Numerical and Experimental Investigation on the Performance of Backflow Channel Aerostatic Bearings with Shunt Injection

Abstract

Simultaneously increasing the load capacity and stiffness of aerostatic bearings is highly significant for ultraprecision machining. To achieve this goal, this study presents a novel method of using backflow channels to divert high-pressure air from the feed pocket to the low-pressure region of the clearance. Different shunt injections are coupled at the end part of the backflow channels. The effects of distribution and structure of the shunt injections are systematically analyzed. Moreover, the experimental data are used to compare and validate the numerically predicted characteristics. Results show that the backflow channels simultaneously enlarge the high-pressure region and improve the load capacity and stiffness of the bearings. The pressure difference between the inherent orifice shunt injections is still evident, which is not beneficial in exploring the potentialities of backflow channels in terms of increasing the load capacity and stiffness of bearings. High-pressure air can be stored under the pocket orifice shunt injection to decrease the pressure difference. Slot shunt injections shaped similar to ramparts can surround the high-pressure air, resulting in a more apparent effect on decreasing the pressure difference. Finally, the load capacity, stiffness, and mass flow rate of the backflow channel bearings are evidently larger than those of pocket orifice bearings. Thus, the growing demand of mass flow rate must also be considered when using backflow channel bearings for their larger load capacity and higher stiffness.