The effect of fixed blades installation angle on the high-efficiency operating range of a centrifugal pump as turbine

Articles in Press

Document Type : Article

Authors

1 Faculty of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran

2 Faculty of Mechanical Engineering, Iran University of Science and Technology, Tehran, Iran.

10.24200/j40.2025.66460.1735

Abstract

In light of the depletion of fossil fuel resources and the environmental challenges of traditional power plants, the development of renewable and sustainable energy technologies has gained significant importance as a strategic solution to meet growing global energy demands and mitigate the consequences of climate change. Using the pump as turbine (PAT) for energy recovery in micro hydropower plants installed in water distribution networks and water supply systems has received considerable attention in recent years as an efficient and economical approach. The implementation of this technology enables pressure regulation and cost-effective electricity generation, potentially playing a key role in the development of renewable energy sources and meeting peak load demands in electrical grids. This study investigates the performance of a centrifugal PAT both numerically and experimentally within its operational range. For numerical analysis, design and simulation processes were conducted using CFturbo and CFX software. The finite volume method was employed for discretizing the governing flow equations, and considering the turbulent nature of flow in PATs, the shear stress transport (SST) turbulence model was employed. The validity of numerical simulations was confirmed by comparing them with experimental results. Due to the absence of a flow control mechanism at the impeller inlet, a significant efficiency reduction is observed compared to the pumping mode, particularly under off-design conditions. To enhance PAT performance, a diffuser with fixed blades was designed, and the impact of stationary vane angles on turbine performance was numerically analyzed by varying angles between 15° and 35°. For performance analysis with different fixed blade angles, the turbulent kinetic energy parameter was utilized, revealing that the angle significantly affects both the distribution and magnitude of turbulent kinetic energy. Turbulence intensity was found to concentrate more prominently in the impeller and the volute tongue, while a more uniform distribution was noted within the volute. Comparison of turbulent kinetic energy contours indicates that in a PAT with fixed blades at an angle of 25°, the distribution is more uniform, leading to an efficiency improvement of 2.63% at the design point.

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Sharif Journal of Mechanical Engineering

Articles in Press, Accepted Manuscript
Available Online from 26 October 2025

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