Research on energy conversion characteristic of pump as turbine

Pump as turbine is a device for energy conversion. To master the characteristics of energy transformation, especially within impeller, plays important roles for further optimum design of pump as turbine. In order to analyze the energy-changing features in detail using computational fluid dynamics, the impeller is divided into six regions by the radius. Under different operating conditions, the variations of power in the different radial cross-section of the impeller, the input net energy in different regions of the impeller, and the energy from the fluid to the impeller were demonstrated. The results show that the pressure energy of fluid is primary for impeller work, instead of the kinetic energy; the front and middle regions of the impeller (about the area of (0.6–1.0) D 2 ) are important parts for energy conversion; in the rear area of the impeller, it acquires little energy from fluid relatively, what’s more, the fluid not only does not work to impeller, but also consumes the impeller mechanical energy under the large flow conditions. So this research may point out the direction for optimization design of the impeller blade.