Ignition-Characteristic Research of the Diesel Fuel in Combustion Vessel Simulated Diesel Engine Cold Start Condition

The initial ignition characteristic of fuel spray in a diesel engine is of great significance in the cold start problem. In this paper, the constant volume combustion vessel was applied to simulate the practical diesel engine condition near the end of the compression stroke and investigate the autoignition threshold temperature and other ignition characteristics for the fuel spray such as ignition delay time and initial ignition location. First, the influence of the ambient temperature and the ambient density in the vessel on ignition delay time, initial ignition location, and fuel mixture autoignition threshold temperature was researched. Then, the influence of fuel injection pressure and the plate surface temperature on ignition delay time and initial ignition location were also investigated in this paper. The results have shown that the autoignition threshold temperature was approximately 803K for the fuel spray in the combustion vessel, which simulated the practical diesel engine condition and the ignition delay time for both free jet and impinging jet increasing with the ambient temperature and the ambient density decreasing, respectively. The experimental map has also been developed to show the zone where initial ignition would occur with the different ambient temperatures and the ambient densities for the diesel fuel; the change of the injection pressure has no obvious influence on ignition delay time, but it reduces ignition success rate. The ignition delay time becomes longer as the plate surface temperature reduces and the variation rate of ignition delay time differs greatly in different temperature zones.