The primary goal of the Bearing Deflectometer Investigation was to gain experience in the use of fiber optic displacement probe technology for bearing health monitoring in a liquid hydrogen turbo pump. The work specified in this Task Order was conducted in conjunction with Air Force Rocket Propulsion Laboratory Contract F04611-86-C-0010. APD conducted the analysis and design coordination to provide a displacement probe design compatible with the XLR-134 liquid hydrogen turbo pump assembly (TPA). Specifications and requirements of the bearing deflectometer were established working with Mechanical Technology Instruments, Inc. (MTI). The TPA design accommodated positioning of the probe to measure outer race cyclic deflections of the pump inlet bearing. The fiber optic sensor was installed as required in the TPA and sensor output was recorded during the TPA testing. Data review indicated that no bearing deflection signature could be differentiated from the inherent system noise. Alternate sensor installations were not investigated, but might yield different results

Diepenbrock, R. T.

Millis, M. G.

Reimer, B. L.

English

NASA Technical Reports Server

,//, &-Q-5
E- '7714
NASA Technical Memorandum 106085
OTV Bearing Deflection Investigation
B.L. Reimer and R.T. Diepenbrock
Aerojet Propulsion Division
Sacramento, California
and
M.G. Millis
Lewis Research Center
Cleveland, Ohio
April 1993
NASA
https://ntrs.nasa.gov/search.jsp?R=19930013805 2020-03-17T06:17:21+00:00Z
OTV BEARING DEFLECTION INVESTIGATION
B.L. Reimer and R.T. Diepenrock
Aerojet Prpulsion Division
Sacarmento, California 95813
and
M.G. Millis
National Aeronautics and Space Administration
Lewis Research Center
Cleveland, Ohio 44135
The primary goal of the Bearing Deflectometer Investigation was to gain experience in
the use of fiber optic displacement probe technology for bearing health monitoring in a liquid
hydrogen trubopump. The work specified in this Task Order was conducted in conjunction
with Air Force Rocket Propulsion Laboratory Contract F04611-86-C-0010. APD conducted the
analysis and design coordination to provide a displacement probe design compatible with the
XLR-134 liquid hydrogen turbopump assembly (TPA). Specifications and requirements of the
bearing deflectometer were established working with Mechanical technology Instruments, Inc.
(MTI). The TPA design accommodated positioning of the probe to measure outer race cyclic
deflections of the pump inlet bearing. The fiber optic sensor was installed as required in the
TPA and sensor output was recorded during the TPA testing. Data review indicated that no
bearing deflection signature could be differentiated from the inherent system noise. Alternate
sensor installations were not investigated, but might yield different results.
i
1.0 INTRODUCTION/ SUMMARY
Many space transportation propulsion system designs utilize turbomachinery with
rolling element bearings. Extreme radial and axial load demands placed upon the
bearings often result in their being the key system life determinator. Providing
improved means of monitoring bearing life is essential to the establishment of propul-
sion system performance, reliability and maintainence requirements. In the interest of
the aforementioned goal, the NASA LeRC developed the Bearing Deflectometer
Investigation as Task Order E.5 of the Orbit Transfer Rocket Engine Technology
Program. The task order called for the use of an MTI Fotonic sensor, a fiber optics
proximity monitoring instrument. The instrument would be installed in a liquid
hydrogen turbopump to better understand it's potential for bearing health monitoring
in a cryogenic environment..
Subtask 1 (Design), of the investigation task order called for incorporating the MTI
1000 Fotonic sensor into the design of the XLR-134 liquid hydrogen turbopump devel-
oped under the Air Force Rocket Propulsion Laboratory contract F04611-86-C-0010. The
turbopump housing design was made to accommodate the sensor probe such that it
would monitor the outside diameter of the outer bearing race of the single pump inlet
bearing. MTI sensors had some history of use in monitoring outer bearing race deflec-
tions in turbomachinery and the Task E.5 investigation design intent was to further the
study by monitoring bearing deflection patterns in the cryogenic environment of the
XLR-134 hydrogen turbopump.
Subtask 2 (Test) of the task order called for installation of the probe into the tur-
bopump for check-out, monitoring and recording of the displacement probe output
during the turbopump test. Subsequent to the test, the resulting data would be reduced
for evaluation and reporting.
The displacement probe installed for testing was the MTI model 3812, selected for
it's high sensitivity. The installation gap and respective output voltage were set for the
displacement probe response to be on the forward slope of the probe calibration curve.
It was determined that once the system reached the cryogenic operating temperature
that the probe to outer race gap would increase but that the resulting operating output
would still correspond to the desired front slope portion of the calibration curve.
1.0, Introduction/ Summary (cont.)
Analysis of the test data indicated that while the sensor output was within the
desire range for optimum displacement sensitivity, it was not possible to establish the
expected bearing trace or signature. The ambient probe gap was altered between tests
in order to acquire data over a slightly wider operating range. The bearing signatures
which are vital to the establishment of a bearing health trend could not be differentiated
from the inherent system noise.
The test plan for the XLR-134 fuel turbopump called for extensive testing at nomi-
nal speed (74K RPM) to verify it's long life design. In fact, the test program was termi-
nated short of it's intended goals due to lack of follow-on contract support. As a result,
there was not sufficient test run time available to to alter the set-up of the MTI 1000
Fotonic sensor and test system to achieve more positive results.
2.0 EXPERIMENT DESIGN DETAILS
2.1 BEARING DEFLECTOMETER
The NASA LeRC provided the instrument based on previous experience with
the design and a desire to gain further knowledge of it's range of application. The
Model 1000 Fotonic sensor is manufactured by Mechanical Technology Inc. (MTI) and
utilizes a fiber optic probe system which is designed to perform non-contact displace-
ment/vibration and surface condition measurements. The system utilizes probe tip
designs incorporating optical fibers with various combinations and orientations of
sending and receiving fibers depending on the application, wide range or high sensitiv-
ity.
Two different probe tip designs were ordered for the test series. Each of the
probes had an outer tip diameter of 1/8 in. and utilized a specially designed safety bar-
rier in the cable sheath to keep hydrogen gas from finding it's way from the inner tur-
bopump housing area to the sensor signal conditioner. One of the probes designs (MTI-
3812) utilizes a random pattern of sending  and receiving fibers for high sensitivity. The
other probe (MTI-3814) is a hemispherical design and was acquired for the purposes of
providing a broader range option. The probe tip length requirement was based on that
2.1, Bearing Deflectometer (cont.)
which would allow the tip to penetrate through the turbopump housing and accommo-
date the special fitting to hold the probe in place. Figure 1 shows the sketch that was
used for design definition and fabrication.
2.2 TURBOPUMP AND PROBE
Special design considerations were required to incorporate the MTI probe
into the XLR-134 turbopump. Figure 2 shows a cross section of the turbopump with the
probe installed. Modifications to the baseline pump design included adding a raised
boss to the outside of the housing at the location of the single pump inlet bearing.
Machined into the boss, an MS 33649 port provided for acceptance of a fitting which
incorporates a standard AN style union on the boss side and a 1/ 8 in. Swagelok tube
fitting on the probe entrance end. The outer and inner pump housings were match
machined to accept the probe tip. The clearance between the inner housing and probe
tip end was minimal to restrict internal flow losses in the pump.
3.0 TEST DETAILS
3.1 HARDWARE SET-UP
Figure 3 shows the XLR-134 turbopump on the test stand with the MTI dis-
placement probe installed. In order to avoid damage to the probe optical fibers, the
swage fitting utilized a composition TFE and glass fiber ferrel.
Throughout the testing, the ferrel provided a positive means for holding the
probe tip while effectively sealing the pump housing at the interface. Figure 4 shows
the MTI 1000 signal conditioning unit installed in the test bay. The unit was installed in
a fire safety box during testing  due to the proximity of hydrogen in the area of the test
stand.
3.2 TEST SET-UP
The probe with the random fiber pattern (MTI-3812) was selected for use
based on it's high sensitivity and the feeling that any outer race deformation resulting
from ball bearing passing loads would be slight. Two different probe tip gaps and their
resulting voltage output were utilized during the course of the testing. Due to the
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3.2, Test Set-Up (cont.)
nature of the hardware, it was not possible to physically measure the probe tip to
bearing race gap. In each case the gap was simply established by using the probe cali-
bration curve and correlating the output voltage to the indicated gap. Frequency
response was based upon the expected 1233 Hz signal for rotating assembly unbalance
and radial play and 3.7K to 6.2K Hz ball passing frequency. Ball passing frequency is a
function of the bearing axial load. The expected frequency response was based upon a
planned turbopump nominal speed of 74K RPM. Calibration and frequency response
curves were furnished with each of the probe tip fiber configurations and are included
in Appendix A along with probe specifications.. The following table indicates the set-
up conditions for the probe and signal conditioner:
Voltage Voltage Filter Datum Intensity Displacement/
Ambient Cryo Setting Shift Setting Vibration
2.1 .73 2 10 X.1 K Read
4.4 2.0 2 10 X1 K Read
As with all of the turbopump test instrumentation, the output from the probe
was remotely monitored from the test control room. A visual reading of the output
voltage was available at all times and signal was recorded on FM tape. Due to the
nature of the test it was not possible to alter the set-up while the pump was "chilled in"
or running.
4.0 DATA ANALYSIS
The test data which was recorded on FM tape was given to the Dynamics Analysis
group. They were directed to look at specific channels of the tape to establish a period
during which the turbopump was operating at it's nominal rotational speed after which
they could look at the displacement sensor data. They were told to look for any signal
in the 1.2K to 6.2 Hz frequency domain. They utilized a dynamic signal analyzer to ana-
lyze at the data. The results of their analysis indicated that there was no recorded data
representative of shaft unbalance, axial play or outer race deformation due to ball
passing loads.
5.0 CONCLUSION
The XLR-134 turbopump test plan was established to demonstrate long life opera-
tion of the pump assembly. The actual turbopump test time achieved was only a frac-
tion of that which was planned due to limited funding.. As a result, there was not suffi-
cient time available to iterate between reconfiguration of the MTI displacement probe
set-up and dynamics analysis until more positive results were achieved.
9
APPENDIX A
PROBE DATA
A-1
TABLE A-1
MTI FOTONIC PROBE SPECIFICATIONS
MTI-3812 MTI-3814
Probe tip diameter 0.125 in. 0.125 in.
Frequency response 70 KHz (-3 db) 70 KHz (-3db)
Output signal ripple 20 mV p-p 20 mV p-p
Resolution M of range) 0.2 dynamic 0.3 dynamic
Resolution M of range) 0.05 static 0.1 static
Sensitivity 0.6 µ in./mV 7.0 µ in./mV
Linear range 0.004 in. 0.030 in.
Standoff 0.0025 in. 0.25 in.
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1. AGENCY USE ONLY (Leave blank) 2- REPORT DATE 3. REPORT TYPE AND DATES COVERED
April 1993 Technical Memorandum
4. TITLE AND SUBTITLE 5. FUNDING NUMBERS
OTV Bearing Deflection Investigation
WU-593-12-11
6. AUTHOR(S)
B.L. Reimer, R.T. Diepenbrock, and M.G. Millis
7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION
REPORT NUMBER
Aerojet Propulsion Division
P.O. Box 13222 E-7714
Sacramento, California 95813-6000
9. SPONSORING/MONITORING AGENCY NAMES(S) AND ADDRESS(ES) 10. SPONSORING/MONITORING
AGENCY REPORT NUMBER
National Aeronautics and Space Administration
Lewis Research Center NASA TM-106085
Cleveland, Ohio 44135-3191
11. SUPPLEMENTARY NOTES
B.L. Reimer and R.T. Diepenbrock, Aerojet Propulsion Division, P.O. Box 13222, Sacramento, California 95813-0000.
M.G. Millis, NASA Lewis Research Center. Responsible person, M.G. Millis, (216) 977-7535.
12a. DISTRIBUTION/AVAILABILITY STATEMENT 121b. DISTRIBUTION CODE
Unclassified -Unlimited
Subject Categories 18, 19, 20, and 35
13. ABSTRACT (Maximum 200 words)
The primary goal of the Bearing Deflectometer Investigation was to gain experience in the use of fiber optic displacement
probe technology for bearing health monitoring in a liquid hydrogen turbopump. The work specified in this Task Order
was conducted in conjunction with Air Force Rocket Propulsion Laboratory Contract F04611-86—C-0010. APD con-
ducted the analysis and design coordination to provide a displacement probe design compatible with the XLR-134 liquid
hydrogen turbopump assembly (TPA). Specifications and requirements of the bearing deflectometer were established
working with Mechanical Technology Instruments, Inc. (MTI). The TPA design accommodated positioning of the probe
to measure outer race cyclic deflections of the pump inlet bearing. The fiber optic sensor was installed as required in the
TPA and sensor output was recorded during the TPA testing. Data review indicated that no bearing deflection signature
could be differentiated from the inherent system noise. Alternate sensor installations were not investigated, but might
yield different results.
14- SUBJECT TERMS 15. NUMBER OF PAGES
'	 18
Fiber optics; Transducers; Turbine instruments; Sensors 16- PRICE CODE
A03
17_ SECURITY CLASSIFICATION 18- SECURITY CLASSIFICATION 19. SECURITY CLASSIFICATION 20. LIMITATION OF ABSTRACT
OF REPORT OF THIS PAGE OF ABSTRACT
Unclassified Unclassified Unclassified
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	 Standard Form 298 (Rev. 2-89)
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