Dynamic characteristics of the tip leakage vortex in an oil-gas multiphase pump based on vorticity decomposition theory

The paper combines experimental and numerical simulation methods to investigate the tip leakage vortex (TLV) in an oil-gas multiphase pump. The study aims to understand the evolution and dynamic characteristics of the TLV. The vorticity decomposition theory is used to analyze the spatial-temporal evolution, transient behavior, and rigid vorticity of the TLV. The findings reveal that the TLV is formed near the pressure surface when the tip clearance jet passes through the shear layer. In one impeller rotation period, transient fluctuations of the TLV are attributed to pressure differences and velocity changes across the tip clearance, and the TLV undergoes two split-dissipation-recurrence processes within one impeller rotation cycle. The presence of the gas phase enhances the scale and strength of the TLV while prolonging its existence in the flow channel. Analysis based on the rigid vorticity transport equation shows that the growth of the TLV and collapse are primarily governed by the rigid vortex generation term. The Coriolis force term contributes to stabilizing the TLV, while the rigid vorticity stretching term affects its shape. Furthermore, the gas phase significantly increases the value of the Rigid vorticity Curl of pseudo-Lamb vector Term (RCT), which plays a crucial role in the prolonged existence of the TLV under gas-liquid two-phase conditions. From an inlet gas void fraction of 0%-20%, the RCT value increases by 4.8 x 106/s2, the entropy production value increases by 75.55%, and the hydraulic efficiency decreases by 16.29%. Transient of vortex in the impeller (rigid vortex), the model of the multiphase pump, transient evolution of tip leakage vortex, analysis of vortex dynamic characteristics, distributions of the term in the rigid vorticity transport equation from the impeller, the Rigid vorticity Curl of pseudo-Lamb vector Term, and energy loss and hydraulic efficiency of the multiphase pump. image