Ralph D. Nine

Factors Affecting Heavy-Duty Diesel Vehicle Emissions

Abstract Societal and governmental pressures to reduce diesel exhaust emissions are reflected in the existing and projected future heavy-duty certification standards of these emissions. Various factors affect the amount of emissions produced by a heterogeneous charge diesel engine in any given situation, but these are poorly quantified in the existing literature. The parameters that most heavily affect the emissions from compression ignition engine-powered vehicles include vehicle class and weight, driving cycle, vehicle vocation, fuel type, engine exhaust aftertreatment, vehicle age, and the terrain traveled. In addition, engine control effects (such as injection timing strategies) on measured emissions can be significant. Knowing the effect of each aspect of engine and vehicle operation on the emissions from diesel engines is useful in determining methods for reducing these emissions and in assessing the need for improvement in inventory models. The effects of each of these aspects have been quantified in this paper to provide an estimate of the impact each one has on the emissions of diesel engines.

Fuel Property, Emission Test, and Operability Results from a Fleet of Class 6 Vehicles Operating on Gas-to-Liquid Fuel and Catalyzed Diesel Particle Filters

A fleet of six 2001 International Class 6 trucks operating in southern California was selected for an operability and emissions study using gas-to-liquid (GTL) fuel and catalyzed diesel particle filters (CDPF). Three vehicles were fueled with CARB specification diesel fuel and no emission control devices (current technology), and three vehicles were fueled with GTL fuel and retrofit with Johnson Mattheys CCRT diesel particulate filter. No engine modifications were made.

Development of a heavy-duty chassis dynamometer driving route

Abstract There is presently a lack of realistic driving cycles or schedules for the chassis dynamometer emissions testing of heavy-duty trucks. This research effort was motivated by the need for representative emissions measurement techniques to compare alternatively fuelled trucks with their diesel or gasoline counterparts operating in heavy-duty truck applications. Speed versus time and video recording data gathered from trucks in local delivery use were used to develop a city/suburban heavy vehicle route (referred to as the CSHVR) for Class 7 (11 794-14969 kg gross vehicle weight) and Class 8 (14969-36287 kg) delivery trucks. Statistical data were gathered on actual truck driving behaviour, as well as 60 h of actual speed versus time driving information. A cycle was then developed by joining microtrips from the actual truck operation and verifying that it was representative of the whole database. A driving route was derived from this cycle with the help of the video data, and with the vehicle deceleration rates modified for practical reasons. It was found that a more powerful truck could bias its exhaust gas emissions by not aggressively applying full power while following a conventional speed versus time trace cycle. In comparison with a speed versus time cycle, a route allows sections of free acceleration (at full power) until a desired overall operating distance is met. A route is defined by a path that a truck must follow where driving instructions are dependent upon the acceleration of the truck, road conditions and speed limitations. The new route has been successfully employed in the emissions testing of several Class 8 tractors and was found to yield emission rates (in g/mile) that were higher than those for the previously documented WVU five-mile route (8 km in length) in the case of a Ford 36287 kg (80000 lb) GVWR tractor with a mechanically injected Cummins 261 kW (350 hp) engine.

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.

USE OF SOY-DERIVED FUEL FOR ENVIRONMENTAL IMPACT REDUCTION IN MARINE ENGINE APPLICATIONS

Diesel-fueled marine engines can contribute to both air and water pollution, particularly when cooling water is contacted with products of combustion in the exhaust system. Soy-derived compression ignition fuel offers a route to reducing these emissions and their effects. A 1972 Westerbeke marine diesel engine was mounted on a dynamometer and the exhaust was arranged so that sampling was possible both with (“wet” also termed “scrubbing”) and without (“dry”) water contact in the exhaust stream. Emissions testing was conducted using the steady state ISO E4 marine duty cycle. The engine was tested with 0, 10, 20, 50, and 100% methyl soy-ester blends with #2 off-road diesel. The pure alternative fuel offered a 45% reduction in particulate matter for both dry and wet tests, with carbon monoxide decreasing and oxides of nitrogen increasing slightly. Particulate matter (PM) reduction is significant in the water phase since it was noted that 40% of the PM entered the water phase upon wet testing. Fuel composition did not have a profound influence on the production of acetaldehyde, acetone, and formaldehyde in the exhaust. However, it was evident that wet testing, where the water contacted the cooling water, produced substantially lower formaldehyde and acetone, but substantially higher acetaldehyde than dry testing, where the exhaust was separated from the cooling water. Dry testing of marine diesel engines may therefore not truthfully reflect oxygenates produced in real use.

Hydrocarbon Speciation of a Lean Burn Spark Ignited Engine

A research program at West Virginia University sought to identify and quantify the individual hydrocarbon species present in alternative fuel exhaust. Compressed natural gas (CNG) has been one of the most widely researched fuels proposed to replace liquid petroleum fuels. Regulated CNG non-methane hydrocarbon emissions are often lower than hydrocarbon emissions from conventional liquid fuels because of the absence of heavier hydrocarbons in the fuel. Reducing NOX and non-methane organic gas (NMOG) emission levels reduces the ozone forming potential (OFP) of the exhaust gases. A Hercules GTA 3.7 liter medium duty CNG engine was operated at seven load and speed set points using local supply CNG gas. The engine was operated at several rated, intermediate and idle speed set points. The engine was operated while the air/fuel ratio value was varied. The lighter load tests as well as the lean operation tests showed an increase in the hydrocarbon emissions as a result of unburnt fuel passing through the engine. As the lambda value approached stochiometric operation, NOX increased and the HC decreased. Hydrocarbons were captured using a dedicated sampling system drawing a sample from a full scale dilution tunnel via a rotary vane pump through a mass flow controller and collected in a tedlar bag. The sample was then analyzed by a gas chromatograph for identification and species were quantified utilizing retention indices. Upon close analysis of the data, the production and destruction of compounds present in engine exhaust can be related to the test fuel and background dilution air. The intent of this research was to identify the formation of products such as ethene that arise from incomplete combustion.

Emissions from Diesel-Fueled Heavy-Duty Vehicles in Southern California

Few real-worid data exist to describe the contribution of diesel vehicles to the emissions inventory, although it is widely acknowledged that diesel vehicles are a significant contributor to oxides of nitrogen (NO x ) andparticulate matter (PM) in Southern California. New data were acquired during the Gasoline/Diesel PM Split Study, designed to collect emissions data for source profiling of PM emissions from diesel- and gasoline-powered engines in the South Coast (Los Angeles) Air Basin in 2001. Regulated gases, PM and carbon dioxide (CO 2 ) were measured from 34 diesel vehicles operating in the Southern California area. Two were transit buses, 16 were trucks over 33,000 Ibs. in weight, 8 were 14,001 Ibs. to 33,000 Ibs. in weight and 8 were under 14,001 Ibs. in weight. The vehicles were also grouped by model year for recruiting and data analysis. Emissions were measured in Riverside, CA, using West Virginia Universitys (WVU) Transportable Medium-Duty and Heavy-Duty Vehicle Emissions Testing Laboratories. The trucks were all exercised through a CSHVR, a Highway cycle, and an Idle period. In addition, selected vehicles were tested under cold start idle, cold start CSHVR, and the Urban Dynamometer Driving Schedule (UDDS). All data were computed in units of g/mile except for idle tests, which were recorded in g/cycle. Repeat runs on the same test schedule demonstrated that data were consistent from run to run. This paper presents the data for the trucks over 33,000 Ib. in weight. Data for these trucks showed conclusively that PM levels are higher for older vehicles: this may be due to vehicle age, but more likely is associated with the improved technology for later model years and implied compliance with later standards. In contrast, emissions of oxides of nitrogen (NO x ) have not fallen in the same way with respect to model year. The data provide new insight into real-world diesel truck emissions and will provide information for emissions source profiles for PM source apportionment in Los Angeles. The data reported in this presentation are a portion of the GasolinelDiesel PM Split Study, sponsored by the U.S. Department of Energys Office of FreedomCAR and Vehicle Technologies through the National Renewable Energy Laboratory.