Search Results

The design and development of an instrument for the measurement of total hydrocarbons in diesel exhaust are described, and its ability to measure steady-state and transient hydrocarbon emissions is indicated. The two-section system comprises a sampling train and flame-ionization detector and a chromatograph electrometer, recorder and backpressure regulator. A mixture of 40% H2 and 60% He was found to be the best fuel for low O2 response with the system. The method has been used for more than a year in evaluating hydrocarbon emissions from a wide variety of diesel engines under a number of typical operating conditions. The greatest advantage of the high-temperature system is its potential for expressing the total hydrocarbon content in diesel exhaust.

The use of diesel exhaust-emissions measurements to predict the observed odor from diesel engine exhaust has been studied, using a group of 31 trucks and buses powered by a variety of diesel engines. Regression analysis of gaseous emissions at a variety of conditions has resulted in equations for use in predicting odor. Acrolein, carbon dioxide, total hydrocarbons, selected light hydrocarbons, nitric oxide, carbon monoxide, and aliphatic aldehydes have been related to perceived odor. Some of these exhaust products are odorous and some are nonodorous yet indicative of the completeness of combustion. The empirical method, however, is somewhat less reliable than the observed odor based on a trained panel rating supra-threshold levels in terms of the PHS Quality-Intensity Odor Rating kit. In general, the greater variety of measurements and the fewer type of engines will increase odor prediction accuracy.

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.

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.

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 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.

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.

Five light-duty vehicles were used to investigate HC, CO, and NOx emissions and fuel economy sensitivity to changes in the length of soak period preceding the EPA Urban Dynamometer Driving Schedule (UDDS). Emission tests were conducted following soak periods 10 minutes to 36 hours in length. Each of the first 8 minutes of the driving cycle was studied separately to observe vehicle warm-up. Several engine and fuel system temperatures were monitored during soak and run periods and example trends are illustrated. The extent to which emission rates and fuel consumption are affected by soak period length is discussed.

Exhaust emissions from heavy duty gasoline-powered vehicles have been studied in detail, under NAPCA support, at South west Research Institute. The principal exhaust emissions studied were carbon monoxide, hydrocarbons, and oxides of nitrogen. A broad variety of vehicles was tested with three variable speed experimental procedures using chassis dynamometers to simulate actual road operations. Approximately 150 trucks and buses of all weight classes were investigated to determine the ability of each vehicle to perform with the respective experimental cycle, each vehicle’s contribution of contaminants on a mass basis per mile driven, and the applicability of these cyclic test procedures for federal testing.

The advent of diesel-powered versions of production passenger cars signals significant dieselization in the United States. Two vehicles, an experimental Oldsmobile diesel Cutlass and a Volkswagen diesel-powered Rabbit, were evaluated to determine their gaseous, particulate, smoke, odor, and noise emissions. For comparison, a 1977 Oldsmobile Cutlass powered by the 260 CID gasoline engine and a 1.6 liter gasoline fuel injected Volkswagen Rabbit (Calfornia version) were similarly evaluated under most emission categories. Three transient driving cycles were employed including those used in emissions certification, sulfate testing, and highway fuel economy.

The problem with diesel exhaust particulate is that it is “too-small”, “too-light”, and there is “too-much” of it. A series of experiments are described that investigate the potential of using an alumina-coated steel wool media, for agglomeration, and an advanced design inertia separator, for collection of the particulate from a 1975 Mercedes 300D diesel car. The goal of 50 percent reduction was realized when new. The effects on other emissions, performance, and noise were evaluated and durability defined.

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.

A wide variety of exhaust emissions are reported for three diesel engines typically used in heavy-duty intercity truck and intracity bus operation. Particulate, odor, sulfate, sulfur dioxide, and selected non-reactive hydrocarbons were measured in addition to the regulated pollutants from Detroit Diesel 6V-7l and 8V-7lTA engines and a turbocharged Cummins 855 cu in research engine. The 855-TC engine was run in standard and a variable injection timing configuration, while the 6V-7l city bus engine was run with two types of injector designs. Emission rates are summarized in terms of grams per unit of fuel consumed and per unit of power output. The data allows direct comparison between engines and engine configurations, as well as a function of engine speed and load condition.

Diesel-powered cars afford some distinct advantages in fuel economy and certain exhaust emissions relative to the conventional Otto cycle engine. Particulate and sulfate emissions from light-duty diesels are two important unregulated emissions for which little is known. Five diesel-powered, light-duty vehicles, a Peugeot 204D, a Mercedes 240D, a Mercedes 300D, a Comprex-equipped Mercedes 220D, and a Perkins 6-247 powered IH pickup, were used to quantify the range of particulate, sulfate as well as other unregulated emissions of odor, visible smoke, sulfur dioxide, aldehydes, and selected non-reactive hydrocarbons. Three transient driving cycles were employed including that used in emissions certification, sulfate testing, and highway fuel economy. Emission rates of particulate, sulfate, and other contaminants of a regulated and unregulated nature are presented in several ways: mass per unit of time, per unit of fuel consumed, and per unit of distance driven.