capacitive flowmeter for gas-solids flow applications...
TRANSCRIPT
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Institute of Electrical Measurement and Signal Processing
Capacitive Flowmeter for Gas-Solids Flow pApplications Exploiting Spatial Frequency
Daniel Hrach, Anton Fuchs, and Hubert ZanglDaniel Hrach, Anton Fuchs, and Hubert Zangl
Graz University of Technology
I tit t f El t i l M t d M t Si l P iInstitute of Electrical Measurement and Measurement Signal Processing
Kopernikusgasse 24 / IV, 8010 Graz, Austria
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
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Institute of Electrical Measurement and Signal Processing
A dAgenda
Introduction State of the Art Granular Flow Sensors Capacitive Correlator Capacitive Spatial Filter Advanced Excitation Scheme Experimental Setup Conclusion
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
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Institute of Electrical Measurement and Signal Processing
I t d tiIntroduction
P ti iPneumatic conveying:
Solid particles in gas clean, flexible and
reliable conveying solutionsolution
applicable for coal dust, wooden- or plastic ppellets, salt, sugar, flour, ...
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
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Institute of Electrical Measurement and Signal Processing
State of the Art Gran lar Flo SensorsState of the Art Granular Flow SensorsOptical:
PIV PIV problems with dust
Ultrasonic: doppler shift works only in special cases (low particle number, problems
with sound distribution in the pipe material) GGamma rays: correlative principle expensive personal security import/export environmentexpensive personal, security, import/export, environment, ..
Capacitive: correlative or spatial filtering principle
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
Granular flow measurement is challenging!
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Institute of Electrical Measurement and Signal Processing
Capaciti e CorrelatorCapacitive CorrelatorCorrelative principles can also be used with light, gamma rays, magnetic principlesp p
Two sensor positions with known distance inwith known distance in flow direction result in a time shifted measurement signalmeasurement signal
velocity = sensor distance
T
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
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Institute of Electrical Measurement and Signal Processing
C iti S ti l FiltCapacitive Spatial Filter
P i i l ll k i Principle well known in
optics
Pipe interior seperated Pipe interior seperated
into a regular array of
different sensitive areas
Particles with constant
velocity cause quasi
periodic signal
velocity = electrode distance1
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
velocity = electrode distance . T
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Institute of Electrical Measurement and Signal Processing
Capaciti e Spatial Filter IICapacitive Spatial Filter II
many concurrent y
particles in the
volume cause large
offset capacity
low signal powerg p
advanced excitation
pattern required
velocity = electrode distance2
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
velocity = electrode distance . T
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Institute of Electrical Measurement and Signal Processing
Advanced Excitation Scheme
FEM Simulation shows:
lower number of periods
f mean free measurement signal
increased signal increased signal power
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
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Institute of Electrical Measurement and Signal Processing
Experimental Setup
variable speed fan
pellets with a diameter of 3 mm and a permittivity of about 3
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
Hot film anemometer
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Institute of Electrical Measurement and Signal Processing
Experimental Setup II
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
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Institute of Electrical Measurement and Signal Processing
Experimental Setup III
in-/quadrature phase
measurement
sampling rate approx.
8 kHz
Particle velocity
determination by means
of frequency estimation
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
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Institute of Electrical Measurement and Signal Processing
Experimental Setup IV
Periodogram calculation:
Frequency estimation
using overlapping FFTs
higher airflow velocity
(higher particle number)
causes higher amplitude
in frequency spectrum
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
Sensor principle works!
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Institute of Electrical Measurement and Signal Processing
Concl sionConclusion
Non invasing measurement system for particle velocityg y p y Based on capacitive spatial filtering Advanced excitation pattern presentedp p Differential excitation allows higher gains Laboratory test results presentedy p
Principle of spatial filtering IS applicable to capacitive fl tflow measurement
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter
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Institute of Electrical Measurement and Signal Processing
Capacitive Flowmeter for Gas-Solids FlowCapacitive Flowmeter for Gas Solids Flow
Applications Exploiting Spatial Frequency
Thank you!
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Daniel Hrach SAS 2008, Atlanta, 12 Feb 2008 Capacitive Flowmeter