1000MW混流式水轮机压力脉动分析

发布时间：2018-06-01 15:38

本文选题：混流式水轮机 + 压力脉动　；参考：《哈尔滨工业大学》2017年硕士论文

【摘要】：随着能源工业的发展,随着工艺技术的日趋成熟,中国水电工业已进入电网峰值高、机组装机容量大、集成网络化管理的蓬勃发展时期。目前在建的白鹤滩电站建成后,单机容量将超过百万千瓦,总装机容量将位列三峡电站之后,成为国内第二大水电站。受运行条件的限制及电网实际需求的不同,混流式水轮机经常要在偏离设计工况下运行,由此引起的运行不稳定问题一直是行业研究的重点课题。作为考核水轮机稳定性的重要衡量标准,压力脉动性能也就成为研究的重点。本课题正是基于白鹤滩电站的模型混流式水轮机,利用数值模拟的手段,对不同单位转速,不同开度的工况进行非定常数值模拟,详细分析内部流动机理,得到压力脉动的特性及其在全流道内的传播规律,并得到转速及开度的变化对压力脉动的具体影响,主要研究内容如下:(1)在同一开度(a_0=8.47mm)不同单位转速下,针对不同工况点进行非定常计算,找出各流域内压力脉动的主频、次频、二次频等,对各频率相关性进行分析,研究各流域内压力脉动特性及沿流向的传播规律,并对比各工况得出转轮转速对压力脉动幅值及频率的影响规律;(2)在同一单位转速(n_(11)=5 8.8 r/min)下,改变活动导叶开度,针对不同工况点进行非定常数值模拟,得出各流域压力脉动特性,并得到压力脉动沿全流道进行传播的变化规律,探究导叶开度对压力脉动峰值及主要频率的影响规律,结合计算得到的速度场、压力场及涡量场,分析各流域内的压力脉动源的产生机理。(3)在变流量工况下,得到各流域内压力脉动连续变化趋势,结合所得到流场分析该工况下的流动状态,并与定流量工况进行比较,分析压力脉动特性的异同。本文的研究结果表明,压力脉动主要频率受导叶开度及转轮转速的影响,在全流道内既向上游传播又向下游传播,并沿途衰减或增加。小开度时,随转速增加,压力脉动幅值整体增加。在小开度下,低转速及高转速时表现为尾水涡带的低频压力脉动,中转速下表现为无叶区转轮叶片通过频率。而在大开度下,压力脉动的幅值整体减小,这表明开度减小,压力脉动特性逐渐明显,脉动程度更剧烈。在变流量下,流量的持续增加使全流道内压力脉动的振幅发生巨大改变,显著高于同开度同转速下的定流量工况。
[Abstract]:With the development of energy industry and the maturation of technology, Chinese hydropower industry has entered the vigorous development period of high peak value of power grid, large installed capacity of unit and integrated network management. After the construction of Baihetan Hydropower Station currently under construction, the single unit capacity will exceed one million kilowatts, and the total installed capacity will rank behind the three Gorges Power Station and become the second largest hydropower station in China. Due to the limitation of operation conditions and the difference of actual demand of power grid, Francis turbine often has to operate in deviation from the design condition. The operation instability caused by this problem has always been a key topic in industry research. As an important measure of turbine stability, pressure pulsation performance has become the focus of research. This subject is based on the model Francis turbine of Baihetan Hydropower Station. By means of numerical simulation, the unsteady numerical simulation of different unit rotational speed and different opening is carried out, and the internal flow mechanism is analyzed in detail. The characteristics of pressure pulsation and its propagation in the whole channel are obtained, and the specific effects of the changes of rotational speed and opening degree on the pressure fluctuation are obtained. The main research contents are as follows: 1) at the same opening degree, 0 / 0 / 8.47mm / unit rotating speed. According to the unsteady calculation of different working conditions, the main frequency, secondary frequency and secondary frequency of pressure pulsation in each watershed are found out. The correlation of each frequency is analyzed, and the characteristics of pressure pulsation and the propagation law along the flow direction are studied. The influence of runner speed on the amplitude and frequency of pressure pulsation is obtained by comparing the different working conditions. The unsteady numerical simulation is carried out at different operating conditions by changing the opening of the active guide vane under the same unit rotational speed (n / v) and 58.8 r / min. The characteristics of pressure pulsation in each basin are obtained, and the variation law of pressure pulsation propagating along the whole channel is obtained. The influence of guide vane opening on the peak value and main frequency of pressure pulsation is explored, and the velocity field, pressure field and vorticity field obtained by calculation are combined with the calculated velocity field, pressure field and vorticity field. The generation mechanism of pressure pulsation source in each watershed is analyzed. Under variable flow condition, the continuous variation trend of pressure pulsation in each watershed is obtained. The flow state under this condition is analyzed in combination with the obtained flow field, and compared with the constant flow condition. The characteristics of pressure fluctuation are analyzed. The results show that the main frequency of the pressure pulsation is affected by the speed of the guide vane and the rotating speed of the runner, which propagates both upstream and downstream in the whole channel, and attenuates or increases along the way. When the opening is small, the amplitude of pressure pulsation increases with the increase of rotational speed. At low speed and high speed, the low frequency pressure pulsation of tail water vortex band is observed at low opening and the passing frequency of impeller blade at middle speed. However, the amplitude of the pressure pulsation decreases at large opening, which indicates that the opening decreases, the pressure fluctuation becomes more obvious and the pulsation becomes more intense. Under the condition of variable flow rate, the amplitude of pressure pulsation in the whole channel is greatly changed with the continuous increase of flow rate, which is significantly higher than the constant flow condition with the same opening degree and the same speed.
【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】：TV734.1

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