Search Results

Measurement of emissions from small utility engines has usually been accomplished using steady-state raw emissions procedures such as SAE Recommended Practice J1088. While raw exhaust measurements have the advantage of producing modal exhaust gas concentration data for design feedback; they are laborious, may influence both engine performance and the emissions themselves, and have no provision for concurrent particulate measurements. It is time to consider a full-dilution procedure similar in principle to automotive and heavy-duty on-highway emission measurement practice, leading to improvements in many of the areas noted above, and generally to much higher confidence in data obtained. When certification and audit of small engine emissions become a reality, a brief dilute exhaust procedure generating only the necessary data will be a tremendous advantage to both manufacturers and regulatory agencies.

Exhaust emission data from several fuel effects studies were normalized and subjected to statistical analyses. The goal of this work was to determine whether emission effects of property variation in alternate-source fuels were similar, less pronounced, or more pronounced than the effects of property variation in petroleum fuels. A literature search was conducted, reviewing hundreds of studies and finally selecting nine which dealt with fuel property effects on emissions. From these studies, 15 test cases were reported. Due to the wide variety of vehicles, fuels, test cycles, and measurement techniques used in the studies, a method to relate them all in terms of general trends was developed. Statistics and methods used included bivariate correlation coefficients, regression analysis, scattergrams and goodness-of-fit determinations.

The U.S. Environmental Protection Agency (EPA) formed a Heavy-Duty Engine Working Group (HDEWG) in the Mobile Sources Technical Advisory Subcommittee in 1995. The goal of the HDEWG was to help define the role of the fuel in meeting the future emissions standards in advanced technology engines (beyond 2004 regulated emissions levels). A three-phase program was developed. This paper presents the results of the statistical analysis of the data collected in the Phase II program. Included is a description of the design of the fuel test matrix, and a listing of the regression equations developed to predict emissions as a function of fuel density, cetane number, monoaromatics, and polyaromatics. Also included is a description of selected analyses of the emissions from a smaller set of fuel data that allowed direct comparison of the effects of natural and boosted cetane number.

As stringent emission regulations further constrain engine manufacturers by tightening both NOx and particulate emission limits, a knowledge of fuel effects becomes more important than ever. Among the fuel properties that affect heavy-duty diesel engine emissions, cetane number can be very important. Part of the CRC-APRAC VE-10 Project was developed to quantify the effects of cetane number on NOx and other emissions from a prototype 1998 Detroit Diesel Series 60. Three fuels with different natural cetane number (41, 45, 52) were treated with several levels and types of cetane improvers to study a range of cetane number from 40 to 60. Statistical analysis was used to define how regulated emissions from this prototype 1998 engine decreased with chemically-induced cetane number increase. Variation of HC, CO, NOx, and PM were modeled using a combination of a fuel's naturally-occurring cetane number and its total cetane number obtained with cetane improver.

A Coordinating Research Council sponsored test program was conducted to determine the effects of diesel fuel properties on emissions from two heavy-duty diesel engines designed to meet EPA emission requirements for 1994. Results for a prototype 1994 DDC Series 60 were reported in SAE Paper 941020. This paper reports the results from a prototype 1994 Navistar DTA-466 engine equipped with an exhaust catalyst. A set of ten fuels having specific variations in cetane number, aromatics, and oxygen were used to study effects of these fuel properties on emissions. Using glycol diether compounds as an oxygenated additive, selected diesel fuels were treated to obtain 2 and 4 mass percent oxygen. Cetane number was increased for selected fuels using a cetane improver. Emissions were measured during transient FTP operation of the Navistar engine tuned for a nominal 5 g/hp-hr NOx, then repeated using a 4 g/hp-hr NOx calibration.

Several studies have investigated the effects of diesel fuel properties on heavy-duty engine emissions. The objective of this CRC-sponsored test program was to determine the effects of oxygenated diesel fuel, and to further investigate the effects of cetane number and aromatic content on emissions from a heavy-duty engine set to obtain transient NOx emissions below 5 and then 4 g/hp-hr. A fuel set was developed with controlled variations in cetane number, aromatics, and oxygen to superette their effects on emissions. Ignition improver was used to increase cetane number of several fuels. Oxygenated diesel fuel was achieved by adding a “glyme” compound to selected fuels to obtain 2 and 4 mass percent oxygen concentrations. With these fuels, emissions were measured over the EPA transient FTP using a prototype 1994 DDC Series 60 tuned for 5 and then 4 g/hp-hr NOx. No exhaust aftertreatment device was used on this engine.

Recent approval of emission standards for small utility engines by the California Air Resources Board(1)* suggests that substantial reductions in emissions from small utility engines will soon be required. While 1994 standards may be met with simple engine adjustments or modifications, 1999 standards are much more stringent and may require the use of catalysts in conjunction with other emission reduction technologies. Assessing the feasibility of candidate emission control strategies is an important first step. Various emission reduction technologies were applied to three different 4-stroke engines. Emission tests were conducted to determine the effectiveness of air/fuel ratio changes, thermal oxidation, exhaust gas recirculation, and catalytic oxidation with and without supplemental air. Results of these evaluations, along with implications for further work, are presented. One engine's emissions were reduced below the levels of 1999 ARB standards.

To characterize exhaust emissions from water-cooled 2-stroke outboard motors (the predominant type), four new motors were tested on dynamometer stands. The engines ranged from 4-65 hp in size, and operating conditions were chosen along lines of simulated boat loading. All the measurements were taken at steady-state conditions. Emission concentrations were measured in raw exhaust gas and after the gases had been bubbled through water in a specially constructed tank. Constituents measured included hydrocarbons, CO, CO2, NO, NOx, O2, light hydrocarbons, and aldehydes. Emissions of sulfur oxides (SOx) were estimated on the basis of fuel consumed, and all the exhaust emissions data were used with available information on population and usage of motors to estimate exhaust emission factors and national exhaust emissions impact.

The research program on which this paper is based included both laboratory emission measurements and extrapolation of results to the national population of heavy-duty farm, construction, and industrial engines. Emission tests were made on four gasoline engines and eight diesel engines typical of those used in F, C, and I equipment. Gaseous and particulate emissions were measured during engine operation on well-accepted steady-state procedures, and diesel smoke was measured during both steady-state conditions and the Federal smoke test cycle. Emissions measured were hydrocarbons, CO, CO2, NO, NOx, O2, aliphatic aldehydes, light hydrocarbons, particulate, and smoke. Emission of sulfur oxides (SOx) was estimated on the basis of fuel consumed, and both evaporative and blowby hydrocarbons were also estimated where applicable (gasoline engines only). Data on emissions obtained from this study were compared with those available in the literature, where possible.

To develop a methodology for characterizing particulate emissions from diesel engines, one 2-stroke cycle engine and one 4-stroke cycle engine were operated in both individual steady-state modes and according to a variation of the 13-mode diesel emissions measurement procedure. Both engines were operated on three fuels, each used with one of two available diesel fuel additives as well as by itself. The primary particulate sampling technique employed was a dilution tunnel, and secondary evaluation techniques included a diluter-sampler developed under contract to EPA by another organization, a light extinction smokemeter, and a filter-type sampling smokemeter. Gaseous emissions were also measured, providing a running check on engine condition. Particulate mass rates were calculated from gravimetric data; and analysis of particulate included determination of sulfur, carbon, hydrogen, nitrogen, phenols, nitrosamines, trace metals, and organic solubles.

Seven motorcycles, ranging in size from 100 to 1200 cm3, were tested for emissions characterization purposes. They were operated on the federal seven-mode test procedure (for 1971 and older light-duty vehicles), the federal LA-4 test procedure (for 1972 and later LDVs), and under a variety of steady-state conditions. Four of the machines tested had 4-stroke engines, and the other three had 2-stroke engines. Emissions which were measured included hydrocarbons, CO, CO2, NO, NOx, O2, aldehydes, light hydrocarbons, particulates, and smoke. Emissions of SOx were estimated on the basis of fuel consumed, and evaporative hydrocarbon losses were also estimated. Crankcase “blowby” emissions from one 4-stroke machine were measured. The impact of motorcycles on national pollutant totals was estimated, based on the test results and information from a variety of sources on national population and usage of motorcycles.

This paper describes the results of a public opinion survey on testing of diesel exhaust odors conducted during 1969 and 1970. Major goals of the research were to relate public opinion of the odors and the objectionability associated with them to odor intensity, and to obtain a dose-response curve as the primary result. The dose-response curve was needed to assess odor-control technology by providing a criterion for deciding whether or not the effect of a given control item would be noticed by the general public, reduce complaints, or be worth the cost and effort required for its implementation. The engine used as the live odor source for the subject research was a two-stroke cycle type similar to those used in many buses. This engine type was chosen because its exposure to the public in urban bus applications is very widespread, and because a large portion of the Environmental Protection Agency's odor research had been performed with similar engines.

Five different diesel fuel feedstocks were processed to two levels of aromatic (0.05 sulfur, and then 10 percent) content. These materials were distilled into 6 to 8 narrow boiling range fractions that were each characterized in terms of the properties and composition. The fractions were also tested at five different speed load conditions in a single cylinder engine where high speed combustion data and emissions measurements were obtained. Linear regression analysis was used to develop relationships between the properties and composition, and the combustion and emissions characteristics as determined in the engine. The results are presented in the form of the regression equations and discussed in terms of the relative importance of the various properties in controlling the combustion and emissions characteristics. The results of these analysis confirm the importance of aromatic content on the cetane number, the smoke and the NOx emissions.

In an attempt to characterize emissions from small air-cooled utility engines, five gasoline-fueled models were operated over a variety of speeds and loads, and important exhaust constituents were measured. These emissions included hydrocarbons, CO, CO2, NO, O2, aldehydes, light hydrocarbons, particulates, and smoke. Emissions of SOx were estimated on the basis of the fuel consumed; evaporative losses of hydrocarbons were also estimated. The impact of small engine emissions was calculated on the basis of the test results and information on national engine populations and usage. From these data, it appears that the 50 million or more small engines currently being used account for only a small part of pollutants from all sources.

This paper describes a research program on exhaust emissions from snowmobile engines, including both emissions characterization and estimation of national emissions impact. Tests were conducted on three popular 2-stroke twins and on one rotary (Wankel) engine. Emissions that were measured included total hydrocarbons, (paraffinic) hydrocarbons by NDIR, CO, CO2, NO (by two methods), NOx, O2, aldehydes, light hydrocarbons, particulate, and smoke. Emissions of SOx were estimated on the basis of fuel consumed, and evaporative hydrocarbons were projected to be negligible for actual snowmobile operation. During emissions tests, intake air temperature was controlled to approximately -7°C (20°F), and room air at approximately 24°C (75°F) was used for engine cooling. Based on test results and the best snowmobile population and usage data available, impact of snowmobile emissions on a national scale was computed to be minimal.

The SwRI/BMW N.A. Intake Valve Deposit Test procedure was the first performance-based test procedure adopted for fuels qualification in the United States. The initial fuel evaluations were begun in January 1988 with six 1985 BMW 318i vehicles. Since that time, the fleet has grown to include over 60 BMW cars, and more than 2000 tests have been performed. This paper gives a statistical summary of approximately 1800 tests performed over a four-year period. Performance data and possible sources of test variation are discussed. Data and analyses offered represent results of tests by all clients. However, data is presented such that no individual test or client is identified.

Small engines which are friendly toward the environment are needed all over the world, whether the need is expressed in terms of energy efficiency, useful engine life, health benefits for the user, or emission regulations enacted to protect a population or an ecologically-sensitive area. Progress toward the widespread application of lower-impact small engines is being made through engine design, matching of engine to equipment and task, aftertreatment technology, alternative and reformulated fuels, and improved lubricants. This paper describes three research and development projects, focused on the interrelationships of fuels, lubricants, and emissions in Otto-cycle engines, which were conducted by Southwest Research Institute. All the work reported was funded internally as part of a commitment to advance the state of small engine technology and thus enhance human utility.

Beginning June 1, 2006, 80% of the highway diesel fuel produced in the United States had to contain 15 ppm sulfur or less. To account for sulfur test method variability, the United States Environmental Protection Agency (US EPA) allowed a 2 ppm compliance margin, meaning that in an EPA enforcement action fuel measuring 17 ppm or less would still be deemed compliant since the true sulfur level could still be 15 ppm. Concern was voiced over the appropriateness of the 2 ppm compliance margin, citing recent American Society for Testing and Materials (ASTM) round-robin and crosscheck test program results that showed sulfur test lab-to-lab variability (reproducibility) on the order of 4 to 5 ppm depending on test method.