Fatigue Analysis Of Weld Impeller Of Centrifugal Compressors

Impellers are core components of high-speed rotors of centrifugal compressors which make the airflow accelerated, pressurized and heated. The structure, service status and working environment of the impeller are very complicated due to cyclic loadings of centrifugal force, aerodynamic force, external excitation and impact as well as dynamic forces. Those loads superposed with welding residual stresses can cause fatigue cracks in locations of high stress. The reliability of the impeller directly affects the normal operation and even the safety of the whole compressor unit. Therefore, it is urgent to pursue the research on analysis of the fatigue property of the impeller.This thesis presents researches on fatigue problem of large-scale compressor impellers based on the state-of-the-art fatigue analysis for mechanical structures. Starting with the basic theory of fatigue, various factors affecting the fatigue strength are taken into account according to the actual operation condition of the impeller. The hotspot stress method is used to analyze the fatigue strength of the impeller. The fatigue life is obtained and the fatigue property is evaluated in combination with the finite element analysis and the test data of fatigue property. Further, the infrared thermal imaging technology is used to get the fatigue strength of the material. The two kinds of test results are compared. A shape optimization of the impeller is used to improve the fatigue property after the analysis. The present method enables the fatigue strength analysis for large-scale centrifugal compressor impellers, and has been applied to the practical design. This ensures the safe, reliable and long-term steady operation of the Ethylene Device of One-Million-Ton Production Per Year and devices alike. It also provides reference and guiding suggestion for future impeller strength design. Beneficial exploration for structure fatigue test techniques are provided in the thesis as well.