Ethanol/Gasoline Droplet Heating and Evaporation: Effects of Fuel Blends and Ambient Conditions

This paper focuses on the modeling of blended ethanol/gasoline fuel droplet heating and evaporation in conditions representative of internal combustion engines. The effects of ambient conditions (ambient pressure, ambient temperature, and radiative temperature) and ethanol/gasoline fuel blend ratios on multicomponent fuel droplet heating and evaporation are investigated using the analytical solutions to the heat-transfer and species diffusion equations. The ambient pressures, gas and radiative temperatures, and ethanol/gasoline fuel ratios are considered in the ranges of 3-30 bar, 400-650 K, 1000-2000 K, and 0% (pure gasoline)-100% (pure ethanol), respectively. Transient diffusion of 21 hydrocarbons, temperature gradient, and recirculation inside droplets are accounted for using the discrete component model. The droplet lifetimes of all mixtures decrease when ambient temperatures increase, under all ambient pressures (3-30 bar). The combination of ethanol and gasoline fuels has a noticeable impact on droplet heating and evaporation; for pure ethanol, the predicted droplet surface temperature is 24.3% lower, and lifetime 33.9% higher, than that for gasoline fuel under the same conditions. Finally, taking into account radiation decreases the gasoline fuel droplet evaporation times by up to 28.6%, and those of ethanol fuel droplets by up to 21.8%, compared to the cases where radiation is ignored.