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This paper presents an experimental study of the performance of several fuel injection nozzles actuated by pressure pulses derived from an accumulator maintained at steady high pressure. Good performance and several types of poor performance of these nozzles are characterized and mapped in terms of variables that can be readily measured, and that could be automatically controlled. The results reveal a new approach for controlling high pressure fuel injection that could provide good system performance over an extremely broad range of fuel injection rates. Although the results of this work are general in scope, they might be applied most advantageously to open-chamber, stratified-charge, spark-ignited engines. The potential application of this approach to such an engine is discussed.

Secondary injection in a diesel engine is defined as the introduction of additional fuel into the combustion chamber after the end of the main injection. It is usually caused by residual pressure waves in the high-pressure pipe line connecting the pump and injector. When these waves exceed the injector opening pressure, secondary injection occurs. Tests revealed that the U.S. Army TACOM single-cylinder engine used in this investigation, fitted with an American Bosch injection system, had secondary injection within the normal engine operating region. The pump spill ports and delivery valve were redesigned to eliminate secondary injection, in accordance with previously reported work. Comparative tests of both the conventional and modified injection systems were run on the same engine, and the effects of secondary injection on engine power, economy, and exhaust emissions were determined.

After-injection is the introduction of additional fuel to the combustion chamber after the end of the main injection. It is a persistent diesel fuel injection problem which usually results in reduced engine power and economy and increased emissions. After-injection is caused by uncontrolled pressure transients at the injector after the opening of the pump spill port. These pressure transients are related to the wave propagation phenomena in the high-pressure pipeline connecting the pump and injector. Use of experimental trial-and-error methods in attempts to control this phenomenon has met with limited success. The analytical control method described in another paper is used to determine design means by which after-injection may be controlled. Further investigation and evaluation of two design changes which release the injection system excess elastic energy in a controlled manner are considered herein. One design change is the addition of a control valve in the pump delivery chamber.

The increasing requirements imposed on diesel engine manufacturers have required the study of fuel injection system faults and the development of means to eliminate them. Until now, improved injection system characteristics have been obtained by experimental trial-and-error procedures. These procedures, however, have proved to be inconvenient, tedious, and have had limited success in eliminating system faults such as after-injection. This is mainly because the transient nature of the injection process requires a more thorough study of the system time-varying parameters. In this paper the residual transients which cause after-injection are analytically investigated. The control of these transients required specification of some system parameter. The rapidly varying nature of the system pressures and flows prevented the use of these variables as control parameters.

The theoretical relationship between engine air consumption and exhaust back pressure is derived for an idealized, 4-stroke-cycle engine inlet process, and compared to results obtained by testing a typical automobile engine. The exhaust back pressure of a 1971 Ford 351-W, V8 engine was varied 0.5-1.5 atm, under a wide range of engine speeds and loads. The results show that engine air consumption responds to variation of the ratio of absolute exhaust back pressure to absolute inlet manifold pressure in a manner approximating that indicated by theory, with a strong dependence on engine speed. These data can be useful in the design of speed-density fuel injection systems for automobiles. Data are also presented concerning the effect of exhaust back pressure on performance and exhaust emissions. Increase in exhaust back pressure decreases nitric oxide, due to the increased exhaust gas remaining in the cylinder, as has also been demonstrated by others.

A theoretical digital simulation of a conventional diesel fuel injection system has been developed. The influence of such factors as wave propagation phenomena, pipe friction, and cavitation are included. The computer results are compared with transient pressures as measured on an actual fuel injection system operated on a test bench. The comparisons show the accuracy and validity of this simulation scheme. Special attention is given to some of the important factors that affect the accuracy of the simulation model. These include the effect of pressure on the fuel bulk modulus and wave speed, the pipe line residual pressure, and the coefficient of discharge of important orifices.

A correlation between the ignition delay, based on the start of pressure rise due to combustion, and the mean air charge temperature has been obtained for diesel, “CITE,” and gasoline fuels. The experimental work was done on a single cylinder open combustion chamber research engine. The intake air temperature was varied over a wide range from atmospheric to about 750 F. The experimental data indicated that the best correlation of the ignition delay and the reciprocal of the absolute temperature is of an exponential form. The apparent activation energy for the three fuels was found to have a straight line relationship with the cetane number of the fuel.

The automotive gasoline engine has been under heavy attack as a source of air pollution, and is now the subject of a very large program of research and development to reduce its undesirable vehicle emissions. The quantity of emissions that can reasonably be tolerated in different areas of the U.S. is presently unknown because of lack of information concerning air movements and air quality standards for man and plants. It is important that this information be made available as quickly as possible because the cost of emission controls of all types will rise rapidly. With rapidly rising costs for air pollution control from all sources, cost-value analyses are urgently needed for economy. Major reductions of the undesirable exhaust emissions of present powerplant systems have been made during the last few years and will continue to be accomplished, under the impetus of air pollution requirements and regulations.

The object of this research was to learn more about the effects of mixture motion upon ignition in spark ignited piston engines, and to determine how variations in mixture velocity alter the combustion process. To provide effective means for producing and measuring the mixture velocity, all tests were made in a constant volume bomb, using mixtures of propane and air. The effects of mixture motion on the lean spark ignition limit, rate of pressure rise, and burning time were determined for mixture ratios ranging from stoichiometric to the lean limit. The mixture pressures corresponded to those in Otto cycle engines at the time of spark occurrence. The results reveal that a mixture velocity of 50 fps, relative to the spark plug, requires an enrichment of 17% with respect to the stagnant lean limit. Increases in mixture velocity were found to greatly increase the rate of pressure rise during combustion. This effect was more pronounced for lean mixtures than for stoichiometric mixtures.

The ignition delay in diesel combustion has been studied in a turbulent chamber engine. The criteria used to define the end of this period are the pressure rise and illumination due to combustion. The pressure rise delay is generally shorter and more reproducible than the illumination delay. The effect of the following factors on the ignition delay were studied: cylinder pressure, fuel/air ratio, fuel injection pressure, cooling water temperature, and engine speed. Data concerning the effect of cylinder pressure on the pressure rise delay period, at constant air temperature, were correlated and compared with previous experimental results. The analysis indicated that the pressure rise delay is affected by physical and chemical factors as well as thermodynamic parameters that control the several forms of energy during the delay period.

This paper provides data concerning the enrichment of automotive carburetors with variation of inlet air pressure and temperature. These changes occur with weather and the seasons, with altitude, and because of underhood heating. The early opening of the conventional carburetor enrichment value at altitude can add greatly to the “ normal” carburetor enrichment. Means for compensating the mixture ratio for these changes in inlet air conditions are known, but will almost certainly add to the complexity and cost of the engine induction system. The cost of improved devices must be compromised with the possible reduction in exhaust emissions and improvement in fuel economy.

Alcohol has been promoted and used as a motor fuel for more than 50 years. However, United States ethyl alcohol production is small compared with gasoline production. High latent heat of vaporization of alcohol makes possible some increase of power over gasoline. The heating value of alcohol is low and energy content of alcohol blends is less than that of gasoline; fuel consumption of blends is therefore increased. The ability of ethanol to improve the octane number of gasoline has diminished as the octane number of gasoline has improved. There is no published evidence that alcohols can appreciably reduce air pollution problems.

THE speed-density carburetion system meters fuel in accordance with engine rpm, intake-manifold temperature, intake-manifold pressure, and exhaust back pressure. The advantage of the system is that these variables can be read and the carburetor settings directly derived or checked during flight. A separate fuel-feed control is provided to govern intake-manifold pressure and temperature - the two main factors affecting detonation.