Mechanism study on pressure fluctuation of pump-turbine runner with large blade lean angle

Excessive pressure fluctuations in the vaneless space can cause mechanical vibration and even mechanical failures in pump-turbine operation. Mechanism studies on the pressure fluctuations and optimization design of blade geometry to reduce the pressure fluctuations have important significance in industrial production. In the present paper, two pump-turbine runners with big positive and negative blade lean angle were designed by using a multiobjective design strategy. Model test showed that the runner with negative blade lean angle not only had better power performance, but also had lower pressure fluctuation than the runner with positive blade lean angle. In order to figure out the mechanism of pressure fluctuation reduction in the vaneless ;jik8space, full passage model for both runners were built and transient CFD computations were conducted to simulate the flow states inside the channel Detailed flow field analyses indicated that the difference of low-pressure area in the trailing edge of blade pressure side were the main causes of pressure fluctuation reduction in the vaneless space.