Radial turbines with nozzle guide vanes are widely used in various size turbochargers.However,due to the interferences with guide vanes,the blades of impellers are exposed to intense unsteady aerodynamic excitations,w...Radial turbines with nozzle guide vanes are widely used in various size turbochargers.However,due to the interferences with guide vanes,the blades of impellers are exposed to intense unsteady aerodynamic excitations,which cause blade vibrations and lead to high cycle failures(HCF).Moreover,the harmonic resonance in some frequency regions are unavoidable due to the wide operation conditions.Aiming to achieve a detail insight into vibration characteristics of radial flow turbine,a numerical method based on fluid structure interaction(FSI) is presented.Firstly,the unsteady aerodynamic loads are determined by computational fluid dynamics(CFD).And the fluctuating pressures are transformed from time domain to frequency domain by fast Fourier-transform(FFT).Then,the entire rotor model is adopted to analyze frequencies and mode shapes considering mistuning in finite element(FE) method.Meanwhile,harmonic analyses,applying the pressure fluctuation from CFD,are conducted to investigate the impeller vibration behavior and blade forced response in frequency domain.The prediction of the vibration dynamic stress shows acceptable agreement to the blade actual damage in consistent tendency.展开更多
Time-varying stiffness is one of the most important dynamic characteristics of rolling element bearings.The method of analyzing the elements in the bearing stiffness matrix is usually adopted to investigate the charac...Time-varying stiffness is one of the most important dynamic characteristics of rolling element bearings.The method of analyzing the elements in the bearing stiffness matrix is usually adopted to investigate the characteristics of bearing stiffness.Linear mapping structure of the bearing stiffness matrix is helpful to understand the varying compliance excitation and its influence on vibration transmission.In this study,a method to analyze the mapping structure of bearing stiffness matrix is proposed based on the singular value decomposition of block matrices in the stiffness matrix.Not only does this method have the advantages of coordinate transformation independence and unit independence,but also the analysis procedure involved is geometrically intuitive.The time-varying stiffness matrix of double-row tapered bearing is calculated and analyzed using the proposed method under two representative load cases.The principal stiffnesses and principal axes defined in the method together indicate the dominant and insignificant stiffness properties with the corresponding directions,and the vibration transmission properties are also revealed.Besides,the coupling behaviors between different shaft motions are found during the analysis of mapping structure.The mechanism of the generation of varying compliance excitation is also revealed.展开更多
基金funded by the National Natural Science Foundation of China(No.51176013)the Specialized Research Fund for the Doctoral Program of Higher Education(No.20111101130002),China
文摘Radial turbines with nozzle guide vanes are widely used in various size turbochargers.However,due to the interferences with guide vanes,the blades of impellers are exposed to intense unsteady aerodynamic excitations,which cause blade vibrations and lead to high cycle failures(HCF).Moreover,the harmonic resonance in some frequency regions are unavoidable due to the wide operation conditions.Aiming to achieve a detail insight into vibration characteristics of radial flow turbine,a numerical method based on fluid structure interaction(FSI) is presented.Firstly,the unsteady aerodynamic loads are determined by computational fluid dynamics(CFD).And the fluctuating pressures are transformed from time domain to frequency domain by fast Fourier-transform(FFT).Then,the entire rotor model is adopted to analyze frequencies and mode shapes considering mistuning in finite element(FE) method.Meanwhile,harmonic analyses,applying the pressure fluctuation from CFD,are conducted to investigate the impeller vibration behavior and blade forced response in frequency domain.The prediction of the vibration dynamic stress shows acceptable agreement to the blade actual damage in consistent tendency.
基金the Joint Funds of the National Natural Science Foundation of China(Grant No.U1834202).
文摘Time-varying stiffness is one of the most important dynamic characteristics of rolling element bearings.The method of analyzing the elements in the bearing stiffness matrix is usually adopted to investigate the characteristics of bearing stiffness.Linear mapping structure of the bearing stiffness matrix is helpful to understand the varying compliance excitation and its influence on vibration transmission.In this study,a method to analyze the mapping structure of bearing stiffness matrix is proposed based on the singular value decomposition of block matrices in the stiffness matrix.Not only does this method have the advantages of coordinate transformation independence and unit independence,but also the analysis procedure involved is geometrically intuitive.The time-varying stiffness matrix of double-row tapered bearing is calculated and analyzed using the proposed method under two representative load cases.The principal stiffnesses and principal axes defined in the method together indicate the dominant and insignificant stiffness properties with the corresponding directions,and the vibration transmission properties are also revealed.Besides,the coupling behaviors between different shaft motions are found during the analysis of mapping structure.The mechanism of the generation of varying compliance excitation is also revealed.
