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This paper introduced a very simple method to measure the liquid phase of spray in an optically accessible DI diesel engine. Particular attention was paid to easy usage and maintaining the compression ratio of the real engine. As a result, a less-expensive 4 W argon laser was used as the beam source and an E-10 high-speed camera was used for continuously observing the elastic-scatter liquid phase image. Meanwhile, the compression ratio can be kept as the real engines by this method. Through this method, the effects such as injection pressure, nozzle specification, intake air boost and temperature on liquid phase penetration before ignition were investigated. Reducing nozzle hole diameter decreased the length of the liquid phase. Increasing injection pressure hastened the evolution of liquid phase, while the liquid phase length varied complexly. Increasing intake air boost considerably shortened the liquid phase penetration and ignition delay.

Three dimensional computational model has been developed to predict the macroscopic behavior of the fuel spray in D. I. diesel engines. The model was based on the KIVA-II code with modification of some submodels that it can deal with the observed phenomena such as liquid column near the nozzle tip and spray impingement on a wall. Firstly, this model was verified by comparing the prediction with the experimental results in a constant volume vessel. Secondly with application to a D.I. diesel engine, the detailed behavior of the spray in a combustion chamber was revealed. Moreover, the engine performance under different spray angles were discussed with the prediction of this model.