水泵水轮机流场脉动与熵产率的关系

为了研究水泵水轮机不同工况下的运行稳定性,采用FLUENT软件对模型水泵水轮机转轮和无叶区的流态、熵产率分布、压力脉动进行了数值模拟,并将数值模拟结果与试验进行了对比.结果表明:数值计算的压力脉动数据与试验值吻合较好,旋涡引起的速度梯度和压力梯度剧烈变化是水泵水轮机内部高能量损失的根本原因.相较于设计工况,小流量工况时转轮叶片吸力面水流的流动分离和旋转失速会导致此处熵产率较高,叶片吸力面压力脉动主频和第2主频幅值最大;大流量工况时动静干涉作用占主导,无叶区的熵产率最大,相应的无叶区压力脉动主频幅值也最大.可见各工况下主流区熵产率和压力脉动具有强相关性,熵产率大的区域,压力脉动也较大.

Relationship between flow pulsation and entropy production rate of pump turbine

In order to study the operation stability of pump turbine under different working conditions, the flow pattern, entropy production rate distribution and pressure pulsation of model pump turbine runner and vaneless area were numerically simulated by FLUENT software, and the numerical simulation results were compared with the test. The results show that the pressure pulsation data of numerical calculation are in good agreement with the experimental values, and the drastic changes of velocity gradient and pressure gradient caused by vortex are the root cause of high energy loss in pump turbine. Compared with the design condition, the flow separation and rotating stall of the flow on the suction surface of the runner blade under small flow condition will lead to higher entropy production rate, and the amplitudes of the main frequency and the second main frequency of the pressure pulsation on the suction surface of the blade are the largest. Under the condition of large flow, the dynamic and static interference is dominant, the entropy production rate in the vaneless region is the largest, and the main frequency amplitude of pressure pulsation in the corresponding vaneless region is also the largest. It can be seen that there is a strong correlation between entropy production rate and pressure pulsation in the main flow area under various working conditions. In the area with large entropy production rate, the pressure pulsation is also large.