Search

Measurements of ignition delay and other combustion phenomena were made on a single-cylinder, open-chamber, supercharged research diesel engine. The influence of engine speed, fuel/air ratio, and air-charge pressure are reported. The results show that the elapsed time from the start of injection until illumination occurs is longer than that for pressure rise due to combustion. As expected, the measured ignition delay is decreased with increased speed. However, when a correction was made for cylinder air temperature change due to speed, the ignition delay increased with speed. Increase in the fuel/air ratio decreased the measured ignition delay. However, when corrected, the ignition delay was unaffected by fuel/air ratio. The smoke increased with engine speed and fuel/air ratio.

A theoretical digital simulation of a conventional diesel fuel injection system was developed to study the problem of after-injection in diesel engines which results in increased exhaust emissions. The influence of wave propagation phenomena, pipe friction, and cavitation were included in the study. Computer results were compared with transient pressures measured on an actual fuel injection system operated on a test bench, and the comparisons showed the accuracy and validity of the simulation method. Analytical control methods were developed to help determine design means to control after-injection. One design change consisted of the addition of a control valve in the pump delivery chamber, while another involved the modification of the pump spill port. Pressures and flows were not significantly altered during the main injection period with either design change. The simulation program confirmed the ability of both design changes to control after-injection, and experimental data from a system with the pump spill port modified in accordance with theoretical design calculations provided satisfactory confirmation of the analyses.