Transient cavitation characteristics of a special mixed-flow turbopump

In order to investigate the transient characteristic of pump hydraulic pressure system, mathematical models of the equipment transient velocity and pump transient speed were established based on the experimental data. The cavitation characteristics at 0.73, 0.90 and 1.00 s moments during the pump starting transient process were analyzed. Numerical results show that distribution of cavitation bubble volume fraction in the suction side of blades at the different net positive suction head (NPSH) conditions is similar. The volume fraction of cavitation bubble increases sharply from the span of 0.7 to 1.0, and reaches the maximum value at the rim. At the time when the equipment gets out of cabin, the average cavity fraction in the rim circumferential surface is about 33% at the condition of the available not positive suction head (NPSH) Na=14.23 m. In this case, the cavitation bubbles block the flow channels, which results in the sharp drop of the pump head, and will affect the equipment acceleration. The experimental results show that the pump rotating speed is accelerating approximately linearly after the starting of the pump hydraulic pressure system, and the NPSH value of the pump increases rapidly with increasing speed of the turbopump. The rotation speed, flow rate and the net positive suction head required (NPSHR) all reach the maximum values at the equipment extravehicular moment, so the smallest submerge depth should be limited to avoid accidents induced by cavitation.