Report presents practical information for incorporating particle impact protection features and average total pressure measurement into probe design while optimizing probe transient response. Computer program calculates probe response, based on Bergh-Tijdeman equation

Englund, D. R.

Nyland, T. W.

English

NASA Technical Reports Server

September 1971	 Brief 71-10374 
S NASA TECH BRIEF
	
A £ 
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 aubscription 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. 
Dynamics of Short Pressure Probes 
The problem: 
In studies of stall propagation through an engine, 
several transient total pressure probes are located 
in the inlet and in between the engine compressor 
stages. The probes have internally mounted miniature 
pressure transducers connected to short total-head 
tubes. To protect the transducer from damage by 
entrained particles in the airstream, either the trans-
ducers are mounted at right angles to the axis of the 
probe, or offsets or baffles are included in the internal 
geometry of the probe. The problem involves in-
corporating the particle impact protection features 
and the average total pressure measurement into 
the probe design without degrading the transient 
response of the meauring system. 
The solution: 
An experimental program was conducted, and the 
report on that program presents practical design 
information for optimizing the transient response 
of the probes. A computer program calculates the 
probe response, based on the Bergh-Tijdeman equa-
tion. 
How it's done: 
The frequency response and the frequency response 
variations resulting from probe geometry variations 
were measured for probes 2.54 cm long with i.d.'s
of 0.325 and 0.160 cm. Geometrical variations were 
designed to permit simultaneous measurement of 
time-average pressure and to protect the pressure 
transducer from particles entrained in the airstream. 
For comparison, a computer program was used to 
calculate the frequency response of a multi-tube 
volume system, using the Iberall and Bergh-Tijdeman 
equations. Measured frequency response showed 
good correlation with predictions made by the com-
puter program. 
Notes: 
1. This program is written in FORTRAN IV for use 
on the IBM-7094 computer. 
2. Requests for further information should be 
directed to: 
COSMIC 
112 Barrow Hall 
University of Georgia 
Athens, Georgia 30601 
Reference: B71-10374 
Patent status: 
No patent action is contemplated by NASA. 
Source: T. W. Nyland, D. R. Englund, and

R. C. Anderson
Lewis Research Center

(LEW-1 1293) 
Category 09 
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.
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Dynamics of short pressure probes

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