Study on the energy conversion characteristics in the impeller of ultra-low specific speed pump as turbine

Abstract With the increasing attention to micro-hydropower generation, pump as turbine (PAT) has broad prospects in the field of micro-hydropower generation due to low price and easy maintenance. The ultra-low specific speed has the advantage of large output power under a small flow rate and is widely used in remote areas to realize micro-hydropower generation. In this paper, With the goal of maximizing the output power at a small flow rate, an ultra-low specific speed pump as turbine (USSPAT) of 16.52 is designed. The energy characteristics inside the impeller are studied by means of experimental and simulation. It is found that the main output area in the impeller located in the inlet area of impeller and near Span0.6 area. In addition, it is found that the high-speed jet caused by RSI inside the impeller and the secondary circulation at the outlet area are the main flow structures that hinder the work of the impeller.