1973-02-01

Analysis and Control of Transient Flow in the Diesel Injection System Part I - The Analytical Control Method 730661

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. On the other hand, the average instantaneous elastic energy stored in the system was found to be a well-behaved function of time and was therefore selected as the control parameter.A design procedure to control after-injection was formulated. In this procedure, design changes required to achieve improved system characteristics were obtained by specification of the average elastic energy function. Two design changes were considered. These included the design of an additional control valve in the pump delivery chamber and the redesign of the pump spill port. The design techniques used in the control method are described in this paper, while the application, results, and experimental verifications are given in a companion paper.

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