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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.

The purpose of this paper is to contribute to knowledge of the behavior of the stratified charge engine with prechamber injection by experimental investigation of several important parameters. Special attention is given to degree of charge stratification, position of injection nozzle and spark plug in the prechamber, construction of the injection nozzle, start of injection, timing of ignition, and throttling of the intake air. These parameters have a more or less significant influence on output, fuel consumption, and exhaust emission. Finally, the combustion system was adjusted partly by optimizing and partly by compromising. Comparison with a conventional spark ignition engine is made. Using a mathematical model of the process, the possible causes of the significant improvements in NO emissions are discussed.

A historical review of the patents and literature pertaining to 3-valve stratified charge engines is presented in this paper. This very old invention appears to be a practical approach for the “clean engine” being sought for vehicular use since it has the intrinsic capability of simultaneously giving good fuel economy and producing minimal objectionable exhaust emissions. The prime requisites of this engine are a rich prechamber charge and a very lean main chamber charge regardless of prechamber volume, nozzle diameter, valving and spark plug location. Fuel-air equivalence ratios of the charges in the two combustion chambers are significantly important in order to achieve the proper optimization. These ratios should be about 15% rich for the prechamber and 15 to 30% lean for the main chamber at the moment of ignition.

Combustion in model eddy combustion chamber was investigated in order to obtain insight into the combustion mechanism. High-speed schlieren cinematography and recording of the ionization current were used in the experiments. It was established theoretically and experimentally that the flame kernel formed by ignition at periphery moved towards the rotation axis and reached it in a time of the order of that for the mixture rotatory cycle at the periphery, irrespective of the circular speed of gas rotation and of the chamber size. After reaching the rotation axis, the kernel acquired the form of rotating body. The radial spread of this body can be lower than the visible rate of the immobile gas burning, due to the fast elongation of the rotating body along the axis. The results obtained are essential for understanding the phenomena occurring in eddy chamber of diesel engine and engines with spark ignition at an eddy motion.

Experimental work of the torch ignited engine demonstrated that this engine provided stable engine performance and low exhaust emissions using an overall lean mixture. Some combustion characteristics of the torch ignited engine were compared with those of a conventional one. Experimental analysis was performed to determine the influence of a number of prechamber inlet air-fuel ratios and nozzle diameters. These are respectively a main operating factor and a main design factor of the torch ignited engine. These factors control the torch combustion process and determine engine performance and emission characteristics.

This paper describes work done to separate and further define the effects of volume and temperature on the effectiveness of exhaust thermal reactors operating at lean (18-22:1) A/F ratios. Thirty feet of stainless tubing with a volume of over 1200in3 was added to the exhaust manifold of a 4 cylinder engine. The entire assembly was insulated to serve as a constant temperature “lean reactor”. Exhaust emission and temperature measurements at various points along the “reactor” provided data on the extent of the HC and CO oxidation reactions as a function of reactor volume. Mass flow calculations were made to calculate eahaust gas residence times. The data are presented as percent HC and CO rreacted versus gas residence time in the reactor and are plotted to show the effect of reactor temperatures ranging from 1275°F to 1675°F at various inlet HC concentrations. Limited data are also presented on the effect of exhaust flow rate on mixing.

The first engine dynamometer test results are presented for a modified fuel system based on hydrogen enrichment for a V-8 I.C. engine. The engine burns mixtures of gasoline and hydrogen under ultralean conditions to yield extreme low NOx emissions with increased engine efficiency. The hydrogen is produced in a compact onboard generator from gasoline and air. The hydrogen-rich product gas is cooled and mixed with the normal combustion air in a modified carburetor. The engine then operates in the conventional manner on atomized gasoline with spark ignition, but with hydrogen-enriched air and with a high spark advance of 40-50° BTDC. The engine thus receives two charges of fuel: a charge of gaseous fuel from the hydrogen generator, and the normal gasoline charge. The results on hydrogen enrichment are compared with the 1973 V-8 baseline stock engine with emission controls, and the same engine without controls and operated at a maximum efficiency under lean conditions.

The flow and combustion processes of a three-valve, stratified charge engine with small prechamber are examined for exhaust emissions. The exhaust emissions from a single-cylinder version of this engine are shown to depend on the internal flow processes as well as mixture supply stoichiometry. A theoretically-based simulation model of the engine flow and combustion processes is described. Model predictions are compared with time-resolved prechamber air-fuel ratio measurements made during intake and compression strokes. These comparisons are used to illustrate and describe the complex flow phenomena which take place in this engine. The combustion process is then examined with the aid of calculations using the simulation model. The complexity of the combustion process is illustrated by showing that, in addition to burned gas temperatures, the cylinder and prechamber burned gas air-fuel ratios change with time.

This paper presents a theoretical study of nitric oxide emissions from an unthrottled stratified charge, spark ignition engine. This investigation was undertaken to determine the nitric oxide production when an ideal rich-lean stratification is present and to determine the effects of introducing an intermediate stoichiometric region. In order to study this problem a three-region (generally rich, stoichiometric, and lean) combustion model was used, and the effects of the following variables were studied: 1. Excess air number of the rich mixture. 2. Percentage of the total fuel in the rich-mixture region. 3. Percentage of fuel burned stoichiometrically. 4. Exhaust gas recirculation, percentage and distribution. Comparisons are made to both experimental results from a throttled engine and calculated results for an unthrottled engine with a homogeneous mixture. For illustrative purposes, an application of the model to a particular geometrical form of charge distribution is analyzed.

Various homogeneous charge and stratified charge engine configurations were studied at wide-open throttle conditions, using simplified computer models. An order-of-magnitude parametric study was performed to find those combinations of variables which predicted a low nitric oxide level. Extreme values of variables were studied for a homogeneous charge engine configuration, which could be difficult to do in a real engine. As expected, these calculations indicated that for practical engine operation the equivalence ratio of the mixture must either be very rich or very lean for a resultant low nitric oxide level. Two extremes of stratified charge engine operation were investigated analytically, in other words, immediate mixing of newly formed products of rich combustion with excess air (instantaneous mixing) and a period of rich combustion followed by air addition to the rich products (delayed mixing). Comparisons of power, efficiency, and specific NOx are presented.

The Volkswagen prechamber injection stratified charge concept has a divided combustion chamber with part of the fuel injected into the prechamber and the intake manifold. Various combustion chamber configurations have been investigated in single-cylinder engine tests, and their applicability to the four-cylinder engine is discussed. The development of the third-generation 1.61 air-cooled opposed cylinder engine, along with its mechanical fuel injection system, is described. Engine maps of the prechamber injection engine are discussed, and engine performance data are specified. Test results on the dynamometer show very low nitrogen oxide emissions with fuel economy not impaired; however, hydrocarbon emissions without aftertreatment are still unsatisfactory.

Charge stratification has long been considered the best feasible means of burning overall weak mixtures. This offers the attractions of fuel economy and relatively low levels of pollutants emitted from the engine. In this paper, two idealised models of charge stratification are considered theoretically, with the emphasis on nitric oxide emissions. The first model represents a linear variation of fuel-air equivalence ratio, from a fuel rich mixture of the first element to burn, to a fuel weak mixture of the last element to burn. The effects of the slope of the equivalence ratio to mass fraction burned and the mean value of the equivalence ratio on nitric oxide emissions are analysed and discussed. The second model represents a step variation in the equivalence ratio, with two different zones each having a constant value of the equivalence ratio, and each being homogeneous within itself.

This paper describes the results of a three year field study into the crash performance of three basic designs of steering assembly, fitted to British cars. These systems have evolved to comply with current European and United States safety standards. While one design, involving a large-area, self-aligning steering wheel mounted on a conventional column, appeared from the field data to be highly effective in preventing serious chest and abdominal injury, the two systems utilizing axial-collapse steering columns proved to be essentially ineffective in practice. This finding is based on a field accident sample of 108 cases, so sampled as to be representative of the severe end of the collision speed and injury spectra. A test program was undertaken to examine the procedures currently used to evaluate steering assemblies. It was found that tests carried out in compliance with FMVSS 203 failed to differentiate between the safe and unsafe systems described above.

To clarify to what extent the results gained from known automobile-pedestrian impact experiments may be applied to actual accidents, comparisons with the analysis of actual accidents and comparable experiments were made with particular attention to the pattern of damage and the throw distances of the pedestrians. These results produced parameters that should be of additional use in forensic practice for defining the location of collision on the roadway. The injury patterns sustained by pedestrians involved in traffic accidents were related to vehicle damage and classified with respect to impact geometry. From the conclusions drawn from the pedestrians' motions, impact stress, and tolerance, experimental results may well be applied to the reconstruction of actual automobile-pedestrian collisions. However, this is true only within distinct classes of impact geometry, characterized by automobile front-end design, pedestrian size, and impact position.

This paper describes the results of a program to develop advanced cantilevered transit bus seats. The Department of Transportation's Urban Mass Transportation Administration funded the $26 million Transbus Program. The paper is divided into two parts. The first part describes the results of a detailed analysis of passenger accidents on-board current transit buses. The second part describes the results of sled tests that evaluated the safety of three new cantilevered seat/sidewall section designs proposed for Transbus relative to the safety of current transit buses. The testing facilities and procedures are described, along with a summary of the results of 16 sled test runs that employed four different sizes of anthropometric dummies. The results clearly indicate that the new seats have safety characteristics superior to current transit bus seats, especially in severe crash situations.

Noise tests were conducted on new and retreaded truck tires of a wide variety of patterns using three different procedures. Single tires on the test wheel and 2-tire sets on the road were correlated with the standard 4-tire sets in accordance with the Recommended Practice SAE J57 Procedure. The correlation was analyzed and the conversion techniques were discussed with the conclusions that it is possible to convert test wheel data to equivalent road test data. The results show that retreaded truck tires are not noisier than new tires of similar construction and tread design.

This paper explains how structural properties of radial and bias ply truck tires affect tire and vehicle performance. The author concludes that a knowledgeable evaluation of the pros and cons of both bias and radial ply truck tires be based on individual operational evaluations and the compromise of tire characteristics which best satisfy needs. Neither radial nor bias ply truck tires can be generalized as the superior choice since each type has areas of superiority.

A simple method based on bevameter soil values enables the engineer to evaluate the motion resistance of a pneumatic tire, in the given soil, and to perform parametric analyses of design and performance. The parameters measured include, besides soil parameters, the following characteristics of the tire: width, diameter, inflation pressure, carcass stiffness, and load. An inexpensive electronic desk calculator assures accuracy of prediction that is more than satisfactory.

This paper discusses equipment and procedures required to retread radial tires, emphasizing truck tires; reviews retreading process for conventional tires; and notes changes required for radials. In exploring the most extensive problem, inability to properly contract and expand radials to provide curing pressure, the paper indicates the need for an elastic matrix and supports use of precured tread systems.