# Characteristic Analysis of Bump Foil Gas Bearing Under Multi-Physical Field Coupling
## 4 Conclusions  
This paper studies the characteristics of wave-foil-type air bearings. Through theoretical modeling, equation derivation, and numerical calculation, a theoretical model of a bearing and a theoretical model of its temperature field are established, the boundary conditions are set, and the finite difference method is used to solve the distribution of the air film temperature. The influence of parameters such as the rotational speed of the rotor shaft, the thickness of the wave foil, and eccentricity on friction torque and load are analyzed; the influence of the main parameters on air film temperature and the influence of ambient temperature on air film temperature are analyzed. The following conclusions were drawn:  
1. The friction torque of the air bearing increases linearly with its rotational speed, and changes in eccentricity do not affect the increasing speed; within a certain range, the bearing load increases with the increase in wave foil thickness or the decrease in half-wave foil length. In a certain range, with the increase in journal radius clearance, the bearing load decreases. When under high-eccentricity conditions, the effect of journal radius clearance can be ignored; with increasing speed, the maximum temperature of the air film and the maximum pressure of the air film increase, considering the thermal deformation of the rotor, wave foil, flat foil, and other components caused by the increasing temperature, which restricts the speed of the rotor. 2. The temperature distribution in the gas film changes significantly along the circumference. In the section from the inlet to the maximum load of the gas film, the temperature of the gas film rises rapidly, after which the temperature decreases due to the decrease in air pressure, and finally, in the negative pressure region, the gas is absorbed, the  
Figure 17: The influence of ambient temperature change on the deflection angle. pressure increases, and the gas reaches the inlet, where it mixes again with the ambient gas and re-enters the bearing. The high-temperature region is concentrated in the load region. Therefore, a cooling gas flow can be passed through the wave foil near the eccentricity angle to achieve a localized cooling effect. Changes in eccentricity lead to changes in the temperature concentration region, and the localized cooling region needs to be changed when the bearing is subjected to different load conditions. 3. The influence of whether or not the thermal field is considered on the bearing characteristics was investigated. Under the condition of considering the temperature field, the pressure of the air film and the load of the bearing will be somewhat higher than their values under the condition of not considering the temperature field, and the degree of this influence increases with the increase in eccentricity. When the bearing is at a low speed, the maximum temperature of the air film does not change much. Therefore, in the process of practical application, when the bearing is in a low-speed state, one should not consider the temperature conditions for the preliminary assessment of some bearing performance parameters. 4. Bearing load characteristics are affected by different ambient gas temperatures. Within a certain range, as the ambient temperature increases, the maximum gas temperature inside the bearing increases, but the degree of increase gradually decreases, and the degree of increase in load capacity also decreases. With an increase in ambient temperature, the stability of the bearing is improved to a certain extent. Therefore, the temperature difference between the inside and outside of the bearing working area should not be too large, which affects bearing capacity and stability. Bump foil gas bearings are operated under the coupling of multiple physical fields, including the force field, flow field, and temperature field. When rotating at high speed, the gas film pressure formed between the journal and the bearing surface constitutes the flow field.