When test valve is actuated, piston is moved by pressurized fluid, and displacement is monitored by electro-optical tracking system and recorded by oscilloscope camera. Electro-optical monitor produces output voltage proportional to displacement of piston

Pearson, D. J.

English

NASA Technical Reports Server

• November 1974	 B74-10217 
NASA TECH BRIEF 
Ames 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. 
System for Measuring Transients in Fluid Flow 
The problem: 
To measure fluid-flow transients in small fast-
acting electrically actuated valves so that performance 
of the valves can be determined as a function of volt-
age, pressure, temperature, presence of particulates, 
number of actuation cycles, and time. 
The solution: 
Place a piston in the flow stream and measure its 
displacement with an electro-optical monitor.
3, closing valve 5, and opening valve 6. Gas bubbles 
in the system will be indicated by anomalous piston 
motion during the repositioning process. 
Pressure Gage	
Inert 
Gas 
Bladder	
Supply 
Accumulator
Gas 
Fluid 
.
How it's done: 
The schematic diagram illustrates the valve test 
station. The piston, placed in precision-bore trans-
parent tubing (2-mm I.D.) before the start of a test, 
may be an immiscible opaque-dyed fluid of about the 
same density as the test fluid, or a solid which will 
form a detectable, contrasting interface with a trans-
parent test fluid; alternatively, the test fluid may be 
opaque and the piston transparent. At the start of a 
test, the piston is located near the left end of the flow 
tube; valves 2 and 3 are open, and 4, 5, and 6 are 
closed. The needle valve is almost completely open; 
as it is turned, its stem displaces a varying amount of 
fluid so that it acts as a vernier control for the initial 
position of the piston. When the test valve is actuated, 
the piston is moved by the pressurized fluid, and the 
displacement is monitored by an electro-optical 
tracking system and recorded by an oscilloscope 
camera. 
After a test run, valve 5 is opened and valve 3 is 
closed; the piston is moved back to its original posi-
tion by. manipulating valve 4. Fine adjustments of 
piston position are made with the needle valve while 
observing a dc voltmeter attached to the output of 
the electro-optical tracker. If the piston is moved too 
far to the left, it can be repositioned by opening valve
Vent	 Vent
To Valve 
Driver 
V-2	 V-4	 Valve
	 Needle Valve
Test
Vent 
Piston)	
\ Flow 
Tube
V-5 
The piston is magnified to form a 25-mm diameter 
by 25-mm long image by a system composed of three 
cylindrical lenses, one of which is the thick-walled 
glass flow tube itself. This system provides magnifica-
tion only in the direction transverse to the motion of 
the piston, and prevents the tracker from losing the 
thin piston without introducing errors in measure-
ments of the piston's position. 
The electro-optical monitor produces an output 
voltage proportional to the displacement of the piston. 
The photograph of the oscilloscope display charac-
terizes the transient flow properties of the valve since 
the displacement voltage is directly proportional to 
the flow volume. An electronic differentiator can be 
L (continued overleaf) 
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.
https://ntrs.nasa.gov/search.jsp?R=19740000217 2020-03-17T13:56:02+00:00Z
used to convert volume—time signals to flow-rate 
signals, which are not readily relatable to the per-
formance of the valve and actuator; extremely small 
fluid flow rates can be measured. 
Note: 
Requests for further information may be directed 
to:
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: TSP 74-10217
Patent status: 
NASA has decided not to apply for a patent. 
Source: Durk J. Pearson of
TRW Systems Group, TRW, Inc. 
under contract to
Ames Research Center 
(ARC-10852) 
B74-10217	 Category 03


System for measuring transients in fluid flow

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