Dynamic Analysis Methods Of Large-sized Centrifugal Compressor Impeller

Impeller is the most important part of centrifugal compressor.It is not enough for the reliability design of impeller that only the centrifugal load is considered in the static analysis.The flow-solid interaction and the special dynamic behavior must be considered during the impeller analysis process.It is the key issue for the safety and reliability design of an impeller.This thesis presents the dynamic analysis methods of large-sized centrifugal compressor impeller based on CAD/CAE technique.The method of flow-solid co-calculation is referred.The application of CAE software, like SolidWorks,FLUENT and ANSYS are introduced.The adaptive mesh generation is applied in static analysis of the impeller,and the influence of the mesh size for structural analysis results is discussed.Besides the adaptive mesh,a type of part fine mesh could also get reliable results.Rotation stall and wake excitation of the enclosed impellers are studied.In order to get the structural response,harmonic response analysis is employed.Based on fatigue failure theory and IIW criterion,a fatigue analysis process is built and the structural stress is obtained. The results shows that rotation stall and wake excitation are the major factors leading to fatigue breakdown.The basic vibration characteristics of centrifugal impeller are studied.The resonance condition for the cyclic symmetric structure is discussed.The cyclosymmetric algorithm is employed in the impeller's modal analysis.The dynamic response of the impeller forced by wake excitation is computed by harmonic response analysis method.A design-oriented method for harmonic analysis of wake excitation is presented.According to this method,a harmonic analysis software written with APDL is developed.Applying the software,the structure engineers can find the dangerous working cases.This thesis provides the necessary theoretical basis for the reliability of the design of large centrifugal compressor impellers.