The role of changing runner geometry in expanding energy efficiency of a centrifugal pump as turbine (PAT)

• Cost-effective generation of clean energy in the pressure-reducing station using centrifugal PAT . • The effect of using a runner with forward blades on PAT efficiency is examined. • Research is done on the effects of blade-leading edge rounding on PAT efficiency . • The analysis of changing blade thickness on the performance of centrifugal PAT is investigated. • Special runner design reduces flow losses and improves performance in the entire working range. Escalating global energy demand and environmental challenges have created a paradigm shift toward expanding the capacity of renewable energy power plants. The utilization of centrifugal PATs is an economically viable approach for producing clean energy in pressure reduction stations. This study evaluates PAT performance with experimental and numerical approaches. It verifies the validity of numerical solutions by comparing them with the experimental results. Analysis of the PAT performance shows that the absence of a control mechanism to guide the inlet fluid into the runner results in separation and vortex formation within the passages, and the efficiency significantly decreases. A new runner is designed by modifying three blade parameters, including thickness, leading edge , and curvature, to improve hydropower performance within its operating range. Investigating flow fields shows that a special runner reduces adverse flow phenomena, such as blade inlet shock, flow separation, and vortex formation within the flow passage. As a result of reduced losses and improved efficiency, PAT performance increases across the whole working range. The results indicate that the efficiency of PAT with a special runner at low-load condition (0.8Q d ), design condition (1.0Q d ), high-load condition (1.2Q d ), and over-load condition (1.3Q d ) is raised by 2.58%, 3.04%, 7.23%, and 4.53%, respectively.