Numerical investigation of a three-lobe gas foil bearing with a double-ring microgrooved top foil based on fluid-structure interaction.

Foil gas bearings are critical supporting components in high-speed oil-free rotating machinery. However, their limited hydrodynamic load-carrying capacity remains a fundamental challenge. To enhance the gas film pressure distribution and load-carrying performance of three-lobe aerodynamic foil bearings, a double-ring circumferential microgroove structure is proposed on the inner surface of the top foil. Based on compressible gas lubrication theory and the fluid-structure interaction method, a numerical model is established to compare grooveless, single-ring microgroove, and double-ring microgroove bearings with different groove spacings under the condition of constant total grooved area. The effects of groove spacing are investigated under rotational speeds of 30000[Formula: see text]70000[Formula: see text] and eccentricity ratios of 0.4[Formula: see text]0.8. The results show that, under different rotational speeds, the grooved structures increase the maximum gas film pressure to approximately 1.04[Formula: see text]1.14 times that of the grooveless bearing, while the load-carrying capacity increases to approximately 1.06[Formula: see text]1.13 times. Under different eccentricity ratios, the maximum gas film pressure increases to approximately 1.02[Formula: see text]1.16 times the original value, and the bearing capacity increases to approximately 1.09[Formula: see text]1.17 times the original value. When the groove spacing of the double-ring microgroove is 4 [Formula: see text], the distribution of the axial high-pressure zone is more continuous, the pressure integration effect is better, and the bearing achieves the optimal load-bearing performance, Compared with the single-ring microgroove structure, this structure reduces the maximum deformation of the ripple foil by 4.7%. The findings demonstrate that a properly designed double-ring microgroove configuration can reshape the axial pressure distribution and increase the effective bearing area, which contributes to improved load-carrying capacity.