高比速混流式水轮机的水力稳定性问题

混流式水轮机的水力稳定性与机组运行工况密切相关。当水轮机在远离设计工况(最高效率点)运行时，会产生脱流和涡带，引起机组甚至相邻混凝土构件振动，并可能产生疲劳破坏。近年来，随着单机容量和水轮机尺寸的增大，有些电站因水头变幅大、负荷调节范围宽、水轮机性能不完全适应电站运行条件、制造质量存在问题和补气不利，水轮机出现不同程度的水力振动，导致转轮叶片裂纹，尾水管壁撕裂，有的甚至引起厂房或相邻水工建筑物发生共振，危及电站安全运行。本文对混流式(特别是高比速混流式)水轮机的水力稳定性问题进行了初步分析和讨论。

Hydraulic Instability Problem on the High Specific Speed Francis Turbine

The hydraulic instability of Francis turbine has a direct bearing on the operation point. While the turbine runs far from the design point (the maximum efficiency point), the separate flow and vortex will be produced and cause the vibration of units and adjacent concrete structure. It may lead to the fatigue damage of equipments. Along with the increase on the unit capacity and the dimension, due to the large head variation and adjusting load range, and the poor manufacture quality and ineffective air admission, the turbine can not suitable the condition of operation at these power stations and cause the hydraulic vibration to some extent. As a reasult, the cracks in the blades and the draft tube as well as the resonance together with the powerhouse or the adjacent buildings will be caused. The primary analysis and discussion has been carried on the hydraulic instability problems for Francis turbines (especially for the high specific speed turbines) in this paper.