Study on hump characteristics of pump turbine with different guide vane exit angles

In order to study the influence of different guide vane outlet angles on the external characteristic hump phenomenon under the pump mode of pump turbine with splitter blades, the pump work condition of a pump turbine model pump of a pumped storage generator unit in China was studied. Three different guide vane outlet angle models of 9.6, 17.5 and 25.6 were selected to discuss the variation law of hump characteristics with the guide vane outlet angle under the pump working condition, and the internal flow pattern of the draft tube, impeller and guide vane region was studied. The results show that the calculated external characteristic curves of the three different guide vane exit angles are in good agreement with the test results under the corresponding working conditions. With the increase of the guide vane exit angle, the hump phenomenon becomes more and more obvious and appears earlier, and the smaller the guide vane exit angle is, the higher the head is. There is no wide high efficiency region under the small guide vane exit angle, and the high efficiency region widens as the guide vane exit angle increases. There are secondary flow and backflow in the vane rotating passage, and a large number of whirlpools exist in the guide vane basin. Due to the existence of these bad flow state, the flow loss is greatly increased and the head is reduced, which eventually leads to the hump phenomenon of the external characteristic curve.