Flow loss characteristics of radial split doublesuction pump as turbines

ZHAO Wei1, LIN Tong1,2,3, WEN Xiaoming1, CHEN Lei1, ZHU Zuchao3

(1.School of Mechanical and Electronic Engineering, Jiangxi College of Applied Technology, Ganzhou 341000, China; 2.Key Laboratory 
of Ionic Rare Earth Resources and Environment, National Ministry of Natural Resources, Ganzhou 341000, China; 3.National-Provincial 
Joint Engineering Laboratory for Fluid Transmission System Technology, Zhejiang Sci-Tech University, Hangzhou 310018, China)

Abstract:  The double-suction centrifugal pump has the disadvantage of a narrow operating range and low efficiency under the pump as turbines (PATs) operation conditions. The flow loss characteristics of radial split double-suction PATs was investigated in this manuscript based on the background of practical engineering applications. Firstly, the hydraulic performance of pump and turbine in typical operation conditions of PATs was predicted by the numerical simulation method. The accuracy and reliability of the numerical simulation method applied was verified by comparing the experiment results under the pump condition. Then, the entropy generation theory was adopted to obtain the quantitative analysis of the weight of the various flow components for the loss of the PATs system and the proportional distribution of the fluid components. Finally, the internal fluid characteristics were analyzed under the typical operation conditions to reveal the location and cause of fluid loss in the main flow components. The research results illustrate that the wall entropy production is the main cause of internal flow loss in radial split double-suction PATs. Under the operating conditions of 0.8Qb, Qb, and 1.2Qb, the wall entropy production respectively accounts for 55.3%, 69%, and 67.4% of the total entropy production. The export chamber is the hydraulic component with the highest proportion of entropy production inside the PATs. The main reasons for the increase in turbulent entropy production are adverse flow characteristics such as local backflow and flow shock. The research results have certain reference significance for optimizing design, regulating operation, and promoting industrial hydraulic turbines.
Key words: double-suction centrifugal pump; pump as turbines (PATs); energy loss; internal flow; numerical simulation; entropy generation theory