Design of thrust balancer minimizes leakage bypass and obviates need for conventional thrust balancer. System allows operation at low flow rates and high thrust capacity at cryogenic temperatures and high pressures

Buckmann, P. S.

English

NASA Technical Reports Server

June 1972	 '1372-10264 
NASA TECH BRIEF 
Marshall Space Flight 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. 
Turbopump Radial and Axial Rotor Support System 
A turbopump rotor bearing which allows the rotor to 
operate above the first two lateral critical speeds and a 
self-compensating thrust balancer with a capacity of 0 to 
200,000 lbs. (0 to 27,600 N) of thrust have been devel-
oped for operation at cryogenic temperatures and high 
pressures. The turbopump rotor support system has two 
sets of preloaded angular contact bearings, one set near 
each end of the turbopump, mounted in radially flexible 
springs with predetermined stiffness, for lateral critical 
speed control. One set of bearings is free to move axially, 
while the other set is restricted in one direction by a 
hard stop and in the other direction by a spring force 
towards pump suction. The rolling element bearings 
absorb transient axial loads. 
The thrust balancer consists of a thrust runner, a 
variable flow-area inner seal, several fixed area orifices, 
and a self-aligning fixed area face seal which forms the 
outer seal. High pressure liquid is fed to the shallow 
cavity between the sills through both the face seal and 
the orifices. Flow continuity through these fixed areas 
and that of the inner sill results in a pressure profile over 
the cavity and a corresponding axial force. If this force 
is not in equilibrium with the other axial loads, the rotor 
will be displaced in a direction opposite to the force un-
balance. If the force generated by the thrust balancer is 
insufficient to equalize the axial rotor forces, the rotor 
will move in a direction to reduce the inner sill clear-
ance. The reduced clearance results in a reduction of the 
inner sill flow area, which then causes the cavity pressure 
to increase so as to maintain flow continuity. 
The action of the thrust balancer is, therefore, self-
compensating in that the rotor system will be displaced
axially until the cavity pressure results in thrust equi-
librium. 
The self-aligning face-seal feature of the design is 
unique due to the "floating" characteristic being tolerant 
of impeller housing distortion and therefore permitting 
close clearance with reduced flow. This is extremely 
important because all leakage or parasitic flows reduce 
pump efficiency and eventually result in increased engine 
weight. The unique design of the thrust balancer mini-
mizes leakage bypass and obviates the need for the con-
ventional thrust balancer and allows operation at low 
flow rates and high thrust capacity. 
Notes: 
1. Information concerning this innovation may be of 
interest to turbomachinery designers and manufac-
turers in general and to pump designers and manu-
facturers in particular. 
2. Requests for further information may be directed to: 
Technology Utilization Officer 
Marshall Space Flight Center 
Code A&TS-TU 
Huntsville, Alabama 35812 
Reference: B72-10264 
Patent status: 
No patent action is contemplated by NASA. 
Source: P. S. Buckmann of

Aerojet Liquid Rocket Company

under contract to
Marshall Space Flight Center

(MFS .2 1495) 
Category 07 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
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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Turbopump radial and axial rotor support system

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