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Two techniques were investigated to reduce the emissions of oxides of nitrogen from a conventional regenerative gas turbine burner that involved only minor changes to the burner configuration and did not impair overall burner and engine performances. These methods were to vary the primary zone equivalence ratio and to shorten the residence time of the gas in the primary zone. Significant reductions in nitric oxide emissions were obtained by applying both methods, singly and in various combinations with one another, to the burner of the General Motors GT-309 vehicular regenerative gas turbine. Reductions in emissions that were measured on a single burner test facility at simulated engine steady-state conditions were confirmed when operating a GT-309 gas turbine powered vehicle over the HEW passenger car emission test cycle.

Although exhaust gas odorants are generally a product of engine and fuel parameters, it is the vehicle that the public associates with exhaust odor. The vehicle and its movements have a large influence on the dispersion of exhaust odorants and, therefore, on the actual public exposure to exhaust odor. A considerable amount of public exposure to vehicle exhaust odor results from municipal operation of diesel-powered buses, especially during the bus-stop sequence. Panel test procedures were developed for field evaluation of full-scale vehicle exhaust odor intensity during the idle and acceleration portions of a simulated bus-stop sequence. Odor tests, based on natural dilution of the vehicle exhaust to the odor threshold, were conducted in a controlled environment, indoors in large buildings. Different degrees of exhaust dilution were achieved by randomly varying the distance from the test vehicle to the panelists.

Exhaust emission tests run on an engine dynamometer are compared with those run on a chassis dynamometer. The worst case average difference between the chassis and engine dynamometer mass emissions, obtained over a period of 6 months, was less than 7%. The elimination of the driver, vehicle, and chassis dynamometer yielded significant improvement in test reproducibility with respect to carbon monoxide and oxides of nitrogen. A digital computer was used to control speed and throttle position of the engine dynamometer experiments. No transmission was used. The computer and engine dynamometer duplicated transient effects of transmission, vehicle, and chassis dynamometer.

This paper describes a computer-controlled engine test cell being developed at the General Motors Research Laboratories. The object is to combine the advantages of the controlled experimental conditions possible in an engine test cell with the dynamic capabilities of a vehicle driven on the road or on a chassis dynamometer to produce a unique research and development tool. The overall system, consisting of an IBM 1800 process control computer linked to an electric dynamometer and engine in an engine test cell, is introduced. A description is given of the test cell control and data acquisition instrumentation and of the pallet system which permits prebuilding of engine experimental packages for rapid installation in the test cell. An overview of the computer programs, with emphasis on user interaction, is presented. The throttle and speed control algorithms, which apply road or chassis dynamometer load conditions to the engine in the engine test cell, are discussed.

Concern over exhaust emissions has revived interest in the gas turbine as a powerplant for passenger cars, and concern over cost has stimulated interest in the single-shaft version of this engine. A novel transmission is needed to compensate for the inherently poor output characteristics of the single-shaft engine. The rated power and response time of the engine and the efficiency and power split of the transmission are shown to be the primary parameters influencing vehicle acceleration. Some factors affecting engine response time are reviewed. Transmission parameters are studied by considering standing-start accelerations of an automobile powered by a fixed-geometry single-shaft engine using versions of three of the many types of possible transmissions. For the combinations considered, the fixed-geometry single-shaft engine cannot easily provide vehicle performance matching that of the traditional two-shaft turbine engine, if both start with the compressor idling at half rated speed.

The single-shaft gas turbine engine has been proposed as a reduced-cost alternate to the previously used two-shaft turbine engine for application to passenger cars. The power output characteristics of the fixed-geometry single-shaft engine have been found to create performance difficulties, particularly with respect to standing-start acceleration of the vehicle. A review of the fundamentals responsible for these difficulties leads to the observation that variable compressor geometry can provide relief from this situation. Use of variable inlet guide vanes is identified as the simplest means of gaining this relief. Design factors influencing the susceptibility of the compressor to control by inlet guide vanes are considered. A method by which inlet guide vanes can be used to improve vehicle acceleration, without penalizing fuel consumption, is illustrated.

The initial NOx reduction activity of several alumina-supported, platinum-group metal catalysts is evaluated in vehicle tests. The experimental vehicle was equipped with two 36 in3 NOx converters, and a 260 in3 oxidation converter containing a pelleted platinum catalyst, rich carburetion, and exhaust gas recirculation. The NOx catalysts included Ru, Ru-Pt, Ru-Pd, mechanical mixtures of Ru and Pt, Pt-Ni, Pt, and Pd. As evaluated over the 1975 FTP, the NOx reducing effectiveness of these catalysts was: Ru combinations > Pt-Ni > Pt ≈ Pd. Modulated air injection was used, enabling the NOx converters to be used as oxidizing converters during vehicle start-up. Operation in this mode greatly reduced HC and CO emissions, with an acceptable increase in NOx emissions. In addition, the NOx reduction performance of all the NOx catalysts was enhanced by bleeding a small amount of air into the NOx converters. Minimum NOx emissions corresponded to air bleed rates of 3-4% of the total engine airflow.

This study was undertaken to develop a better understanding of how intake charge dilution by various gases affected nitric oxide (NO) emission from a single-cylinder spark ignition engine. Carbon dioxide, nitrogen, helium, argon, steam, and exhaust gas were individually added to the intake charge of a propane-fueled, single-cylinder engine operated at constant speed and load. Nitric oxide emission was reduced in all cases. The gases with higher specific heats gave larger NO reductions. The product of diluent flow rate and specific heat correlated with NO reduction. The effects of diluents on calculated combustion temperature, mbt spark timing, and fuel consumption are also presented and discussed.

The effects of charge dilution on the exhaust emission of nitric oxide (NO) from a single-cylinder engine were evaluated over a range of engine design and operating parameters. Nitric oxide emission decreased as much as 70% as charge dilution fraction (volume fraction of product gases in the combustion chamber prior to ignition) was increased from 0.065 to 0.164 due to increased valve overlap, external exhaust recirculation, and reduced compression ratio. With these three variables, NO emission was strongly dependent on charge dilution fraction, but was independent of the specific method used to change charge dilution. Other variables such as valve overlap position, spark timing, and exhaust pressure also affected charge dilution and NO emission, but the relationship between charge dilution fraction and NO emission for these variables was not consistent.

Continuing Stirling engine development at General Motors has uncovered advantages of the powerplant never before fully appreciated. Smoke, odor, noise, and exhaust emission measurements indicate the attractiveness of the engine for applications in a “social” environment. Design details, particularly the external combustion system, are described here only in relation to low emission level. Measurements indicate that smoke and odor are practically undetectable. Sound measurements demonstrate the relative quietness of the engine. Additional data show that exhaust emissions, while very low, exhibit a strong dependence on burner design, air-fuel mixture ratio, burner inlet temperature, and exhaust recirculation.

Many methods of altering the composition of internal combustion engine exhaust gases have been considered for reducing automotive air pollution. By providing a low-energy reaction path, catalysis may be the most effective method of reducing automotive air pollution. Since chemical equilibrium represents the ultimate limit of catalytic treatment of engine exhaust, equilibrium compositions were determined for nine air-fuel mixtures, with overall air-fuel ratios (A/Fs) ranging 12: 1-17: 1 (lb air/lb fuel), for temperatures 300-1500 F. A NASA computation procedure based on free-energy minimization was used to determine the equilibrium concentrations. These calculations indicated that true equilibration of exhaust gases, in the temperature range considered, would nearly eliminate the major exhaust pollutants. No hydrocarbons (HCs), except nonreactive CH4, appeared in significant concentrations. Even at the leanest A/F considered, equilibrium NO concentrations were less than 30 ppm.

The objective of this paper is to give illustrative solutions for the types of combined structural and acoustic problems which arise in the finite element analysis of the automobile passenger compartment and to review related methodology. Analysis implementation using the NASTRAN (NASA STRuctural ANalysis) computer program is discussed briefly, including the use of modal compartment wall models and forced boundary conditions. The model is a two dimensional one, assuming a uniform pressure field in the cross-body direction. This simplification appears to be adequate for the frequency range of interest (20 to 80 Hz).

Theoretically, the combustion of homogeneous, lean air-fuel mixtures offers potentially low emissions with low fuel consumption. An experimental investigation of a lean-combustion engine system, equipped with a lean thermal reactor, was conducted with a 1130 kg (2500 lb) vehicle. The effects of spark timing on vehicle emissions, fuel consumption, and lean reactor performance were determined. Retarded spark timing decreased HC and CO emissions, did not affect NOx emissions, and increased fuel consumption. Over-advanced spark timing decreased CO emissions, increased HC and NOx emissions, and increased fuel consumption. The vehicle emission levels were very sensitive to spark timing changes and carburetor calibration repeatability. Thus, implementation of such a vehicle would require careful control of these engine variables.

An investigation has been made to determine the effects of the degree of fuel atomization on exhaust emissions, fuel consumption, lean limit, MBT spark timing, and cyclic variations in peak cylinder pressure. A single-cylinder engine was used to isolate the effects of atomization on combustion from the additional effects of maldistribution that would be present in a multicylinder engine. Three degrees of gasoline atomization were investigated, along with the case of a well-mixed charge of gaseous propane. The degrees of atomization investigated varied from “Good” (10-20 μm droplets) to “Bad” (400-700 μm droplets) to “Wall-Wetted” (400-700 μm droplets deposited on the intake-port walls). Results from this investigation show that the degree of atomization can have considerable effect on exhaust emissions, but little effect on fuel consumption.

A two-chamber bomb was used to investigate the effect of fluid motions on combustion characteristics, in particular exhaust emissions. Variations in prechamber volume, connecting orifice geometry, air-fuel charge stratification, and initial turbulence of the charge were examined. Tests were run over a wide air-fuel ratio range. High speed motion pictures were used to study flame propagation and fluid motions. The results show that when the strength of the turbulent jet from the prechamber is varied over a significant range, there is little or no effect on the emissions of oxides of nitrogen (NOx) over the entire air-fuel ratio range. Hydrocarbon (HC) emissions were found to increase with jet strength in the portion of the lean air-fuel range of most interest (i.e., around 17:1). However, for very lean mixtures the trend was reversed.

The concentrations of oxides of nitrogen (NOx = NO + NO2) in engine crankcases interest lubricant technologists because NOx reactions with fuel and lubricant components are partially responsible for engine deposits and oil deterioration. To provide information hitherto unavailable in the literature, concentrations of NOx and NO2 were measured in the crankcase gas of a multi-cylinder engine operated at a variety of steady-state conditions. The concentrations of NOx and NO2 measured in the crankcase gas followed the same trends with changes in engine operating variables as the concentrations of NOx and NO2 in the exhaust gas. Specifically, increasing intake manifold pressure, spark advance, and compression ratio, generally increased the concentrations of NOx and NO2. Increasing the percent exhaust gas recirculation, however, decreased NOx and NO2 concentrations.

Catalyst deterioration caused by phosphorus-containing engine oil additives was investigated using a variety of engine oil blends in a steady-state engine-dynamometer test. The reductions in hydrocarbon and carbon monoxide conversion in the 200-hour test were related to two parameters: 1) the quantity of phosphorus in the oil added to the engine, and 2) the amount of phosphorus on the catalyst at the end of the test. Catalyst degradation relative to the first parameter differed from that relative to the second because the two parameters were not directly related. Specifically, catalyst conversion efficiency decreased nonlinearly with the amount of oil-derived phosphorus added to the engine, but linearly with the amount of oil-derived phosphorus found on the catalyst. A higher percentage of phosphorus added to the engine was found on the catalyst with oils containing tricresylphosphate (TCP) than with oils containing zinc dialkyldithiophosphate (ZDP).

Single-cylinder engine tests, an analytical engine cycle simulation, and automobile tests were employed to study the effects of supplementing gasoline with water for use in spark ignition engines. Factors examined include: the method of water addition (both water-in-gasoline emulsions and direct manifold water addition), antiknock characteristics with water addition, MBT spark requirement, indicated engine efficiency, engine cooling requirement, exhaust emissions, volumetric efficiency, lean operating limit, smoke level, exhaust temperature, and vehicle driveability. Among the negative aspects of water addition were increased hydrocarbon emissions and decreased vehicle driveability. Also, the polyoxyethylene type of emulsifier used in the water-in-gasoline emulsions, gave poor fuel stability and caused a rapid buildup of engine deposits. However on the positive side, water-gasoline fuels have higher octane ratings and decrease nitric oxide emissions.

Exhaust emission and performance characteristics of a single-cylinder engine fueled with methanol are compared to those obtained either with gasoline or a methanol-water blend. Our measurements of engine efficiency and power, and CO and NOx emissions agree with trends established in the literature. Consequently, the emphasis is placed on organic emissions (unburned fuel including hydrocarbons, and aldehydes), an area in which there is no consensus in the literature. In all cases with methanol fueling, the unburned fuel (UBF) emissions were virtually all methanol as opposed to hydrocarbon compounds. Without special measures to overcome methanol's large heat of vaporization, UBF emissions were four times greater with methanol than those with gasoline. Similarly, aldehyde emissions were an order of magnitude greater with methanol.

The purpose of this paper is to present a comparison of whole body, target impingement knee impact response for a Part 572 dummy versus that for anthropometrically similar embalmed human cadavers. “Response” is defined here to include the impact force-time history as sensed by 1) femur load cells, and 2) impingement target load cells for the dummy and by the target load cells for the cadavers. The data presented demonstrate significantly higher peak forces and correspondingly shorter pulse durations for the dummy than for the companion cadaver subjects under similar test conditions and at all velocity levels investigated. For the dummy, the ratio of forces measured by the femur load cells to those measured by the impingement target load cells averaged eight tenths.