Computational Analysis on Numerical Simulation of Internal Flow Physics for Pump as Turbine in Renewable Small Hydro Energy Generation

Abstract

Energy contributes significantly in almost all aspects of human life as well as economic activities and plays a crucial role in the infrastructural development of a county to alleviate poverty. Generating energy from a renewable source such as small hydropower through the application of pump operating as a turbine mode called Pump as Turbine is one of the best alternatives to provide clean and inexpensive energy. Using Pump as Turbine helps in generating reasonably priced hydroelectric power for communities in underdeveloped counties. This study investigates the effects of internal flow behaviour and performance of Pump as Turbine under different rotational speed and flow rate. The rotational speed is an essential physical parameter as it affects the Pump as Turbine operation. A model-specific speed centrifugal pump model with head 32 (m), flow rate of 12.5 (m3/h) and the rotational speed of 2900 rpm, has been selected for the study. Numerical simulations have been conducted using the k-ω turbulence model to solve three-dimensional (3D) equations. The pump mode experimental data were used to confirm the results for better analysis. The results predicted that vortex and turbulent kinetic energy increase per rotational speed increase. Also, at the higher rotational speed, very high recirculation of flow is detected at the blade suction chamber, although the pressure side has a smooth flow. This study provides beneficial information which will serve as a reference to help improve PAT performance along with selecting PAT for a small hydropower site. Future works will consider the impact of blade thickness and cavitation in Pump as Turbine.

Periodic Instabilities in a Specific Low-Speed Pump Working as a Turbine

“…Cavitation is an important source of instabilities, so it was included in the same query as instabilities. In this group, the following topics are addressed: geometry, efficiency, cavitation [4,[7][8][9][10][11][12][13][14][15][16][17][18][19][20][21], flow structures [8,[22][23][24][25], pressure fluctuations [16,21,26,27], vortex rope [27], energy losses when switching from pump to turbine mode [28], and application of entropy production theory for energy losses [29]. None of them addresses the measurement of instabilities.…”

Effect of valve opening on starting performance of pump as turbine

“…With increasing flow rate, the hydrodynamic force on the impeller and pressure fluctuations on the volute first decrease and then increase, reaching a minimum value near the design flow rate. Du et al investigated the internal flow behavior of a centrifugal pump operating as a turbine at different speeds and flow rates and analyzed the vortex behavior, turbulent kinetic energy, pressure, and velocity distribution [20]. The results showed that vortex and turbulent kinetic energy affected the internal flow at PAT, with flow instability and local flow structure at higher speeds and flow rates.…”