Bidirectional flow diagnosis to optimize the design of a pump-turbine runner using vorticity dynamics theory

The bidirectional flow in a pump-turbine runner was analyzed using a vorticity dynamics based method. In this method, the runner design is related to the work applied by the blade. The integral of the total pressure work normal to the streamline was analyzed to understand the variations of the pressure work with blade position and the effect of blade position on the total pressure work. The flow diagnosis results are used to modify the distribution of circulation to improve the efficiency and cavitation performance of the pump-turbine runner. Numerical experiments show that for the pump working condition, the runner efficiency is 91.3% and 92.1% before and after the improvement, while for the turbine working condition, the runner efficiency is 91.9% and 92.4% before and after the improvement and that the cavitation coefficient is reduced by 0.012 after the modification.