Karl H. Hellman

Development of adjustment factors for the EPA city and highway MPG values

This paper describes the development of adjustment factors applicable to the EPA City and Highway MPG values. The paper discusses the data bases used, and the analytical methods employed to arrive at adjustment factors of 0.90 for the EPA City MPG value and 0.78 for the EPA Highway MPG value.

Passenger Car Fuel Economy - Trends and Influencing Factors

This paper discusses some trends and influencing factors in passenger car fuel economy. The information presented was derived from nearly 4000 tests of passenger cars ranging from 1957 production models to 1975 prototypes. Data are presented for various model year and vehicle weight categories. Three ways to characterize vehicle specific fuel consumption are presented and discussed. Possible ways to improve fuel consumption are also discussed.

Resistive Materials Applied to Quick Light-off Catalysts

The application of resistive materials as part of an exhaust emission control system is presented and discussed. The importance of cold start emissions is emphasized, and results are presented from experiments conducted with two different conductive materials. Most of the testing was conducted using methanol as the fuel, although some tests were run using gasoline-fueled vehicles

EFFECTS OF FUEL VARIABLES ON DIESEL EMISSIONS

The body of information presented in this paper is directed towards engineers in the field of environmental sciences involved in measuring and/or evaluating the emissions from a variety of diesel engines or vehicles. This paper summarizes recent data obtained by EPA on identification and quantification of different emissions (i.e. characterization) from a variety of diesel engines. Extensive work has been done comparing emissions from some light duty diesel and gasoline passenger cars. The work on the diesel vehicles was expanded to include tests with five different diesel fuels to determine how fuel composition affects emissions. This work showed that use of a poorer quality fuel frequently made emissions worse. The investigation of fuel composition continued with a project in which specific fuel parameters were systematically varied to determine their effect on emissions. EPA is presently testing a variety of fuels derived from coal and oil shale to determine their effects on emissions. EPA has also tested a heavy duty Volvo diesel bus engine designed to run on methanol and diesel fuel, each injected through its own injection system. The use of the dual fuel resulted in a reduction in particulates and NO but an increase in HC and CO compared to a baseline Volvo diesel engine running on pure diesel fuel. Finally, some Ames bioassay tests have been performed on samples from the diesel passenger cars operated on various fuels and blends. An increase in Ames test response (mutagenicity) was seen when the higher aromatic blend was used and also when a commercial cetane improver was used. Samples from the Volvo diesel bus engine fueled with methanol and diesel fuel showed that use of a catalyst increased the Ames response.

A Study of the Potential Impact of Some Unregulated Motor Vehicle Emissions

Studies of emissions from vehicles equipped with catalysts have shown that some unregulated emissions can increase when a catalyst is used. One example of this is sulfuric acid, which has been studied extensively. Other unregulated emissions include ammonia and hydrogen cyanide. In a number of studies, these unregulated pollutant emissions have been measured from light-duty vehicles and heavy-duty engines. These emission levels were used in air quality dispersion models to predict the resultant air quality levels. The ambient concentrations predicted for each pollutant were then compared to suggested concentrations at which adverse health effects may be found to determine if additional monitoring or control would be indicated for these pollutants. It was determined that mobile source emissions of sulfuric acid, hydrogen cyanide, and ammonia do not in general result in ambient levels of concern for the air quality situations studied.

Trends in alternate measures of vehicle fuel economy

This paper develops and discusses the 1978-85 time trends in alternative measures of vehicle fuel economy. Nine alternative measures are presented ranging from ton-miles per gallon to menu-weighted performance adjusted miles per gallon. For each alternative measure, trends for important groups of manufacturers are presented. All of the trends in alternative measures are compared to the percent improvement implied by the original 1978 and 1985 passenger car average fuel economy standards (AFES).

PASSENGER CAR FUEL ECONOMY AS INFLUENCED BY TRIP LENGTH

Data from the Nationwide Personal Transportation Study (NPTS) and other sources have been used to generate distributions of vehicle miles traveled (VMT), average speed, and fuel consumption as a function of trip length. The typical trip of approximately ten miles in length has been shown to result in a fuel economy that is equal to the average fuel economy achieved for all trips combined. NPTS data on average speed vs. trip length and General Motors data on stops-mile vs. average cycle speed indicate that the major characteristics of the trip that results in a fuel economy equal to the overall fuel economy are an average speed of 24.5 mph and 1.4 stops per mile. The composite of the U.S. Environmental Protection Agency city and highway driving cycles is 26.6 mph and 1.4 stops per mile.

EPA MOTOR VEHICLE EMISSIONS CHARACTERIZATION PROJECTS ON LIGHT AND HEAVY DUTY DIESELS

The body of information presented in this paper is directed towards engineers in the field of environmental sciences involved in measuring and evaluating the emissions from a variety of diesel engines or vehicles. This paper summarizes recent data obtained by EPA on identification and quantification of different emissions (i.e. characterization) from a variety of diesel engines. The effects of turbocharging, advanced injection timing, indirect vs. direct injection, exhaust gas recirculation (EGR), and different fuel pumps on HC, CO, NO/sub x/, sulfates, aldehyde, and particulate emissions were determined by testing several heavy duty diesel engines. A heavy duty gasoline engine was tested for comparison. Limited testing was done on a diesel bus engine under malfunction conditions (conditions different from manufacturers recommended specifications).

Fuel Economy of the 1975 Models

The fuel economy data obtained from the emission tests run by the U.S. Environmental Protection Agency (EPA) have been used to show passenger car fuel economy trends from model year 1957 to present. This paper adds the 1975 model year to the historical trend and concentrates on comparisons between the 1975 to 1974 models. The net change in fuel economy for the fleet has been estimated at plus 13.8% comparing the 1975 models to the 1974 models assuming no model mix change occurs. General Motors is responsible for the majority of the fleet average improvement.

Numerical Study to Achieve Stratified EGR in Engines

Exhaust Gas Re-circulation (EGR) has been used in intemal combustion engines to control automotive emissions. EGR is usually used to dilute the inlet charge, which consists of air, by redirecting part of the exhaust into the inlet manifold of the engine. This results in a reduction of the oxygen mass fraction in the inlet charge. However, dilution of the air-fuel mixture in an engine using stratified EGR could offer significant fuel economy saving comparable to lean burn or stratified charge direct-injection SI engines. The most critical challenge is to keep the EGR and air-fuel mixture separated, or to minimize the mixing between the two zones to an acceptable level for stable and complete combustion. Swirl-type stratified EGR and fuel-air flow structure is considered desirable for this purpose, because the circular shape of the cylinder tends to preserve the swirl motion. Moreover, the axial piston motion has minimal effect on the swirling motion of the fluid in the cylinder. In this study, we consider intake system design in order to generate a two-zone combustion system, where EGR is maintained in a layer on the periphery of the cylinder, and the fuel-air mixture is maintained in the center of the cylinder. KIVA-3V was used to perform numerical simulations on different EGR systems. The simulations were performed to determine if the two-zones can be generated in the cylinder, and to what extent mixing between the two zones occurs. For the engine geometries considered in this study, the results showed that it is possible to generate the two zones, but mixing is difficult to control.Copyright