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A modified version of the pneumatic air cushion bumper has been incorporated into the basic design of a prototype automobile designed to provide improved structural performance during front, side, rear, and rollover collisions. A simple air bladder, recessed within a high-strength bumper bar, was supported by the front cross member of a modified frame which also served as a supplementary volume to reduce peak pressures and loads. Check valves were located between the bladder and the frame chamber to limit energy of rebound. Test results showed that the design is suitable for incorporation into vehicles intended to withstand barrier crashes of 5-10 mph.

During the past two decades, front-wheel-drive architecture has grown enormously in Europe. This trend can be explained by the need to provide compactness, large inside space, and good road holding. The paper describes technical problems that arise when designing a front-wheel-drive car and quotes the various technical solutions in current use. The authors conclude that a preference for front-wheel drive will last for a long time.

The performance of a hydrogen-supplemented fuels system is predicted using a semiempirical model. The prediction of this model is compared to data obtained during engine dynamometer tests of a hydrogen generator/multicylinder engine system. The test data and the predictions are also compared to the fuel consumption and emissions of the same engine in its stock configuration and indicate that the hydrogen-supplemented fuels system can improve BSFC 10-15% and simultaneously reduce NOx emissions to a level consistent with the 1977 EPA standard. The performance of an optimized hydrogen generator/engine system is estimated. With these comparisons and estimates used as a basis, the potential of the hydrogen-supplemented fuels system is identified.

Research is demonstrating that it is possible to significantly reduce the in-cab noise levels of the Army's current truck fleet, with accompanying exterior noise reduction. Results are applicable to future Army trucks as well and are reported on a program utilizing a 5-Ton Army Truck. This type of truck was found generally to exceed the applicable limits established in the new MIL-STD 1474, “Noise Limits for Army Material.” The program identified major noise sources and important paths for sound to enter the cab and resulted in the selection of optimum sound absorption, sound barrier and vibration damping materials. The effect of a prototype exhaust system and its placement relative to the cab and the importance and optional means of controlling cooling fan and engine noise were also investigated.

A mathematical model describing the Wankel engine combustion process is developed to evaluate the effects of apexseal leakage on NO emissions. It is assumed that leakage occurs only during combustion and expansion and that only unburned gas leaks out during combustion and that only unburned gas leaks out during combustion and that during expansion, only burned gas leaks out. A parametric study is performed to show the effects of such variables as equivalence ratio, compression ratio and engine speed. An experimentally obtained pressure time trace is used to show the accuracy of the model predictions. It was found that under normal operating conditions (near F = 1), reductions in apex-seal leakage area will not cause an increase in NO emissions and that below 2500 rpm, mass leakage drastically increases with further reductions in speed.

Measurements were made of exhaust histories of the following species: unburned hydrocarbons (HC), carbon monoxide, carbon dioxide, oxygen, and nitric oxide (NO). The measurements show that the exhaust flow can be divided into two distinct phases: a leading gas low in HC and high in NO followed by a trailing gas high in HC and low in NO. Calculations of time resolved equivalence ratio throughout the exhaust process show no evidence of a stratified combustion. The exhaust mass flow rate is time resolved by forcing the flow to be locally quasi-steady at an orifice placed in the exhaust pipe. The results with the quasi-steady assumption are shown to be consistent with the measurements. Predictions are made of time resolved mass flow rate which compare favorably to the experimental data base. The composition and flow histories provide sufficient information to calculate the time resolved flow rates of the individual species measured.

This paper reports on some recent work performed to establish the effectiveness of exhaust gas recycle as a knock suppressant in spark ignition engines, and to determine the effect of fuel and engine operating conditions on knock-limited engine performance and NOx emissions. Performance was evaluated with two different fuels: ASTM isooctane and ASTM 80 octane. With ASTM 80 octane fuel, operating near stoichiometric, the higher knock-limited compression ratio (klcr) resulted in a break mean effective pressure (bmep) which was constant for moderate recycle, falling only with high recycle rates. Brake specific fuel consumption (bsfc) decreased with recycle to a minimum, and then increased for higher recycle rates. For lean mixtures, however, bsfc increased steadily with recycle. Performance was similar with the isooctane. The performance recovery for stoichiometric and rich mixtures (low to moderate recycle) was attributed to the higher klcr and changes in the specific heat ratio.

This paper provides a user oriented description of techniques for the measurement and analysis of engine cylinder pressures. These techniques were developed for piezoelectric transducers and for digital systems of data acquisition and analysis. Test cell procedures are described for transducer preparation and calibration, and for association of each pressure with its appropriate crank angle. Techniques are also described for evaluating the accuracy of pressure data and for eliminating specific errors. Two examples of uses for pressure data are discussed: the calculation of heat release rate in conventional engines, and the computation of internal flows in divided chamber engines.

Attention in the United States is centering on investigations of lighter materials, more efficient structures, impact compatibility between cars, as well as between structure and restraints and simulation of collisions using both mechanical and computer techniques. This paper summarizes investigations as well as safety effects.

Obtaining vehicle fuel economy data in conjunction with chassis dynamometer emissions testing is a useful, convenient technique. Data derived in this manner, using EPA city and highway driving cycles, are in wide use. Fuel economy results obtained by carbon mass balance calculation of carbon containing compounds in the vehicle exhaust are at least as accurate and repeatable as those obtained by direct measurement of fuel consumed. Nevertheless, the overall chassis dynamometer-carbon balance fuel economy test yields undesirable variation of results and needs refinement. Major factors influencing the accuracy and repeatability of test results are: CO2 measurement accuracy; variations in following the driving cycle; vehicle-dynamometer interface conditions; and associated calibration, calculation, test technique and procedural methods and controls employed.

As part of its ESV evaluation effort, Dynamic Science has recently conducted vehicle-to-vehicle aggressive testing of the large AMF ESV with two small Fiat ESVs (Fiat 2,000-pound and Fiat 2,500-pound classes) at a closure speed of 75 mph. Preliminary analyses of crash test results are presented in this report. The vehicle-to-vehicle tests were highly successful in that structural integrity of the Fiat passenger compartments was adequately maintained. The AMF vehicle's hydraulic subsystem absorbed a significant portion of the crash energy in its 20-inch stroke, thus offering reduced aggressiveness to the small Fiat vehicles. However, human survival in terms of meeting current occupant injury criteria was not evaluated since dummies were not included in this preliminary test series. Such an evaluation is planned as part of future phases of this ESV evaluation program.

To ensure cost-effectiveness, automotive industry solid-state device requirements, a small percentage of total U.S. consumption, will be met through custom designs using technologies applicable to non-automotive applications as well. N-MOS and complementary-MOS technologies with their cost and performance advantages and smaller size will prevail in digital signal processing; bipolar IC's plus IC's combining bipolar and MOS technologies on the same chip will be used for linear signal processing. Multiple-epitaxial structured silicon power devices will be used as actuator drivers. The reliability/cost equation will be solved by using buffered power sources to permit use of custom-designed low-voltage IC signal-processing circuits. Power devices having device characteristics that can withstand the high voltage transients will provide the interface between the low-level signal processing and actuator drivers.

This paper describes the application of composite laminates consisting of bonded rubber and plastic layers to discrete energy absorber units and flexible bumper systems. These laminates are manufactured by the fusion bonding technique applied to injection moulding of discrete EA units and thermoforming of resilient EA bumpers. The two material construction allows greater design flexibility in unit and system design. The properties of the dual material system permit a high ratio of energy absorption per unit weight coupled with full recovery of pre-impact configuration. The performance and installation requirements of the ‘V’ shaped discrete bumper mountings is described in detail. Experimental developments in fully flexible bumpers are then discussed.

Through our development work on a bumper system that would meet the requirements of FMVSS No. 215, “Exterior Protection of Passenger Cars,” the correlation between the physical properties of the compressible solid, and the mechanical structure and load-deflection characteristics of the shock isolator system has been clarified. A number of silicone rubbers were investigated and their molecular weight and cross-linking density changed. The results of these investigations have been applied to the new shock isolator system of our 1974 model vehicles.

A major difficulty in performing cost-benefit analyses of bumper designs is the fact that much of the damage from low-speed crashes is never reported either to public agencies or insurers. Much of this unreported crash damage remains unrepaired, at least for some time after the crash, and thus surveys of unrepaired crash damage can provide one source of data for some of the unreported crash damage. During the summer of 1974, surveys of unrepaired crash damage were conducted in seven metropolitan areas. The results of these surveys are presented. It is concluded that the present state of knowledge on the frequency and amount of unreported crash damage is too limited to enable this essential component to be adequately incorporated into cost-benefit analysis of bumper designs.

Data from the Nationwide Personal Transportation Study (NPTS) and other sources have been used to generate distributions of vehicle miles traveled (VMT), average speed, and fuel consumption as a function of trip length. Approximately one third of all automobile travel in the U.S. is seen to consist of trips no more than ten miles in length. Because short trips involve more frequent stops and a smaller percentage of operation during warmed-up conditions, nearly half of the fuel used by automobiles is consumed during the execution of these short trips. The typical trip of approximately ten miles in length has been shown to result in a fuel economy that is equal to the average fuel economy achieved for all trips combined.

Information about public driving patterns was collected in three ways. 1. Chase Cars, equipped with instrumentation were used to monitor 2,500 randomly selected trips in various parts of the United States. Data relating to 11,000 miles of operation was thereby recorded and analyzed. 2. Long duration strip-chart recorders were installed in vehicles in use by the public. These devices recorded traces of speed vs. time, while the vehicles were in motion. More than 12,000 miles of driving were recorded. 3. Passive electronic recording devices were installed in selected vehicles which were in use by the public. These devices recorded the portion of miles driven within various speed bands. In this manner, more than 61,000 miles have been recorded. This study is still in progress and is intended to monitor long-term trends in customer operation.

A new fuel economy test procedure has been developed for passenger cars and light trucks that is basically similar to the established procedures used by U.S. automobile manufacturers. The new SAE procedure provides a standardized method for use in obtaining and comparing vehicle fuel economy values that relate to average conditions encountered in various modes of driving. The various aspects of the program discussed in the paper include road versus laboratory testing; existing procedures; evaluation, comparison and selection of test cycles; test repeatability amongst facilities; relation of test results to those obtained in actual customer usage; comparison of independent consumer survey results; and correction factor development and application.