Multi-fluid detection and counting in vortex flow meters

Abstract

The vortex flowmeter (100) includes a flow tube (102) configured to receive a process fluid flow. A shedder bar (118) is disposed within the flow tube (102) and configured to generate vortices in the process fluid flow. A vortex sensor (144) is positioned to detect vortices in the process fluid flow generated by the shedder bar (118). Measurement electronics (202) are operatively coupled to the vortex sensor (144) to detect an analog signal from the vortex sensor (144) and provide a digital reading related to the analog signal. A processor (200) is configured to receive the digital reading and calculate a speed of the process fluid flow based on a frequency of the digital reading. The processor (200) is further configured to measure the amplitude of the digital reading and estimate a density of the process fluid based on the measured amplitude. The processor (200) is further configured to determine a fluid type based on the measured amplitude and assign a flow rate unit corresponding to the calculated speed to a fluid totalizer corresponding to the detected fluid type.

Description

[Technical Field]

[0001] background Fluid flow through pipes or conduits is often measured to control the flow or monitor the amount of fluid passing through the conduit. Various methods exist for measuring the flow rate of a fluid through a conduit. These methods include measuring the differential pressure across an obstruction to the fluid flow, using a magmeter, and using a vortex flow meter. These various devices and techniques generally use different techniques to detect characteristics of the fluid flow. In some cases, the velocity of the fluid is measured, and sometimes the mass flow rate is calculated based on that. Summary of the Invention

[0002] The embodiments described below relate generally to flow meters, and more particularly to vortex flow meters. Vortex flow meters use an operating principle based on the vortex shedding phenomenon known as the von Karman effect. As fluid passes through a bluff body or shedder bar, it separates and generates small vortices or eddies that alternately migrate along each side of the bluff body and behind it. These vortices result in regions of fluctuating pressure that are detected by a sensor. The frequency of the vortex shedding is essentially proportional to the fluid velocity. These vortices can be detected using a vortex diaphragm.

[0003] overview The vortex flow system includes a flow tube configured to receive a process fluid flow. A shedder bar is disposed within the flow tube and configured to generate vortices in the process fluid flow. A vortex sensor is positioned to detect vortices in the process fluid flow generated by the shedder bar. Measurement electronics are operatively coupled to the vortex sensor and configured to detect an analog signal from the vortex sensor and provide a digital reading related to the analog signal from the vortex sensor. A processor is configured to receive the digital reading and calculate a velocity of the process fluid flow based on a frequency of the digital reading. The processor is also configured to measure an amplitude of the digital reading and estimate a density of the process fluid based on the measured amplitude. The processor is further configured to determine a fluid type based on the measured amplitude and assign a flow rate unit corresponding to the calculated velocity to a fluid totalizer corresponding to the detected fluid type. [Brief explanation of the drawings]

[0004] [Figure 1] 1 is a schematic perspective view of a vortex flow meter to which embodiments of the present invention are particularly applicable; FIG. [Figure 2] A side cross-sectional view of a vortex flow meter is shown. [Figure 3] FIG. 1 is a block diagram of a transmitter circuit 142 according to an embodiment of the present invention. [Figure 4] 1 is a graph illustrating the differences between gas and liquid filters and signals in a vortex flow meter according to an embodiment of the present invention. [Figure 5] 1 is a flow diagram illustrating dual measurement filters used for gas and liquid flows in a vortex flow meter according to an embodiment of the present invention. [Figure 6] 1 is a flow diagram of a method for tallying two fluids with different densities but the same phase using a vortex flow meter according to an embodiment of the present invention. [Figure 7] FIG. 1 is a schematic diagram of a vortex flow meter using a 4-20 mA signal to communicate flow values ​​for multiple fluids over a 4-20 mA signal loop. DETAILED DESCRIPTION OF THE INVENTION

[0005] Some process applications have multiple fluids passing through a conduit at different times. Examples of such applications include plunger lift, water after gaseous carbon dioxide is saturated, or steam scrubbing of hydrocarbon streams in chemical plants or refineries. In many of these applications, it can be useful to measure only one of each fluid, or to measure each fluid in a way that aggregates them into two separate aggregate values.

[0006] Another challenge that can arise in process fluid flow sensing is that during system manufacturing or configuration, not enough information about the actual fluid(s) the flow meter will measure may be available. Given this challenge, a vortex flow meter that can automatically detect the process fluid type (gas vs. liquid) and default the meter to that type of process fluid would offer great value.

[0007] Vortex flow meters essentially measure the velocity of a fluid in a conduit by detecting the frequency of vortices generated by a shedder bar. The shedder bar also generates a density reading via the amplitude of the vortex generation signal, which is directly proportional to the density and the square of the velocity. In some embodiments described below, density measurements are used to distinguish between two fluids, allowing the user to count only one fluid. This can be accomplished using a simple density calibration during manufacturing, or by providing the flow meter with the expected densities or relative differences between the densities and allowing the flow meter to self-calibrate in the application.

[0008] As described in detail below, vortex flow meters according to embodiments of the present invention have options for a first fluid (Fluid 1) and a second fluid (Fluid 2), with each fluid having an assignable totalizer. For example, if the process application is plunger lift, an expected fluid with a density of 62.4 lb / ft3 and 0.75 lb / ft3 can be input into the vortex flow meter, or the vortex flow meter can be configured to expect a typical gas and liquid as the two fluids. The vortex flow meter then measures the velocity and approximate density of the fluid based on the frequency and amplitude of the vortices. The vortex flow meter determines the fluid density based on the amplitude of the vortex sensor signal. Based on the fluid density, the vortex flow meter determines whether the fluid is a liquid or a gas. After determining whether the fluid is a liquid or a gas, the vortex flow meter assigns the measured flow rate to the totalizer assigned to that particular fluid.

[0009] 1 is a schematic perspective view of a vortex flow meter to which embodiments of the present invention are particularly applicable. Vortex flow meter 100 includes a flow tube 102 disposed between a pair of pipe flanges 106, 108 configured for attachment to corresponding process piping. A vortex transmitter 140 is shown positioned above flow tube 102 and including transmitter circuitry 142 disposed therein. Transmitter circuitry 142 is configured to detect vortices via a vortex sensor disposed within flow tube 102 and provide a flow rate output.

[0010] 2 shows a side cross-sectional view of a vortex flowmeter 100. The vortex flowmeter 100 includes a flow tube 102 for conveying a fluid flow 104 of a fluid therethrough. The flow tube 102 includes a curved, cylindrical sidewall 103. The fluid flow 104 may include a liquid or a gas. Pipe flanges 106, 108 are coupled to the flow tube 102. The pipe flanges 106, 108 include bolt holes, such as bolt holes 110, 112, for attachment to a fluid piping system with bolts (not shown). The pipe flanges 106, 108 include sealing surfaces 114, 116 for sealing to mating flanges of the fluid piping system.

[0011] The vortex flowmeter 100 includes a shedder bar 118 within the flow tube 102. The shedder bar 118 includes a bluff body shape. The shedder bar 118 is attached to the flow tube 102 at an upstream location 120. As the fluid stream 104 flows past the shedder bar 118, multiple vortices are generated within the fluid stream 104. Each vortex is referred to as a von Karman vortex street. Each vortex is introduced as the fluid stream 104 passes through a downstream location 122. The downstream location 122 is located downstream of the upstream location 120.

[0012] The flow tube 102 includes an opening 124 in the side wall 103. The vortex flow meter 100 includes a mechanism 126 that extends through the opening 124. The mechanism 126 seals the opening 124 so that fluid within the flow tube 102 does not leak through the opening 124. The mechanism 126 extends into the fluid stream 104 and detects vortices at a downstream location 122. The mechanism 126 detects vortices within the fluid stream 104 and transfers the mechanical motion of the vortex to a location 128 outside the fluid stream 104. The mechanism 126 is not part of the shedder bar 118. The mechanism 126 is spaced a fixed distance downstream from the shedder bar 118.

[0013] Vortex flowmeter 100 includes transmitter 140. Transmitter 140 includes an electronic transmitter circuit 142 as well as a mechanical sensor 144 that detects mechanical motion at location 128 and provides an electrical sensor signal representative of the mechanical motion. Mechanical sensor 144 is coupled to electronic transmitter circuit 142 by lead 146 to provide the electrical sensor signal. Electronic transmitter circuit 142 converts the electrical sensor signal into a standardized transmit signal provided on output lead 148. Electronic transmitter circuit 142 provides an output corresponding to fluid flow 104 passing through flowtube 102 based on the detected oscillations of the von Karman vortex street. Mechanical sensor 144 detects vortex oscillations at sensing location 128 and provides a sensor output on lead 146. Electronic transmitter circuit 142 receives the sensor output from mechanical sensor 144 and outputs the standardized transmit signal on output lead 148. According to one embodiment, the standardized transmit signal comprises a 4-20 milliamp two-wire transmit output signal. According to another embodiment, the 4-20 mA signal provides all power for the electronic transmit circuitry 142 and the mechanical sensor 144. In such an embodiment, the lead 148 can comprise a two-wire process control loop that both powers the device and carries data over the same two conductors.

[0014] FIG. 3 is a block diagram of the transmitter circuit 142 according to an embodiment of the present invention. As shown in FIG. 3, the transmitter circuit 142 includes a processor 200. The processor 200 can be any suitable device or logic configured to obtain one or more readings from a measurement electronics circuit 202 and provide a useful indication of the flow rate of the process fluid. By way of example, the processor 200 is a microprocessor. The processor 200 can include or be coupled to a measurement electronics circuit 202 configured to detect an analog value, such as a voltage, and provide a digital reading thereof to the processor 200. The measurement electronics circuit 202 can include additional amplification, linearization, and / or filtering circuitry, as needed. The measurement electronics circuit 202 is electronically coupled to the vortex sensor 144 and configured to convert the electrical sensor signal into a digital signal for processing by the processor 200.

[0015] 3 also shows the transmit circuit 142, which includes a power module 204. The power module 204 is configured to provide appropriate voltage levels and current protection to each internal component of the circuit 142, as indicated by arrow 206. In embodiments in which the vortex flowmeter is fully powered by the connector through which it communicates, the power module 204 can be configured to remove a selected amount of power, e.g., 4-20 mA, from or to the power supply of the internal components of the circuit 142.

[0016] The communications module 208 is coupled to the processor 200 and configured to communicate with at least one external device using a process industry standard communications protocol. Examples of such protocols include the Highway Addressable Remote Transducer (HART®) protocol, the FOUNDATION™ Fieldbus protocol, PROFIBUS, Modbus, and Controller Area Network (CAN). In one configuration, the communications loop is a wireless process control loop in which data is transmitted wirelessly, for example, using radio frequency (RF) communications. One such wireless process communications protocol is the WirelessHART protocol (IEC 62591).

[0017] The transmitter circuit 142 also includes an input / output module 210 configured to drive a local display, if one is provided in the vortex flowmeter. Additionally, the input / output module 210 may include appropriate circuitry for coupling to one or more user interface buttons or knobs to allow a user to interact with the transmitter circuit 142 in the field.

[0018] 4 is a graph showing the differences between gas and liquid filters and signals in a vortex flow meter according to an embodiment of the present invention. As shown in FIG. 4, at any given velocity (corresponding to frequency, regardless of whether it is gas or liquid), there is a significant difference in the signal as the signal amplitude increases.

[0019] The methods for measuring the injection rates of supercritical carbon dioxide and water are similar. For example, in the Permian Basin of West Texas and Eastern New Mexico, carbon dioxide, with a density of approximately 50 pounds per cubic foot, is injected into oil wells to enhance oil recovery. After a few days, the process fluid is changed to water injection. Although their densities only differ by 20%, it is readily apparent on an oscilloscope which fluid is in the pipe. Therefore, this determination can also determine which fluid is passing through the vortex flow meter. Typically, switching from one fluid to another is a manual process, requiring the blocking of one line and the opening of another. In some cases, the control room may not know whether the valve operator made the switch, or may mistakenly believe that water is being pumped into the reservoir when in fact carbon dioxide is being injected. Using the embodiments described herein and two independent totalizers, the control room can periodically read the values ​​of the individual totalizers via process communications and always have the accurate total amount of each fluid.

[0020] Density measurements can be made using either absolute or relative density measurements. For gases and liquids, it may be possible to identify which fluid is flowing through a conduit using an uncalibrated sensor because vortex sensors can exhibit ±30% variation in output signal amplitude for a given input from one sensor to another, and because gas and liquid densities tend to differ by more than a magnitude indication, for a given sensor, relative signal amplitude reflects density better than ±5-7%. For supercritical carbon dioxide / water mixtures, it may be beneficial to factory calibrate the vortex signal amplitude for each density of the fluid.

[0021] Alternatively, a training mode can be used for the vortex flowmeter. During training, the transmitter of the vortex flowmeter stores the predicted density value of each fluid. As each fluid cycle passes through the vortex flowmeter, the transmitter knows which fluid was which. Embodiments include other options. In yet another possible embodiment, the user provides the transmitter with information about which fluid first passed through the vortex flowmeter, and the transmitter can then calibrate that fluid. In yet another option, no user input is required; the transmitter estimates the identity of the first fluid and then checks whether that estimate is correct when the second fluid begins to pass. In this mode, the first totalizer is assigned by default to the higher density fluid, and the second totalizer is assigned to the lower density fluid. In such a case, only one cycle of the first fluid may be erroneously recorded, at least temporarily, but the vortex flowmeter can switch when it determines that the first fluid is the lower density fluid.

[0022] The embodiments described herein can be implemented as code to create a user-friendly experience for users of vortex flow meters. In one embodiment, the user is provided with a configurable section to provide the expected density and fluid name. Assuming the vortex flow meter is not calibrated, the average density can be measured, and the totalizer can be digitally reassigned the first time the density changes. There does not need to be a set of fluids to find, just high-density and low-density registers for the totalizer. This potentially leaves periods where no totalizer is assigned, but the user will likely have an idea of ​​what the total represents. This embodiment provides minimal setup. In situations where one fluid is liquid and one fluid is gas, there are some additional challenges with setting up the filter. Currently, most vortex flow meters require the user to determine whether they want to measure gas or liquid, and the filter within the vortex flow meter is then adjusted by an order of magnitude in frequency depending on which fluid is selected. This is based on previous technology and processing speed. With modern processing speeds, it is now possible to apply both gas and liquid filters to multiple copies of the vortex shedding signal data after it has been digitized. In this way, fluids in either gas or liquid state can be measured. For high-velocity liquid flow rates, the gas filter setting also allows the flow meter to register the flow rate. In this case, the flow meter performs a density measurement to determine that the fluid is a liquid and excludes it from the count in the gas setting.

[0023] FIG. 5 is a flow diagram illustrating a dual measurement filter used for gas and liquid flows in a vortex flow meter according to an embodiment of the present invention. Method 300 begins at block 302, where an analog sensor signal is received from the vortex sensor. This signal is provided to an analog-to-digital converter, which converts the analog reading into a digital reading, as shown in block 304. Next, at block 306, the digital data is duplicated into two copies. As shown in block 308, the first copy of the digital data is provided to a first digital filter configured for liquids. As shown in block 316, the second copy of the digital data is provided to a second digital filter configured for gases. Returning to block 308, after the digital filter is applied to the digital data, the filtered output is sent to block 310, where a second filter pass is performed on the liquid filtered data to calculate density. The output of the second filter pass is then tested at block 312 to determine whether there is a flow signal above a low flow cutoff value. If so, the flow rate signal is added to totalizer A, as shown in block 314 .

[0024] Returning to block 316, the gas filtered digital data from block 316 is passed to block 318, where a second filter pass is performed to calculate density. The output from the second filter pass is tested in block 320 to determine if there is a flow rate and gas density above the low flow cutoff value. If so, control is passed to block 322, where the flow rate signal is added to totalizer B. As can be appreciated, once these flow rate signals have been added to their respective totalizers, the method repeats by obtaining another sensor signal in block 302. This type of configuration is useful in applications such as plunger lift or chemical plants where hydrocarbon liquids may follow a vapor stream.

[0025] In processes where both fluids are liquids, the vortex transmitter increments totalizer A or B based on a threshold density. In such cases, the filter can be fixed in liquid (or gas) mode and the threshold is determined either via user configuration or via an algorithm that determines an initial average density and calculates the threshold at some safe distance based on the assumed device resolution.

[0026] FIG. 6 is a flow diagram of a method for tallying two fluids with different densities but the same phase using a vortex flow meter, according to an embodiment of the present invention. Method 400 begins at block 402, where an analog sensor signal is obtained from the vortex sensor. Once the analog signal is obtained, it is provided to an analog-to-digital converter, which converts the analog signal into a digital representation thereof, as shown in block 404. Next, at block 406, the digital representation of the vortex sensor signal is filtered using a filter configured for the liquid. The output of the filter configured for the liquid is passed to block 408, where a second filter pass is obtained to calculate density. Next, at block 410, the density is tested to see if it exceeds a threshold value for fluid A. If the density does not exceed the threshold value for fluid A, control is passed to block 412, where the flow rate signal is added to totalizer B. However, if the density exceeds the threshold value for fluid A, control is passed to block 414, where the flow rate signal is added to totalizer A. Similar to FIG. 5, method 400 repeats at block 402 by acquiring another sensor signal until the totalizer signal has increased appropriately.

[0027] As can be appreciated, multiple totalizer values ​​can be communicated relatively easily, and the vortex flowmeter can communicate digital signals using the communications module 208 (shown in FIG. 3) and use process communications or local outputs to provide fluid labels, either Fluid A and Fluid B, Gas and Liquid, or User Label 1 and User Label 2, which are input via process communications. For analog readings of flow values, the flow rate of each fluid can be sent over a 4-20 mA loop, with the vortex flowmeter configured to output 12 mA as a zero flow reading, with one fluid being represented as 4-12 mA and the second fluid being represented in the 12-20 mA range.

[0028] Figure 7 is a schematic diagram of a vortex flow meter that uses a 4-20 mA signal to communicate flow values ​​for multiple fluids through separate 4-20 mA loops. As shown in Figure 7, a 12 mA signal represents zero flow for all fluids. As the 4-20 mA signal decreases from a value of 12 mA, the percentage of range for fluid 1 increases linearly from 0% to 100% at 4 mA. Similarly, as the 4-20 mA signal increases from 12 mA to 20 mA, the percentage of flow range for fluid 2 increases linearly from 0% at 12 mA to 100% at 20 mA. While this method halves the rate accuracy from an analog perspective, this communication method is very useful for users without digital communication capabilities in their control systems.

[0029] While the above-described embodiments have been described with respect to a vortex flowmeter capable of measuring two different fluids, one gas and the other liquid, those skilled in the art will appreciate that the embodiments are also applicable to vortex flowmeters that potentially measure three or more different fluids. Furthermore, embodiments of the present invention can also be implemented where the vortex flowmeter measures one fluid, detects whether it is a liquid or a gas, and automatically configures itself to that detected fluid type. In situations where the user does not provide initial configuration data, the signal can be split as shown in FIG. 7, the vortex flowmeter determines the fluid type (liquid or gas) by recording the duration of one fluid type, and the vortex flowmeter can configure itself to measure that individual fluid type by turning off the signal passing through the alternate fluid type chain and configuring the individual totalizer. In this case, the vortex flowmeter can be configured to a default setting of 4 to 20 mA based on speed, where 20 mA is the upper limit of the device's accuracy. This essentially provides a self-configuring vortex flowmeter.

Claims

1. A vortex flow meter, a flow tube configured to receive the process fluid flow; a shedder bar disposed within the flow tube, the shedder bar configured to induce vortices in the process fluid flow; a vortex sensor positioned to detect vortices in the process fluid flow generated by the shedder bar; a measurement electronic circuit operably coupled to the vortex sensor, the measurement electronic circuit configured to detect an analog signal of the vortex sensor and provide a digital reading corresponding to the analog signal of the vortex sensor; a processor configured to receive the digital readings, calculate a speed of the process fluid flow based on a frequency of the digital readings, measure an amplitude of the digital readings, and estimate a density of the process fluid based on the measured amplitude; a processor configured to determine a fluid type based on the measured amplitude and assign a flow rate unit corresponding to the calculated flow speed to a fluid totalizer corresponding to the detected fluid type; Vortex flowmeters including:

2. 10. The vortex flowmeter of claim 1, wherein the processor is separate from and coupled to the measurement electronics, the measurement electronics including an analog-to-digital converter.

3. The vortex flowmeter of claim 1 , further comprising a communications module coupled to the processor, the communications module configured to communicate according to a process industry standard communications protocol.

4. The vortex flowmeter of claim 3 , wherein the communication module is configured to communicate totalizer information.

5. The vortex flowmeter of claim 4 , wherein the totalizer information includes a plurality of totalizer values, each totalizer value corresponding to a different process fluid.

6. 6. The vortex flow meter of claim 5, wherein the first totalizer value aggregates a flow rate of the process fluid and the second totalizer value aggregates a flow rate of the process gas.

7. 6. The vortex flow meter of claim 5, wherein a first totalizer value aggregates a flow rate of a first process liquid and a second totalizer value aggregates a flow rate of a second process liquid, the first and second process liquids having different densities, and the processor is configured to apply a density threshold to identify process liquid flow rates for the first and second process liquids.

8. The vortex flowmeter of claim 5 , wherein the communication module is configured to communicate digitally.

9. 6. The vortex flowmeter of claim 5, wherein the communication module is configured to generate separate 4-20 milliamp signals indicative of flow rates of two different process fluids.

10. 10. The vortex flow meter of claim 1, wherein the processor is configured to apply a first digital filter to the digital reading, the first filter configured to detect a flow rate of the process liquid.

11. 11. The vortex flowmeter of claim 10, wherein the processor is further configured to apply a second digital filter to the digital reading, the second digital filter configured to detect a flow rate of a process gas.

12. 1. A method for detecting a flow rate of a process fluid using a vortex flow meter, comprising: receiving an analog signal from the vortex sensor; digitally converting the analog signal from the vortex sensor to generate a first digital reading of the analog signal; copying the first digital reading to generate at least one additional digital reading of the analog signal; applying a first digital filter to the first digital reading, the first digital filter configured for detecting a process fluid, and a result of the first digital filter used to calculate a density of the process fluid; applying a second digital filter to the at least one additional digital reading of the analog signal, the second digital filter configured for detecting a process gas, and applying a result of the second digital filter to calculate a density of the process gas; determining whether the liquid flow signal exceeds a low liquid flow cutoff value, and selectively adding units of flow rate to a liquid flow rate totalizer if the liquid flow signal exceeds the low liquid flow cutoff value; determining whether the gas flow signal exceeds a lower gas flow cutoff value, and selectively adding units of flow to a gas flow totalizer if the gas flow signal exceeds the lower gas flow cutoff value; and providing a process fluid flow rate output based on the liquid flow rate totalizer and the gas flow rate totalizer; A method comprising:

13. 13. The method of claim 12, wherein the density of the process fluid is calculated by applying a second liquid filter pass to the results of the first digital filter.

14. 14. The method of claim 13, wherein the density of the process gas is calculated by applying a second gas filter pass to the result of the second digital filter.

15. 13. The method of claim 12, wherein providing a process fluid flow rate output comprises generating separate 4 to 20 milliamp signals indicative of the flow rates of two different process fluids.

16. 16. The method of claim 15, wherein the individual current values ​​represent zero flow rate for both process fluids.

17. 1. A method for detecting a flow rate of a process fluid using a vortex flow meter, comprising: receiving an analog signal from the vortex sensor; digitizing the analog signal from the vortex sensor to generate a digital reading of the analog signal; applying a digital filter to the digital reading, the digital filter configured to detect a process fluid, the results of the digital filter being used to calculate a density of the process fluid; comparing the calculated density to a density threshold; adding a unit of flow rate to a first liquid flow rate totalizer if the calculated density exceeds the density threshold; adding a unit of flow rate to a flow rate totalizer of the second liquid if the calculated density is below the density threshold; and providing a process fluid flow rate output based on the first and second liquid totalizers; A method comprising:

18. 18. The method of claim 17, wherein the density of the process fluid is calculated by applying a second filter pass to the results of the digital filter.

19. 18. The method of claim 17, wherein providing the process fluid flow rate output comprises generating separate 4 to 20 milliamp signals indicative of two different process fluid flow rates.

20. The method of claim 17 , wherein the method is iterative.

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