High-Thrust Aerostatic Bearing Design Through Transient Perturbation Modeling With Numerical Validation

Abstract

A simple perturbation flow model is formulated and validated by a rigorous computational fluid dynamics (CFD) study for designing a counterbalanced vertical-axis aerostatic thrust bearing. The flow model of the orifice at the entry of the stator manifold involves natural transition between the choked and free flows. While the air distribution network of holes in the stator and one air gap at the inner radius of the stator constitute the fixed part, the variable part is comprised of two air gaps at the top and bottom of the stator interconnected by the inner air gaps. The top and the inner gaps receive air by a circular array of holes. While the basic flow of the perturbation model is taken as steady corresponding to fixed air gaps, the transient effect is captured by a squeezing flow due to the variations of the top and bottom gaps. The overall flow including that in the network is assumed as compressible and isothermal. This model has been validated through a transient axisymmetric CFD study using dynamic meshing and the coupled lifting dynamics of the payload. The validated model has been used to find the appropriate counterbalancing, the orifice diameter, the air gap sizes, and the location of the air holes feeding the top gap. This clearly shows the worth of the model for carrying out an extensive design analysis that would have been very costly and even unachievable for small gaps that would occur during system transients.