Donald W. Lyons

Emissions from Trucks using Fischer-Tropsch Diesel Fuel

The Fischer-Tropsch (F-T) catalytic conversion process can be used to synthesize diesel fuels from a variety of feedstocks, including coal, natural gas and biomass. Synthetic diesel fuels can have very low sulfur and aromatic content, and excellent autoignition characteristics. Moreover, Fischer-Tropsch diesel fuels may also be economically competitive with California B- diesel fuel if produced in large volumes. overview of Fischer-Tropsch diesel fuel production and engine emissions testing is presented. Previous engine laboratory tests indicate that F-T diesel is a promising alternative fuel because it can be used in unmodified diesel engines, and substantial exhaust emissions reductions can be realized. The authors have performed preliminary tests to assess the real-world performance of F-T diesel fuels in heavy-duty trucks. Seven White-GMC Class 8 trucks equipped with Caterpillar 10.3 liter engines were tested using F-T diesel fuel. Vehicle emissions tests were performed using West Virginia Universitys unique transportable chassis dynamometer. The trucks were found to perform adequately on neat F-T diesel fuel. Compared to a California diesel fuel baseline, neat F-T diesel fuel emitted about 12% lower oxides of nitrogen (NOx) and 24% lower particulate matter over a five-mile driving cycle.

Diesel and CNG Transit Bus Emissions Characterization By Two Chassis Dynamometer Laboratories: Results and Issues

Emissions of six 32 passenger transit buses were characterized using one of the West Virginia University (WVU) Transportable Heavy Duty Emissions Testing Laboratories, and the fixed base chassis dynamometer at the Colorado Institute for Fuels and High Altitude Engine Research (CIFHAER). Three of the buses were powered with 1997 ISB 5.9 liter Cummins diesel engines, and three were powered with the 1997 5.9 liter Cummins natural gas (NG) counterpart. The NG engines were LEV certified. Objectives were to contrast the emissions performance of the diesel and NG units, and to compare results from the two laboratories. Both laboratories found that oxides of nitrogen and particulate matter (PM) emissions were substantially lower for the natural gas buses than for the diesel buses. It was observed that by varying the rapidity of pedal movement during accelerations in the Central Business District cycle (CBD), CO and PM emissions from the diesel buses could be varied by a factor of three or more. The driving styles may be characterized as aggressive and non-aggressive, but both styles followed the CBD speed command acceptably. PM emissions were far higher for the aggressive driving style. For the NG fueled vehicles driving style had a similar, although smaller, effect on NO{sub x}. It is evident that driver habits may cause substantial deviation in emissions for the CBD cycle. When the CO emissions are used as a surrogate for driver aggression, a regression analysis shows that NO{sub x} and PM emissions from the two laboratories agree closely for equivalent driving style. Implications of driver habit for emissions inventories and regulations are briefly considered.

ALTERNATIVE FUEL TRANSIT BUS EVALUATION PROGRAM RESULTS

The objective of this program, which is supported by the U.S. Department of Energy (DOE) through the National Renewable Energy Laboratory (NREL), is to provide an unbiased and comprehensive comparison of transit buses operating on alternative fuels and diesel fuel. The information for this comparison was collected from eight transit bus sites. The fuels studied are natural gas (CNG and LNG), alcohol (methanol and ethanol), biodiesel (20 percent blend), propane (only projected capital costs; no sites with heavy-duty propane engines were available for studying operating experience), and diesel. Data was collected on operations, maintenance, bus equipment configurations, emissions, bus duty cycle, and safety incidents. Representative and actual capital costs were collected for alternative fuels and were used as estimates for conversion costs. This paper presents preliminary results.

Chassis Test Cycles for Assessing Emissions from Heavy Duty Trucks

Emissions from internal combustion engines can be evaluated by testing the engine itself or testing a whole vehicle using a chassis dynamometer. Recent concerns over atmospheric pollution and the drive to examine alternative fuel technology have led to an interest in chassis testing of trucks and buses. In particular these chassis tests permit the examination of changing emissions over the life of the vehicle. Identification of the chassis test protocols for heavy duty vehicles remains inchoate, but this paper seeks to assuage part of the problem by offering a practical test schedule for Class 8 trucks and truck-tractors in the 15000 to 36,360 kg GVW range. 8 refs., 15 figs., 1 tab.

Idle Emissions from Medium Heavy-Duty Diesel and Gasoline Trucks

Abstract Idle emissions data from 19 medium heavy-duty diesel and gasoline trucks are presented in this paper. Emissions from these trucks were characterized using full-flow exhaust dilution as part of the Coordinating Research Council (CRC) Project E-55/59. Idle emissions data were not available from dedicated measurements, but were extracted from the continuous emissions data on the low-speed transient mode of the medium heavy-duty truck (MHDTLO) cycle. The four gasoline trucks produced very low oxides of nitrogen (NOx) and negligible particulate matter (PM) during idle. However, carbon monoxide (CO) and hydrocarbons (HCs) from these four trucks were approximately 285 and 153 g/hr on average, respectively. The gasoline trucks consumed substantially more fuel at an hourly rate (0.84 gal/hr) than their diesel counterparts (0.44 gal/hr) during idling. The diesel trucks, on the other hand, emitted higher NOx (79 g/hr) and comparatively higher PM (4.1 g/hr), on average, than the gasoline trucks (3.8 g/hr of NOx and 0.9 g/hr of PM, on average). Idle NOx emissions from diesel trucks were high for post-1992 model year engines, but no trends were observed for fuel consumption. Idle emissions and fuel consumption from the medium heavy-duty diesel trucks (MHDDTs) were marginally lower than those from the heavy heavy-duty diesel trucks (HHDDTs), previously reported in the literature.

Evaluation of Emissions from New and In-Use Transit Buses in Mexico City, Mexico

The West Virginia University Transportable Heavy-Duty Emissions Testing Laboratory was used to evaluate exhaust emissions from nine transit buses from six separate manufacturers, as commissioned by the Mexico City, Mexico, Secretariat of the Environment. The vehicles included a hybrid-drive diesel bus, two buses with lean-burn spark-ignited compressed natural gas (CNG) engines, and six buses powered by conventional diesel engines. Vehicle testing weights (curb weight plus passenger weight) ranged from 26,996 Ib (12,256 kg) to 57,025 Ib (25,889 kg), and passenger capacities ranged from 85 to 161. Two driving cycles, the European Transient Cycle (ETC, also known as the FIGE transient cycle) and a new, three-mode Mexico City Schedule, were used to simulate in-use driving conditions during emissions measurements. Diesel fuels with three different sulfur concentrations (15, 150, and 350 ppm) were also examined, and the lowest-sulfur fuel (15 ppm) was not found to have an appreciable direct effect on emissions....

Thermo-elastic Stresses in Composite Beams with Functionally Graded Layer

Analytical expressions have been derived for the thermo-elastic stresses in a three-layered composite beam system whose middle layer is a functionally graded material (FGM). Continuous gradation of the volume fraction in the FGM layer is modeled in the form of an mth power polynomial of the coordinate axis in thickness direction of the beam. Solutions for beams with linear, quadratic, or cubic distributions of continuous gradation in the FGM layer can be obtained from a single algorithm, just by changing the value of the exponent ‘m’. A numerical scheme of discretizing the continuous FGM layer (in sublayers) and treating the beam as a discretely graded structure has also been developed. Appropriate expressions for the solution have been derived for the case of continuous power law gradation (mth power) of the FGM layer. The discretized FGM layer scheme has been shown to yield results that practically match those predicted analytically by the closed-form model.

A Long Term Field Emissions Study of Natural Gas Fueled Refuse Haulers in New York City

New York City Department of Sanitation has operated natural gas fueled refuse haulers in a pilot study: a major goal of this study was to compare the emissions from these natural gas vehicles with their diesel counterparts. The vehicles were tandem axle trucks with GVW (gross vehicle weight) rating of 69,897 pounds. The primary use of these was for street collection and transporting the refuse to a landfill. West Virginia University Transportable Heavy Duty Emissions Testing Laboratories have been engaged in monitoring the tailpipe emissions from these trucks for seven-years. In the later years of testing the hydrocarbons were speciated for non-methane and methane components. Six of these vehicles employed the older technology (mechanical mixer) Cummins L-10 lean burn natural gas engines. Five trucks were equipped with electronically controlled Detroit Diesel Series 50 lean burn engines, while another five were powered by Caterpillar stoichiometric burn 3306 natural gas engines, The Ca terpillar engines employed an exhaust oxygen sensor feedback and three way catalysts. Since the refuse haulers had automatic Allison transmissions, and since they were employed in stop-and-go city service, initial emissions measurements were made using the Central Business Cycle (SAE Jl376) for buses at 42,000 pound test weight. Some additional measurements were made using an ad hoc cycle that has been designed to be more representative of the real refuse hauler use that included several compaction cycles. The Cummins powered natural gas vehicles showed oxides of nitrogen and carbon monoxide emission variations typically associated with variable fuel mixer performance. In the first Year of testing, the stoichiometric Caterpillar engines yielded low emission levels, but in later years two of these refuse haulers had high carbon monoxide attributed to failure of the feedback system. For example, carbon monoxide on these two vehicles rose from 1.4 g/mile and 10 g/mile in 1995 to 144.9 g/mile and 57.8 g/mile in 1996. These stoichiometric engines were also less fuel efficient than their lean burn counterparts. The Detroit Diesel Series 50 powered refuse haulers produced high levels of oxides of nitrogen. However, it was found that changing the shifting patterns of the transmission lowered the oxides of nitrogen. All three engine types showed the potential for low emissions operation and the particulate matter reduction advantage offered by natural gas was evident from the results.

Creation and Evaluation of a Medium Heavy-Duty Truck Test Cycle

The California Air Resources Board (ARB) developed a Medium Heavy-Duty Truck (MHDT) schedule by selecting and joining microtrips from real-world MHDT. The MHDT consisted of three modes; namely, a Lower Speed Transient, aHigher Speed Transient, and a Cruise mode. The maximum speeds of these modes were 28.9, 58.2 and 66.0 mph, respectively. Each mode represented statistically selected truck behavior patterns in California. The MHDT is intended to be applied to emissions characterization of trucks (14,001 to 33,0001b gross vehicle weight) exercised on a chassis dynamometer. This paper presents the creation of the MHDT and an examination of repeatability of emissions data from MHDT driven through this schedule. Two trucks were procured to acquire data using the MHDT schedule. The first, a GMC truck with an 8.2-liter Isuzu engine and a standard transmission, was tested at laden weight (90% GVW, 17,5501b) and at unladen weight (50% GVW, 9,7501b). The second, a Freightliner with a 7.2-liter Caterpillar engine and an automatic transmission, was tested only at 13,000lb (50% GVW). The test runs were performed using the West Virginia University (WVU) medium-duty chassis dynamometer, located in Riverside, CA. Vehicle inertia was mimicked using a flywheel set, and tire and wind drag were mimicked using an eddy current power absorber. The truck exhaust was ducted to a full-scale dilution tunnel, with HEPA filtered dilution air, and a flow rate of approximately 1,500scfm. Particulate matter (PM) mass was found gravimetrically, using filtration, while carbon dioxide (CO 2 ), carbon monoxide (CO), oxides of nitrogen (NO x ) and hydrocarbons (HC) were measured using research grade analyzers. Data were computed in units of g/cycle, g/mile, g/ahp-hr, g/gallon and g/minute, and were examined most carefully in units of g/mile. Preliminary runs showed that the GMC truck did deviate from the target trace when tested at laden weight, and the completed distance for the MHDT Lower Speed Transient mode varied from 0.906 to 0.954 miles. Laden data from the GMC truck demonstrated that emissions were repeatable for all three modes of the MHDT schedule. Averaged GMC truck results for all laden runs of the Lower Speed Transient mode were 8.99g/mile NO x and 0.26g/mile PM results for the Higher Speed Transient mode were 6.50g/mile NO x and 0.20g/mile PM and for the Cruise mode were 4.73g/mile NO x and 0.09g/mile PM. Unladen data from the GMC truck also showed acceptable repeatability, with emissions of NO x that were about 87% of the laden values. The Freightliner, with an automatic transmission, produced 16.39g/mile NO x and 0.33g/mile PM on the Lower Speed Transient mode, 12.59g/mile NOX and 0.25g/mile PM on the Higher Speed Transient mode, 7.93g/mile NO x and 0.14g/mile PM on the Cruise mode and 7.57g/mile NO x and 0.19g/mile PM on the UDDS (Test D). when three runs of thee same mode were run back-to-back, the standard deviation of NO x values for six sequences of runs were under 4% of the average for all three modes on both the manual transmission truck at laden test weight and the automatic transmission truck at unladen weight. CO 2 variation was under 4% as well, except in one instance. In two of the six sequences PM variability exceeded 10%. The researchers concluded that the MHDT was suitable for characterizing the emissions from trucks in future inventory research. Data also showed that emissions from a mode were unaffected by whichever mode was run previously.

On-Road Use of Fischer-Tropsch Diesel Blends

Alternative compression ignition engine fuels are of interest both to reduce emissions and to reduce U.S. petroleum fuel demand. A Malaysian Fischer-Tropsch gas-to-liquid fuel was compared with California No.2 diesel by characterizing emissions from over the road Class 8 tractors with Caterpillar 3176 engines, using a chassis dynamometer and full scale dilution tunnel. The 5-Mile route was employed as the test schedule, with a test weight of 42,000 lb. Levels of oxides of nitrogen (NO{sub x}) were reduced by an average of 12% and particulate matter (PM) by 25% for the Fischer-Tropsch fuel over the California diesel fuel. Another distillate fuel produced catalytically from Fischer-Tropsch products originally derived from natural gas by Mossgas was also compared with 49-state No.2 diesel by characterizing emissions from Detroit Diesel 6V-92 powered transit buses, three of them equipped with catalytic converters and rebuilt engines, and three without. The CBD cycle was employed as the test schedule, with a test weight of 33,050 lb. For those buses with catalytic converters and rebuilt engines, NO x was reduced by 8% and PM was reduced by 31% on average, while for those buses without, NO x was reduced by 5% and PM was reduced by 20% on average. It is concluded that advanced compression ignition fuels from non-petroleum sources can offer environmental advantages in typical line haul and city transit applications.