Experimental investigation on evaporation, puffing and vapor jetting of multi-component fuel droplets with high-volatility difference

Abstract

The current study presents an experimental investigation into the evaporation, puffing and vapor jetting characteristics of multi-component fuel droplet with high-volatility difference at 773 K. The multi-component fuel blends consist of biodiesel as a lower-volatile component, while 2, 5-dimethylfuran (DMF) is used as the higher volatile constituents. The DMF content is systematically varied from 0 to 100 %vol, employing both the fiber-support method and a magnified high-speed backlight illumination technique. The results show that the biodiesel-DMF blended droplets only exhibited weak rupture phenomena: puffing and vapor jetting. In puffing, the thinning of the liquid film primarily arises from the squeezing effect of bubbles, while in vapor jetting, the reduction of the liquid film is predominantly a consequence of the evaporation of the liquid film. Anomalous behavior occurred during the evaporation process of biodiesel-DMF droplets. The lower-volatile component within the droplets did not contribute to an accelerated evaporation of the blended droplets; instead, they resulted in the suppression of their evaporation. In comparison to the theoretical value, the evaporation duration of blended fuel droplets increased by 56.6 %, 50.6 %, and 78.9 %, respectively. This outcome is attributed to the combined effects of five factors: an increase in the overall thermal resistance, a reduction in heat and mass transfer within the gas phase, the occurrence of condensation and incomplete micro-explosion. Notably, the primary factor plays a significant role as the main contributor to this phenomenon, with its contribution to the reduction in droplet evaporation rate ranges from 28 % to 59 %.