RU2420715C2 - Multi-phase coriolis flowmetre - Google Patents

Abstract

FIELD: electricity. ^ SUBSTANCE: in digital flow metre the controller connected to sensor and oscillation generator, which are connected to flow metre tube, is provided with possibility of control for input of apparent density of two-phase flow, which is determined with flow metre, and output of corrected density of two-phase flow. Controller is also provided with possibility of control for input of apparent mass flow of two-phase flow determined with flow metre and for output of corrected mass flow, for input of apparent fraction of the first phase of two-phase flow, which is determined with flow metre, and for output of corrected fraction of the first phase, and for determining mass flow rate of the first phase and mass flow rate of the second phase, as well as for determining reduced velocity of the first phase and reduced velocity of the second phase on the basis of mass flow rate of the first phase and mass flow rate of the second phase respectively, and for determining sliding velocity of the first phase relative to the second phase on the basis of average velocity of the first phase and average velocity of the second phase. ^ EFFECT: invention improves measurement accuracy. ^ 45 cl, 32 dwg

Description

FIELD OF THE INVENTION

The present invention relates to flow meters.

BACKGROUND OF THE INVENTION

Flow meters provide information on materials carried through a pipeline or flow tube. For example, mass flow meters provide an indication of the mass of material carried through a pipeline. Similarly, densitometers or densitometers provide an indication of the density of the material whose flow passes through the pipeline. Mass flow meters can also provide an indication of the density of the material and, therefore, an indication of volumetric flow.

For example, Coriolis-type mass flowmeters are based on the Coriolis effect, according to which the material passing through the pipeline becomes a mass passing in the radial direction under the influence of the Coriolis force, and therefore experiences acceleration. Many Coriolis-type mass flowmeters excite the Coriolis force through sinusoidal vibrations of the pipeline around a major axis perpendicular to the length of the pipe. In such mass flowmeters, the Coriolis reaction force experienced by the mass of the passing fluid is transmitted to the pipeline itself, manifesting itself as a deviation or displacement of the pipeline in the direction of the Coriolis force vector in the plane of rotation.

SUMMARY OF THE SUMMARY OF THE INVENTION

In accordance with one general aspect, the flow meter comprises a vibratory flow tube, an oscillator connected to the flow tube and controlled to communicate movement of the flow tube, a sensor connected to the flow tube and operable to measure the movement of the flow tube and generate a sensor signal, and a controller connected to receive a sensor signal, the controller being controlled to determine a first flow rate of the first phase in a two-phase flow through cutting a flow tube and determining a second flow rate of a second phase in a two-phase flow.

Embodiments may include one or more of the following elements. For example, the first phase may include gas, and the second phase may include liquid.

The controller can be controlled to enter an apparent two-phase flow density as determined by the flow meter and output an adjusted two-phase flow density. The controller can be controlled to correct apparent density based on a theoretical relationship between apparent density and adjusted density or based on an empirical relationship between apparent density and adjusted density (for example, based on a table storing the relationship between apparent density and adjusted density).

The controller can be controlled to input the apparent specific mass flow rate of the two-phase flow determined by the flow meter, and output the adjusted specific mass flow rate of the two-phase flow. The controller can be controlled to correct the apparent specific mass flow rate based on a theoretical or empirical relationship, for example, a tabular relationship, between the apparent specific mass flow rate and the adjusted mass flow rate.

The controller can be controlled to input the apparent fraction of the first phase of the two-phase stream, determined by a flowmeter that determines the amount of the first phase in the two-phase stream, and output the adjusted fraction of the first phase of the two-phase stream. The controller can be controlled to input a fraction of a first phase of a two-phase flow detected by a phase fraction sensor that is located outside the flowmeter.

The controller can be controlled to determine the first flow rate and the second flow rate based on the adjusted values of the determined density and the determined specific mass flow rate of the two-phase flow. The controller can be controlled to determine the first flow rate and the second flow rate based on the adjusted value of the determined fraction of the first phase, which determines the amount of the first phase in the two-phase flow. The controller may be controlled to determine a first flow rate and a second flow rate based on the densities of the first phase and second phase, respectively.

The controller may be controlled to determine a first reduced speed of the first phase and a second reduced speed of the second phase based on the first flow rate and the second flow rate, respectively. The controller may be controlled to determine a two-phase flow mode based on a first reduced speed and a second reduced speed. The controller may be controlled to determine the creep rate between the first phase and the second phase based on the average speed of the first phase and the average speed of the second phase. The controller may be controlled to provide corrections to the first flow rate and the second flow rate based on the first and second reduced velocities, the determined flow regime, or the creep rate, so as to obtain a corrected first flow rate and a corrected second flow rate.

In accordance with another general aspect, the method comprises determining a bulk density of a two-phase flow through a flow tube, wherein the two-phase flow includes a first phase and a second phase, determining a volume specific mass flow of a two-phase flow and determining a first specific mass flow of a first phase based on the bulk density and volume specific mass flow rate.

Embodiments may include one or more of the following elements. For example, the second specific mass flow rate of the second phase can be determined based on the bulk density and volume specific mass flow rate. In determining the bulk density, the apparent bulk density of the two-phase flow can be determined, and the apparent bulk density can be adjusted to obtain a bulk density.

When correcting apparent bulk density, the apparent bulk density can be introduced into a theoretical relationship that correlates the apparent bulk density with the adjusted bulk density, or can be introduced into an empirical relationship that correlates the apparent bulk density with the adjusted bulk density.

When correcting apparent bulk density, a first density of a first phase may be introduced. The fraction of the first phase of the two-phase flow can be determined based on the bulk density, the first density of the first phase and the second density of the second phase. When determining the first specific mass flow rate of the first phase, the first specific mass flow rate can be determined based on the fraction of the first phase and the first density.

The first reduced velocity of the first phase and the second reduced velocity of the second phase can be determined based on the first specific mass flow rate and the second specific mass flow rate, respectively. The flow regime of the two-phase flow can be determined based on the first reduced speed and the second reduced speed. The slippage rate between the first phase and the second phase can be determined based on the average speed of the first phase and the average speed of the second phase. For the first flow rate and the second flow rate, corrections may be provided based on the first and second reduced velocities, the determined flow regime, or the creep rate.

The first phase may include gas, and the second phase may include liquid.

In accordance with another general aspect, the flowmeter controller comprises a density correction system that can be controlled to input the apparent density of the two-phase flow and output the adjusted density of the two-phase flow, wherein the two-phase flow includes a first phase and a second phase, a specific mass flow correction system that can be controlled for input the apparent specific mass flow rate of the two-phase flow and the output of the adjusted specific mass flow rate of the two-phase flow, and a system for determining unit mass flow rate of flow components that can be controlled to determine the first specific mass flow rate of the first phase based on the adjusted density and the adjusted specific mass flow rate.

Embodiments may include one or more of the following elements. For example, a system for determining the specific mass flow rate of flow components can be controlled to determine a second specific mass flow rate of the second phase based on the adjusted density and the adjusted mass flow rate.

The first phase may include a liquid, and the second phase may include a gas. A system for determining the phase fraction can be provided, wherein the system can be controlled to determine the corrected phase fraction of the two-phase flow, while the system for determining the specific mass flow rate of the components of the stream can be controlled to determine the first flow rate and the second flow rate based on the adjusted phase fraction. The system for determining the phase fraction can be a system for determining the volumetric vapor content, which determines the amount of gas in a two-phase stream.

A reduced velocity determination system may be provided that can be controlled to determine a first reduced velocity of the first phase and a second reduced velocity of the second phase. The flowmeter controller may include a flow mode determination system that can be controlled to determine a two-phase flow mode.

The flow mode determination system may further be controlled to determine the phase slip rate relative to the average speed of the first phase and the average speed of the second phase. The system for determining the specific mass flow rate of the flow components can be controlled to improve the determination of the first specific mass flow rate and the second specific mass flow rate not based on the first and second reduced velocities, flow regime, or phase slip velocity.

Details of one or more embodiments are described below with reference to the accompanying drawings. Other elements will become apparent from the description, drawings and claims.

BRIEF DESCRIPTION OF THE DRAWINGS

1A is an illustration of a Coriolis flowmeter using a curved flow tube.

Figv is an illustration of a Coriolis flowmeter that uses a straight flow meter tube.

Figure 2 is a block diagram of a Coriolis flowmeter.

Figure 3 is a block diagram illustrating the operation of the Coriolis flowmeter illustrated in figure 2.

FIG. 4 is a flowchart illustrating a methodology for determining liquid and gas flow rates of a two-phase flow.

Figa and Figv are graphs illustrating the relative error in the measurement of volumetric vapor content and liquid fraction, respectively.

6 is a graph illustrating a mass flow rate error as a function of density difference for a flow tube having a specific orientation and in a selected flow region.

7 is a flowchart illustrating a methodology for adjusting density measurements.

8 is a table illustrating the relationship between the difference in theoretical density and the apparent specific mass flow rate of a two-phase flow.

Fig. 9 is a flowchart illustrating a methodology for determining volumetric vapor content measurements.

10 is a flowchart illustrating a methodology for determining adjusted measurements of specific mass flow rate.

11 is a table illustrating the relationship between the apparent specific mass flow rate and the differential pressure difference of the two-phase flow.

Fig. 12-14 are graphs illustrating examples of density corrections for a number of flow tubes.

15-20 are graphs illustrating examples of mass flow rate corrections for a number of flow tubes.

DETAILED DESCRIPTION

Types of flowmeters include digital flowmeters. For example, US Pat. No. 6,311,136, incorporated by reference in this application, describes the use of a digital flowmeter and an appropriate method involving signal processing and measurement methodology. Such digital flow meters can be very accurate in their measurements, with little or no noise, and can be able to enable a wide range of positive and negative amplification factors in the oscillator circuitry to drive the pipeline. Thus, such digital flowmeters are preferred in a variety of settings. For example, commonly referred U.S. Patent No. 6,505,519, which is incorporated herein by reference, describes the use of a wide range of gain and / or the use of a negative gain to prevent stalling and to more accurately control the flow tube, even during severe conditions for example, a two-phase stream (for example, a stream containing a mixture of liquid and gas).

Although digital flowmeters are specifically described below with reference, for example, to FIG. 1 and FIG. 2, it should be apparent that analogue flow meters also exist. Although such analog flowmeters may have typical disadvantages characteristic of analog circuitry, for example, low accuracy and high noise measurements compared to digital flowmeters, they can also be compatible with the various methodologies and embodiments described in this application. Thus, in the following description, the term "flowmeter" or "measuring device" is used to refer to any type of device and / or system in which the Coriolis flowmeter system uses various control systems and corresponding elements for measuring mass flow, density and / or other material parameters (materials) moving through a flow tube or other pipeline.

FIG. 1A illustrates a digital flow meter that utilizes a curved flow tube 102. In particular, a curved flow tube 102 can be used to measure one or more physical characteristics, such as a moving fluid, as described above. As shown in FIG. 1A, the digital transmitter 104 exchanges the signals of the sensor and the oscillation generator with the curved flow tube 102 so as to measure the vibrations of the curved flow tube 102 and to vibrate the curved flow tube 102, respectively. By quickly and accurately detecting sensor and drive signals, the digital transmitter 104, as described above, will provide fast and accurate operation of the curved flow tube 102. Examples of digital transmitters 104 used with a curved flow tube are shown, for example, in commonly-transmitted US Patent No. 6,311,136. .

FIG. 1B illustrates a digital flow meter that uses a straight flow meter tube 106. More specifically, FIG. 1B illustrates the interaction of a straight flow meter tube 106 with a digital transmitter 104. Such a straight flow meter tube conceptually functions similarly to a curved flow meter 102 and has various advantages / disadvantages compared to curved flow tube 102. For example, a straight flow tube 106 can more easily (completely) fill emptying and emptying than the curved flow tube 102, simply due to the geometry of its design. In use, the curved flow tube 102 can operate at a frequency of, for example, 50-110 Hz, while the straight flow meter 106 can function at a frequency of, for example, 300-1000 Hz. Curved flow tube 102 represents flow tubes having a plurality of diameters, and can function in a variety of orientations, for example, in a vertical or horizontal orientation.

As shown in FIG. 2, the digital mass flow meter 200 comprises a digital transmitter 104, one or more motion sensors 205, one or more oscillation generators 210, a flow tube 215 (which may also be indicated as a pipeline, and which may represent either a curved flow tube 102 or a straight-line flow tube 106, or some other type of flow tube) and a temperature sensor 220. A digital transmitter 104 may be implemented using one or more data processing devices, for example, When using a digital signal processor (DSP), user-programmable gate array (FPGA), problem-oriented application-specific integrated circuit (ASIC), other programmable logic or gate arrays, or programmable logic with a processor core. It should be obvious that, as described in US Pat. No. 6,311,136, appropriate digital-to-analog converters may be included to control the oscillation generators 210, while analog-to-digital converters may be provided for converting the sensor signals from the sensors 205 for use by the digital transmitter 104.

The digital transmitter 104 generates a measurement, for example, of the density and / or mass flow rate of the material, the flow of which passes through the flow tube 215, based on at least the signals received from the motion sensors 205. The digital transmitter 104 also controls oscillation generators 210 to drive movement in the flow tube 215. This movement is measured by motion sensors 205.

Measurements of the density of the material whose flow passes through the flow tube relate, for example, to the frequency of the flow tube 215, which is excited in the flow tube 215 by the driving force exerted by the oscillation generators 210, or to the temperature of the flow tube 215. Similarly, the mass flow through the flow tube the tube 215 relates to the phase and frequency of movement of the flow tube, as well as the temperature of the flow tube 215.

The temperature in the flow tube 215, which is measured using the temperature sensor 220, affects some properties of the flow tube, for example, its rigidity and size. A digital transmitter 104 can compensate for these temperature effects. As also shown in FIG. 2, the pressure sensor 225 is in communication with the transmitter 104 and is connected to the flow tube 215 so as to be controlled to measure pressure in the material whose flow passes through the flow tube 215.

It should be obvious that the pressure of the fluid entering the flow tube 215 and the pressure drop at the corresponding points on the flow tube can be indicators of certain flow conditions. Also, although external temperature sensors can be used to measure the temperature of the fluid, such sensors can be used in addition to the internal sensor of the flow meter, designed to measure the characteristic temperature, for calibrating the flow tube. Some flow tubes also use a variety of temperature sensors to correct the differential temperature between the process fluid and the environment (for example, the temperature of the casing of the flow tube). As described in more detail below, one potential use of inlet temperature and pressure measurements is to calculate the true densities of a liquid or gas in a two-phase flow based on predefined formulas.

The liquid fraction probe 230 relates to a device for measuring the volume fraction of a liquid, for example, water, if the liquid in the flow tube 215 contains water and other fluid, for example, oil. Such a probe or similar probes can certainly be used to measure the volume fraction of a fluid other than water, if such a measurement is preferred or if the liquid does not contain water. In the description below, the measured liquid is generally allowed to be water for example purposes, so that the liquid fraction probe 230 is generally referred to as the aqueous fraction probe 230 or the flooding probe 230.

The vapor content sensor 235 measures the percentage of material in the flow tube 215, which is in gaseous form. For example, water passing through the flow tube 215 may contain air, possibly in the form of bubbles. Such a state in which the material passing through the flow tube 215 contains more than one material is generally referred to as a “two-phase flow”. In particular, the term "two-phase flow" may refer to liquid and gas; however, the term "two-phase flow" may also refer to other combinations of materials, for example, two liquids (for example, oil and water).

Various technologies, presented, in General, in figure 2 with the help of the sensor 235 volumetric steam content, exist for measuring volumetric steam content in a two-phase flow of liquid and gas. For example, there are various sensors and probes that can be introduced into the stream to determine the volumetric vapor content. As another example, a venturi is a tube (i.e. a tube with a narrowed neck, which determines the pressure and velocity of a fluid by measuring the pressure drops generated in the neck when the fluid passes through the tube), based on the fact that the gas generally moves at a higher rate than liquid (s) through constriction, can be used to determine the pressure gradient and, accordingly, to enable the determination of volumetric vapor content. Volumetric vapor measurements can also be obtained using equipment that is completely outside the flow tube. For example, sonar measurements can be used to determine the volumetric vapor content. As a typical example of such a hydroacoustic system, a SONARtracTM type steam volume monitoring system manufactured by GiDRA Corporation of Wallingford, Connecticut can be used.

In this description, the amount of gas in a passing fluid, measured using a volumetric vapor sensor or otherwise defined, is called volumetric vapor content or α, and is defined as α = gas volume / total volume = gas volume / (liquid volume + gas volume). Accordingly, the value referred to in this application as the liquid fraction is defined as 1-α.

In many applications where mass flow measurements are required, the volumetric vapor content of the stream can be 20, 30, 40% or more. However, even with very small volumetric steam contents of 0.5%, the fundamental theory outside the limits of the Coriolis flowmeter becomes less applicable.

In addition, the presence of gas in the fluid stream can affect the measurement of the density of the fluid stream, in general, underestimating the results of the density measurement. That is, it should be obvious that the density ρ _{liquid of the} liquid, which itself passes through the flow tube, will be higher than the true density ρ _{true of the} two-phase flow containing liquid and gas, since the density of the gas (e.g. air) will be generally lower than the density of the liquid (e.g. water) in a two-phase flow. In other words, there is a decrease in density when a gas is introduced into a fluid stream that previously contained only liquid.

Outside of this physical phenomenon, a Coriolis flowmeter measuring a two-phase fluid flow containing gas can provide _apparent ρ _apparent density data, which is an imaginary measurement of the bulk density of a two-phase flow (for example, water and air). This rough measurement ρ _apparent will generally differ (below) from the true bulk density ρ _{true of the} two-phase flow. For example, the resonant frequency used by the flowmeter can become artificially higher due to the relative movement of the gas in the fluid stream, which will cause an underestimation of the density measurement. It should be obvious that many standard flow meters according to the prior art are indifferent to this problem, since most of such measuring devices stop working (for example, stop or give inaccurate measurements) even with small amounts of volumetric vapor content.

US Pat. No. 6,505,519, which is incorporated by reference in this application, states that ρ _apparent deviation (i.e., nominal rough data or bulk density data of a two-phase flow produced by a Coriolis flowmeter) from ρ _true (i.e. true gross or bulk density biphasic flow) can be characterized by many technologies. As a result, the measured ρ _apparent density can be adjusted to obtain a true bulk density ρ _corrected , which is at least approximately equal to the true density ρ _true .

To some extent, in a similar way, the nominal gross or volume specific mass flow rate MF _apparent (i.e., the specific mass flow rate of the entire two-phase flow) measured with a Coriolis flow meter may differ by a predicted or characteristic value from the true volume specific mass flow rate MF _true . It should be obvious that the correction technologies for the adjusted volumetric specific mass flow rate MF _true may differ from the density correction technologies. For example, various techniques for correcting nominal MF _apparent to obtain true MF _true (or at least MF _corrected ) are described in US Pat. No. 6,505,519.

Examples of detailed correction technologies ρ _apparent and MF _apparent are described in more detail below. Generally speaking, although with reference to FIG. 2, a digital transmitter is illustrated as comprising a density correction system 240 that has access to a mass flow correction database 245, and a specific mass flow correction system 250 that has access to a mass flow database 255. As described in more detail below, databases 245 and 255 may contain, for example, correction algorithms that are obtained theoretically or empirically, and / or correction tables that provide adjusted density and mass flow rates for a given set of input parameters. Databases 245 and 255 may also store various other types of data that may be useful in performing density and mass flow corrections. For example, a density correction database may store a series of p _liquid densities corresponding to particular fluids (e.g., water or oil).

As further shown in FIG. 2, the volumetric steam content determination / correction system 260 can be controlled to determine the volumetric steam content of a two-phase stream including liquid and gas. For example, in one embodiment, the volumetric vapor content determination / correction system 260 may determine the true volumetric vapor content α _true from the adjusted density ρ _true . In another embodiment, the volumetric vapor content determination / correction system 260 may input an apparent or nominal volumetric vapor content measurement obtained with the volumetric steam content sensor 235, and may correct the measurement based on the characterization of the error, similar to that described above for density and mass flow rate. In another embodiment, the volumetric steam sensor 235 can be controlled to directly measure the true volumetric vapor content α _true , in which case the volumetric steam determination / correction system 260 simply introduces this measurement.

As soon as the factors ρ _true , MF _true and α _{true are} determined and, possibly, in connection with other known or determined values, the specific mass flow rate determination of the flow components works to simultaneously determine the specific mass flow rate of the liquid phase component and the specific mass flow rate of the gas phase component . That is, the transmitter 104 can be controlled to determine the individual flow rates of the MF _liquid and MF _gas flow components, as opposed to determining only the volumetric flow rate of the combined and total two-phase flow MF _true . Although, as just indicated, such measurements can be determined and / or issued simultaneously, they can also be determined separately and independently from each other.

Once the flow rates of the MF _liquid and MF _gas components have been determined as generally described above, these initial definitions can be improved thanks to a process that takes into account the reduced velocities of the flow components, the sliding speeds between the components and / or the identified flow pattern. In this case, improved flow rates of MF _liquid and MF _gas can be obtained or can be obtained over time as these costs change.

Given speeds are indicated in this application as speeds that would have been if similar mass flow rates of a given phase passed as a single phase through the flow tube 215. The reduced speed determination / correction system 270 is included in the transmitter 104, for example, to determine the apparent or corrected reduced speed gas or liquid in a two-phase flow.

Sliding speeds refer to a state in which the gas and liquid phases in a two-phase flow have different average speeds. That is, the average velocity of an AV _gas is different from the average velocity of an AV _liquid . In this case, S slippage can be defined as S = AV _gas / AV _liquid .

Flow mode is a term that refers to the characterization of the mode of action by which the flow of two phases passes through the flow tube 215 relative to each other and / or the flow tube 215, and can be expressed, at least in part, based on the just determined reduced speeds . For example, one flow regime is known as a “bubble regime” in which gas is trapped (carried away) by a liquid in the form of bubbles. As another example, “shell mode” refers to a series of “plugs” or “shells” of liquid separated by relatively large gas packets. For example, in a vertical flow, projectile gas can occupy almost the entire cross-sectional area of flow tube 215, so that the resulting flow alternates between a composition containing a large amount of liquid and a composition containing a large amount of gas. It is known that there are other flow regimes that have some specific characteristics, including, for example, a ring regime of a (two-phase) flow, a dispersed regime of a (two-phase) flow, and a foamy mode of a (two-phase) flow, and others.

It is known that the existence of a specific flow regime can be influenced by various factors, including, for example, the volumetric vapor and gas content in the fluid stream, the orientation of the flow tube 215 (e.g., horizontal or vertical), the diameter of the flow tube 215, the materials included in the two-phase flow, and velocities (and relative velocities) of materials in a two-phase flow. Depending on these and other factors, the flow of a particular fluid may transition between several flow patterns during a given time period.

Information on phase slippage can be obtained, at least in part, from knowledge of the flow regime. For example, in the bubbly flow regime, allowing a uniform distribution of bubbles, there may be a slight relative motion between the phases. Where bubbles accumulate and combine to form a less uniform distribution of the gas phase, some slippage may occur between the phases, with the gas tending to leak through the liquid phase.

Figure 2 shows that there is a stream mode determination system 275 that has access to a stream mode map database 280. In this case, information on the existing flow regime, including information on phase slippage, can be obtained, stored and available for use while simultaneously determining the specific mass flow rates of liquid and gas in a two-phase flow.

It should be obvious that the various components of the digital transmitter 104, as illustrated in FIG. 2, are in communication with each other, although communication channels are not shown in detail for clarity. In addition, it should be obvious that although the standard components of the digital transmitter 104 are not shown in FIG. 2, their existence or availability for the digital transmitter 104 is allowed. For example, the digital transmitter 104 will typically include measurement systems (volumetric ) density and specific mass flow rate, as well as circuitry for excitation of the oscillation generator 210.

FIG. 3 is a flowchart 300 illustrating the operation of the Coriolis flowmeter 200 illustrated in FIG. 2. In particular, FIG. 3 illustrates the technique by which the flowmeter 200 illustrated in FIG. 2 can be controlled to simultaneously determine the flow rates of MF _liquid and MF _{gas of} liquid and gas, respectively, for a two-phase flow.

According to FIG. 3, it is determined that a two-phase gas-liquid flow exists in the flow tube 215 (302). This can be done by the operator during the configuration of the mass flow meter / densitometer for gas-liquid flow. As another example, this determination can be made automatically by using a Coriolis meter element to determine that a two-phase gas-liquid flow state exists. In the latter case, such a technique is described in more detail, for example, in US patent No. 631136 and in US patent No. 6505519 included in this application by reference.

Once the existence of a two-phase flow has been established, 304 corrected bulk density ρ _true is determined using the density correction system 240 using the density correction database 245 of the transmitter 104. That is, the nominal density ρ _{apparent is} adjusted to obtain ρ _true . The technique for performing this correction is described in more detail below.

Once ρ _true is determined, 306 true volumetric gas and vapor contents α _true can be determined using the volumetric vapor content determination / correction system 260. A 308 corrected volumetric specific mass flow rate MF _{true is} also determined using the specific mass flow rate correction system 250. As in the case of density determination, the methodology for obtaining the corrected volumetric vapor content α _true and specific mass flow rate MF _true is described in more detail below.

From the flowchart 300 of FIG. 3, it should be apparent that the definitions α _true , MF _true , ρ _true can be performed in a series of sequences. For example, in one embodiment, the adjusted volumetric vapor content α _true is determined based on a pre-calculated adjusted density ρ _true , and then the adjusted specific mass flow rate MF _{true is} determined based on α _true . In another embodiment, α _true and ρ _true can be calculated independently from each other, and / or ρ _true and MF _true can be calculated independently.

As soon as the adjusted density ρ _true , the adjusted volumetric vapor content α _true, and the adjusted specific mass flow rate MF _true are known, 310 specific mass flow rates of the gas and liquid components are determined using the specific mass flow rate determination system for the flow components. The methodology for determining the flow rates of liquid and gas components is described in more detail below with reference to figure 4.

Once determined, the flow rates of the liquid and gas components may be displayed or visually displayed 312 for use by the flowmeter operator. In this case, the operator is provided, possibly simultaneously, with information about the specific mass flow rate MF _{liquid of the} liquid and the specific mass flow rate MF _{gas of the} gas of the two-phase flow.

In some cases, this determination may be sufficient 314, in which case the output of the flow rates of the liquid / gas components completes the process route. However, in other embodiments, the determination of the specific mass flow rates of the individual components can be improved by factoring the information on the reduced velocities of the gas / liquid components, the flow regime (s) and phase slippage, if any between the components.

In particular, the reduced gas and liquid velocities, SV _gas and SV _{liquid are} determined as follows. The reduced gas velocity SV _gas is defined as

Where A _T represents the cross-sectional area of the flow tube 215, which can be determined at the point where the volumetric vapor content of the stream is measured. Similarly, the reduced fluid velocity SV _liguid is defined as

и

поскольку эти факторы вычислены на основе α_true, ρ_true и MF_true. Как результат, приведенные скорости SV_gas и SV_liquid представляют скорректированные значения

и

Кроме того, значения плотности ρ_gas и ρ_liquid нужны, как указано выше, для получения данных плотностей жидкости и газа, которые могут храниться в базе данных 245 коррекции плотности. Как более подробно описано ниже в отношении методологии вычисления скорректированной плотности ρ_true, значения плотности ρ_gas и ρ_liquid могут быть известны как функция существующих температуры или давления, определенных посредством соответствующих датчика 220 температуры и датчика 225 давления.As shown in equations 1 and 2, the definition of reduced velocities in this context refers to the earlier definition of MF _gas and MF _liquid . From the foregoing description and from FIG. 3, it should be apparent that MF _gas and MF _liguid represent corrected or true unit mass _flow rates.

and

since these factors are calculated based on α _true , ρ _true, and MF _true . As a result, the given velocities SV _gas and SV _liquid represent the adjusted values

and

In addition, the density values ρ _gas and ρ _liquid are needed, as described above, to obtain data on the density of the liquid and gas, which can be stored in the database 245 density correction. As described in more detail below with respect to the methodology for calculating the adjusted density ρ _true , the density values ρ _gas and ρ _liquid can be known as a function of the existing temperature or pressure detected by the corresponding temperature sensor 220 and pressure sensor 225.

Using reduced velocities and other known or calculated factors, some of which can be stored in the stream mode map database 280, the corresponding stream mode and / or phase slip can be determined 318 by the stream mode determination / correction system 275. As soon as the reduced velocities, flow regime and phase slippage become known, additional corrections of the corrected bulk density ρ _true , the adjusted specific mass flow rate MF _true and / or the corrected volumetric vapor content α _true can be made. In this case, as illustrated in FIG. 3, the costs of the MF _gas and MF _liquid components can be determined.

The flow regime (s) in a two-phase liquid-gas flow can be described by circuits on a graph that shows the reduced fluid velocities depending on the reduced gas velocities. As has just been described, an improvement in the determination of ρ _true , α _true, and MF _true can be obtained by first establishing the approximate values of the liquid and gas flow rates, and then applying a more detailed model for the identified flow regime. For example, with relatively low volumetric vapor content and relatively high flow, there is a flow regime in which aerated fluid behaves as a homogeneous fluid with little or no error in density and mass flow. It can be defined as a homogeneous flow that does not require correction, simply by using observation of the excitation gain, which increases slightly or does not increase, despite a significant difference in the measured density.

4 is a flowchart 400 illustrating a methodology for determining the flow rates of MF _gas and MF _liquid gas and liquid, respectively, for a two-phase flow. That is, the flowchart 400, in General, represents one example of a methodology for determining the mass flow rates 310 of liquid and gas, as described above with reference to Fig.3.

In accordance with FIG. 4, the determination of liquid and gas flow rates 310 begins with input of factors of adjusted density, volumetric vapor content, and specific mass flow rate ρ _true , α _true, and MF _true (402). In the first case, 404, the flow rates of liquid and gas are determined by 406 using equations 3 and 4:

Equations 3 and 4 assume that there is no slip rate (i.e., phase slip) between the liquid and gas phases (i.e., the average gas phase velocity, AV _gas , and the average liquid phase velocity AV _liquid are equal). This assumption is consistent with the fact that in the first case, the reduced velocities and flow regimes (and, therefore, phase slippage) were not determined.

In the second case and, therefore, 404, the determination is made, perhaps, using the flow mode determination / correction system 275 with respect to whether phase slippage 408 exists. If there is no slippage, then again 406 use equations 3 and 4 or complete the process.

If phase slippage exists 408, defined above as S = AV _gas / AV _liquid , then the terms MF _gas and MF _liquid are calculated using the cross-sectional area A _{T of the} flow tube 215, which is also used to calculate the reduced speeds in equations 1 and 2 in position 410. When using the definition of slippage determine

Since MF _true = MF _gas + MF _liquid , equations 5 and 6 can be solved for AV _liquid to obtain equation 7

As a result, the flow rates of liquid and gas are determined by 406 using equations 8 and 9

As described above, the gas trapped in the liquid forms a two-phase flow. Measurements of such a two-phase flow using a Coriolis flowmeter result in the nominal parameters ρ _apparent , α _apparent , MF _apparent to determine the density, volumetric vapor content and specific mass flow rate, respectively, of the two-phase flow. Due to the nature of the two-phase flow with respect to the functioning of the Coriolis flowmeter, these nominal parameters are incorrect due to the predicted factor. As a result, the nominal parameters can be adjusted to obtain the true parameters ρ _true , α _true , MF _true . In turn, the true adjusted values can be used to simultaneously determine the individual flow rates of the two components (liquid and gas).

On figa and figv are graphs illustrating the relative error in the measurement of volumetric vapor content and liquid fraction, respectively. On figa relative error is the relative error of the density, which is dependent on various design and functional parameters, and, in General, refers to the deviation of the apparent (nominal) density from the true combined density, which would be the expected given percentage (%) of gas in liquids.

On figv illustrates the dependence of the true liquid fraction from the nominal liquid fraction. On figv shows the results for the corresponding design of the flow meter, several linear dimensions and costs. In a more general case, the functional relationship may be more complex and dependent on linear size and flow. 5B shows a simple polynomial fit that can be used to correct the apparent liquid fraction.

A different graphical methodology may be used; for example, true volumetric steam content can be applied against the nominal volumetric steam content. For example, FIG. 6 is a graph illustrating a mass flow rate error as a function of density difference for a flow tube having a specific orientation and in a selected flow range.

7 is a flowchart 700 illustrating a methodology for correcting density measurements (304 in FIG. 3). 7, the process begins by entering 702 of the type of flow tube 215 used, which may include, for example, information about whether the flow tube 215 is curved or straight, as well as other relevant facts, such as the size or orientation of the flow tube 215.

Then determine 704 the density of the liquid without gas. This value may be useful in the following calculation (s), and also ensure that other factors that may affect the measurement of the ρ _apparent density, for example, temperature, are not mistakenly interpreted as effects of volumetric vapor content. In one embodiment, the user can directly enter the liquid density ρ _liquid along with the temperature dependence of the density. In another embodiment, known fluids (and their temperature dependencies) may be stored in the density correction database 245, in which case the user may enter the fluid by name. In yet another embodiment, the flow meter 200 may determine the density of the liquid during the time of one phase, the fluid flow, and store this value for future use.

The nominal specific mass flow rate MF _{apparent is} read 706 from the Coriolis flowmeter, and then from the Coriolis flow meter 708 the nominal density ρ _{apparent is} read. After that, the density correction system 240 performs either theoretical, algorithmic correction 710, or empirical, tabular correction 712 to determine the true density ρ _true of the gas-liquid mixture. The value ρ _true can then be deduced as the adjusted density 714.

Algorithmic density correction 710 can be determined based on the knowledge that the normal functioning of the Coriolis flowmeter will not affect the two-phase flow when measuring density, and the nominal density will drop by the value obtained from the equation describing the volumetric vapor content, as described above for the volumetric flow and is repeated in this case, for density in the form of equation 10

This can be used to determine the "density drop" or Δρ, as shown in equation 11

It should be noted that in equation 11 the Δρ value is shown as positive, however, this value can be shown as a negative difference by simply multiplying the right side of the equation by - 1, resulting in equation 12

ρ _gas can be small compared to ρ _liquid , in which case equation 12 can be simplified to equation 13

As described in detail above, density measurements made using a Coriolis flowmeter or other vibratory densitometer generally provide underestimated data and require correction. Accordingly, in accordance with the two-phase flow, equations 12 or 13 can therefore be used to determine the following two quantities: the difference in the corrected or true density Δρ _true and the difference in nominal or apparent density Δρ _arr . Using equation 13 as one example results in equations 14 and 15

The dependence between Δρ _true and Δρ _arr and the apparent specific mass flow rate MP _apparent , as well as other parameters, for example, excitation amplification, sensory balance, temperature, phase mode, and so on, can be obtained or empirically determined. This dependence can be expressed as Δρ _true = f ( _{apparent apparent} MF, excitation gain, sensory balance, temperature, phase mode and / or other factors).

As a result, this relationship can be obtained, or at least proven, for each flow tube in each setting. For a flowmeter tube of one model, known and indicated below as a Foxboro / Invensys CFS10 flowmeter tube, it was empirically determined that for some conditions the above functional dependence can be simplified only to the Δρ _apparent function and has the form corresponding to equation 16

To induce the conditions for both sides of equation 16 to zero, when there is no difference in apparent density, the dependence as a result is expressed by equation 17

M, in general, depends on the complexity of the empirical relationship, but in many cases it may be 2 or 3.

Once the difference in true density is determined, returning back to the above equations, we directly obtain the true density of the mixture ρ _true , as well as the true liquid fraction and volumetric vapor and gas content (the latter is described in more detail with reference to Fig.9).

Tabular density correction 712 can be used when, for example, a functional relationship is too complex or inconvenient to implement. In such cases, the knowledge of the values of ρ _apparent and ΔMF _apparent can be used to determine Δρ _true by using a table having the form of table 800 illustrated in Fig. 8.

Table 800 may be, for example, a table lookup table, which may be stored, for example, in a database 245 or in another storage device for use in various applications of the table. Among other things, the table can be filled during installation in the initial position for storage in the database 245 for individual application of the table.

It should be obvious that the algorithmic and / or tabular views can be expanded to include a variety of sizes, for example, gain, temperature, balance, or flow mode. Algorithmic or tabular correction can also be expanded to include other surface fitting methodologies, such as a neural network, radical basic functions, momentum analysis, or fundamental factor analysis.

As a result, it should be obvious that such extensions can be implemented in the context of FIG. 3 during the implementation of the method described above. Then, in the second case, when the flow mode is identified, the density can be further adjusted using information about the flow mode.

FIG. 9 is a flow chart 900 illustrating a methodology for determining measurements (306 in FIG. 3) of volumetric steam content. As shown in FIG. 9, the process begins with input 902 using the system 240 for determining the volumetric vapor content of the predetermined liquid density ρ _liquid and bulk (adjusted) density ρ _true .

Then, 904 _gas density ρ _gas is determined. As in determining the density of ρ _liquid liquids, there are several methodologies for determining ρ _gas . For example, ρ _gas can simply be assumed to be equal to the density of air, in general, at a known pressure, or it can be actually the known density of a particular gas. As another example, this known density ρ _gas may be one of the above factors (i.e., the density of air or special gas) at the actual or calculated pressure detected by the pressure sensor 225 and / or at the actual or calculated temperature detected by the temperature sensor 220. Temperature and pressure can be determined during routine monitoring using external equipment, as shown in FIG. 2, including a temperature sensor 220 and a pressure sensor 225.

In addition, it may be known that the gas has special characteristics with respect to factors including pressure, temperature, or compressibility. These characteristics can be entered together with gas identification and used to determine the current density ρ _{gas of} gas. As with fluid information, a multitude of gases can be stored in a memory device, possibly together with the characteristics just described, so that the user can access the density characteristics of a particular gas by simply selecting a gas from a list name.

Once the factors ρ _liquid , ρ _gas, and ρ _true became known, it should be obvious that 906 volumetric vapor contents α _true can simply be determined from equation 10. In this case, if necessary, a 908 liquid fraction can simply be determined by calculating 1-α _true .

Although the methodologies for determining the volumetric vapor content α _true based on the density are described above, it should be obvious that the volumetric vapor content can be determined using other methodologies. For example, the nominal volumetric vapor content α _apparent can be directly determined using a Coriolis flowmeter, possibly in connection with other volumetric vapor detection systems (represented in FIG. 2 by the volumetric vapor sensor 235), and adjusted based on empirical or derived equations to obtain α _true . In other embodiments, such external volumetric vapor determination systems can be used to directly measure α _true .

10 is a flowchart 1000 illustrating methodologies for determining measurements (308 in FIG. 3) of the adjusted specific mass flow rate. As shown in FIG. 10, the specific mass flow rate correction system 250 first enters 1002 the pre-calculated differential density correction Δρ _true , and then enters 1004 the measured apparent specific mass flow rate MF _apparent .

The specific mass flow rate correction system 250 employs either tabular 1006 or algorithmic 1008 correction to determine the true specific mass flow rate MF _true of the gas-liquid mixture. The value of MF _true can then be deduced 1010 as the adjusted specific mass flow rate.

When applying the specific mass flow rate correction tabular 1006, knowledge of the Δρ _true and ΔMF _apparent values can be used to determine MF _true by using a table having the form of table 1100 shown in FIG. 11.

Table 1100, as well as table 800, can be, for example, a table lookup table, which can be stored, for example, in a database 245 or in another storage device for use in different applications of the table. Among other things, the table can be filled during installation in the initial position for storage in the database 255 for individual application of the table.

The normalized values of MF _{norm_app} and MF _{norm_true} can be used instead of the true values described above to be used with a flow tube of more than one size. Inputs can also be based on correction, where the correction is determined by equation 18

It is understood that the values in equation 18 represent true or normalized values.

In the algorithmic method, as well as in the algorithmic density correction, mass flow rate correction can be realized using a theoretical or empirical functional dependence, which, as a general rule, should be in the form ΔMF = f (ΔMF _apparent , volumetric vapor content, excitation gain , balance of sensors, temperature, phase mode and / or other factors).

For some cases, this function may simply be polynomial, for example, as shown in equation 19

For a certain set of conditions, the functional relationship can be a polynomial and exponential combination, as shown in equation 20

In equation 20, d = Δρ _true , am = f (MF _apparent )

In one example, m in equation 20 can be replaced by the apparent reduced liquid velocity SV _liquid , which is given, as described above, by equation 2 as SV _liquid = MF _liquid / (ρ _liquid * _AT ).

In this case, ρ _liquid and the cross-section A _{T of the} flow tube are known or input parameters and can be real-time adjusted for temperature using, for example, an integrated device 220 for measuring temperature, a digital controller / transmitter 104.

It should be obvious that, as with the density corrections described above, the algorithmic and / or tabular types of corrections can be extended to include a variety of sizes, for example, gain, temperature, balance, or flow mode. Algorithmic or tabular correction can also be expanded to include other surface fitting methodologies, such as a neural network, radical basic functions, momentum analysis, or fundamental factor analysis.

As a result, it should be obvious that such extensions can be implemented in the context of FIG. 3 during the implementation of the method described above. For example, in the first case, the specific mass flow rate can be determined as described above. Then, in the second case, when the flow mode is identified, the specific mass flow rate can be further adjusted using information about the flow mode.

All the above functional dependences of the specific mass flow rate can be formulated differently when using the gas fraction α or the liquid fraction (1-α) instead of the density difference, as shown in table 1100, illustrated in Fig.11. Although the above methods are dependent on knowledge of the differential density difference Δρ _true , it should be obvious that other methodologies may be used to correct the nominal specific mass flow rate. For example, various methodologies for correcting measurements of the specific mass flow rate of a two-phase flow are described in US Pat. No. 6,505,519, the disclosure of which is incorporated herein by reference.

After describing the corrections of density, volumetric vapor content and specific mass flow rate in general form for the purpose, for example, simultaneously calculating the individual flow rates of components (phases) in a two-phase flow, the description and corresponding illustrations of typical embodiments of these methodologies are given below.

12-14 are graphs illustrating examples of density corrections for a number of flow tubes. In particular, these examples are based on data obtained from three vertical flow tubes to measure flow rate, the flow tubes have a diameter of _^1/2 inch (12.7 mm), _^3/4 inch (19 mm) and 1 inch (25 4 mm).

More specifically, data for the flow tube diameter of _^1/2-inch (12.7 mm) were obtained at a rate of 0.15 kg / s and 0.30 kg / sec, data for the flow tube diameter of 3/4 inch (19 mm) were obtained at a flow rate of 0.5 kg / s and 1.0 kg / s, and data for a flow tube with a diameter of 1.0 inch (25.4 mm) were obtained at a flow rate of 0.5 kg / s, 0.9 kg / s and 1.2 kg / sec. 12 illustrates the error e _{d of the} apparent density of the liquid-gas mixture (two-phase flow) depending on the true difference in the density of the liquid-gas mixture Δρ _true

where, as above, ρ _liquid is the density of the liquid without gas, ρ _true is the density of the liquid-gas mixture, and ρ _apparent is the apparent or nominal density of the liquid-gas mixture.

As shown in FIG. 12, the correction was performed based on the apparent difference in density of the mixture ρ _apparent in accordance with equation 23

As shown in FIG. 12, when fitting the data, the apparent and true difference in the density of the mixture was normalized to values between 0 and 1 by dividing them by 100, where this normalization is intended to guarantee the digital stability of the optimization algorithm. In other words, the normalized apparent and true difference in the density of the mixture is the apparent and true difference in the density of the mixture, defined as the ratio and not the percentage of the density of the liquid ρ _liquid , as shown in equation 24

A model formula based on equation 17 is provided by equation 25

In this case, the coefficients are a ₁ = -0.51097664273685, and ₂ = 1.26939674868129, and ₃ = 0.24072693119420. On figa and figv illustrates a model with the shown experimental data and residual errors. On figa and figv gives similar information, but with each expense, applied separately.

, так что, как указано выше, перепад плотности вычисляют как отношение, а не как процент. Модель (модели) коррекции плотности может быть затем применена для получения нормализованного скорректированного перепада плотности смеси

. В конечном счете, это значение не нормализуют для получения скорректированного перепада плотности

. Конечное вычисление, безусловно, не является обязательным, если скорректированный перепад плотности смеси Δρ_true определен как отношение, а не как процент.To summarize, the difference in density correction is performed at the transmitter 104 by calculating the apparent density difference Δρ _apparent using the apparent density ρ _apparent and the liquid density ρ _liquid . The value of the apparent density drop is normalized to obtain

so that, as indicated above, the density drop is calculated as a ratio, and not as a percentage. The density correction model (s) can then be applied to obtain a normalized adjusted differential density drop

. Ultimately, this value is not normalized to obtain an adjusted density drop

. The final calculation, of course, is not necessary if the adjusted mixture density difference Δρ _{true is} defined as a ratio, and not as a percentage.

15-20 are graphs illustrating examples of specific mass flow rate corrections for a number of flow tubes. In particular, these examples are based on data obtained from three vertical flow tubes to measure flow rate, the flow tubes have a diameter of _^1/2 inch (12.7 mm), _^3/4 inch (19 mm) and 1 inch (25 4 mm). More specifically, data for the flow tube diameter of _^1/2-inch (12.7 mm) were obtained at a rate of 0.15 kg / s and 0.30 kg / sec, data for the flow tube diameter of 3/4 inch (19 mm) were obtained at a flow rate of 0.5 kg / s and 1.0 kg / s, and data for a flow tube with a diameter of 1.0 inch (25.4 mm) were obtained at a flow rate of 0.5 kg / s, 0.9 kg / s and 1.2 kg / s; flow tubes with a diameter of 1 inch (25.4 mm) were used to measure 18 flows in the flow range of 0.30-3.0 kg / s with a maximum density drop of approximately 30%.

On figa and figv illustrates the errors of the apparent mass flow rate for the data used to fit the model depending on the adjusted differential density drop of the mixture Δρ _true and normalized true reduced liquid velocity; that is, the error curves of the apparent mass flow rate to the tube together with the scatter plot of the error of the apparent mass flow rate as a function of the adjusted density drop Δρ _true and the normalized true reduced fluid velocity ν _tn , as shown in equation 26

where m _t is the true mass flow rate of the fluid, i.e., the mass flow rate measured independently, Δρ _liquid is the fluid density, A _T is the cross-sectional area of the flow tube, and ν _max is the maximum value of the reduced fluid velocity (in this case, taken equal to 12) so that ν _tn gives the ratio of the true superficial liquid velocity from the entire range of the flowtube 215. In these examples, differential fluid density and superficial liquid velocity are normalized between 0 and 1 prior to fitting the model to guarantee digital Art bility for the algorithm optimization model.

On Fig illustrates the errors of the apparent mass flow depending on the adjusted differential density of the mixture and the normalized apparent apparent reduced fluid velocity with safety limits for the correction mode. That is, FIG. 16 is a graph of the dispersion of the apparent mass flow rate errors as a function of the adjusted density drop, and at this time, the normalized apparent reduced fluid velocity

, где m - кажущийся массовый расход жидкости (то есть измеряемый передатчиком 104). На график наложены границы, ограничивающие зону безопасности модели, то есть зону, для которой ожидается, что модель даст точность, подобную точности данных подгонки. При использовании этой номенклатуры погрешность е кажущегося массового расхода дается уравнением

where m is the apparent mass flow rate of the liquid (i.e., measured by the transmitter 104). Borders are imposed on the graph that limit the model’s security zone, that is, the zone for which the model is expected to give an accuracy similar to that of the fitting data. When using this nomenclature, the error e of the apparent mass flow rate is given by the equation

The model formula for this situation is shown as equation 27

Where

where in equations 27 and 28, dd _cn is the normalized corrected difference in the density of the mixture, and ν _n is the normalized apparent reduced velocity of the liquid.

In this case, the coefficients are: a ₁ = -4.7899878570465, a ₂ = 4.20395000016874, and ₃ = -5.93683498873342, a ₄ = 12.03484566235777, a ₅ = -7.70049487145104, and ₆ = 0.69537907794202 and ₇ = -0.52153213037389, and ₈ = 0.36423791515369 and a ₉ = -0.16674339233364.

On Fig illustrates a graph of the dispersion of the residual errors of the model along with the formula and coefficients of the model, that is, shows the residual errors of the model depending on the adjusted differential density of the mixture and the normalized true velocity of the fluid. On figa-18D and figa-19D shows the residual errors of the model for the entire data set used for fitting and one true data, respectively. Finally, FIGS. 20A and 20B illustrate interpolation and extrapolation of the model surface outside the safe fit zone. From FIGS. 16, 20A and 20B, the apparent mass flow rate (reduced fluid velocity) and the drop in the density range for this model should be apparent.

To summarize, in this example, the correction of mass flow in the transmitter 104 is carried out by calculating the apparent density difference, and this correction uses the method (s) described above, and normalizing the resulting value by dividing by 100 (or using the resulting normalized corrected density difference from the density model). After that, the normalized reduced fluid velocity, ν _n , is calculated, and this model is used to estimate the error e _{n of the} normalized mass flow rate, where this value gives the error of the apparent mass flow rate as the ratio of the true mass flow rate. The obtained value can be made unnormalized by multiplying it by 100, so that in accordance with this, the mass flow rate error is obtained as a percentage of the true mass flow rate. Finally, the apparent mass flow rate can be adjusted using the error of the unnormalized mass flow rate.

.

.

As is obvious, the above description has a wide range of applications for increasing the accuracy of measurement and correction of a Coriolis flowmeter in a two-phase flow. In particular, the methodologies described above are particularly useful in measurement cases in which the mass flow rate of the liquid phase and the mass flow rate of the gas phase must be measured and / or adjusted to a high level of accuracy. One application example is the measurement of the mass flow of a liquid phase and the measurement of a gas phase under oil and gas conditions.

The above description is provided in the context of the digital flowmeter illustrated in FIG. However, it should be obvious that any vibrational or oscillatory densitometer or flow meter, analog or digital, that is capable of measuring multiphase flow containing a certain fraction of the gas phase can be used. That is, some flowmeters are only capable of measuring process fluids containing a gas phase if this gas phase is limited to a small percentage of the entire process fluid, for example, less than 5%. Other flow meters, for example, the digital flow meter (s) mentioned above, are capable of functioning even if the volumetric vapor and gas content reaches 40% or more.

Many of the above equations and calculations are described based on density, specific mass flow rate and / or volumetric vapor content. However, it should be obvious similar or similar results can be obtained using varieties of these parameters. For example, instead of mass flow, a volume flow can be used. Among other things, instead of the volumetric vapor content, a liquid fraction can be used.

Several embodiments have been described. However, it should be obvious that various modifications can be made. Accordingly, other embodiments are within the scope of the following claims.

Claims (45)

1. A flow meter containing
flow tube
an oscillation generator connected to the flow tube and configured to communicate vibrations to the flow tube when a two-phase flow flows through it,
a sensor connected to the flow tube and configured to measure the movement of the flow tube and generate a sensor signal, and
a controller connected to the sensor and the oscillation generator, and the controller is configured to control
to enter the apparent density of the two-phase stream determined by the flow meter, and output the adjusted density of the two-phase stream,
for inputting the apparent mass flow rate of the two-phase flow determined by the flow meter, and outputting the adjusted mass flow rate of the two-phase flow,
to enter the apparent fraction of the first phase of the two-phase stream, determined by the flow meter, which characterizes the amount of the first phase in the two-phase stream, and output the adjusted fraction of the first phase in the two-phase stream,
and to determine the mass flow rate of the first phase in a two-phase flow through the flow tube and to determine the mass flow rate of the second phase in a two-phase flow, and
to determine the reduced velocity of the first phase and the reduced velocity of the second phase based on the mass flow rate of the first phase and the mass flow rate of the second phase, respectively,
to determine the sliding speed of the first phase relative to the second phase based on the average speed of the first phase and the average speed of the second phase. 2. The flow meter according to claim 1, wherein the controller is operable to correct apparent density based on a theoretical relationship between apparent density and adjusted density. 3. The flow meter according to claim 1, wherein the controller is operable to correct apparent density based on an empirical relationship between apparent density and adjusted density. 4. The flow meter according to claim 1, in which the controller is configured to control the apparent density based on a table storing the relationship between the apparent density and the adjusted density. 5. The flowmeter according to claim 1, in which the controller is configured to control the apparent mass flow rate based on the theoretical relationship between the apparent mass flow rate and the adjusted mass flow rate. 6. The flow meter according to claim 1, in which the controller is configured to control an apparent mass flow rate based on an empirical relationship between the apparent mass flow rate and the adjusted mass flow rate. 7. The flow meter according to claim 1, in which the controller is configured to control to input the fraction of the first phase of the two-phase flow, determined by the sensor of the phase fraction, which is located outside the flow meter. 8. The flow meter according to claim 1, in which the controller is configured to control to determine the flow rate of the first phase and the flow rate of the second phase based on the adjusted values of the determined density and the determined mass flow rate of the two-phase flow. 9. The flow meter according to claim 1, in which the controller is configured to control to determine the flow rate of the first phase and the flow rate of the second phase based on the adjusted value of the determined fraction of the first phase, which characterizes the amount of the first phase in the two-phase flow. 10. The flow meter according to claim 1, in which the controller is configured to control to determine the flow rate of the first phase and flow rate of the second phase based on the densities of the first phase and second phase, respectively. 11. The flowmeter of claim 10, wherein the controller is operable to determine a two-phase flow mode based on a reduced speed of a first phase and a reduced speed of a second phase. 12. The flow meter according to claim 11, wherein the controller is operable to provide corrections for the flow rate of the first phase and flow rate of the second phase based on the reduced velocities, a certain flow regime, or sliding speed to obtain, accordingly, a corrected flow rate of the first phase and an adjusted flow rate of the second phase. 13. The flow meter according to any one of claims 1 to 12, in which the first phase includes gas, and the second phase includes a liquid. 14. A method of measuring the flow rate of a two-phase stream, including
determining the bulk density of the two-phase flow through the flow tube, and the two-phase flow includes a first phase and a second phase,
determination of the mass flow rate of a two-phase flow,
determination of the mass flow rate of the first phase based on bulk density and mass flow rate, as well as
determination of the mass flow rate of the second phase based on bulk density and mass flow rate,
determining the reduced velocity of the first phase and the reduced velocity of the second phase based on the mass flow rate of the first phase and the mass flow rate of the second phase, respectively,
wherein determining the density includes determining the apparent bulk density of the two-phase flow and correcting the apparent bulk density to obtain the bulk density of the two-phase flow, and determining the mass flow rate includes determining the apparent mass flow rate of the two-phase flow and correcting the apparent mass flow rate to obtain the mass flow rate of the two-phase flow. 15. The method according to 14, in which the correction of apparent bulk density includes entering the apparent bulk density into a theoretical relationship that correlates the apparent bulk density with the adjusted bulk density. 16. The method according to clause 15, in which the correction of apparent bulk density includes entering the apparent bulk density in an empirical relationship that correlates the apparent bulk density with the adjusted bulk density. 17. The method according to clause 16, in which the correction of the apparent bulk density includes entering the density of the first phase. 18. The method according to 17, including determining the fraction of the first phase of a two-phase stream based on bulk density, density of the first phase and density of the second phase. 19. The method according to 14, in which the determination of the mass flow rate of the first phase includes determining the mass flow rate based on the fraction of the first phase and the density of the first phase. 20. The method of claim 14, comprising determining a two-phase stream flow mode based on a reduced speed of a first phase and a reduced speed of a second phase. 21. The method according to claim 20, comprising determining the sliding speed of the first phase relative to the second phase based on the average speed of the first phase and the average speed of the second phase. 22. The method according to item 21, including the provision of correction of the flow rate of the first phase and the flow rate of the second phase based on the given speeds, a specific flow mode or sliding speed. 23. The method according to any one of claims 14 to 22, wherein the first phase includes a gas and the second phase includes a liquid. 24. A flowmeter controller comprising
a density correction system configured to control to input the apparent density of the two-phase stream and output the adjusted density of the two-phase stream, wherein the two-phase stream includes a first phase and a second phase,
a mass flow correction system configured to control for inputting an apparent mass flow rate of a two-phase flow and outputting a corrected mass flow rate of a two-phase flow, and
a mass flow rate determination system for flow components configured to control the mass flow rate of the first phase based on the adjusted density and the adjusted mass flow rate and operable to control the mass flow rate of the second phase based on the adjusted density and the adjusted mass flow rate. 25. The flowmeter controller of claim 24, wherein the first phase includes a liquid and the second phase includes a gas. 26. The flowmeter controller of claim 25, comprising a phase fraction determination system configured to control to determine a corrected phase fraction of a two-phase stream, wherein the mass flow rate determination system of the flow components is configured to control a first phase flow rate and a second phase flow rate based on adjusted phase fractions. 27. The flowmeter controller of claim 26, wherein the phase fraction determination system is a gas content determination system that determines the amount of gas in a two-phase stream. 28. The flowmeter controller according to item 27, containing a system for determining the reduced speed, configured to control to determine the reduced speed of the first phase and the reduced speed of the second phase. 29. The flowmeter controller of claim 28, comprising a flow mode determination system configured to control to determine a two-phase flow mode of flow. 30. The flowmeter controller of claim 29, wherein the flow mode determination system is further operable to determine a phase slip speed relative to the average speed of the first phase and the average speed of the second phase. 31. The flowmeter controller of claim 30, wherein the mass flow rate determination system of the flow components is further configured to control to determine a first mass flow rate and a second mass flow rate based on reduced velocities, flow regime, or phase slip velocity. 32. A method for determining the flow rate of a fluid containing a gas phase and a liquid phase, comprising
the passage of fluid through an oscillating flow tube, the fluid including gas and liquid phases;
communicating vibrations to the flow tube while the fluid is passing through it using an oscillator connected to the flow tube and controlled to communicate movement to the flow tube;
receiving a sensor signal during oscillations of the flow tube, the sensor being connected to the flow tube and configured to measure the movement of the flow tube and generating a sensor signal;
organizing access to data related to the true volumetric gas content of the fluid;
determination of the density of the fluid mixture based on available data related to the true volumetric gas content, and
determining a first gas phase flow rate based on the determined mixture density and a received sensor signal or a second liquid phase flow rate based on the determined mixture density and the received sensor signal. 33. The method according to p. 32, in which the flow tube, sensor and oscillation generator form part of the Coriolis flow meter, and the organization of access data related to the true volumetric gas content of the fluid, provides for the organization of access data on the volumetric gas content measured by the volumetric gas meter located behind Coriolis flowmeter. 34. The method according to p, in which the density of the mixture, determined on the basis of the available data related to the true volumetric gas content, is the adjusted density of the mixture. 35. The method according to clause 34, in which the data related to the true volumetric gas content, include the apparent density difference, and determining the adjusted density of the mixture includes determining the apparent density of the mixture of the fluid based on the received sensor signal;
determination of the apparent density difference based on the apparent density of the mixture;
correction of apparent density drop to generate a corrected density drop, and
determination of the adjusted density of the mixture based on the adjusted density difference. 36. The method according to clause 35, in which the correction of the apparent density difference involves the input of the apparent density difference in a theoretical relationship that correlates the apparent density difference with the adjusted density difference. 37. The method according to clause 35, in which the correction of the difference in apparent density provides for the input of the difference in apparent density in an empirical dependence, which correlates the difference in apparent density with the adjusted density drop. 38. The method according to p, in which the data related to the true volumetric gas content, include data representing the true volumetric gas content. 39. A flow meter containing
a flow tube through which a fluid stream flows, including a gas phase and a liquid phase;
an oscillator connected to the flow tube and configured to communicate oscillations to the flow tube,
a sensor connected to the flow tube and configured to measure the movement of the flow tube and generate a sensor signal;
a controller configured to report vibrations to the flow tube while the fluid is passing through the flow tube using the oscillation generator; receiving a sensor signal during oscillations of the flow tube; access data related to the true volumetric gas content of the fluid; determining the density of the fluid mixture based on the available data relating to the true volumetric gas content; determining the mass flow rate of the gas phase based on the determined density of the mixture and the received sensor signal or the mass flow rate of the liquid phase based on the determined density of the mixture and the received sensor signal. 40. The flow meter according to clause 39, in which for accessing data related to the true volumetric gas content of the fluid, the controller is configured to access data representing the true volumetric gas content measured by a meter located outside the Coriolis flowmeter. 41. The flow meter according to clause 39, in which the density of the mixture, determined on the basis of the available data related to the true volumetric gas content, is the adjusted density of the mixture. 42. The flow meter according to claim 39, wherein the data relating to the true volumetric gas content includes an apparent density difference, and to determine the adjusted density of the fluid mixture based on the available data related to the true volumetric gas content, the controller is configured to determine the apparent the density of the fluid mixture based on the received sensor signal; determining the apparent density difference based on the apparent density of the mixture; adjusting the apparent density drop to generate a corrected density drop, and determining the adjusted density of the mixture based on the adjusted density drop. 43. The flow meter according to claim 42, wherein the controller is configured to correct an apparent density drop based on a theoretical relationship between the apparent density drop and the corrected density drop. 44. The flow meter according to claim 42, wherein the controller is configured to correct an apparent density difference based on an empirical relationship between an apparent density difference and a corrected density difference. 45. The flow meter according to claim 42, wherein the controller is configured to correct an apparent density difference based on a table storing the relationships between the apparent density difference and the adjusted density difference.

Images