Critical flashing flow in convergent–divergent nozzles with initially subcooled liquid

Abstract

Investigation on critical flashing flow of initially subcooled water in convergent–divergent nozzles is carried out in this paper. A two-dimensional axial symmetric model is developed. In this model, the explosive flashing process immediately downstream the throat is modeled as an oblique evaporation wave, and the velocity direction change of the supersonic flow downstream the oblique evaporation wave is regarded to be resulted by an oblique shock wave. The further fluid expansion in the divergent section is assumed to be in Isentropic Homogeneous Equilibrium (IHE) except near the throat. The results show that the pressure immediately downstream the throat predicted by Abuaf's model is very close to the experimental result, about 4% deviation from Akagawa's tested value. Non-homogeneous equilibrium region exists downstream the oblique evaporation wave near the throat in the divergent section. The length of the non-homogeneous equilibrium region is increased as the inlet subcooled degree is increased. The pressure profile predicted by the model agrees very well with the tested profile of Akagawa except in the non-homogeneous equilibrium region near the throat.