Study On The Static And Dynamic Characteristics Of Self-Acting Gas Bearing

Study on the static and dynamic characteristics of the gas bearing and the dynamic characteristics of the gas bearing-rotor system are the key theoretical content of the design of rotary machinery with the gas bearing support. The static and dynamic characteristics of self-acting gas bearing and the corresponding bearing-rotor system are studied.The main contents are as follows:(1) Based on the compressible fluid Reynolds equation and gas state equation, basic form of gas-lubricated Reynolds equation under isothermal operating conditions is obtained. The static characteristics, such as gas film pressure distribution, load capacity and eccentric angle are calculated for cylindrical and axial-grooved self-acting gas bearings, and the influence of the bearing number, eccentric ratio and width-to-diameter ratio on statics of gas bearing is investigated by finite difference method. By pressure perturbation and linear PH method, gas film pressure distribution for cylindrical self-acting gas bearing is calculated, and compared with the results solved by the finite difference method.(2) A time-dependent mathematical model is used to describe the pressure distribution of self-acting gas bearing with nonlinearity. The finite difference form of gas-lubricated Reynolds equation is obtained by mathematical transformation, and nonlinear gas film forces of cylindrical and axial-grooved self-acting gas bearings are calculated by the Successive Over Relaxation (S.O.R) method.(3) The dynamic model of the gas bearing-rotor system is established. The unbalanced responses and corresponding bifurcation behaviors of the rotor system supported by finite axial-grooved gas journal bearings are investigated by orbit diagram, Poincare map diagram, time series diagram, frequency spectrum diagram and bifurcation diagram. Numerical results reveal that the nonlinear gas film forces have a significant influence on the stability of the gas bearing-rotor system.(4) Dynamic eccentric ratio and eccentric angle are expressed in the form of a plural which contains a periodic perturbation, and the expression of the dynamic gas film pressure disribution and gas film thickness in the complex plane are derived. Dynamic stiffness and damping coefficients of self-acting gas bearing are calculated, and stability analysis of the gas bearing-rotor system is implemented.This study can provide the theoretical references to the dynamic design of tilting-pad gas bearing and compliant foil gas bearing, and can direct the product design of the practical gas bearing-rotor system.