Fatigue Analysis Of Impeller Of Large Centrifugal Compressors

Large centrifugal compressor is one of the important industrial equipments, which is one of the key equipments for the development of the national economy due to its high technology, complicated manufacture and wide application. The impeller is the core component which has an important influence on the reliability of centrifugal compressor performance. The study of impeller’s structural integrity and fatigue problem has important engineering application value.This paper elaborates the basic concepts of structural integrity and the fault tree analysis method to the impeller’s structural integrity and discusses the method to the impeller fatigue failure analysis.The calculation results of the impeller’s integral model’s CFD are used to obtain the blade surface’s static pressure. The impeller’s over-speeding preloading process is simulated by the software of ANSYS. The influence of the blades’hydrostatic to the impeller’s static stress is discussed and the impeller’s static stress is accurately predicted. The impeller’s vibration resonance mechanism with impeller’s wake excitation is deeply studied. Compared with the impeller’s wake excitation resonance criteria, the SAFE diagram is used to check the impeller’s resonance and point out the modes which are possible to resonance.The characteristics of impeller’s aerodynamic loads, including frequencies, amplitudes and phases, are studied by using the FFT to the unsteady CFD calculated results of integral impeller’s winter working condition. The FFT results illustrate that impeller’s aerodynamic loads’frequencies are mainly by the passing frequencies which are mainly distributed in the impeller’s inlet. But the passing frequencies loads’phase is very complex and the phases of the points which are different positions in the blade are different. The phase differences between adjacent blades to a certain value which is associated with the blades number and the guide vanes number.The thesis elaborates the impeller’s dynamic stresses calculation theories and methods and summarizes the factors affecting the impeller’s dynamic stresses. By comparing the calculated results of wake excitation simplified load model and complete load model, the influences of aerodynamic load characteristics to the dynamic stresses are studied. The impeller’s dynamic stresses are calculated with the full load model which takes account of the load amplitude distribution and load phase distribution. By combined the impeller’s static stresses and dynamic stresses, the impeller’s fatigue life is predicted on the winter working condition. Then the factors which affect the impeller’s fatigue life are analysis.