Abstract
Aerostatic bearings are attractive, with minimal friction losses, high durability, and environmental friendliness. However, such designs have a number of disadvantages, including low load-bearing capacity and high compliance due to high air compressibility and limited injection pressure. The article proposes a double-row aerostatic journal bearing with an external combined throttling system and longitudinal microgrooves in the inter-row zone. It is hypothesized that the use of microgrooves will reduce the circumferential flows of compressed air, as a result of which the compliance should decrease and the bearing capacity should increase. To test the hypothesis, we carried out the mathematical modeling, calculations, and theoretical study of stationary operation modes of the bearing for small shaft eccentricities in the vicinity of the central equilibrium position of the shaft and bearing capacity for arbitrary eccentricities. Formulas were obtained for the numerical evaluation of compliance for bearings with a smooth bushing surface and with longitudinal microgrooves. Iterative finite-difference methods for evaluating the fields of the squared pressure are proposed, on the basis of which the load capacity of the bearings is calculated. Experimental verification of the bearing’s theoretical characteristics was carried out, which showed satisfactory agreement between the compared data. The study of the compliance and load capacity of a microgroove bearing yielded impressive results. We show that the positive effect from the application of the improvement begins to manifest itself already at four microgrooves; the effect becomes significant at six microgrooves, and at twelve or more microgrooves, the circumferential flows in the bearing gap practically disappear; therefore, the bearing characteristics can be calculated on the basis of one-dimensional models of air lubrication longitudinal flow. Calculations have shown that for a length of L = 1, the maximum load capacity of a bearing with microgrooves is 1.5 times higher than that of a conventional bearing; for L ≥ 1.5, the bearing capacity increases twice or more. The result obtained allows us to recommend the proposed improvement for practical use in order to increase the load capacity of aerostatic journal bearings significantly.
Highlights
There has been an increased interest in the use of aerostatic bearings in machines, in machine tools and instruments
Aerostatic bearings have a number of disadvantages, the mos dominant of which are low load-bearing capacity, high compliance, an increased tendency for instability
The first two drawbacks are explaine2dof 2b1y the lim injection pressure, and the last drawback is determined by the high compressibility o even in microvolumes [17,18]
Summary
There has been an increased interest in the use of aerostatic bearings in machines, in machine tools and instruments. Aerostatic bearings are attractive because of their main advantages, namely, low air viscosity, minimal friction losses, and, as a consequence, high durability and environmental friendliness [13,14,15,16]. Sci. 2021, 11, 5714 diaphragms 5, where resistance in a stable bearing should be at approximately an order of magnitude lower than the resistance of the feeders 4 This ensures maximum stability and optimal dynamic quality [18]. We will investigate the characteristics under the assumption that the axes of the bushing and bearing are parallel
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