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The axial throughflow cooling is a realistic solution for the purpose of thermal management in the hydrodynamic gas foil bearings operating at ultra-high rotational speed and mini bearing clearance. In order to illustrate the effects of axial throughflow cooling within the fluid-solid coupled heat transfer mode on the aerodynamic and thermal behaviors of hydrodynamic gas foil journal bearing, a steady three-dimensional fluid-solid coupled numerical simulation is performed in the present study by assuming that the journal-bearing works in a steady-state condition with a fixed eccentricity ratio of 0.9. The results show that the shearing-induced circumferential flow is significantly dominant in the hydrodynamic air film layer. At both edges of the foil bearing section, local suction flow into the bearing clearance and local leakage flow out the bearing clearance happen simultaneously at different circumferential positions. The increase of axial throughflow mass flowrate plays an effective role on improving the cooling capacity. However, it should be noteworthy that the bleeding air pressure is prompted in a nearly quadratic relationship along with the increase of axial throughflow mass flowrate. Due to the non-uniformity nature of viscous-shearing heat generation inside the hydrodynamic gas foil bearing with a big eccentricity, the temperature on the shaft and top foil surfaces takes on a non-uniform distribution. The peak temperature generally has a 20 K–30 K difference with respect to the mean temperature.

Numerical simulations were performed to illustrate the influences effects of annular-cooler surface roughness on wind resistance and thermal environment in a high-speed centrifuge chamber, with the use of multi-reference-frame (MRF) method and classical roughness-modified model. In the present study, the absolute roughness height was specified in a range form 0.05 mm–2.5 mm. With respect to the clearance between rotating-arm tip and stationary-cooler surface, the relative roughness height was changed from 0.0014 to 0.07 accordingly. The results show that the flow field inside the centrifuge chamber is of highly three-dimensional feature. With the increase of surface roughness, the wind resistance is increased monotonously. With regard to the thermal environment, the maximum temperature inside the centrifuge chamber takes on a non-monotonous variation along with the surface roughness height, due to the two contrary influencing roles of surface roughness on the viscous dissipation heat generation and the heat removal capacity. In general, the use of roughed cooler-wall is a promising scheme for reducing the environmental temperature in a high-speed centrifuge chamber. Under the present research conditions, a more favorable relative roughness height is identified in term of a comprehensive factor that reflects the benefit of roughed surface on the reduction of maximum environmental temperature at the pay of aerodynamic penalty.