Ethanol droplet evaporation: Effects of ambient temperature, pressure and fuel vapor concentration

Ethanol is considered a promising alternative fuel due to its advantages compared to conventional fossil fuels. Since fuel evaporation plays an important role in many applications, especially in energy systems involving spray combustion, this work aims to investigate the effects of ambient temperature, pressure and vapor concentration on the evaporation of a single ethanol droplet. In order to validate the theoretical model, numerical simulations of an ethanol droplet evaporation are performed and the results are validated with experimental data. The ambient temperature, pressure and vapor concentration were varied in the ranges of 400-1000 K, 0.1-2.0 MPa and 0.0-0.75, respectively. The results reveal that an increase in the ambient pressure causes an augmentation in the ratio of initial heat-up time to the whole evaporation lifetime, which enhances the unsteady effects of the droplet evaporation. This same ratio is almost independent of the gas temperature at low ambient pressure; however, as the ambient pressure is increased, the tendency of this ratio to increase with the gas temperature becomes significant. Additionally, the results show that there is a threshold ambient temperature, which determines whether the average area reduction rate will increase or decrease as the ambient pressure is increased. Finally, the results show that condensation effects are observed for non-zero ambient vapor concentration, and there is also a threshold ambient temperature which determines whether the average area reduction rate will increase or decrease as the ambient vapor concentration is increased. (C) 2019 Elsevier Ltd. All rights reserved.