水泵水轮机飞逸与制动工况内流特性及转轮受力分析
发布时间：2018-12-15 02:35
【摘要】：可逆式水泵水轮机组兼具了发电及储能的特点,对调整电网负荷起重大作用,尤其对于西北地区新能源大发展中的储能与改善能源配送结构意义重大。水泵水轮机在运行过程中经常会经历启动、停机、甩负荷、飞逸等一系列过渡过程,其中尤以飞逸过渡过程可能引起的破坏性为重。而现今对飞逸及退出飞逸过程中所经历制动工况的研究还不够深入。因此,通过试验数据和数值模拟计算,探讨研究水泵水轮机飞逸及制动工况的流动机理及转轮受力,对改善机组运行的稳定性意义重大。本文以混流式模型水泵水轮机为研究对象,通过数值模拟与试验结合的方式研究其飞逸工况以及退出飞逸时经历的制动工况,主要研究内容如下:1、利用FLUENT软件对混流式水泵水轮机模型7个不同开度下的飞逸工况以及小开度11 mm下全特性曲线上包含水轮机、制动、反水泵的7个工况进行全流道数值模拟,分析并作出单位流量Q11与单位转速n11关系曲线,通过与试验所得曲线的对比,确认数值计算对这两个工况模拟结果的误差度在允许范围内,可以用于分析。2、对不同开度下飞逸工况时的全流道内流形态、压力脉动及转轮受力作出分析,分析开度对飞逸工况的影响。3、选取较小导叶开度11 mm,对其制动工况进行重点探究,着重分析导叶区的尾迹与压力脉动以及转轮和叶片的受力。通过以上分析研究,得出如下结论:1、在不同开度下水泵水轮机进入飞逸工况:(1)随着开度增大到一定值,蜗壳内流动特性显著改变,压力波动程度增大,出现高频脉动成分;转轮进口冲击损失使得内部高低压分布的对称性被破坏,叶片工作面、背面差值增大。(2)随着开度的增大,转轮内流体速度增加,压力增大;转轮所受径向力、轴向力的大小与波动幅度随开度的增大而显著增加,叶片承受的压力载荷也普遍增加,流道内各监测点的压力均有不同程度的升高。2、退出飞逸的过渡过程即制动工况下:(1)导叶区充斥着结构大小不一的漩涡,涡系结构的演变及水流冲击效应造成能量的损失,进一步转化为紊动能,其处压力脉动主频为叶频,幅值达到正常运行工况的3倍以上。(2)制动工况下转轮所受径向力呈周期性脉动,受力方向向一边倾斜,在飞逸线附近正斜率的制动区域运行时内部会出现旋转失速现象,在转轮出口引发周期性横流,对叶片正、背面产生周期性冲击,叶片将承受较大的交变应力。
[Abstract]:The reversible pump turbine unit has the characteristics of power generation and energy storage, which plays an important role in adjusting the load of power grid, especially for energy storage and improvement of energy distribution structure in the development of new energy sources in Northwest China. A series of transition processes, such as start-up, shutdown, load rejection, flight escape and so on, are often experienced during the operation of the pump turbine, especially the damage caused by the flight escape transition process. However, the research on braking condition in flight escape and exit flight escape is not deep enough. Therefore, by means of experimental data and numerical simulation, it is of great significance to study the flow mechanism of the runaway and braking conditions of the pump turbine and the force acting on the runner, which is of great significance to improve the stability of the unit. This paper takes the Francis model pump turbine as the research object, through the numerical simulation and the test way to study its flight escape condition and the exit flight escape experience braking condition, the main research contents are as follows: 1. Using FLUENT software, the full flow channel numerical simulation is carried out on the full characteristic curves of the Francis pump turbine model under 7 different opening conditions and the low opening of 11 mm, including the turbine, brake and reverse pump. The relationship curve between unit flow rate Q11 and unit rotational speed n11 is analyzed and made. By comparing with the curve obtained from the test, it is confirmed that the error degree of numerical calculation for the simulation results of these two conditions is within the allowable range and can be used for analysis. The flow pattern, pressure pulsation and the force on the runner are analyzed under different opening conditions, and the influence of opening degree on flight escape condition is analyzed. 3. The braking condition is mainly studied by selecting a smaller guide blade opening of 11 mm,. The wake and pressure pulsation in the guide vane region and the stress on the runner and blade are analyzed. Through the above analysis and research, the following conclusions are drawn: 1. Under different opening degrees, the pump turbine enters the flight escape condition: (1) with the opening increasing to a certain value, the flow characteristics in the volute significantly change, and the pressure fluctuation degree increases. High frequency pulsation; The impingement loss at the inlet of the runner causes the symmetry of the internal distribution of high and low pressure to be destroyed, and the difference on the back side of the blade face increases. (2) with the increase of opening, the fluid velocity and pressure in the runner increase; The radial force, the axial force and the fluctuation amplitude of the runner increased significantly with the increase of opening, and the pressure load on the blade increased generally, and the pressure at the monitoring points in the runner increased in varying degrees. 2. In the transient process of exit from flight, that is, under braking conditions: (1) the guide vane region is filled with swirls of different sizes, and the energy loss caused by the evolution of vortex structure and the impact effect of water flow is further transformed into turbulent energy. The main frequency of pressure pulsation is blade frequency, and the amplitude is more than 3 times of the normal operating condition. (2) under braking condition, the radial force of the runner fluctuates periodically, and the direction of the force is inclined to one side. In the braking area with positive slope near the flight escape line, the phenomenon of rotating stall will occur inside, and the periodic transverse flow will occur at the outlet of the runner, which will have a periodic impact on the positive and back of the blade, and the blade will bear larger alternating stress.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV136
[Abstract]:The reversible pump turbine unit has the characteristics of power generation and energy storage, which plays an important role in adjusting the load of power grid, especially for energy storage and improvement of energy distribution structure in the development of new energy sources in Northwest China. A series of transition processes, such as start-up, shutdown, load rejection, flight escape and so on, are often experienced during the operation of the pump turbine, especially the damage caused by the flight escape transition process. However, the research on braking condition in flight escape and exit flight escape is not deep enough. Therefore, by means of experimental data and numerical simulation, it is of great significance to study the flow mechanism of the runaway and braking conditions of the pump turbine and the force acting on the runner, which is of great significance to improve the stability of the unit. This paper takes the Francis model pump turbine as the research object, through the numerical simulation and the test way to study its flight escape condition and the exit flight escape experience braking condition, the main research contents are as follows: 1. Using FLUENT software, the full flow channel numerical simulation is carried out on the full characteristic curves of the Francis pump turbine model under 7 different opening conditions and the low opening of 11 mm, including the turbine, brake and reverse pump. The relationship curve between unit flow rate Q11 and unit rotational speed n11 is analyzed and made. By comparing with the curve obtained from the test, it is confirmed that the error degree of numerical calculation for the simulation results of these two conditions is within the allowable range and can be used for analysis. The flow pattern, pressure pulsation and the force on the runner are analyzed under different opening conditions, and the influence of opening degree on flight escape condition is analyzed. 3. The braking condition is mainly studied by selecting a smaller guide blade opening of 11 mm,. The wake and pressure pulsation in the guide vane region and the stress on the runner and blade are analyzed. Through the above analysis and research, the following conclusions are drawn: 1. Under different opening degrees, the pump turbine enters the flight escape condition: (1) with the opening increasing to a certain value, the flow characteristics in the volute significantly change, and the pressure fluctuation degree increases. High frequency pulsation; The impingement loss at the inlet of the runner causes the symmetry of the internal distribution of high and low pressure to be destroyed, and the difference on the back side of the blade face increases. (2) with the increase of opening, the fluid velocity and pressure in the runner increase; The radial force, the axial force and the fluctuation amplitude of the runner increased significantly with the increase of opening, and the pressure load on the blade increased generally, and the pressure at the monitoring points in the runner increased in varying degrees. 2. In the transient process of exit from flight, that is, under braking conditions: (1) the guide vane region is filled with swirls of different sizes, and the energy loss caused by the evolution of vortex structure and the impact effect of water flow is further transformed into turbulent energy. The main frequency of pressure pulsation is blade frequency, and the amplitude is more than 3 times of the normal operating condition. (2) under braking condition, the radial force of the runner fluctuates periodically, and the direction of the force is inclined to one side. In the braking area with positive slope near the flight escape line, the phenomenon of rotating stall will occur inside, and the periodic transverse flow will occur at the outlet of the runner, which will have a periodic impact on the positive and back of the blade, and the blade will bear larger alternating stress.
【学位授予单位】：兰州理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV136
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