| The tilting pad bearing has the characteristics of less noise and stable operation,which is mainly used in large rotating instruments.In recent years,with the rapid development of rotating machinery,the challenges and disadvantages of bearing and rotor system instability caused by non-linear factors such as oil film force began to emerge.Therefore,how to ensure stable operation of tilting pad bearings under reasonable parameters become a hot research issue in this field.This article mainly studies the factors affecting the stability of the tilting bearing-rotor system,and the process of the research in detail is as follows:(1)A tilting pad bearing model was established with a structured grid,and a 1.3 million grid model was determined by comparison finally.Then we developed a flow-solid coupling self-defining dynamic mesh method for model calculation and a UDF program which can update the change of shaft neck and tile speed.Therefore,the grid model still has a higher grid quality when the grid is greatly reversed in the process of research.Finally,based on the grid model,this paper uses the SIMPLEC numerical analysis method to solve the model with “full cavitation”using the two-phase flow control equation.(2)Based on Newton iteration principle,the method for solving the static equilibrium position of tilting tile bearing is used to calculate the flow field in equilibrium of the oil film.Considering the inlet pressure,preload factor and rotation speed as variables,the equilibrium oil film flow field and pad angle were calculated under different working conditions.This helps to further analyze the influence of these factors on the properties of the oil film when the tilting pad bearings are in equilibrium.(3)Considering the inertial conditions of the pad,the differential equations of motion between the oil film force of the tilting pad bearing and the rotor are established in this paper,and then the Newmark-β method is used to integrate the differential equations of motion to obtain the axial trajectory of the rotor and the swing track of the tile in a cycle.When analyzing the vibration stability of the tilting bearing-rotor system,the factors such as inlet pressure,fulcrum position coefficient,rotor mass eccentricity,and tile preload were mainly considered.And this paper compares the calculated data with other literature’s to verify the accuracy of the calculation results in this paper.The results show that the increase of inlet pressure,preload coefficient and rotation speed can lead to enlargement of pressure value of oil film flow field,thereby the bearing capacity is enhanced,but these factors will have different effects on the swing angle of pad.The increase of oil inlet pressure will increase the balance swing angle of the pads,while the increase of preloadand speed will reduce the balance swing angle;And when the bearing preload factor is small,the effect of the inlet pressure on rotor amplitude and minimum of oil film thickness is greater,and the rotor amplitude can be reduced by up to 4.8 μm;Both decreasing the rotor eccentricity and increasing the pad position coefficient can reduce the rotor vibration amplitude and improve the rotor vibration stability;The nonlinear characteristics of the oil film force are more significantly with the increasing of rotor mass and eccentricity;In addition,increasing the oil inlet pressure,preload factor and pad position coefficient,as well as reducing the rotor mass eccentricity can also increase the symmetry of the Y-direction oil film stiffness in a stable motion cycle of rotor. |
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