Abstract
In this work, the estimation of crack initiation life of a hydraulic Francis turbine runner is presented. The life prediction is based on the local strain approach to predict the initiation life. First, the analysis is carried out in air and in water condition and the runner’s natural frequencies were calculated using the finite element (FE) method. The analysis in air is compared with experimental analysis in order to have a representative model of real runner and subsequently the numerical analysis was perform in water. In the case of the runner immersed in water, the added mass effect due to the fluid structure interaction (FSI) is considered. Second, the static and dynamic stresses were calculated according to life estimation. For the calculation of static stresses, the pressure distribution of water and the centrifugal forces were applied to the runner. The dynamic stresses were estimated for interactions between the guide vane and the runner. Lastly, the estimation of the crack initiation life of the runner was obtained.
Highlights
The tendency of higher power concentration in hydraulic turbines, bring as a consequence an increase in both the load and hydraulic forces in the machine
In the most of hydroelectric power plants around the World, turbines have operated for decades and in many of them, the current operating conditions are different from the original design specified, these operations cause vibrations and some have presented cracks in the runners produced by fatigue [1,2]
These concepts are used in this work, and the following procedure is adopted for the estimation of crack initiation growth life of a Hydraulic Francis Turbine Runner that is installed in a Mexican hydroelectric power plant
Summary
The tendency of higher power concentration in hydraulic turbines, bring as a consequence an increase in both the load and hydraulic forces in the machine. These conditions produce major stresses in runners and possible vibration problems that could cause fatigue and fracture the blades. The concept of local strains and stresses are the most promising approach to predict the crack initiation growth in a structure subjected to fatigue loads [4] These concepts are used in this work, and the following procedure is adopted for the estimation of crack initiation growth life of a Hydraulic Francis Turbine Runner that is installed in a Mexican hydroelectric power plant
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