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SAE 952431

A New High Pressure Droplet Vaporization Model for Diesel Engine Modeling

By: Eric W. Curtis, Ali Uludogan, Rolf D. Reitz


A droplet vaporization model has been developed for use in high pressure spray modeling. The model is a modification of the common Spalding vaporization model that accounts for the effects of high pressure on phase equilibrium, transport properties, and surface tension. The new model allows for a nonuniform temperature within the liquid by using a simple 2-zone model for the droplet. The effects of the different modifications are tested both for the case of a single vaporizing droplet in a quiescent environment as well as fora high pressure spray using the KIVA II code. Comparisons with vaporizing spray experiments show somewhat improved spray penetration predictions. Also, the effect of the vaporization model on diesel combustion predictions was studied by applying the models to simulate the combustion process in a heavy duty diesel engine. In this case the standard and High Pressure vaporization models were found to give similar heat release and emissions results. However, the results show that a more realistic representation of the vaporization process is achieved with the new model. In particular, less unburned fuel is predicted to remain in the combustion chamber late in the power stroke.