# Thermal Characteristics Study of the Bump Foil Thrust Gas Bearing
## 5 Conclusions  
In order to study the thermal characteristics of the aerodynamic bump foil thrust bearing, the air-thermoelastic coupling model is developed in this paper with the heat transfer models of the bearing and thrust plate, and the thermal expansion effect of the bearing structure being considered. The temperature field of the gas thrust bearing is solved through the multi-field coupling algorithm. Finally, the experiments of bearing temperature measurement are carried out under different working conditions. Based on the simulation results, the following conclusions are obtained:  
1. The simulation results show that the surface temperature of the top foil experiences firstly increasing along the rotor rotating direction and then maintaining at a certain value. In the entrance area, the temperature is relatively low, and it will rise sharply after mixing with the recirculation hot air. The top foil temperature in the plane section is almost the same, which is obviously higher than that in the inclined region. In the radial direction, the temperature increases first and then decreases slightly as the radius increases;
2. The value of bearing load capacity calculated by the THD model is higher than the value calculated by the isothermal model, and the differences of them will become more and more apparent as the rotational speed increased and the initial gas film thickness decreased. Compared to the bearing load capacity, the rotational speed has more effect on the temperature. There is little influence on the friction loss power calculated by different models. Injecting the cooling gas flow under the top foil can reduce the bearing temperature, and its efficiency will decrease with the increase in cooling gas flow. For example, under the situation of and the rotor speed of 100 krm and static load of 100 N with bearing structure parameters used in this paper, when the gas cooling flow rate of increased up to 0.2 m\({}^{3}\)/min, the cooling effect reach to the maximum;
3. The variation trends of test bearing temperatures with respect to bearing load and rotor speed are similar with those of simulation results, which verified the reasonability of the THD model to some extent. However, the experimental results are relatively higher than the simulation, which is probably caused by the unclear boundary conditions in the experiments which should be clarified in the simulations or due to the measurement error during the experiment. The current simulation ignored some factors, which makes the simulation results are not exactly the same with the experiment results. The further research will consider more accurate structure model and thermal model, including the surface roughness of the foils and the friction between them, and more complex heat transfer models, etc. Conceptualization, J.D. and X.L. ; methodology, X.L. ; software, X.L. ; validation, X.L., C.L., J.D. and G.N. ; formal analysis, J.D. ; investigation, G.N. ; resources, J.D. ; data curation, J.D. ; writ-ing--original draft preparation, X.L. ; writing--review and editing, X.L. ; visualization, C.L. ;  
Figure 21: Relationship between bearing top foil temperature and rotational speed. supervision, C.L. ; project administration, J.D. ; funding acquisition, C.L. and J.D. All authors have read and agreed to the published version of the manuscript. Not applicable. The data presented in this study are available on reasonable request from the corresponding author. The authors declare no conflict of interest. Not applicable. The data presented in this study are available on reasonable request from the corresponding author. The authors declare no conflict of interest. The work described in this paper was supported by National Key R&D Program of China (Grant No. 2018 YFB2000100) and the National Natural Science Foundation of China (Grant No. 52005126). Not applicable. * [PERSON] and [PERSON] (2015) [PERSON]; [PERSON] A fully coupled 3D thermo-elastohydrodynamics model for a bump-type compliant foil journal bearing. _Tribol. Int._**2015**, _82_, 110-122.