HK1144014B

HK1144014B - Vibratory flow meter and method for correcting for entrained gas in a flow material

Info

Publication number: HK1144014B
Application number: HK10110341.3A
Authority: HK
Inventors: Joel Weinstein; Mark James Bell
Original assignee: Micro Motion, Inc.
Filing date: 2007-05-25
Publication date: 2012-10-05

Description

Vibratory flow meter and method for correcting for entrained gas in a flow material

Technical Field

The present invention relates to a vibrating flow meter and method, and more particularly to a vibrating flow meter and method for correcting for entrained gas in a flow material.

Background

Vibrating conduit sensors, such as Coriolis mass flowmeters and vibrating densitometers, typically operate by detecting motion of a vibrating conduit containing a flowing material. Properties related to the substance in the conduit, such as mass flow, density, etc., may be determined by processing measurement signals received from displacement sensors associated with the conduit. The vibration modes of a vibrating mass filled system are typically affected by the combined mass, stiffness and damping characteristics of the contained conduit and the mass contained therein.

A typical Coriolis mass flowmeter includes one or more conduits connected in a line or other transport system and carrying material, such as fluid, mud, etc., in the system. Each conduit can be viewed as having a set of natural vibration modes including, for example, simple bending, torsional, radial, and coupled modes. In a typical Coriolis mass flow measurement application, a conduit is excited in one or more vibration modes as a material flows through the conduit, and the motion of the conduit is measured at points spaced along the conduit. The excitation is typically provided by an actuator (e.g. an electromechanical device such as a voice coil type driver) which perturbs the conduit in a periodic manner. The mass flow rate may be determined by measuring the time delay or phase difference between the movements at the transducer locations. Two such transducers (or pickoff sensors) are typically used to measure the vibrational response of the flow tube or tubes, and are typically located at positions upstream and downstream of the actuator. The two pickup sensors are connected to the electronics by a cable connection, such as by two separate pairs of wires. The instrument receives signals from two pickup sensors and processes the signals to derive a mass flow rate measurement.

Flow meters are used to perform mass flow rate measurements for a wide variety of fluid flows. One area in which Coriolis flow meters may be used is in the metering of oil and gas wells. The products of these wells may include multiphase streams including oil or gas, and may include other components including, for example, water and air. It is highly desirable that even for such multiphase flows, the resulting metering be as accurate as possible.

The Coriolis meter provides high accuracy for single phase flow. However, when a Coriolis flowmeter is used to measure aerated or fluids with entrained gas, the accuracy of the meter may be significantly reduced. Entrained gas is typically present as bubbles in the flowing substance. The size of the bubbles may vary depending on the amount of gas present, the pressure of the flowing substance, the temperature and the degree of mixing in the line. The degree of performance degradation is not only related to the total amount of gas present, but also to the size of the individual bubbles in the flow. The size of the bubble can affect the measurement accuracy. Larger bubbles occupy a larger volume, resulting in fluctuations in the density of the flowing substance. Due to the compressibility of the gas, the gas volume of the gas bubble may vary, while its size does not necessarily vary. Conversely, if the pressure changes, the bubble size may change accordingly, expanding as the pressure decreases, or contracting as the pressure increases. This may also cause a change in the natural or resonant frequency of the flow meter.

Another problem caused by bubbles is slipping (slippage). When the flow meter is vibrated, small bubbles typically move with the liquid flow material. However, during vibration of the flow tube, larger bubbles do not move with the liquid. Instead, the bubbles may be decoupled from the liquid and move independently of the liquid. Thus, liquid may flow around the bubbles. This can adversely affect the vibrational response of the flow meter.

There remains a need in the art for a vibratory flow meter that detects problematic levels of entrained gas. There is also a need in the art for a vibratory flow meter that can accurately measure flow characteristics in the presence of entrained gas. There is also a need in the art for a vibratory flow meter that can accurately measure flow characteristics at any level of entrained gas.

Disclosure of Invention

In accordance with an embodiment of the present invention, a vibratory flow meter for correcting for entrained gas in a flow material is provided. A vibrating flow meter includes: a flow meter assembly configured to generate a vibrational response of a flow material; a bubble vibration sensor configured to generate a bubble measurement signal of the flow material; and meter electronics (meter electronics) coupled to the flow meter assembly and the bubble vibration sensor. The meter electronics is configured to receive the vibrational response and the bubble measurement signal, determine a bubble size of a bubble in the flow material using at least the bubble measurement signal, and determine one or more flow characteristics of the flow material using at least the vibrational response and the bubble size.

In accordance with an embodiment of the present invention, a vibratory flow meter for correcting for entrained gas in a flow material is provided. A vibrating flow meter includes: a flow meter assembly configured to generate a vibrational response of a flow material; a bubble vibration sensor configured to generate a bubble measurement signal of the flow material; and meter electronics coupled to the flow meter assembly and the bubble vibration sensor. The meter electronics is configured to receive the vibrational response and the bubble measurement signal, determine a bubble size of a bubble in the flow material using at least the bubble measurement signal, determine one or more flow characteristics of the flow material using at least the vibrational response, and generate an alarm indicating that the one or more flow characteristics have exceeded a predetermined measurement tolerance if the bubble size exceeds a predetermined size threshold.

According to an embodiment of the present invention, a method of correcting for entrained gas in a flowing substance is provided. The method comprises the following steps: determining a bubble size of a bubble in the flow material using at least the vibration measurement of the flow material; generating a vibrational response through the vibrating flow tube assembly; and determining one or more flow characteristics using at least the vibrational response and the bubble size.

According to an embodiment of the present invention, a method of correcting for entrained gas in a flowing substance is provided. The method comprises the following steps: determining a bubble size of a bubble in the flow material using at least the vibration measurement of the flow material; generating a vibrational response through the vibrating flow tube assembly; and determining one or more flow characteristics of the flowing substance using at least the vibrational response; and generating an alarm if the bubble size exceeds a predetermined size threshold, the alarm indicating that the one or more flow characteristics have exceeded a predetermined measurement tolerance.

Aspects of the invention

In one aspect of the vibratory flow meter, the bubble size sensor measures a bubble response to vibration of one or more bubbles in the flow material.

In yet another aspect of the vibratory flow meter, the bubble size sensor vibrates the flow material and subsequently measures a bubble response to the vibration.

In yet another aspect of the vibratory flow meter, the bubble size sensor acoustically (acoustically) vibrates the flow material and subsequently measures a bubble response to the vibration.

In yet another aspect of the vibratory flow meter, the bubble vibration sensor is separate and independent from the flow meter assembly.

In yet another aspect of the vibratory flow meter, the bubble vibration sensor is formed as part of a flow meter assembly.

In yet another aspect of the vibratory flow meter, the bubble vibration sensor comprises at least one pickoff sensor of the flow meter assembly.

In accordance with yet another aspect of the vibratory flow meter, determining the bubble size includes determining the bubble size of a substantially largest bubble in the flow material.

In yet another aspect of the vibratory flow meter, determining the bubble size further comprises determining the bubble size of bubbles in the flow material that exceed a predetermined size threshold.

In accordance with yet another aspect of the vibratory flow meter, the meter electronics are further configured to generate an alarm indicating that one or more flow characteristics have exceeded a predetermined measurement tolerance if the bubble size exceeds a predetermined size threshold.

In yet another aspect of the vibratory flow meter, further comprising generating a bubble size output.

In yet another aspect of the vibratory flow meter, generating an indication of changing flow conditions if the bubble size exceeds a predetermined size threshold is further included.

In yet another aspect of the vibratory flow meter, determining the one or more flow characteristics further comprises determining the one or more flow characteristics using at least the vibrational response and the bubble size only if the bubble size exceeds a predetermined size threshold.

In accordance with yet another aspect of the vibratory flow meter, generating the alarm further comprises generating a bubble size output indicative of a bubble size.

In accordance with yet another aspect of the vibratory flow meter, generating the alarm further comprises generating a bubble size output of substantially largest bubbles in the flow material.

In yet another aspect of the vibratory flow meter, generating the alarm further comprises generating a change flow condition indication if the bubble size exceeds a predetermined size threshold.

In accordance with yet another aspect of the vibratory flow meter, the meter electronics are further configured to determine one or more flow characteristics using at least the vibrational response and the bubble size.

According to one aspect of the method, determining the bubble size includes determining the bubble size of a substantially largest bubble in the flow material.

In accordance with yet another aspect of the method, determining the bubble size further comprises determining the bubble size of bubbles in the flow material that exceed a predetermined size threshold.

According to yet another aspect of the method, the method further comprises generating an alarm if the bubble size exceeds a predetermined size threshold, the alarm indicating that the one or more flow characteristics have exceeded a predetermined measurement tolerance.

In yet another aspect of the method, further comprising generating a bubble size output.

According to yet another aspect of the method, the method further comprises generating an indication of changing flow conditions if the bubble size exceeds a predetermined size threshold.

In accordance with yet another aspect of the method, determining the flow characteristic further includes determining the one or more flow characteristics using at least the vibrational response and the bubble size only if the bubble size exceeds a predetermined size threshold.

In accordance with yet another aspect of the method, generating an alert further comprises generating a bubble size output.

According to yet another aspect of the method, generating the alert further comprises generating a change flow condition indication if the bubble size exceeds a predetermined size threshold.

In accordance with yet another aspect of the method, the method further includes determining one or more flow characteristics using at least the vibrational response and the bubble size.

In accordance with yet another aspect of the method, determining the one or more flow characteristics further includes determining the one or more flow characteristics using at least the vibrational response and the bubble size only if the bubble size exceeds a predetermined size threshold.

Drawings

Fig. 1 shows a flow meter including a flow meter assembly and meter electronics.

Fig. 2 illustrates a vibratory flow meter according to an embodiment of the invention.

Fig. 3 illustrates a flow chart of a method of correcting for entrained gas in a flow material in a vibratory flow meter.

FIG. 4 is a graph of statistical bubble size distribution in a flow material.

Figure 5 shows a bubble of radius R moving relative to a fluid flow substance.

Fig. 6 shows displaced fluid volumes and bubbles before and after a slip in a fluid flow substance.

Fig. 7 illustrates a flow chart of a method of correcting for entrained gas in a flow material in a vibratory flow meter.

Fig. 8 illustrates a vibratory flow meter according to an embodiment of the invention.

Fig. 9 illustrates a vibratory flow meter according to an embodiment of the invention.

Detailed Description

Fig. 1-9 and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of the invention. Some conventional aspects have been simplified or omitted for the purpose of teaching inventive principles. Those skilled in the art will recognize from these examples variations that fall within the scope of the invention. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the invention. Therefore, the present invention is not limited to the specific examples described below, but only by the claims and their equivalents.

Fig. 1 shows a flow meter 5 including a flow meter assembly 10 and meter electronics 20. The meter electronics 20 is connected to the (flow) meter assembly 10 via a lead 100, and the meter electronics 20 is configured to provide measurements of one or more of density, mass flow rate, volume flow rate, aggregate mass flow, temperature, and other information over the communication path 26. It should be apparent to those skilled in the art that the present invention can be used in any type of Coriolis flowmeter, regardless of the number of drivers, pickoff sensors, flow conduits, or the mode of operation of the vibration. Additionally, it should be appreciated that the flow meter 5 may alternatively comprise a vibrating densitometer.

The flow meter assembly 10 includes a pair of flanges 101 and 101 ', manifolds 102 and 102 ', a driver 104, pickoff sensors 105 and 105 ', and flow tubes 103A and 103B. Drivers 104 and pickup sensors 105 and 105' are connected to flow tubes 103A and 103B.

In one embodiment, as shown, flow tubes 103A and 103B comprise substantially U-shaped flow tubes. Alternatively, in other embodiments, the flow tube may comprise a substantially straight flow tube. However, other shapes may be used and are within the scope of the description and claims.

Flanges 101 and 101 'are attached to manifolds 102 and 102'. The manifolds 102 and 102' may be attached to opposite ends of the spacer 106. Spacers 106 maintain the spacing between manifolds 102 and 102' to prevent unwanted vibrations in flow tubes 103A and 103B. When the flow meter assembly 10 is inserted into a piping system (not shown) carrying the flow material being measured, the flow material enters the flow meter assembly 10 through the flange 101, passes through the inlet manifold 102 where the entire quantity of flow material is directed to enter the flow tubes 103A and 103B, flows through the flow tubes 103A and 103B, and returns to the outlet manifold 102 'where it exits the flow meter assembly 10 through the flange 101'.

The flow tubes 103A and 103B are selected and appropriately mounted to the inlet and outlet manifolds 102 and 102 ' so as to have substantially the same mass distribution, moment of inertia, and modulus of elasticity about the bending axes W-W and W ' -W ', respectively. The flow tubes 103A and 103B extend outwardly from the manifolds 102 and 102' in a substantially parallel manner.

The flow tubes 103A and 103B are driven by the driver 104 in opposite directions about respective bending axes W and W' and in a first out of phase bending mode referred to as the flow meter 5. Driver 104 may comprise one of many well-known devices, such as a magnet mounted to flow tube 103A and an opposing coil (opposing coil) mounted to flow tube 103B. An alternating current is passed through the counter-acting coil to oscillate the two conduits. An appropriate drive signal is applied by the meter electronics 20 to the driver 104 via the conductor 110.

The meter electronics 20 receives the sensor signals on wires 111 and 111', respectively. Meter electronics 20 generates a drive signal on lead 110 that causes driver 104 to oscillate flow tubes 103A and 103B. The meter electronics 20 processes the left and right velocity signals from the pickoff sensors 105 and 105' to calculate the mass flow rate. The communication path 26 provides input and output devices that allow the meter electronics 20 to interface with an operator or with other electronic systems. The description of FIG. 1 is provided as an example of the operation of a Coriolis flowmeter only and is not intended to limit the teachings of the present invention.

A common problem in measuring one or more flow characteristics occurs when entrained air (or any gas) is present in the flowing substance. The entrained gas may be present as bubbles of different sizes. When the bubbles are relatively small, their effect on the flow measurement is negligible. However, as the bubble size increases, the error in flow measurement increases.

Fig. 2 shows a vibratory flow meter 99 according to an embodiment of the invention. The vibratory flow meter 99 includes a flow meter assembly 10, a bubble size sensor 50, and meter electronics 20. Meter electronics 20 is coupled to flow meter assembly 10 by leads 100. In the embodiment shown in this figure, the meter electronics 20 is coupled to the bubble size sensor 50 by one or more wires 51. The flow meter assembly 10 and bubble size sensor 50 can be coupled to a conduit 90 that conducts a flow material. The flow material may comprise a two-phase or multi-phase flow.

The flow meter 99 produces improved flow characteristic measurements. Flow characteristic measurements are improved when entrained bubbles are present in the flowing substance. For example, the flow meter 99 may generate an improved density measurement of the flow material. However, it should be understood that the flow meter 99 may additionally provide a flow rate measurement of the flow material. As a result, the flow meter 99 may comprise a vibrating densitometer and/or a Coriolis flow meter. Other additional flow measurements may be generated and are within the scope of the description and claims.

In one embodiment, meter electronics 20 is configured to vibrate flow tubes 103A and 103B. The vibration is performed by the driver 104. The meter electronics 20 further receives the resulting vibration signals from the pickup sensors 105 and 105'. The vibration signal includes the vibrational response of the flow tubes 103A and 103B. The meter electronics 20 processes the vibrational response and determines one or more flow characteristics such as density, mass, and/or volumetric flow rate.

The bubble size sensor 50 can comprise a substantial portion of the vibratory flow meter 99 and can be formed as part of the flow meter assembly 10. Alternatively, the bubble size sensor 50 may comprise a separate component that is separate and independent from the flow meter assembly 10. In another alternative, the bubble size sensor 50 may be part of the flow meter assembly 10 and may include at least one pickoff sensor 105 and/or 105' of the flow meter assembly 10.

The bubble size sensor 50 is configured to generate a bubble measurement signal of the flow material. The bubble size sensor 50 may measure a bubble response to vibration of one or more bubbles in the flow material and generate a bubble measurement signal from the bubble vibration response. The bubble size sensor 50 may passively detect bubble vibration. Alternatively, the bubble size sensor 50 may vibrate the flow material and then may measure the bubble response to the vibration.

In some embodiments, the vibration comprises an acoustic vibration. Alternatively, in other embodiments, the vibration is non-acoustic.

In some embodiments, the bubble size sensor 50 includes an active device that both generates and detects vibrations. The bubble size sensor 50 in this embodiment may vibrate the corresponding flow tube or flowing material and may receive the resulting vibration. The induced vibrations can be analyzed to determine bubble size of entrained gas in the flowing substance. The bubble size sensor 50 may alternatively vibrate the flow directly, for example through a port in the conduit. Alternatively, in other embodiments, the bubble size sensor 50 comprises a passive device that only detects and receives vibrations. The bubble size sensor 50 may detect vibration of a conduit, such as a conduit including the flow meter assembly 10, or may directly detect vibration of the flow material. The bubble size sensor 50 may receive vibrations generated by the flow of the flow material, where the vibrations may be processed to determine one or more bubble sizes.

The flow meter assembly 10 is configured to generate a vibrational response of the flow material. The meter electronics 20 may receive and process the bubble measurement signal and the vibrational response to, among other things, determine the bubble size. The meter electronics 20 may receive and process the bubble measurement signal and the vibrational response to determine a bubble size of a bubble in the flow material that exceeds a predetermined size threshold. The meter electronics 20 may receive and process the bubble measurement signal and the vibrational response to determine a bubble size of a substantially largest bubble in the flow material.

The meter electronics 20 may receive and process the bubble measurement signal and the vibrational response to determine one or more flow characteristics using at least the vibrational response and the bubble size (see FIG. 3 and related discussion). Alternatively, the meter electronics 20 may receive and process the bubble measurement signal and the vibrational response to generate an alarm when the bubble size exceeds a predetermined size threshold (see FIG. 7 and related discussion). Thus, the alarm may indicate that the flow characteristic has exceeded a predetermined measurement tolerance.

The meter electronics 20 can generate a bubble size output. In some embodiments, the bubble size output includes the size of one or more bubbles. In some embodiments, the bubble size output includes a bubble size of a substantially largest bubble in the flow material. The bubble size output may be stored and or communicated to an operator, or may be communicated to a remote location or device.

The meter electronics 20 may generate an indication of changing flow conditions when the bubble size exceeds a predetermined size threshold. The change flow condition indication may prompt an operator or technician to change the flow condition in the flow meter 99, such as by changing the flow rate, flow pressure, or other flow condition.

The meter electronics 20 may determine one or more flow characteristics based on the bubble size. For example, the bubble size may be correlated to a void fraction value and mass flow rate, or the volume flow rate may be adjusted accordingly. In some embodiments, the meter electronics 20 only determine one or more flow characteristics when the bubble size exceeds a predetermined size threshold.

The fluid model includes equations of motion for spherical Particles in oscillatory flow, such as those in "Bubbles, drags and Particles", n.y.academic Press, 1978, p.306-314, Clift r., Grace j.r., and Weber m.e., which are incorporated herein by reference. These equations are established by solving the unstable scholar (Stoke) equations and then using empirical corrections for the terms to account for the higher reynolds numbers, as may be found in some Coriolis flowmeter applications.

Fig. 3 illustrates a flow chart 300 of a method of correcting for entrained gas in a flow material in a vibrating flow meter. In step 301, bubble size is determined by taking bubble size measurements of one or more bubbles in the flow material. A bubble size sensor may be used to determine the bubble size. The bubble size may be determined using vibration bubble size measurement or acoustic bubble size measurement as previously discussed. After the discussion of flow diagram 300, the bubble size measurement will be discussed in detail below.

The bubble size in some embodiments includes the instantaneous bubble size. The bubble size in some embodiments comprises a substantially average bubble size. Bubble size in some embodiments includes a bubble size measurement of bubbles exceeding a predetermined size threshold. The bubble size in some embodiments comprises a substantially maximum bubble size. Since the largest bubbles in the flowing substance will have the greatest impact and shock on the measured flow characteristics, substantially the largest bubble size can be used.

In step 302, a vibrational response is generated by vibrating the flow tube assembly. The vibrational response may vary depending on the flow of the flow material in the flow tube assembly.

In step 303, one or more flow characteristics are determined using at least the vibrational response and the bubble size. The one or more flow characteristics may include, for example, a density of the flowing substance. The one or more flow characteristics may include, for example, a mass flow rate of the flowing substance. However, other flow characteristics are contemplated and are within the scope of the present description and claims.

The determination may provide a high level of accuracy of the one or more flow characteristics. For example, density measurements are known to be affected by entrained gas in a liquid flow material, also known as two-phase flow conditions, and therefore bubble size can be used to more accurately and reliably determine density. The bubble size (and optionally the number of bubbles) may be used to determine the substantially instantaneous gas volume in the flowing substance. The gas volume may be subtracted from the substantially instantaneous volume flow rate.

In some embodiments, the determining step may be based on the current bubble size. For example, if the detected bubble is not greater than a predetermined size threshold, the determination may optionally be performed using only the vibrational response. Conversely, when the bubble size exceeds a predetermined size threshold, then the determining step may use at least the vibrational response and the bubble size. The threshold may be set so that the determining step is only performed when the bubble size and entrained gas effects become significant.

Coriolis meters require that the flow material move completely with the flow tube during oscillation. This assumption is no longer valid when a bubble is introduced, since there is at least some relative motion or decoupling between the two phases. A fluid model for predicting the performance of a moving fluid may predict the decoupling effect in a Coriolis meter. In addition, the fluid model can be used to compensate for entrained gas in a flowing substance of known bubble size.

The bubble size in a pipe or conduit is a complex function of the line geometry, flow rate, and other fluid properties. The exact distribution of bubbles inside the meter can be measured in real time and decoupling (decoupling) errors can be compensated using a fluid model, which can allow improved measurement of entrained gas.

Several companies provide multi-phase flow Acoustic based Bubble size measurements, including the ABS Acoustic Bubble Spectrometer from Dynaflow corporation of Jussup, Maryland, and the StreamTeone product from CSIROManufacturing & Materials Technology, Clayton, Australia. The measurement principle is very simple. When each bubble encounters a pressure disturbance in the flow or a pressure disturbance from an external source, each bubble will oscillate radially at its natural frequency. The oscillation frequency (ω) of the first mode is primarily a function of bubble size and is expressed as follows:

wherein the term (a) is a bubble radius, (ρ) is a liquid density of the flow substance, (γ) is an adiabatic index of the flow substance, and (p) is a liquid pressure. The measurement involves exciting the bubbles with turbulence or by active excitation at certain frequencies, and then receiving and analyzing the returned frequencies.

For smaller bubbles, the vibration bubble size measurement may not be very accurate or reliable. However, it may be desirable to measure only bubbles that exceed a certain size, because smaller bubbles show a negligible effect on the accuracy of the flow meter.

FIG. 4 is a statistical bubble size distribution plot in a flow material. It is well known that the bubble distribution in a pipeline is well described by a lognormal distribution, which is significantly skewed for smaller diameters. This is advantageous as it means that there are only a few large bubbles containing the majority of the gas volume, as will be shown below. As with a normal distribution, the mean and standard deviation must be known to define the shape of the distribution. For the following derivation, these parameters represent typical water and air flow at moderate flow rates.

There are two control aspects regarding decoupling error in Coriolis flowmeters. The meter is affected by the volume of gas in the meter as it determines the amount of fluid decoupled as relative motion occurs between the two phases. In other words, the meter will not be concerned about how many bubbles are present, but rather about the volume of fluid that those bubbles displace. Second, if a bubble is so small that it will not decouple from the fluid, the bubble does not produce any error and need not be considered. From a decoupling point of view, only larger bubbles will be relevant. The effect of one 5mm diameter bubble may produce a larger error in the meter than hundreds of 0.5mm bubbles.

From a volume point of view, only a few larger bubbles in the distribution will be relevant, since these bubbles comprise almost all of the total volume. This is intuitive since the volume of a sphere is the cube of its radius.

However, when considering the actual decoupling predicted by the fluid model, there may be another transition to larger bubble sizes. The model predicts that there will be no decoupling for very small bubble sizes. Thus, for a typical lognormal distribution that has been skewed to a smaller size, many bubbles in the distribution will be locked out completely in synchrony with the fluid and no error in the mass flow or density measurement will occur.

It has been found that the bubble size corresponds to the oscillation frequency of the bubble. Thus, bubble size can be determined by detecting the vibrational response. If it is only desired to find the largest size, most significant bubble in the flow, a relatively low frequency signal somewhere in the range of 800-. This greatly exceeds most vibrations due to the pump and other components. As a result, the received vibrational response can be examined for a sharp increase in the received signal somewhere between 800-2000Hz, which would indicate a large bubble in the flow.

Assuming that the liquid properties are known and the size of the bubble in the meter is known, the amount of relative movement (i.e. decoupling) occurring in the meter can be calculated. Thus, the extent to which each bubble moves further than the liquid can be determined, which indicates exactly how much fluid moves back from the other direction in response to the movement of the bubble. This directly leads to a determination of the density error and the void fraction by simple equations. The method includes a center of gravity method. It should be understood that other methods are also contemplated as falling within the scope of the present description and claims.

FIG. 5 illustrates radii of movement of a substance relative to a fluid flowA bubble of R. The gas bubbles comprise spheres in a fluid medium. The fluid medium oscillates in synchronism with the flow tube. The radius of the particle is R, and the particle moves the total distance (A) with each oscillation of the tube from zero to the peak_p). The point of interest is the distance traveled by the bubble through the fluid, and not its absolute motion relative to the laboratory reference frame. The relative motion can be defined as (A)_p-A_f) Wherein (A)_f) Is the amplitude of the continuous fluid medium. Amplitude of flow (A)_f) Essentially the amplitude of the flow tube vibration is a known quantity.

The figure shows the bubble moving to one side from the midline of the tube motion to the maximum vibration amplitude (left position in the figure). The total volume affected by particles moving through the fluid from zero to peak amplitude is:

volume affected

However, the actual volume of liquid that is displaced does not include the volume of the bubble. Only the volume of liquid that is moved during the vibration of the flow tube is of interest, which is expressed as:

volume displaced (volume displaced) — (a)_p-A_f)(πR²) (3)

Use ofFrom this volume and the above figure, it can be seen that a barycentric analysis can be used to find the average displacement of the fluid in the path of the bubbles. When the bubble moves from zero to peak X_{Before one}Previously, the equation for the center of gravity of a displaced fluid was:

when the bubble moves from zero to peak X_{After that}The equation for the center of gravity of the displaced fluid is then:

thus, for each oscillation of the tube from zero to peak displacement, the volume (π R)²(A_p-A_f) Moving average distance

Figure 6 shows the volume of fluid and bubbles displaced before and after slippage occurs in the fluid flow material. The term (X) is the center of gravity of the displaced fluid volume. The figure shows the movement of the centre of gravity (X) due to slippage. The movement of the center of gravity (X) occurs in opposition to the vibration of the flow tube.

However, the amount of fluid displaced backwards is not known to be useful for determining the effect on density measurements. Instead, it is necessary to move the equivalent volume backwards the same distance as the tube moves forwards, in order to produce the same change in the center of gravity. It can then be assumed that the volume does not participate in the oscillation of the tube and that the mass contained in the volume is not reflected in the density measurement. This includes conservation of volume calculations, assuming that the volume of the bubble does not change during oscillation. The following calculation yields volumes that do not participate (non-localization):

or:

the volume not participating includes the particle volume times the ratio of the relative particle displacement to the tube displacement. Summing all particles in the tube, the result can be in terms of void fraction To show that:

or:

the result reflects a shift to the right (A)_p-A_f) And a liquid ball that moves the same distance to the left. The same method and equations can be further used to derive the non-participating volumes.

The actual density (ρ) can be established as follows_actual) And has a decoupled density (p)_decoupled) The equation of (c):

ρ_actual＝ρ_f(1-Γ)+ρ_pΓ (10)

the density error can be calculated as the difference between the decoupled density and the actual density divided by the actual density:

as long as the particles move relatively A_pThe term is known from the fluid model, and the equation gives the density error directly. The bubble size measurements and known flow material fluid properties provide the information needed for the fluid model. With this information, the density output of the meter can be corrected. Furthermore, since the actual liquid density is already known from the flowing matter fluid properties, this information can further be used to determine the void fraction Γ.

The use of bubble size measurement provides a completely independent measurement that can be used to detect the presence of gas in a very robust manner. This technique not only allows gas to be detected, but can also provide an estimate of the extent to which entrained gas affects flow measurements.

Fig. 7 illustrates a flow chart 700 of a method of correcting for entrained gas in a flow material in a vibratory flow meter. In step 701, the bubble size is determined, as previously discussed.

In step 702, a vibrational response is generated by vibrating the flow tube assembly. One or more flow characteristics of the flowing substance are determined using at least the vibrational response. The determining may further include using the bubble size.

In step 703, the bubble size is compared to a predetermined size threshold. The predetermined size threshold in some embodiments may comprise an acceptable entrained gas threshold. If the bubble size is less than or equal to the predetermined size threshold, the bubble size is acceptable and the method bypasses step 704 and exits. If the bubble size is greater than the predetermined size threshold, the bubble size is unacceptable and the method proceeds to step 704.

In step 704, an alert is generated. The alarm indicates that one or more flow characteristics have exceeded a predetermined measurement tolerance. For example, if the bubbles are too large, the density measurement of the flowing substance may be adversely affected and the accuracy of the density measurement may be unacceptable due to entrained gas. Other flow characteristics may also be degraded by entrained gas.

Generating the alarm may include setting an alarm condition in the meter electronics 20. Generating an alarm may include transmitting an alarm condition or indication to other devices, such as a monitoring system. Generating an alert may include generating any manner of visual alert or audio alert.

Generating the alert may further include transmitting, displaying, or otherwise indicating the bubble size, such as generating a bubble size output. The bubble size may include the largest bubble size. Alternatively, the bubble size output may include a representative bubble size or an average bubble size.

In some embodiments, generating the alert may further include generating a blending indication indicating a need to change the flow condition. In some embodiments, generating the alert may further include changing the flow condition. For example, the flow material pressure may be increased to reduce entrained gas errors. The increased pressure may reduce the bubble size. Alternatively, the flow rate may be increased in order to break up the bubbles and provide a mixing action. In another alternative, a mixing action may be initiated in order to break up the bubbles or otherwise reduce the bubble size. The mixing indication may prompt a change in flow conditions in order to break up the bubbles or otherwise reduce the bubble size.

Fig. 8 illustrates a vibratory flow meter 99 according to an embodiment of the invention. The vibratory flow meter 99 in this embodiment includes meter electronics 20 and a meter assembly 10. The meter assembly 10 includes flow tubes 103A and 103B, a driver 104, and pickup sensors 105 and 105'. As before, the meter assembly 10 is coupled to the meter electronics 20 by a wire 100. Further, the bubble size sensor 50 may comprise a portion of the flow meter assembly 10 and may be coupled to the meter electronics 20 by a link 51. The bubble size sensor 50 of the present embodiment may be located anywhere on the flow meter assembly 10 or alternatively may extend into the flow tube of the flow meter assembly 10. In some embodiments, the bubble size sensor 50 may comprise a vibration pickup or sensor attached to or part of the flow tube.

Fig. 9 illustrates a vibratory flow meter 99 according to an embodiment of the invention. The vibratory flow meter 99 in this embodiment employs one of the pickoff sensors 105 as both a pickoff sensor and a bubble size sensor 50. Thus, the flow meter assembly 10 is coupled to the meter electronics 20 by the leads 100. The lead 100 conveys both the vibrational response and the bubble size measurement.

The vibratory flow meter and method according to the invention can be employed according to any of the embodiments to provide a number of advantages, if desired. The vibratory flow meter and method can be used to determine accurate flow characteristics. The vibratory flow meter and method can be used to determine one or more measured flow characteristics when entrained gas is present in a flow material. The vibratory flow meter and method can be used to determine flow characteristics obtained from a flow meter assembly only when a bubble size exceeds a size threshold.

The vibratory flow meter and method can be used to determine bubble size. The vibratory flow meter and method can be used to determine a bubble volume. The vibratory flow meter and method can be used to determine the amount of entrained gas, including the volume of entrained gas. The vibratory flow meter and method can be used to determine a void fraction in a flow material.

The vibratory flow meter and method can be used to determine bubbles larger than a critical size. The vibratory flow meter and method can be used to determine the volume of a critical bubble. The vibratory flow meter and method can be used to generate an alarm when a bubble size exceeds a size threshold. The vibratory flow meter and method can be used to generate a bubble size output. The vibratory flow meter and method can be used to generate an indication of changing flow conditions when the bubble size exceeds a size threshold.

Claims

1. A vibratory flow meter (99) for correcting for entrained gas in a flow material, comprising:

a flow meter assembly (10) configured to generate a vibrational response of a flow material;

a bubble size sensor (50) configured to generate a bubble measurement signal of the flow material; and

meter electronics (20) coupled to the flow meter assembly (10) and the bubble size sensor (50) and configured to receive the vibrational response and the bubble measurement signal, determine a bubble size of a bubble in the flow material using at least the bubble measurement signal, and determine one or more flow characteristics of the flow material using at least the vibrational response and the bubble size.

2. The vibratory flow meter (99) of claim 1, with the bubble size sensor (50) measuring a bubble response to vibration of one or more bubbles in the flow material.

3. The vibratory flow meter (99) of claim 1, with the bubble size sensor (50) vibrating the flow material and subsequently measuring a bubble response to the vibration.

4. The vibratory flow meter (99) of claim 1, with the bubble size sensor (50) acoustically vibrating the flow material and subsequently measuring a bubble response to the vibration.

5. The vibratory flow meter (99) of claim 1, with the bubble size sensor (50) being separate and independent from the flow meter assembly (10).

6. The vibratory flow meter (99) of claim 1, with the bubble size sensor (50) being formed as part of the flow meter assembly (10).

7. The vibratory flow meter (99) of claim 1, with the bubble size sensor (50) comprising at least one pickoff sensor (105) of the flow meter assembly (10).

8. The vibratory flow meter (99) of claim 1, with determining the bubble size comprising determining a bubble size of a substantially largest bubble in the flow material.

9. The vibratory flow meter (99) of claim 1, with determining the bubble size further comprising determining a bubble size of a bubble in the flow material that exceeds a predetermined size threshold.

10. The vibratory flow meter (99) of claim 1, with the meter electronics (20) being further configured to generate an alarm if the bubble size exceeds a predetermined size threshold, with the alarm indicating that the one or more flow characteristics have exceeded a predetermined measurement tolerance.

11. The vibratory flow meter (99) of claim 1, further comprising generating a bubble size output.

12. The vibratory flow meter (99) of claim 1, further comprising generating a change flow condition indication if the bubble size exceeds a predetermined size threshold.

13. The vibratory flow meter (99) of claim 1, with determining the one or more flow characteristics further comprising determining the one or more flow characteristics using at least the vibrational response and the bubble size only if the bubble size exceeds a predetermined size threshold.

14. A vibratory flow meter (99) for correcting for entrained gas in a flow material, comprising:

a flow meter assembly (10) configured to generate a vibrational response of the flow material;

meter electronics (20) coupled to the flow meter assembly (10) and the bubble size sensor (50) and configured to receive the vibrational response and the bubble measurement signal, determine a bubble size of a bubble in the flow material using at least the bubble measurement signal, determine one or more flow characteristics of the flow material using at least the vibrational response, and generate an alarm if the bubble size exceeds a predetermined size threshold, wherein the alarm indicates that one or more flow characteristics have exceeded a predetermined measurement tolerance.

15. The vibratory flow meter (99) of claim 14, with the bubble size sensor (50) measuring a bubble response to vibration of one or more bubbles in the flow material.

16. The vibratory flow meter (99) of claim 14, with the bubble size sensor (50) vibrating the flow material and subsequently measuring a bubble response to the vibration.

17. The vibratory flow meter (99) of claim 14, with the bubble size sensor (50) acoustically vibrating the flow material and subsequently measuring a bubble response to the vibration.

18. The vibratory flow meter (99) of claim 14, with the bubble size sensor (50) being separate and independent from the flow meter assembly (10).

19. The vibratory flow meter (99) of claim 14, with the bubble size sensor (50) being formed as part of the flow meter assembly (10).

20. The vibratory flow meter (99) of claim 14, with the bubble size sensor (50) comprising at least one pickoff sensor (105) of the flow meter assembly (10).

21. The vibratory flow meter (99) of claim 14, with determining the bubble size comprising determining a bubble size of a substantially largest bubble in the flow material.

22. The vibratory flow meter (99) of claim 14, with determining the bubble size further comprising determining a bubble size of a bubble in the flow material that exceeds a predetermined size threshold.

23. The vibratory flow meter (99) of claim 14, with generating the alert further comprising generating a bubble size output.

24. The vibratory flow meter (99) of claim 14, with generating the alert further comprising generating a change flow condition indication if the bubble size exceeds the predetermined size threshold.

25. The vibratory flow meter (99) of claim 14, with the meter electronics (20) being further configured to determine the one or more flow characteristics using at least the vibrational response and the bubble size.

26. The vibratory flow meter (99) of claim 25, with determining the one or more flow characteristics further comprising determining the one or more flow characteristics using at least the vibrational response and the bubble size only if the bubble size exceeds the predetermined size threshold.

27. A method of correcting for entrained gas in a flow material in a vibratory flow meter, the method comprising:

determining a bubble size of bubbles in the flow material using at least the vibration measurements of the flow material;

generating a vibrational response through the vibrating flow tube assembly; and

determining one or more flow characteristics using at least the vibrational response and the bubble size.

28. The method of claim 27, wherein determining the bubble size comprises determining a bubble size of a substantially largest bubble in the flow material.

29. The method of claim 27, wherein determining the bubble size further comprises determining a bubble size of bubbles in the flow material that exceed a predetermined size threshold.

30. The method of claim 27, further comprising generating an alarm if the bubble size exceeds a predetermined size threshold, wherein the alarm indicates that one or more flow characteristics have exceeded a predetermined measurement tolerance.

31. The method of claim 27, further comprising generating a bubble size output.

32. The method of claim 27, further comprising generating a change flow condition indication if the bubble size exceeds a predetermined size threshold.

33. The method of claim 27, wherein determining the flow characteristic further comprises determining the one or more flow characteristics using at least the vibrational response and the bubble size only if the bubble size exceeds a predetermined size threshold.

34. A method of correcting for entrained gas in a flow material in a vibratory flow meter, the method comprising:

generating a vibrational response by vibrating the flow tube assembly and determining one or more flow characteristics of the flow material using at least the vibrational response; and

generating an alarm if the bubble size exceeds a predetermined size threshold, wherein the alarm indicates that the one or more flow characteristics have exceeded a predetermined measurement tolerance.

35. The method of claim 34, wherein determining the bubble size comprises determining a bubble size of a substantially largest bubble in the flow material.

36. The method of claim 34, wherein determining the bubble size further comprises determining a bubble size of bubbles in the flow material that exceed a predetermined size threshold.

37. The method of claim 34, wherein generating an alert further comprises generating a bubble size output.

38. The method of claim 34, wherein generating an alert further comprises generating a change flow condition indication if the bubble size exceeds the predetermined size threshold.

39. The method of claim 34, further comprising determining the one or more flow characteristics using at least the vibrational response and the bubble size.

40. The method of claim 39, wherein determining the one or more flow characteristics further comprises determining the one or more flow characteristics using at least the vibrational response and the bubble size only if the bubble size exceeds the predetermined size threshold.