Page 109 - The Tribology Handbook

AI9 Gas bearings

Externally pressurised gas thrust
bearings
There are two main types of externally pressurised gas CENTRAL RECESS ANNULAR BEARING
thrust bearings. These are the central recess and annular BEARING
bearing as shown on the right. The central recess bearing
is fed from a central orifice, while the annular bearing is
fed from a ring of orifices. The stiffness of these bearings
varies with clearance as shown below.

-------
W \... OPERATING POSITION STIFFNESS FOR

Orifice dia. d * for a central recess bearing with clearance
ho = 25 pm (0.001 in) for air, 15"C, ambient pressure
h CLEARANCE 1 bar, is given below.
GENERAL LOAD CLEARANCE CHARACTERISTIC

1.6
0.060
All design data are given for operation at the position
of maximum stiffness and are approximate. 1.4
Load carried W = Ci. arz Pf E 1.2 0.050
E
where Pf = supply pressure (gauge)
E- 1.0 0.040
Stiffness X = 1.42 W/h for pocketed orifices 9
a
C
J 0.8 .-
-
U - 0.030 *=-
0.6
D
0.; 0.020
0.4
0.01 0
0.C 0.2
m
m
W CENTRAL RECESS TYPE 0
z 1 2 3 4 5 6 7
u 0.5
u;
c
m
$ 0.4
2 For other values of clearance h new orifice dia. ;
I-
Q d = d* (%)
hs
-2
u z' 0.: ANNULAR TYPE
w
u
LL For annular bearing with N pocketed orifices;
U
W 0.i
0
u
0
Q
5 0.1 For annular bearing with k-'unpocketed orifices;
d*'.h2
d=-
, Nhi
C I I I I
2 3 4 5 6 7 W
Vr, and stiffness K = 0.95 -
h
A19.2