Impact dynamics of alternative jet fuel drops on heated stainless steel surface

Abstract

There is an emerging trend of employing bio-derived alternative fuels in automobile and aircraft engines to meet the strict norms of environmental pollution. The present study deals with the impact dynamics of camelina-derived alternative jet fuel drops corresponding to Weber number, We in the range 28–886 on heated flat stainless steel surface at surface temperature, Ts ranging from 25 °C to 350 °C. The entire impact dynamics is captured using a high speed camera and analyzed to deduce the temporal variation of normalised drop contact diameter, β for the drop impact cases at different Ts. The high speed image sequences help to record the morphological behaviour of impacting alternative jet fuel drops on the heated surface at different combination of We and Ts and to arrive at phase diagram highlighting the broad regimes of biofuel drop impact dynamics. For the impact of high We drops, the average normalised spreading velocity increases in film boiling regime whereas it slightly decreases in the cases of un-heated surface, film evaporation, and nucleate boiling. The trend of maximum spread factor, βmax with We at different heat transfer regimes is presented. The sensitivity of βmax to We depends on the heat transfer regime and is the highest in the film boiling regime. Further the receding dynamics of impacting biofuel drop on the heated surface is significantly influenced by Ts. The observed trends are qualitatively explained through a temperature-dependent apparent contact angle in the available theoretical models as well as the presence of vapor flow and associated fingering at the rim of drop lamella.