Phase change in fuel sprays at diesel engine ambient conditions: Modeling and experimental validation

•Modeling phase change in Diesel engine fuel sprays based on momentum balance and considerations of mass and heat transfer.•Experimental validation with elastic Mie scattering.•At low ambient conditions, fuel in sprays completely evaporates without boiling or getting supercritical.•At high engine-like conditions, fuel can be heated up to its boiling or critical temperature before evaporating completely.•Two-phase mixing happens in any engine-like spray case; however, at engine conditions, also one-phase mixing is relevant. [Display omitted] The nature of phase change in Diesel engine fuel sprays is not clear to this date. There are different stances on the question whether fuel or a fuel-rich phase can get supercritical (one-phase mixing) or not (two-phase mixing). The presented study utilizes an air entrainment model derived from momentum conservation to determine local mass ratios of ambient gas and fuel. Subsequently, two phase change models are formulated based on this model. On the one hand, the assumption is taken that fuel evaporates without boiling or getting supercritical. On the other hand, evaporation is excluded, assuming that fuel is heated up till boiling or getting supercritical. Both models allow the calculation of values for the liquid length of different fuel sprays. Comparison to experimental data shows that – although two-phase mixing is relevant in any case – at engine-like ambient conditions one-phase mixing is a relevant scenario.