Analysis Of Rotor Characteristics With Squeeze Film Damper Bearing And Research On The Damping Mechanism

Squeeze film damper(hereinafter referred to as SFD)has been widely applied in high speed turbo-machines,thanks to its effective vibration damping capacity as well as the simple and reliable structure.In order to research the characteristics of SFD-rotor system and the damping mechanism in depth,the theoretical analysis and test verification were carried out based on the SFD numerical model and the finite element model of dual-rotor.This thesis may provide theoretical reference and guidance for the design,control and examination of SFD-rotor system.The main research contents and conclusions were summarized as follows:(1)The influence on film force characteristics of the SFD structure parameters and working condition was studied by numerical simulation.The results showed that: excessive eccentricity(>0.6)would dramatically increase the film force and lead to a strong nonlinearity;SFD failure could occur if the ratio of film clearance to diameter is less than 0.0005;High temperature would impact the damping effect.(2)Through SFD-single rotor finite element modeling,the rotor vibration characteristics by SFD design parameters and working condition was analyzed.Simulation showed that,for the constructed rotor model: the critical speed increased non-linearly when the ratio of film clearance to diameter <0.0025;damping efficiency was limited with a big ratio;so as 0.0025~0.00375 was advised.When the eccentricity was more than 0.4,the damping characteristics evaluated dramatically,which could impact the rotational stability;Weak ratio of film length to diameter(<0.125)could lead to excessive eccentricity(>0.6)and poor damping effect;When the film was too long,the critical speed could increase rapidly and deviate far from the designated;so as 0.375~0.5 was advised.(3)The abnormal similar model of one turbo-shaft engine was designed based on the dynamic similarity theory.The characteristics of rotor with/without SFD were obtained by finite element simulation.The results showed that: SFD increased the critical speeds,effectively damped the peak amplitude and eased to surpass the critical speed;the peak amplitude suppression of the single rotor was about 39%~76%,and that of the dual-rotor with the common cavity was about 58%~80%.(4)The SFDs were assessed and discussed: When given consistent-phase unbalance loaded,to the dual-rotor with common cavity,the highest eccentricity of SFD4 was 0.4,located at the 1st order critical speed under inner-rotor main excitation.The other configured SFD eccentricities were all under 0.34.As conclusion,all SFDs satisfied the expected design compliance.(5)The unbalance response of the dual-rotor with common cavity showed that: The common cavity linked with the casing stiffness significantly reduced the critical speeds.The common cavity may lead a more sensitive influence on the rotor displacement when non-linear elements like SFD added into the system.