Conductivity Sensor for Transient Measurement of Gas Holdup in Gas-Liquid Two-Phase Flow in Helical Tubes

Abstract

The present invention discloses a conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube. The ends of a first connecting tube, a first protection electrode, a receiving electrode, a second protection electrode, and a second connecting tube are sequentially connected in an open loop. A first insulating ring is provided between the first protection electrode and the receiving electrode, and a second insulating ring is provided between the receiving electrode and the second protection electrode. One end of the emitting electrode is inserted from one side of the first connecting tube and extends along the axis direction of the first connecting tube to the second connecting tube, and the other end of the emitting electrode is located outside the first connecting tube. The part of the emitting electrode extending along the axis direction of the first connecting tube is located on the convex side of the axis of the first connecting tube and is at a certain distance from the axis of the first connecting tube. The present invention can perform transient measurement of the gas holdup in gas-liquid two-phase flow in a spiral tube, can avoid the influence of edge effects on the measurement results, and the measurement is fast and accurate.

Description

Technical Field

[0001] The present invention belongs to the field of sensors, and particularly relates to a conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a helical tube. Background Art

[0002] The complex and changeable flow characteristics of gas-liquid two-phase flow make it very difficult to measure the gas holdup. Accurately detecting various parameters of two-phase flow is of great significance for the research and manufacture of modern industrial equipment. Currently, the commonly used gas holdup measurement methods in gas-liquid two-phase flow measurement are mainly divided into contact measurement and non-contact measurement. Among them, contact measurement includes conductance probes, optical fiber probes, etc.; non-contact measurement includes ultrasonic method, ray method, tomography (CT), quick closing valve method, differential pressure method, etc. These measurement methods for two-phase flow gas holdup all have certain disadvantages, which limit their application scope to a certain extent. For example, contact measurement generally will cause certain disturbance and influence on the flow condition of two-phase flow in the pipe, will destroy the stability of the flow field, and will reduce the measurement accuracy under high temperature conditions; although non-contact measurement has the advantage of non-invasive measurement, they all have their own disadvantages. For example, the tomography measurement technology highly depends on the accuracy of the image reconstruction algorithm and can only ensure the measurement effect in the measurement range with low gas holdup. The quick closing valve method cannot adapt to transient application scenarios such as on-line measurement, etc. Therefore, the applicable range of non-contact measurement is limited and the accuracy is slightly poor.

[0003] The steam generator is the core equipment for energy transfer in a new type of nuclear reactor. Compared with other types of steam generators, the helical tube steam generator has the characteristics of good heat transfer performance, compact structure, free thermal expansion, and small thermal stress between the tube and the tube sheet, which improves the reliability and safety of related equipment. Therefore, in recent years, the helical tube once-through steam generator has received wide attention. In order to measure the gas holdup of gas-liquid two-phase flow in a helical tube, a sensor with rapid response and accurate measurement is essential. In addition, most of the existing gas holdup measurement methods are designed for straight pipe sections and cannot be directly applied to curved pipes. No measurement method specifically applicable to the gas holdup in a helical tube has been found, and there is no transient measurement sensor for gas holdup designed for helical tubes.

[0004] Patent CN110243876B discloses a conductivity sensor for transient measurement of gas holdup in two-phase flow in a straight pipe, which can accurately, quickly and non-interferingly measure the gas holdup of two-phase flow in a straight pipe. However, this structure is designed for a straight pipe section and is not suitable for a helical tube; if it is directly bent into a helical form for use, there are also problems such as uneven volume distribution around the axis of the emitting electrode, so that the measured conductance impedance value and the gas holdup are not in a one-to-one correspondence relationship, resulting in a certain deviation between the gas holdup measurement result and the actual working condition parameters. Summary of the Invention

[0005] In view of the technical problems existing in the prior art, the present invention provides a conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube, which can perform transient measurement of the gas holdup in the gas-liquid two-phase flow in the spiral tube, with fast and accurate measurement and little interference.

[0006] To solve the above technical problems, the present invention is realized through the following technical solutions:

[0007] A conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube, comprising a first connecting pipe, a first protection electrode, a first insulating ring, a receiving electrode, a second insulating ring, a second protection electrode, a second connecting pipe and a transmitting electrode. The first protection electrode, the receiving electrode and the second protection electrode are all tubular, and the curvatures of the first connecting pipe, the first protection electrode, the receiving electrode, the second protection electrode and the second connecting pipe are consistent with the curvature of the spiral tube to be measured. The transmitting electrode is filamentous. The ends of the first connecting pipe, the first protection electrode, the receiving electrode, the second protection electrode and the second connecting pipe are sequentially connected in an open-loop manner. The first insulating ring is arranged between the first protection electrode and the receiving electrode, and the second insulating ring is arranged between the receiving electrode and the second protection electrode. One end of the transmitting electrode is inserted from one side of the first connecting pipe and extends along the axial direction of the first connecting pipe to the second connecting pipe, and the other end of the transmitting electrode is located outside the first connecting pipe. The part of the transmitting electrode extending along the axial direction of the first connecting pipe is located on the convex side of the axis of the first connecting pipe and is at a certain distance h from the axis of the first connecting pipe. The calculation formula for the distance h is:

[0008]

[0009] In the formula, R is the spiral radius; r is the inner diameter of the first connecting pipe.

[0010] Further, a first flange is fixed at one end of the first connecting pipe, and a second flange is fixed at one end of the second connecting pipe. After the first flange and the second flange are connected by a bolt screw, the first protection electrode, the first insulating ring, the receiving electrode, the second insulating ring and the second protection electrode are pressed between the first connecting pipe and the second connecting pipe.

[0011] Further, a third flange is fixed at the other end of the first connecting pipe, and a fourth flange is fixed at the other end of the second connecting pipe. The third flange and the fourth flange are used to connect with the spiral tube to be measured.

[0012] Further, the inner diameters of the first connecting pipe, the second connecting pipe, the first flange, the second flange, the third flange and the fourth flange are the same.

[0013] Further, the inner diameters of the first connecting pipe, the first protection electrode, the receiving electrode, the second protection electrode, and the second connecting pipe are the same.

[0014] Further, the inner diameters of the first connecting pipe, the first protection electrode, the first insulating ring, the receiving electrode, the second insulating ring, the second protection electrode, and the second connecting pipe are the same.

[0015] Further, the first connecting pipe and the second connecting pipe are made of transparent plexiglass tubes.

[0016] Further, the materials of the first protection electrode, the receiving electrode, the second protection electrode, and the emitting electrode are copper.

[0017] Further, the materials of the first insulating ring and the second insulating ring are plexiglass.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects: For a conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a helical pipe provided by the present invention, the emitting electrode is arranged at a certain offset on the convex side outside the axis of the helical pipe, so that it is located at the volume center of the helical pipe. In this way, the volume distribution around the emitting electrode can be made uniform, thereby ensuring that the measured conductance impedance value and the gas holdup in the helical pipe have a one-to-one correspondence. Secondly, protection electrodes are arranged on both sides of the receiving electrode, which can effectively avoid the interference of edge effects on the measurement results, and has the characteristics of small fluctuation deviation and high stability of the measurement results. Thirdly, the emitting electrode is a filamentous electrode, and the receiving electrode is a tubular electrode, and its inner diameter is equal to the inner diameter of the connecting pipe, ensuring that the normal flow of the two-phase flow in the pipe is not interfered, and avoiding introducing additional measurement errors.

[0019] In order to make the above objects, features, and advantages of the present invention more obvious and understandable, the following specifically enumerates preferred embodiments and, in conjunction with the accompanying drawings, makes the following detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the specific embodiments of the present invention, the following will briefly introduce the drawings required for the description of the specific embodiments. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0021] Figure 1 It is an axial sectional view of a conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a helical pipe according to the present invention;

[0022] Figure 2Schematic diagram for calculating the offset distance of the emitting electrode of a conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to the present invention;

[0023] Figure 3 Schematic diagram of the equivalent circuit when the conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to the present invention is working.

[0024] In the figure: 1 - first connecting pipe; 101 - first flange; 102 - third flange; 2 - first protection electrode; 3 - first insulating ring; 4 - receiving electrode; 5 - second insulating ring; 6 - second protection electrode; 7 - second connecting pipe; 701 - second flange; 702 - fourth flange; 8 - emitting electrode; 9 - bolt and screw. Specific embodiments

[0025] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some but not all of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0026] As Figure 1 shown, a conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to the present invention includes a first connecting pipe 1, a first protection electrode 2, a first insulating ring 3, a receiving electrode 4, a second insulating ring 5, a second protection electrode 6, a second connecting pipe 7 and an emitting electrode 8. The first protection electrode 2, the receiving electrode 4 and the second protection electrode 6 are all tubular, and the curvatures of the first connecting pipe 1, the first protection electrode 2, the receiving electrode 4, the second protection electrode 6 and the second connecting pipe 7 are the same as the curvature of the spiral tube to be measured, and the emitting electrode 8 is filamentous.

[0027] The ends of the first connecting pipe 1, the first protection electrode 2, the receiving electrode 4, the second protection electrode 6 and the second connecting pipe 7 are sequentially connected in an open-loop manner. A first insulating ring 3 is arranged between the first protection electrode 2 and the receiving electrode 4, and a second insulating ring 5 is arranged between the receiving electrode 4 and the second protection electrode 6. Specifically, a first flange 101 is fixed at one end of the first connecting pipe 1, a second flange 701 is fixed at one end of the second connecting pipe 7, and after the first flange 101 and the second flange 701 are connected by a bolt and screw 9, the first protection electrode 2, the first insulating ring 3, the receiving electrode 4, the second insulating ring 5 and the second protection electrode 6 are pressed between the first connecting pipe 1 and the second connecting pipe 7. The same curvature means that the axes of the first connecting pipe 1, the first protection electrode 2, the first insulating ring 3, the receiving electrode 4, the second insulating ring 5, the second protection electrode 6 and the second connecting pipe 7 are the same after connection.

[0028] One end of the emitting electrode 8 is inserted from one side of the first connecting pipe 1 and extends along the axial direction of the first connecting pipe 1 to the second connecting pipe 7. The other end of the emitting electrode 8 is located outside the first connecting pipe 1. The part of the emitting electrode 8 extending along the axial direction of the first connecting pipe 1 is located on the convex side of the axis of the first connecting pipe 1 and is at a certain distance h from the axis of the first connecting pipe 1. The calculation formula for the distance h is:

[0029]

[0030] In the formula, R is the spiral radius; r is the inner diameter of the first connecting pipe.

[0031] That is to say, the extending part of the emitting electrode 8 within the first connecting pipe 1, the first protection electrode 2, the first insulating ring 3, the receiving electrode 4, the second insulating ring 5 and the second protection electrode 6 has the same extending direction as the axial directions of the first connecting pipe 1, the first protection electrode 2, the first insulating ring 3, the receiving electrode 4, the second insulating ring 5 and the second protection electrode 6, and the extending part is offset towards the convex side of the axis, as Figure 1 shown.

[0032] Different from the axis of a straight pipe being located at its volume center, the volume center of a spiral pipe is not on its axis. That is to say, if the emitting electrode 8 is arranged at the axis of the spiral pipe, for a bubble of the same volume, when the bubble is located inside and outside the spiral pipe, the proportion of the volume of the spiral pipe inside the bubble and the proportion of the volume of the spiral pipe outside the bubble are different, which will result in different measured values of the conductance impedance of the bubble, thus causing the measured conductance impedance value not to have a one-to-one correspondence with the gas holdup. Therefore, to solve the problem of uneven volume distribution around the axis caused by arranging the emitting electrode 8 at the axis, after inserting the emitting electrode 8 into the first connecting pipe 1, it needs to be offset a certain distance outward along the axis of the first connecting pipe 1 so that it is located at the volume center of the spiral pipe. Combining Figure 1 and Figure 2 shown, the calculation of the offset distance h is as follows:

[0033] As Figure 2 shown, for a circle with a radius of r and a center at O(0, R), after rotating one week around the x-axis, the volume of the obtained spiral pipe is:

[0034]

[0035] After offsetting the emitting electrode 8 by a distance h to point O', the volume of the outside of the spiral pipe ABCO' after rotating one week around the x-axis is:

[0036]

[0037] Let V1 = 0.5V 总, that is, ensure that the emission electrode 8 is offset to the volume center of the solenoid after offset. Where R is the spiral radius and r is the inner diameter of the first connecting pipe, both are known quantities. Since the equation form is relatively complex, an iterative method is required for solving.

[0038] The inner diameters of the first connecting pipe 1 and the second connecting pipe 7 are the same as the pipe diameter of the actual solenoid to be measured. The inner diameters of the first connecting pipe 1, the first protection electrode 2, the first insulating ring 3, the receiving electrode 4, the second insulating ring 5, the second protection electrode 6, and the second connecting pipe 7 are the same. The materials of the first protection electrode 2, the receiving electrode 4, the second protection electrode 6, and the emission electrode 8 are copper. The materials of the first insulating ring 3 and the second insulating ring 5 are plexiglass. The first connecting pipe 1 and the second connecting pipe 7 are transparent plexiglass pipes.

[0039] The emission electrode 8 is a filament electrode. The diameter of the emission electrode 8 is 1 mm, and the length of the emission electrode 8 is 100 mm.

[0040] Preferably, a third flange 102 is fixed to the other end of the first connecting pipe 1, and a fourth flange 702 is fixed to the other end of the second connecting pipe 7. The third flange 102 and the fourth flange 702 are used to connect with the solenoid to be measured. That is to say, in use, the conductivity sensor is installed on the solenoid to be measured by using the third flange 102 and the fourth flange 702. The inner diameters of the first connecting pipe 1, the second connecting pipe 7, the first flange 101, the second flange 701, the third flange 102, and the fourth flange 702 are the same.

[0041] In order to make the measurement result more accurate, in use, usually two conductivity sensors of the present invention are installed on the solenoid to be measured. The receiving electrodes 4 of the two conductivity sensors are connected, and the emission electrodes 8 of the two conductivity sensors are connected. That is to say, the two conductivity sensors are connected in parallel in the measurement circuit. Compared with a single conductivity sensor, the fluctuation deviation is lower and the stability is higher.

[0042] During operation, a high-frequency alternating current signal is selected as the excitation signal of the conductivity sensor and input to the emission electrode 8 in the two concentric conductivity sensors, with a fast response speed and a small measurement delay.

[0043] The working principle of the present invention is:

[0044] When the two-phase flow fluid enters the conductivity sensor through the first connecting pipe 1, it flows through the filament emission electrode 8 located at a certain distance outside the axis protrusion. The current establishes an electric field in the fluid to be measured, and the receiving electrode 4 senses the potential difference. The emission electrode 8 and the receiving electrode 4, the first protection electrode 2, and the second protection electrode 6 respectively form electric circuits. A sinusoidal alternating current signal is applied to the emission electrode 8. By measuring the magnitude of the current in the circuit, the total resistance value of the circuit can be obtained. Its equivalent circuit diagram is as Figure 3As shown. The excitation voltage V of the conductivity sensor is applied to the two-phase fluid system. Since the internal resistance of the electrode and the solution resistance are in series, they can be considered as a single resistor. And because the internal resistance of the working electrode is much lower than the solution resistance, it is generally simply referred to as the solution resistance Rs. Therefore, the two-phase fluid system can be disassembled into a series-parallel circuit composed of the resistance Rs of the two-phase fluid, the contact resistances Rct1 and Rct2 generated by the polarization phenomenon when the two electrodes come into contact with the fluid, and the double-layer capacitors C1 and C2 formed when the two electrodes come into contact with the fluid. Among them, the cross-sectional area S of the measured solution is as follows:

[0045]

[0046] When the structure of the flow channel is determined, the conductivity σ of the fluid segment with a length of l is inversely proportional to the magnitude of the fluid resistance R.

[0047] According to the results of the calibration experiment, the conductance impedance value changes monotonically with the change of the gas holdup in the two-phase flow in the helical tube. Under different liquid flow rates, the change trend of the conductance impedance value with the volume gas holdup is slightly different. Through the calibration experiment, the relationship between the conductance impedance value in the present invention and the gas holdup in the helical tube under the corresponding working conditions can be established.

[0048] Finally, it should be noted that: the above-described embodiments are only specific embodiments of the present invention, used to illustrate the technical solutions of the present invention, rather than limiting it. The protection scope of the present invention is not limited thereto. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: any person skilled in the art within the technical scope disclosed by the present invention can still modify the technical solutions recorded in the foregoing embodiments or can easily think of changes, or perform equivalent replacements on some of the technical features; and these modifications, changes or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be covered by the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the protection scope of the claims.

Claims

1. An electrical conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube, characterized in that, It includes a first connecting pipe (1), a first protection electrode (2), a first insulating ring (3), a receiving electrode (4), a second insulating ring (5), a second protection electrode (6), a second connecting pipe (7) and a transmitting electrode (8). The first protection electrode (2), the receiving electrode (4) and the second protection electrode (6) are all tubular, and the curvatures of the first connecting pipe (1), the first protection electrode (2), the receiving electrode (4), the second protection electrode (6) and the second connecting pipe (7) are consistent with the curvature of the spiral tube to be measured. The transmitting electrode (8) is filamentous. The ends of the first connecting pipe (1), the first protection electrode (2), the receiving electrode (4), the second protection electrode (6) and the second connecting pipe (7) are connected in an open-loop sequence. The first insulating ring (3) is arranged between the first protection electrode (2) and the receiving electrode (4), and the second insulating ring (5) is arranged between the receiving electrode (4) and the second protection electrode (6). One end of the transmitting electrode (8) is inserted from one side of the first connecting pipe (1) and extends along the axial direction of the first connecting pipe (1) to the second connecting pipe (7). The other end of the transmitting electrode (8) is located outside the first connecting pipe (1). The part of the transmitting electrode (8) extending along the axial direction of the first connecting pipe (1) is located on the convex side of the axis of the first connecting pipe (1), and the transmitting electrode (8) is at a set distance from the axis of the first connecting pipe (1). , so that the transmitting electrode (8) is located at the volume center of the spiral tube.

2. The conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to claim 1, wherein The set distance The calculation formula is as follows: In the formula, R is the spiral radius; r is the inner diameter of the first connecting pipe.

3. The conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to claim 1, wherein One end of the first connecting pipe (1) is fixed with a first flange (101), and one end of the second connecting pipe (7) is fixed with a second flange (701). After the first flange (101) and the second flange (701) are connected by a bolt screw (9), the first protection electrode (2), the first insulating ring (3), the receiving electrode (4), the second insulating ring (5) and the second protection electrode (6) are pressed between the first connecting pipe (1) and the second connecting pipe (7).

4. The conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to claim 3, characterized in that, The other end of the first connecting pipe (1) is fixed with a third flange (102), and the other end of the second connecting pipe (7) is fixed with a fourth flange (702). The third flange (102) and the fourth flange (702) are used to connect with the spiral pipe to be measured.

5. The conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to claim 4, wherein The inner diameters of the first connecting pipe (1), the second connecting pipe (7), the first flange (101), the second flange (701), the third flange (102) and the fourth flange (702) are the same.

6. The conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to claim 1, characterized in that, The inner diameters of the first connecting pipe (1), the first protection electrode (2), the receiving electrode (4), the second protection electrode (6) and the second connecting pipe (7) are the same.

7. The conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to claim 1, characterized in that, The inner diameters of the first connecting pipe (1), the first protection electrode (2), the first insulating ring (3), the receiving electrode (4), the second insulating ring (5), the second protection electrode (6) and the second connecting pipe (7) are the same.

8. The conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to claim 1, characterized in that, The first connecting pipe (1) and the second connecting pipe (7) are made of transparent plexiglass tubes.

9. The conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to claim 1, wherein The materials of the first protection electrode (2), the receiving electrode (4), the second protection electrode (6) and the emitting electrode (8) are copper.

10. The conductivity sensor for transient measurement of gas holdup in gas-liquid two-phase flow in a spiral tube according to claim 1, characterized in that, The materials of the first insulating ring (3) and the second insulating ring (5) are plexiglass.

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