Performance comparison between aerostatic bearings with orifice and porous restrictors based on parameter optimization

ABSTRACT

The performance of aerostatic bearing mainly depends on the throttling effect of its restrictor. The orifice and porous material are the most common restrictors, which have their own advantages and suitable working conditions. At present, there are many studies on the performance comparison of bearings with the two types of restrictors, but almost all of them are carried out on the premise of the determined restrictor parameters, the results of the comparison will vary greatly due to the different restrictor parameters. In order to avoid this problem, the CFD software was used to simulate the flow field in the film based on the theory of gas lubrication. The dynamic and static characteristics of the two kinds of bearings were obtained, and the optimal restrictor parameters were optimized. Based on parameter optimization, the bearing performances were analysed and compared. The study reveals that for the single-restrictor aerostatic bearing, the use of porous restrictor can make the bearing obtain superior dynamic and static performances; For the multi-restrictor aerostatic bearing, the use of the orifice restrictor can make the bearing obtain quite high stiffness, but the use of the porous restrictor can enable the bearing to achieve a considerably high load capacity.

KEYWORDS:

• Restrictor
• aerostatic bearings
• parameter optimization
• CFD

Nomenclature

${\mathrm{P}}_{\mathrm{s}}$	=	the supply pressure of aerostatic bearings;
Pa	=	the ambient pressure of bearings;
Pd	=	the pressure of the outlet of restrictors;
$\rho$	=	the density of the gas in the gas film;
${\rho }_{\mathrm{a}}$	=	the gas density of the ambient environment;
c0	=	the discharge coefficient of nozzle;
s	=	the throttling area, and s = πdh;
$\psi$	=	the nozzle velocity coefficient;
h	=	the thickness of gas film;
k	=	the adiabatic coefficient of the gas;
a	=	the diameter of gas chamber;
d	=	the diameter of orifice;
b	=	the diameter of orifice bearing;
${\mathrm{m}}_1$	=	the gas mass flow out of the orifice bearing;
${\mathrm{m}}_2$	=	the gas massflow flowing into the orifice bearing;
R	=	the gas constant;
T	=	the absolute temperature of gas;
g	=	the acceleration of gravity;
d1	=	the diameter of porous cylinder;
H	=	the thickness of porous cylinder;
d2	=	the diameter of porous bearing;
${\mathrm{Q}}_1$	=	the gas massflow flowing into the porous bearing;
${\mathrm{Q}}_2$	=	the gas mass flow out of the orifice bearing;
$\mu$	=	the dynamic viscosity coefficient of gas;
${\mathrm{p}}_{\mathrm{i}}$	=	the pressure of the fluid in the porous material;
${\mathrm{w}}_{\mathrm{z}}$	=	the axial velocity of gas inside the porous material;
$\phi$	=	the viscous resistance coefficient of the material;
M	=	the mass of gas consumption of bearings;
α	=	the energy consumption efficiency;

Acknowledgments

I would like to thank my student Liaoyuan Wang and colleague Shengze Wang for their efforts in this paper.

Disclosure statement

No potential conflict of interest was reported by the authors.