Analysis of Pressure Pulsation and Blade Crack Propagation for Francis Turbine
At present,the cracks or even falling off of the turbine runner blades occur from time to time,which seriously affects the safe operation of power station.In this paper,a hydropower station unit is taken as the research object,based on the fluid-structure interaction theory and the extended finite element method,the whole flow channel and runner structure of the turbine are simulated and analyzed.Moreover,the pressure pulsation information of the runner blades under different operating conditions is extracted,and the strength of the runner structure and the fatigue crack propagation of the blades are analyzed.The results show that the pressure ripple inside the runner is mainly caused by the rotation of the runner,the uneven flow field at the outlet of the guide vane and the low-frequency tail water vortex band.Under different operating conditions,the stress distribution of the blade is about the same.Meanwhile,there is a stress concentration phenomenon near the junction of the blade outlet edge,the upper crown and the lower ring.While a crack occurs at the edge of the runner near the junction of the lower ring,the crack will gradually expand from the water outlet to near the lower ring of the runner,and eventually develop into a penetrating crack.Furthermore,the number of load cycles experienced by the blade with penetrating cracks is related to the magnitude of stress and the shape of the crack.
hydraulic turbine runnerfluid-structure couplingpressure pulsationstrength analysisfatigue crack extensionfatigue life analysis
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