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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program 2 Program Assessments This chapter contains a summary of OHVT's strategy and goals, followed by assessments of individual OHVT R&D programs: on vehicle technologies, on fuels utilization, and on materials technologies. Activities related to environmental and health issues, which are a minor part of the OHVT program, are also addressed. The committee makes recommendations for components of the OHVT R&D program, as appropriate. OVERALL STRATEGY AND GOALS The committee commends OHVT on its systematic approach to R&D. Since OHVT's creation in 1996, the program has developed a technology road map and identified the barriers to achieving the goals of the program. The first road map, which was issued in October 1997, was recently revised, updated, and republished (DOE, 1997, 2000a). OHVT sponsored many workshops in developing its multiyear plans for the road map, eliciting input from the broader technical community and developing relationships with its “customers.” The recommendation for a road map resulted from an OHVT workshop in April 1996 to elicit input from DOE's customers in the heavy-vehicle industry, including truck and bus manufacturers, diesel-engine manufacturers, fuel producers, suppliers to these industries, and the trucking industry. The development of the road map entailed formulating goals consistent with DOE's strategic plan, assessing the status of technologies, identifying technical targets, identifying barriers to achieving the targets, developing a strategy for overcoming the barriers, and determining schedules and milestones (DOE, 2000a). This structure was followed for the three groups of truck classifications: Classes 1 and 2 trucks (pickups, vans, SUVs), Classes 3 to 6 trucks (medium-duty trucks, such as delivery vans), and Classes 7 and 8 trucks (large, heavy-duty, on-highway trucks). OHVT envisions the development of energy-efficient diesel engine technologies for all three classes with near-zero emissions. The following goals are stated in the road map (DOE, 2000a): Develop by 2004 the enabling technologies for a Class 7 and 8 truck with a fuel efficiency of 10 mpg (at 65 mph) that will meet prevailing emission standards. For Class 3–6 trucks operating on an urban driving cycle, develop by 2004 commercially viable vehicles that achieve at least double the fuel economy of comparable current vehicles (1999), and, as a research goal, reduce criteria pollutants to 30 percent below EPA standards. Develop by 2004 the diesel engine enabling technologies to support large-scale industry dieselization of Class 1 and 2 trucks, achieving a 35 percent fuel efficiency improvement over comparable gasoline-fueled trucks, while meeting applicable emissions standards. The road map identifies the following key enabling technologies and areas for study: emission controls (including exhaust-gas after-treatment technologies) combustion technology materials, environmental science, and health effects truck safety engineering simulation and modeling OHVT's strategy includes the active involvement of customers/stakeholders in developing government/industry partnerships. First, DOE and OHVT 's missions, as well as governing statutes, laws, and directives from Congress, must be satisfied. Second, the intersection of the federal mission and the customer's interests must be determined. To help with this step, OHVT conducted a customer focus workshop(s). Third, OHVT has sponsored workshops to identify
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program customers' needs, from which road maps were developed with goals, barriers to development, and multiyear program plans to overcome the barriers. OHVT plans to modify these road maps as new information is collected and use them to determine resource requirements and prepare budgets. Finally, mechanisms have been developed for partnering with organizations outside the federal government. The lessons learned are then used to change the development process and modify the road maps. The committee believes that OHVT has identified its mission well and articulated its vision clearly. The programs seem to be well managed, and OHVT seems receptive to input from its stakeholders, as evidenced by the recognition of the fuel economy implications of the 1998 Consent Decree and the adaptation of program goals to address these new challenges. In addition, program managers have been very effective in identifying competent research teams to conduct projects. The focus of OHVT's initial planning with customers/stakeholders was a workshop in April 1996 attended by representatives of the heavy-vehicle industry including diesel-engine manufacturers, truck manufacturers, truck owners and operators, and trade organizations, as well as representatives of DOE. Workshop participants developed a common vision for the heavy-vehicle industry of the future and recommended that a technology road map addressing common R&D needs and interests be developed. Customers/stakeholders included U.S. diesel-engine manufacturers and heavy-vehicle manufacturers, U.S. automakers (truck divisions), component manufacturers, fleet operators and owners, industry trade organizations, fuel suppliers, materials suppliers, universities, and research organizations (Eberhardt, 2000). Private sector participants included Caterpillar, Inc., Cummins Engine Company, Detroit Diesel Corporation (DDC), International Truck and Engine Corporation (Navistar International Corporation is the parent company), Deere and Company, Johnson Matthey, Englehard, Freightliner, Kenworth, Mack, ARCO, BPAmoco, ExxonMobil, Shell, representatives of the natural gas industry, and others. Since 1996, as part of its R&D strategy to solicit customer input, OHVT has sponsored about 34 workshops, meetings, and symposia focused on a broad spectrum of technologies and needs for the OHVT R&D program. OHVT continues to solicit input from its stakeholder and customer base. OHVT's R&D strategy is to “focus on the Diesel-cycle engine and its fuel requirements as the confluence of energy efficiency, fuels flexibility, and very low emissions for trucks of all classes” (Eberhardt, 2000). The R&D strategy involves the development of clean diesel fuels and blends that can be derived from a variety of feedstocks (e.g., petroleum, natural gas, coal, and biomass) and can be used in advanced, high-efficiency, clean diesel engine technologies. The goal is to produce more efficient light-duty, medium-duty, and heavy-duty trucks. When reviewing federal R&D programs, the role of federally funded R&D vis-à-vis the private sector must always be considered. The National ransportation and Technology Strategy defines research and technology programs that should be supported by the federal government as research that supports long-term national transportation goals. Federal research and technology investments often promote the development of benefits with broad applications to the public that would be difficult for individual companies to fund because they might not recoup their investment or realize a profit. A government role is generally associated with high-risk research beyond the capacity of individual companies. Finally, federal research and technology development generates benefits that will be realized in the long term and, therefore, do not meet the criteria for private sector investment (NSTC, 1994). IMPROVING ENERGY EFFICIENCY A basic understanding of how fuel energy is used in a typical vehicle is essential for determining how investments in R&D could lead to improved energy efficiency. The distribution of fuel energy is difficult to determine in detail because it varies with the type of engine and, for a given engine, varies with the operating conditions. Figure 2-1 illustrates an average fuel-energy distribution for an automobile (NRC, 1992), which includes three energy-distribution categories: exhaust heat, cooling system, and brake work (i.e., the net work delivered to the flywheel). Analyzing the energy distribution in a vehicle is difficult. For example, the transmission has an oil cooler to dissipate losses. One must then determine if these losses should be reflected in the transmission or the cooling system. Designs for improved energy efficiency would minimize the amount of fuel energy going to exhaust heat and the cooling system and increase the fraction of fuel energy going to brake work. In fact, modern diesel truck engines already have a turbo-charger to use exhaust energy to supercharge the engine to increase power. For diesels, exhaust flow rate and energy content decrease with load. Many proposed systems would use more of the exhaust energy and add weight and volume to the engine system; to date, none has proven to be cost effective. Another option, an “adiabatic” engine, has the potential to reduce the energy flow to the cooling system but has other significant drawbacks and is not being pursued (NRC, 1987). A more efficient cooling system could reduce power usage a little (Lehner, 1999). So at this point, only small reductions in exhaust heat and the cooling system seem feasible. For a given indicated horsepower, decreases in engine friction, pumping losses, use of accessory systems, and transmission losses will increase brake horsepower. If these four losses remain constant, an increase in indicated horsepower will increase brake horsepower. Table 2-1 and Table 2-2 show the results of computer simulations of a Class 8
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program FIGURE 2-1 Average fuel-energy distribution for an automobile. Note: proportions vary with vehicle design and operating conditions. Source: NRC, 1992. heavy-duty truck using a commercial diesel engine operating at its rated speed and power while pulling an 80,000-lb GVW vehicle up a 1 percent grade. As Figure 2-2 shows, fuel-energy distribution varies widely for a tractor-trailer combination depending on operating conditions. Reducing vehicle speed or drag is an obvious way to reduce fuel consumption significantly. (OHVT's goal of 10 mpg was for 65-mph vehicle speed.) However, reducing vehicle speed entails trade-offs, such as increased trip transit time and, therefore, increased indirect costs to the trucker, impedance of traffic flow by slow vehicles, possible safety problems, and so on. Reducing the drag coefficient also requires trade-offs. Changes in the shape and contour of the vehicle may reduce load-carrying capability in vehicles with regulatory-restricted sizes and volumes. Return on investment and labor costs tend to push the trucking industry towards higher speeds for greater productivity. Technologies that reduce aerodynamic drag are, therefore, very important. Aerodynamic drag has a nonlinear TABLE 2-1 Distribution of Fuel Energy for a Truck Engine Category Percentage of Fuel Energy Exhaust heat 33.5 Cooling system 24.5 Brake work 42.0 TOTAL 100.0 relation to vehicle speed while the sum of rolling friction and accessory power is estimated to be linearly related to vehicle speed (see Figure 2-2). Therefore, a reduction in drag can have very large payoffs in terms of reduced energy consumption. For example, a reduction in vehicle speed from 70 mph to 64 mph could yield about a 25 percent reduction in power consumed by drag. One of the drag reduction projects discussed later in this report anticipates this kind of drag reduction (Diamond, 2000). Significant reductions in vehicle drag or reduced speeds are the only obvious ways to reduce fuel consumption substantially. Given the practical barriers, however, reductions will probably have to be achieved by small improvements in other areas, such as reducing rolling resistance or accessory power. The remainder of this chapter addresses the primary areas of activity indicated in OHVT's R&D budget breakdown (see Table 1-4): on vehicle technologies, on fuels utilization, and on transportation materials. The committee's review is focused primarily on FY00 but also includes some activities related to environmental and health issues. VEHICLE TECHNOLOGIES Advanced Combustion Engines Introduction OHVT has identified six key enabling technologies for meeting its goals: emission controls (including exhaust-gas after-treatment technology); combustion technology; materials; environmental science and health effects; truck safety; and engineering simulation and modeling. The OHVT road map also notes that R&D on fuels and lubricants is conducted
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program TABLE 2-2 Indicated Work Distribution for a Truck Engine Category Percentage of Fuel Energy Comments Indicated Work 47.0 This energy only includes work at the top of the piston on the compression and expansion strokes. Engine friction (including oil and water pumps) 2.5 Most of this energy goes to the cooling system. Pumping losses 2.5 Most of this energy goes to the exhaust heat. Brake work 42.0 This number, which was used in the Consent Decree and is changing with time, represents an efficient modern engine. jointly by OAAT and OHVT. The committee has determined that two of these, emission controls and combustion technologies, fall into the general category of advanced combustion-engine technologies. Overview of Programs in Combustion and Emissions OHVT's program goals are grouped according to the class range of trucks to which they apply (Classes 1 and 2, Classes 3 to 6, Classes 7 and 8). Using its three main goals as guidelines, OHVT then identified objectives for each class range of trucks and selected projects to address these specific objectives. The programs related to light trucks (Classes 1 and 2) are focused on the development of technologies for clean diesel engines that could replace current gasoline engines. The goal is to improve the fuel economy of light trucks by at least 50 percent (on a gasoline fuel economy equivalent basis), while meeting EPA Tier 2 emissions standards. The OAAT also has a program for light trucks, which is addressing the entire vehicle power train system, rather than focusing on engine development. Thus, OAAT's projects are based on different philosophies of power transmission, such as hybrid-electrical vehicle (HEV) propulsion. Thus, the approaches of OAAT and OHVT are complementary, not duplicative. OHVT's combustion and emission projects are being coordinated through the Diesel Cross-cut Team, which is linked to R&D on diesel engines being conducted under the Partnership for a New Generation of Vehicles (PNGV, which includes most of OAAT's programs). The advantage of FIGURE 2-2 Accessories, aerodynamic drag, and rolling friction as a function of highway speed for a typical Class 8 tractor trailer. (CD= coefficient of drag) Source: McCallen et al., 1998.
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program FIGURE 2-3 Projected contributions of advanced technologies to diesel engine efficiency. Source: DOE, 1997. coordinating R&D by OHVT and PNGV through the Diesel Cross-cut Team is significant leveraging of OHVT funds. However, it also limits OHVT to the time frame and engine-power levels being pursued by PNGV, which has a goal of developing a production prototype of a midsized family sedan with up to three times the gasoline fuel economy equivalent of 1994 cars by 2004 (NRC, 2000). The objective of OHVT's program for heavy-duty trucks (Classes 7 and 8) is to provide basic technical information (e.g., improved understanding of physical processes, new and/or improved system optimization and control techniques) that will lead to the development by 2004 of the enabling technologies for a 10-mpg truck (at 65 mph) while meeting the emission requirements set forth in the Consent Decree. The technical target for the heavy-vehicle engine is a brake thermal efficiency of 50 percent. In anticipation of more stringent emission standards, longer range (by 2006) emission targets of 1.0 g/bhp-hr for NOx and 0.05 g/bhp-hr for PM, or the EPA 2008 standards,1 (whichever is lower), have also been set as research goals. The funding level for OHVT's heavy-duty truck engine program for FY00 is $5.0 million. The program was not funded at all in the previous two years. The goal for medium-duty trucks (Classes 3 to 6) is to develop and demonstrate, by 2004, commercially viable vehicles that achieve, in use, at least double the fuel economy of comparable 1999 vehicles. Another goal is to reduce criteria pollutant emissions to at least 30 percent below the EPA standards prevailing in 2004. Under the newly proposed EPA standards, technologies that produce emission levels 30 percent below the 2004 standards would only have a three-year life because 2007 standards will be much stricter. Because the typical driving cycle of a medium-duty truck is primarily urban delivery, which requires many stops and starts, OHVT believes these vehicles are prime candidates for HEV technology. Consequently, OHVT's research is focused on HEV concepts, and OHVT-supported research on combustion and emission is not directly intended for medium-duty vehicles. However, OHVT program managers expect emission improvements obtained in its programs on light-duty and heavy-duty trucks to be applicable to medium-duty truck engines. Technical Challenges A very aggressive target of 50 percent for the brake thermal efficiency has been set for Classes 7 and 8 trucks. The goal in OHVT's initial road map was 55 percent (DOE, 1997), but this has been lowered to account for the fuel economy penalty likely to be incurred by exhaust-gas after-treatment systems for emissions control. Nevertheless, 50 percent brake thermal efficiency would represent an improvement of about 15 percent in engine efficiency over state-of-the-art engines and would also meet the more stringent emission regulations. Research is being focused on advanced combustion-chamber components for high peak pressure, advanced fuel-injection systems, better air-handling systems, and improved piston/cylinder liner designs to reduce friction. Figure 2-3 shows OHVT's projections for a 15-percent overall improvement in the engine system. OHVT estimates that improved combustion would represent a 1 percent potential improvement in fuel economy, but optimizing the integrated system performance of the power train, including the fuel, engine, and exhaust-gas after-treatment system, will most likely be essential. The distinction between combustion and peak cylinder pressure are hazy at best because the same technologies are being used for both. Therefore, in the committee's opinion, Figure 2-3 represents the results expected for a given project rather than potential improvement. 1 2008 was stipulated in the OHVT road map before EPA issued its proposed heavy-duty emissions standards.
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program In addition, the potential gain distribution shown in Figure 2-3 should be updated. New computations optimizing reductions in emissions and fuel consumption in given operating conditions have shown that dramatic reductions in emissions and fuel consumption may be possible, indicating that an optimized combustion process could be important for lowering both emissions (optimization studies have predicted a factor of 300 reduction in particulate matter and a 30-percent reduction in NOx) and fuel consumption (by 10 to 15 percent) (Senecal and Reitz, 2000; Senecal et al., 2000). Of course, real-life reductions must reflect the entire vehicle operating regime. However, an optimized combustion process, combined with a camless engine that would optimize the engine configuration at a given operating point, might provide major reductions in emissions and, therefore, lessen the need for a complex after-treatment system. Considering the potential significance of these new computations, OHVT should continue to support work on incylinder modeling and simulation. In addition, OHVT should review and update the potential gain distribution shown in Figure 2-3, and the new estimates should be reflected in future budget allocations. Improved fuel economy must be accomplished under the constraint of meeting future EPA and CARB emission standards for all classes of trucks, and these standards are currently driving the choices of technology being investigated and/or developed by the engine industry. The gain in fuel economy that could be attained by “dieselization ” of light-duty trucks is well known (fuel economy is the primary reason diesel engines are the power plants of choice for medium-duty and heavy-duty trucks). However, unless the emission standards can be met, diesels cannot be used. Exhaust-gas after-treatment systems and changes in fuel composition, combined with continued improvements in combustion, appear to be the best hope for meeting the emission standards and for meeting OHVT's program goals. Specific Projects, Objectives, and Goals The list of projects and participants in OHVT's combustion and emission programs is impressive (see Appendix C). Studies on fundamental combustion and spray processes are being performed at the Combustion Research Facility at Sandia National Laboratories (SNL), Livermore, California. Research includes a study of in-cylinder diagnostics to improve the understanding of combustion and emission formation processes, an investigation of homogeneous-charge compression-ignition (HCCI) combustion, a study of injection spray behavior in a constant volume vessel, and the establishment of a special laboratory for investigating alternative fuels. The work at Sandia has the potential of providing knowledge and tools that will help solve critical problems in a longer time frame (2007 –2010). However, the committee is not convinced that these programs fit into OHVT's strategic plan, which has a 2004 time frame. Research on HCCI is a longer term, high-risk, high-payoff project. In HCCI combustion (sometimes referred to as “flameless” combustion), the release of chemical energy is brought about in an essentially homogeneous mixture. Although HCCI combustion is limited to light-load operation, it could be very useful if it could be integrated into the combustion strategy as a portion of the engine-operating regime. A completely developed and implemented HCCI system would represent a “new” mode of combustion, with the potential of reducing in-cylinder emissions more than the target levels for conventional diesel combustion. Although the committee believes R&D on HCCI is important and should be continued, HCCI will almost certainly not be an “enabling” technology by 2004. The fundamental investigation of spray processes in a constant-volume vessel is also valuable fundamental research. However, a constant-volume vessel and an engine differ significantly. For example, the interaction between the fuel injection and the in-cylinder fluid motion, which is not duplicated in a constant-volume vessel, is a critical aspect of achieving maximum performance in an engine. Therefore, at this time, the results of an injection system with a constant-volume vessel cannot be transferred directly to an engine. The results of OHVT 's basic research will provide a basis for testing the validity of advanced computational models and will be helpful in determining directions for further improvements in injection-combustion systems. New insights into air-fuel mixing processes and the preparation of combustible mixtures via fuel injection might also be provided. Like R&D on HCCI, this work has a potentially high payoff and should continue to be part of the OHVT program. Also like HCCI, however, it is not likely to help OHVT meet its near-term goals. Lawrence Livermore National Laboratory (LLNL) has expertise in comprehensive kinetic modeling. For OHVT's projects, modeling efforts are directed towards diesel engine combustion, HCCI combustion, and multicylinder HCCI analysis. At the Los Alamos National Laboratory (LANL), work is proceeding on the development of a next-generation computational tool called CHAD (computational hydrodynamics for advanced designs). Like the projects at Oak Ridge National Laboratory (ORNL) and LLNL, this work is expected to yield valuable tools and knowledge for longer term development (2007–2010). Other national laboratories are also actively involved in the OHVT program, primarily through cooperative research and development agreements (CRADAs). Argonne National Laboratory (ANL) is involved in a CRADA with Caterpillar and the University of Wisconsin to study reducing incylinder emissions via injection of air late in the combustion cycle. ORNL is involved in a CRADA with DDC on diesel exhaust speciation and analysis of lean-NOx catalysts. Additional CRADAs at ORNL include one with Cummins Engine Company to study NOx control in after-treatment systems and catalyzed soot filters and one with Ford-Visteon to study NO sensors.
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program Pacific Northwest National Laboratory, which has expertise in plasma-assisted catalysis and nonthermal plasmas, is involved in two CRADAs, one with Caterpillar and the other with Delphi-DDC. Initial tests on nonthermal plasmas and the plasma-assisted catalysis systems indicate that these approaches to emission reduction may be tolerant to sulfur in fuel (see a later section in this chapter on Fuels Utilization). The R&D at Pacific Northwest is high risk but could have a very high payoff, and OHVT should continue to pursue it. Some carefully controlled engine testing is scheduled to begin soon, but neither of the technologies being investigated at Pacific Northwest will provide a near-term solution to meeting the 2004 emission standards. Finally, OHVT is actively involved in 50/50 cost-share projects with Cummins-DaimlerChrysler, DDC-DaimlerChrysler, and Caterpillar-Ford to develop a competitive Class 2 truck diesel engine for introduction into the SUV and light-truck market. OHVT's funding is being used to facilitate interactions between the heavy-duty engine industry and automotive manufacturers. The work is being performed solely by the partnering companies and is proprietary; results are protected from public disclosure for five years. Therefore, the committee found it difficult to assess the scope and focus of the light-duty engine program, and conclusions about these projects are based on a variety of other sources and the committee members' expertise and experience. One of the companies in the program is probably working on developing technologies that could eventually be incorporated into hardware components for a Class 1 or Class 2 light-duty truck engine. The committee supports OHVT's promotion of industry research on promising, yet high risk, approaches to configuring engine-emission control systems that might facilitate the introduction of more fuel-efficient engines into the light-truck and SUV market. Because the committee did not have access to the 50/50 cost-share programs in their entirety, the focus of the program could not be determined. However, the committee does not endorse using OHVT funds to support specific engine or component development programs by industry. The committee also noted that none of these programs includes other engine configurations, such as gasoline-engine HEVs, which might be able to meet the emission standards more easily and at lower cost than a diesel engine and still have better fuel economy than the gasoline engine currently used in SUVs and light trucks. The committee approves of the longer time frame of many of the projects listed above and encourages OHVT to continue to support them. However, the committee was not convinced that these programs together provide a strategy for meeting OHVT's stated goals in the 2004 time frame. These programs can all stand on their own merit and can be justified as “enablers” for meeting OHVT's long-term research targets, but they should not be included in the strategy for meeting OHVT's near-term goals. Budgets The funding level for all R&D in combustion and emission control at the national laboratories for FY00 is $4.215 million (see Appendix C): $1.35 million is being spent on after-treatment research systems; $1.94 million on combustion research; and $925,000 on control technology, technology evaluation, and support for the Diesel Cross-cut Team. OHVT's budget for the 50/50 cost-share program for the Class 2 diesel engine development is $18.0 million. Program Balance Funding for the OHVT program as a whole is weighted very heavily towards industry and the national laboratories: industry, 72 percent; national laboratories, 18 percent; other (e.g., small businesses), 6 percent; and universities, 4 percent. The advantage is that OHVT has tremendous leverage of its financial resources. The disadvantage is that the emphasis and the bulk of the funding may be inconsistent with a long-term research time horizon. The committee is also concerned that the portfolio of projects covers too broad a range of activities rather than focusing on critical technologies. OHVT appears to have established good communications with OAAT programs in the PNGV program. OHVT should continue to participate in this dialogue to ensure that OHVT programs and OAAT/PNGV programs are as well coordinated as possible. The delay between the initiation of a research program for engines and the introduction of a product is approximately eight years (see Figure 2-4). The delay between the decision to produce a product and production is approximately three years. This leaves only five years between the initiation of a research program and the use of the results to produce or improve a product. Therefore, for OHVT to meet its 2004 production target, programs initiated in 1997 should be nearing completion, and newer programs with a longer time horizon should be under way. The initial program was organized to be consistent with the eight-year delay. However, OHVT has not periodically reevaluated its research portfolio in terms of the eight-year horizon. OHVT's R&D on advanced combustion engines has potential short-term, midterm, and long-term payoffs. However, OHVT did not demonstrate to the committee an updated logical structure or global vision for future programs. The committee believes it essential that OHVT put in place a process for periodically (at least annually) reviewing and updating its individual programs and their overall goals and targets to reflect an eight-year or longer time horizon. The initial review should also develop a logical structure and global vision for the program. The rationale of this process should be to identify OHVT technologies that, if successfully developed in the next decade, would be of maximum benefit to the nation. The review process would also enable
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program OHVT to assess the status of current programs and determine if they are yielding benefits. FIGURE 2-4 Increasing the efficiency of diesel engines and brake-specific fuel consumption (BSFC = lbs of fuel per hour per unit of engine power) for research and production engines. Source: Eberhardt (2000), based on information from Caterpillar, Inc. In the committee's opinion, the most crucial technologies by far are those that will enable diesel engines to meet future emission regulations. If they cannot meet these standards, they cannot be sold, regardless of their potential fuel savings. The committee believes that the development of diesel exhaust-gas after-treatment systems will be one of or the most important enabling technologies in this area and should be made a higher priority. The effect of fuels and lubricants on integrated system performance should also be investigated (Perez, 2000). The timelines for most of OHVT's research projects are too short and the cost sharing too great for university participation. Most university facilities have advanced instrumentation and computational capabilities but do not have state-of-the-art engine technologies. Also, the process of educating students during a research program usually results in slower progress. Therefore, universities are better suited to conducting long-term, fundamental research. If more of OHVT's program were focused on an eight to ten-year time horizon, universities would have more opportunities to participate. Advanced Engine Mechanisms For reciprocating engines, the crank-connecting, rod-piston mechanism has been, and currently is, the mechanism of choice, together with ports and/or cam-operated valves. It is well known from thermodynamic analysis that the compression ratio built into this mechanism can exert a strong influence on engine efficiency. In the diesel engine, the compression ratio is set high enough to promote compression ignition. In the spark-ignition engine, on the other hand, the abnormal combustion phenomenon of autoignition necessitates choosing a lower compression ratio. Because autoignition occurs primarily at high engine loads, variable-geometry demonstration engines have been built that allow the compression ratio to be increased at part throttle for better efficiency, then decreased at high loads to avoid abnormal combustion. Just such an engine, with an anticipated time frame of 2005, was recently announced by Saab (Crosse, 2000). At light load, the engine runs normally aspirated at high efficiency, with a compression ratio of 14. As the throttle is opened, the compression ratio decreases continuously to a minimum of 8 at full load. At this condition, the engine is highly supercharged by an engine-driven, positive-displacement compressor and intercooled. Primarily because of this supercharging, Saab claims that this 1.6-liter engine has the output of a 3-liter conventional engine. If this innovative Saab engine proves to be production viable, it should narrow the efficiency gap between the spark-ignition and compression-ignition engines. If the diesel engine cannot meet future emissions standards, a supercharged variable-compression-ratio engine might be an interesting alternative for SUVs or light-duty trucks. The ability to vary the compression ratio might also prove advantageous to the diesel engine for control of emissions or of peak cylinder pressure, or for improved cold starting. International Truck and Engine Company recently issued a press release announcing a camless-diesel engine technology, in which the valves are hydraulically operated (Brooke, 2000; Navistar, 2000). The combination of electronically actuated and hydraulically controlled cams used in conjunction with computer-controlled, exhaust gas recirculation (EGR) and turbocharging, represents a transition to a “command-controlled ” air-induction system. International
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program claims that “NOx emissions will be reduced by up to 70 percent, with significant gains in fuel economy. Particulate emissions are claimed to be reduced to 90 percent below the EPA's proposed 2010 diesel regulations” (Brooke, 2000). Command control provides the capability of optimally configuring the engine, for both fuel economy and emissions, for each load and speed condition. This capability is of little value for an engine operating at fixed conditions but could significantly improve both fuel economy and emissions in an engine that operates in a range of conditions. If this technology is perfected, it could minimize engine-out emissions, which in turn would minimize, or possibly eliminate, the reduction requirements of an after-treatment system. Command control would also allow engine operation to be tailored to enhance exhaust-gas after-treatment performance (i.e., promote catalyst light-off or particulate-trap regeneration). Recently, Flynn et al. (2000) hypothesized that it may not be possible with current diesel engine technology and fuels to meet the 2007 emission standards via in-cylinder emission reduction alone. If this conclusion is correct, exhaust-gas after-treatment systems will be necessary and will become an integral part of the diesel engine power train. OHVT also recognizes this eventuality and has included exhaust-gas after-treatment systems, as well as in-cylinder emission reduction technologies, as a major R&D area. For contractual reasons, the committee was not informed of all of the details of the engines used in OHVT's programs. Consequently, the committee cannot comment on OHVT's work on advanced engine mechanisms. According to the announcements by Saab and International described above, new technologies have the potential for minimizing or eliminating the need for after-treatment. OHVT should immediately review these advances in advanced engine mechanisms and assess their implications for OHVT's research programs. Findings and Recommendations Finding. Engine-related programs cosponsored by the Office of Heavy Vehicle Technologies and industry from 1997 to date have encouraged industry and government together to solve important environmental problems and have produced useful results. Recommendation. The cooperative government-industry approach being pursued by the Office of Heavy Vehicle Technologies should be continued with the addition of periodic (at least annual) reviews and updates of research on key enabling technologies. Finding. Continual assessments of past achievements, the appropriateness of stated goals and projects, and the need for new approaches and goals are necessary for coordinating long-term research. It is not clear to the committee that OHVT is following this process. An eight-year time delay from the initiation of research to the introduction of a product has been documented by the Office of Heavy Vehicle Technologies. Three of the eight years have passed since the presentation of the 1997 technology road map. The committee was disappointed that more reassessments and adjustments had not been made since the initiation of the program. Recommendation. The Office of Heavy Vehicle Technologies should put in place a process by which it can gradually revise its mix of programs and periodically (at least annually) review and update its programs and goals to reflect a time horizon of eight years or more. Finding. Projects selected encompass a broad range of research areas rather than focusing on critical technologies. Given available resources, a smaller number of carefully chosen projects would be more productive. Recommendation. The Office of Heavy Vehicle Technologies should carefully identify the most critical problem(s), such as emissions control, and concentrate its resources on research that will provide long-term solutions to these critical problems. Finding. A significant portion of the program ($18 million in FY00) is focused on Class 1 and Class 2 light-duty vehicle engines through proprietary 50/50 cost-share projects with industry. Although the committee could not determine if funding was being used for that purpose, there was some indication that one of the companies in the program is working on technologies that might be incorporated into hardware components for a Class 1 or Class 2 light-duty engine. The committee supports the promotion of industry research on promising, yet high risk, approaches to configuring engine-emission control systems. The committee does not endorse the use of government funding to support specific engine or component development programs by industry. Recommendation. The committee believes it appropriate for the Office of Heavy Vehicle Technologies (OHVT) programs to provide basic technical information to promote the development of more fuel-efficient engine-emission systems by the private sector for the light-truck and sport utility vehicle market. OHVT should evaluate the effectiveness of its 50/50 cost-share agreements with industry based on the extent to which each program is creating this basic information. OHVT should not support any cooperative agreement to develop a specific engine or component. Heavy Vehicle Systems The objective of the OHVT program is to increase fuel efficiency and reduce emissions, while maintaining and improving operational safety. OHVT's methodology is to analyze and optimize a heavy vehicle as a totally integrated system. The fuel economy goal for Classes 7 and 8 trucks is
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program 10 mpg while meeting prevailing emission standards. A complete systems view of the total vehicle system includes engine systems technology, fuels, and a general category called systems technology, which includes the rest of the vehicle. The components of the heavy vehicle systems technology are: aerodynamic drag, auxiliary systems, rolling resistance, friction and wear, thermal management, high-strength, weight-reduction materials, and a category called others. These programs are addressed in this section. Overall Systems View As far as the committee could determine, OHVT has not conducted a total systems analysis except to generate a list of categories. Based on discussions with some investigators in the systems technology program, the committee believes that the lack of a total systems approach will result in the program failing to achieve its goal of a 10-mpg truck (McCallen, 2000; Englar, 2000a). The subareas in the systems technology program are not well coordinated with OHVT's overall goals, which increases the likelihood that the program goals for heavy-duty trucks will not be reached. Given the significant impact of reduced power requirements, both in terms of economics and fuel consumption, the percentage of the budget devoted to reducing power requirements should be very large and R&D on vehicle systems should be continued past the stated ending date of 2001 (DOE, 2000a). Fortunately, much of the R&D is still in the planning stage and can still be reconsidered. If possible, the changes should be made without seriously disrupting the individual parts of the program. To this end, OHVT might consider giving a private contractor the responsibility of integrating the total systems approach. The integrated programs should meet OHVT's specific requirements for coalition building, and the national laboratories should be an on-call resource. Finding. Because the heavy vehicle systems R&D element of the OHVT program is not well coordinated, the results will have little chance of contributing to the trucking industry in a timely fashion. Recommendation. The present program of loosely coordinated projects should be replaced with a focused, results-oriented task structure and clearly stated goals for each project. Funding should then be allocated according to the potential for gains in fuel economy within the constraints of emission standards. In addition, the program should be extended well beyond 2001. Multiyear Program Plan for the Aerodynamic Drag Program The current plan for R&D on reducing aerodynamic drag has a three-tier, temporal structure: a plan with long-term benefits, a plan with midterm benefits, and a plan with short-term benefits. All of these are separate projects. The overall goal is to reduce drag by 15 to 25 percent (Diamond, 2000). The long-term projects are centered at the national laboratories and focused on advancing the technology of computational fluid dynamics (CFD) in the area of drag prediction for Class 8 trucks. The research team includes investigators from LLNL, SNL, National Aeronautics and Space Administration (NASA), the University of Southern California, and the California Institute of Technology. Three different computational methods are being developed and validated experimentally. Although the projects are focused on a fundamental understanding of the flow physics, researchers have also been meeting with industry representatives to solicit their support and determine their expectations. The midterm program includes one project with Georgia Technical Research Institute (GTRI) on pneumatic aerodynamics (pressurized air blowing) that uses jets of air to control and augment or reduce the aerodynamic forces and moments on the vehicle (Englar, 2000a). This technology, which was developed for short takeoff and landing aircraft, is expected to be efficient and mechanically simple. The short-term program, which is focused on applying known technology to current production vehicles, consists of one consultant employed at a firm called Dynacs. Some progress has been made. For example, an existing truck with a deflector mounted on the cab was not reducing drag as planned, but was actually increasing drag. The consultant was able to identify the cause as a slight (10 to 11 inch) increase in space between the cab and the following trailer and to expedite the improvement. OHVT has identified reduction in aerodynamic drag as a key element in reducing overall fuel consumption. In fact, it may be the single most important factor for trucks that spend most of their time on interstate highways (see Figure 2-2). However, OHVT's overall level of effort in aerodynamics does not reflect this importance, and is being done largely without industry involvement. By contrast, work on engine-related activities is being done with direct involvement of the engine manufacturers. In fact, the program is heavily weighted toward the development of CFD models. The CFD project does include wind-tunnel tests, but they must be refined to represent the full complexity of a truck. Therefore, the value of the wind tunnel models will be to verify the CFD models, which may be computationally challenging but will not provide guidance to real-world truck designers. Improving the technology of CFD for drag predictions is a worthwhile goal and should be continued, but the goal of a 10-mpg truck will not be met unless applications are developed for a tractor-trailer vehicle. OHVT is funding CFD development at seven research locations with a combined FY00 budget of $992,000. All of the CFD approaches being investigated appear to be completely independent of one another, except for the exchange of information among project participants, and no
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program decision point is planned for choosing among them (e.g., a Go/No Go decision framework); at that point some of them would be discontinued and efforts would be concentrated on the most successful codes to ensure that they would be user friendly and usable to the trucking industry. A new technology being funded by DOE through OHVT is being investigated at GTRI by staff from the former Lockheed aerodynamic group using a wind tunnel, which was donated to the Georgia Institute of Technology by Lockheed. Aerodynamicists at GTRI have developed and applied surface blowing and suction techniques (called pneumatic technology) to short takeoff and landing aircraft have proposed using this technology to reduce the drag of the nonstreamlined shapes of trucks. They also suggest that they can provide lift to reduce the weight on the wheels. A quick bounding calculation suggests that this effect is likely to be less than 5 percent of vehicle mass. Nevertheless, aerodynamic lift could conceivably reduce drag, rolling resistance, and damage to highways. The highly nonlinear effect of weight on highway damage might provide a significant advantage (AASHTO, 1994). The aerodynamic lift technology can reportedly be controlled very quickly for optimal operation in a dynamic process, such as braking. A more complete integration of total truck systems would help investigators at GTRI determine better ways of integrating their technology developments into the truck as a whole (i.e., the impact on the engine, exhaust emissions, and the operating modes of an engine in a truck environment) (Englar, 2000b). GTRI is planning a demonstration of this technology on an actual truck, which might further the transfer of this new technology to the heavy truck industry, in which manufacturers are primarily assemblers. Aerodynamic improvements will require much closer collaboration between vehicle designers, wind tunnel experiments, and computational modelers. The many complexities (e.g., spinning wheels, cooling system airflow, flow into and out of the underhood area, exposed frame rails and cross members) will have to be taken into account by the computational analysts and their importance determined in the aerodynamic drag of a truck. Wind tunnel tests using detailed models can assist in the development of models and in the empirical design of truck shapes. The high cost of computers able to handle the computational codes will necessitate close cooperation between the trucking industry and the national laboratories. However, the massive parallel computational capabilities available at the national laboratories are being used to develop CFD codes. The committee believes OHVT (and DOE) should develop a plan to make these capabilities, which will not be affordable for many years, available to the truck manufacturing industry. Finding. The development of different computational fluid dynamics (CFD) codes are proceeding independently of one another. No plan has been developed to coordinate these activities to provide useful results for the trucking industry. Recommendation. A decision point should be defined at which time the most suitable single methodology of computational fluid dynamics (CFD) technologies should be selected for further support. A significant effort should be made to ensure that the final CFD model is user friendly. Finding. The program on pneumatic technology in the Office of Vehicle Technologies plan may be useful in the near term for the aerodynamic design of vehicles and may warrant expansion. Recommendation. The Office of Vehicle Technologies (OHVT) should study the benefits and costs associated with pneumatic technology and, if the results are favorable, should provide enough funding to thoroughly investigate this, including the impact of providing compressor power. Experimentally oriented programs should take an integrated approach to flows outside the truck and under the hood, including the integration of the engine compartment, underbody flows, and flows around the wheels. OHVT should also ensure that pneumatic technology, rotating tires, and underhood flows are included in the capabilities included in the development and benchmarking of the computational fluid dynamics model. Studies should focus on aerodynamic design, as well as the safety of vehicles equipped with pneumatic technology. Finding. The benefits of computational fluid dynamics design methods will not be immediately useful to the trucking manufacturing industry unless the industry has access to the leading-edge computational power necessary to apply them. Recommendation. The Office of Heavy Vehicle Technologies should provide industry with some means of access to the high-scale, massively parallel computers at the national laboratories until this level of computational power becomes affordable to industry and the value of the new computational fluid dynamics models have been demonstrated. Rolling Resistance The targeted goal of this program is to reduce rolling resistance by 8 to 10 percent through a multiyear plan for energy efficiency in heavy-duty vehicle tires, drive trains, and braking systems (DOE, 2000a; Blau, 2000). The preferred mechanism for reducing rolling resistance is the use of super single tires, which have been commercially available for more than a decade but have not been widely used for commercial trucks. The super single tire is both larger in diameter and wider than the most common tires used on Class 8 trucks. It also operates at higher pressure and requires a wider wheel rim. A super single tire of this configuration would be used in place of a pair of conventional truck tires. Super single tires have not been widely adopted for many
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program reasons, including concerns about safety, stability, and loss of cargo volume. Another concern is the possible acceleration of road damage. OHVT plans to work with the U.S. Department of Transportation and the American Trucking Association to explore the issues surrounding the use of super single tires. OHVT also plans to conduct tests to compare road damage from dual and single tires. OHVT plans to develop and maintain a tire-material database and to develop software for modeling tire materials and instrumentation systems for sensing real-time tire condition and misalignments. Unfortunately, the national laboratories do not have much expertise in tire technology, which is highly competitive and proprietary. For most trucks, the larger diameter of the super single tire is a sufficient reason for not using it. The larger diameter can be accommodated only by raising the bed of the truck or trailer. Since the overall height, width, and length of trailers is set by regulation, and since most Class 8 trailers are built to the regulated limits, raising the truck bed would reduce the cargo space. In a van trailer that hauls volume-limited (as opposed to weight-limited) loads, the productivity of the truck is directly proportional to cargo volume. Furthermore, the height of loading docks has been standardized at the height of current truck beds. For these reasons, even if all other problems were solved, low-height trucks, such as tankers, are the only trucks likely to adopt super singles. OHVT has no plan to encourage tire manufacturers to develop a better alternative. A competition could be held, for example, to develop an acceptable tire with reduced rolling resistance that meets the need for wet and dry road grip, tread wear, ride, noise, aging, cost, robustness against road hazards, and protection of the highways against road damage. The new tire would be much more acceptable and would benefit the nation sooner if it could be retrofitted to today's fleet. The truck operators, who will play a major role in deciding whether to purchase the new technology, should also play a major role in the evaluation of new tires. Designing heavy-duty trucks for increased fuel efficiency must take into account vehicle interactions with roads and bridges. The weight of trucks is a major factor in the design life of roads. Damage to a road from a single fully loaded Class 8 truck is equivalent to the damage from about 5,000 cars (AASHTO, 1994). A 10-percent increase in truck weight would increase the damage rate by about 50 percent. As one would expect, the damage rate depends on tire configuration. Therefore, changing to high-pressure tires or to any other new tire configuration will have to be thoroughly evaluated to determine the effect on roads. The American Association of State Highway and Transportation Officials (AASHTO), which has existing databases and has developed the current models of road damage, should be included in the team that evaluates road damage. Finding. Expertise in tire technology is mainly in the private sector. Recommendation. The Office of Heavy Vehicle Technologies (OHVT) should consider restructuring its research on rolling resistance to encourage the development of superior tires by the tire industry. Finding. Approaches to decreasing rolling resistance could have significant impacts on highway infrastructure. Recommendation. The Office of Heavy Vehicle Technologies should devote more resources to evaluating the impacts of new tire designs on highways. Reducing Friction and Wear in Heavy Vehicles The plan for reducing friction and wear is almost totally focused on materials-related issues, including: (1) surface-modification technologies; (2) chemistry of lubricants and additives; (3) failure mechanisms; (4) advanced computer codes; (5) predictive bench-top tests; and (6) other issues. The target is a 15-percent reduction in losses caused by friction in the drive train and the engine (Fessler and Fenske, 1999). Wear is closely related to the breakdown of lubricant film, surface hardness, material compatibility, and oil contamination, rather than engine friction. In modern truck engines, wear is not a problem unless the lubrication system (including the regulation of lubricant temperature) operates improperly or improper lubricants and/or change intervals are used. Therefore, OHVT seems to place too much emphasis on the problem of wear in the engine. Friction reduction is another area in which OHVT's emphasis on materials research is excessive, at least for the engine. In the program plan, power consumption in engines is said to relate to material-based properties, but many sources in the open literature contradict this (Assanis, 1999). In fact, the figure in the plan showing the breakdown of mechanical friction does not represent a typical heavy-duty engine (Fessler and Fenske, 1999, p. 12), and many other questions could be raised about its validity. The data seems to be either from a very atypical engine or simply inaccurate. Finding. The present friction and wear program is concentrated too heavily on materials research and not enough on practical techniques for reducing friction and constraints on those techniques. For example, a change that lowers friction but sacrifices oil control may have an unacceptable effect on emissions. Recommendation. Research on reducing friction in the engine should be incorporated into the engine program. Funding for research on wear in the engine should be cut back. Under-Hood Thermal Management The OHVT Technology Roadmap (DOE, 2000a) specifically states:
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program Aerodynamic designs offer new challenges in designing the under-hood systems and components of trucks. Optimal location and shape of components (e.g., engine, fans, radiators, heat exchanges, intake manifolds) have to be determined. Advanced high-efficiency trucks require optimization of the thermal performance of the power system and a well-characterized under-hood thermal environment to ensure that electronic control systems and other temperature-sensitive components operate properly. This complicated systems analysis requires the integration of high-fidelity models of thermal-hydraulic processes that stretch the state-of-the-art in CFD and high-performance computing. The computational model should integrate thermal models for convective, conductive, and radiative heat transport as well as integrate models for critical heat management system components, including cooling fans and radiators. A workshop report and multiyear program plan were recently developed (DOE, 2000b). In the committee's opinion, the under-hood thermal management program seems to be well structured but, as discussed below, is not integrated with the aerodynamics program. The under-hood program is also underfunded. The quotation above reflects OHVT's approach to under-hood design. The emphasis is on computation alone, rather than on computation for design. No mention is made of the crucial integration of under-hood thermal management and external aerodynamics. Some of the biggest reductions in drag in piston-engine aircraft and automobiles have resulted from an integrated approach to internal and external aerodynamics. In fact, an integrated approach was recommended in a workshop sponsored by the program, but it was not included in the program plan, and principal investigators told the committee they have no plans for integration (McCallen, 2000; Englar, 2000b). The simulation of the thermal management system is currently of very great interest in heavy-duty truck design because the size, cost, and power requirements for the cooling system are expected to increase substantially with the new emission control levels. EGR and retarded fuel-injection timing, two of the most common techniques used to reduce emissions of NOx, are both expected to increase heat rejection. Therefore, an integrated system design will be the most effective and economical approach, and simulations will be the best way to evaluate trade-offs. Eventually, designs will have to be verified in demonstration vehicles to convince the trucking industry of their performance. Simulations of vehicle design with the CFD code CHAD (computational hydrodynamics for advanced designs) may not be practical because it requires very long run times. This deficiency was revealed during a review of the under-hood thermal-management program at ANL (Domanus and Caufield, 1999). Mathematicians at ANL have identified ways of speeding up the CHAD code by two orders of magnitude. If ANL is allowed to develop these changes, all of the programs that use CHAD would benefit. R&D on controlling nucleate boiling and R&D on nanofluids are both concentrated on improvements in liquid-side heat transfer, whereas under-hood aerodynamics will affect air-side heat transfer. The committee feels that a clear distinction should be made between these two classes of technologies and that the program 's focus should be largely on air-side heat transfer, which is the most common limiting mechanism on liquid-to-air systems and is expected to be the principal contributor to aerodynamic drag in the cooling system and auxiliary power consumption by the cooling system. Nevertheless, corrosion and fouling for liquid-side heat transfer, as well as liquid-side cooling in critical regions, such as between the fuel injector and the exhaust valve, are also important and should still be supported by OHVT. Finding. Under-hood thermal management and overall vehicle drag are closely related and should be considered together in mathematical models if practical design methods are to be developed. Recommendation. The under-hood thermal management program should explore integrating the vehicle-drag simulation and the thermal-management simulation so that a total system can be simulated. The program should use newly developed tools to proceed with a sample design that includes drag reduction, adequate cooling, and low power consumption. The design should then be validated in a demonstration vehicle. Finding. The computation time for real problems using the CHAD (computational hydrodynamics for advanced design) computer code is so long that it all but precludes its use in design practice. Recommendation. Efforts should be made to reduce the running time for the CHAD (computational hydrodynamics for advanced design) code. Finding. The program on under-hood thermal management includes a wide range of investigations, from comprehensive under-hood models to techniques for investigating solid-to-liquid and solid-to-air heat transfers. The most significant improvements in thermal systems are expected to be provided by improved solid-to-air heat transfer. Recommendation. The Office of Heavy Vehicle Technologies (OHVT) should ensure that all activities that would enhance and control air-side heat transfer are adequately funded before considering funding for projects on liquid-side heat transfer (other than corrosion and fouling). Auxiliaries and Other Energy-Saving Projects OHVT includes the cab comfort-control system and the regenerative shock absorber in the category of auxiliaries and other energy-saving projects. Only R&D on the regenerative shock absorbers is funded for FY00 (a high-risk project about which the committee was provided very little
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program information). The cab comfort system is addressed by the use of an auxiliary power unit that could reduce the need for idling the engine during long overnight truck stops and a plan to inform truck operators of the potential energy savings of reducing long idle operations. OHVT's goal of a 10-mpg truck postulates very significant reductions in power requirements for auxiliaries. The rationale for a small auxiliary power unit is that it would use less energy and produce fewer emissions than the complete truck engine operating at idle speed and very low load. Even though an auxiliary power unit can probably be developed to meet this expectation, the improvement might be small because of the adverse effects of scaling internal combustion engines to low power levels. OHVT does not have any funded programs in auxiliary power for FY00. Other potential energy-saving technologies are not included in the program, although the OHVT Technology Roadmap projects a large saving in power consumed by auxiliaries. For example, most engine auxiliaries are designed for a particular worst-case condition. If the engine drives the auxiliary power unit by a constant-ratio mechanical drive, its power consumption can be excessive. Alternative auxiliary drives can save substantial energy by matching the performance to the needs of the engine. Consider, for example, the lubricating oil pump on a truck engine, which is designed with excess capacity to meet the worst-case condition of engine operation at very high speeds when oil pressure must be high enough to fill all of the oil supply passages at a positive pressure at all times to prevent rapid engine failure. Engine failure is most likely when the vehicle is operating in overspeed conditions, such as descending a grade through one of the lower gears. Therefore, the lubricating pump is designed to provide more oil than necessary, even in this extreme condition. An additional margin is included to meet the increased flow requirements of worn crankshaft bearings and the decreased capacity of aging pumps. For many other operating conditions, however, very little oil flow and pressure are required. The lubrication supply system consists of an engine-driven gear pump and a pressure-relief bypass valve. Because the pump system is designed with extra capacity, the pressure-relief valve is partially open during most engine operations. The flow of oil across the pressure drop of the relief valve constitutes a direct energy loss that must be compensated for by increased input to the pump shaft. Because the pump is not 100 percent efficient, the input power must be greater than the loss in the relief valve. The net loss can be several kilowatts. If the oil supply pressure could be modulated in response to engine operating condition, a substantial portion of the power used to circulate oil through the engine could be saved. Several options are currently used to increase the efficiency of engine auxiliaries. The trend in the automobile industry is to use electric drive for engine accessories. Even though the efficiency penalties of converting shaft power to electricity and back again are considerable, the benefits of tailoring the power supply to the requirements of the moment result in a net gain in efficiency. In the future, automobiles will have 42-V electrical systems, which will improve the efficiency of generators and motors; heavy-duty trucks are also expected to benefit from 42-V systems. Other options for increasing the efficiency of engine auxiliaries include mechanical variable-speed drive and variable-geometry pumps and fans. Water pumps, radiator fans, and power steering pumps could all be made more efficient, either by electric drive or by other means. If electronic controls and sensors are used to optimize power use, these accessories could also contribute to better fuel economy. Finding. Advances in the efficiency of engine auxiliaries and other onboard systems that require power will be important for the development of a 10-mpg truck. OHVT has no program to quantify and demonstrate the full range of advanced technologies. Recommendation. The Office of Heavy Vehicle Technologies (OHVT) should consider and evaluate the potential energy savings in engine auxiliaries and other system power loads with technologies not currently in the program. Depending on the results of the analysis, OHVT should then consider expanding its development activities in auxiliaries and accessories with low energy consumption. Hybrid Systems The goal of the Heavy Vehicle Propulsion Hybrid R&D Program is to develop and demonstrate, by 2004, commercially viable vehicles that achieve at least double the fuel economy of comparable 1999 vehicles in an urban driving cycle and, as a research goal, to decrease criteria pollutant emissions to at least 30 percent below EPA standards prevailing in 2004. The focus is on urban trucks and buses with hybrid-electric power trains, with special emphasis on configurations with natural-gas engines. OHVT plans to work with competitively selected industry teams that include hybrid system developers and vehicle manufacturers (Wares and O'Kain, 2000). In response to a solicitation for heavy-vehicle hybrid propulsion systems on September 24, 1999, OHVT received several proposals. The winners were announced on March 3, 2000 (Wares and O'Kain, 2000). OHVT representatives indicated that industry response to the solicitation was excellent and that a variety of vehicle hybrid propulsion system designs and vehicle applications were received. The three teams selected are: NovaBus/Lockheed Martin; Electrocore/GM Allison; and A.D. Little/Freightliner/ISE Research/DDC/University of California, Davis. Unfortunately, details of the proposals were not provided to the committee for review. Consequently, the following comments and recommendations are based on committee members' knowledge of the field.
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program HEV passenger cars have recently been introduced into the marketplace. An HEV uses a power-augmenting electric motor and associated energy storage device (e.g., a battery) to reduce the rated power requirement of the primary power plant (e.g., a diesel engine). Passenger-car HEVs achieve better urban fuel economy than conventional passenger cars for three reasons: more efficient operation of the engine; engine shutoff; and regenerative braking. First, conventional passenger cars characteristically have high power-to-weight ratios to provide the acceleration performance and hill-climbing ability demanded by American drivers. The high ratio forces the engine to operate much of the time at light loads, at which friction and throttling losses markedly decrease the efficiency of the traditional spark-ignition engine. Because the smaller HEV engine is forced to operate at higher loads, its efficiency is improved. Second, in most HEVs, fuel flow to the engine can be halted during braking and idling. Third, the electric motor operates as a generator during braking. Therefore, part of the kinetic energy invested in the moving vehicle can be recovered and stored in the battery for reuse on demand. This type of generator is sometimes called a regenerative retarder, and recovery of energy during braking is called regenerative braking. The additional weight of the HEV electrical system generally exceeds the weight saved by the smaller engine. The resulting increase in net weight offsets some of the fuel savings expected from an HEV. The trade-off is influenced by the driving schedule and must be evaluated analytically prior to hardware commitment. A driving schedule featuring frequent starts and stops, such as for urban delivery vans or buses, is conducive to fuel-economy gains in an HEV with regenerative braking. However, in fast decelerations from high speeds, as might occur for on-highway trucks, much of the available braking energy may have to be sacrificed because of limitations on the battery charging rate. If the decelerations are consistently from low road speeds, regenerative braking will probably be less effective because of poor generator efficiency at low speeds. More information on regenerative braking may soon be available through a planned DOE program on regenerative retarders (Blau, 2000). Vehicle systems simulations can determine the potential fuel economy and emissions benefits of HEVs. Power electronics are an essential element of HEVs. Normally, the motor/generator is an alternating-current machine, but the battery storing the electricity is a direct-current device. The power electronics must convert the current between the two devices efficiently and with precision control. The battery storage is a critical component of an HEV drive train. As a battery accumulates service time, its performance deteriorates until eventually it must be replaced. The characteristics of an HEV may, therefore, depend on battery age. Other problems are also related to electrochemical storage batteries. The performance of some batteries is drastically reduced at subfreezing temperatures. Some cannot be fully charged at high ambient temperatures. Some cannot be quickly charged, which may be essential for regenerative braking. Some have unresolved safety concerns. Meeting emission standards will be critical to the success of improved vehicle technologies, including hybrid vehicles. Even demonstrating an emissions reduction of 30 percent below the 2004 EPA standards in a production prototype by 2004 may be insufficient. Given the lead time required by industry to progress from a prototype to actual production, an appropriate emissions target would be meeting the standards for 2007, which are more than 30 percent below the 2004 standards. OHVT has been working with its stakeholders and industry to develop road maps and carry out technology development. As noted above, a number of teams have been formed, and vehicle projects have been selected for heavy-vehicle hybrids. None of these teams includes the customer, however, who is the ultimate user of the vehicle. Vehicle manufacturers can offer HEVs in the marketplace, but if they do not have the qualities desired by the owner/operator, they will have no chance of making a significant market penetration. Natural gas should be compared to diesel fuel in a broad context of the entire fuel cycle (see Fuels Utilization section). In terms of energy conservation and the production of greenhouse gases, as well as cost and domestic availability, processes ranging from fuel recovery to delivery, energy costs of compressing natural gas to make compressed natural gas (CNG) and the liquefication of natural gas to make liquefied natural gas (LNG), as well as onboard storage, will have to be considered. Finding. Computer simulations of vehicle systems will be necessary to identify the potential fuel economy and emissions of hybrid electric vehicles. Recommendation. If it has not already done so, the Office of Heavy Vehicle Technologies should evaluate the candidate hybrid electric vehicles by computer simulation. For the simulations to be meaningful, the specific driving schedule on which the gain in fuel economy is assessed must be defined. Finding. Acceptance by the ultimate end-user or owner of the vehicle will be critical to ensure significant market penetration of heavy-duty hybrid vehicles. Recommendation. The Office of Heavy Vehicle Technologies should ensure that the customer (i.e., the anticipated user/owner of the vehicle) is consulted as the program progresses. The customer may also have useful insights for planning future programs. FUELS UTILIZATION OHVT's fuels program currently focuses on two fuels: low-sulfur diesel and natural gas. The fuels utilization R&D
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program budget was about $14.6 million in FY00, or about 21 percent of the OHVT budget. Programs on Fischer-Tropsch liquids, oxygenates, and biodiesel have essentially been completed. The committee believes that the current focus is appropriate. Continued monitoring of R &D on oxygenates outside of the program may be useful to determine if new opportunities develop. OHVT is focusing on the current range of interest for sulfur concentration (5 to 50 ppm). Low-sulfur fuel is necessary to minimize both particulate emissions and minimize the deleterious effects of sulfur oxides produced in the engine that reduce the efficiency of the after-treatment systems. One candidate after-treatment system uses an NOx trap, which can be poisoned by sulfur oxides. Another, less sulfur-sensitive system, uses an additive (e.g., urea) to reduce NOx to nitrogen. The engine builders have suggested a sulfur limit of 5 ppm primarily to protect the catalyst in the NOx trap (Thoss, 2000). The petroleum industry has recommended that sulfur specifications in diesel fuel be lowered to an average of 30 ppm, with a maximum of 50 ppm, arguing that sulfur limits lower than that would be very costly and could cause fuel shortages (Cavaney, 2000). EPA has proposed a standard of 15 ppm. Research on a variety of after-treatment technologies using fuels with a range of sulfur concentrations will be necessary to determine which technology will meet the emission standards at minimal cost to the consumer for the fuel-vehicle system. Determining the size distribution and chemical character/ toxicity of particulates in the exhaust gas from the after-treatment system will also be necessary because of concerns about diesel particulates as TACs. Natural Gas The Alternative Fuels Program supports the development of a viable heavy-duty, vehicular, natural-gas engine. Such engines are already being marketed for urban transit vehicles and school buses. Natural gas is the preferred fuel because its engine-out emissions are lower than with diesel fuel. However, to meet the new emission standards, after-treatment will be necessary. Vehicles with heavy-duty, natural-gas engines are frequently purchased through government agencies rather than by private companies, often encouraged through legislation and/or financial incentives such as subsidies and tax relief. In the long term, however, natural-gas vehicles (NGVs) will have to be cost competitive with diesel vehicles, except in special circumstances, such as urban use where low emissions and other environmental benefits may be more important than cost. Specific goals of the OHVT Natural Gas Vehicle Program include demonstrating two hybrid NGVs by 2004 that are competitive in cost and performance with their diesel-engine counterparts. One will be a Class 3 to 6 vehicle operating on CNG; the other will be a Class 7 to 8 vehicle operating on LNG. OHVT has identified four technology barriers to broad acceptance of NGVs. The first is inferior engine efficiency. Three types of natural-gas engines have been proposed: the spark-ignited natural gas engine (SING), the pilot-injection natural gas engine (PING), and the direct-injection natural gas engine (DING). The SING, which normally uses an inducted, premixed, near-stoichiometric charge of fuel and air, is limited to a compression ratio lower than that of the diesel engine because of combustion knock, despite the high octane rating of natural gas. Consequently, even though its efficiency will exceed that of a spark-ignited gasoline engine, the SING is not likely to match the efficiency of the diesel engine. The compression ratio of the PING, which employs compression ignition of a pilot injection of diesel fuel to initiate combustion of the natural gas, does not have the same limitation. The DING, which injects natural gas directly into the cylinder and uses glow-plug-assisted ignition, is even less likely to experience combustion knock. A second technology barrier to natural-gas engines is the size and weight of onboard fuel storage containers. At the commonly used pressure of 250 atm, CNG occupies about four times as much space as diesel fuel. High pressures dictate long, cylindrical, thick-walled storage tanks that are often difficult to package in a vehicle. Moreover, the tanks are heavy and expensive. LNG consumes only about two-thirds more space than diesel fuel with the same energy content. However, LNG is a cryogen, having a temperature of about –150°C. Therefore, LNG must be stored in a bulky vacuum-jacketed tank. As the tank is warmed by the environment, gas must be vented to avoid the buildup of pressure. For safety reasons, this would discourage the use of LNG in vehicles that are either serviced or parked in enclosed buildings. OHVT is investigating a storage system involving the adsorption of natural gas onto carbon fibers in a tank pressurized to 34 atm. Because heat is generated during fast charging of the tank, it would require cooling. An electric heater would be used to drive gas from the tank. Although adsorption storage of natural gas is not a new technology, the potential of this particular system has not yet been thoroughly defined. A third technology barrier is the limited availability of fueling stations. In 1998, there were 5,318 CNG fueling sites and 486 LNG fueling sites (70 percent of them in California) in the United States (Davis, 1999). By comparison, there were between 150,000 and 200,000 gasoline stations. Thirty-five states had only one or no LNG sites. In 1999, federal, state, and local governments operated 45 percent of the heavy-duty CNG vehicles and 78 percent of the heavy-duty LNG vehicles (Davis, 1999). A fourth technology barrier is the high cost of a natural-gas fueling station. To provide for fast filling (as opposed to overnight filling, which might be acceptable for a privately owned passenger car and some short-range urban delivery trucks), a CNG service station normally uses a large
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program compressor that pumps natural gas from a modest supply-line pressure up to a pressure exceeding that of the vehicle storage tank. On demand, the gas flows from the station tank to the vehicle tank via the pressure difference. The total energy expended in compressing the station gas is minimized by pumping only part of the gas to maximum station pressure. The remainder is compressed to a series of lower pressure levels and stored in a cascade of intermediate-pressure tanks. A fast-fill cascade can be designed to refuel an NGV in a reasonable period of time. When refueling a series of NGVs, however, enough time must elapse between vehicles so that the station compressor can refill the cascade. LNG is transferred to the vehicle tank by a liquid pump. Pumping LNG as a cryogenic liquid consumes less energy than compressing it as a gas to CNG storage pressures. However, liquefying the fuel consumes much more energy than compressing CNG. Finding. The low-sulfur fuel program is appropriately focused on 5 to 50 ppm, the range of current interest. The program approaches the fuel, engine, and after-treatment as an integrated system. The oil industry, the after-treatment industry, and engine builders are all participants in the program. Recommendation. The Office of Heavy Vehicle Technologies should place a higher priority on its low-sulfur fuel program. Finding. It is too late to influence engine designs for 2004. Recommendations. For demonstrations of a Class 3 to 6 vehicle operating on compressed natural gas and a Class 7 to 8 vehicle operating on liquefied natural gas to be meaningful, the vehicles should meet the proposed emissions standards for 2007. Finding. The spark-ignited natural gas (SING) engine is not likely to equal the efficiency of the diesel engine, although it may surpass the efficiency of a spark-ignited gasoline engine. Recommendation. The Office of Heavy Vehicle Technologies should limit its support to the pilot-injection natural-gas engine (PING) and the direct-injection natural gas engine (DING) unless it determines that the spark-ignited natural gas engine (SING) can provide solutions to emissions problems that the other two engines cannot. Support for all three engines is warranted until their performance and emissions characteristics are well understood. Finding. If similar natural-gas vehicles (one using compressed natural gas [CNG] and the other using liquefied natural gas [LNG]) travel the same distance on a kilogram of natural gas, the CNG vehicle will probably be more energy efficient than the LNG vehicle because of the difference in energy requirements for the fuel. Recommendation. Evaluations of energy consumption of natural-gas vehicles should include the energy required to deliver the fuel to the vehicle engine. A “well-to-wheels” analysis should be used for assessing technology options. Finding. Industry is already marketing compressed natural gas (CNG) storage tanks, as well as tanks for cryogenic storage. Hence, unless a new technology that provides significant improvements in performance is identified, there is no need for OHVT to support such developments. OHVT currently supports only minimal research on other advanced storage technologies, such as methane storage with novel adsorbents. Recommendation. The Office of Heavy Vehicle Technologies should conduct more research on novel adsorption storage for the purpose of determining system requirements for charging and discharging the tank, response to engine transients, and the weight, cost, safety, and energy balance of such a system. Finding. Until a sufficient number of natural-gas vehicles are operating commercially in the United States with a consequent demand for natural-gas fuel, new commercial natural-gas stations are not likely to be built, except for use by centrally fueled fleets. Recommendation. Building natural-gas refueling stations should not be a priority for the Office of Heavy Vehicle Technologies at this time. Instead, research should be focused on centrally fueled fleets until natural-gas vehicles have better engine efficiency and marketable onboard energy storage. Finding. The emissions of particulate matter from natural-gas engines have not been well characterized. In light of recent trends in emission regulations, these emissions have become more important. Recommendation. The physical and chemical characteristics of particulate emissions from natural-gas engines should be studied, both with and without after-treatment systems. TRANSPORTATION MATERIALS TECHNOLOGIES The OHVT Technology Roadmap notes that the enabling technology for a new engine component is often the material from which the part can be made (DOE, 2000a). The engines under development will have to operate under more challenging conditions, such as higher temperatures, more hostile environments, and greater stress, than today's engines.
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program In addition, the chassis weight of the vehicles will have to be reduced to meet the fuel economy and emissions goals. Meeting these challenges will require new and different materials that will entail design changes. The importance of materials is reflected in OHVT's budget for R&D in this area: $15.7 million in 1996; $12.5 million in 1997; $13.3 million in 1998; and $15.0 million in 1999. These expenditures represented a substantial portion of the total OHVT budget (from more than 50 percent in 1996 to about 33 percent in 1999). In addition, a significant part of the materials budget ($5.2 million in 1996, $5.5 million in 1999) went to support the High-Temperature Materials Laboratory (HTML) at ORNL. Although OHVT uses this laboratory, HTML is a national facility for materials research with a host of clients, and the portion of its budget directly related to the OHVT program is uncertain. OHVT's materials program is divided into two areas: high-strength, weight-reduction materials and advanced materials for propulsion systems. The goal of the high-strength, weight-reduction program is to reduce the vehicle weight by 35 to 40 percent for Class 1 and 2 vehicles, 25 percent for Class 3 to 6 vehicles, and by 5,000 lbs for Class 7 and 8 vehicles. The goal of the program for advanced materials for propulsion systems is to develop materials to meet the needs of fuel systems, exhaust-gas after-treatment systems, valve trains, and air-handling systems. Weight reduction for all truck classes faces similar challenges, which, in fact, are similar to those faced by the PNGV program, which is focused on midsized automobiles. Lighter weight materials and design changes will result in lower vehicle weights, but lighter materials may cost more, can be more difficult to join, and have limited databases. Materials for propulsion systems must satisfy requirements for increased strength, greater dimensional precision in production, new and quite different materials that can withstand hostile high-temperature environments, and the ability to withstand higher stress environments. The committee was given several presentations and information pieces on R&D programs in materials (see Appendix D). Although the committee was not required to evaluate each program, they appear to be well managed. However, projects are not prioritized based on their importance to the success of the OHVT program as a whole and their likelihood of success. Considering the myriad of problems and opportunities in materials R&D, OHVT must develop a process for identifying the most significant materials-related barriers to improved performance and prioritize them according to need. Then, relevant technologies should be evaluated in terms of their probability of success, and the most promising technologies should be selected. Finally, OHVT should establish long-range research programs to address needs that cannot be addressed by current technologies. Unless a disciplined, systematic approach is adopted, almost any materials-related R&D can be justified as being relevant to the OHVT program. OHVT must ensure that the projects it supports are not just relevant but also (1) address a priority need, (2) have a reasonable chance of success, or (3) are long-term research projects that may have high risks but also have potentially high payoffs. Finding. OHVT has no systematic process for prioritizing high-strength, weight-reduction, materials-related research and development (R&D) or for monitoring other relevant, federally funded, materials R&D. Recommendation. A systematic process should be developed and put in place to monitor relevant, federally funded, materials research and development (R &D), to prioritize materials needs, and to identify high-priority opportunities for R&D. This process should use vehicle-systems modeling analyses to set specific goals for vehicle, power train, and chassis weight to meet the overall fuel economy goals. ENVIRONMENT AND HEALTH ISSUES The primary mission of OHVT's research programs is to provide a knowledge base for improved fuel economy and control of engine emissions. Other agencies are focusing on the health and environmental effects of engine emissions. However, researchers studying the production of emissions should also have an appreciation of the health and environmental effects of these emissions. To that end, OHVT has participated in a small way in some health and environmental studies. The committee approves of this participation but only to the extent required to optimize OHVT's research on emission-control techniques. REFERENCES AASHTO (American Association of State Highway and Transportation Officials). 1994. Design Procedures for New Pavements. Publication No. FHWA-HI-94-023 (February). Washington, D.C.: Federal Highway Administration. Assanis, D.N. 1999. An Overview of Engine Friction and Its Effect on Fuel Efficiency. Presented at Research Needs for Reducing Friction and Wear in Transportation, Argonne National Laboratory, Argonne, Illinois, March 22–23, 1999. Blau, P. 2000. Energy Efficiency in Heavy Vehicle Tires, Drivetrains, and Braking System. Draft Multi-Year Program Plan for Running Resistance, Revision 1, January 10, 2000. Washington, D.C.: U.S. Department of Energy, Office of Heavy Vehicle Technologies. Brooke, L. 2000. Navistar camless diesel: 1st to power 2003 Fords. Automotive Industries Today (May). Available on line at: http://www.ai-online.com/articles/may00/0500u4.htm Cavaney, R. 2000. Letter from Red Cavaney, American Petroleum Institute, to Carol Browner, Administrator, Environmental Protection Agency, April 26, 2000. Crosse, J. 2000. SVC. Engine Technology International, Issue 2/00: 27–30. Davis, S.C. 1999. Transportation Energy Data Book. 19th ed. Springfield, Va.: U.S. Department of Commerce, National Technical Information Service .
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Review of the U.S. Department of Energy's Heavy Vehicle Technologies Program Diamond. 2000. Personal communication from Sidney Diamond, Office of Heavy Vehicle Technologies, to William Brown, member of the Committee on Review of DOE's Office of Heavy Vehicle Technologies, June 13, 2000. DOE (U.S. Department of Energy). 1997. OHVT Technology Roadmap. DOE/OSTI-11690 (October). Washington, D.C.: U.S. Department of Energy, Office of Heavy Vehicles Technology. DOE. 2000a. OHVT Technology Roadmap. DOE/OSTI-11690/R (January). Washington, D.C.: U.S. Department of Energy, Office of Heavy Vehicles Technology. DOE. 2000b. Thermal Management for Heavy Vehicles (Class 7–8 Trucks) in Workshop Report and Multiyear Program Plan, Draft, January . Washington, D.C.: U.S. Department of Energy, Office of Heavy Vehicle Technologies. Domanus, H., and T. Canfield. 1999. Personal communication from Henry Domanus, and Thomas Canfield, Argonne National Laboratory, to William Brown, member of the Committee on Review of DOE's Office of Heavy Vehicle Technologies, September 23, 1999. Eberhardt, J. 2000. Origin and Rationale for the DOE Heavy Vehicle Technologies Program . Presentation by J. Eberhardt, director, OHVT, to the Committee on Review of DOE's Office of Heavy Vehicle Technologies, National Academy of Sciences, Washington, D.C., February 16, 2000. Englar, R.J. 2000a. Development of Pneumatic Aerodynamics Devices to Improve the Performance, Economics, and Safety of Heavy Vehicles. SAE 2000-01-2208. Warrendale, Pa.: Society of Automotive Engineers. Englar, R.J. 2000b. Personal communication between R.J. Englar, Georgia Technical Research Institute, and William Brown, member of the Committee on Review of DOE's Office of Heavy Vehicle Technologies, May 22, 2000. Fessler, R.R., and G.R. Fenske. 1999. Multi-Year Program Plan: Reducing Friction and Wear in Heavy Vehicles , December 13. Washington, D.C.: U.S. Department of Energy, Office of Heavy Vehicle Technologies. Flynn, P.F., G.L. Hunter, R.P. Durrett, L.A. Farrell, and W.C. Akinyemi. 2000. Minimum Engine Flame Temperature Impacts on Diesel and Spark-Ignition Engine NOx Production. SAE 2000-01-1177. Warrendale, Pa.: Society of Automotive Engineers. Lehner, C.W. 1999. Design and Development of a Model Based Feedback Controlled Cooling System for Heavy Duty Diesel Truck Applications Using a Vehicle Engine Cooling System Simulation. Master's Thesis, Department of Mechanical Engineering, Michigan Technological University, Houghton, Michigan. McCallen, R. 2000. Personal communication from R. McCallen, Lawrence Livermore National Laboratory, to William Brown, member of the Committee on Review of DOE's Office of Heavy Vehicle Technologies, May 22, 2000. McCallen, R., D. McBude, W. Rutledge, F. Broward, A. Leonard, and J. Ross. 1998. A Multi-Year Program Plan for the Aerodynamic Design of Heavy Vehicles (May). UCRL-PROP-127753 Dr Rev 2. Livermore, Calif.: Lawrence Livermore National Laboratory. Navistar (Navistar International Corporation). 2000. Navistar unveils camless engine technology. Available on line at: http://www.dieselnet.com/news/0004navistar.html NRC (National Research Council). 1987. A Review of the State of the Art and Projected Technology of Low Heat Rejection Engines. Washington, D.C.: National Academy Press. NRC. 1992. Automotive Fuel Economy: How Far Should We Go? Washington, D.C.: National Academy Press. NRC. 2000. Review of the Research Program of the Partnership for a New Generation of Vehicles, Sixth Report. Washington, D.C.: National Academy Press. NSTC (National Science and Technology Council). 1999. National Science and Technology Strategy. Committee on Transportation Research and Development. April 1999. Washington, D.C.: National Science and Technology Council. Perez, J.M. 2000. Exploring Low Emissions Lubricants for Diesel Engines. NREL/SR-570-28521. Washington, D.C.: U.S. Department of Energy, Office of Heavy Vehicle Technologies. Senecal, P.K., and R.D. Reitz. 2000. Simultaneous Reduction of Diesel Engine Emissions and Fuel Consumption Using Genetic Algorithms and Multi-dimensional Spray and Combustion Modeling. SAE 2000-01-1890. Warrendale, Pa: Society of Automotive Engineers. Senecal, P.K., D.T. Montgomery, and R.D. Reitz. 2000. A methodology for engine design using multi-dimensional modeling and genetic algorithms with validation through experiments. International Journal of Engine Research (In press). Thoss, J. 2000. Integrated Emissions Control for Heavy Duty and Light Duty Diesel Engines. Presentation by J. Thoss, chief engineer, Catalytic Systems Division, Johnson Matthey, to the Committee on Review of DOE's Heavy Vehicle Technologies Program, National Academy of Sciences, Washington, D.C., April 26, 2000. Wares, R., and D. O'Kain. 2000. Heavy Vehicles Hybrid Propulsion Systems R&D Program. Presentation by R. Wares, team leader, Heavy Vehicle Hybrid, OHVT, and D.O'Kain, OHVT, to the Committee on Review of DOE's Heavy Vehicle Technologies Program, National Academy of Sciences, Washington, D.C., April 26, 2000.
Representative terms from entire chapter: