515 research outputs found
Experimental investigations of two-phase flow measurement using ultrasonic sensors
This thesis presents the investigations conducted in the use of ultrasonic
technology to measure two-phase flow in both horizontal and vertical pipe flows
which is important for the petroleum industry. However, there are still key
challenges to measure parameters of the multiphase flow accurately. Four
methods of ultrasonic technologies were explored.
The Hilbert-Huang transform (HHT) was first applied to the ultrasound signals of
air-water flow on horizontal flow for measurement of the parameters of the two-
phase slug flow. The use of the HHT technique is sensitive enough to detect the
hydrodynamics of the slug flow. The results of the experiments are compared
with correlations in the literature and are in good agreement.
Next, experimental data of air-water two-phase flow under slug, elongated
bubble, stratified-wavy and stratified flow regimes were used to develop an
objective flow regime classification of two-phase flow using the ultrasonic
Doppler sensor and artificial neural network (ANN). The classifications using the
power spectral density (PSD) and discrete wavelet transform (DWT) features
have accuracies of 87% and 95.6% respectively. This is considerably more
promising as it uses non-invasive and non-radioactive sensors.
Moreover, ultrasonic pulse wave transducers with centre frequencies of 1MHz
and 7.5MHz were used to measure two-phase flow both in horizontal and
vertical flow pipes. The liquid level measurement was compared with the
conductivity probes technique and agreed qualitatively. However, in the vertical
with a gas volume fraction (GVF) higher than 20%, the ultrasound signals were
attenuated.
Furthermore, gas-liquid and oil-water two-phase flow rates in a vertical upward
flow were measured using a combination of an ultrasound Doppler sensor and
gamma densitometer. The results showed that the flow gas and liquid flow rates
measured are within ±10% for low void fraction tests, water-cut measurements
are within ±10%, densities within ±5%, and void fractions within ±10%. These
findings are good results for a relatively fast flowing multiphase flow
Two-phase slug flow measurement using ultra-sonic techniques in combination with T-Y junctions
The accurate measurement of multiphase flows of oil/water/gas is a critical element
of oil exploration and production. Thus, over the last three decades; the development
and deployment of in-line multiphase flow metering systems has been a major focus
worldwide. Accurate measurement of multiphase flow in the oil and gas industry is
difficult because there is a wide range of flow regimes and multiphase meters do not
generally perform well under the intermittent slug flow conditions which commonly
occur in oil production.
This thesis investigates the use of Doppler and cross-correlation ultrasonic
measurements made in different high gas void fraction flow, partially separated
liquid and gas flows, and homogeneous flow and raw slug flow, to assess the
accuracy of measurement in these regimes.
This approach has been tested on water/air flows in a 50mm diameter pipe facility.
The system employs a partial gas/liquid separation and homogenisation using a T-Y
junction configuration. A combination of ultrasonic measurement techniques was
used to measure flow velocities and conductivity rings to measure the gas fraction. In
the partially separated regime, ultrasonic cross-correlation and conductivity rings are
used to measure the liquid flow-rate. In the homogeneous flow, a clamp-on
ultrasonic Doppler meter is used to measure the homogeneous velocity and combined
with conductivity ring measurements to provide measurement of the liquid and gas
flow-rates. The slug flow regime measurements employ the raw Doppler shift data
from the ultrasonic Doppler flowmeter, together with the slug flow closure equation
and combined with gas fraction obtained by conductivity rings, to determine the
liquid and gas flow-rates.
Measurements were made with liquid velocities from 1.0m/s to 2.0m/s with gas void
fractions up to 60%. Using these techniques the accuracies of the liquid flow-rate
measurement in the partially separated, homogeneous and slug regimes were 10%,
10% and 15% respectively. The accuracy of the gas flow-rate in both the
homogeneous and raw slug regimes was 10%. The method offers the possibility of
further improvement in the accuracy by combining measurement from different
regimes
Model-based Filtering of Interfering Signals in Ultrasonic Time Delay Estimations
In dieser Arbeit werden modellbasierte algorithmische AnsĂ€tze zur Interferenz-invarianten ZeitverschiebungsschĂ€tzung vorgestellt, die speziell fĂŒr die SchĂ€tzung kleiner Zeitverschiebungsdifferenzen mit einer notwendigen Auflösung, die deutlich unterhalb der Abtastzeit liegt, geeignet sind. Daher lassen sich die Verfahren besonders gut auf die Laufzeit-basierte Ultraschalldurchflussmessung anwenden, da hier das Problem der Interferenzsignale besonders ausgeprĂ€gt ist. Das Hauptaugenmerk liegt auf der Frage, wie mehrere Messungen mit unterschiedlichen Zeitverschiebungen oder Prozessparametern zur UnterdrĂŒckung der Interferenzsignale in Ultraschalldurchflussmessungen verwendet werden können, wobei eine gute Robustheit gegenĂŒber additivem weiĂen GauĂ\u27schen Rauschen und eine hohe Auflösung erhalten bleiben sollen. Zu diesem Zweck wird ein Signalmodell angenommen, welches aus stationĂ€ren Interferenzsignalen, die nicht von wechselnden Zeitverschiebungen abhĂ€ngig sind, und aus Zielsignalen, die den Messeffekt enthalten, besteht.
ZunĂ€chst wird das Signalmodell einer Ultraschalldurchflussmessung und sein dynamisches Verhalten bei Temperatur- oder Zeitverschiebungsschwankungen untersucht. Ziel ist es, valide SimulationsdatensĂ€tze zu erzeugen, mit denen die entwickelten Methoden sowohl unter der PrĂ€misse, dass die Daten perfekt zum Signalmodell passen, als auch unter der PrĂ€misse, dass Modellfehler vorliegen, getestet werden können. Dabei werden die Eigenschaften der Signalmodellkomponenten, wie Bandbreite, StationaritĂ€t und TemperaturabhĂ€ngigkeit, identifiziert. Zu diesem Zweck wird eine neue Methode zur Modellierung der TemperaturabhĂ€ngigkeit der Interferenzsignale vorgestellt. Nach der Charakterisierung des gesamten Messsystems wird das Signalmodell -- angepasst an die Ultraschalldurchflussmessung -- als Grundlage fĂŒr zwei neue Methoden verwendet, deren Ziel es ist, die Auswirkungen der Interferenzsignale zu reduzieren.
Die erste vorgeschlagene Technik erweitert die auf der Signaldynamik basierenden AnsĂ€tze in der Literatur, indem sie die Voraussetzungen fĂŒr die erforderliche Varianz der Zeitverschiebungen abschwĂ€cht. Zu diesem Zweck wird eine neue Darstellung von mehreren Messsignalen als Punktwolken eingefĂŒhrt. Die Punktwolken werden dann mithilfe der Hauptkomponentenanalyse und B-Splines verarbeitet, was entweder zu Interferenz-invarianten ZeitverschiebungsschĂ€tzungen oder geschĂ€tzten Interferenzsignalen fĂŒhrt. In diesem Zusammenhang wird eine neuartige gemeinsame B-Spline- und RegistrierungsschĂ€tzung entwickelt, um die Robustheit zu erhöhen.
Der zweite Ansatz besteht in einer regressionsbasierten SchĂ€tzung der Zeitverschiebungsdifferenzen durch das Erlernen angepasster SignalunterrĂ€ume. Diese UnterrĂ€ume werden effizient durch die Analytische Wavelet Packet Transformation berechnet, bevor die resultierenden Koeffizienten in Merkmale transformiert werden, die gut mit den Zeitverschiebungssdifferenzen korrelieren. DarĂŒber hinaus wird ein neuartiger, unbeaufsichtigter Unterraum-Trainingsansatz vorgeschlagen und mit den konventionellen Filter- und Wrapper-basierten Merkmalsauswahlmethoden verglichen.
SchlieĂlich werden beide Methoden in einem experimentellen Ultraschalldurchflussmesssystem mit einem hohen MaĂ an vorhandenen Interferenzsignalen getestet, wobei sich zeigt, dass sie in den meisten FĂ€llen den Methoden aus der Literatur ĂŒberlegen sind. Die QualitĂ€t der Methoden wird anhand der Genauigkeit der ZeitverschiebungsschĂ€tzung bewertet, da die Grundwahrheit fĂŒr die Interferenzsignale nicht zuverlĂ€ssig bestimmt werden kann. Anhand verschiedener DatensĂ€tze werden die AbhĂ€ngigkeiten von den Hyperparametern, den Prozessbedingungen und, im Falle der regressionsbasierten Methode, dem Trainingsdatensatz analysiert
Model-based Filtering of Interfering Signals in Ultrasonic Time Delay Estimations
This work presents model-based algorithmic approaches for interference-invariant time delay estimation, which are specifically suited for the estimation of small time delay differences with a necessary resolution well below the sampling time. Therefore, the methods can be applied particularly well for transit-time ultrasonic flow measurements, since the problem of interfering signals is especially prominent in this application
Model-based Filtering of Interfering Signals in Ultrasonic Time Delay Estimations
This work presents model-based algorithmic approaches for interference-invariant time delay estimation, which are specifically suited for the estimation of small time delay differences with a necessary resolution well below the sampling time. Therefore, the methods can be applied particularly well for transit-time ultrasonic flow measurements, since the problem of interfering signals is especially prominent in this application
Electronics for Sensors
The aim of this Special Issue is to explore new advanced solutions in electronic systems and interfaces to be employed in sensors, describing best practices, implementations, and applications. The selected papers in particular concern photomultiplier tubes (PMTs) and silicon photomultipliers (SiPMs) interfaces and applications, techniques for monitoring radiation levels, electronics for biomedical applications, design and applications of time-to-digital converters, interfaces for image sensors, and general-purpose theory and topologies for electronic interfaces
Technology applications
A summary of NASA Technology Utilization programs for the period of 1 December 1971 through 31 May 1972 is presented. An abbreviated description of the overall Technology Utilization Applications Program is provided as a background for the specific applications examples. Subjects discussed are in the broad headings of: (1) cancer, (2) cardiovascular disease, (2) medical instrumentation, (4) urinary system disorders, (5) rehabilitation medicine, (6) air and water pollution, (7) housing and urban construction, (8) fire safety, (9) law enforcement and criminalistics, (10) transportation, and (11) mine safety
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