STUDY OF THE CONDITIONS FOR CONTROLLED IGNITION OF FUELS WITH A POOR AUTO-IGNITION QUALITY

摘要

This study deals with the development of the controlled-ignition technology for high-performance compression ignition alcohol engines. The objective of this study is to clarify the physical aspects of the main factors governing the auto-ignition phenomenon of an alcohol spray. We are now in the process of drawing a map that will indicate the influence of the auto-ignition quality evaluated by the ignition delay at each governing parameter. When the mapping is completed by a number of systematic experiments, the engine control logic can be established and high-performance alcohol engines can be realized. In order to realize such engines adaptable for any kind of biofu-els including alcohols with a poor auto-ignition quality, the establishment of the ignition-control technology is most important. In the mixture formation process, two kinds of factors that govern the auto-ignition phenomenon of an alcohol spray have to be considered. One can be called the internal factor relating to the fuel properties. The other can be called the external factor corresponding to the surrounding gas conditions such as pressure, temperature, and oxygen concentration. This paper mainly focuses on the effect of the external factors on auto-ignition. In the experiments, ethanol-diethyl ether (ED) blended fuels were employed in order to investigate the effects of internal factors. Spray mixture formation and auto-ignition phenomenon of tested fuels in a large constant-volume-electrical-heating chamber was visualized by the shadowgraph method and images were recorded with a high-speed camera. The results obtained showed that the oxygen concentration and temperature of the surrounding gas strongly influence the ignition delay.