Prediction method of centrifugal pump running in turbine mode based on losses analysis

Abstract

Interest of Pump as Turbine (PAT) is growing with diverse applications in engineering. Usually, the data of PATs are not available in the hands of pump manufacturers. Therefore, performance prediction methods appear as an important research area of PATs. The current prediction methods reposed on expensive, inaccurate and time consuming experimental methods. In the scope of this work, a generic and robust prediction method is built up for a centrifugal impeller PAT. The most significant hydraulic losses were derived in PAT mode, these are namely, the shock losses at the impeller inlet, the swirling losses at the impeller outlet and the impeller wall frictional losses. The Euler head, the available total head and the hydraulic efficiency were computed as well. The global efficiency was computed taking into account the machine mechanical and volumetric efficiencies, enabling therefore to perform comparison of the new prediction method with experimental, computational fluid dynamic (CFD), Rossi and Perez performances prediction methods. From where it resulted a good agreement between the given prediction methods for the entire range of operation, confirming the robustness and the applicability of the developed prediction method. The relative difference between the new prediction method and CFD data and between the new prediction method and experimental data remained higher for lower discharge conditions, notably for extreme part load conditions, where a small error could result in very high relative difference.