In order to provide some theoretical guideline for the structure design of the new type externally pressurized spherical air bearings,the static characteristics and the factors affecting the static characteristics of the air bearings were analyzed.A finite volume method was adopted to discretize the three-dimensional steady-state compressible Navier-Stokes equations,and a modified SIMPLE algorithm for compressible fluid was applied to solve the discretized governing equations.The pressure field and velocity field of the air bearings were obtained,and the factors and rules affecting the static characteristics were analyzed.The results show that the pressure of near air intakes can reach above 80% of air supply pressure,and there is a pressure steep fall around the air intakes.When the film thickness is greater than 20 μm,the bearing capacity rapidly decreases as film thickness increases.As the air supply pressure increases from 0.2 to 0.6 MPa,the maximum static stiffness increases by more than three times.The calculation method proposed well fits the general principle,which can be extended to the characteristic analysis of other air bearings.
In order to predict accurately the characteristics of supersonic flow in new type externally pressurized spherical air bearings under large bearing clearance and high air supply pressure,which could decrease their load carrying capacity and stability,a CFD-based analysis was introduced to solve the three-dimensional turbulent complete compressible air flow governing equations.The realizable κ-ε model was used as a turbulent closure.The supersonic flow field near air inlets was analyzed.The flow structures illustrate that the interaction exists between shock waves and boundary layer,and the flow separation is formed at the lower corner and the lower wall around the point of a maximum velocity.The numerical results show that the conversion from supersonic flow to subsonic flow in spherical air bearing occurs through a shock region(pseudo-shock),and the viscous boundary layer results in the flow separation and reverse flow near the shock.The calculation results basically agree with the corresponding experimental data.
