Novel gas-liquid two-phase flowmeter and measuring method thereof

Abstract

The invention relates to the technical field of gas-liquid two-phase flow detection, in particular to a novel gas-liquid two-phase flowmeter which comprises a shell, an inlet section, a contraction section, a throttling measurement section, a diffusion section and an outlet section are sequentially arranged in an inner cavity of the shell from one end to the other end, capacitors are installed on the two sides of the throttling measurement section, and the capacitors are connected with the contraction section. The throttling measuring section is arranged between the contraction section and the expansion section, the fluid flow and the gas-liquid content in the fluid can be measured at the same time, the fluid flow velocity is obtained by measuring the pressure difference of the fluid before and after passing through the contraction section, and the flow velocity of the fluid is measured by measuring the pressure difference of the fluid before and after passing through the expansion section. And the gas-liquid holdup in the fluid is measured at the throttling measurement section through a capacitance method or a radio frequency admittance method.

Description

Technical Field

[0001] The invention relates to the technical field of gas-liquid two-phase flow detection, and in particular to a novel gas-liquid two-phase flow meter. Background Art

[0002] In the fields of energy and chemical industry, it is often necessary to measure the flow rate of gas-liquid two-phase fluid and the gas-liquid content in the gas-liquid two-phase fluid. The most common liquid in the gas-liquid two-phase fluid is water. At present, the measurement of gas-liquid two-phase flow in the fluid is mainly achieved through Venturi flowmeter. According to Bernoulli's equation, the flow rate of the fluid through the throttling device is proportional to the square root of the pressure difference before and after the throttling device. Therefore, after detecting the pressure difference before and after the throttling device, the flow rate of the fluid can be calculated; the flow rate of the fluid can be obtained by multiplying the flow rate of the fluid by the cross-sectional area of ​​the throttling section; because Venturi can only be used to detect the total flow rate of the fluid, it cannot effectively detect the gas-liquid content in the fluid. Therefore, its application is limited. The detection of gas-liquid content is often measured by capacitance method or radio frequency admittance method. A pair of electrodes are set on the pipe wall, and the difference in dielectric constants of the two media in the mixture is used to measure the capacitance value of the capacitor formed between the two electrodes. The proportion of the two media in the medium between the two electrodes is calculated, thereby determining the content of the two media in the mixture. The flow patterns of gas-liquid two phases in horizontal pipes can be roughly divided into seven types. If the flow rate of liquid in the pipeline remains unchanged, and the flow rate of gas increases from small to large, the order of flow patterns is: bubbly flow - slug flow - laminar flow - wavy flow - impact flow (slug flow) - annular flow - mist flow.

[0003] Since the medium in the pipeline has different flow states and changes frequently, the liquid surface closer to the electrode has a greater impact on the electrode, while the liquid surface farther away from the electrode has a smaller impact on the electrode. In addition, the cross-section of the pipeline is generally circular, the two plates are arc-shaped, and the distance between the two plates changes continuously. Therefore, ordinary capacitance method or radio frequency admittance method detection method cannot accurately detect the average dielectric constant of the medium in the pipeline. Summary of the invention

[0004] In view of the shortcomings of the prior art, the present invention proposes a novel gas-liquid two-phase flowmeter, which can accurately measure the gas and liquid two-phase flow rates in a fluid at the same time.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention proposes a novel gas-liquid two-phase flowmeter, comprising a shell, wherein the inner cavity of the shell is composed of an inlet section, a contraction section, a throttling measurement section, a diffusion section and an outlet section from one end to the other, capacitors are installed on both sides of the throttling measurement section, the inlet section is provided with a front pressure-taking hole, and the throttling measurement section is provided with a rear pressure-taking hole.

[0007] Specifically, the throttling measurement section is in the shape of a rectangular parallelepiped, and the two plates of the capacitor are both flat electrodes, and are respectively installed on two opposite surfaces of the throttling measurement section.

[0008] Specifically, the contraction section and the diffusion section are both in the shape of a quadrangular pyramid.

[0009] Specifically, the two plates of the capacitor are insulated from each other.

[0010] Specifically, a front pressure-taking hole is provided through the side wall of the inlet section, and a rear pressure-taking hole is provided through the side wall of the throttling measurement section.

[0011] The present invention also proposes a novel measurement method for a gas-liquid two-phase flowmeter, which measures the phase fraction and the cross-sectional area of ​​the phase in the fluid by using the capacitance method or the radio frequency admittance method through the capacitance of the throttling measurement section, calculates the flow velocity of the phase by the pressure difference before and after the fluid flows through the contraction section and the Reynolds number of the phase, and finally multiplies the flow velocity of the phase by the cross-sectional area of ​​the phase in the throttling measurement section to obtain the instantaneous flow rate of the phase.

[0012] Compared with the prior art, the present invention has the following beneficial effects:

[0013] (1) The present invention sets a throttling measurement section between the contraction section and the diffusion section, which can simultaneously measure the fluid flow rate and the gas-liquid content in the fluid. The fluid flow rate is obtained by measuring the pressure difference before and after the fluid passes through the contraction section, and the gas-liquid content in the fluid is measured in the throttling measurement section by the capacitance method or the radio frequency admittance method.

[0014] (2) The present invention sets the throttling measurement section into a rectangular parallelepiped shape, and sets the two plates of the capacitor on two opposite surfaces of the throttling measurement section respectively. The electric field lines between the two plates are mainly parallel lines and can be evenly distributed between the two plates to the greatest extent. In this way, the dielectric constant between the positive and negative plate electrodes measured by the capacitance method can form an equivalent linear proportional relationship with the cross-sectional area of ​​the rectangular parallelepiped channel, so that the dielectric constant between the positive and negative plate electrodes can accurately reflect the water content between the positive and negative plate electrodes, and directly convert the cross-sectional area of ​​water in the throttling measurement section. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a structural schematic diagram of the flow meter of the present invention;

[0016] Figure 2 It is a schematic diagram of the side view structure inside the housing of the flow meter of the present invention;

[0017] Figure 3 Schematic diagram of the electric field line distribution between two plates of a capacitor in the flow meter of the present invention;

[0018] Figure 4 This is the principle diagram of the gas-liquid two-phase flowmeter calibration device;

[0019] Figure numerals: 1. Shell, 2. Inlet section, 3. Contraction section, 4. Throttling measurement section, 5. Diffusion section, 6. Outlet section, 7. Capacitor, 8. Signal cable, 9. Front pressure taking hole, 10. Rear pressure taking hole. DETAILED DESCRIPTION

[0020] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0021] Example

[0022] refer to Figure 1 and Figure 2 The present embodiment proposes a novel gas-liquid two-phase flowmeter, comprising a shell 1, wherein the inner cavity of the shell 1 is sequentially composed of an inlet section 2, a contraction section 3, a throttling measurement section 4, a diffusion section 5 and an outlet section 6 from one end to the other, and capacitors 7 are installed on both sides of the throttling measurement section 4, wherein the inlet section 2 and the diffusion section 5 are coaxial cylindrical, and the diameters of the inlet section 2 and the diffusion section 5 are both the same as the diameter of the fluid pipeline, the inlet section 2 introduces the fluid into the contraction section 3, and the fluid flows through the contraction section 3, the throttling measurement section 4, the diffusion section 5 and the outlet section 6 in sequence, according to the Bernoulli equation, the fluid flow rate can be obtained by detecting the fluid pressure difference between the inlet section 2 and the throttling measurement section 4, and the gas-liquid content in the fluid is obtained by the capacitors 7 installed on both sides of the throttling measurement section 4, the present embodiment has a simple structure and is easy to use, and can simultaneously detect the fluid flow rate and the gas-liquid content in the fluid.

[0023] Specifically, the throttling measurement section 4 is in a rectangular shape, and the two ends of the throttling measurement section 4 are smoothly transitioned with the contraction section 3 and the diffusion section 5, respectively. Figure 2 and Figure 3 The two plates of the capacitor 7 are both flat electrodes, and are respectively installed on two opposite surfaces of the throttling measurement section 4, so that the electric field lines between the two plates are mainly parallel lines, and can be evenly distributed between the two plates to the greatest extent. In this way, the dielectric constant between the positive and negative flat electrodes measured by the capacitor 7 method forms an equivalent linear proportional relationship with the cross-sectional area of ​​the rectangular channel, so that the dielectric constant between the positive and negative flat electrodes can accurately reflect the water content between the positive and negative flat electrodes, and directly convert the cross-sectional area of ​​the water in the throttling measurement section 4. The calculation process is simple and the detection result is accurate, wherein the contraction section 3 and the diffusion section 5 can preferably be a quadrangular pyramid.

[0024] Specifically, the two plates of capacitor 7 are insulated, and the two plates of capacitor 7 are respectively connected to the data processor outside the flow meter through signal cable 8. The signal cable 8 transmits the collected capacitance 7 data to the data processor, and the data processor calculates the gas-liquid content in the fluid through the capacitance 7 of capacitor 7.

[0025] A front pressure-taking hole 9 is provided through the side wall of the inlet section 2, and a rear pressure-taking hole 10 is provided through the side wall of the throttling measuring section 4. The rear pressure-taking hole 10 does not conflict with the electrode plate of the capacitor 7. The first pressure-taking tube passes through the front pressure-taking hole 9 and is connected to the inlet section 2, and the second pressure-taking tube passes through the rear pressure-taking hole 10 and is connected to the throttling measuring section 4. The flow rate of the fluid in the pipeline can be calculated by the liquid pressure difference in the first pressure-taking tube and the second pressure-taking tube.

[0026] In this embodiment, each electrode plate of the capacitor 7 is in the shape of a flat plate with a certain width.

[0027] In order to better illustrate the beneficial effects of the present invention, refer to Figure 4 , the gas-liquid two-phase flowmeter in this embodiment is used as the gas-liquid two-phase flowmeter to be tested, and the gas-liquid two-phase flowmeter to be tested is installed on the gas-liquid two-phase flowmeter calibration device. The host computer reads the test data of the gas and liquid two-phase flowmeters and the gas-liquid two-phase flowmeter to be tested respectively through the standard Modbus communication protocol. Finally, the test data of the gas-liquid two-phase flowmeter to be tested is compared with the test data of the gas and liquid two-phase flowmeters on the gas-liquid two-phase flowmeter calibration device: During the test, the gas and water flow ratio is adjusted for each test point first, and after the gas-liquid two-phase flowmeter calibration device runs stably, the data is measured. The amount of measured data for each test point is 3 groups. The test results of the gas-liquid two-phase flowmeter calibration device are shown in Table 1:

[0028] Table 1 Test results of gas-liquid two-phase flowmeter calibration device

[0029]

[0030] The most common occasion for the use of gas-liquid two-phase flowmeters is the measurement of natural gas wellheads in oil and gas fields. According to the requirements of Section 4.4.7 of GB 50349-2015 "Gas Field Gathering and Transportation Design Specifications", the allowable deviation of the three-level metering system should be ±7.0%; according to Section 4.4.2, the measurement accuracy of water and natural gas condensate produced by gas wells should be determined according to production needs, and the allowable deviation should be ±10%. According to the requirements of Section 5.4.6 of SY / T 7700-2023 "Oil and Gas Field and Pipeline Engineering Instrument Control System Design Specifications", the maximum allowable error of each phase flow measurement of multiphase meters is ±5% for liquids and ±10% for gases.

[0031] It can be seen from Table 1 that the average measurement error of the gas-liquid two-phase flowmeter of the present invention for the gas in the mixture is 0.43%, and the average measurement error for the liquid in the mixture is 0.307%, and the measurement accuracy is relatively high.

[0032] The specific embodiments of the present invention enable those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0033] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A new type of gas-liquid two-phase flow meter, characterized in that: The invention comprises a shell (1), wherein the inner cavity of the shell (1) is composed of an inlet section (2), a contraction section (3), a throttling measurement section (4), a diffusion section (5) and an outlet section (6) from one end to the other end, capacitors (7) are installed on both sides of the throttling measurement section (4), the inlet section (2) is provided with a front pressure-taking hole (9), and the throttling measurement section (4) is provided with a rear pressure-taking hole (10).

2. A novel gas-liquid two-phase flowmeter according to claim 1, characterized in that: The throttling measurement section (4) is in the shape of a rectangular parallelepiped, and the two plates of the capacitor (7) are both flat plate electrodes, and are respectively installed on two opposite surfaces of the throttling measurement section (4).

3. A novel gas-liquid two-phase flowmeter according to claim 2, characterized in that: The contraction section (3) and the diffusion section (5) are both in the shape of a quadrangular pyramid.

4. A novel gas-liquid two-phase flowmeter according to claim 2, characterized in that: The two plates of the capacitor (7) are insulated.

5. A novel gas-liquid two-phase flowmeter according to claim 1, characterized in that: A front pressure-taking hole (9) is provided through the side wall of the inlet section (2), and a rear pressure-taking hole (10) is provided through the side wall of the throttling measurement section (4).

6. The measurement method of a novel gas-liquid two-phase flowmeter according to claim 1 is characterized in that: The phase fraction and the cross-sectional area of ​​the phase in the fluid are measured by the capacitance (7) of the throttling measurement section (4) using the capacitance method or the radio frequency admittance method, and the flow velocity of the phase is calculated by the pressure difference before and after the fluid flows through the contraction section (3) and the Reynolds number of the phase. Finally, the flow velocity of the phase is multiplied by the cross-sectional area of ​​the phase in the throttling measurement section (4) to obtain the instantaneous flow rate of the phase.

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