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| Hump characteristic of reversible pumpturbine in pump mode |
| Tao Ran1, Xiao Ruofu1, Yang Wei1, Liu Weichao2 |
| 1.College of Water Resources and Civil Engineering, China Agricultural University, Beijing 100083, China; 2.Dongfang Electric Machinery Co. Ltd., Deyang， Sichuan 618000, China |
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Abstract To investigate the hump characteristic in dischargehead curve of reversible pumpturbines in pump mode, the internal flow field of a pumpturbine unit is simulated in its pump mode under different flowrate conditions by employing the detached eddy simulation (DES) method. The underlying mechanism for the hump characteristic is exploited by comparing the CFD and experimental characteristics of flow inside each passage of the unit, especially for the hydraulic losses in the diffusing passage and for the rotorstator interaction. The results show that the flow exhibits an obviously asymmetric pattern at the runner outlet as the unit is operated in the low discharge range. The asymmetric flow field is caused from the vortex and secondary flow generated in the diffusing portion of the runner passages. As a result, the hydraulic losses in the unit rise dramatically, causing a reduction in the pump head, eventually the hump characteristic occurs. Nevertheless, improving the flow pattern under the low discharge conditions can be very helpful to mitigate or eliminate the hump characteristic. The mechanism for the hump characteristic has been enunciated here. This may be referential and helpful to improve the hydraulic performance and conducive to enhance the operating stability of a reversible pumpturbine.
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Received: 16 December 2013
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