Vibration characteristics of turbocharger rotor system considering internal thread texture parameters of semi-floating ring bearing

Abstract

The internal thread texture causes changes in the dynamic characteristics of the oil film of the semi-floating ring bearing, which affects the amplitude of vibration and operating life of the turbocharger rotor system. Based on the fluid lubrication theory, the oil film governing equation of a semi-floating ring bearing with surface texture parameters is derived. The effects of the texture depth, position, and number of turns of the internal thread on the dynamic characteristics of the bearing oil film, such as the maximum pressure, load-carrying capacity and stiffness damping, are analyzed. Taking a type of turbocharger as an example, a hydrodynamic model is established to analyze the oil film lubrication in the semi-floating ring bearings, and the dynamic characteristic of the oil film is analyzed by computational fluid dynamics method. The results show that the maximum pressure, bearing capacity, and stiffness damping coefficient of oil film increase firstly and then decrease with the increase of texture depth and the number of thread turns in the range of journal rotation speed from 1000 to 20,0000 r/min. Compared with the non-texture bearings, the dynamic characteristics coefficients of the oil film such as bearing capacity and stiffness damping increase the most, when the depth of texture is 0.006 mm and the number of thread turns is 9. Secondly, the dynamic characteristic coefficient of oil film is improved when the texture is distributed in the middle than on both sides. The thread texture with appropriate parameters can suppress the rotor system vibration amplitude. The conclusion can provide a reference for the design of textual parameters of semi-floating ring bearings.

Research on Sudden Unbalance Response of Rigid-Elastic-Oil Coupled Ball Bearings

“…where m b is the vibration mass concentrated at the journal (including the masses of the bearing, damper, and rotor), G b is the gravity of the journal, F r is the radial oil film force, F t is the circumferential oil film force, F dr is the radial component of the elastic force acting on the journal, F dr = 0.5K s [e d cos(φ d − φ b ) − e b ], F dt is the tangential component of the elastic force acting on the journal, F dt = 0.5K s [e d sin(φ d − φ b )], T i indicates the support reaction at the boss of the elastic ring, T i = k er e b cos(θ i − φ b ), k er is the elastic ring stiffness, N is the number of inner bosses in the elastic ring, θ i is the angle between the i th inner boss and the negative direction of the Z-axis, θ i = β + 2(i − 1)π/N, K y is the squirrel cage stiffness in the Y-axis direction, K z is the squirrel cage stiffness in the Z-axis direction, y and z represent the offset distance of O j in the YO b Z plane, G d is the gravity of the disc, F sr is the radial component of the elastic force acting on the disc, In Equation ( 1), K y and K z are obtained using the finite element method, while F r and F t are determined from the oil film force generated via the ERSFD. Combined with Figure 1b and without considering the damping hole, the governing equation for the transient oil film pressure can be written as follows [46]:…”