水泵水轮机甩负荷过渡过程研究

发布时间：2018-04-10 13:56

本文选题：水泵水轮机 + 甩负荷过程　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：抽水蓄能发电机组在实际运行过程中工况转换频繁,并且往往伴随着严重的不稳定性问题。但目前对甩负荷过程瞬变流动的三维研究却相对较少。本文通过三维湍流数值模拟的方法对水泵水轮机的甩负荷过渡过程进行了研究。为了反映甩负荷过程水泵水轮机内部瞬变流动的非定常特性,在FLUENT数值模拟中通过用户自定义函数(UDF)来给定随时间变化的压力进出口边界条件,根据转子动力学角动量平衡方程结合内流场迭代计算甩负荷过程中变化的机组转速,运用动网格方法模拟甩负荷后活动导叶的动态关闭过程。按以上边界条件设置对考虑转轮间隙流动和不考虑转轮间隙流动的水泵水轮机甩负荷过程分别进行了模拟。根据不考虑转轮间隙流动的甩负荷过程数值计算结果,采用对比分析和时频联合分析(如短时傅里叶变换STFT)以及内流场分析相结合的方法分析了甩负荷过程水泵水轮机的外特性和压力脉动的动态不稳定性及其内流机理;根据考虑转轮间隙流动的甩负荷过程数值计算结果,基于熵产理论结合内流场采用对比分析的方法分析了甩负荷后水泵水轮机内的能量转换过程和损失分布及其流动机理。研究结果表明,采用三维湍流数值模拟的方法能够较为准确的模拟水泵水轮机的甩负荷过渡过程,并且在实际流场计算时应该考虑转轮与顶盖及底环之间的间隙流动的影响;甩负荷过程中水泵水轮机的外特性具有动态不稳定性,造成这种外特性动态不稳定的直接原因是水泵水轮机内剧烈的压力脉动,而造成上述外特性和压力脉动动态不稳定的根源是甩负荷后水泵水轮机无叶区和尾水管中的复杂的旋涡流动;从能量的角度讲,水泵水轮机的甩负荷过程就是一个来自水流的能量在水泵水轮机内的各种能量形式之间相互转换,最终趋于稳定的能量耗散过程。在甩负荷后的飞逸过程和进入反水泵工况之前的制动过程中,水泵水轮机内的能量损失主要分布在尾水管弯肘段和无叶区及转轮中。在甩负荷后的反水泵运行过程中上述能量损失主要分布在双列叶栅(活动导叶和固定导叶)和转轮中。造成甩负荷后水泵水轮机内能量损失的根源同样是水泵水轮机内相应位置处的旋涡流动。
[Abstract]:In the actual operation of pumped storage generator sets, the switching of working conditions is frequent, and often accompanied by serious instability problems.However, the three-dimensional research on transient flow during load rejection is relatively rare.In this paper, a three-dimensional turbulent numerical simulation method is used to study the load-rejection transition process of a pump turbine.In order to reflect the unsteady characteristics of transient flow in pump turbine during load rejection, the pressure inlet and outlet boundary conditions with time change are given by user defined function in FLUENT numerical simulation.According to the angular momentum balance equation of rotor dynamics and the iterative calculation of the internal flow field, the dynamic closing process of the guide vane after load rejection is simulated by using the dynamic grid method.According to the above boundary conditions, the load rejection process of the pump turbine considering the clearance flow of the runner and the flow without the clearance of the runner is simulated respectively.According to the numerical results of the load rejection process without considering the clearance flow of the runner,The external characteristics of pump turbine, the dynamic instability of pressure pulsation and the internal flow mechanism of pump turbine during load rejection are analyzed by means of comparative analysis and time-frequency combined analysis (such as STFTFT) and internal flow field analysis.Based on the numerical results of the load rejection process considering the clearance flow of the runner, the energy conversion process, the loss distribution and the flow mechanism of the pump turbine after load rejection are analyzed based on the entropy production theory and the internal flow field.The results show that the 3-D turbulent numerical simulation method can accurately simulate the load rejection transition process of the pump turbine, and the effect of the gap flow between the runner, the top cover and the bottom ring should be taken into account in the actual flow field calculation.In the process of load rejection, the external characteristics of the pump turbine have dynamic instability. The direct cause of this dynamic instability is the violent pressure pulsation in the pump turbine.The dynamic instability of the external characteristics and pressure pulsation is caused by the complex vortex flow in the vaneless zone and draft tube of the pump turbine after load rejection.The load rejection process of the pump turbine is a process of energy dissipation from the water flow to each other among the various energy forms in the pump turbine, and eventually tends to stabilize the energy dissipation process.During the flight escape process after load rejection and the braking process before entering the reverse pump condition, the energy loss in the pump turbine is mainly distributed in the elbow section of the draft tube, the vaneless zone and the runner.During the operation of the reverse pump after load rejection, the energy loss is mainly distributed in the double-row cascade (movable guide vane and fixed guide vane) and the runner.The source of energy loss in the pump turbine after load rejection is also the vortex flow at the corresponding position in the pump turbine.
【学位授予单位】：哈尔滨工业大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV743;TV734

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