Miniature pressure transducers in compact water-cooled mounts are placed in hotter and more confined environments than previously possible. It quantitatively measures high frequency total pressure fluctuations resulting from rotating stall in an axial flow engine compressor

Armentrout, E. C.

English

NASA Technical Reports Server

October 1968	 Brief 68-10370 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
to encourage their commercial application. Copies are available to the public at 15 cents each 
from the Clearinghouse for Federal Scientific and Technical Information, Springfield, Virginia 22151. 
Cooled Miniature Pressure Transducers

Effective at High Temperatures 
Transducer Electrical Leads	 Reference Line 
Leads 
Coolant In	 Coolant Out 
AA
Weld 
.
	
io;::tProbe 
A 
Cooling Jac Coolant Passage
O-Ricl 
Gas Flow -.
Sensing Probe Holder 
A 
Cooling Jacket 
Sensino Probe 
A compact water-cooled mount for miniature pres-
sure transducers, which has been developed, permits 
locating the transducers in hotter and more confined 
environments than was previously possible. Compact-
ness was attained by utilizing pressure transducers ¼ 
inch in diameter by ¼ inch in length, with connect-
ing leads and reference pressure tube extending from 
the rear. Good response at frequencies to several hun-
dred Hertz is obtained by locating the pressure trans-
ducer near the mouth of the sensing probe. 
The cooling jacket comprises two concentric tubes. 
The inner tube is circular, with an inside diameter 
slightly larger than the outside diameter of the trans-
ducer. The outer tube is flattened to an elliptical cross 
section having a minor axis equal to the outside 
diameter of the inner tube. The two tubes are roll 
(continued irserleal) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the United States 
Government nor any person acting on behalf of the United States
Government assumes any liability resulting from the use of the 
information contained in this document, or warrants that such use 
will be free from privately owned rights.
https://ntrs.nasa.gov/search.jsp?R=19680000370 2020-03-12T05:52:30+00:00Z
welded or spot welded together at their line of con-
tact to provide parallel coolant supply and return 
passages. The coolant passages are connected at the 
inner or sensing end where the inside tube is reduced 
in diameter to fit around the transducer. The cooling 
jacket extends past the end of the transducer, so that 
the gas adjacent to the pressure diaphragm is also 
cooled. The transducer rests on a 0.010-inch-wide rim 
at the end of the inner tube. A thermocouple is 
attached to the transducer case. Transducer operating 
temperature is used to determine the coolant flow 
rate required and to correct the pressure measure-
ments. 
To assemble the device, the transducer is posi-
tioned in the inner tube which is then filled with an 
epoxy-type cement. This both seals the tube and 
prevents vibration of the leads, reference tube, and 
thermocouple. An alternate method uses 0-ring seals 
and a capped tube. The completed transducer mount 
is slipped into the sensing probe holder, and the sens-
ing probe is inserted into the inner end of the pressure 
transducer mount. Gas sealing is achieved with an 
0-ring. 
Initial testing at various ambient temperatures and 
flow rates showed excellent performance. As a result,
approximately 50 units of lengths ranging from 1.2 
to 9.4 inches were built, and are being used in the 
testing of advanced aircraft engines. Gas temperatures 
at the probe locations range upward of 1000° F. 
Notes: 
1. This instrumentation made it possible, for the first 
time, to measure quantitatively high-frequency 
total pressure fluctuations resulting from rotating 
stall in an axial flow engine compressor. Measure-
ments have determined the initial location of stall 
and followed the progression of a stall through the 
remaining stages of the compressor. 
2. Details may be obtained from: 
Technology Utilization Officer 
Lewis Research Center 
21000 Brookpark Road 
Cleveland, Ohio 44135 
Reference: B68-10370 
Patent status: 
No patent action is contemplated by NASA. 
Source: E. C. Armentrout 
(LEW-10401) 
Brief 10370
	 Category 01


Cooled miniature pressure transducers effective at high temperatures

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