The impact of blade inlet angle (β2) influence on pump-as-turbine performance by using entropy production theory

The effect of the blade inlet angle on the pump-as-turbine (PAT) has not been adequately investigated. The hydraulic performance of PAT was analyzed using an available test rig. The accuracy of the numerical data was established by the comparative analysis of the experimental data. The study demonstrated that as the blade inlet angle increases, so does hydraulic performance, but only to a certain degree. The required pressure head and the shaft power increased with the increase in blade inlet angle. As compared to the volute and outlet pipe, the hydraulic power loss within the impeller accounts for a large portion of the total power loss. The impeller power loss decreases and increases at low and high flow rates, respectively, as the blade inlet angle increases. The fluid angle of attack decreases as the blade inlet angle increases at high flow, allowing the impeller power loss to drop and performance to increase. To visualize PAT internal energy loss, the distribution of the variable of pressure, velocity, and entropy dissipation theory was applied. The impeller had the highest energy loss of the PAT geometrical parameters. The shock loss, flow separation, and asymmetric volute structure are the primary causes of impeller loss. The unsteady simulation results showed that rotor-stator interaction greatly influences the gap between the volute tongue and the impeller tip. The research results provide a reference for the design of the PAT.