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The adverse effects of charge dilution on combustion of spark ignition engines are well known; as a tool for reduction of nitrogen oxide emission, it becomes important. Some methods of analyzing combustion phenomena in a single-cylinder engine (27.1 CID) with charge dilution were tried. Multiple ionization probes roughly indicate the pattern of flame propagation, but details of the flame, especially charge dilution, cannot be measured by this method. Flame photographs, on the other hand, showed clearly the effects of combustion chamber design on flame propagation and its cyclic dispersion. The effects of combustion chamber configuration, ignition energy and spark duration, ignition timing, composition of diluent gas, air-fuel ratio, and mixture homogeneity were examined. Mass burnt fraction was calculated from both flame photographs and pressure indicator diagrams.

This paper discusses the Mercedes-Benz V-8 engines, their design as compared to US V-8 engines, and development concerning exhaust emission control and fuel consumption. Also covered are special problem areas, and their respective solutions which today have come to be of secondary importance, for example, the lubrication system, defoaming of the lubricant, noises generated by the lubrication system, and the adaptation of the hydraulic valve clearance adjustment to high engine speeds.

Normal means of reducing vehicle fuel consumption, such as lower speeds, shorter trips and proper maintenance, are well known. This paper reviews a number of other, lesser known, fuel conservation measures this paper includes practical recommendations for their application and cites results that may be achieved.

The California Legislature conducted an investigation into the low emission properties of steam-powered automobiles, 1972-74. Two steam propulsion systems were built and installed into sub-compact cars suitable for urban driving. The Aerojet Liquid Rocket Co. installed a steam turbine in a Chevrolet Vega, while Steam Power Systems built a piston engine system for a car of special design. The project demonstrated that it is possible to reduce exhaust emission levels to less then those required by the 1978 Federal standards. Road performance was adequate for urban-suburban driving. Fuel consumption was higher than comparable internal combustion-powered vehicles. Guidelines for future improvements are given.

The Rankine cycle engine is being considered as an alternative to the emission controlled spark ignition automobile engine, primarily because of the promise of inherently low emissions. Much of this promise is beginning to become reality. The development of combustors for Rankine cycle engines has progressed to the point where very low steady state emissions have been demonstrated for several combustor designs. In addition, the original 1976 emissions standards have been met in several motor vehicles powered with Rankine cycle powerplants.

A three-way correlation study of aerodynamic pressure measurements has been carried out between the MIRA model and full-scale wind tunnels and actual road conditions. Six vehicles and two quarter-scale models were used, each fitted with 30 or more static pressure tubes and tappings connected to a multi-tube manometer. The results showed close correlation between full-scale tunnel and road measurements, though apparently with a smaller blockage effect than previously assumed. Good correlation was also found between model and full-scale tunnel measurements, provided a high standard of accuracy was maintained in the model manufacture.

The Cumulative Damage Division of the SAE Fatigue Design and Evaluation Committee recently finished an extensive fatigue test program. This test program involved one Keyhole test specimen, two different materials, three loading spectrums and the cooperation of eight test laboratories to run the 58 specific fatigue tests. The objective of the overall division program was to determine the state-of-the-art of cumulative damage life prediction capability using the experimental data for correlation. This work reports a finite element and damage analysis of the Keyhole test specimen. The calculated notch root strain was compared with the experimental strain. The calculated stress and strain were used in a cumulative damage procedure to predict life for both materials subjected to various load levels for each of three loading spectrums. The results of the theoretical life predictions are compared to the experimental results.

Three computer programs are presented for predicting the fatigue life of notched members undergoing complex load histories. The programs, while differing in terms of required information, employ a common approach involving the determination of the material response at the notch root, an assessment of damage based on closed hysteresis loops, and a linear damage summation to predict life. Agreement between predictions and experimental results generated by the SAE Fatigue Design and Evaluation Committee is reasonably good. The programs have purposely been kept simple to allow for easy modification. Applications and limitations of the three programs are discussed.

Results of the SAE Fatigue Design and Evaluation Committee, Cumulative Damage Division test program are reported. This includes a description of the test specimen geometry, variable amplitude load histories, material properties and fatigue data. The data set produced can be used to generally evaluate methods of fatigue life prediction and laboratory simulation.

Chevrolet's automatic truck cab spot-welding facility has several features that make it unique in the automobile industry. The mechanical complexity, computer control system, and physical size of the facility help to increase quality and productivity.

By calculating the cooling rate during quenching and calculating Ms temperatures from measured carbon contents and carbide quantities in depth, curves indicating the time at which transformation began in cylindrical specimens were determined. Using these curves, measured residual stress distributions were analyzed. Transformation started at a depth near the carburized case-core boundary, determined by the carbon gradient and cooling rate. It then proceeded out to the case and into the core, generating high internal stresses in these areas. The sequence of transformation was responsible for oscillations in the final residual stress distribution, with maximum compression occurring outside the case-core boundary.

A TRIAXIAL AUTOMOTIVE WHEEL FORCE AND MOMENT TRANSDUCER A transducer capable of simultaneously measuring the dynamic forces and moments acting on the front or rear wheel of an automotive vehicle has been jointly developed by Ford Motor Company and GSE, Inc. This transducer was designed to be used on passenger cars with 13, 14, or 15 inch wheels. It is adaptable to laboratory wheel and tire testing machines. An instrumentation package that provides electrical excitation, signal conditioning, and cross-talk compensation for the transducer was also developed. The operational features of the transducer and the transducer instrumentation package as well as an assessment of some of its applications will be presented using functional block diagrams. Specifications for the system are listed and calibration data and road evaluation data will also be presented.

The effect of prestraining on the tensile properties and uniaxial low cycle fatigue behavior of SAE 1008 hot rolled low carbon steel strip has been investigated using a prestraining technique which simulates a press forming operation. Preliminary data for the case of a 40% balanced biaxial prestrain show a considerable increase in fatigue resistance in the long life regime. The reduced ductility as a result of prestraining, however, causes degradation of the short life fatigue resistance. Therefore, for component operation in the long life regime where the strains are mainly elastic, SAE 1008 may have considerably greater fatigue resistance than a designer would anticipate based on the yield and ultimate strength levels or fatigue data of the as-received material.

Two cycle counting algorithms, based on Range Pair and Rainflow methodologies, are quantitatively compared using three typical automotive load histories. Both algorithms were found to produce essentially equivalent counted spectra based on the resultant amplitude exceedance data. Because of the output format, the range pair algorithm is generally recommended for applications requiring damage accumulation calculations and spectrum analysis. The rainflow algorithm is recommended for applications involving cycle counting of arbitrary duration field load histories.

Using linear elastic fracture mechanics concepts, two steels quenched and tempered to Rockwell C 40-47 were evaluated for application in crawler tractor main frames. These high strength steels were D6-B and an experimental steel whose chemistry was optimized using a digital computer procedure referred to as the CHAT system, an acronym standing for Computer Harmonized-Application Tailored. Fatigue crack growth rate da/dN versus ΔK for constant amplitude loading and plane strain fracture toughness KIc parameters were determined from compact specimens. These parameters together with approximate stress intensity calculations were utilized to estimate component fatigue crack growth life assuming various initial crack sizes. These estimations were compared with accelerated component fatigue life, which included both crack initiation and crack growth.

This paper presents predictions of fatigue crack initiation life for three distinctly different, irregular load histories, each applied to keyhole-notched compact tension specimens at several maximum load levels and using two different structural steels. Work leading to this paper was done in conjunction with the cooperative research program of the SAE Fatigue Design and Evaluation Committee. Three computerized prediction methods (Landgraf, Wetzel, and a Nominal Stress Range approach) are used. All predictions are based on load histories condensed to 10% of their original number of reversals by the “Racetrack Method.” This method, which is described in detail, selects the most damaging overall ranges in an irregular load history while preserving the sequence of the original loading. Predictions are compared with test data for the two dozen combinations of loading type and level and steel used. Comments are made on the relative merits of the different prediction methods.

Severe corrosion was observed in the neck area of Inconel 751 material exhaust valves operated in an ebulient-cooled natural gas engine. The type of corrosion was identified as sulfidation attack. Deposits removed from the valves consisted mainly of calcium sulfate (CaSO4) from oil additives and carbon (C) residue from combustion products. Experimentation showed that the presence of C was a necessary pre-requisite for attack. Based on this information, the corrosion mechanism must involve the reduction of the sulfate by C. The reduction of the sulfate results in a high sulfur chemical potential at the alloy surface making transport of sulfur into the substrate a highly favored step. Aluminizing the Inconel 751 material proved to be an effective deterrent against sulfidation attack.

THREE SIMPLIFIED PROCEDURES for predicting fatigue life are compared with actual test results. The part geometry, load histories, material properties, and test results used in these analyses were obtained from the SAE Fatigue Design and Evaluation Committee's Cumulative Fatigue Damage Test Program (1)*. The purpose of this effort is to evaluate the relative accuracy and applicability of these frequently used methods.

Single-cylinder experiments were conducted with a 3-valve carbureted pre-chamber stratified charge engine in comparison with a conventional engine. The pre-chamber engine operation is governed by many design and operating variables. This investigation was limited to determining the effect of overall air/fuel ratio, ignition timing and EGR on emissions and fuel economy at a single road load test condition. It was found that, as for the conventional engine, these operating variables are also significant for the pre-chamber engine and that a compromise must be made between good fuel economy and low emissions. The main virtue of the pre-chamber engine was found to be the ability to operate at leaner overall air-fuel ratio. This resulted in lower nitrogen oxide (NO) emissions than the conventional engine without EGR. The unburned hydrocarbons (HC) were found to be higher for the pre-chamber engine up to the conventional engine lean misfire A/F ratio.

Experimental work is carried out to investigate the importance of the connecting nozzle between the auxiliary and the main chambers and the ignition point location to the performance of a stratified charge spark ignition engine using Broderson's method of charge stratification. Thre different nozzle configurations and two ignition point locations were used in the present experiment. The study shows that the fuel economy obtained with this approach is dependent upon the nozzle geometry which also plays an important role in the combustion noise generation, a characteristic of this method. The results show good fuel consumption over the entire range; the analytical work on the combustion of the mixture in the auxiliary chamber indicates that flame initiation near the center of the nozzle opening has a potential of restricting the flow of unburned mixture in the main chamber.