Research On Vibration Control Of Rotor And Gear System Based On Integral Squeeze Film Damper

Rotating machinery,such as aeroengine,compressor and turbogenerator set,are key equipment in national defense and industrial production in China.The problem of over-critical vibration caused by unbalanced mass is widespread with these large-scale machinery,making it impossible for them to start normally.In addition,gear system,one of the most widely used power transmission devices in mechanical equipment,also causes a vibration problem under internal and external excitation,which has become a key factor affecting their operational stability and service life.The vibration problem with mechanical equipment has seriously restricted the improvement of the combat capability of our military equipment and the increase of the economic benefits of enterprises.Therefore,it is urgent to develop new vibration control methods for rotors and gear systems which are easy to apply in engineering.In this thesis,aimed at the problem of over-critical vibration caused by unbalanced mass of rotating machinery and the vibration of gear transmission system,a new technique of vibration control based on integral squeeze film damper(ISFD)was proposed.The vibration reduction performance of ISFD in rotor and gear system was studied through combining theoretical analysis and experiments.The main work of this thesis is as follows:(1)Without considering the influence of oil film stiffness,the influence of different structural parameters of ISFD on its radial stiffness was studied The results show that the radial stiffness of ISFD increases linearly with the increase of axial length,decreases approximately linearly with the increase of oil film gap,and varies irregularly with the increase of S-shaped spring distribution angle,radial thickness and radial position.The radial static stiffness of ISFD was calculated and measured,the results of which show that ISFD has excellent linear stiffness characteristics in a wide load range.The vibration response of ISFD-single disk Jeffcott rotor under different unbalances was studied experimentally,the results of which show that ISFD can provide linear damping force in a wide unbalance range,and the stiffness of oil film remains unchanged.Besides,the damping coefficient of ISFD was calculated using modal analysis method.(2)An active vibration control method of rotor system based on ISFD was proposed.By actively controlling the oil supply of ISFD,the targeted suppression of the over-critical vibration of rotor is realized.An active vibration control system based on ISFD was developed,and a switching control strategy based on rotational speed was designed.The effect of the rotational speed-based ISFD switching control method on the suppression of the over-critical vibration of single-span and single-span cantilever rotor was studied experimentally.As indicated by the results of the switch control experiment,the maximum vibration reductions of the single-span rotor in horizontal and vertical directions are 39%and 42%,respectively;the maximum vibration reductions of the single-span cantilever rotor in horizontal and vertical directions are 34%and 38%,respectively.Compared with the traditional passive control method of ISFD,the rotational speed-based ISFD switching control method can control the over-critical vibration of rotor in a targeted manner.(3)A vibration control method of gear system based on ISFD was proposed.Starting from the path of vibration transmission of gear system,ISFD is used to reduce and isolate the meshing excitation of the gear system,and the feasibility of using ISFD for vibration reduction of gear shafts is verified by theoretical analysis and experiments.The influence of ISFD installation position and damping fluid viscosity on the vibration reduction characteristics of gear shafts was studied.The results show that ISFD support can reduce the meshing impact vibration of gear shafts at different rotational speeds,and has a wide vibration reduction frequency band.In order to achieve a better vibration reduction effect,priority should be given to installing ISFD on a shaft with larger vibration.ISFD using dimethyl silicone oil as damping fluid can reduce the vibration of the gear shaft by more than 50%,and the amplitude of decrease increases with the increase of damping fluid viscosity.Aiming at the vibration of multiple parallel gear shafts and gear shaft misalignment fault in engineering,the suppression effect of ISFD on its complex vibration was studied experimentally.The results show that ISFD can effectively attenuate the shock vibration of multiple parallel gear shafts,and reduce the peak vibration acceleration of the bearing block by about 30%.ISFD can also effectively reduce the vibration caused by misalignment fault of gear shafts,and satifactorily suppress the vibration of characteristic frequency components and resonance modulation frequency components.On this basis,an involute spur gearbox based on ISFD technique was developed and designed to study the vibration reduction performance of ISFD under different loads and rotational speeds.The results show that ISFD has a satisfactory vibration reduction performance for gearbox under different loads and rotational speeds,and can effectively suppress the high frequency vibration components of gearbox,thus exhibiting the promising application prospect of ISFD in gearbox.(4)An integral elastic ring squeeze film damper(IERSFD)structure is developed.It integrates the traditional elastic ring squeeze film damper with a novel and compact structure,and has the characteristics of low stiffness for elastic support and vibration reduction for squeeze film damper.Using dimethyl silicone oil as the damping fluid of IERSFD,the vibration reduction characteristics of gear shafts with IERSFD at different rotational speeds and damping fluid viscosities were studied.The results show that IERSFD can effectively reduce the shock and vibration of gear's meshing,and attenuate vibration for most of the gears' frequency components within a wide vibration reduction frequency band.Within a certain viscosity range,the vibration reduction becomes more effective with the increase of the damping fluid viscosity of IERSFD.In summary,the research results of this thesis have broaden the application fields of ISFD and provided a new method for vibration control of rotor and gear system.ISFD has a good vibration reduction performance,and is easy to apply in engineering.The research contents contribute to the design of rotating machinery characterized by low vibration,high stability and long life,thus presents vital engineering significance.