Author:

Keywords:

Science & Technology, Technology, Engineering, Mechanical, Transportation Science & Technology, Engineering, Transportation, ORIFICE-TYPE RESTRICTOR

Abstract:

The behaviour of aerostatic bearings is strongly influenced by the entrance flow effects nearby feeding sources. A basic understanding of these flow phenomena and accurate rediction of their relevant parameters are therefore essential in the design and optimisation process of any aerostatic bearing application. The subject matter of this paper has for long been the topic of extensive research. An overview of the different approaches found in literature shows mostly methods based on empirical formulas with a validity limited to the experimental conditions that produced them. The proposed solution method uses the technique of separation of variables to convert the boundary-layer equations describing the laminar channel flow into an initial value problem. This allows the exact calculation of the pressure profile from gap entrance up to the attainment of viscous flow. Knowledge of the pressure distribution near the gap entrance together with the mass flow rate leads to the determination of an expedient coefficient of discharge, allowing a more practical lumped parameter formulation. The results are compared with experimental data from various sources and the agreement is found to be remarkably good, indicating that a laminar flow model is adequate in characterising the entrance flow over a wide range of working parameters.