部分负荷下混流式水轮机转轮叶片变形对流场的影响

将CFD流动分析软件与结构刚强度软件有机结合,对混流式转轮在不同工况下的流动进行分析。通过程序将流场参数加载到结构分析软件上,对变形后的叶片再次进行网格划分流场计算,并计算出混流式转轮叶片上的应力和变形,详细分析了转轮变形后的流场,达到了真正意义上的流固耦合。研究结果表明:最大应力发生在转轮叶片的出水边与上冠的连接处,应力集中较明显,易于发生疲劳破坏。产生最大变形的部位是转轮叶片的出水边与下环的连接处,且从上冠到下环变形量逐渐增大,即此部位就是叶片振动的敏感区域;转轮变形后对水轮机内部流场的影响表现在叶片进口边头部压力增大,叶片出口边靠下环处流速增大、压力下降,空化性能降低。变形后的流场使得尾水管内部的涡带产生、紊动加剧,说明叶片变形后对水轮机内部流场的影响是引起水轮机裂纹和振动的真正原因。

INFLUENCE OF RUNNER BLADE DEFORMATION ON FLUID FIELD OF FRANCIS TURBINE UNDER PART LOAD

Combined CFD flow analysis, stiffness and strength software, the flow is analyzed under different operation condition of Francis turbine. Through the program parameters are transferred to the structure analysis software, then for the deformed blade the grid is partitioned and the flow field is computed, and the stress and strain of blade of Francis turbine are obtained, finally the Fluid field distribution under deformed turbine blade is analyzed in detail, which reaches the actual Fluid-solid coupling. The research result shows that the maximal stress occurs at the joint of outlet of blade and crown, where stress concentrates seriously, and the tired destroy is prone to occur. The most deformation occurs at the joint of outlet of blade and band, the deformation increases gradually from crown to band, which is the sensitivity area of vibration. The influence of deformed blade on inter flow field represents that the press increases at the head of inlet of blade, the flow velocity increases and press decreases at the outlet of blade near band, then the cavitation performance is fallen. The deformed blade causes the vortex in the draft tube, turbulence severity, which explains that the influence of deformed blade on inter flow field is the real reason of causing crack and vibration of turbine.