Reliablity Anasysis Of The Second Stage Turbine Blade In A APU

The second stage turbine blade is one of the typical hot end components in the APU power section.It works in high temperature,high pressure,and high-speed centrifugal environments.It is inevitable that the blade will be failed and damaged.Therefore,it is necessary to study the damage,fatigue and reliability of the second stage turbine blade in APU.Based on APU repair report,the data of the damage blade are counted,the main damage patterns of the blade are analyzed.The damage mechanism of the blade is studied.Based on the blade damage data,two-parameter Weibull distribution model is selected to establish distribution model.On the basis of linearization of the distribution function,the least squares method is used to fit the fault data with MATLAB programming.The related parameters are solved.The K-S test method is used to perform the fitting optimization test.The relevant functions are drawn.Four reliability indicators are calculated.The three-dimensional model of the APU second stage turbine assembly is established by using CATIA.The blade finite element is established by using ANSYS Workbench.Blade flow field is simulated by using CFX.CFX temperature field and pressure field are loaded on the corresponding module,and the blade temperature distribution and aerodynamic distribution are simulated and studied.Loading speed simulates blade centrifugal force.Under the joint action of three kinds of loads,a blade flow-thermal-solid coupling model is established to simulate and study the equivalent stress and equivalent strain.The Manson-Coffin model is used to calculate the fatigue life of the blade in the "start-constant-start" state based on finite element simulation.It is compared with Fatigue Tool simulation in ANSYS Workbench.Based on the current service APU,the blade damage is calculated by using the Miner damage theory,and the total number of flight hours is predicted,which contrasted with the average life.The equivalent load and strength distribution are calculated.The reliability of the blade is calculated based on the stress-strength interference model.