Research on performance failure caused by gas blocking in multiphase mixed-transport pump under non-uniform inflow conditions

The helical-axial multiphase mixed-transport pump fails due to gas blocking caused by gas-liquid separation caused by cavitation under complex conditions with high gas volume fraction. This is an urgent engineering problem that needs to be addressed in the application of this pump. In order to simulate the flow structure characteristics in the channel, two types of non-uniform inflow boundary conditions are introduced. The bubble structure, velocity, and pressure of the inflow conditions under different operating conditions are compared and analyzed, and the variation rules affected by the non-uniform boundary conditions are obtained. At the same time, the internal flow characteristics and mechanisms of helical-axial multiphase mixed-transport pump are analyzed based on the velocity changes at the inlet of the impeller and the pressure fluctuations at the outlet of the diffuser, leading to the intensification of gas-liquid separation and eventually the development of gas blocking. Research has shown that by changing the flow boundary conditions through the UDF program, it has been found that the linear change in inlet pressure has a more pronounced effect on the gas-liquid separation in the flow channel of the mixed-transport pump than the sinusoidal change, leading to a serious decline in pump performance when gas blocking occurs, until failure. When the inlet gas content is 10%, with the increase in flow rate, the head of the linear boundary condition decreases significantly at 0.95 Q/Qd\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$Q/Q{\text{d}}$$\end{document} Along the axial direction of the flow channel, the velocity disturbance of the linear boundary condition is significant on the suction surface of the blade, and the low-pressure area inside the flow channel is 30% higher than that of the sinusoidal boundary condition. The research conclusion can provide reference value for solving the problem of gas blocking in engineering applications of helical-axial multiphase mixed-transport pump.