A three-dimensional capacitance array sensor that is resistant to high voltage and low temperature

Abstract

The application provides a high-pressure-resistant and low-temperature-resistant three-dimensional capacitive array sensor, comprising: an external structure, a polytetrafluoroethylene tube, an auxiliary dielectric, a capacitive array sensor and a signal lead; the external structure is fixedly connected with the capacitive array sensor, and the auxiliary dielectric and the signal lead are connected between the external structure and the capacitive array sensor; the polytetrafluoroethylene tube is located in the external structure and is fixedly connected with the external structure and the capacitive array sensor through the auxiliary dielectric. The pressure resistance of the sensor provided by the application can reach 4 MPa, and the temperature resistance can reach-190 DEG C. By extending the axial length of the two end electrodes and shortening the axial length of the middle layer electrode, the three-dimensional multilayer electrode array sensor is optimized, the conformal transformation principle is used to guide and select the axial length proportion of different layer electrodes, the sensitivity distribution of the center region of the to-be-measured sensitive field is more uniform, and then the axial image reconstruction accuracy and resolution of the center region are improved.

Description

Technical Field

[0001] The invention belongs to the field of sensors and test measurement, and in particular relates to a three-dimensional capacitance array sensor that is resistant to high voltage and low temperature. Background Art

[0002] Multiphase flow refers to a fluid state characterized by the mixed flow of gas, liquid, and solid phases. It is commonly found in a wide range of fields, including energy, chemical engineering, healthcare, and aerospace. Real-time monitoring of multiphase flow system parameters serves the regulation and control of the overall system and is a crucial guarantee for industrial production safety. Real-time monitoring of the state parameters of different types of multiphase fluids shares technical similarities. For example, gas-liquid two-phase flow is a typical multiphase flow state and can be generally categorized as heterogeneous gas-liquid two-phase flow or homogeneous gas-liquid two-phase flow, depending on whether the two phases have the same medium. The former is common in the petrochemical industry, involving oil-gas and water-gas two-phase flows; the latter is common in aerospace energy, healthcare, and industrial production, involving the liquefied transportation of hydrogen, nitrogen, oxygen, carbon dioxide, and noble gases. Because liquefied gas generally has a low latent heat and low phase transition temperature, it is prone to vaporization even under high-pressure and low-temperature transportation, resulting in gas-liquid two-phase flow. This phenomenon significantly impacts the transportation safety of liquefied gas, making real-time monitoring of the gas-liquid two-phase flow generated during its transportation crucial.

[0003] The flow characteristics of gas-liquid two-phase flow are extremely complex, and accurate monitoring of its state parameters remains a technical challenge. Specifically, the following are the main problems: (1) The phase states are complex and changeable: During the gas-liquid two-phase transfer process, different phases interact with each other, forming a non-steady-state interface, and unpredictable material, momentum and energy exchange occurs at the interface. Homogeneous gas-liquid two-phase flow under high pressure will also face the situation of gas-liquid phase conversion affected by temperature. (2) There are many parameters to be measured: Compared with single-phase fluid, gas-liquid two-phase flow has more state parameters, including flow type, phase fraction, flow rate and differential pressure, etc. Therefore, it is difficult to accurately monitor all parameters at the same time, and its parameter monitoring method is not exactly the same as that of single-phase fluid. (3) The parameters to be measured are prone to change: The flow state of the gas-liquid two-phase flow is affected by the physical properties of the single-phase fluid (such as density and viscosity). State parameters such as fluid flow rate and phase fraction often have a large range of change and change speed, making it difficult to establish a unified model for the entire flow process; (4) The measurement environment requirements are harsh: Compared with many other fluids, the homogeneous gas-liquid two-phase flow generated during the transportation of liquefied gas has more stringent requirements on the measurement environment. It usually requires the sensor to have the characteristics of high pressure resistance and low temperature resistance, which is a difficulty in technical implementation.

[0004] Currently, three-dimensional capacitance imaging (3D-capacitance imaging) is a widely used method in the field of gas-liquid two-phase flow monitoring. This technology, an important method of electrical tomography (ET), typically involves placing a spatial electrode array outside the measured field. This array measures the capacitance between each electrode pair and, combined with relevant image reconstruction algorithms, inverts the three-dimensional dielectric constant distribution of the measured field, thereby obtaining information about the actual material distribution and physical characteristics within the measured field. This technology offers advantages such as simple structure, low production cost, non-invasive measurement, good real-time performance, and strong environmental adaptability. Therefore, it is also widely used in scenarios such as fluidized bed solid particle concentration monitoring, combustion state monitoring, and formation mineral exploration. However, due to the "soft field" effect of 3D-capacitance imaging and the significant influence of measurement errors on the inversion process, it places extremely high demands on the design of the capacitance array sensor arrangement. In particular, traditional congruent electrode arrays suffer from poor axial resolution and large nonlinear distortion of the reconstructed image. The present invention is committed to solving the above-mentioned problems and proposes a design and optimization method of a high-pressure and low-temperature resistant three-dimensional capacitive array sensor for real-time monitoring of the liquefied gas transportation process. It should be noted that the present invention is not only suitable for monitoring the gas-liquid two-phase fluid state with stricter measurement environment requirements, but also suitable for monitoring processes of multi-phase fluid states such as gas-solid, liquid-solid, and gas-liquid-solid with more relaxed measurement environment requirements. Summary of the Invention

[0005] To solve the above technical problems, the present invention proposes a three-dimensional capacitive array sensor that is resistant to high pressure and low temperature. By reconstructing the relative dielectric constant distribution changes in the core area of ​​the sensitive field to be measured by the capacitive array sensor, the state change information of the multiphase fluid in the area is obtained, and the state parameters (flow type, flow velocity and phase fraction) during its transmission process are monitored.

[0006] To achieve the above-mentioned object, the present invention provides a three-dimensional capacitance array sensor that is resistant to high voltage and low temperature, comprising: an external structure, a polytetrafluoroethylene tube, an auxiliary dielectric, a capacitance array sensor, and a signal lead;

[0007] The external structure is fixedly connected to the capacitive array sensor, and the auxiliary dielectric and the signal lead are connected between the external structure and the capacitive array sensor;

[0008] The polytetrafluoroethylene tube is located in the external structure and is fixedly connected to the external structure and the capacitive array sensor through the auxiliary dielectric.

[0009] Optionally, the external structure includes a large flange, a small flange, bolts, screw rods, nuts and a metal shell;

[0010] The large flanges are located on both sides of the capacitive array sensor and are detachably connected via the bolts, screws and nuts;

[0011] The small flanges are located on both sides of the large flange and are fixedly connected to the large flange;

[0012] The metal shell is located on the outer surface of the capacitive array sensor, and the auxiliary dielectric is connected between the metal shell and the capacitive array sensor.

[0013] Optionally, the capacitive array sensor includes N layers of annular electrode arrays, and each layer of the annular electrode array includes M electrodes;

[0014] The annular electrode arrays in different layers are arranged in sequence along the axial direction of the outer wall of the polytetrafluoroethylene tube, and the electrodes in the same layer are arranged at equal intervals along the circumferential direction of the outer wall of the polytetrafluoroethylene tube, forming a three-dimensional N-layer annular electrode array.

[0015] Optionally, the signal lead is connected to a lead interface, one end of the signal lead is connected to the electrode, and the other end is connected to the metal shell through the lead interface, and the lead interface is embedded in the metal shell.

[0016] Optionally, the axial length of the electrodes in the three-dimensional N-layer annular electrode array is obtained based on a conformal transformation.

[0017] Optionally, the axial length of the electrodes in the three-dimensional N-layer annular electrode array is obtained by:

[0018] The longitudinal section of the polytetrafluoroethylene tube is regarded as a straight line group in a first complex plane, and the electrodes of different layers in the three-dimensional N-layer annular electrode array are regarded as line segments on the straight line group;

[0019] The straight line group is mapped into a circle in a second complex plane, and the line segments are mapped into arcs on the circle, and the axial length of the electrode is obtained based on the arcs.

[0020] Optionally, mapping the straight line group in the first complex plane into a circle in the second complex plane by the conformal transformation;

[0021] The mapping expression is:

[0022]

[0023] Wherein, e is a natural constant, r is the radius of the polytetrafluoroethylene tube, i is an imaginary unit, z is the complex coordinate of the longitudinal section of the tube before conformal transformation, and ω is the complex coordinate of the longitudinal section of the tube after conformal transformation.

[0024] Optionally, obtaining the electrode axial length based on the arc includes: making the arc mapped by the line segment in the second complex plane have a central angle and an arc length with a fixed proportional relationship, performing an inverse transformation on the arc to obtain the electrode axial length,

[0025] The inverse transform is:

[0026]

[0027] Wherein, h is the modulus of the imaginary part of one endpoint of the electrode in the first complex plane, and θ is the central angle of the arc determined by the endpoint of the electrode and the real axis of the coordinate in the second complex plane.

[0028] Compared with the prior art, the present invention has the following advantages and technical effects:

[0029] (1) The capacitive array sensor has a specific axial electrode length and has the same electrode arc length in the complex domain after being mapped by a specific conformal transformation. Since the conformal transformation does not change the measurement characteristics of the capacitance, the sensor maintains the same characteristics in the complex domain before mapping. Therefore, compared with traditional capacitive array sensors with equal axial electrode lengths, the sensor proposed in the present invention has a more uniform sensitivity distribution characteristic within the measured field and a higher axial resolution. In addition, the present invention is original in applying conformal transformation to the optimization of the axial lengths of electrodes in different layers of a three-dimensional multilayer capacitive sensor.

[0030] (2) The sensor structure can withstand a pressure of up to 4 MPa and a temperature of up to -190°C, exhibiting excellent electrical response characteristics and being suitable for measuring state parameters of high-pressure or low-temperature gas-liquid two-phase flows. Because other types of multiphase fluids typically require lower measurement environments, the present invention is also applicable to monitoring their state parameters, indicating a certain degree of universality. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The accompanying drawings, which constitute part of this application, are intended to provide a further understanding of this application. The exemplary embodiments and descriptions of this application are intended to explain this application and do not constitute an improper limitation on this application. In the accompanying drawings:

[0032] Figure 1 This is a schematic structural diagram of a high-voltage and low-temperature resistant three-dimensional capacitive array sensor according to an embodiment of the present invention;

[0033] Figure 2 Schematic diagram of a longitudinal section of a pipeline in a complex domain before and after conformal transformation mapping according to an embodiment of the present invention;

[0034] Figure 3 Schematic diagram of a special example of conformal transformation according to an embodiment of the present invention;

[0035] Figure 4Schematic diagram of the corresponding relationship between electrode parameters before and after conformal transformation mapping according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments in this application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0037] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0038] like Figure 1 As shown, the present invention provides a three-dimensional capacitive array sensor that is resistant to high pressure and low temperature, including: an external structure, a polytetrafluoroethylene tube, solid glue, a capacitive array sensor, and a signal lead; the external structure is fixedly connected to the capacitive array sensor, and an auxiliary dielectric and a signal lead are connected between the external structure and the capacitive array sensor; the polytetrafluoroethylene tube is located in the external structure and is fixedly connected to the external structure and the capacitive array sensor through the auxiliary dielectric.

[0039] The external structure is used to provide support and electromagnetic shielding for the capacitance array sensor. The solid glue is used as an auxiliary dielectric between the metal housing and the capacitance array sensor. The capacitance array sensor is used to measure the parameters of gas-liquid two-phase fluids. The signal lead and lead interface are used to connect the metal housing and the capacitance array sensor. The polytetrafluoroethylene tube is used for the flow of gas-liquid two-phase fluids.

[0040] It should be noted that the present invention is not only applicable to gas-liquid two-phase fluid state monitoring with stricter measurement environment requirements, but is also applicable to gas-solid, liquid-solid, gas-liquid-solid and other multiphase fluid state monitoring processes with looser measurement environment requirements.

[0041] Furthermore, the external structure includes a large flange, a small flange, bolts, screws, nuts and a metal shell; wherein the large flange is fixed to both sides of the capacitive array sensor by bolts, screws and nuts; the small flange is fixed to both sides of the large flange; the large flange, small flange, bolts, screws and nuts are used to provide stable support for the capacitive array sensor; the metal shell is located on the outer surface of the capacitive array sensor, and is used to provide an electromagnetic shielding measurement environment for the capacitive array sensor.

[0042] The polytetrafluoroethylene tube is wrapped in a metal shell, fastened at both ends by large flanges, and the metal shell and the large flange are welded; finally, solid glue with a constant dielectric constant is poured through the glue filling port on the metal shell to fix and seal the polytetrafluoroethylene tube, electrode array and lead wires.

[0043] Furthermore, the capacitive array sensor includes N layers of annular electrode arrays, each layer of the annular electrode array includes M electrodes; wherein N is an integer not less than 3, and M is an integer not less than 4;

[0044] The annular electrode arrays in different layers are arranged in sequence along the axial direction of the outer wall of the polytetrafluoroethylene tube, and the electrodes in the same layer are arranged at equal intervals along the circumferential direction of the outer wall of the polytetrafluoroethylene tube, forming a three-dimensional N-layer annular electrode array.

[0045] Furthermore, the signal lead is connected to a lead interface, one end of the signal lead is connected to the electrode, and the other end is connected to the metal shell through the lead interface, and the lead interface is embedded in the metal shell.

[0046] Furthermore, the N-layer annular electrode array further includes a preset electrode axial length;

[0047] The electrode axial length is obtained based on the conformal transformation method.

[0048] Furthermore, conformal transformation methods include:

[0049] The longitudinal section of the polytetrafluoroethylene tube is regarded as a straight line group in the first complex plane, and the electrodes of different layers in the three-dimensional N-layer annular electrode array are regarded as line segments on the straight line group;

[0050] The straight line group is mapped to a circle in the second complex plane, and the line segments are mapped to arcs on the circle. The electrodes in different layers are regarded as multiple line segments on the straight line group, which are mapped to multiple arcs on the circle. The axial length of the electrode is obtained based on the arcs.

[0051] Furthermore, mapping the straight line group to a circle in the second complex plane includes: translation, rotation, and a transformation process of mapping the straight line to a ray and mapping the straight line to a circle.

[0052] Furthermore, obtaining the axial length of the electrode based on the arc includes: making the arc mapped by the line segment in the second complex plane have a central angle and arc length with a fixed proportional relationship (generally the same or similar central angle and arc length), performing an inverse transformation on the arc to obtain the axial length of the electrode.

[0053] This embodiment provides a mechanical structure design method for a three-dimensional capacitive array sensor with a withstand voltage of up to 4 MPa, and proposes a method for optimizing the electrode axial length parameters based on conformal transformation, thereby improving the overall axial resolution of the sensor and enabling more accurate measurement results in the core area of ​​the sensitive field to be measured.

[0054] like Figure 1As shown, this embodiment provides a three-dimensional capacitive array sensor that is resistant to high pressure and low temperature, including five parts: an external structure, a polytetrafluoroethylene tube, a solid glue injected into the gap between the external structure and the polytetrafluoroethylene tube, a capacitive array sensor, leads and their interfaces; the capacitive array sensor has a special electrode arrangement, and its design and optimization process are guided by a conformal transformation method adopted by the present invention.

[0055] In this embodiment, the external structure serves as a support to increase the pressure resistance of the sensor. The present invention is considered a sensor module that can be connected to the pipeline system of the fluid to be measured as required. The two small flanges are used to connect the upstream and downstream pipelines; the two large flanges are connected to each other by at least two bolts and screws to ensure the stability of the overall structure of the sensor; the metal shell is connected to the ground potential through a wire to provide an electromagnetic shielding measurement environment for the internal capacitive array sensor. Among them, the upstream and downstream pipelines refer to the pipe section connecting the pipeline system of the fluid to be measured and the present invention.

[0056] The outer diameter of the polytetrafluoroethylene tube is 100 mm and the wall thickness is 10 mm. Solid glue is specifically poured into the gap between the metal shell and the polytetrafluoroethylene tube. The relative dielectric constant of the solid glue is 2.5. It is used to act as an auxiliary dielectric between the metal shell and the capacitive array sensor, and transfer the pressure on the polytetrafluoroethylene tube to the external structure.

[0057] The capacitive array sensor consists of four layers of annular electrode arrays, which are arranged axially along the outer wall of the polytetrafluoroethylene tube. Each layer of the electrode array contains six electrodes that are evenly spaced and closely arranged along the outer wall of the tube. Each electrode is connected by a lead wire, and the interface at the other end of the lead wire is embedded in the metal shell through an opening. The lead wire is a coaxial cable, and its shielding layer is connected to the metal shell. Its interface is a coaxial connector. The 24 electrodes are numbered as e1-e 24 The spacing between adjacent layers of annular electrode arrays is 5 mm. The total length of the area where the capacitive array sensors are arranged is 155 mm. The axial lengths of the four layers of annular electrode arrays from upstream to downstream are 49 mm, 21 mm, 21 mm, and 49 mm, respectively.

[0058] The lead is a coaxial cable that complies with the GB / T 11322.1-2013 standard. Its shielding layer is connected to the metal shell, and its interface is a coaxial connector that complies with the GB / T 11313.1-2013 standard.

[0059] The electrodes of different layers of the capacitance array sensor have specific axial lengths, and the length parameter selection method is guided by a conformal transformation concept adopted by the present invention. Figure 2As shown, the polytetrafluoroethylene tube is regarded as a tube of infinite length. The longitudinal section of the tube is represented in the complex plane (x, yi), i.e., the first complex plane, as a set of two straight lines z with a distance of 2r, where r is the outer diameter of the polytetrafluoroethylene tube. The real axis coordinates of the straight lines are r and -r respectively, the radius of the tube r is 50 mm, and the electrodes at different layers are regarded as line segments on the tube. After seven piecewise conformal transformations, the tube and the electrodes at different layers are mapped to a circle ω with a radius of 1 in the complex plane (u, vi), i.e., the second complex plane. The first complex plane (x, vi) and the second complex plane (u, vi) are mathematical concepts, specifically the concepts of complex variable functions. The piecewise conformal transformation is guided by the complex variable function group (1)-(7):

[0060]

[0061] Among them, z1, z2, z3, z4, z5, and z6 represent the intermediate variable curves in the piecewise conformal transformation process.

[0062] Including translation, rotation, straight line mapping to ray and straight line mapping to circle and other transformation processes, the overall mapping formula from z to ω is obtained by induction:

[0063]

[0064] Wherein, e is a natural constant, r is the radius of the polytetrafluoroethylene tube, i is an imaginary unit, z is the complex coordinate of the longitudinal section of the tube before conformal transformation, and ω is the complex coordinate of the longitudinal section of the tube after conformal transformation. 24 The meanings are different. The e in the formula is a natural constant, and the numbered e in the figures refers to the electrode number.

[0065] The conformal transformation formula (9) is still difficult to obtain an intuitive line-angle mapping relationship, so this embodiment simplifies it, as shown in the following example: Figure 3 As shown, from the geometric relationship represented by the complex function group (1)-(7), it can be deduced that the ray from point A in the complex plane (x, vi) to point B at infinity is mapped to an arc from point A' in the complex plane (u, vi) to point B' on the real axis. The geometric relationship is:

[0066]

[0067] Wherein, h is the modulus of the imaginary part of one endpoint of the electrode in the first complex plane, θ is the central angle of the arc determined by the endpoint of the electrode and the real axis of the coordinate in the second complex plane, and any endpoint of any electrode of the array sensor satisfies the above inverse transformation formula.

[0068] Due to the symmetry of the electrode distribution, the geometric relationship only represents the case where h>0 and 0≤θ≤90°.

[0069] In the embodiment, the total length of the area where the capacitive array sensor is arranged is 155 mm, the annular electrode arrays of adjacent layers are spaced apart from each other by 5 mm, and the annular electrode arrays of the same layer are spaced apart from each other by 5 mm. Figure 4 According to the geometric relationship (10), θ1 is about 10.015° and θ4 is about 4.495°, and at this time, an equation group is constructed by using the geometric relationship (11):

[0070]

[0071] wherein θ1, θ2 and θ4 are the central angles of the arcs corresponding to the infinite remote tube segment, the electrode and the electrode gap after the conformal transformation, respectively.

[0072] Solving gives θ2 is about 34.418°. By Figure 4 and the geometric relationship (11), the axial length of e1 electrode is about 49 mm and the axial length of e7 electrode is about 21 mm. The axial lengths of the remaining electrodes can be obtained by the symmetry relationship.

[0073] The above is only a preferred specific embodiment of the present application, but the protection scope of the present application is not limited to this. Any person skilled in the art can easily think of changes or replacements within the technical scope disclosed by the present application, which should be covered in the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. A three-dimensional capacitance array sensor that is resistant to high voltage and low temperature, characterized in that: Including: external structure, polytetrafluoroethylene tube, auxiliary dielectric, capacitance array sensor and signal lead; The external structure is fixedly connected to the capacitive array sensor, and the auxiliary dielectric and the signal lead are connected between the external structure and the capacitive array sensor; The polytetrafluoroethylene tube is located in the external structure and is fixedly connected to the external structure and the capacitive array sensor via the auxiliary dielectric; The capacitive array sensor includes N layers of annular electrode arrays, and each layer of the annular electrode array includes M electrodes; The annular electrode arrays of different layers are sequentially arranged axially along the outer wall of the polytetrafluoroethylene tube, and the M electrodes in the same layer are equally spaced along the circumferential direction of the outer wall of the polytetrafluoroethylene tube, forming a three-dimensional N-layer annular electrode array; The axial length of the electrodes in the three-dimensional N-layer annular electrode array is obtained based on a conformal transformation method; comprising: The longitudinal section of the polytetrafluoroethylene tube is regarded as a straight line group in a first complex plane, and the electrodes of different layers in the three-dimensional N-layer annular electrode array are regarded as line segments on the straight line group; The straight line group is mapped into a circle in a second complex plane, and the line segments are mapped into arcs on the circle, and the axial length of the electrode is obtained based on the arcs.

2. The high-voltage and low-temperature resistant three-dimensional capacitance array sensor according to claim 1, characterized in that: The external structure includes a large flange, a small flange, bolts, screw rods, nuts and a metal shell; The large flanges are located on both sides of the capacitive array sensor and are detachably connected via the bolts, screws and nuts; The small flanges are located on both sides of the large flange and are fixedly connected to the large flange; The metal shell is located on the outer surface of the capacitive array sensor, and the auxiliary dielectric is connected between the metal shell and the capacitive array sensor.

3. The high-voltage and low-temperature resistant three-dimensional capacitance array sensor according to claim 1, characterized in that: The signal lead is connected to a lead interface, one end of the signal lead is connected to the electrode, and the other end is connected to the metal shell through the lead interface, and the lead interface is embedded in the metal shell.

4. The high-voltage and low-temperature resistant three-dimensional capacitance array sensor according to claim 1, characterized in that: Mapping the straight line group in the first complex plane to a circle in the second complex plane by the conformal transformation; The mapping expression is: Where, e is a natural constant, r is the radius of the polytetrafluoroethylene tube, i is an imaginary unit, and z is the complex coordinate of the longitudinal section of the tube before conformal transformation. is the complex coordinate of the longitudinal section of the pipeline after conformal transformation.

5. The high-voltage and low-temperature resistant three-dimensional capacitance array sensor according to claim 1, characterized in that: The method for obtaining the axial length of the electrode based on the arc is as follows: making the arc mapped by the line segment in the second complex plane have a central angle and an arc length with a fixed proportional relationship, and then performing an inverse transformation on the arc to obtain the axial length of the electrode; The inverse transform is: Wherein, h is the imaginary modulus of one of the electrode endpoints in the first complex plane, θ is the central angle of the arc defined by the electrode endpoint and the real axis of the coordinate in the second complex plane, and r is the radius of the polytetrafluoroethylene tube.

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