Examination on behavior of tip leakage flow in a three-stage gas-liquid two-phase flow pump

Abstract

Tip leakage flow (TLF) trajectory in a pump with gas entrainment is investigated via visualization experiments and numerical simulations. Starting position of tip leakage vortex (TLV) is determined accurately by numerical simulation. Under high liquid flow rate (Q_l) and high inlet gas volume fraction (IGVF) conditions, TLF flows from suction surface to pressure surface near the leading edge of blade, and the direction of TLF gradually changes along the chord which flows from pressure surface to suction surface near the tailing edge. The angle between TLF and blade mean camberline increases progressively as either Q_l or IGVF decreases, and starting position of TLV moves towards leading edge direction. As Q_l or IGVF decreases, value of vorticity increases and high vorticity region moves towards leading edge. The entropy production rate at blade tip clearance is high, and entropy diffuses from pressure surface to suction surface due to jet flow in blade tip clearance. The greater the amount of accumulated gas there is, the greater the amount of entropy in the area. In addition, when gas is entrained in pump, there are many low frequency fluctuations generated in blade tip clearance.