Dynamical Analysis Of Elastic Ring Squeeze Film Damper-Rotor System

The elastic ring squeeze film damper(ERSFD)was first designed by engineers in the former Soviet Union.Because of its good ability to reduce vibration,frequency modulation and suppress oil film nonlinearity,it has been used in aero engines and introduced into our country.As the new aero-engines,gas turbines,high-speed centrifuges and flywheel energy storage machine have higher requirements for vibration control,ERSFD has broad application prospects.Due to the lack of sufficient theory and experimental experience for the coupling mechanism between the elastic ring and the oil film,the measurement and prediction of equivalent oil coefficients,the analysis of two-phase flow and the influence of ERSFD on the rotor dynamics,it is hard to improvement and application of ERSFD.In response to this phenomenon,the thesis has done the following work.(1)A fluid-structure coupling calculation method is proposed based on finite element theory and fluid lubrication theory.On this basis,a semi-analytical method(SAM)which can save more than 90% of calculation time is proposed based on the hypothesis of short bearing.The method is verified by comparing the results of numerical simulation and experiment.Then,the influence of the deformation of elastic ring,amount of bosses,supply-holes,supply pressure,connection oil holes,and seal on the oil pressure are analyzed.The perturbation method and the parameter identification method are used to analyze the equivalent oil damping,stiffness,mass coefficients under different structural parameters(2)Combining three different rotor dynamics models,the elastic ring squeeze film damper-rotor dynamics calculation model and semi-analytical model are proposed.Then the influence of factors such as seal,rolling bearing,whirl radius,whirl speed,external excitation,amount of bosses,elastic ring thickness and oil film thickness on the dynamic response of the rotor is analyzed.The results show that the elastic ring squeeze film damper has a better ability to supress the bistable response than the traditional squeeze film damper.(3)An elastic ring squeeze film damper-rotor test rig was built to measure the deformation shape of the elastic ring,variety of temperature and the relationship between the inner and outer oil pressure and analyze the influence of the oil supply pressure,the excitation frequency and the whirl radius on the oil pressure.Then the equivalent oil film damping,stiffness and mass coefficients under different oil supply pressure and rotation speed are analyzed experimentally.The result proves that the equivalent damping coefficient has the most obvious effect,and the effect of the equivalent mass coefficient is greater than that of the equivalent stiffness.Next,the resonance response,bistable response,and superharmonic response of the rotor under different oil supply pressures,unbalanced mass are analyzed.(4)Based on the homogeneous flow model,a fluid-structure coupling method that considers the effects of two-phase flow is proposed.The method is verified by comparing the results with the experimental and numerical simulated results.Furthermore,the influence of structure parameters and operational condition on the taking place condition of two phase flow,the influence of two phase flow on the oil pressure,equivalent coefficients and rotor dynamic response are analyzed.Finally,computational fluid dynamics(CFD)is used to analyze the process of cavitation and its influence on the oil pressure of ERSFD.The results show that the two-phase flow will affect the oil film pressure,the equivalent oil coefficient,and may cause the bistable response of rotor.