A Numerical Study of the Transient Evaporating Spray Mixing Process in the Diesel Environment

Some results of a systematic study of the effects of fuel and chamber gas properties on the transient evaporating spray mixing process are presented. The study uses an existing two-dimensional stochastic thick spray model. The results show that the combustion process in typical heavy duty, quiescent, DI diesel engines can be mixing limited rather than vaporization limited. In addition, the results show that the mixing process of a transient evaporating spray is characterized by the combined effects of fuel evaporation and its turbulent mixing with the surrounding air. In general, increasing the evaporation rate alone does not necessarily increase the fuel-air mixing rate. Furthermore, two dimensionless parameters have been used to quantify the relative effects of fuel and chamber gas properties on the transient spray evaporation process. Finally, through detailed comparisons between spray and gas jet results, the transient evaporating spray mixing process is better understood. With this understanding, further modification of the phenomenological jet mixing model published earlier can and will be made.