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12 CHAPTER 3 Primer on Field Studies This chapter describes the field studies, and how they were downstream from the engine exhaust plane, see Figure 3. At conducted, in chronological order. A tabulation of missions, the 1-m and 10-m (3-ft and 33-ft) sampling locations, multi- dates, locations, operators, airframes, and engines is provided ple probe tips were used to examine the spatial variations of in Appendix A. A list of particle and gas-phase species mea- emissions properties across the exhaust plume. This testing sured is provided in Appendix D. matrix provided engine gas and particle emission informa- tion for more than 400 test conditions. Ambient conditions (during the testing period, the prevailing wind was from the 3.1 APEX1 southwest, but varied from all directions during the experi- The Aircraft Particle Emissions eXperiment (APEX1) was ment period; wind speeds ranged from 0.4 to 14.3 m/sec the first ground-based experiment to simultaneously exam- (1.3 to 46.92 ft/sec); ambient temperature and dew point ine gas and particle emissions from a modern commercial ranged from 16 to 36C (61 to 97F) and from -10 to -2C aircraft over the complete range of engine thrust settings. (14 to 28F), respectively; the wide ranges of ambient condi- APEX1 was conducted at NASA Dryden Flight Research tions impacted the engine operation and therefore the emis- Center (DFRC), Edwards Air Force Base, California, between sions data; some of the apparent variations in the measured April 20-29, 2004. Particle and gas emissions from one of the data have been traced to changes in ambient conditions; NASA DC-8 aircraft's CFM56-2C1 engines were measured as ambient submicron particle concentrations measured at the functions of engine thrust, fuel composition, plume age, testing site were typically <5 g/m3), as well as engine temper- and local ambient conditions. The specific objectives were to atures, fuel flow rates, and fan speeds, were carefully docu- examine the impact of fuel sulfur and aromatic content on mented for each of the test points examined during the non-volatile (soot) and volatile particle formation; follow the experiment. APEX results represent the first and most exten- evolution of particle characteristics and chemical composi- sive set of gas and particle emissions data from an in-service tion within the engine exhaust plume as it cooled and mixed commercial engine wherein multiple instruments were used with background air; examine the spatial variation of particle to quantify important species of interest. properties across the exhaust plume; evaluate new measure- Two different engine testing matrices were used for each fuel ment and sampling techniques for characterizing aircraft used. The NASA test matrix was designed to investigate the particle and gas emissions; and provide a dataset for use in effects of engine operating parameters on particle emissions. studies to model the impact of aircraft emissions on local air It included 11 steady-state engine thrust settings: 4, 5.5, 7, 15, quality. 30, 40, 60, 65, 70, 85, and 100% rated thrust output. (Full take- APEX1 was a collaborative research effort sponsored by off thrust at the high desert altitude corresponds to 93% NASA, EPA and DOD. It brought together scientists from three of the rated engine thrust; henceforth, 100% will be used to de- NASA centers, the EPA, the U.S. Army and Air Force (USAF), note 93%). Except for the 100% thrust level where run-time three universities, engine and airframe manufacturers, and was limited to 1.5 min, approximately 10 min were spent at two private research corporations. each thrust setting to allow adequate time for analyzing sam- During APEX1, particle and gas emissions were measured ples from each of the three downstream probes. The EPA test at 11 engine thrust settings for each of 3 different fuels (base, matrix followed the ICAO-defined LTO (landing-take off) cycle high-sulfur, and high-aromatic fuels) in samples drawn from to simulate aircraft emissions at the airport, and consisted of probes located 1, 10, and 30 m (3, 33, 98 ft, respectively) approximately 26 min at idle (7%), 0.7 min at take off (100%),

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13 Figure 3. Schematic of NASA DC-8 with sampling rakes and mobile laboratories. 2.2 min at climb (85%), and 4 min at approach (30%) engine Temperature probes (type-K thermocouples) and total and thrust settings. For the entire test matrix, each engine condition static pressure probes mounted on the rake were used to map was repeated several times to get a measure of statistical repeata- the core-flow position. bility and to allow adequate run time for the collection of time- Particle samples collected at 1 and 10 m (3 ft and 33 ft) used integrated samples for chemical characterization. the same type of probes and sample transport tubing. At the A portable weather station was erected a short distance from 1-m (3-ft) location, particle samples were diluted at each par- the test site and used to continuously monitor and record ticle probe tip with a concentric flow of dry nitrogen (N2) to ambient wind, temperature, and pressure throughout the suppress particle-particle interactions and the generation of engine runs. new aerosol due to gas-to-particle conversion involving water Multi-port particle and gas sample rakes were designed, and sulfuric acid. The 10-m (33-ft) samples were typically not built, and deployed to map the spatial variations of emis- diluted. The 30-m (98-ft) location probe was a single probe sions properties across the exhaust plume at the 1- and 10-m (3-ft and 33-ft) probe locations. As shown in Figure 4, these P1 rakes held six traditional gas inlet ("G") probes and six parti- GG1 G1 P2 cle inlet ("P") probes that allowed introduction of dilution air G2 just downstream of the probe tip. To provide adequate flow GG3 P3 G3 for filter and whole-air samplers, six additional, large-diameter P4 G4 gas inlet ("GG") probes were attached to either side of the P5 G5 1-m (3-ft) rake, aligned horizontally with the six, centerline- GG5 P6 mounted gas probes. The particle and gas probes were mounted CFM56-2C1 G6 in an alternating pattern at 32-mm (1.26-in.) spacings and numbered from the top to bottom in the rake. The 1-m (3-ft) sample rake was minimally cooled with low-pressure water. Out In At the 30-m (98-ft) location, a single probe sampled the Water mixed exhaust plume without further dilution. Figure 4. Orientation of sampling probes The center of the 1-m (3-ft) rake was aligned approxi- (P-particulate, G-gaseous, GG-external gaseous) mately 77 mm (0.25 ft) to the side of the engine vent tube. with respect to the engine exit plane.