| Impeller as the most core components of the centrifugal compressor,its fatigue strength and service life directly determines the overall safety of the compressor.Shenyang an enterprise centrifugal compressor under normal operating conditions,rated life,the impeller fatigue damage,the accident caused certain economic losses.In order to ensure that the compressor can operate safely and reliably,according to the actual situation,the fatigue strength calculation method of the impeller is amended,and the corrected calculated value is analyzed for reliability verification.The main research contents are as follows:(1)Among the many factors that determine the fatigue strength of the impeller,stress concentration,surface processing and dimensions are selected as the main influencing factors according to the degree of importance and feasibility of the study.The mutual influence coefficients of the three factors are studied,and the fatigue integrated correction coefficient is proposed based on the existing theory.By comparing with the existing theory,it is proved that the fatigue integrated correction coefficient has the least sensitivity to the three factors,indicating the best stability subject to the change of parameters,and thus the calculation result error in the subsequent impeller fatigue strength is also the least,which provides the theoretical basis for the subsequent calculation.(2)The impeller dynamics is analyzed to find out the minimum location of the impeller fatigue strength(the location where fatigue damage occurs in the impeller),and the fatigue strength is calculated.In order to ensure the real simulation of the actual stress condition of the impeller,the mesh division of the impeller is verified to be irrelevant;subsequently,the modal of the impeller is compared with and without pre-stress,and the modal analysis shows that the inherent frequency of the impeller resonance is reduced by the action of the coupling load,setting The impeller speed under different working conditions is set,and the possible resonant frequency point of the impeller is found out by Campbell diagram for resonance verification.After the fatigue damage caused by resonance is excluded through the verification,the harmonic response analysis of the impeller is carried out to find out the sensitive frequency at which the maximum displacement deformation of the two impellers occurs according to the different structural reasons of the impeller,and the stress value at the sensitive frequency is derived to provide data for the subsequent fatigue strength correction and reliability analysis.(3)Based on the commonly used S-N reliability calculation theory,the P-S-N reliability calculation curves and confidence intervals of the three stress-life models are fitted,and the threeparameter model is selected for fatigue strength reliability analysis through data comparison,and the stress values at the sensitive frequency above are corrected for calculation;a control group is set up to compare the stress values of 90% and 50% reliability at rated life,to discriminate between the two The stresses in both cases are judged to meet the fatigue limit strength conditions,and the safety factor is further compared.On the basis of ensuring that the impeller achieves the expected use effect,although the rated fatigue strength of the impeller in use is reduced,the safety of the impeller under normal working conditions is theoretically improved.In summary,this paper takes the impeller under normal operating conditions and within the rated life,where fatigue damage occurs,as the research object.The fatigue strength calculation method of the impeller is modified,and the P-S-N reliability verification analysis of the sensitive stress value of the impeller is carried out.The modified fatigue strength is more consistent with the actual condition of the impeller,which theoretically improves the safety of the impeller under normal operating conditions and provides a theoretical reference for the design and application of centrifugal compressor impellers. |
PDF Full Text Request