An enhanced multi-component vaporization model for high temperature and pressure conditions

An enhanced multi-component vaporization model was proposed to simulate the vaporization process of fuel droplets under high ambient temperatures and pressures. In the present model, the heat flux of conduction, enthalpy diffusion, and radiation absorption in the gas phase are calculated by Fourier's law, the multi-component diffusion sub-model, and a simplified analytical solution of the radiative heating, respectively. A surface temperature sub-model was employed to evaluate the average temperature within the droplet and the surface temperature of the droplet. For calculation of vapor-liquid phase equilibrium, a real and an ideal gas approach was used for high and low ambient temperatures and pressures, respectively. Moreover, the dependence of gas physical properties on temperature and pressure is also considered. Based on the enhanced vaporization model, extensive verifications for different multi-component droplets were conducted, and the results indicate that satisfactory agreements between the predictions and measurements can be achieved. Finally, the multi-component vaporization model was applied to investigate the vaporization characteristics of practical fuel droplets with a wide range of diameters at high ambient temperatures and pressures, and the effects of radiation absorption and real gas behavior on the vaporization process were understood. It is found that the influence of radiation absorption on the vaporization behavior strongly depends on the droplet diameter and the ambient temperature, and the effect of ambient pressure on the average vaporization rate is determined by the ambient temperature. Considering the compromise between computational accuracy and efficiency, a pressure criterion (P′) was introduced for the choice of ideal or real gas approaches, and a diameter criterion (D′) was also defined to decide whether to consider the radiation absorption in the vaporization model.