The Numerical Simulation On Welding Residual Stress And Dynamic Characteristics Of Large Fan Impeller

Fan is a kind of fluid machinery,which can convert the mechanical energy made by prime mover to pressure and kinetic energy used to gas transportation,and is widely applied.Impeller is the key component of the fan,its safety and rel iability is one of the most important factors to ensure the normal operation of the fan.When the impeller runs,it will be affected by centrifugal force and welding stress,The stress superposition has a great influence on the safety and reliability of the impeller.Therefore,it has important theoretical and engineering significance to kown the regularity of the stress and deforrmation of the impeller before its design and manufacture.In this paper,large finite element analysis software ANSYS was used to studied the safety and reliability of a welding impeller,which is based on thermal elastic-plastic finite element theory.The study including two parts,the first part mainly studies the stress and deformation of the impeller after welding and heat treatment,and discussed how the welding process?heat treatment process and blade structure effect on the residual stress and residual deformation of the impeller.The second part studied the dynamic characteristics of the impeller,the distribution of stress and deformation are cleared through the analysis of strength reliability of the impeller in operating condition.The inherent frequency and vibration mode of the impeller are calculated which can be a powerful reference data to avoid the resonance at runtime.Researches showed that the weld residual stress of the impeller is mainly concentrated in the inlet and outlet of the welds,these areas is a weak link of the impeller.After heat treatment,the peak stress concentration parts remain the same,but the stress value decreased significantly.The deformation of the impeller is less than 3mm after welding and heat treatment.And the residual stress test results match with the calculation results.On the basis of the above calculation,optimized calculation of the impeller was done,the heat treatment optimization results show that,the extension of the heat treatment time is conducive to the release of the welding residual stress,and at a certain temperature range,the higher the heat treatment temperature is,the stronger the ability to eliminate stress.The structure optimization calculation of the impeller showed that with the increase of blade cutting angle,the peak weld stress decreased.Contrastive analysis of the two kinds of welding process showed that the peak stress are reduced under the new welding process.The stress analysis of the impeller under the rated speed showed that the maximum stress concentration was in the blade of the impeller where serious distorted.The modal analysis showed that the critical speed of the impeller deviating from the rated speed under the rated speed,it won't produce resonance phenomenon,and the stiffness hardening effect have a certain influence on the resonant frequency of the impeller,it was that the natural frequencies of the impeller increases as the speed increases.