Influence of the clearance flow on the load rejection process in a pump-turbine
Influence of the clearance flow on the load rejection process in a pump-turbine
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DOI：
10.1016/j.renene.2018.04.054
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发表时间：
2018-11
期刊：
影响因子：
8.7
通讯作者：
Xiaolong Fu;Deyou Li;Hongjie Wang;Guanghui Zhang;Zhenggui Li;Xianzhu Wei
中科院分区：
文献类型：
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作者：
Xiaolong Fu;Deyou Li;Hongjie Wang;Guanghui Zhang;Zhenggui Li;Xianzhu Wei
转轮与静止件之间的间隙流极大地影响水泵水轮机的效率和水推力。特别是在甩负荷过程中，转轮的间隙流量对于准确预测转轮上的液压扭矩和转速的变化更为重要。然而，在大多数先前的研究中，间隙流通常被忽略。为了研究间隙流动对甩载荷过程模拟的影响，本文在考虑和不考虑转轮间隙流动的情况下进行了三维模拟。为了模拟边界条件的瞬态特性，使用用户定义的函数确定了螺旋套管入口和尾水管出口处的非定常总压和静压边界条件。采用刚体运动与水泵水轮机内水流耦合的方法来预测转速的变化。采用动态网格技术模拟导叶的动态关闭过程。根据已有的实验数据，对考虑和不考虑转轮间隙流动的数值模拟结果进行了比较和分析。结果表明，甩负荷瞬态过程中转轮与静止件之间的间隙流对水泵水轮机脉动性能特性和非定常涡流的准确模拟有显着影响。而且越接近小流量工况，间隙流量的影响越严重。因此，在模拟甩负荷暂态过程时，应考虑间隙流对水泵水轮机非定常主流的分流和冲击作用。
The clearance flow between the runner and the stationary parts greatly effects the efficiency and the hydraulic thrust of pump-turbines. Especially in the load rejection process, the clearance flow of the runner is more important to accurately predict the hydraulic torque on the runner and the variation of the rotational speed. However, the clearance flow was generally neglected in the most previous studies. To investigate the influence of the clearance flow on the simulation of load rejection process, three dimensional simulations were carried out in this paper with and without considering the clearance flow of the runner. To simulate transient characteristic of the boundary conditions, the unsteady total pressure and static pressure boundary conditions were determined at the spiral casing inlet and draft tube outlet using the user defined function. The method of coupling the rigid body motion with the water flow in the pump-turbine was adopted to predict the variation of the rotational speed. Dynamic mesh technology was used to simulate the dynamic closing process of the guide vanes. Based on the available experimental data, the numerical simulation results with and without considering the clearance flow of the runner were compared and analyzed. The results indicate that the accurate simulations of the fluctuating performance characteristics and the unsteady vortex flows in the pump-turbine are significantly influenced by the clearance flow between the runner and the stationary parts during the load rejection transient process. Moreover, the closer to the small discharge conditions, the influence of the clearance flow is more severe. Therefore, the shunt and impact action of the clearance flow to unsteady main flow in pump-turbines should be considered during the simulation of the load rejection transient process.