Enstrophy dissipation of the tip leakage vortex in a multiphase pump

Abstract

Tip clearance is the distance required between the blade tip and the pump body wall of the impeller in the multiphase pump, of which the resulting tip leakage vortex (TLV) causes unstable flow, leading to energy dissipation. However, only a few studies have been made on the energy dissipation caused by the TLV, and the internal mechanism of energy dissipation has not been revealed. In the present work, enstrophy dissipation theory is innovatively applied to quantitatively study the energy dissipation of the TLV in impeller, to provide guidelines for controlling energy dissipation associated with the TLV, and to optimize the design of the multiphase pump. The location, mode, and energy dissipation rate caused by the TLV are analyzed. The relationship between vorticity and the enstrophy dissipation rate is summarized, and the energy dissipation law is revealed during the inception, development, and dissipation of the TLV. The present analysis indicates that the vorticity is highest at the core of the TLV and gradually weakens along the radial direction with the vortex core at the center; the enstrophy dissipation, however, presented the opposite distribution law. The enstrophy dissipation rate changes as the spatialtemporal evolution of the TLV. The gas phase significantly deteriorates the flow pattern of the TLV, enhances the volume enstrophy dissipation rate, and reduces the wall enstrophy dissipation rate. The volume enstrophy dissipation power increases by 45.33% with an inlet gas void fraction of 10%, the wall enstrophy dissipation power decreases by 23.90%, and the total enstrophy dissipation power increases by 17.21%.