贯流式水电站过渡过程及其水位波动规律研究

发布时间：2018-12-17 10:10

【摘要】：随着我国水电资源开发的深入,贯流式低水头电站越来越多。一般低水头电站具有库容小、明渠河道径流式的特点。水电机组经常在电力系统中承担调频调峰、以及汛期防洪泄水等任务。当贯流式机组工况发生较大变化时,机组流量相应发生变化,会在上游及下游河道中形成较大水位波动。这样一来,不仅会影响机组出力的稳定性,还会对水电站水工建筑物以及航运安全造成不利影响。因此,本文针对这一问题,通过分析计算贯流式水轮发电机组甩负荷过渡过程,研究水电站上下游水位波动规律。本文首先建立了明渠河道、过水管道、以及水轮发电机组各部分数学模型;然后,根据明渠和管道中的水流流动特性,选取不同时间步长分别给出明渠非恒定流和压力管道非恒定流的特征线法计算模型。其次,构建了“引水明渠+压力管道+机组+压力管道+尾水明渠”水力系统计算模型,将水轮机模型静态全特性曲线用正交网格离散后存储于三维数组中,采用MATLAB语言编写过渡过程计算程序。最后分别计算了不同明渠河道长度与断面面积、不同导叶与桨叶关闭时间情况下,贯流式机组甩负荷过渡过程中的上下游明渠河道水位波动变化曲线。计算结果表明,贯流式机组管道进口压力在甩负荷初始时刻会出现负水击现象;明渠面积越小,明渠的水位波动幅度越大;明渠长度越长,明渠的水位波动周期越大;在相同导叶关闭时间情况下,桨叶关闭时间越长,转速上升率越小,明渠水位波动越小。特别在桨叶不动作时,转速上升率、明渠水位波动、轴向反推力及水轮机进口压力波动明显降低。
[Abstract]:With the development of hydropower resources in China, there are more and more low-head tubular hydropower stations. Generally, low-head hydropower stations have the characteristics of small storage capacity and open channel runoff. Hydropower units often undertake the tasks of frequency modulation and peak regulation, flood control and discharge in flood season. When the operating condition of the tubular unit changes greatly, the unit discharge will change accordingly, which will form a large water level fluctuation in the upstream and downstream river channels. In this way, it will not only affect the stability of generating units, but also adversely affect hydraulic structures and shipping safety of hydropower stations. Therefore, in order to solve this problem, this paper analyzes and calculates the transient process of load rejection of tubular turbine generator sets, and studies the fluctuation law of water level in upstream and downstream of hydropower stations. In this paper, the mathematical models of open channel, water pipeline and hydro-generator unit are established. Then, according to the flow characteristics of open channel and pipeline, different time steps are selected to calculate the unsteady flow in the open channel and the unsteady flow in the pressure pipeline by the characteristic line method, respectively. Secondly, the hydraulic system calculation model of "open channel of pressure pipeline unit in open channel" is constructed, and the static full characteristic curve of turbine model is discretized by orthogonal grid and stored in three dimensional array. MATLAB language is used to program the calculation program of transition process. Finally, the variation curves of water level fluctuation in the upstream and downstream open channel during load rejection transition of tubular units are calculated under the conditions of different open channel length and section area, different guide vane and blade closing time. The calculation results show that the inlet pressure of tubular unit will appear negative water hammer phenomenon at the initial time of load rejection, the smaller the open channel area, the greater the fluctuation amplitude of open channel water level, the longer the length of open channel, the greater the period of open channel water level fluctuation. Under the same guide vane closing time, the longer the blade closing time, the smaller the speed rise rate and the smaller the open channel water level fluctuation. Especially when the blade is not moving, the speed rise rate, the open channel water level fluctuation, the axial reverse thrust and the turbine inlet pressure fluctuation are obviously reduced.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV734

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