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3 Engine Systems and Fuels Introduction diesel programs due to the synergy from light-duty to heavy- duty diesel engines. No further discussion of the light-duty The 21st Century Truck Partnership (21CTP) includes diesel program will be presented here, even though it was specific goals in the areas of engine systems and fuels. This funded in fiscal years (FY) 2000 through 2004 (as shown in chapter contains comments on the goals and the related Table 1-6 in Chapter 1 and in more detail in Appendix C). research programs, including aftertreatment systems, the High Temperature Materials Laboratory of the Oak Ridge National Laboratory (ORNL), and health concerns related Goal of Thermal Efficiency of 50 percent to diesel emissions. Three specific goals were set for engine systems and fuels Introduction (DOE, 2006, p. 2), which can be summarized as follows: The first overarching technology goal of the 21CTP is stated as follows: â¢ Achieve 50 percent thermal efficiency, while meeting 2010 emission standards, by 2010; Develop and demonstrate an emissions compliant engine â¢ Research and develop technologies to achieve 55 per- system for Class 7-8 highway trucks that improves the engine cent thermal efficiency by 2013; and system fuel efficiency by 20 percent (from approximately â¢ By 2010 identify and validate fuel formulations 42 percent thermal efficiency today to 50 percent) by 2010. making possible 5 percent replacement of petroleum (DOE, 2006, p. 14) fuels. This goal was further defined in terms of Major Activity The goals discussed in this chapter are exclusively focused and Milestone 3 as follows: on heavy-duty diesel engines. Prior to the formation of the 21CTP, the responsibilities for heavy-duty and light-duty Demonstrate engine efficiency of 50 percent with 2010 truck technology were merged within the U.S. Department emissions compliance through integration of advanced fuel of Energy (DOE) Office of Heavy Vehicle Technologies injection, new combustion regimes, exhaust-heat recovery, (OHVT). One of the objectives that the OHVT inherited, aftertreatment, advanced controls, low-friction features, air handling, thermal management, and advanced materials. and which was subsequently included in the 21CTP, was the (DOE, 2006, p. 21). development of diesel engine enabling technologies, to sup- port large-scale industry dieselization of Class 1 and 2 light- duty trucks capable of achieving 35 percent fuel efficiency Background and Analysis improvement over comparable gasoline-fueled trucks, while The 21CTP developed an energy audit of a typical Class 8 meeting applicable emission standards (National Research tractor-trailer combination vehicle traveling on a level road at Council, 2000, p. 14). Because this program was a legacy a constant 65 miles per hour (mph) with a gross combination of earlier vehicle research at DOE, none of the objectives weight (GCW) of 80,000 lb, as shown in Figure 3-1. Baseline of the 21CTP were associated with this program, although the accomplishments of this program were frequently cited by DOE officials in presentations to the committee. DOE Personal communication to the committee from Ken Howden, U.S. believed that this program was beneficial for the heavy-duty Department of Energy, Office of FreedomCAR and Vehicle Technologies, August 29, 2007. 26
ENGINE SYSTEMS AND FUELS 27 FIGURE 3-1â Energy audit of a typical Class 8 tractor-trailer combination on a level road at a constant speed of 65 mph and a GVW of 80,000 lb. SOURCE: DOE, 2006, p. 7. Fig 3-1, bitmapped TABLE 3-1â Baseline and 21CTP Target Values from the 3. A 20 percent improvement in engine thermal efficiency Energy Audit Shown in Figure 3-1 from the current baseline of 42 percent will yield the 50 percent thermal efficiency objective. Percentage Â Base Target Reduction Increases in fuel economy, expressed in miles per gal- Total Energy Consumption 380 kW 225 kW 40% lon (mpg), will be directly proportional to improvements Engine Power Required 160 kW 112.8 kW 30% â Thermal Efficiency 42% 50% â in Â thermal efficiency. However, fuel usage in gallons is Auxiliary Loads 15 kW 7.5 kW 50% inversely proportional to miles per gallon. Therefore, a 20 Drivetrain 9 kW 6.3 kW 30% percent improvement in thermal efficiency will result in only Rolling Resistance 51 kW 30.6 kW 40% a 16.7 percent reduction in fuel usage, as shown below. Aerodynamic Losses 85 kW 68 kW 20% Thermal efficiency = â (work output)/(fuel energy input) ~ miles/gal ~ mpg Fuel usage ~ 1/mpg and 21CTP target values from the energy audit shown in Percentage change in fuel usage = Figure 3-1 are also listed in Table 3-1. â (1/mpgimproved â 1/mpgbase) Ã 100 The following observations can be derived from this Percentage change in fuel usage = energy audit: â (1/1.2 â 1/1.0) Ã 100 = â16.7 percent 1. Improvements in engine efficiency offer the largest This result illustrates an inconsistency in a presentation potential reductions in fuel usage. Reductions in roll- to the committee, which erroneously suggested that a 20 ing resistance and aerodynamic losses offer lesser percent improvement in engine thermal efficiency would reductions in fuel usage. yield a 20 percent reduction in fuel usage. 2. The engine power output of 160 kilowatts (kW), which For consistency with DOE, the following terminology is is required by the vehicle at 65 mph, is about 42 per- used in this report: cent of the total fuel energy consumption rate of 380 kW (which equates to 6.8 mpg). Therefore, the thermal â¢ Individual vehicle fuel consumption is expressed as efficiency is 42 percent, which is representative of gallons per mile (gpm). (Note: Alternative units such todayâs typical diesel engine thermal efficiency at the 65 mph road load operating condition. Vinod K. Duggal, Cummins Engine Company, Inc., âDiesel Engine R&D and Integration,â Presentation to the committee, Washington, D.C. February 9, 2007, Slide 11.
28 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP as liters/100 km or gallons/ton-mile may be more TABLE 3-2â 21CTP Funding for the Demonstration of descriptive, but the committee did not use them. 50Â Percent Thermal Efficiency (U.S. dollars) â¢ Individual vehicle fuel economy is expressed as miles Â DOE Participant Total per gallon (mpg). â¢ Total annual vehicle fuel consumption is expressed in Cummins 19,032,087 20,471,307 â 39,503,394 Caterpillar 19,353,158 22,854,337 â 42,207,495 total gallons consumed and is equal to total vehicle Detroit Diesel 16,906,376 17,496,651 â 34,403,027 miles traveled divided by the average mpg. Total 55,291,621 60,822,295 116,113,916 SOURCE: Ken Howden, DOE, FCVT, DOE responses to committee Program Status queries on 21CTP engine systems and fuels, March 28, 2007. The 21CTP selected the engine manufacturers Cummins, Caterpillar, and Detroit Diesel as the industry partners for the demonstration of 50 percent thermal efficiency at 2010 emissions. Although Volvo/Mack was also identified by DOE as another industry partner in the 21st Century Truck Although the details of the technology features are vague Partnership Roadmap, Volvo/Mack does not appear to have in many cases, significantly different approaches were been funded and has not reported any results. Work on the 50 taken in several areas. Cummins used a high-pressure (HP) percent thermal efficiency objective began with the initiation c Â ommon rail fuel, system while Caterpillar and Detroit of the 21CTP in 2000 and continued until 2007, when DOE D Â iesel did not specify the fuel injection system. Another pos- concluded this activity. sible significant difference is that Caterpillar used variable The 21CTP funding for the demonstration of 50 percent intake valve actuators while Cummins and Detroit ÂDiesel did thermal efficiency at 2010 emissions is shown in Table 3-2. not specify this feature. Exhaust Gas Recirculation (EGR) A total of $116 million was spent on the program for demon- systems differed, with Cummins using high pressure loop stration of 50 percent thermal efficiency at 2010 emissions, EGR while Caterpillar used low-pressure (LP) EGR. Detroit with $55 million provided by DOE and $61 million provided Diesel did not specify the EGR system. TurboÂcharging sys- by the industry partners. The industry partners performed all tems also differed. Cummins used variable geometry turbo- of the work in this program. DOE did not provide the com- charging while Caterpillar used a series LP compressor, HP mittee with a breakdown of specifically how the government compressor, HP turbine, and LP turbine. Detroit Diesel did money and the industry money were spent. not specify the turbocharging system. Although it was not clearly stated by the 21CTP, the Each of the industry partners used a waste heat recovery committee assumed that achieving this goal required testing (WHR) system in an effort to approach 50 percent thermal a complete engine system on an engine dynamometer and efficiency. Cummins applied a Rankine cycle WHR system demonstrating that the resulting thermal efficiency and emis- with a turbine-driven generator, which would ultimately drive sions, measured according to standardized test procedures, an electric motor geared to the engine-output shaft. In con- met the specified goals. To assess the status of this goal, the trast, Caterpillar and Detroit Diesel used turboÂcompounding committee summarized the results reported by each industry WHR systems. partner in Table 3-3. The Cummins results, which indicated that 50 percent These results show that none of the industry partners thermal efficiency could be achieved when a Rankine cycle achieved the goal of measuring 50 percent thermal effi- WHR system with a power output of 57 hp was added to the ciency at 2010 emissions from a complete engine system. engine power output of 378 hp, are questionable due to two With respect to the 50 percent thermal efficiency goal, each key technical issues. partner either failed to test a complete engine system on an engine dynamometer and used analysis to project results, or 1. The âRankine cycle WHR System Test Blockâ sche- failed to achieve the 50 percent thermal efficiency goal with matic provided by Cummins shows 60ÂºF cooling water a complete engine system. provided for the Rankine cycle WHR system. This The technologies used in the demonstration engines, unrealistically low temperature cooling water, which which were modified from production baseline engines, are would not be available on Class 7 or 8 trucks, would listed in Table 3-4. These technologies were identified by improve the efficiency of the Rankine cycle WHR the industry partners and are categorized according to the system (Van Wylen, 1961, pp. 282-284). features that were intended to be used for this demonstration An appropriate heat sink for such a Rankine cycle and are listed under Major Activity and Milestone 3 (DOE, system might be air at an 80Â°F temperature. Such a 2006, p. 21). heat sink temperature would require the design of special heat exchange systems and a system to provide Ken the air for cooling. Thus, the change in Rankine cycle Howden, DOE, FCVT, DOE responses to committee queries on 21CTP engine systems and fuels, March 28, 2007. heat sink temperature would be accompanied by addi-
ENGINE SYSTEMS AND FUELS 29 TABLE 3-3â Reported Results of Thermal Efficiency Testing Measured Test Results Cummins Caterpillar Detroit Diesel Engine alone 43.2% at 378 hp Not Specified Not Specified WHR 57 hp at 60Â°F cooling water for Not Specified Not Specified Rankine Cycle System Not tested 47.4% Thermal Efficiency 48.4% Thermal Efficiency (Engine + WHR) (WHR device was not integrated with engine-output shaft) Analytical Projections 50% Brake Thermal Efficiency 50.5% Thermal Efficiency 50.2% Thermal Efficiency (Reported as Peak Efficiency) (Nelson, 2006a) Baseline Engine Engine Model MY2000ISX 450 2007 C15 15L Engine Not Specified Rated Power 450 hp @ 2000 rpm 550 hp @ 1800 rpm (est.) Peak Torque 1650 ft-lb @ 1200 rpm 1850 ft-lb @ 1200 rpm and 1534 ft-lb @ 1237 rpm 1850 ft-lb @ 1100 rpm Thermal Efficiency 42% Not Specified Not Specified Test Speed/Load Condition âTypical Cruiseâa âKey fuel economy pointâa Not Specified Test Conditions SAE J1349 (Net Power) SAE J1995 (Gross Power) EPA Certification Procedures Technology Demonstration Engine System Tested Engine and Rankine cycle WHR Implied to be total engine and Implied to be total engine and System were not mechanically turbocompound system turbocompound system connected Test Speed/Load Condition Peak Torque Peak Torque (1200 rpm, 1,850 ft-lb) Not Specified Test Condition Power 435 hp Not Specified Not Specified Issues with Results Rankine cycle is used to produce electricity. Losses in the conversion of electricity to engine shaft power do not appear to be included Â Rankine cycle used 60Â°F cooling Â Â water. Significantly higher temperatures would be expected in a vehicle, with subsequent deterioration of the Rankine cycle efficiency aGurpreet Singh, DOE, FCVT, âOverview of DOE/FCVT Heavy-Duty Engine R&D,â Presentation to the committee, Washington, D.C., February 8, 2007. tional energy losses required for cooling the system Several features identified in the Major Activity and Mile- condenser. stone 3 were not included in the test engines, as shown in Table 3-5, and were not addressed by the industry partners. 2. A driveline electric motor consuming the electric The most notable features not included were ânew combus- power generated by the Rankine cycle WHR sys- tion regimesâ and âadvanced materials.â This was of signifi- tem and geared to the engine-output shaft would be cant concern because DOE had funded extensive research required to utilize the WHR power in a Class 7 or 8 work in the 21CTP focused on low-temperature combustion truck. Instead of testing a driveline electric motor and within the category of ânew combustion regimesâ and high- gear set to transmit the electric motor power to the temperature materials within the category of âadvanced output shaft of the engine, a load bank (i.e., resistors) materials.â was used to consume the electric power generated. The Other features were not applied consistently by the indus- efficiency of the electric motor and the gear set do not try partners; selected features were used by some partners appear to have been included in the calculation of the and were not used by other partners. These areas included power that the WHR system could add to the engine âadvanced fuel injection,â âadvanced controls,â âlow-Âfriction shaft power. features,â âair handling,â and âthermal management.â ÂSeveral examples illustrate this issue:
30 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP TABLE 3-4â Technologies in Demonstrator Engines for Thermal Efficiency Testing Features Cummins Caterpillar Detroit Diesel Engine MY2000 ISX 450 2007 C15 15L Engine Not Specified Advanced Fuel Injection High-pressure common rail fuel system NA NA replaced the HPI fuel system New Combustion Regimes NA NA NA Exhaust-Heat Recovery Rankine cycle with load bank to simulate a Turbocompound Turbocompound driveline motor consuming electric power Aftertreatment Simulated by increasing back pressure on High efficiency aftertreatment includes dual High-efficiency NOx the exhaust DPF and dual NRT aftertreatment Advanced Controls Engine calibration was tuned with the Variable intake valve actuators NA hardware set to achieve target emission levels Low-Friction Features Optimized lube and water pumps Low-friction components NA Air Handling NA Reduced flow restriction, High-Efficiency NA air systems (series turbocharging) Thermal Management NA Reduced heat rejection NA Advanced Materials NA NA NA Other Features Compression Ratio Increased compression ratio Increased compression ratio Cylinder Pressure NA Increased peak cylinder pressure capability NA Charge Cooling NA High efficiency compact Intercooler and NA Aftercooler EGR High-pressure loop EGR with EGR cooler Low pressure (LP) EGR picked up after DPF; NA includes CGIC (EGR cooler) Turbocharging Variable geometry turbocharging instead of High Efficiency Air System with series LP NA fixed geometry turbocharging compressor, HP turbine and LP turbine Other ExhaustâWHR cooler System optimization (peak cylinder NA pressure, CR, etc.) CACâWHR cooler CoolantâWHR cooler WHR system boost and feed pumps, turbine/ generator Â Test cell coolers to control engine coolant Â Â and IMT to target conditions NOTE: CAC, charge air cooler; CGIC, clean gas induction cooler; DPF, diesel particulate filter; IMT, intake manifold temperature; NRT, NO x reduction trap; WHR, waste heat recovery. 1. Variable valve actuation was used only by Caterpillar. that it had prepared air gap pistons and exhaust port The role of this feature for improving thermal effi- liners, but that they had not been tested. The commit- ciency was not defined. Furthermore, the committee tee did not receive an explanation of why, after nearly was not informed of the extent to which the absence 7Â years with thermal management as a key feature to be of this feature on the engines of the other two indus- included in this project, these items were not included try partners contributed to their failure to achieve the in the Caterpillar test engine. In contrast, the engines of 50Â percent thermal efficiency goal. the other two partners did not include this feature and 2. Only Caterpillar stated that it incorporated reduced heat the committee did not receive an explanation of why rejection in its engine, but the means by which this was this feature was not included in their programs. Like- achieved was not defined and the role of this feature wise, the committee was not informed of the extent to for improving thermal efficiency was not provided. which the absence of this feature contributed to their Caterpillar subsequently reported to the committee failure to achieve the 50Â percent thermal efficiency.
ENGINE SYSTEMS AND FUELS 31 TABLE 3-5 Status of Achieving 2010 Emissions Standards at 50 Percent Thermal Efficiency Â Cummins Caterpillar Detroit Diesel Emissions Standards Test Conditions Assumed to be the â â EPA FTP Heavy Duty Transient same single point Test Cycle, Supplemental used to measure Emission Test (SET) consisting thermal efficiency of the 13 mode ESC (European Stationary Cycle), and NTE (Not to Exceed) Limits. Engine-Out Emission Test Results NMHC (nonmethane hydrocarbon) â â â â CO â â â â NOx 1.39 g/bhp-h 2.5 g/bhp-h â â PM (particulate matter) <0.1 g/bhp-h â â â Exhaust Emission Test Results NMHC â â â 0.14 g/bhp-h CO â â â 15.5 g/bhp-h NOx â â â 0.20 g/bhp-h PM â â 0.006 g/bhp-h 0.01 g/bhp-h Exhaust Emission Analytical Calculations NMHC â â â â CO â â â â NOx 0.209 g/bhp-h 0.17 g/bhp-h 0.2 g/bhp-h â PM <0.01 g/bhp-h <0.01 g/bhp-h â â Assumptions for Analytical Calculations NOx 85% effectiveness 93-97% conversion 95.3% urea SCR â with urea-SCR efficiency efficiency assumed, but aftertreatment demonstrated with higher efficiency has been SCR aftertreatment measured (Nelson, 2006a) PM 90% effective PMI â â â filter Aging Used for Aftertreatment System Above Performance âThe effect of aging âThese are technology â assumptions was accounted for evaluation/demonstration âconsistent with an by only using a projects, and hence, did aged cycle.âa 5% degradation not require the protocol factor for the NOx of durability or aging aftertreatmentâ a required for product development.â a DPF Loading Assumed to have â â â average loading Fuel Economy Penalty Reflected in base The fuel economy âThe fuel economy â engine performance. penalty for the back information is Aftertreatment pressure of 13 kPa competitive information, system was of the aftertreatment and, therefore, not public simulated by system was domain.âa increased back accounted for by pressure on the actually having exhaust. the aftertreatment installed DPF Regeneration â Passive regeneration â â ability of the DPF allows it to be self- regenerating NOTE: â, no information provided to the committee. aGurpreet Singh, DOE, FCVT, âOverview of DOE/FCVT Heavy-Duty Engine R&D,â Presentation to the committee, Washington, D.C., February 8, 2007.
32 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP TABLE 3-6â Improvements Proposed for Reaching 50 Percent Thermal Efficiency Feature Cumminsa Caterpillarb Detroit Dieselb Breathing NA NA Variable breathing Fuel Injection NA Higher injection pressure Heat Insulation NA Add air gap pistons NA Add exhaust port liners Parasitic Losses NA NA Parasitic loss reduction Turbocharger NA Redesign the LP stage turbine to reach the 80% analytical predictions Increased efficiency Add the redesigned HP stage compressor to reach 80% analytically predicted level WHR NA Redesign turbocompound mechanically to eliminate rubbing friction caused by NA undamped shaft dynamics Aftertreatment NA NA Backpressure reduction aCummins analytically projected 50 percent thermal efficiency, but it did not demonstrate 50 percent thermal efficiency with one complete engine system. Improvements are likely to be required by Cummins to resolve issues noted in Table 3-3 in order to achieve 50% thermal efficiency. bImprovements provided by each company. In defining the goals of the 21CTP, DOE indicated that partners, are shown in Table 3-5. âMeeting the 2010 emis- all of these areas would have a significant role in improving sions standardâ implies that: (a) emission levels from the test engine thermal efficiency, yet several of the features received engine and aftertreatment system, when tested on the EPA little or no attention in the attempted demonstration of FTP Heavy Duty Transient Test Cycle, the Supplemental 50Â percent thermal efficiency. Although DOE has provided Emission Test (SET) and the Not To Exceed (NTE) tests, significant funding in several of these areas in the 21CTP in are adequately below the applicable standards to account addition to the funding for the achievement of 50Â percent for the statistical variability of emission results from in-use thermal efficiency at 2010 emissions, the results from this production engines, and (b) the complete test engine and work were not included in the unsuccessful attempts by aftertreatment system has been aged on a durability cycle the three industry partners to achieve the important goal to simulate 435,000 miles for HHDDE as prescribed by the of 50 percent thermal efficiency. Advanced development EPA regulations. The table indicates that an inconsistent within companies usually lags national laboratory research. approach was taken by the three industry partners in dem- However, not including many advanced features in the onstrating 2010 emissions. test engines was of particular concern, because the engine As described earlier, none of the partners achieved the manufacturers were known to have had past experience and goal of 50 percent thermal efficiency at 2010 emissions development activities in most of these areas. standards. Instead, the industry partners presented discus- DOE should review the original features expected to be sions on potential improvements that might be used to reach included in the 50 percent thermal efficiency engine and the stated goals. These potential improvements, as reported determine the justification for omitting some of the features by the industry partners, are summarized in Table 3-6. As from the demonstration engines. DOE should also determine indicated in the table, Caterpillar and Detroit Diesel pro- how the results of their funding of research in several of jected that significant design changes would be required these areas, especially in the categories of ânew combustion to reach the goal of 50 percent thermal efficiency at 2010 regimesâ and âadvanced materialsâ could have been incor- emissions. In contrast, Cummins analytically projected 50 porated in an engine that might have had a greater potential percent thermal efficiency, but it did not demonstrate 50 to achieve 50 percent thermal efficiency. percent thermal efficiency with one complete engine system. None of the industry partners demonstrated compliance Improvements are also likely to be required by Cummins to with the 2010 emissions regulations. Meeting the 2010 resolve the issues noted in Table 3-3. EPA test procedures standard while achieving the 50 percent thermal efficiency are the industry standard and should be used for emissions goal implied that any thermal efficiency penalty incurred by testing, in order to achieve 50 percent thermal efficiency with meeting the 2010 emissions standard would inherently be one complete engine system. included in the thermal efficiency measurement. Compari- sons of the test procedures used to confirm that the demon- KenHowden, DOE, FCVT, DOE responses to committee queries on strator engines met the 2010 emissions standard and the 21CTP engine systems and fuels, March 28, 2007. emission control systems used, as reported by the industry Ken Howden, DOE, FCVT, DOE responses to committee queries on 21CTP engine systems and fuels, March 28, 2007.
ENGINE SYSTEMS AND FUELS 33 Finding 3-1. Although DOE has concluded that the 50 per- the different approaches. Furthermore, the effectiveness of cent thermal efficiency goal has been achieved, the experi- the individual features used on the demonstration engines mental test results show that none of the industry partners could not be determined due to the lack of analysis or system achieved the goal of 50 percent thermal efficiency at 2010 modeling. A validated system model should have been used emissions standards with a complete engine system. Each to compare test data with analytical projections to determine partner either failed to test a complete engine system on an if each feature was performing as expected. engine dynamometer and used analysis to project results or failed to achieve 50 percent thermal efficiency at 2010 emis- Recommendation 3-3. Prior to beginning future test phases sions standards with a complete system. Details of the ana- of this program to achieve 50 percent thermal efficiency, lytical projections were proprietary and were not provided to system modeling should be used so that the preferred tech- the committee. Moreover, the work that was accomplished nical approaches could be selected and test data could be was at the intrinsically more efficient peak torque condition compared with analytical projections to determine if the rather than at an engine speed and load representative of expected results have been obtained. 65Â mph road load. Finding 3-4. Although DOE stated that the 2010 emissions Recommendation 3-1. Objective and consistent criteria standard was achieved in the demonstrator engines attempt- should be used to assess the success or failure of achieving ing to achieve 50 percent thermal efficiency, only steady- a key goal of the 21CTP such as the attainment of 50 percent state emissions at one test condition were reported rather thermal efficiency. Detailed periodic technical reviews of than test results from the EPA specified test procedures for progress against the program plan should be conducted so the 2010 emissions standard. In some cases, the emissions that deficiencies can be identified early and corrective actions were estimated from engine-out emissions and assumed implemented to ensure success in accomplishing program aftertreatment efficiency. goals. DOE should continue to work toward demonstrating 50 percent thermal efficiency at the peak efficiency condi- Recommendation 3-4. Achieving compliance with 2010 tion as well as representative 65-mph road load engine speed emissions with a âone-offâ prototype engine designed to and torque condition. DOE should also consider reducing demonstrate 50 percent thermal efficiency may be too strin- the number of industry contracts on specific engine projects gent a goal for the 21CTP. The emission objective levels that are funded so that only the engine systems most likely should be revised to be the demonstration of emissions at a to meet the goal, based on system modeling and analytical single point, where the emission level selected to be dem- projections, will be developed and tested experimentally. onstrated should have the potential for meeting the 2010 emissions as specified by EPA test procedures. Finding 3-2. The goal of achieving 50 percent thermal efficiency at 2010 emissions was not clearly specified Finding 3-5. Although industrial partners reported on their by the 21CTP. Each of the three industry partners used a progress, the presentations were high level summaries with different test procedure for measuring thermal efficiency critical engineering information omitted, thereby making the (see Table 3-4). Likewise, none of the industry partners assessment of accomplishments relative to goals difficult. demonstrated 2010 emissions using the required EPA test procedures with aged engine and aftertreatment systems. A Recommendation 3-5. DOE should work to develop a goal of this importance should be specified by standard test review process that will allow future review committees to procedures so that the results are verifiable and compatible evaluate âsensitiveâ information so quantitative assessments with industry standards. of progress can be made. Recommendation 3-2. Future work to achieve the goal of Engine System Life and Durability 50 percent thermal efficiency at 2010 emissions should be specified by industry standard test procedures. SAE J1349 Tests with single, one-off demonstration engines fail to Engine Power Test Code is the industry standard for net demonstrate the system life required for introduction into the power ratings and should be specified for the thermal effi- heavy-duty truck marketplace. The demonstration of system ciency portion of this goal (SAE, 2004). Test results should durability for a 400,000- to 1,000,000-mile system life target clearly provide all of the engineering details required to represents a serious âreal worldâ hurdle for the introduction interpret the results. of such hardware. DOE and the industry partners will need to address the Finding 3-3. Some of the technical features used to approach system life target of heavy-duty diesel engines as they are the goal of 50 percent thermal efficiency, as shown in developing experimental, one-off demonstration engines Table 3-4, differed among the three industry partners, and with improved thermal efficiency. At a minimum, a roadmap no explanation or technical analysis was provided to justify of required technical actions to achieve system life targets
34 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP after demonstrating thermal efficiency objectives in a one- future emissions standards. The impacts on fuel economy off, demonstration engine should be provided. associated with the addition of these emission control sys- tems are difficult to quantify for specific engines from the data that were presented to the committee. The industry A Novel Potential Energy Recovery Concept partners indicated that the details of these emission control In reviewing the Cummins WHR concept of the Rankine systems are proprietary and have chosen not to specify their cycle using a turbine generator to provide electric power configurations or their performance explicitly. to supplement the main engine shaft power, the committee Several of the slides presented indicate the general trends found that an interesting, and potentially relevant, extension of the adverse impact on fuel economy that can occur due of this concept was contained in a Cummins presentation on to the additional emission control systems without further exhaust energy recovery at the 2006 Diesel Engine Emis- improvements in the thermal efficiency of the engine. Engine sion Reduction (DEER) Conference (Nelson, 2006b). This efficiency improvements, which had been occurring at the presentation suggested the following features for a potential level of one half a percent per year, decreased significantly energy recovery concept: as the model year 2002 was approached. Figure 3-2, which is reproduced from Duggal, shows trends for the impact â¢ An on-vehicle high-voltage bus, departing from the typi- of emission standards for model year 2002 and beyond on cal 12 VDC systems engine efficiency. A 3 percent decline in absolute engine â¢ Incorporating technology common with Hybrid Electric efficiency is associated with the introduction of cooled Vehicles (HEV), including battery storage and power EGR to meet the 2002 emissions standard. An additional conditioning. 1.5 percent degradation in engine efficiency is forecasted â¢ Opportunities for high voltage accessories, including: to occur with increased EGR to meet the 2007 emissions âDriveline motor/generator âCoolant pump(s) standard. Improvements in the engine configuration were âPower steering portrayed as having the capability to recover this absolute âElectric fans 41/2 percent engine efficiency decrease at the 2007 emissions âAir compressor, and standard. Figure 3-2 also predicts a 2 percent absolute engine âHeating, ventilation, and air conditioning (HVAC) efficiency degradation because EGR levels will again be increased to meet the 2010 emissions standard. This brief presentation suggested that a significant revi- Because of the lack of detailed information, it is not pos- sion of the entire propulsion system and its accessories sible to determine the precise fuel economy degradation that could potentially yield fuel savings from the following had been encountered by the engine manufacturers as they techniques: changed their configurations to meet the emission standards. DOE should ask the manufacturers to supply this informa- â¢ Using the HEV concept could allow the main diesel tion to assist in determining the size and cause of these fuel engine to be downsized and peak power demands could economy degradations associated with the successive changes be supplied by the electric motor and battery storage in required emission standards (such as increases in back pres- system sure before regeneration and quantity of fuel used to regener- â¢ Extensive use of high voltage, electrically driven ate the diesel particulate filter [DPF]). Such information would accessories on an on-demand basis allow the DOE to evaluate the potential beneficial impact of â¢ Elimination of a separate engine-driven alternator the technologies being developed by the 21CTP program. An additional concern is associated with the cost and This significant revision of the entire propulsion system energy content/requirements (because urea is made from and its accessories should be studied for its potential in pro- natural gas) of reagents for reducing NOx levels with Selec- viding fuel savings as a means for meeting the goal of the tive Catalytic Reduction (SCR) NOx removal systems. It is 21CTP. The study should include analysis of the cost-benefit not clear how the cost or energy content/requirements of of each of the opportunities listed above. These opportuni- such reagents is being related to the efficiency targets for the ties are discussed further in Chapter 4, under the heading 21CTP. Because the reagent use is directly proportional to âHybridization of Long-Haul Trucks.â the pre-SCR NOx levels in the exhaust, one must know these details to outline reagent use and cost. Discussion with regard to SCR reagent usage was absent from the presentations and Fuel Economy Losses Related to Oxides of Nitrogen (NOx) and Particulate Control Vinod K. Duggal, Cummins Engine Company, Inc., âDiesel Engine One of the key challenges with regard to maintaining and R&D and Integration,â Presentation to the committee, Washington, D.C., improving fuel economy for heavy-duty truck engines is to February 9, 2007, Slide 8. Vinod K. Duggal, Cummins Engine Company, Inc., âDiesel Engine minimize the fuel economy losses associated with adding R&D and Integration,â Presentation to the committee, Washington, D.C., NOx and particulate control systems to these engines to meet February 9, 2007, Slide 16.
ENGINE SYSTEMS AND FUELS 35 FIGURE 3-2â Heavy truck engine technology roadmap showing the effects of emission regulations on thermal efficiency. SOURCE: Vinod K. Duggal, Cummins Engine Company, Inc.,âDiesel Engine R&D and Integration,â Presentation to the committee, Washington, D.C., Feb- ruary 9, 2007, Slide 16. Figure 3-2, bitmapped, type changes not possible only the NOx removal effectiveness was discussed in infor- specific engine speed and load conditions for this demon- mation presented for the SCR systems. If DOE determines stration were not specified, each of the industry partners that reagent costs or energy is significant, it should specify a reported that their best thermal efficiency was measured at, procedure to include these effects in thermal efficiency and or near, the peak torque condition of the engine, as indicated vehicle fuel economy goals and economic assessments. in Table 3-3. The data presented for the 50 percent thermal efficiency The peak torque condition where the best thermal goal by the industry partners projected the performance of e Â fficiency was demonstrated is not consistent with the such emission control systems for the configurations used t Âypical 65 mph road load engine operating condition that in the specific engine tests. In some cases, the operating was specified as the focus of Class 8 trucks for the 21CTP. condition chosen for the test caused exhaust temperatures This discrepancy in operating conditions is illustrated in the to be sufficiently high to continuously regenerate the DPFs. energy audit of a typical Class 8 tractor-trailer combination Thus, no fuel economy degradation was associated with on a level road at a constant speed of 65 mph and a GVW of the level of fuel economy demonstrated. This circumstance 80,000 lb as shown previously in Figure 3-1. appears to be an optimistic assumption with regard to overall To meet the goals of the 21CTP goal, this audit shows usage of a heavy-duty truck. It appears reasonable that DPFs that the 50-percent thermal efficiency goal is required at the would require periodic regeneration, especially in city use or road load power at 65 mph rather than at the peak torque operating without a loaded trailer, and thus the potential for condition. The road load power required at 65 mph is degradation in overall engine efficiency. 214 hp (160 kW), as shown in Table 3-7. At the peak torque A January 31, 2007, Associated Press article (Robertson, condition for these engines, approximately the same power is 2007) quoting Freightliner executives highlighted additional generated as at the rated power condition, which is attributed costs associated with meeting new emissions standards. In to the significant torque rise of these engines. that article, Freightliner Corporation stated that some fuel The decrease in thermal efficiency at the 65 mph road economy penalties were associated with meeting the 2007 load power condition versus the peak torque condition can emissions standards. These fuel economy degradations were be significant. This reduction is illustrated on a typical fuel not quantified in their corporate statement. consumption map for a production DDC Series 60 12.7L engine shown in Figure 3-3 (from Merrion, 1994). The 65 mph road load operating condition (speed and power) Thermal Efficiency Goal at Full Load Versus Road Load for typical drivetrain parameters for a fuel-efficient Class 8 The 21CTP goal for the three industry partners was to truck is shown on this fuel consumption map. As indicated demonstrate 50 percent thermal efficiency. Although the in the figure, a 2.5 percent decrease (1.1 percentage point
36 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP TABLE 3-7â Comparison of Engine Rated Power and data from the 21CTP as well as published data indicate that RoadÂ Load Power up to a 7 percent decrease (3.4 percentage point decrease) in thermal efficiency can be expected at the 65 mph road load Road Load Road Load Power as Engine Rated Power Power Percent of Rated Power condition versus the peak thermal efficiency condition. A convenient method for defining the road load condition Cummins ISX 450 hp 214 hp 48% would be to use one of the operating conditions from the SET Caterpillar C15 550 hp 214 hp 39% Detroit Diesel NA NA NA (Supplemental Emission Test) which is the 13-mode steady- state emission test established to help ensure that heavy-duty NOTE: NA, Not available to the committee. engine emissions are controlled during steady-state type driving, such as a line-haul truck operating on a freeway. This test is based on the European Unionâs 13-mode ESC (European Stationary Cycle) schedule, commonly referred to as the âEuro III cycle.â This cycle is shown schematically in Figure 3-4. Peak Because road load power required at 65 mph is approxi- Torque mately half of the rated power, and rated torque of the engine, 13-mode test point A50 (60 percent engine speed, 50 percent load) would appear to be an appropriate choice to approxi- mate the 65 mph road load condition, although this would need to be confirmed for each engine under consideration. The 60 percent of rated engine speed for test point A50 is similar to the speed for the peak torque condition that had been used for the demonstration of peak thermal efficiency by the industry partners. Finding 3-6. Achieving the 21CTPâs goal of 50 percent 65 mph peak thermal efficiency is not expected to result in the Road Load Partnershipâs goal of 50 percent thermal efficiency for a typical Class 8 tractor-trailer combination on a level road at a constant speed of 65 mph and a GVW of 80,000 lb. Even if 50-percent thermal efficiency were to be achieved at, or near, the peak torque condition, up to a 7 percent improve- ment (3.4 percentage point improvement) task would still remain to achieve 50 percent thermal efficiency at the 65 mph road-load condition. FIGURE 3-3â DDC Series 60 12.7L brake-specific fuel consump- tion map. SOURCE: Based on Â Merrion, 1994, modified by the Fig 3-3, bitmapped mostly Recommendation 3-6. The 21CTP should clearly define, in committee. Reprinted with permission from SAE paper 940130. addition to the peak thermal efficiency condition, the specific Copyright 1994 by SAE International. 65-mph road-load condition for demonstrating 50 percent thermal efficiency. The committee suggests using one of the 13-mode steady-state emission test points for approximat- ing the 65-mph road load condition. For typical engines, decrease) in thermal efficiency occurs from the peak thermal drivetrains, and vehicles, emission test point A50 (60 per- efficiency condition to the road load condition, as shown in cent engine speed, 50 percent load) would be appropriate, Table 3-8. although the most appropriate point (or multiple points, if The 21CTP stated that âdifference in peak thermal necessary) should be determined for the specific engine, efficiency and road-load thermal efficiency is common, powertrain, and vehicle configuration under consideration. [but] it is not a universal rule.â However, subsequent data The 21CTP should request each of the three current industry provided by several of the industry partners, also shown in partners to test their experimental demonstration engines Table 3-8, indicated that the decrease in thermal efficiency according to this recommendation. at the 65 mph road load engine operating condition versus the peak thermal efficiency can be significant. The available A recent CRC study has proposed new cycles under devel- opment that may correlate better with actual in-use emis- DOE, sions and, possibly fuel usage, for heavy-duty diesel trucks FCVT, 21CTP, response to committee query, transmitted via e-mail by Ken Howden, March 27, 2007. (Tennant, 2007). This study found that their in-use operation
ENGINE SYSTEMS AND FUELS 37 TABLE 3-8â Change in Thermal Efficiency (BSFC) from Peak Thermal Efficiency to 65 mph Road Load Condition Change in Thermal Efficiency Source Condition BSFC Thermal Efficiencya RoadÂ Load vs. Peak DDC Series 60 Peak Thermal Efficiency 0.312 lb/bhp-h 43.9% Peak 12.7L BSFC Map â 400 hp â 1,500 rpm â (71% maximum engine speed) Road Load (65mph) 0.320 lb/bhp-h 42.8% â2.5% â 214 hp â 1,500 rpm Cummins ISX Peak Thermal Efficiency NAc 50% Peak 50% Thermal Efficiency â A100 point: 1,168 rpm, 1,650 ft-lb, 367 hp Analytical Projection Test Engine Road Load (65 mph) NA Inadequate Data Inadequate Data â B63 point: 1,456 rpm, 1020 ft-lb, 283 hp Provided Provided Caterpillar Peak Thermal Efficiency NA 47.4% Peak 50% Thermal Efficiency â 1,200 rpm, 1,850 ft-lb, 420 hp Test Engine â (peak torque) (Gear Fast, Run Slow Strategy) Road Load (65 mph) NA Avg = 45.7% â3.6% â Approximately 250 hp â Average of A50 and B50 pointsb â A50 point: 1,200 rpm, 925 ft-lb, 210 hp A50 pt = 46.6% â B50 point: 1,500 rpm, 925 ft-lb, 265 hp B50 pt = 44.8% Detroit Diesel Peak Thermal Efficiency N/A 48.4% Peak 50% Thermal Efficiency â A100 point: 1,237 rpm, 1,548 ft-lb, 364 hp Test Engine Road Load (65 mph) NA About 45% â7.0% â Average of B50 and B75 points â A50 point: 1,506 rpm, 782 ft-lb, 224 hp â B75 point: 1,506 rpm, 1,172 ft-lb, 336 hp aThermal efficiency % = (1/BSFC) Ã 13.7. bPointsrefer to 13 mode emission test points. cNA, not available to the committee. could be partitioned into the following four modes (with associated maximum speeds noted): creep (9 mph), transient (48 mph), cruise (59 mph), and high-speed cruise (65 mph). Each mode was highly transient, and only the high-speed cruise mode reached 65 mph. The 21CTP should monitor this work and consider the possible future application of these cycles for assessing thermal efficiency improvements for HHDDEs. Commercial Viability The ultimate purpose of DOEâs 21CTP is to develop technology that will ultimately be used in widespread com- mercial applications so that the demonstrated fuel savings in the laboratory can be achieved across all Class 7 and 8 trucks. For this to occur in the free marketplace, the ultimate cost of the technology used to achieve the fuel savings must be recovered by the savings in fuel costs within a period of sev- eral years. The status of the system costs required to achieve 50 percent thermal efficiency, as reported by the industry partners, is summarized in Table 3-9. As indicated by the lack FIGURE 3-4â Thirteen-mode steady-state emission test conditions. SOURCE: DieselNet Online information service on clean diesel of cost information in the table, the issues of system costs engines and diesel emissions. Available at www.dieselnet.com/stan- and commercial viability do not appear to have been suitably dards/cycles/esc.html. Accessed August 6, 2007. addressed by DOE and the industry partners. Fig 3-4, bitmapped
38 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP TABLE 3-9â Commercial Viability Â Cummins Caterpillar Detroit Diesel Hardware Status Lab-based technology demonstration NA Technology demonstration projects One-off, prototype devices Vehicle Packability of Engine Lab demonstration not constrained by on- System package able to be installed System vehicle packaging limits in Class 8 truck Hardware Costs NA NA Costs of laboratory or prototype hardware do not reflect on their costs when available in commercial use. Commercial Potential NA Several of the technology building NA blocks are being considered for inclusion on the 2010 Heavy Duty on highway engine offering from Caterpillar. Production viability and the ability to package the system were vital in the Caterpillar demonstration. Cost of Key Elements to be These details are proprietary. However, NA NA Considered Commercially Viable a cost-payback analysis considering fuel from an Economic Perspective cost versus the performance and price of the waste heat recovery (WHR) system components would determine its viability from an economic perspective. Any analysis should also include the potential benefit of WHR to reduce overall vehicle cooling system loadings. Work Planned to Achieve Ongoing WHR project seeks to demonstrate NA Some work is planned. However, Costs Required to Make the this concept in-vehicle which may also DOE role in these efforts has not Key Features of the Engine demonstrate its commercial viability. yet been determined. Commercially Viable NOTE: NA, no information provided to the committee. Cummins addressed this issue at the August 2006 DEER are incurred. None of the analyses of fuel savings required Conference in a presentation titled âAchieving High Effi- to pay back initial costs highlighted the development costs ciency at 2010 Emissionsâ (Nelson, 2006a). This presen- for demonstrating the high mileage life of these modified tation showed that a 10 percent fuel savings for a truck engines and energy recovery systems. The work to guarantee operating for 120,000 miles per year and with $3.00/gal fuel a system life comparable to those of current engines will would provide a savings of $9,000 over an 18-month period represent very significant investment of time and cost for (assuming 6.0 mpg). Cummins stated that $9,000 would the introduction of modified engines and energy recovery be the target cost for 10 percent fuel savings. Because the systems into production. 21CTP goal is to reduce fuel consumption by 17 percent, the Cummins estimates would indicate that, at $3.00/gal fuel Finding 3-7. DOE and the industry partners did not appear cost, approximately $15,000 might be a suitable cost target to address the potential commercial viability of the technolo- for the improvements added to the base engine. gies or the potential costs required to achieve cost-effective An additional cost related to major modifications to the solutions, as illustrated in Table 3-10. base engine and the addition of an energy recovery system is associated with the required durability of heavy-duty Âdiesel Recommendation 3-7. DOE should request the industry engines. Engine lifetimes for heavy-duty diesel engines partners to make an assessment of cost objectives required are typically 400,000 to 1,000,000 miles. To achieve this to achieve commercial viability. level of durability, significant development cost and time
ENGINE SYSTEMS AND FUELS 39 Goal of Thermal Efficiency of 55 percent of efficiency, emissions, and fuels. It is well known that the interactions among these elements are fundamental and com- Introduction plex. For example, a new aftertreatment component such as a NOx trap or SCR catalyst cannot be effectively considered in The 55 percent goal has been proposed by DOE in the a systematic manner without knowledge of the âengine-outâ 21CTP Roadmap document (DOE, 2006, p. 2) to follow emissions, particularly from the new combustion regimes the goal of demonstrating the 50 percent efficiency goal. It that are being investigated. should be noted that the work toward the 55 percent goal, if It does not appear that any formalized systems engineer- it has started at all, is very much in its beginning. ing analysis was done to determine (1) the relative impor- In assessing the research programs in support of this goal, tance of these barriers, (2) the interactions among them, and the committee identified two general issues of concern: (3) the overall effect of each on the entire system. This would be required to determine realistic improvements that would 1. The appropriateness of the recent shift of focus toward be needed for each of the barriers identified to achieve the component development to achieve a prototype emis- 55 percent thermal efficiency goal. To do so quantitatively sions-compliant engine system thermal efficiency of would require a well-developed total system simulation, 55 percent by 2013; and which the authors of the Roadmap state is immature or not 2. Effectiveness of the number of engine companies to be available. However, a top-down qualitative approach, start- funded, i.e., one or two versus five. ing with the overall system goals, subgoals, and technical requirements to achieve them would provide at least some Appropriateness of Shifting Focus Toward Component understandable framework for allocating the reduced amount Development to Achieve an Engine System Thermal of funding that is available. Inspection of the Quad Sheet Efficiency of 55 Percent by 2013 submissions of 2007 (DOE, 2007) appears to show a col- lection of projects, albeit in important areas, but absent any The pertinent strategy as stated the 21CTP Roadmap estimate of what success in any of the projects would mean document (DOE, 2006, p. 10) is as follows: to the achievement of the system goal. This type of funding and organization is more appropriate to basic research than Research and develop technologies which will achieve a stretch thermal efficiency goal of 55 percent in prototype it is to applied research with a specific system goal. engine systems by 2013, leading to a corresponding 10 per- However, a planned major enabler of the attainment of cent gain in over-the-road fuel economy over the 2010 goal. the 55 percent thermal efficiency goal appears to be low- (2010 goal was 50 percent thermal efficiency.) temperature combustion (LTC), in its various forms. LTC is heavily supported by the FreedomCAR and Vehicle Tech- This goal has to be taken in the context that the DOE nologies light duty program with expected âspill-overâ ben- budget for Engine Systems work starting in FY 2008 could efits in the heavy-duty engine sector. Therefore, in reviewing be severely reduced (see Table 1-6 and Appendix C for the the appropriateness of the shift to component research, it is details of the appropriations to the 21CTP and the parent important to assess LTC as a âcomponentâ technology for programâs research budgets). The extent of this reduction the attainment of 55 percent thermal efficiency in heavy-duty is illustrated by the budget for Heavy Truck Engines of truck engines. This discussion follows. $14.49 million in FY 2007 dropping to a requested budget of $3.519 million for FY 2008, i.e., a 76 percent reduction. Issues Related to Low-Temperature Combustion Lesser reductions are present in supporting areas such as Combustion and Emissions, and Waste Heat Recovery. Only The committee is concerned about the research program Propulsion Materials Technology for Heavy Vehicles shows to develop LTC, i.e., homogeneous charge compression- a modest budget increase of roughly 25 percent. ignition (HCCI) or premixed charge compression-ignition As noted earlier in this chapter, the 2010 efficiency goal (PCCI). In particular, recognizing the present status and of 50 percent was not demonstrated by any of the program future outlook for this technology, the committee believes it participants, even with the relatively large funding base that to be unlikely that it will enable heavy-duty diesel engines was available from the initiation of the 21CTP until 2007 to achieve the thermal efficiency goal and emission standard when DOE concluded this activity. Therefore, it is obvious with a more effective emission control system having little that the funds to be allocated for FY 2008 and onward will or no aftertreatment. have to be used in a very prudent manner, which may mean Traditional spark-ignited (SI) and diesel engines both fewer projects of greater scope and potential, in order to have rely on a source of positive ignition. In SI engines, this is any chance of achieving meaningful technical progress. accomplished by means of a high-voltage discharge across On pages 16 and 17 of the 21CTP Roadmap (DOE, 2006), the electrodes of a spark plug that is immersed in a fuel and what appears to be a âlaundry listâ of technical barriers to air mixture within the engine cylinder that is capable of achieving this goal is presented under the separate categories supporting flame kernel development and subsequent flame
40 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP propagation. The timing of the spark event is a control vari- cylinder in the case of PCCI. In either case, the mixture is able, which can be set optimally for fuel efficiency or delayed so dilute that combustion has to occur through the natural (retarded) to control in-cylinder phenomena such as NOx for- chemical kinetic mechanisms between the fuel and the sur- mation or to eliminate the occurrence of engine knock. The rounding air and residual gases (i.e., burned gases containing rate at which the flame propagates is highly correlated to the nitrogen, oxygen, carbon dioxide [CO2] and water [H2O] turbulence level in the cylinder and the cylinder geometry. as major species) as the mixture is compressed to higher In diesel engines, positive ignition is obtained by injecting temperatures during the compression stroke of the engine. fuel of sufficient cetane rating into air, which has already been This reliance on gas-phase chemical kinetics results in major compressed to high temperature and pressure within the cyl- control and operational issues because the kinetic rates do inder of a high compression ratio engine before the injection not scale with engine speed (measured in revolutions per event. After a short delay associated with droplet atomiza- minute [rpm]), are variable at different loads, are dependent tion, vaporization and early-stage chemical reactions, a flame on engine thermal condition and are a function of the diesel process is initiated that spreads to the remainder of the fuel fuel composition, which can vary across a significant range that has already been injected or is continuing to be injected and still be acceptable for traditional diesel combustion. in jet-like fashion through the nozzle(s) of the high-pressure Many papers and articles have been written about LTC diesel fuel injection system. The rate of combustion is tied and homogeneous charge compression-ignition (HCCI) to the injection rate, the fluid motion in the cylinder, and the engines (see, for example, SAE, 2007), but most describe rate at which the individual droplets vaporize and burn. The single-cylinder steady-state engine operation and initial timing of the injection event is a control variable that has an attempts at modest transient operating states. As such, many effect on the thermal efficiency of the cycle and the formation of the conclusions about the potential of such combustion of pollutants such as NOx and particulate matter. approaches are still quite speculative and not based on solid Diesel combustion, in many ways, is more complex than documented technical results. SI engine combustion. (Flynn et al., 1999). Even though the HCCI, PCCI, or LTC cannot be used in engine starting air-fuel mixture is lean overall (excess air with respect to and cold-engine light load operation due to the very low tem- the stoichiometric requirement for complete combustion), perature and the correspondingly low rates of the controlling the combustion process is not homogeneous. Some of the kinetic reactions. The processes require a warmed-up engine energy release process takes place in a very rich condition and the attainment of appropriate operating temperatures as the fuel enters the injectorâs spray plume. This region is within the engine system. This primary issue must be over- where particulate precursors are formed and particulates come in any practical implementation of an LTC concept. are created which must be subsequently burned before the LTC processes depend on the ignition quality of the fuel combustion process is completed. In addition to the very used in their operation. Fuels with high cetane numbers rich process taking place in the fuel air mixture that enters such as those typically used for diesel fuels have significant the spray plume, there is a very high temperature in the low temperature reactivity and thus ignite easily at modest nearly stoichiometric diffusion flame that forms around overall engine compression ratios. These low compression the spray jet periphery. This high-temperature diffusion ratios limit the maximum thermal efficiency obtainable from flame is the source of the nitrogen fixation process within such cycles. Fuels with lower cetane, or higher octane rat- the diesel combustion chamber. Despite the major advances ings, have a smaller amount of low temperature reactivity in high-pressure diesel fuel injection technology, which has and thus require higher compression ratios to obtain igni- reduced both emissions and noise through pulse injection tion. DOEâs present fuels research activity is investigating and droplet size reduction, the process is still inherently the optimization of fuel composition for such approaches nonhomogeneous. Consequently both NOx and particulates to obtain combustion at appropriate compression ratios and from the engine are well in excess of tailpipe standards and engine operating temperatures. Again, most of this effort is significant, and complex afterÂtreatment is required to lower undertaken on single-cylinder engine tests, and not transient them to acceptable levels. multicylinder engine operation. Thus, the data obtained to The basic concept of LTC, in its various forms, is to carry date are far removed from those required to demonstrate out the combustion process in an ultra-lean or dilute mixture, the true viability of such approaches for real multicylinder the temperature of which is low enough to forestall the fixa- heavy-duty engines. Furthermore, it is likely that no single tion of nitrogen and oxygen, i.e., reduce NOx formation to fuel composition optimizes efficiency under all conditions levels capable of meeting 2010 emission levels without after- of speed and load. As discussed below in the section âGoals treatment, and whose lean composition avoids the formation Involving Fuels,â the committee does not recommend assum- of particulate matter. The fundamental technical issue or ing that specialized fuels will be commercially available for barrier to LTC combustion in diesels (and SI) engines is that advanced combustion engines. there is no longer a source of positive ignition, which is easily Experience has shown that the overall thermodynamic controlled. The fuel is injected very early in the case of HCCI efficiency of optimized HCCI or PCCI combustion processes to achieve homogeneity or is premixed before entry into the can be similar to those of normal optimized diesel engines
ENGINE SYSTEMS AND FUELS 41 (Kuzuyama et al., 2007). This is true even though the best kinetic ignition process, and therefore the resulting combus- of such cycles would have significant unburned hydrocarbon tion placement, is dependent on the integrated thermal state (HC) and carbon monoxide (CO) emissions due to the rela- within the engine, special adaptations are required to man- tively low temperatures and the tendency for the reactions age combustion processes during transient operation where to terminate quickly before the entire combustion process is the engine thermal and heat transfer conditions can change complete, especially during the expansion stroke when the drastically and rapidly. To date only modest rates of engine- temperature is decreasing rapidly. Analysis usually indicates output increase or decrease have been demonstrated with that the incomplete hydrocarbon combustion in the best of actual engine tests. The severity of required engine operation such cycles yields combustion efficiencies of about 95 per- transients is well demonstrated by the transients required cent compared to the normal diesel combustion efficiency during the transient emissions certification process for of 99-plus percent. This lower combustion efficiency is heavy-duty engines, i.e., the FTP. This test was statistically counteracted by the lack of radiant emissions and heat loss derived from analysis of actual engine operation in in-city from particulates that occurs in the traditional diesel com- environments. Thus, the transients represented in the cycle bustion process. These radiant heat losses typically amount depict the required level of transient operations necessary to 5 percent of the fuel energy and they occur near top dead for in-city operation of a heavy-duty truck. Because the rates center of the cycle and thus represent nearly a 5 percent loss of transient load excursion on the cycle are almost an order in engine efficiency (Flynn et al., 1999). The combination of of magnitude greater than any transient load excursion rates poor combustion efficiency and lower heat losses can yield demonstrated for LTC in the open literature, the development similar indicated engine efficiencies for conventional diesel of such transient capability remains a significant roadblock to and LTC combustion processes. Combustion efficiency the application of such combustion processes to real engines losses accompany even the most efficient LTC (HCCI or (SAE, 2007). PCCI) operating points, even those with most of the energy These LTC processes, as intended, do produce engine release occurring rapidly near top dead center. exhaust with virtually no particulates or NOx emissions. These rapid energy releases are also accompanied by Thus, engines that could use such processes over their com- significant noise emissions similar to those occurring during plete operating range could have exhaust emission control knock in an SI gasoline engine. A great deal of effort has been systems that are much simpler than those being presently placed on slowing these rapid heat release rates to control proposed for heavy-duty applications, i.e., regenerative par- noise and rapid rates of pressure-rise within the cylinder. ticulate filters and either regenerative NOx traps, lean NOx A wide variety of approaches have been used to slow these catalyst or SCR. No researcher has demonstrated that LTC combustion processes. Approaches such as the introduction processes could be used to cover the entire engine operating of diluents to the combustion chamber and the stratification map from engine startup through high load and transient of fuel/air ratios within the combustion chamber have been operation. The current operating range for LTC, as shown in successfully used to lengthen heat release durations and Figure 3-5, is confined to low loads, while diffusion com- reduce combustion noise. These processes, though, also lead bustion dominates at high loads. Thus, it remains unclear to delaying combustion into the later part of the expansion as to the actual emission control benefits of applying such cycle, thus increasing the portion of unburned HC and CO combustion processes. Some authors, such as Duffy (2004), that remain in the engineâs exhaust and a corresponding loss proclaim success at operation from light load to very high in thermal efficiency. The level of HC and CO emissions in load with low temperature combustion processes, but exami- the exhaust of such HCCI and PCCI combustion processes nation of their test results indicate that these experiments far exceeds the allowed level of tailpipe HC and CO. With really use combinations of multiple combustion modes. The combustion efficiency in the range of 95 percent versus resulting exhaust gas constituents include unburned HC and 99 percent for conventional diesel engines, LTC engines will CO, (normal LTC emissions) plus particulates and NOx emis- experience a four- to fivefold increase in unburned HC and/or sions in excess of upcoming standards that would require CO emissions. Thus, catalytic oxidation of these combustion exhaust aftertreatment devices for each of these pollutants products will be required if HCCI or PCCI combustion pro- complicating the exhaust aftertreatment system greatly. cesses are used in operating modes of a production engine As indicated above, most of the research presented in the configuration. These emissions occur at conditions of low open literature to date is from single-cylinder and simple exhaust temperature and thus will require catalysts of very multi-cylinder engine experiments. These experiments pres- high efficiency and systems to promote oxidation at operat- ently have shown no way of dealing with the range of load ing points with very low exhaust temperature. It is unknown variation that is required for heavy-duty engine operation or whether sustained operation at these types of conditions the transient characteristics necessary for real vehicle opera- would require the addition of fuel or some other means to tion. It presently appears that there is little potential for the heat the oxidation catalysts. application of such low temperature combustion processes Transient engine operation is also a problem with HCCI over the range of engine operation in heavy-duty engines. and PCCI combustion processes. Because the chemical
42 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP FIGURE 3-5â Illustration of the operating range for LTC combustion. SOURCE: Vinod K. Duggal, Cummins Engine Company, Inc., âDiesel Engine R&D and Integration,â Presentation to the committee, Washington, D.C., February 9, 2007, Slide 14. Fig 3-5, bitmapped Further, if LTC is ultimately able to operate successfully Recommendation 3-8. DOE should complete the demon- at the maximum engine load, the lean or dilute nature of stration of the 50 percent thermal efficiency goal before this combustion process (to achieve NOx levels capable of embarking on the 55 percent goal. With respect to Âongoing meeting 2010 emission levels without aftertreatment) will work on low-temperature combustion, DOE should objec- require significant increases in engine maximum cylinder tively analyze the potential viability of this combustion pressures or engine displacement to achieve output similar concept for heavy-duty engine applications, recognizing the to those of engines currently used in on highway trucks. If many issues that would need to be resolved to achieve com- these changes in engine cylinder pressure requirements or mercial viability. displacement are introduced into the market, these product introductions would require major changes in engine design Finding 3-9. Information on the effects of fuel formulations and require a research and development cycle of over five on LTC operation was not presented to the committee by the years to demonstrate appropriate engine life targets. Higher 21CTP. However, the committeeâs opinion is that any single cylinder pressures may also introduce significantly higher diesel fuel formulation is unlikely to optimize LTC over all friction losses, which should be considered. Early discus- modes of operation. The optimum fuel for light-load opera- sions by DOE with potential contractors and/or suppliers tion will likely have different properties than the optimum for such efforts to obtain their perspective on how such fuel for heavy-load operation. product change would be implemented, the time require- ments for such product introductions and their overall effect Recommendation 3-9. DOE should try to specifically on efficiency and emission controls are considered by the confirm whether or not a single non-specialty diesel fuel committee as highly desirable. formulation will optimize LTC over all modes of operation and modify its priorities accordingly based on the data. Finding 3-8. DOE is shifting prematurely to component research to support the 2013 stretch goal of 55 percent Finding 3-10. Even if LTC is successful at light loads, tradi- t Â hermal efficiency before completely demonstrating the ear- tional diesel operation will likely be necessary at cold start lier 2010 goal of 50 percent. Importantly, after analyzing the and higher loads. Due to the different emission issues at light results of the lengthy and extensive efforts carried out in the loads and heavy loads, it is very implausible that heavy-duty area of low-temperature combustion (LTC), it is considered diesel engines will require no aftertreatment. unlikely that this technology will be a successful enabler of the 55 percent stretch goal at any time in the near term Recommendation 3-10. DOE should undertake an analysis because it cannot be adequately controlled over the full range of a mixed-mode scenario to determine whether unburned of operating conditions of heavy-duty engines and has not HC and CO control in the LTC regime and DPF and NOx demonstrated inherent fuel-consumption advantages. Based control in the traditional diesel combustion regime is not on the open literature, the chances for success of LTC as a more complex and costly than aftertreatment for traditional practical technology appear limited. diesel alone.
ENGINE SYSTEMS AND FUELS 43 Number of Companies to Be Funded Goals Involving Fuels At the level of the proposed funding for FY 2008 and future Introduction years, it is unlikely that five heavy-duty engine manufacturers can be funded adequately as major participants in the compo- The fuel-related goals of the 21CTP were as follows: nent area. This number should be reduced to one or, possibly two, based on the merits of the proposals submitted. 1. By 2010, identify and validate fuel formulations opti- mized for use in advanced combustion engines exhibiting Finding 3-11. At the reduced budget levels for FY 2008 and high efficiency and very low emissions, and facilitating beyond, the inclusion of five engine manufacturers as cost- at least 5 percent replacement of petroleum fuels. sharing participants reduces the ability of funding projects 2. By 2010, identify and exploit fuel properties that could increase efficiency and reduce overall tailpipe emissions of âcritical mass,â which is not in keeping with the national through (1) lower engine-out emissions, including new interest. low-temperature combustion regimes, and (2) enhance- ment of aftertreatment performance for 2010 emissions Recommendation 3-11. DOE should fund only one or, regulations. possibly, two manufacturers during the next phase of the 3. By 2013, identify non-petroleum fuel formulations (i.e., p Â rogram so that only the most promising projects of a sig- renewables, synthetics, hydrogen-carriers) for advanced nificant scope can be accomplished. engines and new combustion regimes for the post 2010 time frame that enable further fuel economy benefits and petroleum displacements while lowering emissions Thermoelectric Energy Conversion Systems levels to near zero, thus adding incentives for using non- A subsidiary issue related to the goal of thermal efficiency p Â etroleum fuels. of 55 percent is DOEâs decision to investigate thermoelectric energy conversion technology as a major opportunity for The meaning of the dates specified in the above goals, improved waste heat recovery systems. 2010 and 2013, were unclear to the committee. For GoalÂ 1, There are only two references to this work in the docu- the committee assumed that 2010 was the date by which mentation provided to the committee. Experimental work the research work required to identify and validate the fuel at NREL is described in Quad Sheet B-1 and FEA analysis formulations specified would be completed and 5 percent work at ORNL is documented in Quad Sheet A-53. Other replacement of petroleum fuels would actually be achieved work may have been presented at other forums such as in-use. For Goals 2 and 3, the committee assumed that the DEER conferences of 2002 through 2007. The work the dates, 2010 and 2013, respectively, were the dates by described seems to still be at a very basic stage of develop- which the research work would be completed. The basis ment for it to merit inclusion in an applied program such as by which DOE selected these dates was not provided to the the 21CTP at this time. Further, it is hard to envision that a committee. thermoelectric device could absorb a significant amount of The engines referred to in the above goals were assumed exhaust energy without imposing an undue backpressure on by the committee to mean the following: the engine system. â¢ Advanced Combustion Engines. These are engines that Finding 3-12. The thermoelectric conversion systems are at are currently being researched by the 21CTP with the a very basic stage and seem to have been âlumpedâ into the goal of achieving 50 percent thermal efficiency at 2010 21CTP as a matter of budgetary convenience for more basic emissions. These engines are being developed for the work going on primarily at the National Laboratories. current specification for No. 2 diesel fuel. â¢ New Combustion Regimes and Low Temperature Com- Recommendation 3-12. The thermoelectric conversion bustion Regimes. Both of these terms are assumed to research should be removed from the 21CTP program until a refer to the process of more thoroughly premixing the more advanced level of technical maturity is attained. At the fuel and air prior to combustion at very lean air/fuel very least, a technical analysis of the candidate waste energy ratios to achieve low combustion temperatures. recovery systems is needed to determine if future efforts on thermoelectric conversion systems within the framework of Diesel fuel has been the primary truck fuel in the United the 21CTP are justified. States, and around the world, for many years. Currently, heavy trucks and buses, almost all of which use diesel fuel, consume 21 percent of the total surface transportation fuel Kevin Stork, DOE, FCVT, âFuel Technologies R&D for Heavy Trucks,â Presentation to the committee, February 9, 2007, Washington, D.C., Slide 3.
44 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP FIGURE 3-6â Surface transportation fuel use. SOURCE: Vinod K. Duggal, Cummins Engine Co., Inc., âDiesel Engine R & D and Integra- tion,â Presentation to the committee, Washington, D.C., February 9, 2007, Slide 4. Fig 3-6, bitmapped used in the United States, as shown in Figure 3-6.10 Off-road the basic hydrocarbon portion obtained from petroleum, or vehicles are also significant consumers of diesel fuel while supplementing it with bio-derived or other non-petroleum- light-duty vehicles predominately use gasoline. Overall, derived diesel fuel, must be sensitive to the impacts of fuel approximately 40 percent of the total surface transportation cost. fuel used is diesel fuel. Very little diesel fuel is used in the United States for light-duty vehicles. That may change if, Nonpetroleum Fuels for Advanced Combustion Enginesâ as expected, fuel economy standards (CAFE) are increased, Goal 1 and the use of light-duty diesel engines increases because of their inherently higher fuel economy. DOE recently clarified to the committee that this goal The United States has a very extensive and well-devel- deals with advanced nonpetroleum-based fuels and that oped refining, distribution and storage system for provid- future engine designs should operate cleanly and efficiently ing low-sulfur diesel fuel, essentially all of it derived from on fuels with a range of fuel properties, regardless of fuel domestic and imported petroleum. Engines and diesel fuels feedstock.11 Because the entire truck fleet takes many years have been designed to work well together in terms of vehicle to replace, existing engine designs will be in operation for operation and performance, fuel economy, and emissions many years to come. Therefore, properties of fuel available control. ASTM fuel specifications help to ensure that avail- in-use must be within the range of the diesel fuel specifica- able engines and fuels are compatible. The extensive work tions that were used in the design of these engines in prior that has been required to ensure engine and fuel compatibility years. In addition, current engines as well as future engine will have to be taken into consideration when developing designs will need to operate cleanly and efficiently on fuels advanced combustion engines and replacements for petro- independent of the fuel feedstock. leum fuels. The first part of Goal 1 deals with advanced combustion A considerable portion of the freight movement in the engines exhibiting high efficiency and very low emissions. United States is by truck. The trucking industry is very As noted earlier in this section, these engines are currently sensitive to fuel cost. Thus, any efforts to modify fuel for being researched by the 21CTP with the goal of achiev- use in diesel engines by either changing the composition of ing 50 percent thermal efficiency at 2010 emissions. As 10Vinod K. Duggal, Cummins, Inc., âDiesel Engine R & D and Integra- 11DOE responses to committee queries on engine systems and fuels, tion,â Presentation to the committee, Washington, D.C., February 9, 2007. delivered by Ken Howden via e-mail, March 27, 2007.
ENGINE SYSTEMS AND FUELS 45 TABLE 3-10â Comparison of ASTM Specification for No. 2 Diesel Fuel and 100 Percent Biodiesel Â D975-No.2 Diesel Fuel D6751-Biodiesel (B100) Units ASTM Method Applicability Diesel fuel suitable Blend component up to Â°C D93 for use in on-highway 20 percent in any diesel engines fuel or home heating oil Flash point 52 min. 130 min. Â°C D93 Water and Sediment 0.050 max. 0.05 max percent volume D2709 Distillation Temperature, 90% Recovered 282-338 Not Specified Â°C D86 Distillation Temperature, Atmospheric Equivalent, Not Specified 360 max. Â°C D1160 ââ 90% Recovered Kinematic Viscosity, 40Â°C 1.9-4.1 1.9-6.0 mmÂ²/sec D445 Ash 0.01 max. Not Specified percent mass D482 Sulfur 0.0015 max. 0.0015 max. percent mass (ppm) D5453 Copper Strip Corrosion No. 3 max. No. 3 max D130 Cetane Number 40 min. 47 min. D613 One of the following: â Cetane Index 40 min. Not Specified D976 â Aromaticity 35 max. Not Specified percent volume D1319 Cloudpoint Report Report Â°C D2500 Ramsbottom Carbon on 10% Distillation Residue 0.35 max. Not Specified percent mass D524 Carbon Residue 100% Sample Not Specified 0.05 max. percent mass D4530 Lubricity, HRFF@60C 520 max. Not Specified microns D6079 Calcium/Magnesium combined Not Specified 5 max. ppm (ug/g) EN14538 Sulfated Ash Not Specified 0.02 max. percent volume D874 Acid Number Not Specified 0.50 max. mg KOH/gm D664 Free Glycerin Not Specified 0.020 max. percent mass D6584 Total Glycerin Not Specified 0.240 max. percent mass D6584 Phosphorus Content Not Specified 0.001 max. percent mass D4951 Sodium/Potassium combined Not Specified 5 max. ppm EN14538 Oxidation Stability Not Specified 3 min. hours EN14112 SOURCE: DOE responses to committee queries on engine systems and fuels, delivered by Ken Howden, DOE, FCVT, via e-mail, July 27, 2007. explained in this chapter, these engines are modifications â¢ Biodiesel primarily, but also biomass-to-liquids of existing production diesel engines with conventional (BTL) combustion systems using high pressure, common-rail fuel â¢ Oil sands and shale oil injection systems, advanced turbocharging systems and cooled EGR, along with PM and NOx aftertreatment systems. Biodiesel is a fuel comprised of mono-alkyl esters of The production engines were originally developed for the long chain fatty acids derived from vegetable oils such as current ASTM specification for No. 2 diesel fuel and the soybeans or animal fats, designated B100 and meeting the modified versions of these engines for the 21CTP program requirements of ASTM International Specification D6751. were Âtailored for the same fuel specification. This standard specification for biodiesel was issued in 2002. The second part of Goal 1 deals with 5 percent replace- The specification for biodiesel fuels does not depend on the ment of petroleum fuels with non-petroleum fuels. DOE feedstock and/or processing method. The specification is explained that their Fuel Technologies R&D program con- designed to ensure safe operation in a compression-ignition sists of two components: Advanced Petroleum-Based Fuels engine (Hoar, 2007). Biodiesel is not raw vegetable oil; (APBF) and Non-Petroleum-Based Fuels (NPBF).12 The it must be produced by a chemical process that removes specific activity of the NPBF component that applies to this glycerin from the oil. Table 3-10 show a comparison of the objective is research to resolve barriers pertaining to use of biodiesel specification, ASTM 6751, with ASTM 975 for non-petroleum fuels as direct replacements of conventional conventional No. 2 diesel fuel. fuels. Fuels and fuel sources under consideration by DOE As noted in Table 3-10, many of the physical proper- include: ties considered in these specifications for biodiesel meet or exceed the stringency of the conventional No. 2 diesel fuel specification. However, several physical properties speci- fied for No. 2 diesel fuel, such as T90, aromaticity and ash, 12Kevin Stork, DOE, FCVT, âFuel Technologies R&D for Heavy Trucks,â are not specified for biodiesel, thereby making transparent Presentation to the committee, February 9, 2007, Washington, D.C. operation in current diesel engines problematic. Experience
46 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP to date with biodiesel has shown some favorable properties Sept. 11, 2007, a report by the Organization for Economic (lubricity, sulfur content and lower particulate matter emis- Cooperation and Development (OECD) unequivocally rec- sions) compared with conventional diesel fuel. ommended that governments around the globe phase out To date, EPA has considered biodiesel fuel as âsubstan- their biofuels subsidies (Ngo, 2007). It characterized them as tially similarâ to diesel fuel, which precludes producers from simply ushering in inefficient new sources of energy supply. having to go through the laborious EPA fuel waiver request The OECD report said biofuels would cut energy-related program. emissions by 3 percent at most, and that their cost greatly Another potential shortcoming is that the biodiesel outweighs their benefits. The reportâs authors stated, âWhen specification does not specify composition. Biodiesel fuel acidification, fertilizer use, biodiversity loss and toxicity of composition will depend on the source (rapeseed oil, soy agricultural pesticides are taken into account, the overall oil, palm oil, coconut oil, waste cooking oil, etc.), and the environmental impacts of ethanol and biodiesel can very production technology. Thus, the chemical composition of easily exceed those of petrol (gasoline) and diesel fuel.â biodiesel fuels will vary greatly, and their composition will The authors of this report take no stance on the future of determine their effects on engine operation, deposits, emis- biofuels in the United States. However, as pointed out here sions, etc., when blended into conventional diesel fuel. To and elsewhere in this section, there are many issues involv- eliminate some of these potential problems, refinery-based ing biodiesel that have to be resolved before it can become processes, such as Neste Oilâs Next Generation Biomass to a viable commercial success. It is incumbent that the DOE Liquids (NExBTL) process (Schill, 2007) have been devel- stay in the mainstream regarding all of these issues. oped to process the biofuels feedstock in the refinery along DOE, especially at NREL, together with biodiesel sup- with the petroleum. This could help ensure more uniform pliers and users are actively exploring the compatibility of fuels with consistent properties when biodiesel is a refined biodiesel fuels with current and future engines. Potential component of diesel fuel. biodiesel performance concerns that are being evaluated In the United States and around the world, biodiesel are: production facilities are being built in large numbers. The Renewable Fuels Standard (RFS) of the Energy Policy Act of 1. Deposit control, especially in the fuel system and at 2005 has had, and will continue to have a role in the increase the injector tips in production facilities in the United States. Currently in the 2. Filter plugging and water separator performance, espe- United States, there are more biodiesel production facilities cially the influence of low temperature properties than refineries making diesel fuel, and many more are being 3. Oxidation stability built and planned. However, their fuel production capacities 4. NOx emissions are very small compared with refineries. In 2005, biodiesel 5. Impact of particulate properties on DPF performance, production was less than one percent of refinery produc- ash loading in the DPF and EGR cooler fouling tion of 2.8 million barrels per day of diesel fuel (EIA). The 6. Impacts on lubricant performance National Biodiesel Board estimated that 16,000 barrels per day would be produced in 2006 (Moran, 2006), which is DOE did not report on the status or timetable of their significantly less than the several million barrels per day of efforts to resolve these concerns. refinery production of diesel fuel. A major exploration of biodiesel fuel issues is currently Hartâs International Fuel Quality Center/Global Biofuel being conducted by the Japanese Clean Air Program (JCAP), Center recently projected that the worldâs biofuel capacity with which NREL has maintained close contact. DOE should could increase threefold from its current capacity of 5 billion explore more joint activities on biofuels with JCAP. gallons per year. Even if U.S. biofuels capacity increased With modern diesel engines moving toward hot fuel circu- similarly by 2010, it would only reach less than 3 percent lation (via common rail systems), potential oxidation stabil- of refinery production of diesel fuel, which would be insuf- ity issues will need to be resolved. It is generally accepted ficient to replace 5 percent of petroleum-derived diesel that palm oil derived biodiesel (from Southeast Asia) has fuel. Therefore, it is highly unlikely that the goal of at least better oxidation stability than either rape methyl ester (from 5Â percent replacement of petroleum fuels could be achieved Western Europe) or soy methyl ester (from the United by 2010 using biodiesel alone. States). However, a recent study published by SAE (Goto and An additional and increasing concern with biofuels is the Shiotani, 2007) pointed out that oxidation stability worsens competition between biomass use for food and for fuel. This as the palm oil-derived methyl ester biodiesel fuel content is already evident in the United States with the increased increases, or the fuel temperature increases, with consequent production of corn for ethanol taking away cropland from loss of oxidation stability and fuel system corrosion. other products, such as soybeans, and resulting in increased The impact of biodiesel on exhaust NOx emissions is not prices for both soy and corn dependent food products. clear. EPAâs position is that biodiesel increases NOx emis- The controversy over biofuels and ethanol continues to sions; NRELâs position is that it has little or no effect. A grow. As reported in the Ethanol and Biodiesel News of recent paper (Sobotowski et al., 2007) supports EPAâs posi-
ENGINE SYSTEMS AND FUELS 47 tion. This issue will need to be resolved. The discrepancy Replacement of 5 percent petroleum fuel by 2010 is a may be related to the chemistry of the biodiesel fuels used in very aggressive, if not unrealizable goal, especially consider- the various studies. To resolve the impasse between DOE and ing that the most optimistic increase in biodiesel production EPA, an independent body should look at all of the biodiesel capacity could only achieve replacement of 3 percent of studies to see if the chemistry of the fuel can be related to its petroleum fuels by 2010, as previously discussed. Regard- impact on NOx emissions. ing compatibility of the fuel with existing engines, DOE did Todayâs diesel fuel can be improved by blending with not provide the committee with a timetable for the resolu- gas-to-liquid (GTL) components. This approach is used in tion of the issues associated with the use of biodiesel fuels Europe for premium quality diesel fuel. However, DOE did or blends. Achieving this goal is also highly contingent on not comment on any work on diesel fuel blended with GTL the acceptance of biodiesel blends by the diesel engine and components. trucking industries, especially from a cost and operational Independent of their source and the process for genera- performance perspective. Current and proposed federal and tion, biodiesel fuels should be characterized by their chemi- state legislation contain tax incentives for the biodiesel indus- cal and physical properties. These properties should be used try that could assist with the acceptance of biodiesel fuels. to correlate with the fuelâs performance in engines and Without these incentives it is unlikely that biodiesel will have impacts on emissions. a major impact. A biodiesel blend, as distinguished from biodiesel fuel, Biodiesel fuels are in vogue because of their presumed is a blend of biodiesel fuel meeting ASTM 6751 with benefits regarding greenhouse gases, especially carbon p Â etroleum-based diesel fuel designated BXX, where XX is dioxide (CO2), reduction. A recent study from Wetlands the volume percent of biodiesel. DOE is focused on ensuring International (Max, 2007) in the Netherlands has challenged that B20 is compatible with engines with diesel particulate that assumption regarding palm oil. It concluded that the filters/selective catalytic reduction/NOx absorber catalysts CO2Â reduction benefits of palm oil were overwhelmed by that will enter the market in the 2007-2010 timeframe.13 theÂ CO2 released when swamps in Southeast Asia were However, to date, the diesel engine manufacturers, through drained to provide land for planting the palm trees. Although the Worldwide Fuel Charter, have recommended a maximum this will not apply in the United States, it lends a note of of five percent biodiesel (fatty acid methyl ester) blended in caution, and suggests that rigorous âwell-to-wheelâ analy- diesel fuel, and that ASTM Standard D6751 be followed. ses, especially in the generation of the crops providing the DOE must allay the engine manufacturersâ concerns about biodiesel feedstocks, are needed to thoroughly explore the blends containing more than 5 percent biodiesel fuel before benefits of biofuels. Land use issues must be incorporated such blends can be accepted. into the âwell-to-wheelâ analyses. DOE has stated that they are not aware of operational The Low Carbon Fuel Standard (LCFS) concept is likely issues for B20 or lower blends prepared from B100 that to be implemented in the United States and Europe. 15 It meets D6751, with one exception. Some biodiesel blends can essentially calls for a 10 percent reduction in carbon intensity cause cold temperature filter plugging even when the cloud of transportation fuels by 2020. Biofuels, including bioÂdiesel, point of the blend indicates it should be satisfactory. This are one of the most likely near term options. DOE, EPA, and may be caused by an impurity that is not currently limited in industry should work closely together on this standard as it D6751. NREL and other participants at ASTM are working is being implemented. on this issue and expect to ballot a new requirement for the In addition to biodiesel as a potential replacement for ASTM specification during 2008. DOE acknowledges that petroleum fuels, DOE is also investigating oil sands and experience is still being gained, especially with 2007 and shale oil sources of fuel as part of its Non-Petroleum-Based later on-highway engines. As more information is acquired, Fuels (NPBF) efforts. DOE did not provide additional a further update to the specification may be required.14 information on work directed toward these fuel sources, and DOE did not provide the committee with plans for achiev- did not provide any indication of the potential extent of the ing the goal of replacing 5 percent of petroleum fuel with commercial use of these fuels by 2010. non-petroleum fuels by 2010. This goal is highly dependent Oil shale for many years has been a prominent potential on three factors: source of oil. The resource base, primarily in arid Utah and Colorado, is very large. But it has not been commercially 1. Biodiesel availability tapped to any extent because of environmental concerns 2. Compatibility with existing engines related to water availability and surface mining. To lessen 3. Fuel cost the concerns over surface mining, attention is being given to in-situ retorting to generate the shale oil. In recent years, fuels made from Canadian tar sands have 13Kevin Stork, DOE, FCVT, âFuel Technologies R&D for Heavy Truck,â been commercialized and blended into diesel fuel. More than Presentation to the committee, Washington, D.C., February 9, 2007. 14DOE responses to committee queries on third meeting, delivered by Ken Howden via e-mail July 27, 2007. 15See http://www.energy.ca.gov/low_carbon_fuel_standard/index.html.
48 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP one million barrels per day of fuels from Canadian tar sands in these studies âmay remain undisclosed,â which severely are now being used in the United States. That volume was limits the usefulness of this project. Furthermore, because the expected to grow; however recent environmental concerns in committee is concerned about the viability of low tempera- Alberta may limit the growth. ture combustion (discussed in this chapter), the applicability of the results of this project may be limited. Finding 3-13. It is unlikely that the goal of identifying Furthermore, the implication of the FACE project, which and validating non-petroleum fuel formulations, optimized is exploring fuels significantly beyond todayâs ASTM speci- for use in advanced combustion engines, will be achieved fication for No. 2 diesel fuel, is of serious concern. DOE did by 2010. DOEâs nonpetroleum fuels effort is focused on not address the concern that the FACE project may define resolving biodiesel operational issues and commercialization optimum fuel properties for an engine with a new combus- barriers, but DOE did not provide a timetable for successful tion regime that are not consistent with the properties of resolution of these efforts. DOE is also investigating oil sands conventional diesel fuel defined in the ASTM specification and shale oil as other sources of petroleum fuel replace- for No. 2 diesel fuel. A potential implication of such a result ment. DOE did not present a plan for 5 percent replacement is that an engine with a new combustion regime may require of petroleum fuels. The Renewable Fuels Standard of the a separate fuel, which would entail significant problems in Energy Policy Act of 2005 is likely to have a role in accel- the refining, distribution, storage, availability and cost of erating the availability of nonpetroleum fuels. a special diesel fuel for these engines. Additionally, if the emissions performance of vehicles with engines having a Recommendation 3-13. DOE should continue to work new combustion regime is contingent on use of specialized with biodiesel developers and users to ensure compatibility fuels, it is unlikely that the EPA would grant approval without when biodiesel is blended with conventional diesel fuel guarantees of fuel availability. and problem-free use of biodiesel fuels in diesel engines. The history of liquid fuel (both gasoline and diesel fuel) Successful deployment will require resolving operational use in the United States shows little or no success for highly issues and updating the biofuel specifications. Development specialized fuels with limited sales potential. An example of of refining technology to make acceptable diesel from shale this is the very limited availability of E85 fuel (85 percent oil or tar sands is not high-risk research suitable for federal ethanol, 15 percent gasoline) for the millions of recent model funding and should be left to the private sector. DOE should year vehicles that can utilize this fuel. Even assuming suc- develop specific plans, including key actions and timetables, cess of engines with low temperature combustion regimes, for 5 percent replacement of petroleum fuels. there will be very few vehicles in the marketplace with them for many years. Trucking companies are unlikely to buy vehicles with these engines without widespread availability Fuels for Low-Temperature Combustion Regime Enginesâ of the specialized, reasonably priced fuel needed for these Goal 2 engines. The committee interpreted Goal 2 as being directed toward Refiners do not like to make small quantities of special- fuel properties of petroleum-based fuels that could have ben- ized fuels, especially if it requires capital expenditures. eficial effects on engine efficiency and emissions, including Production, distribution and storage of these fuels will cost aftertreatment performance with emphasis on engines with more per gallon than for conventional diesel fuels. Refueling new low temperature combustion regimes. Directly address- stations will not readily either give up an existing tank and ing this goal is the other component of DOEâs fuel technol- pump, or install a new tank and pump, for a specialized fuel ogy R&D program identified as Advanced Petroleum-Based with small demand. Fuels (APBF).16 While it is important to continue with R&D to understand A key DOE project focused on this goal is the FACE the optimum fuel properties for current and future engines, (Fuels for Advanced Combustion Engines) project. This it will be more critical to be able to make the future engines project, which operates under a Coordinating Research operate on the conventional diesel fuel or gasoline that will Council working group, was formed to better understand the be readily available for many years. The committee does not fuel effects on LTC (low temperature combustion) engines. believe that specialized fuels will be commercially available The fuel variables being investigated are cetane number, for advanced combustion engines, especially with the low aromatic content, and T90 point. Fuels with variations in volume that will be required for many years for vehicles these properties are being distributed to teams researching with these engines. To gain a better appreciation for the multiple approaches to advanced combustion engines and issues involved with use of a specialized fuel with advanced aftertreatment systems. DOE stated that the engine hardware combustion engines, DOE should meet with at least several major oil companies to explore the practical realities of pro- viding a special fuel. 16Kevin Stork, DOE, FCVT, âFuel Technologies R&D for Heavy With respect to the emission reduction portion of this Trucks,â Presentation to the committee, Washington, D.C., February 9, 2007, Slide 4. objective, the difficulty in defining the properties of fuels
ENGINE SYSTEMS AND FUELS 49 for engines with new combustion regimes was pointed out understanding and development of future fuels. The focus of in a recent paper published by SAE (Kalghatgi et al., 2007). this effort appears to be on oil sands. The authors said that the debate over reducing engine-out There are many potential sources of non-petroleum emissions from diesel engines is tied to whether or not future derived diesel fuel, including; oil shale, coal, tar sands, natu- engines, especially light-duty diesel engines, will require ral gas and biomass. Technology exists to make diesel fuel higher cetane number than currently is sold in the United with excellent properties from coal and natural gas. Some States. If such engines need to promote premixed combus- gas-to-liquids facilities have been commercialized outside tion, higher cetane number fuels will not help. These engines the United States. None has been announced for construction are expected to require lower cetane number fuel to allow in the United States. time for thorough premixing of the air and fuel prior to the Extreme caution has to be exercised when using diesel initiation of combustion. fuels made from these sources. For example, engine and fuel system failures have been reported (Peckham, 2007) with Finding 3-14. DOE is exploring fuel properties of Âpetroleum- light-duty pickup trucks using diesel fuel derived entirely based fuels that could have beneficial effects on engine from tar sands. DOEâs Pacific Northwest National Lab is efficiency and emissions, including aftertreatment. The investigating this problem. Although it is unlikely that future committee is concerned about the viability of low tem- diesel fuel will be produced entirely from tar sands, this perature combustion regimes used in this effort, and that the failure indicates that a thorough investigation of this issue applicability of the results of this project may be of limited is required. James Eberhardt of DOE has cautioned that value. The committee is also concerned that DOEâs work more attention needs to be paid to the molecular structure may define optimum fuel properties for an engine with a new of these new fuels, rather than only the ASTM D-975 diesel combustion regime that are not consistent with the properties fuel specifications. of conventional diesel fuel defined in the ASTM specifica- The goal of identifying fuel formulations that will tion for No. 2 diesel fuel. A potential implication of such a improve fuel economy and reduce emissions is optimistic, result is that a future engine with a new combustion regime perhaps to the point of being unrealistic. The synthetic fuels may require a separate fuel, which would entail significant being mentioned for this goal are all hydrocarbon-based fuels problems in the refining, distribution, storage, availability that would be expected to have combustion characteristics and cost of a special diesel fuel for these engines. similar to conventional diesel fuel. It appears unlikely that the fundamental mechanisms that control the formation of Recommendation 3-14. The committee recommends HC, NOx, and particulate emissions in a diesel engine can be against assuming that specialized fuels will be commercially dramatically altered with a change in the fuel formulation to available for future engines with new combustion regimes. the extent that the emissions could approach zero. Due to the issues concerning the viability of low temperature combustion regimes and commercially available specialized Finding 3-15. DOE provided little insight into the scope fuels, DOE should consider redirecting these efforts toward and magnitude of the effort to address the goal of develop- work with greater probability of contributing to the overall ing non-petroleum fuel formulations beyond biodiesel that goals of the 21CTP. could provide additional fuel economy improvements and near-zero emissions. DOE did not report any specific work plans, results, or timetables addressing this objective. Nonpetroleum Fuels for the Post 2010 TimeframeâGoal 3 The committee assumed that Goal 3 was intended to Recommendation 3-15. DOE should reaffirm that this goal emphasize the development of nonpetroleum fuel formula- should continue to be pursued. If the goal is considered to tions beyond biodiesel, previously addressed by Goal 1. The strongly contribute to the overall 21CTP goals, DOE should goal also addresses benefits of these fuels in providing addi- develop specific work plans and timetables for addressing tional fuel economy improvements and emission reductions. this goal. The discussion below will first address the potential fuel formulations followed by the potential functional benefits In 2005, Reaction Design of San Diego, Calif., a devel- in fuel economy and emissions. oper and licensor of commercial simulation software used DOEâs report on their work on this objective to the com- for modeling the kinetics of fuel combustion, formed the mittee provided little insight into the scope and magnitude Model Fuel Consortium (MFC). 17 The activities of the of the effort. DOE briefly mentioned that they planned to MFC are directed toward the creation of new test-fuel investigate fuels with properties that capture synthetic fuels. formulations as well as the establishment of a database for Also briefly mentioned was their effort to resolve barriers certified fuel models that will be accessible by the various pertaining to fuels derived from oil sands and shale oil. DOE has established a synergistic team with the Canadian 17Available at http://www.reactiondesign.com/support/open/mfc.html. Center for Upgrading Technology (NCUT) to improve the A Â ccessed May 30, 2007.
50 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP members of the consortium. Model fuels are a unique mix Ken Howden, program director of the 21CTP, mentioned of a few pure chemicals that are intended to reproduce the the phrases, âemit little or no pollution,â and âdevelop and combustion behavior of more complex commercial fuels. demonstrate an emissions-compliant engine systemâ19 and The main computer codes used by the MFC are CHEMKIN stated that among the programâs significant accomplish- and KINetics, both of which are commercially supported by ments, âcollaboration has enabled production diesel engines Reaction Design. to meet stringent 2007 emissions while maintaining high It should be noted that this type of work has been going efficiency.â20 on in government and industry laboratories and academic Jim Eberhardt, Chief Scientist of the FCVT, said âDOE institutions for many years and that it is exceedingly difficult with industry is developing more sulfur tolerant catalysts to capture the detailed and complex kinetics of realistic fuels under Combustion and Emission Control and Advanced and their performance in actual engine combustion systems. Petroleum-Based Fuels-Diesel Emission Control (APBF- Success is far from guaranteed. Nevertheless, improvements DEC) activities.â21 in this capability offer the promise of faster and more cost- Gurpreet Singh listed, under barriers, âemissions: inadeÂ effective evaluation of current and future fuel formulations quate simulation capabilities, lack of readily implemented in existing and new engine designs as well as in new com- sensing, robust process control systemâ and âFuels: need bustion concepts. understanding of fuel property effects on NOx and particulate In addition, the MFC and Reaction Design, with partners emission characteristics and implications on DPF opera- from Chevron and the University of Southern California, has tion.â Thus, the 21CTP and DOEâs role in the exhaust afterÂ been recently awarded a grant from the U.S. Department of treatment arena is not very well defined, and measurement Energyâs FCVT to study the combustion of various biofuels. against specific objectives is not possible. In spite of these The program is aimed at developing efficient, environmen- statements, some significant contributions have been made, tally friendly transport fuels that will lessen the U.S.âs depen- as outlined by Singh.22 dence on petroleum. The goals of the program are generally Ron Gravesâs presentation thoroughly reviewed the sta- consistent but more aggressive than DOEâs 21CTP goal to tus of several emissions treatment projects. The âOverview optimize fuel formulations for current-generation diesel of Goals and Status of Major Engine Technology Projects engines that incorporate some non-petroleum-based biofuel- with Industryâ outlines several emissions and aftertreatment blending components. A 5 percent replacement of petroleum accomplishments and future goals.23 fuels is an initial target with an additional 5 percent set for Duggal stated that the heavy-duty engine technology 2010 diesel engines. However, based on the impacts on roadmap included potential improvements of âelimination of refinery operations and fuel blending facilities, it is unlikely NOx aftertreatment.â24 and Kevin Stork stated that âbalance that this program will be able to influence the introduction of point temperature (for DPF regeneration) decreased with commercial fuels in time to impact 2010 diesel engines. B20- and B100-significant differences in regeneration rate, with blend levels as low as 5 percent (biodiesel).â25 The most significant review of aftertreatment programs Aftertreatment Systems was presented by Ron Graves26 in âEmission Control R&D Introduction Program,â Presentation to the committee, Washington. D.C., February 8, The three goals discussed above in this chapter address 2007. 19Ken Howden, DOE, FCVT, âPartnership History, Vision, Mission, and exhaust emissions and aftertreatment, in terms such as â2010 Organization,â Presentation to the committee, Washington. D.C., February emission compliant,â âemission-compliant, engine system 8, 2007, Slide 2. thermal efficiency of 55 percent by 2013,â âreduce overall 20Ken Howden, DOE, FCVT, âPartnership History, Vision, Mission, and tailpipe emissions,â âlower engine-out emissions,â enhance- Organization,â Presentation to the committee, Washington. D.C., February ment of aftertreatment performance for 2010 emission regu- 8, 2007, Slide 14. 21James Eberhardt, DOE, FCVT, âReview of Findings from Previous lations,â and âlowering emission levels to near zero.â The Heavy Vehicle Review,â Presentation to the committee, Washington, D.C., following material discusses aftertreatment in the context of February 8, 2007. these statements. 22Gurpreet Singh, DOE FreedomCAR and Vehicle Technologies Pro- gram, âOverview of DOE/FCVT Heavy-Duty Engine R&D,â Presentation to the committee, Washington, D.C., February 8, 2007. Discussion 23Ron Graves, DOE, ORNL (Oak Ridge National Laboratory), âEmission Control R&D for Heavy Truck Engines,â Presentation to the committee, The 21CTP program on aftertreatment systems is vague Washington, D.C., February 8, 2007. and does not define the priority for exhaust aftertreatment. 24Vinod K. Duggal, Cummins, Inc., âDiesel Engine R & D and Integra- For instance, the Ed Wall presentation does not mention tion,â Presentation to the committee, Washington, D.C., February 9, 2007. exhaust emissions as part of the top R&D objectives. 18 25Kevin Stork, DOE, FCVT, âFuel Technologies R&D for Heavy Trucks,â Presentation to the committee, Washington, D.C., February 9, 2007. 26Ron Graves, DOE, ORNL, âEmission Control R&D for Heavy Truck 18Ed Wall, DOE, FCVT, âDOE FreedomCAR and Vehicle Technologies Engines,â Presentation to the committee, Washington, D.C., February 8,
ENGINE SYSTEMS AND FUELS 51 TABLE 3-11â Sectoral Breakdown of CRADA Partners in specialized, in some cases one-of-a-kind (for example, Emission Control Research a Â berration-corrected electron microscope with sub-ÂAngstrom resolution) instruments for materials research and character- Sector Share of Total Held by That Sector (percent) ization. Its facilities have been utilized by participants of the Engine/Auto 28 21CTP. Examples are given below. Catalyst Suppliers 18 The replacement value of the instruments in the facility Labs and Government 21 Software/Consulting 18 is approximately $47 million. It is located at the Oak Ridge Universities 15 National Laboratory occupying a space of 37,511 square feet, which houses six centers:27 SOURCE: Ron Graves, DOE, Oak Ridge National Laboratory, âEmis- sion Control R&D for Heavy Truck Engines,â Presentation to the committee, Washington, D.C., February 9, 2007, Slide 7. â¢ Materials Analysis Center â¢ Mechanical Characterization and Analysis Center â¢ Residual Stress Center â¢ Thermography and Thermophysical Properties Center â¢ Friction, Wear, and Tribology Center for Heavy Truck Engines,â which included the following â¢ Diffraction Center statements: The Laboratory makes available to researchers from 1) Expected lower limits of engine-out emissions dictate universities, U.S. industries, and governmental agencies a aftertreatment requirements for NOx. skilled staff providing support in the use of the specialized 2) Progress in NOx control via in-cylinder processes has de- equipment in the six centers. On average, 90 user projects are layed need for exhaust aftertreatment until after 2007. supported each year with projects lasting from a few days to as long as a few weeks. Access is available to qualified users He also detailed the activities of CLEERS, DCT (Diesel through either proprietary or non-proprietary agreements. In Crosscut Team), and DOE labs use of CRADAs. Much has the case of non-proprietary work, the results must be pub- been accomplished through these cooperative groups, per- lished in the open literature; in that case there is no cost to the haps in part, because they are made up of the components user. Users who conduct proprietary work there are charged shown in Table 3-11. for total recovery of costs associated with time and resources. At one time, funding for work at the facility was included in Finding 3-16. No specific goals have been outlined for the budgets of various DOE programs, such as the 21CTP. 21CTP diesel engine aftertreatment systems but some goals However, since FY 2003 it has been treated as a separate line have been set for eliminating aftertreatment. However, as dis- item in the DOE budget. Funding for the User Program is cussed in this chapter, the goal of eliminating aftertreatment allocated on an annual basis and is not prorated for each user does not appear to be achievable in the foreseeable future. project. The budget for FY 2007 is $4.1 million.28 Recommendation 3-16. Specific goals should be set for aftertreatment systems (improved efficiency, lower fuel 21st Century Truck Projects29 That Rely on the High consumption, lower cost of substrates, lower cost catalyst, Temperature Materials Laboratory etc.). Active 2007 Projects Finding 3-17. The CLEERS, DCT, and CRADAs have con- â 1. Austenitic Stainless Steel Alloys for Exhaust Mani- tributed to many successful projects and programs. folds and Turbochargers. The objective is to develop new materials to permit Recommendation 3-17. The 21 CTP should continue with an increase in engine-out temperatures to improve the CLEERS, DCT and CRADA activities for aftertreatment engine efficiency. This is a CRADA between ORNL systems. and Caterpillar. The DOE budget for 2007 is $185,000 with a cost share of $185,000 from Caterpillar. High Temperature Materials Laboratory Introduction 27Edgar Lara-Curzio, âThe High Temperature Materials Laboratory,â The High Temperature Materials Laboratory was estab- Presentation to the committee, Washington, D.C., May 31, 2007. lished 20 years ago as a National User Facility to provide 28Personal communication, Edgar Lara-Curzio, Re: 21st Century Truck Partnership Project Quad Sheets, to the committee, Washington, D.C., MayÂ 21, 2007. 2007, Slide 1. 29As listed in DOE, 2007.
52 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP â 2. Catalyst Characterization. 11. Integrated Approach for Development of Energy- The objective is to develop catalyst devices that Efficient Steel Components for Heavy Vehicle and will meet diesel emissions regulations with minimal Transportation Applications. impact on fuel economy. The DOE budget for 2007 The objective is to develop tools to simulate the for this area is $230,000. formation and influence of non-homogeneous micro- â 3. Catalyst via First Principles. structures in steel processing for truck applications. The object is to use theoretical models to help Validation of the tools using production components develop optimum catalyst systems. The DOE budget is being carried out at Caterpillar. There is no DOE for 2007 is $195,000. budget for 2007. â 4. Characterization of Catalyst Microstructures and 12. Thermomechanical Processing of Titanium and Deactivation Mechanisms. T Â itanium/Aluminum Sheet and Plate. The objective is to develop a better understanding of The objective is to develop new low cost titanium mechanisms that control aging and poisoning behav- powder processing methods for application to large ior of exhaust emission reduction catalyst materials. truck components (e.g., leaf springs) for weight The DOE budget for 2007 is $200,000. reduction. There is no DOE budget for 2007. â 5. Friction and Wear Reduction in Diesel Engine Valve Trains. Completed Projects The objective is to develop a high-temperature, repetitive impact test system and associated test NOx Sensor Development methods, and apply them to the investigation of Advanced Machining and Sensor Concepts candidate materials and surface treatments for diesel Deformation in Ceramics engine valve train components. The DOE budget for Durability of Diesel Engine Materials 2007 is $130,000. This project is planned to continue Durability of Particulate Filters through 2009. High Density Infrared Technology for Surface Treatments â 6. Life Prediction of Diesel Engine Components. High Toughness Materials The objective is to develop methods to assess and Low Cost Manufacturing of Precision Diesel Engine improve the durability (life) of advanced ceramic Components and titanium/aluminum diesel engine components Mechanical Behavior of Ceramic Materials (valves). Such advanced materials provide better Titanium Turbocharger Development engine efficiency through improved thermal manage- Walker Process for Stress Relief ment and reduced mass. The DOE budget for 2007 is Advance Materials for Friction Brakes $95,000. Attachment Techniques for Heavy Truck Composite â 7. Lightweight Valve Train Materials (Titanium). Chassis Members The objective is to develop and validate by in- Basic Studies of Ultrasonic Welding for Advanced Trans- engine tests, the performance of advanced ceramic portation Systems and titanium valves. This project is in coopera- Counter Gravity and Pressure-Assisted Lost Foam tion with Caterpillar. The DOE budget for 2007 is M Â agnesium Casting $175,000. Effects of Ice Clearing Treatments on Corrosion of Heavy â 8. Mechanical Reliability of Piezo-Stack Actuators. Vehicle Materials and Components The objective of the project is to evaluate piezoÂ Friction Stir Welding and Processing of Advanced ceramic materials and stack actuator designs for Materials diesel fuel injectors and develop methods for improv- High Conductivity Carbon Foam for Thermal Control in ing system performance. The project is planned to Heavy Vehicles continue through 2008. The DOE budget for 2007 is Improved Friction Tests for Engine Materials $305,000. Research on Next Generation Truck Brake Materials â 9. Micro-structural Changes in NOx Trap Materials. Brake Lining Coding and Marking The objective is to develop an understanding of Finite Element Truck Crash Modeling the changes that occur in NOx trap materials during Integrated Braking Systems AnalysisâLaboratory Efforts various modes of operation. There is no continuing DOE budget in 2007. Finding 3-18. The High Temperature Materials Laboratory 10. Nano-crystalline Materials by Machining. is a valuable resource, providing specialized instrumentation The objective is to develop high performance metal and professional expertise in support of materials research. matrix composites to reduce rotating mass in diesel 21CTP projects have utilized the laboratory extensively; it engine components. The DOE budget for 2007 is has provided support to 35 different 21CTP projects since $50,000. 2001. Whereas few advanced materials were actually utilized
ENGINE SYSTEMS AND FUELS 53 in the 21CTP project to demonstrate the major 50 percent from heavy-duty vehicles meeting the 2007 and 2010 US thermal efficiency goal, it is expected to contribute to the EPA emissions standards. DOE is a major funder of this 21CTP in valuable ways in the future. program.31 ACES recognizes that any study must address emissions Recommendation 3-18. The DOE should continue to pro- from the combined technologies of new heavy-duty diesel vide 21CTP projects access to the HTML. Although HTMLâs engines, aftertreatment, lubricants and fuels designed to meet budget is not explicitly linked to the 21CTP, DOE should the new standards. It is an animal study using rats and not make every effort to maintain a stable budget for the HTML, focusing on the direct effects in humans. in order to keep it at the âstate of the artâ level, and able to The committee endorses the DOE funding of this study respond to the needs of the broader research community. and recommends that this continues for the remainder of the study until results become available in the 2012-2013 period. Health Concerns Related to Emissions from ACES is a cooperative, multi-party effort to characterize Heavy-Duty Vehicles the emissions and assess the safety and potential health effects of these new, advanced engine systems and fuels. The ACES Introduction program is being carried out by the Health Effects Institute The FreedomCAR and Vehicle Technologies (FCVT) (HEI) and the Coordinating Research Council (CRC). Key program of the Office of Energy Efficiency and Renew- stakeholders and funders of the effort include representatives able Energy (EERE), U.S. Department of Energy, conducts of engine manufacturers, the petroleum industry, emission research to illuminate the health effects of emissions from control manufacturers, EPA, DOE, CARB, and the Natural heavy-duty vehicles. Its goals are twofold: (1) to provide a Resources Defense Council. ACES will utilize established sound scientific basis underlying any unanticipated potential emissions characterization and toxicological methods to assess health hazards associated with the use of new powertrain the overall safety and potential health effects of production- technologies, fuels, and lubricants in transportation vehicles; intent engine and control technology combinations that will be and (2) to ensure that vehicle technologies being developed introduced into the market during the time period. by FCVT for commercialization by industry will not have The characterization of emissions from representative adverse impacts on human health through exposure to toxic advanced diesel engine systems will include comprehensive particles, gases, and other compounds generated by these analyses of the gaseous and particulate material, especially new technologies. In all, 105 papers from the FCVT Health those species that have been identified as having potential Impacts Activity have been published in peer-reviewed health significance. This study will include a chronic bioÂ Â iterature since 1999 (Eberhardt, 2007).30 l assay of cancer end points similar to the standard National Toxicology Program (NTP) bioassay utilizing one rodent species (rats) and assessing cancer and noncancer end points Discussion (including respiratory, immunologic, and other effects for The database upon which the health impact of diesel which there are accepted toxicological tests). These end particulate is evaluated is generally recognized to be in need points will also be measured in a short-term exposure study of updating. The pollutants of major concern are nitrogen after completion of the bioassay using the then aged engine. oxides (NOx) and particulate matter (PM)âboth PM10 (par- It is anticipated that these studies will assess the potential ticles smaller than 10 millionths of a meter Â [micrometer] health effects of these advanced diesel engines systems, will in diameter) and especially PM2.5 (those smaller than identify and assess any unforeseen changes in the emissions 2.5Â micrometers). Both of these classes of pollutants will be and effects as a result of the technology changes, and will reduced with new engine and aftertreatment technologies contribute to the development of a data base to inform future used with cleaner, low-sulfur diesel fuel. In terms of health assessments of the potential health risks relating to these impacts, there is the need for data about the health impacts advanced engine and control systems. associated with the mass and the precise chemical compo- nents of particles for engine systems designed to meet the Major Project Elements and Timing 2007 and 2010 standards. A major new study is underway to address the data ACES is taking place in three phases: gaps identified above. The Advanced Collaborative Emis- sions Study (ACES) is a multiyear, multisponsor program â¢ In Phase 1, extensive emissions characterization (by designed to investigate potential health effects of emissions the Southwest Research Institute) of four production- intent heavy heavy-duty diesel (HHDD) engines and 30James Eberhardt, Chief Scientist, DOE, FCVT, âOverview of the Health Impacts of the Office of FreedomCAR and Vehicle Technologies Program,â 31Brent Bailey, âDiesel Emissions Research at CRCâ (the ACES ÂDiesel Presentation to the committee, Washington, D.C., February 8, 2007. Project), Presentation to the committee, Washington, D.C., May 31, 2007.
54 REVIEW OF THE 21ST CENTURY TRUCK PARTNERSHIP control systems designed meet 2007 standards for PM noncancer health end points that have been associated and NOx are being conducted and will be the basis for with exposure to diesel exhaust (Phase 3B). In addi- selecting one heavy-duty diesel engine/aftertreatment tion, a short-term study (3 months exposure duration), system for health-related studies (Phase 3). No results measuring the same noncancer end points as in the were available at the time of this report. chronic bioassay will be conducted in a different set â¢ In Phase 2, extensive emissions characterization of a of animals after completion of the chronic bioassay group of production-intent engine and control systems to determine whether the exhaust of the 2007 engine meeting the 2010 standards (including more advanced (Phase 3C) will produce emissions that are of concern NOx controls) will be conducted. from the human health standpoint. Due to program â¢ In Phase 3, the selected 2007-compliant engine system slippage, animal studies are now expected to start in would be installed in a specially-designed emissions the Fall of 2008 and may slip further. generation and animal exposure facility (Phase 3A) and will be used in chronic inhalation study with health Subsequently, subject to full evaluation of the 2007 engine measurements at several time periods to form the basis tests, one (or possibly two) selected 2010-compliant engine of the ACES safety assessment (Phases 3B and 3C). system could be installed and characterized (Phase 3D) and This is will include a core 24-month chronic bioassay evaluated in short-term health effects studies (Phase 3E) of cancer and noncancer end points in rats similar to measurÂing the same end points measured after comparable the standard NTP bioassay. In addition to assessing exposure duration in the chronic bioassay and the subsequent potential carcinogenicity of whole diesel exhaust, short-term study with the 2007-compliant engine, as well this chronic bioassay would provide information on as other established end points that require specific animal chronic toxicity through histopathological analyses of models or interventions. The schedule and organization of multiple organs at interim sacrifices and at the end of the study are shown on Figures 3-7 and 3-8, respectively. the study, on mutagenicity, inflammation, and other With respect to the ACES program, the committee supports FIGURE 3-7â Overall schedule, CRC ACES study. SOURCE: Brent Bailey, Health Effects Institute, âDiesel Emissions Research at CRCâ (the ACES Diesel Project), Presentation to the committee, Washington, D.C., May 31, 2007, slide 21. Fig 3-7, bitmapped FIGURE 3-8â Project organization, CRC ACES study. SOURCE: Brent Bailey, Health Effects Institute, âDiesel Emissions Research at CRCâ (the ACES Diesel Project), Presentation to the committee, Washington, D.C., May 31, 2007, slide 21. Fig 3-8, bitmapped
ENGINE SYSTEMS AND FUELS 55 continuation of this study, because of the vital information Kuzuyama, H., et al. 2007. A Study on Natural Gas Fueled Homogeneous it provides. Charge Compression-ignition EngineâExpanding the Operating and Combustion Mode Switching, SAE Paper 2007-01-0176). Max, Arthur. 2007. Scientists Weigh Downside of Palm Oil. Associated Finding 3-19. ACES is a cooperative, multi-party effort to Press, April 1. characterize the emissions and assess the safety and potential Merrion, David F. 1994. Diesel Engine Design, 1994. SAE Buckendale health effects of new, advanced engine systems, aftertreat- Lecture SAE Paper No. 940130 in SP-1011. ment, fuels and lubricants. It is an animal study using rats Moran, Susan. 2006. Biodiesel Comes of Age as the Demand Rises. New York Times. Sept. 12. and not focusing on the direct effects on humans. DOE is Nelson, Christopher R. 2006a. Achieving High Efficiency at 2010 Emis- providing the major funding for this program. sions, Paper presented at DEER Conference, August 23, 2006. Nelson, Christopher R. 2006b. Exhaust Energy Recovery, Paper presented Recommendation 3-19. The committee endorses the DOE at DEER Conference, August 24, 2006. funding of this study and recommends that this continue for Ngo, Peter, 2007. OECD calls out biofuels: âCure worse than the disease.â Ethanol & Biodiesel News, Vol. XIX, No. 37, September 11. the remainder of the study until results become available in NRC (National Research Council). 2000. Review of the U.S. Department the 2012-2013 time period. of Energyâs Heavy Vehicle Technologies Program. Washington, D.C.: National Academy Press. Peckham, Jack. 2007. CARBâs Biodiesel Policy Still Facing Criticism from References Engine Makers, Automakers, Refiners, End-Users. Diesel Fuel News, DOE (U.S. Department of Energy). 2006. 21st Century Truck Partnership Vol. 11, No. 2, January 15. Roadmap and Technical White Papers. Doc. No. 21CTP-003. Washing- Robertson, Gary D. 2007. More layoffs announced by Freightliner in N.C. ton, D.C. December. Associated Press. DOE. 2007. 21st Century Truck Partnership, Project Quad Sheets. Doc. No. SAE (Society of Automotive Engineers International). 2004. J1349 Engine 21CTP-004. Washington, D.C. January. Power Test CodeâSpark Ignition and ÂCompression-ignitionâNet Power Duffy, Kevin. 2004. Heavy-Duty HCCI Development Activities. Presenta- Rating, Rev. August 2004. tion at Diesel Engine Emission Reduction Conference. SAE. 2007. Homogeneous Charge Compression-ignition ÂEngines, Special Flynn, P. F., R. P. Durrett, G. L. Hunter, A. O. zur Love, W. O. Akinyemi, Publication SP-2100. J.Â C. Dec, and C. K. Westbrook. 1999. Diesel Combustion: An Integrated Schill, Susanne Retka. 2007. Heeding Hydrogenation. Biodiesel Maga- View Combining Laser Diagnostics, Chemical Kinetics, And Empirical zine. March. Available at http://www.biodieselmagazine.com/article. Validation, Presented to the Society of Automotive Engineers at the 1999 jsp?article_id=1505&q=&page=all. Accessed May 13, 2008. Annual Congress, Detroit, Michigan SAE Paper No. 1999-01-0509. Sobotowski, Rafal A. Charles R. Schenk, Brian A. Olson, Chien Sze, and Goto, S., and H. Shiotani. 2007. Studies of Fuel Properties and Oxidation Joan K. Whinihan. 2007. Impact of Test Cycle and Biodiesel Concentra- Stability of Biodiesel Fuel, SAE Paper No. 2007-01-0073, January. tion on Emissions. Impact of Test Cycle and Biodiesel Concentration Hoar, Paul. 2007. Biodiesel Quality, Standards and Certification, on Emissions. SAE paper 2007-01-4040. Available at http://www.sae. National Biodiesel Board, January 11. Available at http://www.Â org/technical/papers/2007-01-4040. Accessed May 30,2007. biodieselmagazine.com/article.jsp?article_id=1505&q=&page=all. Tennant, Christopher. 2007. CRC Report Number ACES-1, July, Creation Accessed May 13, 2008. of the âHeavy Heavy-Duty Diesel Test Schedule for Representative Kalghatgi, G., H-E. Angstrom, and P. Risberg. 2007. ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ï¿½ Partially Pre-Mixed Measurement of Heavy-Duty Engine Emissions. Auto-Ignition of Gasoline to Attain Low Smoke and Low NOx at High Van Wylen, Gordon J. 1961. Thermodynamics, Hoboken, N.J.: John Wiley Load in a Compression-Ignition Engine and Comparison with a Diesel & Sons, Inc. pp. 282-284. Fuel, SAE Paper No. 2007-01-0006, January. World Wide Fuel Charter, Available from Alliance of Automobile Manu- facturers, Washington, D.C.