Study Of Vibration Characteristics Modeling Of Shafting Structure And Its Power Flow Analysis

As an important part of power plant,shafting structure is foundation of low vibration and noise design.In addition to study vibration characteristics of shafting structure,the influence of complicated factors on its vibration characteristics cannot be ignored.The shafting vibrational energy will transmit through the supporting structure,and the investigation on its transmission path is the key of relevant vibration control.Therefore,vibration characteristics and energy transmission of shafting structure and its coupling system will be of great theoretical significance and application value.With the topics of structural vibration modeling and power flow characteristics,the following research work has been carried out in this thesis:Three dominant vibration modes of shafting structure are torsional,longitudinal and transverse vibrations andthe vibration displacements are expanded in the form of improved Fourier series solving by vibration differential equation and Rayleigh-Ritz method.The Rayleigh-Ritz method are used to establish a unified solution for three vibration modes.Through the in-plane vibration analysis of flexure shaft,the advantages of unified solution are embodied.It is found that the above modeling method can be used to analyze the influence of arbitrary boundary condition and curvature radius without any significant modification in theoretical derivation and simulation program.Vibration characteristics of shaft structure is studied with various complex boundary taken into account,including elastic boundary conditions,axial load,elastic foundation,and flexural deformation.The arbitrary cross-section and stiffness of non-uniform support are expanded through the even extension of Fourier series,and a unified analysis modeling for the transverse vibration of shaft structure with complex boundary is proposed.Furthermore,the vibration characteristics of flexure shaft structure with axial load and elastic foundation are analyzed,and the reliability of modeling analysis is proved.The influence of various complex factors on the transverse vibration of straight and flexure shaft is studied.Based on the unified solution derived by Rayleigh Ritz energy method,used to model and solve the transverse vibration of complex shafting are modeled and solved.Then the vibration characteristics of stepped shaft,multi-layer coupling structure and multi-spanflexure shaft are modeled and analyzed uniformly considering with arbitrary shaft segments.In the vibration analysis of stepped and multi-layer structure,the effect of cross-section variation is studied and the influence of rotational restraining spring between the coupling interface is fully considered.The multi-span flexure shaft analysis model is established to analyze the influence of coupling stiffness and concentrated mass betweenshafts.In the study of shafting system,a marine propulsion shafting model is applied to study vibration characteristic and power flow transmission considering distributed elastic foundation.The supporting bearing is modeled and analyzed with distributed supporting and compared with the simplified model,which shows the advantages of distributed support model.In the analysis of bending shaft,the deformation by its own gravity is considered and the analysis model is established using stepped flexure shaft.The influence of various shafting parameters on vibration characteristics before and after deformation is analyzed.The study has very important significance for the analysis of shaft vibration and power flow characteristics.In the analyses of vibration and energy transmission of shafting coupling model,the supporting bearing and the foundation are simplified,and the shafting coupling model is established.The difficulty of solving shafting coupling model is that the bearing length is less than the length of the shafting and its foundation.Therefore,starting with the vibration of multi-layer coupled structure,the vibration and power flow characteristics of the coupledmodel are analyzed when the length of middle layer varies.Then the shafting coupling model is solved with unified solutionto analyze the influence of structural parameters and elastic supporting stiffness on its vibration characteristics.For the study of power flow characteristics,the effects of concentrated mass,axial load and supporting stiffness are analyzed and discussed.Finally,the relevant experimental setups are designed and built up for the study of vibration characteristics and power flow transmission of the shafting system,and various experimental measurements are performed.Through the comparison of the measured data with the theoretical prediction,various potential factors causing the measurement error in theexperiments are discussed and analyzed.The work presented in this thesis can provide the theoretical foundation and useful reference for the vibration characteristics and power transmission mechanism and its optimization of various relevant shafting system.