长短叶片转轮对低比速混流式机组的性能改善研究

基于计算流体动力学分析理论,对含有常规转轮和长短叶片转轮的混流式水轮机开展全流道数值分析,研究高水头下低比转速混流式水轮机转轮在不同工况下的流动现象,探明转轮加装短叶片对混流式水轮机内部流动状态的影响。在最优工况下,通过对比计算所得的两种转轮内部的流速和压力分布发现:加装短叶片以后转轮叶片吸力面进口附近的涡流得到明显抑制,长叶片的压力负荷得到减弱;增加短叶片后,转轮出口环量减小较为明显,对尾水管流态改善、转轮及机组的能量特性提高有重要作用。研究结果表明,在相同的单位参数下,相比常规叶片转轮,长短叶片转轮改善了转轮进口的入流条件,从而提升了机组的运行稳定性和能量特性,可作为高水头转轮设计的主要方向。

Performance improvement analysis of a low-specific speed Francis turbine runner with splitter blades

Based on the theory of CFD analysis，through conducting full passage numerical analysis on the conventional runner and runner with splitter blades of francis turbine，internal flow phenomena of the high head and low specific speed francis turbine under different conditions are investigated in this paper，especially the flow phenomena of the runner，aiming at verifying how the internal flow state of francis turbine operating under high head conditions will differ between with and without splitter blades. Through calculation，internal flow velocity and pressure distribution of runner blades under different flow discharge in the same unit speed are obtained，it is found that after adding splitter blades，inlet vortex on suction surface of the long blade runner is inhibited obviously，and pressure load of the long blade is reduced. After adding splitter blades，outlet circulation of the runner has an obvious reduction，which plays an important role in improving flow state of draft tube and energy characteristics of the runner and unit. It can be concluded from research results in this paper that under the same unit parameters，compared with conventional runner，the splitter blade runner not only improves the inflow condition of the runner，but also improves the operation stability and energy characteristics of the unit，thus it can be used as the main direction in design of the high head runner.