轮缘间隙对贯流式水轮机转轮内部流动特性研究

以柴家峡电站原型机为研究对象,采用数值计算对水轮机转轮区域空化现象进行了系统的研究。通过改变轮缘间隙的距离,对灯泡贯流式水轮机不同轮缘间隙时的空化现象进行模拟,比较了不同间隙值转轮空化的发生状态,分析了轮缘间隙值变化对水轮机转轮空化性能及流场压力脉动的影响。结果表明:转轮内空化区域主要发生在叶片背面轮缘靠近出水边处和叶片背面轮毂间隙处,间隙值增大使轮缘处间隙空化发生剧烈。这是由于叶片与转轮室之间的位置存在间隙泄漏流动所引起的,此位置流体受到转轮主流的排挤作用并且在二次流和回流的共同作用下,间隙泄漏流动容易形成漩涡,从而致使此处的压力降低;叶片压力脉动呈现出周期性的变化,轮缘处对压力脉动所引起的振动敏感性大于叶片中部和轮毂处,当间隙值远离设计值时,压力幅值变化剧烈。

Research on the Flow Characteristics of the Turbine Runner by Flange Clearance

The prototype of the Chaijiaxia Power Station as the research object,numerical simulation is carried out to systematically research the phenomenon of cavitation in the turbine runner.By changing the distance of the tip gap,the cavitation phenomenon of different flange clearances of bulb tubular turbines is simulated,by comparing the occurrence of cavitation with different gaps,the effect of flange clearance value on the cavitation performance of the turbine runner and the pressure fluctuation of the flow field are analyzed.The results show that the cavitation in the runner mainly occurs at the suction side of blade near the outlet edge and the hub clearance,increased clearance value causes intense cavitation at the blade edge due to the leakage flow of the position between the blade and the wheel chamber,the fluid is repulsed by the main flow of the runner and combined with the secondary flow and back flow,gap leakage flow can easily form vortex,which causes the pressure here to decrease.The blade pressure fluctuation shows periodic changes,and the vibration sensitivity caused by the pressure fluctuation of the blade is more than that at the middle of the blade and at the hub,the gap value is far from the design value,the pressure amplitude changes more drastically.