Study On The Influence Of The Preload Of The Upper And Lower Boxes Of The Sliding Bearing On The Vibration Characteristics Of The Rotor

Sliding bearing is widely used in many fields of industrial production,especially in high-speed and heavy-duty occasions,due to its advantages of large bearing capacity,good vibration resistance,high operation accuracy,low noise and long service life.With the development of modern industrial machinery towards the direction of high reliability and high stability,there are higher requirements for the vibration characteristics of shafting.The shafting equipped with sliding bearing often has problems of vibration increase or even vibration instability due to the influence of rotor eccentricity and other factors.In engineering practice,some manufacturers control shafting vibration by adjusting the preload of bolts in the upper and lower case of sliding bearing,but there is no theoretical basis.This project takes DQ18 sliding bearing as the research object.Firstly,the static model of DQ18 sliding bearing shafting is established.By adjusting the preload of bearing upper and lower box,the radius clearance of bearing is changed,so as to change the oil film thickness and stiffness.Then,the dynamic model of shafting is established,and the influence of preload of bearing upper and lower box on shafting vibration is discussed,It provides theoretical guidance for suppressing vibration instability of shafting and optimizing structural design.The analysis results show that with the preload of the upper and lower housing increasing,the radial clearance of the bearing decreases correspondingly,while the eccentricity,oil film stiffness and damping coefficient of the bearing increase nonlinearly,while the deflection angle and minimum oil film thickness decrease nonlinearly,which has obvious suppression effect on the vibration phenomenon caused by the unbalanced excitation of the rotor mass.The main research contents are as follows:The paper expounds the research background and significance,expounds the research progress of the dynamic and static characteristics of sliding bearing,the influence of the support stiffness of sliding bearing on the vibration characteristics of shafting,and the research progress of the influence of the preload of the upper and lower box of sliding bearing on the vibration characteristics of shafting,and summarizes the research content and main frame of this paper.The paper,the influence of preload on bearing radius clearance is analyzed,and the displacement of bearing radius clearance under different preload adjustment is analyzed by finite element method.The influence of bearing radial clearance on the vibration instability of shafting is analyzed.Finally,the shafting dynamic model under the excitation of rotor mass unbalance is established.Based on the finite difference method and Reynolds boundary conditions,the influence of different bearing radius clearance on the static characteristics of sliding bearing,such as oil film dynamic pressure,oil film thickness,eccentricity,deflection angle and bearing capacity,is analyzed.According to the static characteristics of sliding bearing,the fluid simulation software Fluent is used to further analyze,and the distribution law of oil film dynamic pressure and bearing capacity under different bearing radius clearance is simulated,and the results are compared with those calculated by finite difference method.Then,the dynamic characteristics of the journal bearing are analyzed by using the pressure disturbance method,and the static characteristics of the journal bearing with the change of the radial clearance and the mapping relationship between the static characteristics and the dynamic oil film stiffness and damping are obtained.Based on the theory of multi-body dynamics,the influence of different bearing radius clearance on the dynamic oil film stiffness and damping under the excitation of rotor mass unbalance and the vibration characteristics of shafting in engineering practice are analyzed;The vibration response experiment of shafting was carried out to detect the vibration characteristic parameters of shafting under different preloads of upper and lower box in actual operation,and the results were compared with the numerical simulation results,so as to calculate and solve the optimal preload of upper and lower box of sliding bearing.The paper studies the influence of preload of sliding bearing upper and lower box on shafting vibration characteristics,which has great theoretical significance and engineering application value to solve the problem of excessive shafting vibration.