基于熵产理论的水泵水轮机反S区水力损失机理分析

水泵水轮机在水轮机工况运行时易进入反S不稳定区，影响机组的安全稳定运行。传统压差法在计算水力损失时不能获得损失的具体分布和详细来源，因此水泵水轮机在反S区水力损失机理仍有待深入研究。本文采用雷诺时均方法对某原型抽蓄电站水泵水轮机在活动导叶开度分别为12°和35°下的反S区运行工况进行了数值模拟，基于熵产理论对各个过流部件和不同类型的水力损失进行了定量分析，并结合流场分布情况进一步明确了水力损失的分布特点和产生原因。结果表明，水泵水轮机进入反S区会引起导叶段水力损失占总水力损失的比例逐渐增大，而转轮段水力损失逐渐减小。在不同类型的能量损失中，湍流熵产占据主导，壁面熵产次之，直接熵产最小。随着水泵水轮机进入深度反S区，转轮区湍流熵产损失较大区域从转轮进口的叶片压力面转移到转轮出口叶片吸力面。水泵水轮机位于反S区时，转轮对水流做功输入能量，使无叶区总压大幅上升，活动导叶开度增大会显著增大无叶区水流能量幅值。

Analysis of hydraulic loss mechanism in inverse S-shaped region of pump-turbine based on entropy generation theory

When the pump turbine is operating in the turbine condition,it is easy to enter the unstable inverse S-shaped region,which affects the safe and stable operation of the unit.The traditional differential pressure method cannot obtain the specific distribution and detailed source of the hydraulic loss when calculating the hydraulic loss,so the hydraulic loss mechanism of pump turbine in inverse S-shaped region still needs to be further studied.In this paper,the Reynolds time-averaging method is used to simulate the operating conditions in the inverse S-shaped region of a prototype pump turbine with the movable guide vane opening of 12° and 35° respectively.Based on the entropy generation theory,the hydraulic losses of each flow components and different types are quantitatively analyzed.Combined with the distribution of flow field,the distribution characteristics and causes of hydraulic loss are further analyzed.The results show that when the pump turbine enters the inverse S-shaped region,the proportion of the hydraulic loss in the guide vane section to the total hydraulic loss increases gradually,while the hydraulic loss in the runner section decreases gradually.Among different types of energy loss,turbulent entropy generation is dominant,followed by wall entropy generation,and direct entropy generation is the least.As the pump turbine enters the deep inverse S-shaped region,the area with large indirect entropy production loss in the runner zone shifts from the blade pressure surface at the runner inlet to the suction surface at the runner outlet.When the pump turbine is located in the inverse S-shaped region,the runner does work on the water flow and inputs energy and propagates upstream,making the total pressure in the bladeless zone rise significantly,and the increase of the opening of the active guide vane will significantly increase the amplitude of the flow energy in the bladeless zone.