Analyzing the Inlet Gas Void Fraction on the Flow Characteristics for a Multiphase Pump Based on Cavitation Cases

Abstract

Inlet gas void fraction (IGVF) affects the cavitation evolution in a multiphase pump and easily results in a drop of the head and efficiency when cavitation is more serious. In this paper, a numerical method was performed to qualitatively and quantitatively analyze the effect of the inlet gas void fraction on the pressure and velocity characteristics of the multiphase pump at different cavitation stages. The results show that with the increase of IGVF and the development of cavitation, the pressure in the impeller flow passage is reduced, and the pressure corresponding to the cavitation region drops sharply to the saturated vapor pressure. With the decrease of the cavitation coefficient, and due to the expulsion effect of the cavitation bubbles, the relative velocity in the cavitation region becomes larger. Because of the large pressure gradient at the end of the cavitation bubbles, the kinetic energy of the fluid is insufficient to overcome the effect of the inverse pressure gradient, resulting in a backflow vortex. Investigations on cavitation evolution in the multiphase pump at different IGVFs are of great significance for improving its performance.

Keywords

• cavitation evolution
• gas-liquid two-phase
• cavitation stage
• CFD
• velocity distribution
• backflow vortex