Droplet Vaporization in Turbulent Convective Flows With Temporal Variation of Pressure and Temperature

This paper presents a numerical model to investigate the effect of temporal variation of pressure and temperature on vaporization process of a single droplet exposed to a turbulent freestream of gaseous nitrogen. As a typical case, the evaporation rate and droplet life time of n-heptane droplet during adiabatic compression process and isobaric expansion process of a standard diesel cycle are investigated numerically. The numerical model is based on solving complete sets of time-dependent conservation equation of mass, momentum, energy, and species concentration in both gas-phase and liquid-phase. The turbulence terms in the conservation equations of the gas-phase are modeled by using the shear-stress transport (SST) model. The system parameters such as pressure and temperature at the beginning of fuel injection (i.e. represented by engine speed, RPM, and compression ratio, RC), and turbulence intensity are varied to provide a wide range of test conditions. To account for variation of temperature, variable thermo-physical properties, gas and liquid phase transients and radiation are considered. Also, the effects of high-pressure such as non-ideal gas behavior, solubility of gases into droplet and pressure dependence of gas- and liquid-phase thermo-physical properties are considered. Results of temporal variation of pressure and temperature are compared with those of isobaric and isothermal conditions.