基于谐响应分析的冲击式水轮机转轮共振预测

Resonance Prediction of Pelton Turbine Runner based on Harmonic Response Analysis

冲击式水轮机水斗的疲劳断裂与转轮的周期性振动密切相关。以六喷嘴冲击式水轮机模型机组转轮为研究对象,采用基于模态叠加的谐响应分析法,获取转轮在实际工作载荷激励下的形变与应力响应并评估薄弱部位,结合坎贝尔图确定共振转速。结果表明,在实际运行工况下转轮三阶模态振型最易被激发,最大形变值为21.50mm,位于水斗尖端;七阶与八阶频率下被施加最大简谐载荷的水斗等效应力值较大,从根部向水斗尖端缺口处递减,最大应力值出现在分水刃根部,发生明显的应力集中;坎贝尔图显示易发生谐共振的转速为587r/min、660r/min、785r/min,在实际运行中应进一步测试与避免。

Fatigue fracture of bucket of Pelton turbine is closely related to periodic vibration of runner.Taking the runner of a six-nozzle Pelton turbine model unit as the research object,the harmonic response analysis method based on modal superposition is used to obtain the deformation and stress response of the runner under actual working load excitation and evaluate the weak parts.The resonance speed is determined by Campbell diagram.The results show that the third-order modal vibration mode of the runner is most easily excited under actual operating conditions,and the maximum deformation value is 21.50mm at the tip of the bucket.The equivalent stress value of the bucket under the maximum harmonic load at the seventh and eighth order frequencies is larger,and decreases from the root to the tip of the bucket.The maximum stressvalue appears at the root of the water separation edge,and obvious stress concentration occurs.Campbell diagram shows that the speed of resonance is 587r/min,660r/min,785r/min,which should be further tested and avoided in actual operation.