Numerical approach to analyze propane flash boiling spray using modified gas-jet model

Abstract

In engine simulation, coarse mesh size is usually used to analyze a variety of cases utilizing chemistry which consists of many species and reactions. However, it is difficult to predict spray morphology exactly with coarse mesh. In this study, a model to predict structure deforming flash boiling spray even for the coarse mesh has been developed. A flash breakup model combined with a modified version of a gas-jet model was utilized to analyze propane flash boiling spray. The gas jet direction was calculated by averaging the directions of spray from each nozzle. A high-velocity region near the axis of gas-jet flow confined the plumes to form a single plume. Gasoline spray was analyzed to determine proper Kelvin-Helmholtz-Rayleigh-Taylor (KH-RT) model constants. Gasoline spray characteristics such as spray tip penetration and morphology were captured using the final model constants. Using the KH-RT model constants, the flash breakup model was validated for propane flash boiling spray. Sauter mean diameter (SMD) of simulation and experiment showed similar results. However, spray morphology could not be captured by the simulation using only the flash breakup model. A modified gas jet model was applied to the simulation along with the flash breakup model to improve spray morphology. Using the modified gas-jet and flash breakup models, spray structure penetrating through the central axis was successfully predicted and this resulted in a better spray tip penetration prediction. SMD trend depending on ambient pressure was captured and maximum error between experimental and simulation results was 11%.