Volume tube phase flow state monitoring device and method based on electrical capacitance tomography

Abstract

The invention provides a volume tube phase flow state monitoring device and method based on electrical capacitance tomography. Firstly, the invention proposes that an ECT method is introduced into a volume tube to realize gas-liquid two-phase flow distribution state detection for the first time, and breaks through the technical bottleneck that real-time monitoring of an internal flow state cannot be realized by a traditional method. And secondly, non-contact, total-cross-section and dynamic sensing of the phase state of the fluid in the volume pipe is achieved, and higher adaptability and safety are achieved. Meanwhile, the method supports volume fraction estimation and time sequence change analysis, and provides a reference basis for flow metering, working condition diagnosis, anomaly detection and the like. Finally, the technical blank of a traditional volumetric method device in the aspect of multiphase flow measurement precision guarantee is made up, and good engineering practicability and popularization value are achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of instruments and meters, and particularly relates to a device and method for monitoring the multiphase flow state inside a volume tube based on electrical capacitance tomography (ECT). Background Art

[0002] Traditional piston-type volume tubes are primarily used for calibration and verification of liquid or gas flowmeters. They achieve high-precision volume measurement by precisely displacing a piston within a cylinder to establish a traceable volume. However, when dealing with complex fluids (such as gas-liquid mixtures or liquids containing impurities), these devices often struggle to distinguish whether the current measurement segment is a single phase. This indistinguishability directly impacts calibration or measurement reliability, potentially leading to measurement errors, data drift, and even invalid determinations.

[0003] Traditional volume tubes mainly rely on the installation of temperature and pressure sensors to determine working conditions and perform phase state detection and measurement. However, these methods generally have the following shortcomings:

[0004] Intrusive measurement methods interfere with normal flow: For example, temperature and pressure sensors need to be placed inside the volume tube, which may affect the flow field distribution and introduce additional pressure loss.

[0005] The detection method is limited to local or average information: ultrasonic and pressure difference methods can only obtain the overall flow velocity or pressure drop, which is difficult to reflect the specific distribution of different phases on the cross section of the volume tube.

[0006] Poor sensitivity to gas-liquid mixing state and large errors: Especially in low-speed flow and unstable flow patterns (such as plug flow and bubbly flow), traditional methods are prone to response delays or misjudgments, affecting measurement accuracy.

[0007] Unable to achieve visual monitoring of internal flow state: Currently, there is a general lack of non-contact, full-section, real-time identification methods for the gas-liquid phase distribution state inside the volume tube.

[0008] In recent years, electrical capacitance tomography (ECT), a non-invasive imaging technology that reconstructs dielectric distribution based on inter-electrode capacitance changes, has been widely used in process pipelines, multiphase flow monitoring and other fields. Its principle is to set up multiple electrode pairs outside the fluid channel, measure the capacitance values ​​under different excitation combinations, and invert the spatial distribution of the dielectric constant in the measurement area, thereby realizing the visual identification of multiphase components such as gas, liquid, and solid. Summary of the Invention

[0009] To address the shortcomings of the aforementioned existing technologies, the present invention provides a device and operating method for monitoring the multiphase flow state of a volume tube using electrical capacitance tomography (ECT) technology. These devices belong to the fields of industrial process detection and multiphase flow visualization. The device is primarily suitable for monitoring the distribution state of gas-liquid two-phase fluids, such as natural gas, liquefied petroleum gas, and crude oil, in volumetric metering pipelines. It enables non-contact, full-cross-section, dynamic identification of phase changes within the volume tube, and boasts a compact structure, high detection accuracy, and flexible deployment.

[0010] The technical features of the present invention include but are not limited to the following aspects:

[0011] In one aspect, the present invention provides a volume tube phase flow state monitoring device based on electrical capacitance tomography, comprising: a volume tube unit, a capacitance sensing and acquisition unit, and an imaging and calculation unit;

[0012] Each unit is connected in sequence through signal and control links;

[0013] The capacitive sensing and acquisition unit is arranged on the outer wall of the volume tube unit, and is used to obtain the capacitance data of the fluid state in the volume tube unit, and transmit it to the imaging and calculation unit for processing and judgment, and then feed back the judgment result to the volume tube unit to realize state control.

[0014] On the other hand, the present invention also provides a method for monitoring the phase flow state of a volume tube based on electrical capacitance tomography, which is applied to the above-mentioned device and includes the following steps:

[0015] Step 1: The volume control operating system issues a "start detection" command;

[0016] Step 2: After the fluid flows into the volume tube, the electrode array begins to sense and generate mutual capacitance signals;

[0017] Step 3: The data collector collects the mutual capacitance signal, reconstructs the image, and calculates the volume fraction;

[0018] Step 4: Determine whether there is a gas-liquid mixture that affects the measurement accuracy based on the volume fraction; if there is a situation that affects the measurement accuracy, terminate the measurement process; if not, start the measurement process.

[0019] Based on the above technical features, the present invention produces the following beneficial effects:

[0020] 1. This paper first proposed the introduction of the ECT method in a volume tube to detect the distribution state of gas-liquid two-phase flow, breaking through the technical bottleneck of traditional methods that cannot achieve real-time monitoring of internal flow state;

[0021] 2. It realizes non-contact, full-section, dynamic perception of the fluid phase state inside the volume tube, with higher adaptability and safety;

[0022] 3. Support volume fraction estimation and time series change analysis, providing a reference basis for flow measurement, working condition diagnosis, anomaly detection, etc.;

[0023] 4. The phase state inside the tube can be accurately determined at the critical point of the phase change of the fluid inside the tube, and the phase state judgment threshold can be greatly reduced;

[0024] 5. The overall structure is compact and easy to deploy, suitable for promotion and application on engineering sites, and has significant industrial transformation.

[0025] In summary, the present invention fills the technical gap in traditional volumetric devices in ensuring the accuracy of multiphase flow measurement, and has good engineering practicality and promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a schematic diagram of the overall structure of the device according to an embodiment of the present application;

[0027] Figure 2 A schematic diagram of an ECT electrode structure according to an embodiment of the present application;

[0028] Figure 3 This is a complete flow chart of the embodiment of this application.

[0029] Figure numerals: 1. Imaging calculation device; 2. Capacitive data collector; 3. Capacitive sensor; 4. Volume tube operating system; 5. Piston; 6. Start detection photoelectric sensor; 7. End detection photoelectric sensor; 8. Piston-type volume tube cylinder; 9. Protective ring; 10. Pipeline to be tested; 11. Electrode array; 12. Shielding layer. DETAILED DESCRIPTION

[0030] In order to better understand the technical solution of the present invention, the following describes the embodiment of the present invention in detail with reference to the accompanying drawings and the basic principles of electrical capacitance tomography. This embodiment is not intended to be limiting, but serves to clearly illustrate the technical implementation path.

[0031] like Figure 1-Figure 3 As shown, the technical solution of this application aims to introduce the ECT sensing technology traditionally used in process pipelines and test platforms into a special metering device called a volume tube after structural adaptation and functional simplification, so as to realize non-contact, real-time dynamic detection of the internal fluid phase. In view of the significant difference in capacitance between the gas and liquid phases, this application adopts a method of surrounding multiple pairs of electrodes to realize cross-sectional capacitance data acquisition, and completes dielectric constant distribution image reconstruction based on the linear back projection (LBP) algorithm. On this basis, combined with regional filtering and image post-processing strategies, a phase recognition model is constructed to realize rapid identification of gas and liquid phase distribution areas in the fluid and volume fraction estimation. The volume fraction is used as the judgment standard to determine whether there is a detection error problem caused by phase inhomogeneity.

[0032] like Figure 1 and Figure 2 As shown, an embodiment of the present application provides a volume tube phase flow state monitoring device based on electrical capacitance tomography. The device uses the volume tube as the core measurement unit, arranges an electrode array around its outer wall, constructs a capacitive sensing area, and reconstructs the gas-liquid distribution through imaging of the change in cross-sectional dielectric constant, thereby estimating the volume fraction of each phase. If there is any situation that affects the measurement accuracy based on the volume fraction of each phase, the measurement accuracy is guaranteed.

[0033] Furthermore, the device includes a volume tube unit, a capacitive sensing and acquisition unit, and an imaging and computing unit. Each unit is connected sequentially via signal and control links. The capacitive sensing and acquisition unit is located on the outer wall of the volume tube unit and is used to acquire capacitance data of the fluid state within the volume tube unit, transmit it to the imaging and computing unit for processing and judgment, and ultimately feed the judgment results back to the volume tube unit to achieve state control.

[0034] Furthermore, the volume tube unit includes a piston-type volume tube cylinder 8, a start detection photoelectric sensor 6, an end detection photoelectric sensor 7, and a piston 5 assembly. The piston 5 is disposed inside the cylinder 8, and the start detection photoelectric sensor 6 and the end detection photoelectric sensor 7 are installed outside the cylinder 8 and connected to the volume tube operating system 4 via wires.

[0035] Furthermore, the capacitive sensing and acquisition unit includes an electrode array 11, a capacitive sensor 3, a shielding layer 12, and a guard ring 9. The electrode array 11 is mounted on the outer wall of the standard volume section of the volume tube to sense changes in the dielectric constant of the medium and is electrically connected to the capacitive sensor 3 to form a capacitance measurement channel. The electrode array 11 is covered by a shielding layer 12 and has guard rings 9 at both ends. The capacitive sensor 3 is used to collect mutual capacitance information between the electrodes.

[0036] Several ECT electrodes are arranged along the axial or circumferential direction of the outer wall of the volume tube to form a capacitance measurement channel. The electrodes are connected to the capacitance sensing and acquisition unit through a multi-way switch matrix to collect the capacitance changes caused by different phase states in the target area in real time.

[0037] The electrodes are arranged in a symmetrical ring or with equal spacing, which is suitable for a typical cylindrical volume tube structure and can cover the main area of ​​the fluid cross section, thereby ensuring the integrity and representativeness of image reconstruction.

[0038] Furthermore, the imaging and computing unit includes a capacitance data collector 2 and an imaging computing device 1. The capacitance data collector 2 is connected to the capacitance sensor 3 via a circuit to obtain raw capacitance data and transmit it to the imaging computing device 1 for subsequent processing.

[0039] like Figure 2 As shown, the ECT electrode array 11 is evenly distributed along the outer wall of the pipeline 10 to be tested, with 8 to 32 metal electrodes forming a ring arrangement. Each pair of electrodes can form a set of capacitance measurement path systems. The multi-channel switching module dynamically controls the excitation and reception combination to achieve automatic rotation of electrode roles. The mutual capacitance value C between different electrode pairs is ij It is closely related to the dielectric constant distribution inside the fluid. The basic calculation model is:

[0040]

[0041] Where V i represents the voltage of the i-th excitation electrode, Indicates the position within the measurement area The dielectric constant at , are the electric field intensity distributions excited by the excitation electrode and the receiving electrode respectively, and Ω is the measurement cross-sectional area.

[0042] like Figure 3 As shown, the embodiment of the present application further provides a method for monitoring the phase flow state of a volume tube based on electrical capacitance tomography, which is applied to the above-mentioned device, and the method includes the following steps:

[0043] Step 1: The volume control operating system 4 issues a "start detection" instruction;

[0044] Step 2: After the fluid flows into the volume tube, the electrode array 11 starts to sense and generate mutual capacitance signals;

[0045] Step 3: The data collector 2 collects the mutual capacitance signal, reconstructs the image, and calculates the volume fraction;

[0046] Step 4: Determine whether there is a gas-liquid mixture state affecting the measurement accuracy based on the volume fraction: if the volume fraction is unstable and less than the threshold, it is determined that there is a gas-liquid mixture state affecting the accuracy; if the volume fraction is stable and greater than the threshold, it is determined that there is no gas-liquid mixture state affecting the accuracy, and the judgment result is transmitted to the volume tube operating system 4.

[0047] Furthermore, when the device is working, the operator first uses the volume tube operating system 4 to issue a "start detection" instruction. After the control program is started, the capacitance acquisition process is immediately started and the current fluid state is locked after the fluid enters the volume tube cylinder 8.

[0048] After the fluid flows into the volume tube, the electrode array 11 begins sensing and generating mutual capacitance data. Capacitive sensor 3 collects this mutual capacitance data. This data is acquired by capacitance data collector 2 and uploaded to imaging computing device 1, which processes the mutual capacitance data, including image reconstruction, volume fraction calculation, and phase state determination.

[0049] Furthermore, in step 3, image reconstruction utilizes the linear back projection (LBP) method, which has low computational complexity and is suitable for embedded environments. This method is supplemented by correction strategies such as regional filtering and edge enhancement to improve image clarity and boundary recognition accuracy. Pixel classification and discrimination are performed based on the image. By setting dielectric constant thresholds and spatial neighborhood analysis rules, the gas and liquid phases are automatically separated and labeled, and their volume fractions are estimated. Based on this volume fraction, the phase state within the tube is determined to determine whether it meets the inspection requirements.

[0050] Furthermore, image reconstruction uses the linear back projection (LBP) algorithm, which projects the capacitance changes onto a two-dimensional grid. After image reconstruction, the image is binary segmented by setting a dielectric constant threshold. Gas phase regions (low dielectric constant) and liquid phase regions (high dielectric constant) can be automatically identified, and the liquid phase volume fraction can be estimated according to the following formula:

[0051]

[0052] Among them, N liq is the number of liquid phase pixels, N total is the total number of pixels, represents the liquid volume fraction.

[0053] These results can be displayed in real time on the imaging computing device 1 and are also applicable to non-uniform flow patterns such as bubbly flow, plug flow, and stratified flow. Compared to traditional mechanical structures or ultrasonic sensor methods, this device is non-invasive and has a fast signal response, making it suitable for deployment in pipelines containing hazardous media such as natural gas, liquefied gas, two-phase water, and carbon dioxide.

[0054] Further, the step 4 is specifically as follows:

[0055] After calculating the volume fraction, the imaging calculation device 1 determines whether there is a detection error problem caused by phase unevenness: if the current phase volume fraction is unstable or less than the threshold, it is determined that there is a gas-liquid mixture that affects the accuracy, and the judgment result is sent to the volume tube operating system 4 to terminate the measurement to avoid data deviation caused by phase unevenness; if the current phase volume fraction is stably greater than the threshold, it is determined that there is no gas-liquid mixture that affects the accuracy, and the judgment result is sent to the volume tube operating system 4. The volume tube operating system 4 triggers the start detection of the photoelectric sensor 6 to confirm that the fluid has officially entered the metering process, and the metering process is completed when the end detection of the photoelectric sensor 7 is triggered.

[0056] The modular structure of the device can be deployed on edge computing platforms such as industrial controllers, embedded processors, and micro workstations. It features low power consumption, low latency, and online operation, making it suitable for unmanned industrial sites or remote monitoring needs. By dynamically identifying and quantifying the gas-liquid distribution within the volume tube, it improves the accuracy, stability, and safety of volumetric measurement.

[0057] The device is structurally compatible with the existing volume metering system without interfering with the original fluid measurement function. While achieving visual monitoring of the flow state, it does not introduce additional pressure loss or pipeline interference and has good system integration.

[0058] It should be noted that the above implementation modes are preferred examples of the present invention. For ordinary technicians in the relevant technical field, any equivalent replacement, structural adjustment or module integration scheme made without departing from the basic concept of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A volume tube phase flow state monitoring device based on electrical capacitance tomography, characterized in that: include: Volume tube unit, capacitive sensing and acquisition unit, and imaging and computing unit; Each unit is connected in sequence through signal and control links; The capacitive sensing and acquisition unit is arranged on the outer wall of the volume tube unit, and is used to obtain the capacitance data of the fluid state in the volume tube unit, and transmit it to the imaging and calculation unit for processing and judgment, and then feed back the judgment result to the volume tube unit to realize state control.

2. The device according to claim 1, characterized in that The volume tube unit includes: a piston-type volume tube cylinder, a start detection photoelectric sensor, an end detection photoelectric sensor and a piston; The piston is arranged inside the piston-type volume tube cylinder; The start detection photoelectric sensor and the end detection photoelectric sensor are installed outside the cylinder body and are connected to the volume tube operating system through wires.

3. The device according to claim 1, characterized in that The capacitive sensing and acquisition unit includes: an ECT electrode array, a capacitive sensor, a shielding layer and a guard ring; The ECT electrode array is fitted on the outer wall of the standard volume section of the volume tube to sense changes in the dielectric constant of the medium; it is electrically connected to the capacitance sensor to form a capacitance measurement channel, and is covered by a shielding layer, with protective rings at both ends.

4. The device according to claim 3, characterized in that The ECT electrode array is evenly distributed along the outer wall of the pipeline to be tested, with 8 to 32 metal electrodes forming a ring arrangement. Each pair of electrodes forms a capacitance measurement path system, and the excitation and reception combinations are dynamically controlled by a multi-channel switching module to achieve automatic rotation of electrode roles.

5. The device according to claim 4, characterized in that The ECT electrode array is arranged on the outer wall of the pipeline to be tested along its axial direction or circumferential direction.

6. The device according to claim 4 or 5, characterized in that The ECT electrode array is arranged in a symmetrical ring or distributed at equal intervals.

7. The device according to claim 1, characterized in that The imaging and computing unit includes: a capacitance data collector and an imaging computing device; The capacitance data collector is connected to the capacitance sensor via a circuit, and is used to obtain raw capacitance data and transmit it to the imaging computing device for subsequent processing.

8. A method for monitoring phase flow status in a volume tube based on electrical capacitance tomography, applied to a device for monitoring phase flow status in a volume tube based on electrical capacitance tomography as claimed in any one of claims 1 to 7, characterized in that: The steps include: Step 1: The volume control operating system issues a "start detection" command; Step 2: After the fluid flows into the volume tube, the electrode array begins to sense and generate mutual capacitance signals; Step 3: The data collector collects the mutual capacitance signal, reconstructs the image, and calculates the volume fraction; Step 4: Determine whether there is a gas-liquid mixture that affects the measurement accuracy based on the volume fraction; if there is a situation that affects the measurement accuracy, terminate the measurement process; if not, start the measurement process.

9. The method according to claim 8, characterized in that In step 3, the image is reconstructed using a linear back-projection algorithm, which projects the capacitance change onto a two-dimensional grid. After image reconstruction, the image is binary segmented by setting a dielectric constant threshold to automatically identify the gas phase region and the liquid phase region. The liquid phase volume fraction is calculated based on the number of liquid phase pixels and the total number of pixels.

10. The method according to claim 8, characterized in that The step 4 is specifically as follows: After calculating the volume fraction, the imaging computing device determines whether there is a detection error caused by phase inhomogeneity: If the current phase volume fraction is unstable or less than the threshold, it is determined that there is a gas-liquid mixture that affects the accuracy. The judgment result is sent to the volume tube operating system to terminate the measurement to avoid data deviation caused by uneven phase state; If the current phase volume fraction is stably greater than the threshold, it is determined that there is no gas-liquid mixture affecting the accuracy, and the judgment result is sent to the volume tube operating system; the volume tube operating system triggers the start detection photoelectric sensor to confirm that the fluid has officially entered the metering process, and the metering process is completed when the end detection photoelectric sensor is triggered.

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