| The runner is one of the most important parts of the turbine, the loads applied the runner include the centrifugal forces, pressures of water and the alternating dynamic stresses. All of the loads and the welding residual stresses could cause the fatigue cracks in the high stress locations. These cracks greatly influence on the stability and safety of hydro turbine. It has been a problem to be solved immediately in the design and manufacture. So studying the fatigue character of runners is very necessary. SANXIA Hydraulic Generator Unit is the largest unit in the world, the stability of the runner has great influence on the operation of the units, the meaning is very important. This research mainly studies the general method of fatigue analysis for Francis runners;it bases on the theory of fatigue, and synthesizes kinds of factors affecting fatigue strength. Meanwhile, it also takes into account the results of finite element analysis and dynamic analysis for operating load universe. SANXIA runner has been calculated by this method, the fatigue life and safety factor of the runner based on design life have been obtained. The fatigue character of the runner was estimated through the results. Through this study, the fatigue strength method for Francis runners has been obtained and this method has been applied the design of runners. It provides the systematic techniques of preventing cracks and enhances the fatigue strength of runners. This method not only can be used the calculations of Francis runners but also can be used the other calculations of parts.
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