Quantitative analysis of transient evaporation characteristics in diesel spray by high-speed UV-LAS technique

This paper reports the transient evaporation characteristics of diesel spray in an optical chamber at non-reacting high-temperature and high-pressure conditions. An ultraviolet/visible laser absorption and scattering (UV-LAS) technique was applied for visualizing and quantifying two-phase characteristics. The tip penetration, distribution of vapor mass concentration, equivalent ratio, and the mass of entrained gas was quantitatively obtained. The influence of micro-orifice diameter (0.11-0.18 mm), ambient temperature (700-900 K), and density (15-21 kg/m3) on spatial/temporal results were thoroughly compared. The results showed that the evaporation rate gradually exceeds the injection rate as the mixture temperature increases. The ambient temperature enhances the evaporation rate with a relatively constant entrainment speed and thus further narrows the gap between delivery and evaporation rate. The ambient density and nozzle diameter play a crucial role in the entrainment process by controlling the spray momentum, which dominates the spray volume and eventually influences the evaporation process. These results provide insightful information for understanding and modeling the evaporation process of a diesel spray.