Numerical study on void fraction wave of reciprocating multiphase pumps with high gas rates based on real gas models

Instantaneous gas-liquid flow and distribution have an important influence on the performance of a multiphase pump, especially under the high gas content conditions. How to accurately simulate the complete working cycle of a multiphase pump and reflect the transient oil-gas flow inside the pump cavity are the main difficulties of the study. A three-dimensional whole-cycle numerical simulation has been conducted to predict the void fraction waves of the reciprocating multiphase pumps under the high gas rates and to evaluate the effects of multi-case parameters on its pulsation characteristics. The instantaneous two-phase distribution and fluctuation characteristic accompanying the movement of the piston and the valves during each process of the multiphase pump are innovatively obtained under the high gas rates. Five different ideal gas model and real gas models used in this simulation are compared and optimized first, and then validated by the experimental results. Void fraction wave signals in the time and frequency domains are obtained from multiple working cycles of the multiphase pump, and the pulsation rates, propagation speeds, amplitudes, and power spectral densities are analyzed in great detail under different inlet gas contents, pressure ratios, crank speeds, and stroke lengths.