Study of component proportion effects on flash boiling atomization with ternary-alkane fuel mixtures

Abstract

When liquid fuel is injected under superheated conditions, it would experience rapid evaporation in the form of flash boiling. Bubbles constantly generated inside liquid can enhance the atomization and evaporation of fuel spray, and further changes spray macroscopic structure. Former studies have shown that the presence of high volatility fuel can significantly prompt the atomization of low volatility fuel. However, the effects of component proportion on the flash boiling atomization of multi-component fuel spray have not been fully understood yet. Moreover, the lack of an appropriate superheated index for multi-component fuel spray hinders the deeper physical insight into their flash boiling behavior. To bridge these gaps, three single-component alkanes (n-pentane, iso-octane, and n-decane) with noticeably various vapor pressures were blended in different mixtures to investigate the influence of component proportion on their flash boiling behavior. Their macroscopic spray cross-patterns were tested under various fuel temperature and ambient pressure using a high-speed planar laser Mie-scattering imaging system. The difference of their spray cross-patterns was analyzed. The results indicated that the component proportion of light-end component (with the highest vapor pressure) dominates the spray flash boiling behavior due to its high likelihood of evaporation. Based on these results, a new superheated index modified from the ratio of ambient pressure and bubble point pressure was proposed to predict their flash boiling behavior. This newly proposed superheated index was found to better elucidate the flash boiling behavior of test fuels.