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Technical Paper

Diesel Combustion Chamber Sampling - Hardware, Procedures, and Data Interpretation

1975-02-01
750849
In-cylinder sampling appears to be the only available means for obtaining detailed information of the diesel combustion process. This information is necessary to understand pollutant formation because of the intimate relationship between formation rates and local cylinder conditions. This paper discusses efforts to (1) examine and improve sampling valve design, (2) evaluate potential effects of the valve and the sampling system on sample composition, (3) find methods to extract useful information from sampling data. Sampling hardware is currently being used to study combustion in engines, but further work is needed to quantify the influence of hardware and procedures on sample composition and to design experiments to provide data containing maximum information.
Technical Paper

A Rotary Engine Test to Evaluate Lubricants for Control of Rotor Deposits

1974-02-01
740159
During development of the General Motors rotary engine, the lubricant was recognized as important to its success because certain lubricants produced deposits which tended to stick both side and apex seals. Consequently, it was decided to develop a rotary engine-dynamometer test, using a Mazda engine, which could be used for lubricant evaluation. In an investigation using an SE engine oil with which there was rotary engine experience, engine operating variables and engine modifications were studied until the greatest amount of deposits were obtained in 100 h of testing. The most significant engine modifications were: omission of inner side seals, plugging of half the rotor bearing holes, pinning of oil seals, grinding of end and intermediate housings, and using a separate oil reservoir for the metering pump. Using this 100 h test procedure, three engine oils and five automatic transmission fluids were evaluated.
Technical Paper

Emission Control with Lean Operation Using Hydrogen-Supplemented Fuel

1974-02-01
740187
Hydrogen-supplemented fuel was investigated as a means of extending lean operating limits of gasoline engines for control of NOx. Single-cylinder engine tests with small additions of hydrogen to the fuel resulted in very low NOx and CO emissions for hydrogen-isooctane mixtures leaner than 0.55 equivalence ratio. Significant thermal efficiency improvements resulted from the extension beyond isooctane lean limit operation. However, HC emissions increased markedly at these lean conditions. A passenger car was modified to operate at 0.55-0.65 equivalence ratio with supplemental hydrogen. Vehicle emissions, as established by the 1975 Federal Exhaust Emissions Test, demonstrated the same trends as the single-cylinder engine tests. The success of the hydrogen-supplemented fuel approach will ultimately hinge on the development of both a means of controlling hydrocarbon emissions and a suitable hydrogen source on board the vehicle.
Technical Paper

Design and Development of a Variable Valve Timing (VVT) Camshaft

1974-02-01
740102
The development of a variable valve timing (VVT) camshaft was initiated as a potential means of controlling exhaust emissions from a spark ignition piston engine. This approach was based on the fact that valve overlap influences internal exhaust gas recirculation which in turn affects spark ignition engine emissions and performance. The design, fabrication, bench tests and engine durability tests of a unit incorporating splines to allow the intake cams to move relative to the exhaust cams is discussed. Preliminary test data from a 350 CID (5700 cm3) engine fitted with the VVT camshaft are discussed with regard to durability and emissions.
Technical Paper

Effects of Engine Oil Composition on the Activity of Exhaust Emissions Oxidation Catalysts

1973-02-01
730598
Platinum, palladium, and copper-chromium oxidation catalysts for exhaust emission control were exposed to exhaust gases from a steady-state engine dynamometer test in which the amount of oil consumed per unit volume of catalyst was high. When unleaded gasoline (0.004 Pb g/gal, 0.004 P g/gal) was used, conventional SE oil caused somewhat greater loss of catalyst activity than an ashless and phosphorus-free (“clean”) oil. Chemical analysis of the catalyst indicated that phosphorus from the conventional oil was probably responsible for the difference. However, a test run with low-lead (0.5 Pb g/gal, 0.004 P g/gal) gasoline and “clean” oil caused much greater catalyst activity deterioration than either of the tests with unleaded gasoline.
Technical Paper

Effects of Spark Location and Combustion Duration on Nitric Oxide and Hydrocarbon Emissions

1973-02-01
730153
This study describes the effect of spark plug location on NO and HC emissions from a single-cylinder engine with a specially modified combustion chamber. The effects of changes in combustion duration caused either by spark location, dual spark plugs, or charge dilution on NO and HC emissions were also examined. Experiments were run at constant speed, constant load, and mbt spark timing. Nitric oxide emissions were the same with the spark plug located either near the intake or exhaust valve, but were higher with the spark plug midway between the valves or with dual ignition. Hydrocarbon emissions were lowest with the spark plug nearest the exhaust valve and increased with the distance of the spark plug from the exhaust valve. With charge dilution the decrease in NO emission was isolated into a pure dilution effect and a combustion duration effect. The combustion duration effect was minimal at rich mixtures and increased with air-fuel ratio.
Technical Paper

Initial Oxidation Activity of Noble Metal Automotive Exhaust Catalysts

1973-02-01
730570
The use of relatively small catalytic converters containing alumina-supported platinum (Pt) and palladium (Pd) catalysts to control exhaust emissions of hydrocarbons (HC) and carbon monoxide (CO) was investigated in full-scale vehicle tests. Catalytic converters containing 70-80in3 of fresh catalyst were installed at two converter locations on the vehicle. Carburetion was richer than stoichiometric, with air-fuel ratios (A/F) comparable to those proposed for dual-catalyst systems containing an NOx reduction catalyst. The vehicle was equipped with exhaust manifold air injection. Homogeneous thermal reaction in the exhaust manifolds played a significant role in the overall control of HC and CO. Four Pt catalysts, three Pd catalysts, and one Pt-Pd catalyst were prepared and evaluated. Total metal loadings were varied 0.01-0.07 troy oz. Hydrocarbon conversion efficiencies varied 62-82%, measured over the 1975 cold-hot start weighted Federal Test Procedure.
Technical Paper

Continuous Secondary Air Modulation - Its Effect on Thermal Manifold Reactor Performance

1973-02-01
730493
Secondary air scheduling and average delivery rate have a great influence on the performance (carbon monoxide and hydrocarbon cleanup) of rich thermal manifold reactors. A continuously modulated secondary air system was devised to provide a tailpipe air-fuel ratio that did not change significantly with engine speed or load when a “flat” carburetion calibration was incorporated. This system involved throttling the inlet of the air pump(s) so that the air pump and engine intake pressures were equal. The continuous air modulation system was compared with an unmodulated system and a step-modulated system. The secondary air systems were investigated with both GMR “small volume” cast iron thermal reactors and Du Pont V thermal reactors on modified 350 CID V-8 engines in 1969 Chevrolet passenger vehicles. It was found that thermal reactor performance improved with each increase in control of the secondary air schedule.
Technical Paper

The Relationship of Low-Temperature Rheology to Engine Oil Pumpability

1973-02-01
730478
An analysis of oil pumpability reveals that engine oil pumping failures may occur because either the oil cannot flow under its own head to the oil screen inlet, or the oil is too viscous to flow through the screen and inlet tube fast enough to satisfy pump demands. To determine which factor is controlling, the behavior of commercial, multigraded oils was observed visually at temperatures from -40 to 0°F (-40 to - 17.8°C) in a laboratory oil pumpability test apparatus. Test results revealed that pumping failures occur by the first alternative: a hole is formed in the oil, and the surrounding oil is unable to flow into the hole fast enough to satisfy the pump. Of 14 oils tested, 7 failed to be pumped because of air binding or cavitation which developed in this manner. A model, which explains these failures in terms of yield point considerations and the low shear apparent viscosity of the oils, is proposed.
Technical Paper

Correlation of Physical Properties with Performance of Polyacrylate Radial Lip Seals at -30F

1973-02-01
730051
This paper evaluates the tendency of lip seals to fracture in a test apparatus in which dynamic runout is 0.010 in and the temperature is cycled between -30 and 0 F. Seals made of eight different polyacrylate polymers were soap-sulfur cured with various types and amounts of carbon black. Physical tests included room-temperature flexibility defined by Young's modulus at small strains, standard tensile tests at room temperature, flexibility at sub-zero temperatures determined by a Gehman test, and sub-zero starting torques of the seals. Primary determinant of successful fracture resistance is a low starting torque resulting from good low-temperature flexibility. The effect of adding graphite to some of these formulations is described and some current commercially available seals are evaluated.
Technical Paper

Some Factors Affecting Gas Turbine Passenger Car Emissions

1972-02-01
720237
The intent of this paper is to put into proper perspective the relationships among the vehicle, the thermodynamic cycle, and the combustion process as they relate to exhaust emissions from a gas turbine-powered passenger car. The influence of such factors as car size, installed power, regeneration, and other cycle variables on level road load fuel economy, and on the production of oxides of nitrogen and carbon monoxide, are examined. In limited checks against experimental data, the mathematical model of the combustor used in this study has proved to be a reliable indicator of emission trends. The calculated emission levels are not final, however, with deficiencies subject to improvement as new combustor concepts are developed.
Technical Paper

The Turbine Interstage Diffuser

1971-02-01
710553
The incentive for use of an interstage diffuser in a free-shaft gas turbine engine is briefly examined and some pertinent published background data reviewed. Tests of two annular diffusers behind an upstream turbine show the deleterious effects of turbine exit flow nonuniformity on diffuser behavior. The flow acceleration provided by the area contraction of a power turbine nozzle located at the diffuser exit substantially improves the nature of the flow previously found to exist at the diffuser exit in the absence of the nozzle.
Technical Paper

Effect of Combustion Chamber Surface Temperature on Exhaust Hydrocarbon Concentration

1971-02-01
710587
The relationship between surface temperature and exhaust hydrocarbon concentration was explored by installing surface thermocouples at three locations in the combustion chamber of a single-cylinder engine. Coolant temperature, coolant passage surface scale, and ethylene glycol in the coolant affected exhaust hydrocarbon concentration through changes in surface temperature. As power output increased, combustion chamber surface temperature rose, and exhaust hydrocarbon concentration fell. The increase in surface temperature accounted for about 43% of the decrease in hydrocarbon concentration. The reason for the other 57% of the decrease is unknown, but it may have been caused by increasing gas temperatures in the quench zone. Increasing surface temperature by engine modification would be expected to have adverse effects on engine octane requirement, volumetric efficiency, and oil oxidation.
Technical Paper

General Motors' Steam-Powered Passenger Cars - Emissions, Fuel Economy and Performance

1970-02-01
700670
Two steam-powered passenger ears have been designed, built, and tested. The SE-101 is an intermediate sport coupe incorporating the comfort and convenience features of a modern passenger car and vehicle performance comparable to a low-powered automobile. The SE-124 is a very low-power intermediate sedan with manual start and semiautomatic control. The characteristics of these cars were evaluated relative to the operational requirements of current transportation needs, with particular emphasis on exhaust emissions. Start-up time, exhaust emissions, fuel economy, acceleration, and water consumption data are presented. Although any one of these characteristics may be improved at the expense of others, it does not appear that any compromise can satisfy all of the areas required by today's motorist.
Technical Paper

A Combustion System for a Vehicular Regenerative Gas Turbine Featuring Low Air Pollutant Emissions

1967-02-01
670936
The combustion system developed for the General Motors GT-309 regenerative gas turbine is used to illustrate pertinent structural, performance, and exhaust emission considerations when designing for a vehicular gas turbine application. The development of each major component and the performance of the combustion system as a whole are reviewed. The satisfactory performance and durability potential of the GT-309 engine combustion system have been demonstrated by extensive operation in a component test facility and in several test cell and vehicle installed engines. Exhaust emissions of unburned hydrocarbons and carbon monoxide are minimal and are of no concern from an air pollution standpoint. No objectionable exhaust smoking and odor are produced.
Technical Paper

Numerically Controlled Milling for Making Experimental Turbomachinery

1967-02-01
670096
Utilization of numerically controlled milling has been found particularly attractive in producing, in limited quantities, the three-dimensional curved surfaces characteristic of turbomachinery. In experimental and developmental programs its use can result in decreased fabrication cost, reduced lead time, and improved dimensional accuracy. Following a review of the general classifications of numerically controlled milling machines available for manufacture of such parts, illustrations are given of some of the procedures and techniques employed in their use. A variety of parts made using numerical control serve as examples.
Technical Paper

Digital Data Acquisition and Computer Data Reduction for the California Exhaust Emission Test

1966-02-01
660406
The tedious, time consuming task of hand reducing data from the California exhaust emission test has been alleviated through the use of digital data acquisition equipment and a digital computer. Analog signals from exhaust gas analyzers and an engine speed transducer are converted to digital measurements which are recorded on tape and submitted to a digital computer for data analysis and computation of results. In the data analysis, the computer identifies the required driving modes from engine speed changes, taking into account the sample delay time. “Reported” composite emissions determined by the automatic data reduction method agree within 5% with results determined by careful hand analysis of analog strip chart recordings. The results determined by the automatic data reduction system are more consistent and accurate because human errors prevalent in hand analysis have been eliminated, and because nonlinear analyzer response is accounted for.
Technical Paper

The GMR Sealometer A New Machine for Oil Seal Evaluation

1966-02-01
660381
The Sealometer is used for evaluating the performance of lip type oil seals and provides a dimensionless number derived from measuring the increase in temperature of a test shaft operating in a lip seal for a given time interval. With the Sealometer it is possible to study parameters that affect seal performance. As a quality control instrument, the machine provides accurate data for design. Sealometer evaluation offers a quick method of determining the life expectancy of a particular design for a particular application and eliminates the need for long life test programs.
Technical Paper

Evaluating the Effect of Fluids on Automatic Transmission Rotating Shaft Seal Elastomers

1966-02-01
660396
The Total Immersion Test (ASTM D 471) for seal elastomers, used in evaluating the compatibility of fluids and seals for automatic transmissions, does not, produce hardness and volume change results similar to those found for rotating shaft seals in service. The Tip Cycle Test was devised to provide better agreement with service results. In the test, one side of the seal is exposed to air, and the other alternately to fluid and to air-fluid vapor. Rotating shaft seals were evaluated in both car and dynamometer transmission tests, and in various bench tests. Agreement was poor between transmission tests and both the Total Immersion and the Dip Cycle Tests. Good agreement was found with the Tip Cycle Test.
Technical Paper

Fluid Composition Affects Leakage from Automatic Transmissions

1966-02-01
660397
Tests were conducted using older model cars with automatic transmissions to determine the effect of fluid composition on leakage past the rotating shaft seals. It was found that seal leakage was reduced or stopped by changing to seal-swelling fluids, and increased with seal-shrinking fluids. Leakage was also reduced by adding aromatic additives to existing fluids in the transmissions. Seal volume and hardness change results from bench tests support the car data.
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