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Research Papers: Techniques and Procedures

Instantaneous Liquid Flow Rate Measurement Utilizing the Dynamics of Laminar Pipe Flow

[+] Author and Article Information
Bernhard Manhartsgruber

Institute of Machine Design and Hydraulic Drives, Johannes Kepler University, Altenbergerstrasse 69, 4040 Linz, Austriabernhard.manhartsgruber@jku.at

J. Fluids Eng 130(12), 121402 (Oct 27, 2008) (8 pages) doi:10.1115/1.2969464 History: Received February 18, 2008; Revised July 09, 2008; Published October 27, 2008

This paper deals with the utilization of the dynamic characteristics of laminar flow in circular pipes for the indirect measurement of flow rates. A discrete-time state space realization of the transmission line dynamics is computed via inverse Laplace transform and an identification and model reduction method based on the singular value decomposition. This dynamic system is used for the computation of the flow rate at one end of a pipe section. Special attention is paid to the identification of the speed of sound and the dimensionless dissipation number of the pipe section, since exact knowledge of these parameters is crucial for the reliability of the measurement results. First, experimental validation results are given in a limited range of operating frequencies between 100 Hz and 2000 Hz. Flow rate variations within ±1.2l/min have been measured with an uncertainty of ±0.07l/min at the 95% confidence level. The test fluid was mineral oil.

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Copyright © 2008 by American Society of Mechanical Engineers
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References

Figures

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Figure 7

Comparison of the measured pressure p1 against the value computed from p0 and p2

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Figure 8

The match between the left-hand side and right-hand side of Eq. 10

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Figure 9

Flow rate Q0(t) computed from measurements of p0(t) and p2(t)

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Figure 4

Segment of measurement data

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Figure 3

Gaussian pulse excitation signal: whole period with a blowup of the pulse

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Figure 2

Experimental setup

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Figure 5

Discrete amplitude spectra of the pressures p0, p1, and p2

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Figure 6

Dependence of the identified parameters on the upper limit frequency

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