Numerical prediction on overall performance of double suction pump reverse running as turbine
CHEN Tie-Jun, GUO Peng-Cheng, LUO Yi, WU Yu-Lin
(1. Institute of Water Resources and Hydroelectric Engineering, Xi′an University of Technology, Xi′an, Shaanxi 710048, China； 2.State Key Laboratory of Hydroscience and Engineering, Tsinghua University, Beijing 100084, China)
Abstract：To study the behavior of a double suction pump with guide vanes when running as a turbine, the performance of the pump was predicted by using the SST k-ω turbulence model; meanwhile, the performance in turbine mode was investigated as well, especially in the braking pump mode and reverse rotation pump mode. It was shown that the pump efficiency at the rated point is 89.3% and the peak efficiency in turbine is as high as 90.5%; moreover, when the head is more than 200 m, the turbine can keep a higher efficiency over a wider flow rate range. The head curve in pump mode doesn′t show a positive slope at all; in turbine mode, however, the curve exhibits a "S" shape zone, suggesting a turbine shouldn′t be operated in that zone. The flow patterns in the runner are smooth and there is no reverse or separation phenomenon in the pump and turbine modes at the duty points. The passage between the runner and the double suction pipe is so narrow that the flow swirls strongly there. When the pump is operated in reverse rotation and braking pump modes, the reverse flow in the runner leads to stall phenomena. It is necessary to consider that cavitation may occur in turbine mode, for operation safety occurrence of cavitation should be avoided.
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