Characteristic Analysis Of High Speed Floating Ring Bearing-Rotor System

The floating ring hydrostatic/hydrodynamic bearing introduces a floating ring based on the hydrostatic/hydrodynamic bearing, the friction loss is reduced and the stability is improved, which is used comprehensively in some situations that require high speed. The floating ring bearing-rotor system in the turbocharger was studied and the static and dynamic characteristics were calculated. The mathematical model was established to calculate stability of the system considering the mass of the ring and the stiffness of the elastic rotor and the threshold speed was calculated.First, this paper established the dynamic Reynolds equations of the inner and outer layer film in the floating ring bearing and the boundary conditions, the formulas of static and dynamic characteristics were deduced; then the inner and outer film were meshed and the Reynolds equation was calculated by the difference method, the processing method on the boundary of oil cavity was described. In calculating the dynamic characteristics the differential equations need to make the corresponding changes because the step sizes of grids were not equal in meshing. The program used the dichotomy to get the balanced position of floating ring. The dynamical models were established considering the mass of ring and the stiffness of rotor, the stability criterion was established by the Routh-Hurwitz guidelines and the threshold speed was obtained by the iterative program.One bearing was selected to calculate, the static and dynamic characteristics were got under different speeds and eccentricities and we can visualize the changing curve of them. Then the threshold speeds were calculated as the ring mass and the stiffness of the rotor changed and the influence of two factors to the stability of the system was analyzed. The results indicated that for this bearing, the stability would decrease considering the ring mass and the threshold speed decreased with increasing mass; the stability of elastic rotor was lower than the rigid rotor and the threshold speed increased with increasing stiffness.