Influence of valve's lag characteristic on pressure pulsation and performance of reciprocating multiphase pump

Reciprocating multiphase pump is the key equipment for the oil-gas transport technology in the petroleum industry. The opening and closing motions of suction and discharge valves directly affect the transport performance and stability of pump. In this paper, the whole working cycle of reciprocating multiphase pump is studied by using computational fluid dynamics (CFD) method. The combined actions of piston, suction and discharge valves are dealt with User Defined Functions and dynamic grid technique. Based on the instantaneous motions of valves, the lag characteristics of suction and discharge valves under different working conditions are analyzed. And the influences of lag angles on the pressure pulsation, P-V diagram and input power of the pump are further investigated. The results show that the lag angles have a significant impact on the internal and external characteristics of the reciprocating multiphase pump. Due to the most obvious opening lag angle of discharge valve, the pump pressures and P-V diagram have the sudden fluctuations just after the end of compression process, which appear in the range of θ = 240.7°-273.1° for the initial condition. The gas volume fraction (GVF) plays more important role than the suction and discharge pressures in the working of reciprocating multiphase pump, and the opening lag angles of suction and discharge valves at GVF = 0.9 increase to more than 6 times at GVF = 0.1. By the comparisons of input power, the simulated results for reciprocating multiphase pump show good agreement with the results of prototype test. This study would provide a theoretical basis for the design of high-efficiency multiphase pump and valve.