The influence of non-ideal vapor–liquid equilibrium on the evaporation of ethanol/iso-octane droplets

The present work investigates the differences between ideal and non-ideal vapor–liquid equilibria (VLE) and their effect on vaporization for multicomponent hydrocarbon fuels, which are representative for combustion and gasification. For this purpose, a parametric study is performed for examining non-ideal VLE behavior within a pressure range from 0.5 to 20.0 bar and an ambient temperature range from 0 °C to 600 °C, which are typical vaporization conditions in technical systems. The VLE results are then applied in a 0D single-droplet evaporation model, which can be considered a base model for most CFD applications. The droplet life time and the evaporation rates of the individual liquid components are studied for ideal and non-ideal VLE by varying the pressure, the temperature and the particle Reynolds number. A detailed analysis of the transient processes is performed in binary and ternary diagrams and a separation factor is introduced as a quantitative means of measuring for the effective relative volatility of the species. The observed differences suggest that non-ideal VLE have a significant impact on the droplet evaporation characteristics for complex hydrocarbon mixtures.