EP4078097A1 - Method for measuring the flow of a liquid medium having variable gas content, on the basis of a differential-pressure measurement - Google Patents

Method for measuring the flow of a liquid medium having variable gas content, on the basis of a differential-pressure measurement

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Publication number
EP4078097A1
EP4078097A1 EP20816979.7A EP20816979A EP4078097A1 EP 4078097 A1 EP4078097 A1 EP 4078097A1 EP 20816979 A EP20816979 A EP 20816979A EP 4078097 A1 EP4078097 A1 EP 4078097A1
Authority
EP
European Patent Office
Prior art keywords
flow
flow regime
value
measurement
differential pressure
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP20816979.7A
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German (de)
French (fr)
Inventor
Stephan Schäfer
Hao Zhu
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Endress and Hauser Flowtec AG
Original Assignee
Endress and Hauser Flowtec AG
Flowtec AG
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Publication date
Application filed by Endress and Hauser Flowtec AG, Flowtec AG filed Critical Endress and Hauser Flowtec AG
Publication of EP4078097A1 publication Critical patent/EP4078097A1/en
Withdrawn legal-status Critical Current

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/74—Devices for measuring flow of a fluid or flow of a fluent solid material in suspension in another fluid
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F1/00—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow
    • G01F1/05—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects
    • G01F1/34—Measuring the volume flow or mass flow of fluid or fluent solid material wherein the fluid passes through a meter in a continuous flow by using mechanical effects by measuring pressure or differential pressure
    • G01F1/50—Correcting or compensating means
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
    • G01F15/02—Compensating or correcting for variations in pressure, density or temperature
    • G01F15/022—Compensating or correcting for variations in pressure, density or temperature using electrical means
    • G01F15/024—Compensating or correcting for variations in pressure, density or temperature using electrical means involving digital counting
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01F—MEASURING VOLUME, VOLUME FLOW, MASS FLOW OR LIQUID LEVEL; METERING BY VOLUME
    • G01F15/00—Details of, or accessories for, apparatus of groups G01F1/00 - G01F13/00 insofar as such details or appliances are not adapted to particular types of such apparatus
    • G01F15/02—Compensating or correcting for variations in pressure, density or temperature
    • G01F15/04—Compensating or correcting for variations in pressure, density or temperature of gases to be measured
    • G01F15/043—Compensating or correcting for variations in pressure, density or temperature of gases to be measured using electrical means
    • G01F15/046—Compensating or correcting for variations in pressure, density or temperature of gases to be measured using electrical means involving digital counting

Definitions

  • the present invention relates to a method for flow measurement based on a differential pressure measurement by means of an effective pressure transmitter through which the medium flows.
  • This measuring principle is the established state of the art and is described in: "Flow Manual", 4th edition 2003, with ISBN 3-9520220-3-9.
  • Flow measurement based on differential pressure measurement has established itself, for example, as a supplementary measurement principle to Coriolis mass flow measurement when a large gas load of a liquid medium affects the measurement accuracy of the Coriolis mass flow sensor.
  • the combination of these measurement principles is described, for example, in the patent application DE 10 2005 046 319 A1 and the as yet unpublished patent application with the file number DE 10 2018 130 182.0.
  • the method according to the invention for measuring the flow of a liquid medium with a variable gas load on the basis of a differential pressure measurement by means of a differential pressure transmitter through which the medium flows comprises: determining a differential pressure measurement between two measuring points of the differential pressure transmitter; Determining a flow regime; Determining a flow rate measurement based on the differential pressure measurement; and the flow regime.
  • determining the flow rate includes determining a gas volume fraction.
  • the determination of the gas volume portion includes the determination of at least one gas volume portion selected from suspended bubbles, free bubbles and slugs.
  • the determination of the flow regime is based on at least one measured variable that characterizes a media property that che is selected from the list of the following media properties: density, viscosity, temperature, heat capacity, thermal conductivity, electrical conductivity and pressure.
  • the determination of the flow rate includes an evaluation of fluctuations over time or fluctuations of a measured variable that characterizes a media property.
  • the measured density value and the gas volume fraction are determined by means of a vibronic measuring sensor, in particular with a vibrating measuring tube.
  • the measured flow rate value is determined in that a preliminary measured flow value is determined on the basis of the measured differential pressure value assuming a first flow regime, the preliminary flow measured value being corrected when a second flow regime is determined which differs from the first flow regime .
  • the preliminary flow measurement value is furthermore determined as a function of a density value and / or a viscosity value, in particular the density value and / or the viscosity value being a density measurement value and / or the viscosity measurement value.
  • the correction takes place with a correction factor assigned to the flow regime.
  • the correction factor for at least one flow regime includes a function specific to the flow regime that depends at least on a gas volume fraction.
  • the correction factors for a plurality of flow regimes each include a function specific to the flow regime, which depends at least on a gas volume fraction, the functions of various flow regimes differing from one another.
  • the first flow regime comprises a flow of a single-phase medium.
  • Fig. 2a to c Schematic sketches of different flow regimes and the associated time courses of the differential pressure, including:
  • Fig. 2a Slug flow
  • Fig. 2c Suspended microbubbles or homogeneous liquid
  • Fig. 1 shows schematically the pressure drop dp across a differential pressure transducer at various exemplary mass flow rates rrn, m 2 , m 3 , as a function of the gas load, the pressure drop being shown for different flow regimes. It can be clearly seen that with identical mass flow rates rhi, the pressure drop increases with increasing gas loading. The facts are made more complicated by the fact that the pressure drop with identical gas loading and identical mass flow differs depending on the flow regime. The pressure drop for suspended bubbles, for free bubbles and for so-called slug flow is shown in more detail in the diagram. It can be clearly seen that the pressure drop increases significantly from flow regime to flow regime with the same gas loading for the same gas loading.
  • FIGS. 2a to 2c The flow regime mentioned and exemplary signatures of the associated differential pressure signals are shown in FIGS. 2a to 2c outlined.
  • Slugs can have a length of up to several diameters of the measuring tube.
  • the free bubbles shown in Fig. 2b are no longer held by the liquid. There are pronounced relative movements between the free bubbles and the surrounding liquid. Due to the small expansion of the free bubbles compared to the slugs, the signature of the differential pressure signal has a higher one Fluctuation frequency and possibly lower amplitudes.
  • the signature shown in FIG. 2c for suspended microbubbles or a homogeneous medium essentially corresponds to a noise which, given the given temporal resolution of a differential pressure measurement, can hardly be correlated with the size of microbubbles.
  • a third approach to the identification of the flow regime is given by an analysis of fluctuations in the density of the medium or an oscillation frequency on which the density measurement is based of a measuring tube of a Coriolis mass flow sensor or density sensor in which the medium is guided, the fluctuations for slug -Flow have a different signature than free or suspended bubbles.
  • the damping of measuring tube vibrations or the fluctuation of the damping of measuring tube vibrations can also be viewed as an indicator of a flow regime.
  • the measuring arrangement also contains a pressure sensor for determining the gas volume fractions. The measured pressure value determined in this way and / or its fluctuation can also be used to identify the flow regime.
  • the parameters mentioned can be evaluated individually or in combination in order to identify the flow regime based on their relationship.
  • a flow regime can first be set under laboratory conditions, whereby the mass flow rate and the gas volume fraction that are possible for a given medium in this flow regime are varied in order to record associated values for selected of the above parameters. This is repeated for different flow regimes. It is then identified which parameter values are indicative of a given flow regime or enable a clear definition of the flow regime. To be favoured takes into account the parameters or parameter fluctuations that can be recorded without additional sensors.
  • the time signature of a fluctuation in density or vibration damping normalized with a preliminary mass flow rate is an indicator of slug flow if this corresponds to a characteristic spatial extent of slugs.
  • dp with i element N denotes a pressure drop at the differential pressure transducer in the i th multiphase flow regime
  • dmo describes the pressure drop for the homogeneous medium or medium loaded only with suspended bubbles
  • g indicates the respective gas load
  • dm / dt m denotes the mass flow.
  • the correction factors k, (g) can be stored in tabular form or stored as functions, in particular polynomials in g. By implementing the functions k, the correct mass flow m can then be determined for various flow regimes.
  • a differential pressure measured value is first recorded (110).
  • a flow regime is then identified (120), and the differential pressure measured value dp, in the arbitrary flow regime, is reduced to a standard pressure drop using the function k, (g) (130):
  • the mass flow rate sought is determined using a function dm / dt (dpo, g) (140).

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  • Physics & Mathematics (AREA)
  • Fluid Mechanics (AREA)
  • General Physics & Mathematics (AREA)
  • Measuring Volume Flow (AREA)

Abstract

The invention relates to a method (100) measuring the flow of a liquid medium having variable gas content, on the basis of a differential-pressure measurement by means of a differential-pressure-generating primary element, through which the medium flows, which method comprises: ascertaining a differential-pressure measurement value (110) between two measurement points of the differential-pressure-generating primary element; ascertaining a flow regime (120); ascertaining a flow rate measurement value according to the differential-pressure measurement value and the flow regime (140), the flow rate measurement value being ascertained by ascertaining a provisional flow rate measurement value on the basis of the differential-pressure measurement value under the assumption of a first flow region, which provisional flow rate measurement value is corrected if a second flow regime different from the first flow regime is determined.

Description

Verfahren zur Durchflussmessung eines flüssigen Mediums mit veränderlicher Gasbeladung auf Basis einer Differenzdruckmessung Method for measuring the flow of a liquid medium with a variable gas load based on a differential pressure measurement
Die vorliegende Erfindung betrifft ein Verfahren zur Durchflussmessung auf Basis einer Differenzdruckmessung, mittels eines von dem Medium durchströmten Wirkdruck gebers. Dieses Messprinzip ist etablierter Stand der Technik und u.a. beschrieben in: „Durchfluss-Handbuch“, 4. Auflage 2003, mit der ISBN 3-9520220-3-9. Durchflussmes sung auf Basis einer Differenzdruckmessung hat sich z.B. als ergänzendes Messprinzip zur Coriolis-Massedurchflussmessung etabliert, wenn ein große Gasbeladung eines flüssigen Mediums die Messgenauigkeit der Coriolis-Massedurchflussmessaufnehmer beeinträchtigt. Die Kombination dieser Messprinzipien ist beispielsweise beschrieben in der Offenlegungsschrift DE 10 2005 046 319 A1 und der noch unveröffentlichten Pa tentanmeldung mit dem Aktenzeichen DE 10 2018 130 182.0. Der in den genannten Schutzrechten beschriebene, ergänzende Einsatz der Differenzdruckmessung weist noch insofern Raum für Verbesserungen auf, als die Gasbeladung eines flüssigen Me diums die Messgenauigkeit beeinträchtigen kann. Es ist die Aufgabe der vorliegenden Erfindung hier Abhilfe zu schaffen. Die Aufgabe wird erfindungsgemäß gelöst durch das Verfahren gemäß dem unabhängigen Anspruch 1. The present invention relates to a method for flow measurement based on a differential pressure measurement by means of an effective pressure transmitter through which the medium flows. This measuring principle is the established state of the art and is described in: "Flow Manual", 4th edition 2003, with ISBN 3-9520220-3-9. Flow measurement based on differential pressure measurement has established itself, for example, as a supplementary measurement principle to Coriolis mass flow measurement when a large gas load of a liquid medium affects the measurement accuracy of the Coriolis mass flow sensor. The combination of these measurement principles is described, for example, in the patent application DE 10 2005 046 319 A1 and the as yet unpublished patent application with the file number DE 10 2018 130 182.0. The supplementary use of differential pressure measurement described in the aforementioned property rights still has room for improvement insofar as the gas loading of a liquid medium can impair the measurement accuracy. It is the object of the present invention to remedy this. The object is achieved according to the invention by the method according to independent claim 1.
Das erfindungsgemäße Verfahren zur Durchflussmessung eines flüssigen Mediums mit veränderlicher Gasbeladung auf Basis einer Differenzdruckmessung mittels eines von dem Medium durchströmten Wirkdruckgebers umfasst: Ermitteln eines Differenzdruckmesswerts zwischen zwei Messpunkten des Wirkdruckgebers; Ermitteln eines Durchflussregimes; Ermitteln eines Durchflussratenmesswerts in Abhängigkeit von dem Differenzdruckmesswert; und dem Durchflussregime. The method according to the invention for measuring the flow of a liquid medium with a variable gas load on the basis of a differential pressure measurement by means of a differential pressure transmitter through which the medium flows comprises: determining a differential pressure measurement between two measuring points of the differential pressure transmitter; Determining a flow regime; Determining a flow rate measurement based on the differential pressure measurement; and the flow regime.
In einer Weiterbildung der Erfindung umfasst das Ermitteln des Durchflussregi mes das Bestimmen eines Gasvolumenanteils. In a further development of the invention, determining the flow rate includes determining a gas volume fraction.
In einer Weiterbildung der Erfindung umfasst das Ermitteln des Gasvolumenan teils das Bestimmen mindestens eines Gasvolumenanteils ausgewählt aus suspen dierten Blasen, freien Blasen und Slugs. In a further development of the invention, the determination of the gas volume portion includes the determination of at least one gas volume portion selected from suspended bubbles, free bubbles and slugs.
In einer Weiterbildung der Erfindung basiert das Ermitteln des Durchflussregimes auf mindest ens einer Messgröße, welche eine Medieneigenschaft charakterisiert, wel- che ausgewählt ist aus der Liste der folgenden Medieneigenschaften: Dichte, Viskosität, Temperatur, Wärmekapazität, Wärmeleitfähigkeit, elektrische Leitfähigkeit und Druck. In a further development of the invention, the determination of the flow regime is based on at least one measured variable that characterizes a media property that che is selected from the list of the following media properties: density, viscosity, temperature, heat capacity, thermal conductivity, electrical conductivity and pressure.
In einer Weiterbildung der Erfindung umfasst das Ermitteln des Durchflussregi mes, eine Auswertung von zeitlichen Schwankungen bzw. Fluktuationen einer Mess größe, welche eine Medieneigenschaft charakterisiert. In a further development of the invention, the determination of the flow rate includes an evaluation of fluctuations over time or fluctuations of a measured variable that characterizes a media property.
In einer Weiterbildung der Erfindung werden der Dichtemesswert und der Gas volumenanteil mittels eines vibronischen Messaufnehmers, insbesondere mit einem vibrierendem Messrohr bestimmt. In a further development of the invention, the measured density value and the gas volume fraction are determined by means of a vibronic measuring sensor, in particular with a vibrating measuring tube.
In einer Weiterbildung der Erfindung wird der Durchflussratenmesswert ermittelt, indem auf Basis des Differenzdruckmesswerts unter Annahme eines ersten Durchfluss regimes ein vorläufiger Durchflussmesswert ermittelt wird, wobei der vorläufige Durch flussmesswert korrigiert wird, wenn ein zweites Durchflussregime festgestellt ist, wel ches sich von dem ersten Durchflussregime unterscheidet. In a further development of the invention, the measured flow rate value is determined in that a preliminary measured flow value is determined on the basis of the measured differential pressure value assuming a first flow regime, the preliminary flow measured value being corrected when a second flow regime is determined which differs from the first flow regime .
In einer Weiterbildung der Erfindung wird der vorläufige Durchflussmesswert weiterhin in Abhängigkeit von einem Dichtewert und/oder einem Viskositätswert er mittelt, wobei insbesondere der Dichtewert und/oder der Viskositätswert ein Dichte messwert und/oder der Viskositätsmesswert ist bzw. sind. In a further development of the invention, the preliminary flow measurement value is furthermore determined as a function of a density value and / or a viscosity value, in particular the density value and / or the viscosity value being a density measurement value and / or the viscosity measurement value.
In einer Weiterbildung der Erfindung erfolgt die Korrektur mit einem dem Durch flussregime zugeordneten Korrekturfaktor. In a further development of the invention, the correction takes place with a correction factor assigned to the flow regime.
In einer Weiterbildung der Erfindung umfasst der Korrekturfaktor für mindestens ein Durchflussregime eine für das Durchflussregime spezifische Funktion, die zumin dest von einem Gasvolumenanteil abhängt. In a further development of the invention, the correction factor for at least one flow regime includes a function specific to the flow regime that depends at least on a gas volume fraction.
In einer Weiterbildung der Erfindung umfassen die Korrekturfaktoren für mehrere Durchflussregime jeweils eine für das Durchflussregime spezifische Funktion, welche zumindest von einem Gasvolumenanteil abhängen, wobei sich die Funktionen verschie dener Durchflussregime voneinander unterscheiden. In a further development of the invention, the correction factors for a plurality of flow regimes each include a function specific to the flow regime, which depends at least on a gas volume fraction, the functions of various flow regimes differing from one another.
In einer Weiterbildung der Erfindung umfasst das erste Durchflussregime einen Durchfluss eines einphasigen Mediums. In a further development of the invention, the first flow regime comprises a flow of a single-phase medium.
Die Erfindung wird nun anhand der in den Zeichnungen dargestellten Ausfüh rungsbeispiele näher erläutert. Es zeigt: Fig. 1 : Eine schematische Darstellung von Messergebnissen für den Druckabfall bei verschiedenen Massedurchflussraten als Funktion der Gasbeladung für verschiedene Durchflussregime;The invention will now be explained in more detail with reference to the Ausfüh approximately examples shown in the drawings. It shows: 1: A schematic representation of measurement results for the pressure drop at different mass flow rates as a function of the gas loading for different flow regimes;
Fig. 2a bis c: Schematische Skizzen verschiedener Durchflussregime und der zugehörigen zeitlicher Verläufe des Differenzdrucks, darunter:Fig. 2a to c: Schematic sketches of different flow regimes and the associated time courses of the differential pressure, including:
Fig. 2a: Slug flow Fig. 2a: Slug flow
Fig. 2b: Freie Blasen Fig. 2b: Free bubbles
Fig. 2c: Suspendierte Mikroblasen bzw. homogene Flüssigkeit Fig. 2c: Suspended microbubbles or homogeneous liquid
Fig. 3: Ein Flussdiagramm eines Ausführungsbeispiels des erfindungsgemäßen Verfahrens. 3: A flow diagram of an exemplary embodiment of the method according to the invention.
Fig. 1 zeigt schematisch den Druckabfall dp an einem Wirkdruckgeber bei ver schiedenen exemplarischen Massedurchflussraten rrn, m2, m3, als Funktion der Gas beladung, wobei der Druckabfall für verschiedene Durchflussregime dargestellt ist. Es ist deutlich zu erkennen, dass bei identischen Massedurchflussraten rhi der Druckabfall mit zunehmender Gasbeladung zunimmt. Der Sachverhalt wird noch dadurch verkom pliziert, dass sich der Druckabfall bei identischer Gasbeladung und identischem Masse durchfluss, je nach Durchflussregime unterscheidet. Genauer ist im Diagramm der Druckabfall für suspendierte Blasen, für freie Blasen und für so genannten Slug-Flow dargestellt. Es ist klar ersichtlich, dass der Druckabfall bei gleicher Gasbeladung von Durchflussregime zu Durchflussregime bei gleicher Gasbeladung signifikant zunimmt. Fig. 1 shows schematically the pressure drop dp across a differential pressure transducer at various exemplary mass flow rates rrn, m 2 , m 3 , as a function of the gas load, the pressure drop being shown for different flow regimes. It can be clearly seen that with identical mass flow rates rhi, the pressure drop increases with increasing gas loading. The facts are made more complicated by the fact that the pressure drop with identical gas loading and identical mass flow differs depending on the flow regime. The pressure drop for suspended bubbles, for free bubbles and for so-called slug flow is shown in more detail in the diagram. It can be clearly seen that the pressure drop increases significantly from flow regime to flow regime with the same gas loading for the same gas loading.
Die genannten Durchflussregime und exemplarische Signaturen der zugehörigen Differenzdrucksignale sind in Fign. 2a bis 2c skizziert. Bei dem in Fig. 2a dargestellten Slug-Flow treten Fluktuationen mit einer vergleichsweise niedrigen Frequenz auf, die mit der Durchflussrate und dem Kehrwert einer charakteristischen Länge der Slugs skaliert. Slugs können eine Länge von bis zu mehreren Durchmessern des Messrohrs aufweisen. Die in Fig. 2b dargestellten freien Blasen, werden nicht mehr von der Flüs sigkeit gehalten. Es kommt zu ausgeprägten Relativbewegungen zwischen den freien Blasen und der umgebenden Flüssigkeit. Aufgrund der gegenüber den Slugs geringen Ausdehnung der freien Blasen weist die Signatur des Differenzdrucksignals eine höhere Fluktuationsfrequenz und ggf. geringere Amplituden auf. Die in Fig. 2c dargestellte Signatur für suspendierte Mikroblasen bzw. ein homogenes Medium, entspricht im Wesentlichen einem Rauschen, das bei der gegebenen zeitlichen Auflösung einer Differenzdruckmessung kaum noch mit der Größe von Mikroblasen zu korrelieren ist.The flow regime mentioned and exemplary signatures of the associated differential pressure signals are shown in FIGS. 2a to 2c outlined. In the case of the slug flow shown in FIG. 2a, fluctuations occur with a comparatively low frequency that scales with the flow rate and the reciprocal of a characteristic length of the slugs. Slugs can have a length of up to several diameters of the measuring tube. The free bubbles shown in Fig. 2b are no longer held by the liquid. There are pronounced relative movements between the free bubbles and the surrounding liquid. Due to the small expansion of the free bubbles compared to the slugs, the signature of the differential pressure signal has a higher one Fluctuation frequency and possibly lower amplitudes. The signature shown in FIG. 2c for suspended microbubbles or a homogeneous medium essentially corresponds to a noise which, given the given temporal resolution of a differential pressure measurement, can hardly be correlated with the size of microbubbles.
Um im Messbetrieb eine Massedurchflussrate auf Basis eines Druckabfalls bestimmen zu können, ist es erforderlich das vorliegende Durchflussregime zu identifizieren. Die beschriebenen Signaturen bieten hierzu einen ersten Ansatz. Ein zweiter Ansatz zur Identifizierung des Durchflussregimes ist auf Basis von Informationen über den Anteil freier und gebundener Blasen gegeben. In der noch unveröffentlichten Patentanmel dung DE 102019115215.1 wird eine qualitative Darstellung des Anteils freier Blasen und suspendierter Blasen gelehrt. In der noch unveröffentlichten Patentanmeldung DE 102019135299.1 wird eine quantitative Ermittlung des Anteiles freier und gebundener Blasen beschrieben. Ein dritter Ansatz zur Identifizierung des Durchflussregimes ist durch eine Analyse von Fluktuationen der Dichte des Mediums bzw. einer der Dichte messung zugrundeliegenden Schwingfrequenz eines Messrohrs eines Coriolis-Masse- durchflussmessaufnehmers bzw. Dichtemessaufnehmers gegeben, in dem das Medium geführt wird, wobei die Fluktuationen für Slug-Flow eine andere Signatur aufweisen als für freie oder suspendierte Blasen. Anstelle der Dichte kann auch die Dämpfung von Messrohrschwingungen bzw. die Fluktuation der Dämpfung von Messrohrschwingun gen als Indikator für ein Durchflussregime betrachtet werden. Weiterhin enthält die Messanordnung zur Bestimmung der Gasvolumenanteile einen Drucksensor. Der damit ermittelte Druckmesswert und/oder dessen Fluktuation kann ebenfalls zur Identifikation des Durchflussregimes herangezogen werden. Die genannten Parameter können einzeln oder in Kombination ausgewertet werden, um anhand von deren Beziehung die Durchflussregime zu identifizieren. In order to be able to determine a mass flow rate on the basis of a pressure drop during measurement operation, it is necessary to identify the flow regime at hand. The signatures described offer a first approach. A second approach to the identification of the flow regime is given on the basis of information about the proportion of free and bound bubbles. In the as yet unpublished patent application DE 102019115215.1, a qualitative representation of the proportion of free bubbles and suspended bubbles is taught. The as yet unpublished patent application DE 102019135299.1 describes a quantitative determination of the proportion of free and bound bubbles. A third approach to the identification of the flow regime is given by an analysis of fluctuations in the density of the medium or an oscillation frequency on which the density measurement is based of a measuring tube of a Coriolis mass flow sensor or density sensor in which the medium is guided, the fluctuations for slug -Flow have a different signature than free or suspended bubbles. Instead of the density, the damping of measuring tube vibrations or the fluctuation of the damping of measuring tube vibrations can also be viewed as an indicator of a flow regime. The measuring arrangement also contains a pressure sensor for determining the gas volume fractions. The measured pressure value determined in this way and / or its fluctuation can also be used to identify the flow regime. The parameters mentioned can be evaluated individually or in combination in order to identify the flow regime based on their relationship.
Zur Implementierung der Identifikation kann zunächst unter Laborbedingungen, ein Durchflussregime eingestellt werden, wobei die Massedurchflussrate und der Gas volumenanteil, die für ein gegebenes Medium in diesem Durchflussregime möglich sind variiert werden, um zugehörige Werte für ausgewählte der obigen Parameter zu erfas sen. Dieses wird für verschiedene Durchflussregime wiederholt. Anschließend wird identifiziert, welche Parameterwerte indiziell für ein gegebenes Durchflussregime sind bzw. eine eindeutige Definition des Durchflussregimes ermöglichen. Bevorzugt werden die Parameter oder Parameterfluktuationen berücksichtigt, die ohne zusätzliche Sen sorik erfasst werden können. To implement the identification, a flow regime can first be set under laboratory conditions, whereby the mass flow rate and the gas volume fraction that are possible for a given medium in this flow regime are varied in order to record associated values for selected of the above parameters. This is repeated for different flow regimes. It is then identified which parameter values are indicative of a given flow regime or enable a clear definition of the flow regime. To be favoured takes into account the parameters or parameter fluctuations that can be recorded without additional sensors.
So ist beispielsweise die zeitliche Signatur einer mit einer vorläufigen Masse durchflussrate normierten Fluktuation der Dichte bzw. der Schwingungsdämpfung ein Indikator für Slug-Flow, wenn dies einer charakteristischen räumlichen Ausdehnung von Slugs entspricht. For example, the time signature of a fluctuation in density or vibration damping normalized with a preliminary mass flow rate is an indicator of slug flow if this corresponds to a characteristic spatial extent of slugs.
Die beobachteten Differenzdruckmesswerte bei einer Massedurchflussrate m in einem mehrphasigen Durchflussregime eines Mediums mit einer gegebenen Gasbe ladung werden mit den bei der gleichen Massedurchflussrate normiert. Die resultieren- den Korrekturfaktoren k, (g) werden für verschiedene Durchflussregime jeweils mit einer für das Durchflussregime spezifische Funktion der Gasbeladung gefittet: The measured differential pressure values observed at a mass flow rate m in a multiphase flow regime of a medium with a given gas charge are normalized with those at the same mass flow rate. The resulting correction factors k, (g) are fitted for different flow regimes with a function of the gas loading specific to the flow regime:
So das gilt: So that applies:
Hierbei bezeichnet dp, mit i Element N einen Druckabfall am Wirkdruckgeber im i- ten mehrphasigen Durchflussregime, während dmo den Druckabfall für das homogene Medium, bzw. nur mit suspendierten Blasen beladene Medium beschreibt, wobei g die jeweilige Gasbeladung und angibt und dm/dt = m den Massedurchfluss bezeichnet. Here dp, with i element N denotes a pressure drop at the differential pressure transducer in the i th multiphase flow regime, while dmo describes the pressure drop for the homogeneous medium or medium loaded only with suspended bubbles, where g indicates the respective gas load and and dm / dt = m denotes the mass flow.
Die Korrekturfaktoren k, (g) können tabelliert abgelegt oder als Funktionen hinterlegt werden, insbesondere Polynome in g. Durch Implementierung der Funktionen k, kann dann für verschiedene Durch flussregime der korrekte Massedurchfluss m ermittelt werden. The correction factors k, (g) can be stored in tabular form or stored as functions, in particular polynomials in g. By implementing the functions k, the correct mass flow m can then be determined for various flow regimes.
Dazu wird zunächst ein Differenzdruckmesswert erfasst (110). Dann wird ein Durchflussregime identifiziert (120), und der Differenzdruckmesswert dp, in dem beliebigen Durchflussregime wird mittels der Funktion k,(g) auf einen Standarddruck- abfall zurückgeführt (130): Schließlich wird die gesuchte Massedurchflussrate mit einer Funktion dm/dt (dpo, g) bestimmt (140). For this purpose, a differential pressure measured value is first recorded (110). A flow regime is then identified (120), and the differential pressure measured value dp, in the arbitrary flow regime, is reduced to a standard pressure drop using the function k, (g) (130): Finally, the mass flow rate sought is determined using a function dm / dt (dpo, g) (140).

Claims

Patentansprüche Claims
1. Verfahren (100) zur Durchflussmessung eines flüssigen Mediums mit veränderlicher Gasbeladung auf Basis einer Differenzdruckmessung mittels eines von dem Medium durchströmten Wirkdruckgebers, umfassend: Ermitteln eines Differenzdruckmesswerts (110) zwischen zwei Messpunkten des1. A method (100) for flow measurement of a liquid medium with variable gas loading on the basis of a differential pressure measurement by means of a differential pressure transducer through which the medium flows, comprising: determining a differential pressure measured value (110) between two measuring points of the
Wirkdruckgebers; Differential pressure transducer;
Ermitteln eines Durchflussregimes (120); Determining a flow regime (120);
Ermitteln eines Durchflussratenmesswerts in Abhängigkeit von dem Differenz druckmesswert; und dem Durchflussregime (140), wobei der Durchflussratenmesswert ermittelt wird, indem auf Basis des Diffe renzdruckmesswerts unter Annahme eines ersten Durchflussregimes ein vorläufiger Durchflussratenmesswert ermittelt wird, wobei der vorläufige Durchflussratenmesswert korrigiert wird, wenn ein zweites Durchflussregime festgestellt ist, welches sich von dem ersten Durchflussregime unterscheidet. Determining a flow rate measured value as a function of the differential pressure measured value; and the flow regime (140), wherein the flow rate measurement is determined by determining a preliminary flow rate measurement based on the differential pressure measurement assuming a first flow regime, the preliminary flow rate measurement being corrected if a second flow regime is determined which differs from the first flow regime differs.
2. Verfahren nach Anspruch 1 , wobei das Ermitteln des Durchflussregimes das Bestimmen eines Gasvolumenanteils umfasst. 2. The method of claim 1, wherein determining the flow regime comprises determining a gas volume fraction.
3. Verfahren nach Anspruch 2, wobei das Ermitteln des Gasvolumenanteils das Bestimmen mindestens eines Gasvolumenanteils, ausgewählt aus suspendierten3. The method according to claim 2, wherein the determination of the gas volume fraction is the determination of at least one gas volume fraction selected from suspended
Blasen, freien Blasen und Slugs umfasst. Includes bubbles, free bubbles, and slugs.
4. Verfahren nach Anspruch einem der vorhergehenden Ansprüche, wobei das Ermitteln des Durchflussregimes, auf mindestens einer Messgröße beruht, welche eine Medieneigenschaft charakterisiert, welche ausgewählt ist aus der Liste der folgenden Medieneigenschaften: Dichte, Viskosität, Temperatur, Wärmekapazität, Wärmeleitfähigkeit, elektrische Leitfähigkeit, und Druck 4. The method according to claim one of the preceding claims, wherein the determination of the flow regime is based on at least one measured variable which characterizes a media property which is selected from the list of the following media properties: density, viscosity, temperature, heat capacity, thermal conductivity, electrical conductivity, and pressure
5. Verfahren nach Anspruch 4, wobei das Ermitteln des Durchflussregimes, eine Auswertung von zeitlichen Schwankungen der Messgröße umfasst, welche eine Medieneigenschaft charakterisiert. 5. The method according to claim 4, wherein the determination of the flow regime comprises an evaluation of fluctuations in the measured variable over time, which characterizes a media property.
6. Verfahren nach einem der vorhergehenden Ansprüche, wobei der Dichtemesswert und der Gasvolumenanteil mittels eines vibronischen Messauf nehmers, insbesondere mit einem vibrierendem Messrohr bestimmt werden. 6. The method according to any one of the preceding claims, wherein the measured density value and the gas volume fraction are determined by means of a vibronic measuring transducer, in particular with a vibrating measuring tube.
7. Verfahren nach einem der vorhergehenden Ansprüche, wobei der vorläufige Durchflussratenmesswert weiterhin in Abhängigkeit von einem Dichtewert und/oder einem Viskositätswert ermittelt wird. 7. The method according to any one of the preceding claims, wherein the preliminary measured flow rate value is further determined as a function of a density value and / or a viscosity value.
8. Verfahren nach Anspruch 7, wobei der Dichtewert und/oder der Viskositätswert ein Dichtemesswert und/oder der Viskositätsmesswert ist bzw. sind. 8. The method according to claim 7, wherein the density value and / or the viscosity value is or are a density measurement value and / or the viscosity measurement value.
9. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Kor rektur mit einem dem Durchflussregime zugeordneten Korrekturfaktor erfolgt. 9. The method according to any one of the preceding claims, wherein the correction takes place with a correction factor assigned to the flow regime.
10. Verfahren nach Anspruch 9, wobei der Korrekturfaktor für mindestens ein Durchflussregime eine für das Durchflussregime spezifische Funktion umfasst, die zumindest von einem Gasvolumenanteil abhängt. 10. The method according to claim 9, wherein the correction factor for at least one flow regime comprises a function specific to the flow regime that depends at least on a gas volume fraction.
11 . Verfahren nach Anspruch 10, wobei die Korrekturfaktoren für mehrere Durchflussregime jeweils eine für das Durchflussregime spezifische Funktion umfassen, welche zumindest von einem Gasvolumenanteil abhängen, wobei sich die Funktionen verschiedener Durchflussregime voneinander unterscheiden. 11. Method according to claim 10, wherein the correction factors for a plurality of flow regimes each comprise a function specific to the flow regime, which function depends at least on a gas volume fraction, the functions of different flow regimes differing from one another.
12. Verfahren nach einem der vorhergehenden Ansprüche, wobei das erste Durchflussregime einen Durchfluss eines einphasigen Mediums bzw. eines Mediums mit suspendierten Mikroblasen umfasst. 12. The method according to any one of the preceding claims, wherein the first flow regime comprises a flow of a single-phase medium or a medium with suspended microbubbles.
EP20816979.7A 2019-12-19 2020-12-01 Method for measuring the flow of a liquid medium having variable gas content, on the basis of a differential-pressure measurement Withdrawn EP4078097A1 (en)

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DE102005046319A1 (en) * 2005-09-27 2007-03-29 Endress + Hauser Flowtec Ag Two or multi-phase medium e.g. fluid`s, physical flow parameter e.g. flow rate, measuring method, involves producing measurement values representing parameter by considering pressure difference of medium and by usage of transfer function
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