A CFD Prediction of Hydraulic and Cavitation Performance of a Vortex Pump as Turbine

Vortex pumps allow solid materials in the liquid pumped to pass through them and are subject to slight erosion in their hydraulic components compared with ordinary centrifugal pumps. Thus they have the potential to harness hydraulic energy in rivers with substantial debris and sediment and residual liquid pressure energy in solid-liquid two-phase flow processes in industry. However, whether this type pump can be used as turbine remains free from attack currently. In the paper, the non-cavitating and cavitating turbulent flows in a vortex pump with a specific speed of 76 were simulated by using CFD method when it operates as turbine. In the pump mode, its non-cavitating and cavitating performance predicted was compared with the experimental data. It is demonstrated that the vortex pump can operate as turbine to generate a certain shaft-power. Unfortunately, the best efficiency point in the turbine mode is farther from that in the pump mode, but the turbine cavitation performance is also much poorer than the pump mode. In the draft tube, the liquid is in rotation with the same direction as the impeller. Additionally, there is a cavitating vortex rope in the center of the tube. The cavitation performance improvement and cavitating vortex rope control may be the key problems to be solved in the future.