1984-02-01

Modeling of Transient Evaporating Spray Mixing Processes-Effect of Injection Characteristics 840226

Some results of a systematic numerical study of the effects of injection characteristics on the transient evaporating spray mixing process in a diesel like environment are presented. The study uses an existing two-dimensional stochastic thick spray model. It was found that, for a fixed injection quantity, changes in the nozzle hole number, nozzle hole size, and injection duration changed significantly the evaporation and mixing processes of a transient evaporating spray. In particular, It is found that, for a fixed nozzle geometry, reduced injection duration is most effective in increasing the mixing rate. The results also show that the injection rate shape greatly influences the mixing process of a transient spray, especially during the injection period. After the end of injection, the global effect of injection rate shape can be characterized by the mass averaged injection pressure alone. The higher the mass averaged injection pressure, the faster the mixing rate. In addition, the results of the end-of-injection study suggests that poor end-of-injection can result in poor spray atomization and local undermixing. Furthermore, the results of the pulsed (intermittent) injection study show that the mixing rate is reduced with pulsed injection if the injection rate remained fixed. Any gradual rise and fall in the injection rate shape during pulsed injection period reduces the effective injection pressure, hence mixing rate. Only pulsed injection with fixed injection duration gives faster mixing due to the increase in injection rate.

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