Turbine flowmeters are calibrated dynamically by means of frequency response tests, provided small perturbations are used. The indicated flow is related to the actual flow by a first order lag function. This lag function is completely defined by the breakpoint frequency which is directly proportional to mean flow rate

Stevens, G. H.

English

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December 1969	 Brief 69-10764 
NASA TECH BRIEF 
NASA Tech Briefs are issued to summarize specific innovations derived from the U.S. space program, 
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Dynamic Calibration of Turbine Flowmeters
Vent to 
Atmosphere 
Air Supply 
Accumulator
 Throttle-valve	 Sinusoidal 
Control Apparatus	 Command
Pressure 
Collection  
and Storage	 wmeter	
Signal  
Tank
Drive Gear
	 Throttle	
L......1... 	 Sharp-edged Flow Pump	 Valve	 Signal	 Orifice 
Return Gear Pump 
Dynamic Calibration Schematic
.
Exhaust 
Reservoir 
Spillway 
It has been found that turbine flowmeters can be 
calibrated dynamically by means of frequency-
response tests, provided small perturbations are 
used. The indicated flow is related to the actual flow 
by a first-order lag function: 
W, 
W ,
=
1 +-; 
where W 1
 is the perturbation mass flow indicated 
by the flowmeter, W' is the perturbation actual mass 
flow, f is the perturbation frequency and f 0
 is the 
breakpoint frequency of the flowmeter. This lag func-
tion is completely defined by the breakpoint frequency 
which is directly proportional to mean flow rate 
f0 = CW
where W is the mean value of actual mass flow and 
C is an experimentally determined constant. 
Knowledge of the value of C is sufficient for com-
pletely specifying the flowmeter dynamics over the 
range of mean flows investigated. 
Turbine flowmeters are occasionally used to meas- 
ure dynamic flow rates of liquids. The accuracy of 
such dynamic measurements is questionable without 
a dynamic calibration of the flowmeter and indicat-
ing apparatus. 
Techniques for evaluating this performance that 
have been proposed determine the flowmeter response 
to large step changes in flow rate. Unfortunately, 
step changes in flow rate having short rise times are 
difficult to realize. An alternate technique for obtain-
ing a flowmeter calibration was investigated. The 
calibration was obtained for a 3/8-inch flowmeter 
(continued overleaf) 
This document was prepared under the sponsorship of the National 
Aeronautics and Space Administration. Neither the UniteØ 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=19690000652 2020-03-16T18:34:30+00:00Z
by sinusoidally perturbing the liquid flow rate through 
a line terminated with an orifice. The flow indicated 
by the flowmeter was compared with that obtained 
from the orifice-pressure-drop measurements. This 
technique has the advantages that it employs easily 
obtained sinusoidal perturbation, and it provides 
repeatable results. 
Note: 
The following documentation may be obtained 
from:
Clearinghouse for Federal Scientific 
and Technical Information 
Springfield, Virginia 22151 
Single document price $3.00 
(or microfiche $0.65)
Reference: NASA TMX-1736 (N69-17702), 
Dynamic Calibration of Turbine Flow-
meters by Means of Frequency Response 
Tests 
Patent status: 
No patent action is contemplated by NASA. 
Source: Grady H. Stevens 
Lewis Research Center 
(LEW-110 14) 
Brief 69-10764	 Category 01


Dynamic calibration of turbine flowmeters

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