CN111829600A - Measuring device and measuring method for micro-upgrade flow - Google Patents

Abstract

The application discloses metering device and metering method of little upgrading flow, and this metering device includes: the orifice plate comprises a fluid inlet, a fluid outlet and a transverse channel positioned between the fluid inlet and the fluid outlet, the fluid inlet and the transverse channel are connected through a main channel, a first side channel and a second side channel, and the transverse channel and the fluid outlet are connected through a third side channel and a fourth side channel; the magnetic induction device comprises a coil, a conductive circuit and a magnet, wherein the coil and the magnet are arranged in the transverse channel, one end of the conductive circuit is connected with the coil, and the other end of the conductive circuit is connected with the current detection circuit; the current detection circuit is used for detecting the magnitude of induced current generated in the conducting circuit and the frequency of change of the current direction; induced current is generated in the conductive path when the magnet is pushed by the fluid to reciprocate in the transverse passage in a direction perpendicular to the coil; and a calculation device for calculating the flow rate of the fluid according to the magnitude of the induced current and the frequency of the change in the direction of the current.

Description

Measuring device and measuring method for micro-upgrade flow

technical field

The present application relates to the technical field of flow measurement, and in particular, to a metering device and a metering method for micro-upgraded flow.

Background technique

At present, the conventional measurement method is still the observation method of the measuring cylinder-like device at the milliliter level and the electronic balance weighing method. The observation method of measuring cylinder devices is affected by interface interference, and its error is always above 0.2ml; the electronic balance weighing method requires more accurate measurement of fluid density, and its measurement accuracy is not high for different types of oil phases. in the measuring cylinder method.

With the gradual deepening of the development and research of ultra-low permeability and ultra-low permeability reservoirs, the accurate measurement of small volume flow in experiments has become more and more difficult, and conventional measurement methods are difficult to meet the requirements for measurement accuracy. In the core experiment, the fluid volume in the conventional core was reduced from about 6 milliliters (ml) to about 2 ml, but the dead volume of the process in the same experiment did not decrease, so the measurement error was greatly increased. In addition, although the volume in the inlet and outlet pipelines required to calculate the volume of the fluid in the core can be calculated, and the volume of the fluid in the outlet back pressure can be measured, it is not easy to calibrate the volume under different pressure conditions due to the influence of compressibility, which further leads to The measurement error increases.

In conventional microscopic pore model experiments, since the total amount of fluid in the model body is very small, and its range is between 1 microliter (μL) and 200 μL, volume measurement is almost impossible, so the area method is usually used for measurement, or different calculation estimates are used. The amount of fluid in the state, but this method is also affected by whether the fluid is identifiable, and it cannot measure the flow change during the flow. Restricted by this technical situation, conventional microscopic experiments mostly focus on the localization analysis of observed phenomena, and the inability of quantitative analysis has always troubled researchers.

It can be seen that the existing measurement methods have great difficulties and errors in measuring the micro-upgrade flow, and it is difficult to meet the current measurement requirements for the micro-upgrade flow.

SUMMARY OF THE INVENTION

In a first aspect, an embodiment of the present application provides a metering device for micro-upgrade flow, which is used to reduce the measurement error of micro-upgrade flow and improve the measurement accuracy. The metering device includes:

The orifice plate 8 includes a fluid inlet 7, a fluid outlet 15, and a transverse channel 12 between the fluid inlet 7 and the fluid outlet 15. Between the fluid inlet 7 and the transverse channel 12, the main channel 9, the first side channel 10 and the first side channel 12 pass through. The two side flow channels 11 are connected, the angle between the first side flow channel 10 and the main flow channel 9 is the same as the angle between the second side flow channel 11 and the main flow channel 9, and the angle between the lateral channel 12 and the fluid outlet 15 is the same. The third side flow channel 32 is connected to the fourth side flow channel 33, and the width of the transverse channel 12 is greater than the width of the fluid inlet 7; the magnetic induction device includes the coil 16, the conductive line 34 and the magnet 13, and the coil 16 and the magnet 13 are arranged in the transverse direction. Inside the channel 12, one end of the conductive line 34 is connected to the coil 16, and the other end is connected to the current detection circuit 19; the current detection circuit 19 is used to detect the magnitude of the induced current generated in the conductive line 34 and the frequency at which the current direction changes; the The induced current is generated in the conductive line 34 when the magnet 13 is pushed by the fluid and reciprocates in the transverse channel 12 in a direction perpendicular to the coil 16; the computing device 21 calculates the flow rate of the fluid according to the magnitude of the induced current and the frequency at which the direction of the current changes. flow.

In a second aspect, an embodiment of the present application provides a metering method applied to the metering device for micro-upgrade flow as described in the first aspect, the method comprising:

When the fluid pushes the magnet to do the reciprocating motion of the cutting coil, the magnitude of the induced current generated in the conductive line and the frequency of the change of the current direction are detected; the flow rate of the fluid is calculated according to the magnitude of the induced current and the frequency of the change of the current direction.

The micro-upgrade flow metering device provided in the embodiment of the present application can be directly installed at the inlet or outlet of the core microscopic model, which eliminates the interference of the dead volume in the pipeline and the back pressure control device and the interference of the change of the compression coefficient, and improves the ultra-low At the same time, the application uses the principle of electromagnetic induction to establish a micro-current detection method for sensing the reciprocating motion of the magnet, and also solves the problem that conventional micro-tests cannot quantitatively measure the flow of micro-level upgrades.

Description of drawings

In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the following briefly introduces the accompanying drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present application. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without any creative effort. In the attached image:

1 is a schematic diagram of the principle of a metering device for micro-upgrade flow provided in an embodiment of the application;

FIG. 2 is a schematic structural diagram of an orifice plate in the metering device for micro-upgrade flow provided in the embodiment of the application;

3 is a schematic diagram of the principle of another micro-upgrade flow metering device provided in an embodiment of the application;

4 is a schematic structural diagram of a metering device for micro-upgrade flow provided in an embodiment of the application;

5 is a flowchart of a metering method applied to a metering device for micro-upgrade flow provided in an embodiment of the application;

6 is a schematic view of the size of the orifice plate of the metering device for micro-level flow rate applied to conventional microscopic experiments provided in the embodiment of the application;

7 is a schematic diagram of the installation position of the metering device for micro-upgrade flow in the conventional microscopic experiment provided in the embodiment of the application;

FIG. 8 is a schematic view of the dimensions of the orifice plate of the metering device for micro-upgrade flow rate applied to the core-flooding experiment provided in the embodiment of the application;

FIG. 9 is a schematic diagram of the installation position of the metering device for micro-upgrade flow in the core-flooding experiment provided in the embodiment of the present application.

reference number

1: Thin tube 2: Sudden expansion tube

3: Total flow vector 4: Main direction component

5: Eddy component 6: Lateral component

7: Fluid inlet 8: Orifice plate

9: Main runner 10: First side runner

11: Second side channel 12: Lateral channel

13: Magnet 14: Position marker

15: Fluid Outlet 16: Coil

17: Ammeter 18: Substrate

19: Current detection circuit 20: Amplifier circuit

21: Computing device 22: Flow output display window

23: Entrance 24: Microscopic Visual Model

25: Metering device for microliter flow rate 26: Pore section

27: Exit 28: Displacement device

29: Holder 30: Low permeability core

31: Back pressure and receiving device 32: Third side flow channel

33: Fourth side runner 34: Conductive line

Detailed ways

In order to make the purposes, technical solutions and advantages of the embodiments of the present application more clearly understood, the embodiments of the present application will be further described in detail below with reference to the accompanying drawings. Here, the exemplary embodiments and descriptions of the present application are used to explain the present application, but are not intended to limit the present application.

The application uses microfluidic technology to design micron-scale channels, and realizes the reciprocating motion of solid micro-particles in the transverse channel by fine-tuning the flow rate of different channels; it can be known from the principle of magnetic induction that the reciprocating motion of the micro-magnet will generate a micro-current in the surrounding conductive coil. , and monitoring the current direction conversion frequency can calculate the flow value in and out of the channel. The principle of the method of the present application will be briefly introduced below.

Referring to Fig. 1, it can be seen from the movement of the fluid in the flow channel where the thin tube 1 enters the sudden expanding tube 2 structure, the total flow vector 3 is dispersed into the main direction component 4 and the lateral component 6 after entering the sudden expanding tube 2, and the The vortex component 5 is formed on both sides of the main flow channel of the increased end face, where the pressure is lower, and the fluid is easy to stay here. Obviously, if there is a small solid that cannot flow out in the sudden expansion pipe 2, it will migrate at this low pressure and be the most stable.

According to the above principles, the embodiment of the present application designs an orifice plate 8 of a metering device for a micro-level flow rate, and the material of the orifice plate 8 may be polydimethylsiloxane (PDMS). Referring to FIG. 2 , the orifice plate 8 includes a fluid inlet 7 , a fluid outlet 15 and a transverse channel 12 between the fluid inlet 7 and the fluid outlet 15 . The fluid inlet 7 and the transverse channel 12 are connected by the main channel 9, the first side channel 10 and the second side channel 11. The angle between the first side channel 10 and the main channel 9 is the same as the second side channel. The angle between the channel 11 and the main channel 9 is the same. The transverse channel 12 and the fluid outlet 15 are connected to the fourth side channel 33 through the third side channel 32 . The width of the transverse channel 12 is greater than that of the fluid inlet 7 . Wherein, the outlet width of the first side channel 10 is half of the outlet width of the main channel 9 ; the outlet width of the second side channel 11 is half the outlet width of the main channel 9 .

According to the principle shown in FIG. 1 , when the fluid enters from the fluid inlet 7 , the main channel 9 , the first side channel 10 and the second side channel 11 enter the transverse channel 12 with a sudden increase in diameter. Referring to FIG. 2 , this The pressure is lowest at positions 04 and 04' in the transverse channel 12. The magnet 13, i.e. the magnetic ball as shown in the figure, has a tendency to be stable here, offset by the 04 and 04' positions due to the partial flow of the outgoing flow at 02 and 02'. If the magnets 13 at positions 03 and 03' tend to block the outlet side flow passages, the partial flow of the outflow flow from 02 and 02' drives them away. Thus within the transverse channel 12, the magnet 13 will reciprocate in the range 01 and 02 or 01 and 02' or 02 and 02' under the action of the inlet fluid flow.

Considering that the magnet 13 may reciprocate within the range of 01 and 02, the range of 01 and 02', or the range of 02 and 02', in the embodiment of the present application, the coil 16 takes the inlet main channel 9 as a boundary, and two sides Wound separately, that is, the coil 16 is wound in the range of 01 and 02, and 01 and 02' in FIG. 2, respectively, so that when the magnet 13 moves in the range of 01 and 02, the coil in the range of 01 and 02 can be wound. An induced current is generated in 16; when the magnet 13 moves in the range of 01 and 02', an induced current can be generated in the coil 16 in the range of 01 and 02'.

It should be noted that, after the magnet 13 moves under the initial condition, it will continue to move under the influence of inertia, and it will not be stable in a certain position. If the magnet 13 stops moving due to the roughness of the hole, the magnet 13 can be removed from the stop position by artificially changing the current direction and intensity of the coil 16 .

Obviously, the movement range and reciprocating frequency of the magnet 13 in the transverse channel 12 are positively related to the flow velocity. The higher the flow velocity, the larger the lateral movement range of the magnet 13 and the faster the reciprocating frequency.

In order to achieve micro-scale flow measurement, the size of the orifice of the orifice plate 8 in FIG. 2 is in the micrometer (μm) scale. According to the measurement needs, the size of the orifice can be adjusted to design and manufacture the metering device 25 for micro-upgrade flow with different flow ranges.

In addition, the metering device 25 for the micro-upgrade flow provided by the embodiment of the present application also utilizes the principle of electromagnetic induction. As shown in FIG. 3 , when the magnet 13 moves in the coil 16 , an induced current will be generated as the magnetic flux increases or decreases, and the sensitive ammeter 17 will detect the corresponding current direction and amplitude change.

According to the above electromagnetic induction principle, as shown in FIG. 4 , the embodiment of the present application designs a magnetic induction device, a current detection circuit 19 and a computing device 21 of a metering device for micro-upgrade flow. The magnetic induction device includes a coil 16, a conductive line 34, and a magnet 13. The coil 16 and the magnet 13 are arranged inside the transverse channel 12 (not shown in FIG. 4). One end of the conductive line 34 is connected to the coil 16, and the other end is connected to the current The detection circuit 19 is connected. The current detection circuit 19 is used to detect the magnitude of the induced current generated in the conductive line 34 and the frequency at which the direction of the current changes; when the magnet 13 is pushed by the fluid and reciprocates in the transverse channel 12 in a direction perpendicular to the coil 16 Produced in conductive traces 34 . The computing device 21 calculates the flow rate of the fluid according to the magnitude of the induced current and the frequency of changing the direction of the current.

The magnetic induction device includes two coils 16 and two conductive lines 34, each coil 16 is connected to one conductive line 34; one of the coils 16 is arranged in the transverse channel 12, between the first side channel 10 and the main channel 9 The other coil 16 is arranged in the transverse channel 12 at the position between the second side flow channel 11 and the main flow channel 9 . The orifice plate 8 is disposed on the base plate 18 . In order to stabilize the coil 16 , the coil can be wound on the base plate 18 and cured on the base plate 18 by liquid glue.

The material of the magnet 13 may be a neodymium iron boron magnet. The shape of the magnet 13 may be a cube, a rectangular parallelepiped, a sphere, or the like. However, considering that the friction of the sphere is relatively small, the shape of the sphere can be preferably selected as the magnet 13 .

Referring to FIG. 4 , it is a schematic diagram of the overall structure of the metering device for micro-upgrade flow provided by the embodiment of the present application. The current detection circuit 19 in the metering device includes an amplification circuit 20 connected to the conductive line 34 for amplifying the induced current in the conductive line 34 . The amplifying circuit 34 can adopt the triode multi-stage amplifying method, and can detect the current change of the nano-ampere (NA) level. In the embodiment of the present application, the magnet 13 is small, and the number of coils 16 is less limited by the volume, and its current variation range is below the microamp level. Therefore, in order to improve the measurement accuracy, an amplifier can be set between the conductive line 34 and the current detection device. circuit 20. The structure and connection method of the discharge circuit 20 are mature in the prior art, and will not be repeated here.

In an implementation manner of the embodiment of the present application, in order for the user to know the size of the flow, as shown in FIG. size.

The micro-upgrade flow metering device provided in the embodiment of the present application can be directly installed at the inlet or outlet of the core microscopic model, which eliminates the interference of the dead volume in the pipeline and the back pressure control device and the interference of the change of the compression coefficient, and improves the ultra-low At the same time, the application uses the principle of electromagnetic induction to establish a micro-current detection method for sensing the reciprocating motion of the magnet, and also solves the problem that conventional micro-tests cannot quantitatively measure the flow of micro-level upgrades.

The embodiment of the present application also provides a metering method applied to the aforementioned micro-upgraded flow metering device. As shown in FIG. 5 , the method includes:

Step 501: Detect the magnitude of the induced current and the frequency at which the current direction changes when the fluid pushes the magnet to perform the reciprocating motion of the cutting coil.

Step 502: Calculate the flow rate of the fluid according to the magnitude of the induced current and the frequency at which the direction of the current changes.

In an implementation manner of the embodiment of the present application, calculating the flow rate of the fluid according to the magnitude of the induced current and the frequency of changing the direction of the current includes: calculating the distance S of the magnet in one reciprocating motion according to the formula S=ae ^bI , where a , b are constants, I is the amplitude of the induced current; calculate the single flow q according to the formula q=me ^S , where m is the constant related to the channel; calculate the flow rate Q of the fluid according to the formula Q=nq, where n is the current The frequency with which the direction changes.

Among them, the constants a and b can be determined according to the following methods:

The flow rate of the fluid is preset, and the fluid with different constant flow rates is used to flow through the micro-level flow metering device to collect the magnitude of the induced current corresponding to the different flow rates and the frequency at which the current direction changes; according to the magnitude and current of the induced current corresponding to the different flow rates The frequency of the direction change determines the constants a, b.

m is related to the channel structure such as the diameter of the channel, the angle between the main channel and the side channel, the length of the channel, and the width of the lateral channel. Therefore, after the metering device for the micro-upgrade flow rate described in the present application is manufactured, the parameter m is determined experimentally with a fixed flow rate according to the pore structure.

The micro-upgrade flow metering device provided in the embodiment of the present application can be directly installed at the inlet or outlet of the core microscopic model, which eliminates the interference of the dead volume in the pipeline and the back pressure control device and the interference of the change of the compression coefficient, and improves the ultra-low At the same time, the application uses the principle of electromagnetic induction to establish a micro-current detection method for sensing the reciprocating motion of the magnet, and also solves the problem that conventional micro-tests cannot quantitatively measure the flow of micro-level upgrades.

The following will introduce a metering device for micro-up flow rate applied in conventional microscopic experiments, and a metering device for micro-up flow rate applied in core flooding experiments in combination with specific dimensions.

1. A metering device for micro-level flow in conventional microscopic experiments

The design dimensions of the metering device for micro-upgrade flow suitable for the microscopic visual model are shown in Figure 6. Its external dimensions are 3 millimeters (mm) × 6 mm × 2 mm, and the thickness of the channels is 40 micrometers (μm). After calculation, it can be known that the total space volume in the channel of the metering device is about 0.2 microliter (μL). The fabrication method and process of the 40 μm pore PDMS model is a mature technology, and will not be repeated here.

The coil 16 in the magnetic induction device can be a copper wire with a diameter of 12 μm. When the shape of the used magnet 13 is spherical, the diameter of the magnetic sphere is between 30 and 35 μm.

When performing conventional microscopic experiments, it can be installed according to one of the two installation positions of the metering devices 25 for micro-upgrade flow as shown in FIG. 27 are available. In the microscopic visualization model 24 , the metering device 25 is placed directly inside the microscopic visualization model 24 .

In conventional microscopic experiments using the metering device 25 for micro-level flow rate provided by the present application, the total amount of fluid passing through the pores of the microscopic visual model 24 is accurately measured.

Furthermore, the aperture portion 26 shown in FIG. 7 is a constituent part of the microscopic visual model 24 .

2. A metering device for micro-upgrade flow in core flooding experiments

Figure 8 shows the design dimensions of the micro-upgraded flow metering device suitable for core flooding. After calculation, it can be known that the total space volume in the channel of the metering device is about 3.6 μL.

The coil 16 in the magnetic induction device can also be a copper wire with a diameter of 12 μm. When the shape of the used magnet 13 is spherical, the diameter of the magnetic sphere is between 100 and 115 μm.

When performing the core flooding experiment, it can be installed according to one of the two installation positions of the metering device 25 for the micro-level flow rate as shown in FIG. Either, in the rock displacement experiment, the metering device needs to be in contact with the rock.

In addition, it should be noted that in the core flooding experiments, the injection rate of the displacement device is strictly controlled. Since the metering device of micro-liter flow rate is consistent with the characteristics of ultra-low osmotic and ultra-low osmotic slow-speed seepage, the injection speed is very slow. The flow metering device excludes the influence of the displacement device and the fluid compressibility in the intermediate container, and the measured value is 40 μL/min.

In the displacement experiment using the metering device with a micro-upgrade flow rate provided by the present application, the flow rate of the fluid passing through the metering device is measured and stored in real time.

In addition, the displacement device 28 , the holder 29 , the low-permeability core 30 , the back pressure and the receiving device 31 shown in FIG. 9 are all commonly used devices in the core displacement experiment, and will not be repeated here.

As will be appreciated by those skilled in the art, the embodiments of the present application may be provided as a method, a system, or a computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, etc.) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the present application. It will be understood that each flow and/or block in the flowchart illustrations and/or block diagrams, and combinations of flows and/or blocks in the flowchart illustrations and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to the processor of a general purpose computer, special purpose computer, embedded processor or other programmable data processing device to produce a machine such that the instructions executed by the processor of the computer or other programmable data processing device produce Means for implementing the functions specified in a flow or flow of a flowchart and/or a block or blocks of a block diagram.

These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory result in an article of manufacture comprising instruction means, the instructions The apparatus implements the functions specified in the flow or flows of the flowcharts and/or the block or blocks of the block diagrams.

These computer program instructions can also be loaded on a computer or other programmable data processing device to cause a series of operational steps to be performed on the computer or other programmable device to produce a computer-implemented process such that The instructions provide steps for implementing the functions specified in the flow or blocks of the flowcharts and/or the block or blocks of the block diagrams.

The specific embodiments described above further describe the purpose, technical solutions and beneficial effects of the present application in further detail. It should be understood that the above are only specific embodiments of the present application and are not intended to limit the Within the scope of protection, any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included in the protection scope of this application.

Claims (10)

1. A metering device for micro-scale flow, the metering device comprising:

the orifice plate (8) comprises a fluid inlet (7), a fluid outlet (15) and a transverse channel (12) positioned between the fluid inlet (7) and the fluid outlet (15), the fluid inlet (7) and the transverse channel (12) are connected through a main channel (9), a first side channel (10) and a second side channel (11), an included angle between the first side channel (10) and the main channel (9) is the same as that between the second side channel (11) and the main channel (9), the transverse channel (12) and the fluid outlet (15) are connected through a third side channel (32) and a fourth side channel (33), and the width of the transverse channel (12) is larger than that of the fluid inlet (7);

the magnetic induction device comprises a coil (16), a conductive circuit (34) and a magnet (13), wherein the coil (16) and the magnet (13) are arranged in the transverse channel (12), one end of the conductive circuit (34) is connected with the coil (16), and the other end of the conductive circuit is connected with the current detection circuit (19);

a current detection circuit (19) for detecting the magnitude of an induced current generated in the conductive line (34) and the frequency of change in the direction of the current; the induced current is generated in the conductive line (34) when the magnet (13) is reciprocated in the transverse channel (12) in a direction perpendicular to the coil (16) by the fluid;

and a calculation device (21) that calculates the flow rate of the fluid based on the magnitude of the induced current and the frequency at which the direction of the current changes.

2. The apparatus according to claim 1, wherein the current detection circuit (19) comprises:

and the amplifying circuit (20) is connected with the conductive line (34) and is used for amplifying the induced current in the conductive line (34).

3. The device according to claim 1, characterized in that the outlet width of the first side channel (10) is half the outlet width of the main channel (9); the outlet width of the second side runner (11) is half of the outlet width of the main runner (9).

4. A device according to claim 1 or 2, characterized in that the magnetic induction means comprise two coils (16) and two electrically conductive tracks (34), each coil (16) being connected to one electrically conductive track (34); one of the coils (16) is arranged in the transverse channel (12) at a position between the first side channel (10) and the main channel (9); another coil (16) is arranged in the transverse channel (12) at a position between the second side channel (11) and the main channel (9).

5. The device according to claim 1, characterized in that the orifice plate (8) is arranged on a base plate (18), the coil (16) being wound on the base plate (18) and being cured on the base plate (18) with a liquid glue.

6. The device according to claim 1, wherein the material of the orifice plate (8) comprises polydimethylsiloxane.

7. Device according to claim 1, characterized in that the material of the magnet (13) comprises a neodymium-iron-boron magnet.

8. A metering method applied to the metering device of the micro-upgrade flow as claimed in any one of claims 1 to 6, characterized in that the method comprises the following steps:

detecting the magnitude of induced current generated in the conducting circuit and the frequency of change of the current direction when the fluid pushes the magnet to do reciprocating motion of the cutting coil;

and calculating the flow rate of the fluid according to the magnitude of the induced current and the frequency of the change of the current direction.

9. The method of claim 8, wherein calculating the flow rate of the fluid based on the magnitude of the induced current and the frequency of the change in direction of the current comprises:

according to the formula S ═ ae^bICalculating the path S of the magnet in one reciprocating motion, wherein a and b are constants, and I is the amplitude of the induction current;

according to the formula q me^SCalculating single flow q, wherein m is a constant related to a pore channel;

the flow rate Q of the fluid is calculated according to the formula Q nq, where n is the frequency at which the direction of the current changes.

10. The method of claim 8 or 9, wherein before calculating the flow rate of the fluid based on the magnitude of the induced current and the frequency of the change in direction of the current, the method further comprises:

presetting the flow rate of fluid, and collecting the magnitude of induced current corresponding to different flow rates and the frequency of current direction change by utilizing the flow of the fluid with different constant flow rates through a metering device for micro-upgrade flow;

the constants a, b are determined according to the magnitude of the induced current corresponding to different flow rates and the frequency of the change in the direction of the current.

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