Reliability Robust Design Of Impeller Of Large Centrifugal Compressor

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 reliability of the impeller.This thesis presents researchs on structural reliability problem of large centrifugal compressor impeller under the centrifugal force based on the state-of-art mechanical strength design and reliability robust design for mechanical structures. The research work is divided into two parts, the first part is analysis of the strength of the single impeller under the centrifugal force, and get the results of the deformation and stress distribution of the impeller. Combine with the neural network technology to carry out the reliability of the impeller design with the principle to reduce costs, and also carry out the reliability robust design of the impeller with the neural network technology as well as the reliability-based sensitivity technique. The objective is making the reliability of the impeller structures insensitive to the variations of the design variables.The second part is based on the non-linear contact theory, and use the finite element method to analysis the assembly structure of the impeller when the hot charging process is end, the main is anysis the size of internal stress and the contact station of the wheel and the axis. The static contact and the dynamic contact under the centrifugal force is respective analysised. The interference closure is designed under the standerd of full contact state to make sure the impeller and the axis well assembled. In the end, the reliability and the the reliability robust design of the impeller can be obtained by combining the neural network technology and the reliability-based sensitivity technique, and the results is compared with the reliability robust design of the single impeller. Through the study of this thesis, a reliability robust design method have been summarized and explored to apply to the large-scale centrifugal compressor. The method is ensuring that the large-scale centrifugal compressor normal operatined under a high reliability and the impeller structures insensitive to the variations of the design variables. The results data of this thesis provides reference and guiding suggestion for future impeller strength design. Beneficial explorations for design of impeller structure relianbility are provided in the thesis as well.