Curves span wide range of operating conditions, including: lubricant compressibility numbers from 0 to 80, bearing length-to-diameter ratios from 1/4 to 2, and either rotating or stationary grooved members

Fleming, D. P.

Hamrock, B. J.

English

NASA Technical Reports Server

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May 1975	 B75-10063 
S NASA TECH BRIEF 
Lewis Research Center 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Design Curves for Optimizing Stability 
of Herringbone-Grooved Journal Bearings 
. 
S
Design curves have been developed for optimizing 
herringbone-grooved bearing design parameters to maxi-
mize bearing stability and load bearing capacity. The 
curves span a wide range of operating conditions, in-
cluding: lubricant compressibility numbers from 0 (in-
compressible) to 80, bearing length-to-diameter ratios 
from 14 to 2, and either rotating or stationary grooved 
members. 
The herringbone-grooved journal bearing was investi-
gated in quest of a bearing which would overcome the two 
problems of self-excited whirl instability and load 
capacity. The objective of this study was to determine 
groove parameters which would maximize the stability of 
the bearing, or the resistance to self-excited whirl. 
More than any other factors, self-excited whirl in-
stability and low load capacity limit the usefulness of 
gas-lubricated self-acting journal bearings. The whirl 
problem is the tendency of the journal center to orbit the 
bearing center at an angular speed less than or equal to 
half that of the journal about its own center. In many 
cases, the whirl amplitude is large enough to cause 
destructive contact of the bearing surfaces. 
The low load capacity of self-acting gas-lubricated 
journal bearings is also a serious concern in many 
applications, largely because of the low viscosity of gases. 
Also, unlike a liquid lubricant, a gaseous lubricant changes 
its density as it passes through the bearing. This so-called 
compressibility effect results in a "terminal" load condi-
tion. That is, the load capacity does not increase 
indefinitely with speed, but quickly approaches a fixed 
value. 
The figure shows the bearing studied. The bearing has 
angled, shallow grooves in the journal surface. The grooves 
can be partial as shown or extend the complete length of 
the bearing. Also, the grooves can be placed in the 
rotating or non-rotating surface. The purpose of these 
grooves is to pump fluid toward the center of the bearing 
and thereby increase the lubricant pressure in the bearing. 
This self-pressurization can increase the load capacity over 
that of a smooth bearing; it is also responsible for the 
good stability of the herringbone bearing. The herring-
bone bearing is unidirectional; that is, it pumps inwardly 
for only one direction of rotation.
\ 
From the design curves, optimum groove configura-
tions were determined to maximize the stability of 
herringbone-grooved journal bearings. 
Compared with bearings optimized to maximize load 
capacity, bearings optimized for stability (.1) allow a 
thousandfold increase in bearing-supported mass in some 
cases before onset of instability (the most pronounced 
increases are for bearings with small length-to-diameter 
ratios operating at high compressibility numbers), and (2) 
lose no more than 77 percent of their load capacity in any 
case studied. Stability is much greater when the grooved 
member rotates. 
Notes: 
- These design curves should be of interest to manu-
facturers and users of bearings and general rotary 
equipment. 
2. Further information is available in the following 
report: 
NASA TN-D-7803 (N74-34888), Optimization of 
Self-Acting Herringbone-Grooved Journal Bearings 
for Maximum Stability
(continued overle ,dt 
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Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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Copies may be obtained at cost from: 
Aerospace Research Applications Center 
Indiana University 
400 East Seventh Street 
Bloomington, Indiana 47401 
Telephone: 812-337-7833 
Reference: B75-10063 
3. Specific technical questions may be directed to: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B75-10063 
Source: D.P. Fleming and B.J. Hamrock 
Lewis Research Center
(LEW-12442)
S 
B75-10063	 Category 06


Design curves for optimizing stability of herringbone-grooved journal bearings

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