ID 94

Numerical simulation of transient flow under superheated conditions by different thermal assumptions

 

Abstract:

Flash-boiling is a promising way to improve spray atomization quality because of its superior breakup efficiency and finer droplet size. However, the quick evaporation phenomenon with liquid-vapor phase coupling is still not fully understood due to the complexity of the multi-phase flow. In this paper, two thermal physical models are developed to deal with the phase change process. The first model assumes that each phase of the mixture is under thermal equilibrium, and the other one considers the liquid phase as superheated while the vapor phase in its saturated state. In order to characterize the influence of the thermal state of the mixture, a numerical simulation of the flash-boiling flow modeling water-steam mixture in a sudden depressurization condition has been conducted using these two different methods with a homogeneous relaxation model. The results have been compared and shows that the two methods predict a similar flow velocity distribution and mass flow rate. The difference between the two methods mainly lies in the temperature distribution of each phase, which consequently results in different vapor mass generated. In addition, the speed of sound of the mixture and each single phase have also been investigated to show the influence of compressibility of the mixtures on pressure and evaporation propagation.