Abstract
KEYWORDS – Spray Structure, Evaporation, Flash Boiling Spray, Liquid Spray, Ambient Temperature
ABSTRACT
Direct Injection (DI) technology has been widely adopted in gasoline engines because of its high fuel economy and excellent transient response. Fuel spray characteristics in DI engines are crucial to the performance of combustion and emission. The objective of this study is to systematically investigate the influence of ambient temperature on spray structure and evaporation characteristics under non-flash boiling, transitional and flare flash boiling conditions. Mie-scattering method was employed to capture the time-resolved structure of liquid sprays under various ambient temperatures. In addition, Schlieren method was used to measure the time-resolved liquid-vapor distribution of the spray. A high pressure and high temperature constant volume chamber was utilized to realize various ambient temperatures and superheat degrees for sprays. A single-hole injector was tested and n-hexane was used as the fuel. The experimental results show that higher ambient temperature leads to stronger fuel evaporation and shorter liquid penetration for all spray conditions. Specially for the transitional flash boiling spray, the influence of ambient temperature on the macroscopic structure is the most noticeable among all three conditions. For non-flash boiling spray, the time required for full vaporization is reduced considerably under high ambient temperature. In contrast, flare flash boiling spray is less sensitive to different ambient temperatures than transitional and non-flash boiling spray.