Numerical Investigation of the Effect of Adding Stay Blades on Improving the Performance of Centrifugal Pump as Turbine

With the changing patterns of energy consumption and the emergence of economic and environmental issues, renewable energy production has received a lot of attention all over the world. Micro-hydropower plants that utilize pumps as turbine (PAT) instead of traditional turbines offer unique advantages such as low construction and maintenance costs, and short commissioning time. In the present study, the design and simulation of a centrifugal PAT were performed using CFturbo and CFX software. The governing equations were discretized using the finite volume method, and the k-ω SST turbulence model was employed for numerical analysis. The performance curves of simulated PAT show acceptable agreement with experimental results. Since pumps are not designed for reverse operation and lack equipment to guide fluid flow from the volute to the impeller, significant losses occur, particularly under off-design operating conditions. In order to improve the PAT performance, diffusers equipped with stay blades were designed for implementation in the space between the impeller and the volute, and the effect of the number of stay blades on operating range was numerically investigated. Results indicate that the PAT equipped with a 10-blade diffuser exhibits more uniform turbulent kinetic energy distribution and provides a wider operating range with high efficiency. Besides, the PAT efficiency at the design point has increased by 2.7%.