高水头混流式水轮机压力脉动特性数值研究

发布时间：2018-08-19 18:46

【摘要】：近年来,随着混流式水轮机装机尺寸与单机容量逐渐增大,水轮机的振动问题日益突出。其中活动导叶与转轮相互作用引起的压力脉动是造成水轮机运行不稳定的主要原因之一,它会诱发机械振动,使转轮叶片产生裂纹,影响机组的稳定运行。本文以Francis-99混流式模型水轮机为研究对象,对其进行全流道数值计算,并进行活动导叶与转轮间无叶区压力脉动及其传播特性探究,为水轮机的安全稳定运行提供一定的参考。研究工作主要包括了下列几部分内容:首先,对不同导叶开度的水轮机进行了数值模拟,获得水轮机运行特性参数,并与模型试验数据进行对比分析。结果表明:水轮机的效率、水头、力矩及各监测点压力均值的数值计算值与试验值吻合较好;压力脉动的数值计算结果也和模型试验结果基本上一致。其次,对3种导叶开度的水轮机进行了全流道非定常数值模拟,分析了不同工况下水轮机内部流动特点,深入研究了活动导叶与转轮间无叶区压力脉动特性。结果表明:最优工况下,活动导叶和转轮间无叶区由动静干涉效应引起的压力脉动主要以转轮叶片通过频率及其倍频为主,且压力脉动幅值远大于其他位置。无叶区压力脉动沿水轮机流道传播至整个流场,向上游和下游传播过程中,其幅值都不断减小。通过对不同工况下无叶区压力脉动进行详细分析,发现无叶区压力脉动的主要频率不受活动导叶开度的影响,但是偏离最优工况点越远,压力脉动频率成分越为复杂。最后,对同一导叶开度(小开度)不同流量下的水轮机进行数值模拟,分析转轮域的内部流场分布与压力脉动特性。结果表明:两种工况下,转轮域都有明显的叶道涡产生,水流流态较差,尤以靠近上冠处最差,偏离上冠越远,水流流态越好;随着流景的增大,转轮域的水流流态整体上得到了改善,叶道涡的范围减小,撞击现象减弱。叶片上各监测点的压力脉动主频均为28fn,为活动导叶通过频率;且叶片压力面面的门报力脉动幅值高于吸力面,转轮域中压力脉动幅值的最大值出现在叶片进口位],沿着水流流动方向,由进口至出口压力脉动幅值不断的降低;叶片压力面进口处压力脉动幅值从上冠到下环逐渐减小,但在叶片中间和出口处却不断增大。叶片吸力面压力分布规律和压力面基本上一致。
[Abstract]:In recent years, with the increasing of the size and capacity of Francis turbine, the vibration problem of turbine becomes more and more serious. The pressure pulsation caused by the interaction between the moving guide vane and the runner is one of the main reasons for the unstable operation of the turbine. It will induce mechanical vibration and make the runner blade crack and affect the stable operation of the turbine. In this paper, the full-channel numerical calculation of Francis-99 Francis turbine is carried out, and the pressure pulsation and its propagation characteristics in the vaneless zone between the active guide vane and the runner are investigated, which provides a certain reference for the safe and stable operation of the turbine. The research work mainly includes the following parts: firstly, the hydraulic turbine with different guide vane opening is numerically simulated, and the operating characteristic parameters of the turbine are obtained, and compared with the model test data. The results show that the calculated values of the efficiency, head, torque and the mean pressure of each monitoring point are in good agreement with the experimental values, and the numerical results of pressure fluctuation are basically in agreement with the model test results. Secondly, the unsteady numerical simulation of three kinds of hydraulic turbines with guide vane opening is carried out, and the characteristics of flow inside the turbine under different operating conditions are analyzed, and the pressure pulsation characteristics in the vaneless zone between the guide vane and the runner are studied in depth. The results show that the pressure pulsation caused by the static and static interference in the leafless region between the active guide blade and the runner under the optimal working condition is mainly caused by the passing frequency and the frequency doubling of the runner blade, and the amplitude of the pressure fluctuation is much larger than that of other locations. The pressure pulsation propagates along the turbine runner to the whole flow field, and the amplitude decreases continuously during the upstream and downstream propagation. Through the detailed analysis of the pressure pulsation in the leafless region under different operating conditions, it is found that the main frequency of the pressure pulsation in the leafless region is not affected by the opening of the active guide vane, but the farther away from the optimal operating condition, the more complex the pressure fluctuation frequency component is. Finally, the numerical simulation of the turbine with the same guide blade opening (small opening) and different flow rate is carried out to analyze the internal flow field distribution and pressure pulsation characteristics of the runner. The results show that under both conditions, there are obvious blade vortex in the runner domain, and the water flow pattern is worse, especially near the upper crown. The farther away from the upper crown, the better the water flow pattern, and with the increase of the flow scene, As a whole, the flow pattern in the runner domain is improved, the range of blade vortex decreases, and the impingement phenomenon is weakened. The main frequency of pressure pulsation in each monitoring point of blade is 28fn, which is the passing frequency of active guide vane, and the amplitude of gate force pulsation of blade pressure surface is higher than that of suction surface. The maximum amplitude of pressure pulsation appears in the inlet position of the blade] in the runner domain. Along the flow direction, the amplitude of pressure pulsation decreases continuously from inlet to outlet, and the amplitude of pressure pulsation decreases gradually from the top crown to the lower ring at the inlet of the blade pressure surface. But in the middle of the blade and at the outlet is increasing. The pressure distribution of the suction surface of the blade is basically the same as that of the pressure surface.
【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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