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A new analytical method, absorption of tunable diode laser radiation, can detect small concentrations of gases with fast response. This technique has been applied to the detection of vehicle sulfate emissions in the form of sulfuric acid (H2SO4) vapor. Previously available methods for sulfate analysis required collecting samples for 10 min. or more. Our laser system has a response time of 2.4 s. This allowed tracking the sulfate emissions of a vehicle during a Highway Fuel Economy Test. The data suggests that catalyst temperature is the major parameter controlling sulfate emissions and that storage and release of sulfur occurs at low and high catalyst temperatures, respectively. The same method detected methane during both the Highway Fuel Economy Test and the Federal Test Procedure. It identified the conditions, and corresponding concentrations, for high methane emissions. A qualitative comparison with total hydrocarbon emissions uncovered significant differences during accelerations.

An apparatus was developed for the determination of the engine oil contribution to both total and extractable particulate exhaust emissions from diesel-powered vehicles during cyclic operation on a chassis dynamometer. For the five vehicles tested, the percentage of the total particulate material that was derived from engine oil ranged from 7 to 14%. Between 14 and 26% of the total particulate material was extractable with benzene-ethanol (80-20) solvent. Oil contributed from 30 to 55% of the extractables in most cases. Engine design and oil formulation generally appeared to have only small effects on the oil contribution to the particulate emissions. A 1982 model-year vehicle with a 1.8L engine was an exception, since its oil contribution to the total and especially to the extractable particulate emissions (14 and 95%, respectively) was significantly greater than for any of the other vehicles.

The axially stratified-charge (ASC) concept was demonstrated in a compact production car by modifying the engine and developing the required control system and calibration. Two production 1.8 L four-cylinder engines were modified to operate as ASC engines by adding shrouded inlet valves to produce swirl, and by providing timed-sequential port fuel injection. One of these engines was calibrated for minimum fuel consumption in the laboratory using a computer-controlled engine and dynamometer. The second engine was installed in a vehicle equipped with an oxidizing catalyst. A complete control system was developed for this engine to implement the minimum fuel consumption calibration in the vehicle. The fuel economy of the ASC vehicle was six percent better than that of the base vehicle. It had acceptable driveability, and had a 91 Research octane requirement on the fuel.

Relative roles of premixed and diffusion burning in diesel combustion have been examined in terms of characteristic times for ignition delay (τig), combustion (τc) and fuel-air mixing (τm). Results indicate that the majority of the diesel combustion process is diffusion controlled, as in gas turbine combustion, since τc << τm over the entire range of operating conditions. During the ignition phase, some premixed burning can occur in the fringe of the fuel spray where τm < τig; however, most of the fuel injected prior to ignition also burns in the diffusion mode, since τm > τig in the majority of the fuel spray. The fraction of premixed burning which occurs during the ignition phase is increased by longer τig, high rates of fuel injection, high air swirl and the use of multi-hole injectors, which increase the surface area of the spray.

The state of California has adopted a “real-time” evaporative emission procedure that will be used starting with the 1995 model year. This test, which focuses on high temperature conditions, and measures all sources of evaporative emissions, represents a very stringent requirement. Non-fuel background emissions, i.e., paint, adhesives, and even air conditioning refrigerant, can be a significant fraction of the total measured emissions. California has included a provision in their regulations that allows for the subtraction of background emissions, using a methodology to be developed in the future. This paper reviews the history of non-fuel emission regulations, provides data showing the magnitude of the problem using the new real-time procedure, and suggests a methodology for establishing a new background emission test procedure.

A new aluminum alloy bearing material containing lead-base babbitt is described. This material provides the performance advantages of an overplated babbitt construction without requiring the plating procedure. Performance characteristics including fatigue, wear, score, and corrosion resistances and embedability are compared to standard SAE bearing materials on the basis of laboratory tests. Extensive engine dynamometer and vehicle field tests are described to show the excellent durability of this new material.

The flow of oil into a rotating crankshaft has been investigated. Analysis of the physics of the problem together with dimensional analysis indicates, for a given journal geometry, that a relationship exists between Reynolds number, non-dimensionalized pressure drop, and oil flow. Data obtained from an oil flow test rig are used to determine explicit correlations for two oil feed configurations; one journal with and one journal without a lead-in groove.

Previous studies of human thoracic injury tolerance and mechanical response to blunt, midsternal, anteroposterior impact loading were reported by the authors at the 1970 SAE International Automobile Safety Conference and at the Fifteenth Stapp Car Crash Conference. The present paper documents additional studies from this continuing research program and provides an expansion and refinement of the data base established by the earlier work. Twenty-three additional unembalmed cadavers were tested using basically the same equipment and procedures reported previously, but for which new combinations of impactor mass and velocity were used in addition to supplementing other data already presented. Specifically, the 43 lb/11 mph (19.5 kg/4.9m/s) and 51 lb/16 mph (23.1 kg/7.2 m/s) conditions were intercrossed and data obtained at 43 lb/16 mph (19.5 kg/7.2 m/s) and 51 lb/11 mph (23.1 kg/4.9 m/s).

Elimination of the conventional cooling system of a diesel engine and the incorporation of structural ceramics for the combustion chamber continues to receive attention worldwide. Application of this concept for a light-duty diesel engine installed in an intermediate-size passenger car is analyzed by computer simulation. The fuel economy of a water-cooled turbocharged DI diesel engine installed in a vehicle is compared to the fuel economy of low-heat-rejection (LHR) turbocharged and turbocompounded DI diesel engines. Appropriate consideration is given for the differences in loading imposed by the vehicle with displacement scaled for equal vehicle acceleration performance. On a combined EPA fuel economy basis, the LHR turbocharged engine is estimated to give 6% better fuel economy and the LHR turbocompounded engine is estimated to give 13% better fuel economy in the LHR vehicle in comparison to the water-cooled turbocharged engine in the baseline vehicle.

SAE 1046 steel axle I-beam forgings produced by the direct quench method and the conventional reheat and quench method were examined. Impact and tensile specimens obtained from sections of two direct quench and one conventional reheat and quench axle I-beams were tested. These data were correlated with hardness and microstructure to determine the relationship between microstructure and properties. The microstructure of direct quenched beams is coarse grained with a martensite case and bainite core. In contrast, the microstructure of conventionally heat treated beams is fine grained with a martensite and/or bainite case and pearlite core. Tensile and impact properties indicate that direct quenching is an acceptable alternative to the conventional reheat and quench process. Fatigue testing of direct quenched beams is currently being performed.

A NEW BARRIER to higher compression ratios has recently become apparent — engine rumble! This phenomenon will prevent further increases in compression ratio unless corrective measures are taken. This paper describes the phenomena of engine rumble not only in terms of the noise and vibrations that emanate from the engine but also in terms of the pressure development inside the cylinder. Rumble is the result of abnormally rapid pressure buildup in the combustion chamber due to multiple ignition of the fuel-air mixture by glowing deposits. Since deposits are responsible for the occurrence of engine rumble, studies have been made to determine the contribution of various gasolines and oils to the rumble tendency of the deposits formed. Results from dynamometer and road tests show that combustion-chamber deposits formed by the use of some oils and fuels are considerably less likely to cause rumble than deposits from others.

The General Motors Research Library online catalog provides electronic access to traditional library materials (books and journals), access to company documents (internal reports and product information), an alerting service, and links to non-bibliographic information. The Library also offers an online literature searching service as a supplement to the online catalog.

The effects of changing the intake-O2 mole fraction on the emissions of gaseous and particulate-bound hydrocarbons (HC and volatiles, respectively) have been examined using low- and high-swirl prechamber diesel engines. HC and volatile emissions indices increased with decreasing O2 mole fraction. For most of the test conditions, the effect of intake-air composition on both of these emissions could be explained by variations in the calculated stoichiometric flame temperature, implying that the combustion process in the engines considered was mainly diffusion-controlled. The results also indicated that, at certain operating conditions, a significant fraction of the volatile matter was contributed by sources unrelated to the main combustion event.

A single-cylinder engine was used to study the effect of engine operating parameters on the early stage of deposit formation (first 8 hours). Deposit samples were collected from the engine cylinder using removable sampling probes. Among the engine operating parameters studied, coolant temperature had the greatest influence on deposit formation. Equivalence ratio of the air-fuel mixture was also important. Other variables such as compression ratio and intake air temperature had minimal effects. Investigations using a temperature controlled probe revealed that surface temperature is a dominant factor in the deposit forming process. Within a temperature range from 98°C to 256°C, there is an inverse relationship between the amount of deposit accumulated and the surface temperature. Extrapolating the experimental data showed that the critical surface temperature for deposit formation is near 310°C, above which no deposit is expected to form.

Engine and chassis dynamometer tests were conducted using the GMR GT-225 experimental automotive gas turbine engine to determine the effect of fuel nitrogen on NOx emissions. Kerosene doped with pyridine was used as fuel and both a conventional diffusion-flame combustor and an experimental lean, premixing-prevaporizing combustor were tested. The results show that a sizable amount of fuel nitrogen is converted to NOx with both combustors. The lean, premixing-prevaporizing combustor converted a greater fraction of the fuel nitrogen than did the diffusion-flame combustor and for both combustors, the fraction converted decreased as the fuel nitrogen content increased.

Multidimensional computations were made of spark-ignited premixed-charge combustion in a pancake-combustion-chamber engine with a centrally located spark plug and in two pent-roof-chamber engines, one with a central spark plug and the other with dual lateral spark plugs. A global combustion submodel was used that accounts for laminar kinetics and turbulent mixing effects. The predictions were compared with available measurements in the pancake-chamber engine over a range of loads, speeds, and equivalence ratios. In all cases the computed and measured cylinder pressures agreed well in trends and magnitudes (within 8%) for the entire duration of combustion. Fair agreements were also obtained between predicted and measured values of wall heat flux and emission index of nitric oxide. In the pent-roof-chamber engines the predicted maximum cylinder pressures also agreed well with measurements (within 12%) in cases with MBT (Minimum spark advance for Best Torque) or advanced spark timing.

The influence of flame temperature on NOx, particulate and hydrocarbon emissions from a single-cylinder light-duty direct-injection diesel engine was examined by varying the composition of the intake air with the engine operating at different speeds and loads. At a fixed engine speed, load, and start-of-combustion timing, the effects of intake-gas composition on emissions were found to correlate with variations in the characteristic diffusion flame temperature. Furthermore, this flame temperature dependence was not significantly affected by the engine operating conditions. These results indicate that the flame temperature correlations originally developed for divided-chamber diesel engines can be applied to direct-injection diesel engines.

A two-stage heat-release model was developed and applied to both a divided-chamber and an open-chamber diesel engine to determine the fuel burning rates and product temperatures from measured cylinder pressure-time profiles. Measured NO emission levels for several engine operating conditions were used to select the equivalence ratios of the two stages. Combustion in the first stage was taken to occur at a stoichiometric air-fuel ratio, while second-stage combustion was considered to occur at an equivalence ratio below the cylinder-averaged equivalence ratio. An empirical fit for the equivalence ratio of the second stage was determined. Good agreement between the results of this model and the corresponding single-stage model was obtained for heat-release and heat-transfer histories. The computed combustion temperatures for the rich stage were found to be consistently higher (7 to 22% on an absolute scale) than published flame-temperature measurements.

Interlaboratory comparisons of extraction and chemical characterization are reported for exhaust particulate from heavy-duty diesel engines, typical of the 1980s. This study is the final of a series conducted by member companies of the Coordinating Research Council on methods and measurements to expand knowledge about unregulated constituents of diesel-engine exhaust. Exhaust particulate from heavy-duty diesel engines of the 1980s averaged about 25 wt% extractable by methylene chloride. In engine-to-engine comparisons, the extractable fraction correlated with the ratio of total engine hydrocarbon to nonextractable carbon particulate. These comparative studies demonstrate methods for monitoring changes in the composition of diesel particulate that may occur as stringent emission standards are implemented in the 1990s.

A free-piston engine hydraulic pump (FPEHP) is considered as a power source in the propulsion system of an automotive vehicle. The propulsion system uses a two-stroke spark-ignited free-piston engine coupled to a hydraulic pump and an accumulator where high pressure hydraulic fluid is stored for transmission of power. The energy in the accumulator is transmitted to hydraulic motors which provide the tractive effort. A mathematical model was developed for the FPEHP and computer simulation studies were performed. A particular free-piston engine hydraulic pump concept was simulated at various operating conditions and compared with a similarly-sized conventional engine. We can conclude that the FPEHP engine has no thermodynamic advantage over a conventional engine, but there are reduced nitric oxide emissions. Also, the FPEHP has a limited range of engine speed and a narrower range of ignition timing than a conventional engine.