Ignition Mechanism Analysis of DI Diesel Fuel Spray Using Constant Volume Combustion Vessel and Bottom-Viewed Single Cylinder Diesel Engine

The ignition phenomena of diesel fuel spray injected into a constant volume vessel with medium injection pressure were investigated. Results show that ignition occurs at a certain point near the surface of spray liquid column before breakup where activation reaction is advanced one step ahead of others and the impingement plate assists surface ignition. From these results was deduced the following concept that fuel vaporized from the liquid surface begins to be activated when the velocity gradient at the liquid column surface decreases to a certain level, leading to ignition. The blowing-off limited ignition model was proposed from this concept. Based on the functional relation between various factors and the ignition delay derived from this model, the ignition delay date were well arranged into an experimental formula. Next, ignition investigation was carried out using a bottom-viewed single cylinder engine, revealing that the effects of many factors including EGR rate related to O2 concentration can be analyzed comprehensively based on the above model.