Research On Stability Of Sliding Bearing Rotor System Based On Nonlinear Oil Film Force Of Finite Length Sliding Bearing

As one of the important supporting components in rotating machinery,sliding bearing is widely used in large rotating equipment such as steam turbine and turbine.With the upgrading and innovation of engineering equipment,the requirements for stable operation accuracy of equipment are increasing.Therefore,it is of great significance to quickly solve the nonlinear oil film force of the sliding bearing rotor system for real-time monitoring and control of the stable operation of rotating machinery.The acquisition of nonlinear oil film force is inseparable from the selection of bearing model and the solution of Reynolds equation.At present,in the study of bearing model,infinite long and infinite short sliding bearing models are often used,but the axial or circumferential oil film force of sliding bearing is ignored.The sliding bearing model is more idealized and simplified,so the calculation results can not accurately reflect the stability of the system.In the existing calculation methods of Reynolds equation,researchers mainly use numerical method or database method to solve Reynolds equation.The complex iterative process and database cost are difficult to use and the calculation efficiency is low,which is not suitable for practical engineering application scenarios that need fast response.Aiming at the practical engineering application,based on the nonlinear oil film force model of finite length bearing,this paper adopts the analytical method of separating variables to carry out the analytical solution of nonlinear oil film force.The analytical solution equation of oil film force based on this model is derived,and the analytical solution of oil film force is obtained.At the same time,the stability analysis of finite length sliding bearing rotor system is carried out.The experimental results show that the theoretical analysis is in good agreement with the experimental results.The main research contents and conclusions of this paper are as follows :(1)Establishment of nonlinear oil film force analytical model of finite length journal bearing.By establishing the nonlinear oil film force analytical models of infinite long sliding bearing,infinite short sliding bearing and finite long sliding bearing,and comparing the advantages and disadvantages of oil film force calculation,a nonlinear oil film force analytical model of finite long sliding bearing closer to engineering practice is determined.The calculation method proposed by this model can be widely used to solve the oil film force in engineering,so as to realize the rapid analysis of the stability of sliding bearing rotor system in engineering.(2)Solution of nonlinear oil film force analytical model of finite length journal bearing.The three boundary conditions of Sommerfeld,semi-Sommerfeld and Reynolds are discussed and compared.Based on the Reynolds boundary condition,the nonlinear differential equation of oil film pressure is derived by using the separation variable method.The oil film pressure is obtained by solving the special solution and the general solution,and the oil film force is obtained after integration.The accuracy of the solution method is verified more intuitively by comparing with the oil film pressure distribution solved by the numerical method,the relationship between the maximum oil film pressure and the aspect ratio,and the circumferential and axial distribution of the oil film force under different aspect ratios.Finally,a method for solving the nonlinear oil film force of finite-length sliding bearings based on Reynolds boundary conditions is proposed.(3)The stability analysis and experimental study of finite length journal bearing rotor system.Based on the solution of nonlinear oil film force of finite length sliding bearing,the dimensionless stable operation parameter Op is introduced to discuss the stability of finite length sliding bearing rotor system.Based on the rotor test bench,the related experiments on the stability of the finite length sliding bearing rotor system are carried out.The experimental results show that the theoretical analysis is in good agreement with the experimental results.