Geometry Optimization of Two-Phase Supersonic Steam Ejector Based on Homogeneous Equilibrium Model

Abstract

Currently, the ideal gas model was popular to be taken as the geometry optimization approach with the development of ejector, which was lack of consideration of phase transition and condensation process. In this paper, a two-phase flow model— homogeneous equilibrium model (HEM) model was established to simulate the complex flow phenomenon in the steam ejector. Furthermore, a new method for optimizing steam ejectors was proposed based on the HEM model. Sensitivity analysis was conducted on all geometric parameters of the steam ejector, and find those that have a more significant impact on the entrainment ratio of the steam ejector through orthogonal tests with eleven-factor and three-level. It was concluded that the area ratio Amix/Ath is the most sensitive factor affecting the ejector performance. The key geometric parameters were selected for optimization and the entrainment ratio of the optimized ejector is 96.4% higher than that of the initial ejector. Finally, the variable working condition analysis was carried out on the optimized ejector. The performance results show that at a fixed primary pressure, critical back pressure (CBP) and entrainment ratio (ER) at critical mode increase almost linearly with increasing secondary pressure, and separate linear regressions empirical formula were obtained for them, respectively.

Keywords: Steam ejector, two-phase flow, HEM model, Orthogonal test, linear regression equation