Abstract: A pump in reverse as turbine has wide application. Besides renewable energy power generation, it can also be used for high-pressure residual energy recovery in high-energy-consumption industries, but generally with a low hydraulic efficiency. To improve its efficiency, the CFD method can be used to optimize its hydraulic performance in combination with the design theory of hydraulic turbines. This study optimizes the impeller of a centrifugal pump as turbine using an orthogonal experimental method, and applies it to seawater desalination energy recovery with a rated speed of 12000 r/min and certain external dimensions limited. We examine the optimized turbine in detail, using experimental and numerical methods and focusing on its hydraulic performance and flow characteristics. Results show that compared with the initial design, the orthogonally optimized design is improved evidently in its impeller’s flow separation and vortex flows and its hydraulic efficiency. The calculations of performance characteristic curves agree well with the tested trends. At the rated speed, with the increasing water head, its hydraulic efficiency increases first and then decreases; its optimal hydraulic efficiency is 85.5%. Under partial working conditions, the farther away from the optimal point, its hydraulic efficiency will be reduced accordingly, and its internal flow state will become more complex.

Key words: hydraulic turbine, impeller, orthogonal optimization, numeral calculations, performance characteristic curve