Static performance of the aerostatic journal bearing with grooves

Abstract

Aerostatic bearings are widely employed in precision machines due to their properties of low friction, low heat conduction, and long-life operation. In this work, static performance of the journal bearing with rectangular grooves is investigated numerically. The effect of geometrical parameters such as axial groove length ${\overline{g}}_l$ , circumferential groove length ${\overline{g}}_w$ , orifice diameter d_f, groove depth g_h, misalignment angles ${\varphi }_x$ and ${\varphi }_y$ on the load capacity $\overline{F}$ , stiffness $\overline{K}$ , and gas flow rate $\overline{Q}$ are analyzed systematically. The resistance network method (RNM) is utilized to solve the Reynolds equation required in the analysis. Performance parameters including pressure distribution P, load force $\overline{F}$ , stiffness $\overline{K}$ , and gas flow rate $\overline{Q}$ are examined in the simulations.

It is revealed from the simulations that the proper value of axial groove length ${\overline{g}}_l$ to obtain a better static performance varies from 1/8 to 1/2 when d_f varies between 0.11 and 0.29 mm, respectively. Therefore, a larger load force and stiffness can be obtained if ${\overline{g}}_l$ is chosen to be 1/4, when diameter of the bearing orifice d_f equals 0.17 mm. It is also suggested that ${\overline{g}}_w$ be chosen from the range of 1/6 and 1/3 to obtain a better static performance and a smaller gas flow rate. $\overline{F}$ decreases with an increase in d_f when ${\overline{g}}_l$ is set to be 1/8. However, the load force $\overline{F}$ increases with an increase in d_f when ${\overline{g}}_l$ varies from 3/8 to 1/2. ${\overline{g}}_l$ has a significant influence on the changes of $\overline{F}$ with d_f when ${\overline{g}}_w$ is set to be constant. Therefore, d_f should be selected according to ${\overline{g}}_l$ for an optimal design. The increase of misalignment angle ${\varphi }_x$ leads to an increase in the load force $\overline{F}$ . ${\varphi }_y$ has little influence on the load force $\overline{F}$ . Misalignment angles ${\varphi }_x$ and ${\varphi }_y$ have little influence on stiffness $\overline{K}$ and gas flow rate $\overline{Q}$ . Therefore, it is preferable if ${\varphi }_x$ is larger than 0 rad.