The mechanism of internal energy losses in double- suction centrifugal pumps under direct and reverse conditions

Abstract

The double-suction centrifugal pump has gained extensive application in various hydraulic projects and industrial processes under direct and reverse operating conditions. However, the occurrence of unstable flow phenomena, such as flow separation, vortex and reflux, poses a significant challenge to its hydraulic performance. Therefore, this paper aims to analyze the energy loss and energy dissipation mechanisms in double-suction centrifugal pumps operating in both direct and reverse conditions. By utilizing the entropy production theory, a combination of numerical simulations and experimental methods are employed to investigate the energy loss of double-suction centrifugal pump compared to double-suction centrifugal pumps as turbines. The findings indicate that the turbulent entropy production loss and wall entropy production loss are the principal contributors, accounting for over 57 % and 33 % of the total entropy production loss, respectively, under different flow conditions of the pump and turbine. Conversely, the direct entropy production loss is not more than 1 %. This suggests that the main causes of energy losses are associated with wall effects in the near-wall region and unstable flow in the main flow region. Within the pump conditions, the main components responsible for energy loss are the volute and impeller. Conversely, under turbine conditions, the impeller and draft chamber are the main contributors to energy loss. The presence of a suction chamber rib proves beneficial under pump conditions as it diverts and optimizes internal flow. However, the draft chamber flow divider exacerbates energy losses under turbine conditions. This study not only provides insights into the energy loss characteristics of a double-suction pump operating under direct and reverse conditions but also offers a fresh perspective on the structural optimization of both the double-suction pump and double-suction pump as turbine.