Study on cavitation of liquid nitrogen in pumps induced by coupling of pressure drop and external temperature

Abstract

A cryogenic pump is a kind of pump for transporting low-temperature fluid. The medium in the cryogenic pump is prone to cavitation. To study the cavitation of liquid nitrogen in the pump induced by the coupling of pressure drop and external heating, the Zwart cavitation model and SST k-ω turbulence model were used, and the functional relationship between saturated steam pressure and the temperature was imported into CFX software by CEL language for the solution. The external characteristics and internal flow of the cryogenic pump at different inner wall temperatures of volute were analyzed. The results show that when the temperature of the inner volute wall is above 128 K at the inlet pressure of 0.078 MPa, the pressure distribution in the volute changes significantly, the head and efficiency of the cryogenic pump decrease significantly, and the external temperature has a significant impact on the performance of the cryogenic pump. When the temperature of the inner volute wall is lower than 128 K, the temperature of the inner volute wall has little effect on the pressure distribution in the volute. Due to the heat absorption of cavitation, the temperature of the cavitation area in the impeller decreases. The influence of inlet pressure on the temperature distribution in the volute can be ignored. Affected by the external temperature, the high-temperature area in the pump is mainly distributed near the volute tongue and the inner volute wall, and the cavitation area in the volute is also distributed near the same position. The vapor volume fraction in this area increases with the inner wall temperature. The research results have reference values for selecting thermal insulation measures and improving cavitation resistance.