Experimental and numerical investigations on pressure pulsation in a pump mode operation of a pump as turbine

Abstract

AbstractHydropower has been the leading renewable source and cheapest ways to generate electrical energy in the world. In recent years, there has been a major upsurge in the hydropower development because of the use of pump as turbine (PAT). However, the operational reliability of a PAT is greatly affected by the unsteady flow fields; therefore, it is important to examine the unsteady flow behavior which can be used as a reference to reduce the noise, vibration, and cavitation performance for centrifugal pumps working as turbines. Thus, the objective of this study was to evaluate the unsteady flow fields by analyzing the distribution of the pressure pulsations using both numerical and experimental measurements in a PAT operating in pump mode. Firstly, the three‐dimensional (3D) unsteady flow equations were solved using SST k‐ω turbulence model during the numerical calculations. Secondly, the numerical results of the hydraulic pump performance were validated by the experimental measurements for numerical accuracy. Lastly, pressure transducers are positioned at certain monitoring points to measure the pressure in the PAT investigated. The numerical and experimental results show that the main frequency of the pressure pulsation is equal to the blade frequency, and as it deviates from the design operating condition, the magnitude of pressure pulsation intensifies. Furthermore, the impeller eye marked the lowest pressure coefficients especially at the design condition and makes it highly susceptible to cavitation. High pressure coefficients were obviously seen at the pressure side on the blade surface closer to the trailing edge at all studied operating conditions. Meanwhile, the rotor‐stator interaction generated the highest pressure pulsation distribution at the volute tongue. Thus, modification of the volute tongue is an optimal approach of reducing the pressure pulsation intensity in the volute and pump as a whole.