CN102998343B - Two-phase flow tomography system based on array-type monopole conducting probe - Google Patents

Abstract

The invention discloses a two-phase flow pattern detection system based on an arrayed single-cathode conductance probe. The system includes: a flow pipeline; fixedly installed on the inner wall of the flow pipeline, and includes a plurality of detection points and detection point lead-out lines, The lead wire of each detection point passes through the wall of the flow pipe and is electrically connected to the lead terminal of the outer wall; the multi-channel acquisition device connected with the lead terminal and used to collect the potential value of each detection point; installation An annular anode on the inner wall or inside of a flow channel for applying excitation to the fluid. The invention is simple in principle and reliable, can effectively reduce the uncertainty of flow pattern detection, and can also monitor and record the cross-section phase holdup in real time, and can meet a certain usable accuracy.

Description

A two-phase flow tomography system based on arrayed unipolar conductance probes

technical field

The invention relates to the technical field of flow pattern identification of two-phase pipe flow, in particular to a two-phase flow tomography imaging system based on an arrayed unipolar conductance probe.

Background technique

The phenomenon of two-phase flow exists widely in modern engineering fields such as petroleum and chemical industry. It is of great significance to study the distribution of each phase and flow shape in two-phase flow to better grasp other flow parameters. Drawing on the CT scanning tomography technology in the medical field, it is hoped to obtain real-time tomographic information of flow faults in order to obtain three-dimensional spatiotemporal distribution information of multiphase fluids. Two-phase/multi-phase tomography technology came into being. The application of tomography technology in the measurement of two-phase flow parameters is of great significance to the mechanism research and numerical simulation verification of two-phase flow, and it represents the future development trend of the current multiphase flow parameter detection technology.

Tomography imaging using rays such as X-rays and gamma rays is the earliest developed process tomography technology. Rays passing through the measured section will be attenuated due to medium absorption and scattering, and the tomographic image can be obtained by measuring the attenuation amplitude in different directions and then inversely transforming the projection. This technology is a direct application of medical CT technology in the field of multiphase flow parameter detection. In actual use, its most obvious disadvantage is poor real-time performance. In addition, the cost of using rays is high, and the safety cannot be guaranteed.

Capacitance process tomography is also a process tomography technology that has been studied and applied earlier. Its measurement principle is that different components of the multiphase fluid flowing in the pipeline have different dielectric constants. Capacitance between pairs of electrodes on the surface is used for imaging. For example, the capacitance value measured in the Chinese invention patent ZL01112515.2 is related to the phase distribution of the entire section. This "soft field" property makes image reconstruction very complicated only by the capacitance value, and the use of complex iterative algorithms will consume a lot of time. time to retrieve the cross-sectional image. Due to the dependence on capacitance measurement, this type of sensor is very sensitive to the dielectric constant of the fluid. The dielectric constant is often changed due to the conductive impurities in the fluid, which makes the reconstruction image inevitable and difficult to correct, which affects the imaging quality and the final image. measurement results.

Chinese invention patent CN1595132A describes a capacitive sensor for two-phase flow tomography, which can solve the projection image of the insulating medium in the direction of the wire by measuring the capacitance change of the insulated wires placed in parallel, through the electric rotation or spin device Drive the screen to rotate, so that the projection information in several directions can be obtained, and the flow field image can be obtained through projection inverse transformation. An obvious defect of this method is that the rotation of the sensor itself has an impact on the flow field itself. If the sensor rotates too fast, it will disturb the distribution of the entire flow pattern. The condition of the same position, the projection inverse transformation is out of the question. Moreover, this method is very sensitive to the dielectric constant of the medium, and a slight change in the composition may cause measurement errors.

U.S. Patent US6314373 proposes a new conductance tomography method. The sensitive parts are two layers of stainless steel electrodes parallel to each other. phase distribution. The obvious shortcoming of this method is that it ignores the impact of the bare part other than the intersection point on the conductance of the measured point. For liquids with high resistivity, this shortcoming will seriously affect the accuracy of measurement. Therefore, this method has strict requirements on the liquid environment and is difficult to apply.

However, the method of using a single probe to detect the dispersed phase holdup in two phases has many applications, and the technology is relatively mature. However, the commonly seen applications are only for single-point measurement, and can only roughly estimate the water content and judge the flow pattern based on the signal frequency change. The traditional bipolar impedance probe detects the resistivity of a local point inside the flow channel through two electrodes that are insulated from each other and are close to each other. Due to the small size of the electrodes, the electrolytic reaction makes the anode easily corroded and has poor durability.

Contents of the invention

The purpose of the present invention is to improve the traditional single-root double-electrode probe and combine it with the tomographic imaging method to propose a system different from the previous flow pattern measurement, which can realize online real-time measurement. Oil-water/gas-water two-phase pipe flow section image (tomography) and more accurate calculation of water cut.

The present invention proposes a two-phase flow pattern detection system based on an arrayed single-cathode conductivity probe, which includes:

The flow pipe 1 is used to provide a two-phase fluid with a large difference in resistivity to flow therein;

The arrayed single-cathode conductivity probe 4 is fixedly installed on the inner wall of the flow pipe 1, and includes a plurality of detection points and detection point lead lines arranged in a spatial array. Each detection point has only one pole, which is used as a cathode, and each The lead wires of each detection point pass through the pipe wall of the flow pipe 1 and are electrically connected to the lead terminals on the outer wall of the flow pipe 1;

The multi-channel acquisition device 2 is connected to the lead terminal on the outer wall of the flow pipe 1, and is used to collect the potential value of each detection point, and compress the potential detection results of all detection points each time;

The annular anode 5 is installed on the inner wall of the flow pipe 1 or inside the pipe, and is used to apply continuous high voltage excitation or pulse excitation to the fluid;

When the detection system is working, each detection point of the array type single cathode conductance probe 4 is used as a cathode, and when a fluid with a small resistivity flows through the detection point, there is a gap between the detection point and the annular anode 5. The passage is formed by the fluid with small resistivity, and the multi-channel acquisition device 2 records the detection point as a high level; when the fluid with high resistivity flows through the detection point, the gap between the detection point and the annular anode 5 is Insulation, the multi-channel acquisition device 2 records the detection point as a low level, so as to obtain the distribution of the medium at each position in the corresponding section of the flow pipeline 1 .

The invention utilizes the obvious difference in the resistivity of the flowing medium to apply continuous or pulse voltage excitation to the pipe section to be tested through the anode, and each detection point of the conductivity probe is arranged in a certain cross-section inside the pipe in various forms of arrays. The matching circuit detects the circuit on-off situation of each detection point, and can distinguish the type of fluid medium near each detection point. By quickly scanning the detection results of each detection point on the section to obtain the fluid medium distribution near each detection point, the flow tomographic image at this time can be obtained immediately without image reconstruction operations.

Compared with the flow sensor device in the prior art, the present invention has the following advantages:

(1) Intuitively present the real-time distribution image of the flow section, which is beneficial to the human visual recognition of the flow pattern, and also provides more accurate and rich data for the computer to judge the flow pattern;

(2) Each detection point of the cathode probe works independently without interfering with each other. Each detection point has an independent conduction circuit and shares the same anode. The components are simple, the principle is simple and reliable, easy to understand, and easy to realize;

(3) By sacrificing the anode, the effect of protecting the precision cathode is achieved, and because the anode is large in size and easy to replace, the electrical corrosion problem of the impedance probe is solved;

(4) The image reconstruction process does not require complex calculation inversion, and can be controlled only by a single-chip microcomputer, saving costs.

The two-phase flow tomography system of the array type unipolar conductance probe of the present invention improves the traditional bipolar probe method and combines with the tomography method, and can realize online real-time measurement of the two-phase flow section image (tomography imaging) and perform more accurate water cut calculations. It can be applied to flow pattern discrimination of two-phase pipe flow, research on flow pattern evolution mechanism, real-time water cut detection, etc. If two array probes of the same type are continuously installed in the pipeline and combined with the cross-correlation algorithm, it is even possible to describe the velocity of each phase of flow and the slippage velocity between phases.

Description of drawings

Fig. 1 is a structural diagram of a two-phase flow pattern detection system based on an arrayed single-cathode conductivity probe according to an embodiment of the present invention.

Fig. 2 is a schematic diagram of the electrolysis reaction involved in the present invention.

Fig. 3 is a schematic diagram of an array-type single-cathode conductivity probe applied in a square pipeline and arranged in a matrix according to an embodiment of the present invention.

Fig. 4 is a schematic diagram of an array-type single-cathode conductivity probe applied in a circular pipeline with radially arranged detection points according to an embodiment of the present invention.

Fig. 5 is a schematic diagram of an array type single-cathode conductance probe realized by a flexible wire technology according to an embodiment of the present invention.

Fig. 6 is a schematic diagram of a two-phase flow phase separation velocity detection system composed of two sets of arrayed conductivity probes according to an embodiment of the present invention.

Detailed ways

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be described in further detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

Fig. 1 is a structural diagram of a two-phase flow pattern detection system based on an arrayed single-cathode conductance probe according to an embodiment of the present invention. As shown in Fig. 1, in an embodiment of the present invention, The two-phase flow pattern detection system of the probe includes: flow pipeline 1, multi-channel acquisition equipment 2, computer 3, array type single cathode conductivity probe 4 and annular anode 5, used to know the real-time flow of the two-phase flow medium form, including:

The flow pipeline 1 is used to provide two-phase fluids of different media (such as oil-water or gas-water, the present invention will be described below using the two-phase fluid of oil and water as an example) to flow therein, and the resistivities of different media in the flow medium are different. And there is a big difference, in which the resistivity of water is small, and the resistivity of oil phase/gas phase is large;

The arrayed single-cathode conductance probe 4 is fixedly installed on the inner wall of the flow pipe 1, and the arrayed single-cathode conductance probe 4 has a relatively large number of detection points, and each detection point requires an independently insulated lead wire , in order to reduce the interference of the lead wire to the flow field, it is necessary to reduce the wire diameter of the lead wire as much as possible, and the lead wire passes through the pipe wall of the flow pipe 1 and is electrically connected (such as welded) to the outer wall of the flow pipe 1 On the lead terminal, the above fixed structure is beneficial to protect the soft lead wire from being broken;

The arrayed single-cathode conductance probe 4 mainly includes detection points arranged in a spatial array, lead wires of the detection points and an insulating solid skeleton. The structural features of the detection points are very simple, and any exposed metal point can be used as a detection point. point. If the core of the wire end covered with the insulating layer is exposed, the exposed metal core can be used as a detection point. The detection point and the insulated lead wire are fixed on the insulated solid skeleton. Each detection point has only one pole. When the system is working, it is used as the cathode, and all the cathodes share one anode; Figure 1 shows a method for realizing the array arrangement of detection points-flexible wiring method. The process details can be found in For the description of Figure 5 below, the arrangement of detection points is not limited to a specific arrangement, as long as it is arranged in a spatial array, such as radial arrangement, axial arrangement, square matrix arrangement, etc. The distance between each detection point can be equal or unequal, and each detection point is independent of each other. The array type single cathode conductance probe 4 is insulated except the detection point is exposed, and the rest of the probe is insulated.

In addition, the arrayed single-cathode conductivity probes 4 can be used alone, or in multiple groups to achieve different measurement purposes. For example, what is shown in Fig. 5 is a two-phase flow phase separation velocity detection device composed of two sets of array probes.

The multi-channel acquisition device 2 is connected to the lead terminal on the outer wall of the flow pipeline 1, for example, connected to the lead terminal on the outer wall of the flow pipeline 1 through a multi-core cable, so as to connect the multi-channel acquisition device 2 to the array unit. Each detection point on the cathode conductance probe 4 is connected; the multi-channel acquisition device 2 is used to collect the potential level of each detection point at high speed, and compresses the potential detection results of all detection points each time, and sends it to Computer or stay for follow-up processing, described multi-channel acquisition equipment can utilize multi-channel acquisition card, multi-channel acquisition control panel, data acquisition equipment such as single-chip microcomputer;

The computer 3 is connected to the output end of the multi-channel acquisition device 2, for example, it can be connected to the output end of the multi-channel acquisition device 2 through a standard serial communication protocol via a serial port line, so as to receive and decompress the multi-channel in real time. Collect the data sent by the device 2, and display the real-time cross-sectional image of the flow pipeline 1 according to the detection results and geometric positions of each detection point; the computer 3 can also reconstruct the result according to the cross-sectional image, according to the average occupied area of each detection point The cross-sectional area of the two-phase flow is calculated to calculate the cross-sectional phase distribution rate of the two-phase flow, that is, the real-time information of each phase holdup rate. The annular anode 5 is installed on the inner wall of the flow pipe 1 or inside the pipe (due to its arbitrariness, it is not limited to being installed on the inner wall of the pipe), and is used to apply continuous high voltage excitation (such as a voltage of 12V) to the fluid. Excitation) or pulse excitation (the pulse frequency is related to the acquisition capability of the multi-channel acquisition device 2); the zero-potential end of the loaded voltage excitation is connected with the zero-potential end of the multi-channel acquisition device 2 described below to maintain the relationship between the two The voltage reference zero point is the same; in the electrolysis reaction, the annular anode 5 is slowly corroded as a corrosion pole, and each detection point of the array type single cathode conductance probe 4 is protected as a cathode (the electrolysis reaction can refer to the illustrate). The annular anode 5 can be installed on the upstream of the arrayed single-cathode conductance probe 4, or can be installed on the downstream of the arrayed single-cathode conductance probe 4, and the installation position is less than 2 times the inner diameter of the pipeline from the probe. should. The material of described annular anode 5 can be conductive materials such as copper, aluminum, stainless steel; Because the present invention adopts the design of independent anode, therefore, the thickness of described annular anode 5, shape all can be designed according to pipeline shape, make the inner wall of anode and The inner walls of the pipes overlap and are connected to the pipes in the form of flanges to reduce the influence on the flow field.

The "single cathode" concept of the arrayed single cathode conductance probe 4 means that each independent detection point of the probe has only one pole instead of two poles, and this pole is used as a cathode in the measurement circuit. A certain detection point of the arrayed single-cathode conductivity probe 4 is only responsible for detecting the potential level of the fluid component in contact with it, and then judges the fluid component near this detection point by comparing with the threshold potential.

When the detection system is in operation, each detection point of the array type single cathode conductance probe 4 is used as a cathode, and through the excitation of the anode, the water body in contact with the anode is excited to a high potential, while the gas phase or oil phase is Low level due to low resistivity. That is to say, when the conductive fluid flows through a detection point of the arrayed single-cathode conductivity probe 4, the exposed metal detection point is covered by water, and a passage is formed between the cathode detection point and the anode by means of a continuous water phase. The channel acquisition device 2 measures this point (such as utilizing its internal digital selection device to measure, at this moment, the output value of the digital selection device is one), and obtains a high-level signal by recording the multi-channel acquisition device 2; when the insulating medium When (such as oil or gas) flows through the detection point on the probe, the exposed metal detection point is covered by the insulating medium, the cathode and the anode are insulated, and a path cannot be formed. The internal multi-channel acquisition device 2 The digital selection device measures this point (at this time, the output value of the digital selection device is zero), and the low-level signal is obtained by recording through the multi-channel acquisition device 2 . In this way, the multi-channel acquisition device 2 can measure the data of each detection point through high-speed scanning, that is, the potential level, so that the type of medium at each position in the corresponding section of the flow pipeline 1 can be known, so as to obtain the corresponding value of the flow pipeline 1. The distribution of the medium in the section, that is, the distribution of the two phases, and the detected data can be further sent to the computer 3, and the real-time image display of the two-phase distribution on the entire pipe flow section can be obtained, so as to obtain the flow pipe 1 Cross-sectional tomographic image. Due to the one-to-one correspondence between the media type and the detection results, the image reconstruction process does not require complex algorithms, and can be controlled by a small single-chip microcomputer.

In the present invention, due to the electrolysis reaction in water, the anode is slowly corroded by the principle of electrolysis reaction in the water environment, and the detection point of the probe as the cathode will be protected, so as to protect the cathode probe and extend the The service life of the probe and the purpose of reducing the replacement cost of the probe; the volume of the anode is much larger than that of the cathode, which greatly enhances the corrosion resistance of the entire tomographic imaging system; the anode is independent, for example, it can be designed to be easily disassembled The flange structure can be replaced directly after damage or serious damage, without making changes to the cathode.

Fig. 2 is the schematic diagram of the electrolytic reaction involved in the present invention, in Fig. 2, A is the anode ring that material is copper, and B is a schematic independent cathode detection point, under the excitation of power supply, the anode voltage is high, and the cathode voltage is low , the free ^OH in water moves from the cathode to the anode under the action of the electric field force, copper loses two electrons and becomes copper ions, and combines with hydroxide ions to form copper hydroxide precipitate (trace amount), the cathode releases electrons, and the free Hydrogen ions are combined to generate hydrogen bubbles (trace amounts). According to the principle of the above electrolysis reaction, the anode metal will be corroded slowly, while the cathode material will be protected.

Fig. 3 is a schematic diagram of an array-type single-cathode conductivity probe applied in a square pipeline and arranged in a matrix according to an embodiment of the present invention. In Fig. 3, A represents the ring-shaped anode metal block, B represents the flow pipe, and C represents the arrayed single-cathode conductivity probe. Since the cross-section of the square pipe is rectangular, the application of the array probe to the rectangular cross-section can make the arrangement of the detection points more uniform and make the measurement results of the water holdup information more accurate. Therefore, the oil phase area in the measurement image results can be used The water holdup information in two-phase flow can be simply calculated with the water phase area.

Fig. 4 is a schematic diagram of an array type single-cathode conductivity probe applied in a circular pipeline in which the detection points are radially arranged according to an embodiment of the present invention. In Fig. 4, A is a bare metal detection point, and B is an insulated one. The supporting frame, C is the clamping section of the array probe, the entire probe is similar to a gasket, and the installation can be completed only by clamping the probe between the two flanges of the pipeline. The detection points are arranged on the radial insulating frame according to certain rules, and each detection point is connected to the outside of the array probe through the insulated lead wire attached to the surface of the frame or buried inside the frame, and connected to the subsequent circuit through the lead terminal. Due to the axisymmetric nature of the circular array, this arrangement method can more accurately describe the flow state of the circular cross-section pipeline, such as the two-phase flow in the vertical circular cross-section pipeline.

Fig. 5 is a schematic diagram of an array-type single-cathode conductance probe implemented by flexible wiring technology and arranged in a matrix according to an embodiment of the present invention. In Figure 5, C is the ring-shaped anode metal block, B is the insulated cable fixing block, and A is the cable probe. Utilize the flexible wiring process to print the copper wire on the heat-resistant and corrosion-resistant polyimide substrate, and then cover the surface with a polyimide film for insulation, only exposing the end of the copper wire , as a metal detection point. This process can compress the thickness of the sheet-shaped cable structure to about 0.1mm, and each sheet-shaped cable structure can accommodate less than 20 detection points. By arranging multiple lines in parallel or radially, an array of detection points can be easily formed, which can realize the judgment of phase distribution in a section inside the pipeline. The flexible cable technology perfectly combines the detection point, the lead-out line, and the insulating support frame. Due to the thin thickness, it will not have a significant impact on the flow field.

Fig. 6 is a schematic diagram of a two-phase flow phase separation velocity detection device composed of two sets of arrayed single-cathode conductivity probes according to an embodiment of the present invention. In Figure 6, A is the anode, B and B* are an arrayed single-cathode conductivity probe module, C and C* are flow pipes, and D is a correlator, which is used to detect the data of the two sensors. Anode A is installed between the two probes and shared by the two probes. The distance between the two probe detection planes is L, and L is small enough that when the fluid flows through the two sets of cables, its flow state (such as the distribution of each phase, the size and position of oil bubbles, etc.) does not change significantly. When oil bubbles or air bubbles pass through two groups of array probes sequentially, two images with the closest shape will be formed in turn, and the two images can be found through the cross-correlation algorithm. Since the time difference T is also known, through V=L /T can get the oil phase/gas phase separation velocity dispersed in the two-phase flow.

The specific embodiments described above have further described the purpose, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above descriptions are only specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (10)

1. the two phase flow pattern detection system based on array type single negative electrode conducting probe, is characterized in that, this system comprises:

Flow duct (1), flows therein for offering the two-phase fluid that resistivity contrasts is very large;

Array type single negative electrode conducting probe (4), be fixedly installed on the inwall of described flow duct (1), comprise and be a plurality of check points and the check point extension line that space array is arranged, each check point only has a utmost point, as negative electrode, each check point extension line is electrically connected through the tube wall of described flow duct (1) and the lead terminal of described flow duct (1) outer wall;

Multichannel collecting equipment (2) is connected with the lead terminal of described flow duct (1) outer wall, for gathering the potential value of each check point, and the potentiometric detection result for whole check points is each time compressed;

Circular anode (5) is installed on inner-walls of duct or the pipe interior of described flow duct (1), is used to described fluid to apply lasting high voltage excitation or pulse excitation;

Described detection system is when work, each check point of described array type single negative electrode conducting probe (4) is as negative electrode, when the little fluid of resistivity flows through described check point, between check point and described circular anode (5), by the little fluid of resistivity, form path, it is high level that described multichannel collecting equipment (2) records this check point; When the large fluid of resistivity flows through described check point, between check point and described circular anode (5), be insulated, it is low level that described multichannel collecting equipment (2) records this check point, thereby obtains the dielectric distribution situation of each position in described flow duct (1) respective cross-section.

2. the two phase flow pattern detection system based on array type single negative electrode conducting probe according to claim 1, is characterized in that, the check point of described array type single negative electrode conducting probe (4) is exposed metal dots, other SI semi-insulations.

3. the two phase flow pattern detection system based on array type single negative electrode conducting probe according to claim 1, is characterized in that, described array type single negative electrode conducting probe (4) also comprises solid insulation skeleton, for fixed test point and check point extension line.

4. the two phase flow pattern detection system based on array type single negative electrode conducting probe according to claim 1, it is characterized in that, described detection system also comprises computing machine (3), be connected with the output terminal of described multichannel collecting equipment (2), the data that multichannel collecting equipment (2) sends for receiving in real time, described in decompress(ion), and according to the testing result of each check point and geometric position, show the real-time cross-sectional image of described flow duct (1).

5. the two phase flow pattern detection system based on array type single negative electrode conducting probe according to claim 4, it is characterized in that, described computing machine (3) is also further according to described real-time cross-sectional image, and the area of section on average occupying according to each check point calculates diphasic flow area of section ratio.

6. the two phase flow pattern detection system based on array type single negative electrode conducting probe according to claim 1, it is characterized in that, the zero potential end UNICOM of the zero potential end of the voltage drive that described circular anode (5) loads and described multichannel collecting equipment (2), to keep both Voltage References identical zero point.

7. the two phase flow pattern detection system based on array type single negative electrode conducting probe according to claim 1, it is characterized in that, described circular anode (5) is installed on upstream or the downstream of described array type single negative electrode conducting probe (4), and the distance between described array type single negative electrode conducting probe (4) is less than the twice of flow duct (1) internal diameter, its inner wall shape is consistent with flow duct (1) inwall, is fixedly mounted in flow duct (1).

8. the two phase flow pattern detection system based on array type single negative electrode conducting probe according to claim 1, is characterized in that, the material of described circular anode (5) is conductive material.

9. the two phase flow pattern detection system based on array type single negative electrode conducting probe according to claim 1; it is characterized in that; in described detection system work; described circular anode (5) is slowly corroded as the corrosion utmost point, and each check point of described array type single negative electrode conducting probe (4) is protected as negative electrode.

10. the two phase flow pattern detection system based on array type single negative electrode conducting probe according to claim 1, is characterized in that, described array type single negative electrode conducting probe (4) uses separately or many groups are common uses.