Effect of Surface Waviness on the Performances of an Aerostatic Thrust Bearing with Orifice-Type Restrictor

In this paper, four waviness types are presented to investigate the effect of surface waviness on the static performance, dynamic performance and stability of an aerostatic thrust bearing with orifice-type restrictor. The influences of wave amplitude and rotational speed on the bearing performances are studied. The Reynolds equation is first solved through small perturbation method to obtain the static and dynamic characteristics. Subsequently, by adopting an iterative method based on the acquired dynamic coefficients, a numerical method is proposed to analyze the bearing stability. The calculated critical supply pressure is compared with that obtained by the traditional orbit method and it indicates that the proposed method has higher computational efficiency. The results show that the surface waviness has great influence on the bearing performances and the effect becomes increasingly pronounced with the growth of wave amplitude. The performances are more sensitive to the waviness arranged in bearing radial direction than circumferential direction. The enhancement of certain performance is always accompanied by the decline of another performance for the bearing with wave pattern on the surface, which leads to the fact that the bearing performances cannot be comprehensively improved in static characteristic, dynamic characteristic and stability. Besides, high rotational speed will cause pneumatic instability more readily. Finally, a stiffness measuring experiment and a modal test are performed to verify the accuracy of computational analysis and results.