Influence Analysis Of Blade Crack On Locomotive Turbocharger

The working environment of turbine blade of locomotive turbocharger is very harsh.The exhaust gas of high temperature and high pressure directly contact with the blade,and the turbine blade bears the combined action of centrifugal load,aerodynamic load and thermal load.Under the action of varying working conditions and loads,the blade is easy to crack,which affects the safe and stable operation of the turbocharger.Therefore,it is very significant to study the influence of blade crack on the vibration characteristics of turbocharger.Based on the theory of material mechanics and fracture mechanics,the effects of coupling stress and crack parameters on the vibration of locomotive turbine blades are studied in this paper.Firstly,four groups of typical working conditions are selected according to the data of locomotive turbocharger experimental platform.CFX is used to solve and calculate the aerodynamic load and temperature load of turbine blade,and the temperature and pressure distribution of blade surface in each working condition is obtained.Then the fluid-structure coupling analysis of the turbine was carried out to obtain the stress distribution of the turbine blade under the action of each load,and the influence of each load on the natural frequency of the turbine under different conditions was studied.Secondly,the turbine blade crack model was established by using the finite element method,and the time-varying stiffness matrix of the crack element was obtained by using the strain energy release rate method.The effects of crack location and crack depth on the vibration characteristics of turbine blades were analyzed by FRANC3 D software.The analysis results show that thermal stress reduces the natural frequency,centrifugal stress increases the natural frequency,and coupling stress ultimately reduces the natural frequency of the turbine blade.The change of crack location and depth will affect the natural frequency and resonance speed of each mode.Change the position of crack,can cause change rate is greater than the low order natural frequency of the higher order,with the increase of crack depth,can lead to maximize inherent frequency variation of modal transformation of order,the relative position of crack to greater influence on the resonance speed drop rate,crack depth changes affect the resonance point number,increases with the depth of crack,resonance point increase in the number.