Droplet Breakup Model in Spray Combustion SimulationBased on Measurements of Droplet Disintegration Mechanisms

Abstract

ABSTRACT: A breakup model used in spray combustion simulations was developed to predict the breakup process of spray droplets, which has large influences on the mixture formation and the combustion process in internal combustion engines. Taylor Analogy Breakup (TAB) Model is widely used as a droplet breakup model. Improved TAB (ITAB) Model has been developed by improving model constants and the breakup/non-breakup boundary condition of TAB Model. ITAB Model reproduces the dimensionless breakup time based on the observation results of the single droplet breakup behavior and CFD simulation results. In this study, calculation methods of droplet diameter and droplet velocity after breakup in ITAB Model are modified to avoid fitting model constants during spray analysis. Droplet diameter after breakup is determined by calculating Sauter Mean Diameter and using the droplet diameter distribution after breakup based on the observation results of the single droplet breakup behavior. The calculation constant for Sauter Mean Diameter is a function of Weber number to reproduce the breakup phenomenon of single droplets. Droplet velocity after breakup is calculated based on the energy conservation law of droplets used in Enhanced TAB Model. This model shows that Sauter Mean Diameter after breakup is almost same and perpendicular motion of droplets after breakup is more active than TAB Model. This model also considers the effects of the fuel physical properties on breakup characteristics. Model analysis shows that droplet diameter after breakup of the high boiling point component fuel is larger under same conditions and the effect of temperature change is larger than that of the low boiling point component fuel.