Optimization of restrictor parameters and static characteristics study on orifice type hydrostatic thrust bearing

Gas bearings play a crucial role in maintaining the precision of ultra-precision machine tools. However, the bearing capacity is inferior to that of rolling bearings. The bearing capacity of gas bearings is directly influenced by restrictor structural parameters. To clarify the combined effect of restrictor structural parameters on the static bearing capacity of gas bearings and enhance the bearing capacity. The orthogonal test method was used to investigate the impact of various combinations of parameter levels (e.g. diameter of orifices d1, thickness of gas film h1, diameter d2 of pressure-equalizing groove (PEG), and PEG depth h2 on the static load carrying capacity of the bearings). The load-carrying capacity (LCC) and mass flow rate (MFR) were selected as the experimental indicators. Results showed that gas film thickness, orifice diameter, PEG diameter and PEG depth dominated LCC. Additionally, it was observed that diameter of orifices has the most significant impact on MFR, followed by thickness of gas film, PEG diameter, and PEG depth having the smallest influence on MFR. LCC serves as a critical manifestation of the static bearing capacity of bearings. However, this increase in LCC unavoidably resulted in higher gas consumption, leading to an elevated MFR. Consequently, the structural parameters of restrictor were optimized based on the principle of optimal LCC, while also ensuring that there was no significant rise in MFR. The optimized parameter combinations were thickness of gas film h1=0.01 mm, diameter of orifices d1=0.25 mm, PEG diameter d2=5 mm, and PEG depth h2=0.07 mm. This study can contribute to a profound understanding of the nonlinear dynamic mechanism and structural optimization design application of air bearing.