PERFORMANCE ANALYSIS OF FRANCIS PUMP-TURBINE RUNNER WITH ADJUSTABLE BLADE USING COMPUTATIONAL FLUID DYNAMICS

Abstract

One of the most common energy storage system that is used for stabilising the grid is Pumped Hydroelectric Storage (PHES) system. Although PHES has been used for a long time, most of the existing PHES cannot vary the amount of electricity that they can store from the grid. This will cause a problem when the grid has a high penetration of wind and solar energy. There are few solutions that have been suggested, but all of them require additional big machine and space which make it not a practical solution for existing PHES power plant. This research proposes a new mechanism that can be introduced to a Francis pump-turbine runner which can improve the operational flexibility of the machine when it is operating as a pump at PHES plant. The design started off from an existing turbine runner and some modifications were made to allow the blade tip to be adjusted, enabling the turbine to change the pump power whilst operating at a fixed rotational speed. All the research works are based on Computational Fluid Dynamics (CFD) simulation. Based on the research done,this mechanism does not affect significantly the efficiency of the runner in turbine mode and was able to vary the pump power ranging from -30.77% to 16.67% without cavitation. The round-trip efficiency obtained in this research was 78.33% - 78.62% which is comparable to the existing PHES power plant of 75%- 85%.