Research On Vibration Control Of Rotor System Based On STF Damping

Rotating machinery such as industrial compressor,steam turbine,aero engine and all kinds of motors are the core equipments of industry and play a very important role in the fields of aviation,electric power,petrochemical,metallurgy,etc.During the operation process,excessive vibration often generates in the rotor system,which is the core component of rotating machinery.The excessive vibration can damage the stability of rotating machinery,and even force the units to shut down or destroy in severe case.There are two main reasons for the vibration of rotating machinery based on mechanism analysis,one is the forced vibration caused by external excitation such as unbalance or the other fault excitation,e.g.collision,misalignment,etc.;the other is large amplitude and low frequency self-excited vibration caused by small clearance and medium disturbance force.With the development of the modern rotating machinery,its rotor systems have more and more slender shaft and reduced rotor-stator gap clearance in order to reach high efficiency,and blade aerodynamic load is also increasingly growing.All these enlarge the occurrence possibility of forced vibration and self-excited vibration.So,in order to ensure the stable operation of rotating machinery,the vibration control of rotor system is necessary.Variable damping methods,such as the damper made of electro-rheological fluid or magneto-rheological fluid,have been widely applied in the vibration control of rotor system,but all the variable damping devices based on these smart materials need external energy and additional structures,which may increase the complexity of the structure of rotating machinery.So,the more simply variable damping control method is urgent needed.Shear Thickening Fluids(STF),which has the characteristics of rapid increase in viscosity and damping when the relative shear rate increases,and no need for external energy,can be used for the development of the variable damping device and greatly simplify the devices' structure.Therefore,the STF damping is adopted to control the forced and self-excited vibration of rotor system in this paper,and passive and semi-active control of rotor system vibration is studied.The specific work is as follows:(1)A novel damping device suitable for vibration control of rotor system based on the adaptive damping characteristic of STF is developed,so as to overcome the complexity of ER/MR damping devices,which can offer a new way for realizing simplification of the vibration control of rotating machinery.The mathematical model of the new-type damper is studied.Experimental results show that the designed STF damper has good variable damping performance and considerable application value;and fitting study using the LM algorithm and comprehensive comparison shows that the Bouc-Wen model can be used to describe the nonlinear damping and stiffness characteristics of STF dampers very well.(2)The inhibition mechanism of the forced vibration of rotor system with the STF damping is studied.Suppression for the forced vibration of rotor system using the STF damper is presented.The incremental harmonic balance method combined with the arc length method is adopted for solving the steady-state response and unbalance response of rotor system with nonlinear hysteretic force.The dynamic model of the STF damping-rotor system and the STF damping-vibration absorber-rotor system is established to conduct the dynamic characteristic research.Meanwhile,the corresponding test bench is set up and the test verification is carried out.Both theoretical and experimental analysis show that the STF damping can significantly inhibit large amplitude vibration of rotor system in resonance region,and the damping effect leads to a nonlinear growth with the increase of unbalance vibration.Therefore,the STF damping has the adaptive characteristics of amplitude suppression.It can also inhibit the resonance peak of the dynamic vibration absorber and to make it have a better effect.(3)The inhibition mechanism of the STF damping on self-excited vibration of the simple rotor system and rotor system in practical engineering is studied.By combining fixed interface mode synthesis method for dimension reduction with Newmark-? numerical solution method,the vibration response characteristics and parameter influence of the rotor system under the excitation of the Alford force and fluid sealing force are studied.On this basis,the control method to select damping by using the stability regional map of the rotor system with self-excited vibration is proposed.The results show that it has a very good effect on suppressing the self-excited vibration induced by Alford force or fluid sealing force through applying the nonlinear damping method.(4)The conception that the damping control could be realized by controlling the relative shear velocity is proposed so that semi-active control of rotor system is realized.The experimental research on the semi-active control of rotor system by using the STF damper driven by a vibration exciter is carried out and simulation analysis is conducted.The results show that the damping force can be adjusted and increased,the resonance amplitude of the rotor can be further reduced by applying the active control frequency,and the semi-active control of the rotor vibration is then realized.In the end,the idea using the laminated piezoelectric actuator to control the STF damper is presented in order to ensure simplicity of the variable damping device.