Silk screen sensing device applicable to supercritical water condition and method for measuring void fraction

Abstract

The invention relates to a silk screen sensing device suitable for supercritical water conditions and a void fraction measuring method. The device comprises a pressure-resistant shell; the ceramic insulating sleeve is connected with the pressure-resistant shell through the wedge-shaped interface; the inner sleeve match A and the inner sleeve match B are connected through a wedge-shaped structure and locked through a hoop ring buckle; the silk screen sensor comprises an excitation end silk screen and a receiving end silk screen which are vertically arranged, and the excitation end silk screen and the receiving end silk screen pass through sensor contacts and then are embedded in the insulating disc; the excitation source and the signal collector are integrated in the pressure-resistant shell, and the wire slot of the inner sleeve matching B penetrates through the insulating sealing element of the inner sleeve matching A and then is connected to the silk screen sensor; the pressure-resistant shell is welded in a main pipeline loop, and the silk screen sensor is arranged perpendicular to the working medium flowing direction. Compared with the prior art, the system has the advantages of high measurement precision, extreme environment resistance, interference resistance and the like.

Description

Technical Field

[0001] The present invention relates to the technical fields of fluid mechanics, thermal hydraulics and measurement technology, and particularly relates to a wire mesh sensing device applicable to supercritical water conditions and a method for measuring void fraction. Background Art

[0002] Due to its special physical and chemical properties, supercritical water is widely used in the fields of nuclear energy, chemical engineering, supercritical extraction, etc. In these application environments, the bubble behavior in the flow has an important impact on the thermodynamic stability, heat transfer characteristics and equipment safety of the system. Therefore, accurately measuring the bubble behavior in a supercritical water environment is crucial for optimizing system design and improving operation efficiency.

[0003] Existing methods for measuring bubbles, such as optical imaging, conductivity sensors and ultrasonic sensors, have problems such as low measurement accuracy and poor tolerance in a high-temperature and high-pressure supercritical water environment. Wire mesh sensors have been widely used in bubble measurement in a low-temperature and low-pressure environment due to their simple structure and fast real-time response. However, in a supercritical water environment, the application of wire mesh sensors still faces technical challenges, such as the high-temperature resistance of sensor materials, the accuracy of signal acquisition, and the stability in a high-pressure environment.

[0004] CN202311649914.6 discloses a wire mesh sensor applicable to a high-temperature and high-pressure environment. In a high-temperature and high-pressure geometric flow channel, emitter and receiver electrodes arranged vertically and staggered are installed perpendicular to the flow direction. The emitter and receiver electrodes are made of enameled wires to ensure insulation between the emitter and receiver electrodes. At the same time, one end of the emitter and receiver electrodes is connected to a rigid terminal, and the other end is connected to a rigid signal connection wire. The rigid terminal is embedded in the insulating ceramic on the inner side of the flow channel. The rigid signal connection wire passes through the insulating ceramic layer on the inner side of the flow channel and then passes out of the outer wall surface of the flow channel to connect to an excitation source or a signal collector, and the rigid signal connection wire is sealed with the outer wall surface of the flow channel. Thus, the phase distribution imaging measurement of gas-liquid two-phase flow in a high-temperature and high-pressure environment is realized. However, the material durability is insufficient, and there are signal interference and measurement errors. Summary of the Invention

[0005] The purpose of the present invention is to overcome the above-mentioned defects existing in the prior art and provide a wire mesh sensing device applicable to supercritical water conditions and a method for measuring void fraction, with high measurement accuracy, resistance to extreme environments and anti-interference ability.

[0006] The present invention provides a wire mesh sensing device applicable to supercritical water conditions, including:

[0007] A pressure-resistant outer shell with a working pressure range of 23 MPa to 30 MPa and a working temperature range of 360 °C to 500 °C;

[0008] The ceramic insulating sleeve is made of ceramic insulating material and is connected to the pressure-resistant shell through a wedge-shaped interface; the ceramic insulating sleeve is connected to the pressure-resistant shell through screws and the wedge-shaped interface;

[0009] Inner sleeve fitting A and inner sleeve fitting B are connected through a wedge-shaped structure and locked by a clamp ring; to ensure the pressure resistance performance of the inner sleeve under high pressure;

[0010] The wire mesh sensor includes an excitation end wire mesh and a receiving end wire mesh arranged vertically. The excitation end wire mesh and the receiving end wire mesh are embedded inside the insulating disc after passing through the sensor contacts;

[0011] A grid-shaped sensitive area is formed through orthogonal projection, significantly improving the spatial resolution and measurement accuracy. The orthogonal wire meshes form dense intersection points on the fluid cross-section, and each intersection point corresponds to the real-time measurement of the local void fraction.

[0012] The vertical cross structure enables the projection overlap of the excitation end and the receiving end wire meshes to form dense two-dimensional capacitance detection units (spacing 1 mm). When bubbles flow through, it can cover a wider transverse and longitudinal flow cross-section, reduce the measurement blind area, and accurately capture the three-dimensional distribution characteristics of bubbles through the synchronous change of capacitance signals at multiple points. The vertical layout synchronously captures the bubble distribution in the transverse (flow direction) and longitudinal (pressure gradient direction) of the fluid. Combining with the time series analysis of the capacitance signals, the three-dimensional dynamic evolution process of the voids can be reconstructed. At the same time, the orthogonal projection forms a natural spatial filtering effect, effectively suppressing the signal crosstalk caused by the high-speed flow of supercritical water, reducing the parasitic capacitance coupling between adjacent wire meshes, and ensuring the signal-to-noise ratio of the capacitance signals; in addition, the vertical structure, combined with the high-temperature rigidity of the molybdenum wire and the limit packaging of the insulating disc, can offset the stress through deformation in the symmetric direction during thermal expansion, avoiding the instability of the wire mesh spacing due to temperature fluctuations, thus ensuring the repeatability of long-term measurements.

[0013] The excitation source and the signal collector are integrated inside the pressure-resistant shell. The wire groove of inner sleeve fitting B passes through the insulating seal of inner sleeve fitting A and is then connected to the wire mesh sensor;

[0014] The wire mesh sensor, inner sleeve fitting A, inner sleeve fitting B, ceramic insulating sleeve, and pressure-resistant shell are axially connected in sequence; the pressure-resistant shell is welded to the main pipeline loop, and the wire mesh sensor is arranged perpendicular to the working fluid flow direction. The two pressure-resistant shells are connected by stud nuts and welded to the main pipeline.

[0015] Further, the distance between the excitation end wire mesh and the receiving end wire mesh is 1 mm.

[0016] Further, the materials of the excitation end wire mesh and the receiving end wire mesh are molybdenum metal, the single wire diameter is not more than 0.1 mm, and the surface is coated with an antioxidant insulating layer.

[0017] Furthermore, a conical surface positioning structure is provided at the wedge-shaped connection between the inner sleeve fitting A and the inner sleeve fitting B.

[0018] Furthermore, the exciting end wire mesh and the receiving end wire mesh leads of the wire mesh sensor pass through the wire groove of the inner sleeve fitting B and are connected to the excitation source and the signal collector through copper conductive nodes.

[0019] Furthermore, the excitation source is a micro high-frequency module encapsulated in a PCB, with a size of 20mm × 20mm × 5mm, a power of 6mW, powered by a high-temperature lithium battery (Li-SOCl2), and wrapped with a 10mm heat insulation layer on the outside.

[0020] Furthermore, the signal collector uses an embedded data acquisition module, which includes a low-power STM32 microcontroller and a high-precision ADC, with a size of 30mm × 30mm × 10mm, and is powered by a high-temperature lithium battery (Li-SOCl2).

[0021] Furthermore, a sealing gasket is provided at the interface between the ceramic insulating sleeve and the pressure-resistant outer shell to prevent supercritical water from seeping in.

[0022] The present invention also provides a method for measuring the void fraction of a wire mesh sensing device applicable to supercritical water conditions, including the following steps:

[0023] S1: In supercritical water fluid (pressure ≥ 22MPa, temperature ≥ 374°C), each exciting end wire mesh is excited separately in sequence; during measurement, the main pipeline is connected to an electric heating device, and the fluid working medium flow is pressurized and heated by electric heating to obtain supercritical water fluid. The pressure of this supercritical water fluid is not less than 22MPa, and the corresponding temperature is not less than 374°C.

[0024] S2: The conductivity signal of the receiving end wire mesh is recorded in real time by the signal collector; the conductivity signal is temporarily stored in an embedded memory card, and the void distribution is analyzed offline after the measurement ends;

[0025] S3: Calculate the local void fraction according to the conductivity change and statistically calculate the cross-sectional average void fraction. The magnitude of the current received by the receiving end wire mesh characterizes the instantaneous void fraction size at the intersection of the emitter and the receiver. Measure the local void fraction at each intersection of the emitter and the receiver, and calculate the average cross-sectional void fraction therefrom, thereby obtaining the void fraction distribution inside the supercritical fluid.

[0026] Furthermore, the excitation source outputs a high-frequency alternating voltage; the signal collector records the current signals at all intersections of the exciting end and the receiving end in units of frames. For all exciting end wire meshes and receiving end wire meshes, each time the exciting end wire mesh is sequentially excited and the signal is received by the signal collector, the measurement of one frame is completed.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) High-precision measurement: The vertical wire mesh array with a spacing of 1 mm can identify millimeter-level bubbles, improving the spatial resolution of the void fraction.

[0029] (2) Resistance to extreme environments: The thermal expansion coefficients of molybdenum wire (4.8×10 -6 / °C) and zirconia insulating disc (10.5×10 -6 / °C) match. The similar thermal expansion coefficients of ceramics and molybdenum are used to avoid thermal stress cracking. The structural stress is reduced under a 500°C thermal shock, preventing the wire mesh from deforming due to thermal mismatch; Composite protection system: The Al2O3 / Si3N4 gradient coating reduces the oxidation rate of the wire mesh in supercritical water, resisting chemical corrosion and electrochemical oxidation of supercritical water; Multi-layer sealing structure: The wedge-shaped interface and the conical surface positioning have a small assembly error. Combined with the rapid heat conduction of the copper wire groove (thermal conductivity 401 W / m·K), the temperature of the internal module is always kept at a low level. A physical sealing barrier is formed through a high-temperature sintering process to block the penetration of supercritical water. When measuring, the excitation / receiving wire mesh forms a micro-capacitance structure. When a bubble passes through, the change in dielectric constant causes a capacitance signal fluctuation. The small diameter of the molybdenum wire (≤0.1 mm) improves the spatial resolution, and combined with the electrical insulation characteristics of the coating, the signal is ensured to be stable. Finally, the on-line quantitative monitoring of the void fraction in supercritical water is realized. The molybdenum wire mesh and insulating disc ensure the long-term stable operation of the sensor in the supercritical water environment. Achieve the sealing of the wire mesh sensing device under supercritical conditions and obtain the measurement of the void fraction quantity in supercritical water.

[0030] (3) Anti-interference: The embedded insulation fixation effectively isolates the interference of external conductive media, ensuring the accuracy of signal acquisition; The excitation source outputs a high-frequency alternating voltage, reducing the electrode polarization effect compared with the DC scheme. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is an exploded view of a wire mesh sensing device suitable for supercritical water conditions;

[0032] Figure 2 is an installation sectional view of a wire mesh sensing device suitable for supercritical water conditions;

[0033] Figure 3 is a signal transmission schematic diagram of a wire mesh sensing device suitable for supercritical water conditions;

[0034] Figure 4 is a sectional view of a wire mesh sensing device suitable for supercritical water conditions.

[0035] Reference numerals: 1 - pressure-resistant outer shell; 2 - ceramic insulating sleeve; 3 - inner sleeve fitting A; 4 - inner sleeve fitting B; 5 - wire mesh sensor; 6 - wire groove. Detailed Embodiments

[0036] The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments. Features such as component models, material names, connection structures, control methods, algorithms, etc. that are not clearly described in this technical solution are regarded as common technical features disclosed in the prior art.

[0037] Embodiment 1

[0038] This embodiment provides a wire mesh sensing device applicable to supercritical water conditions, as Figures 1-4 shown, including:

[0039] A pressure-resistant outer shell 1 with a working pressure range of 23 MPa to 30 MPa and a working temperature range of 360 °C to 500 °C;

[0040] A ceramic insulating sleeve 2 made of ceramic insulating material and connected to the pressure-resistant outer shell 1 through a wedge-shaped interface; the ceramic insulating sleeve 2 is connected to the pressure-resistant outer shell 1 through screws to the wedge-shaped interface;

[0041] Inner sleeve fitting A3 and inner sleeve fitting B4, which are connected through a wedge-shaped structure and locked by a clamp ring; ensuring the pressure resistance performance of the inner sleeve under high pressure; a conical surface positioning structure is provided at the wedge-shaped connection of the inner sleeve fitting A3 and the inner sleeve fitting B4.

[0042] A wire mesh sensor 5, including a vertically arranged excitation end wire mesh and a receiving end wire mesh, the excitation end wire mesh and the receiving end wire mesh are embedded inside the insulating disc after passing through the sensor contact; the distance between the excitation end wire mesh and the receiving end wire mesh is 1 mm. The materials of the excitation end wire mesh and the receiving end wire mesh are molybdenum metal, the single wire diameter is not more than 0.1 mm, and the surface is coated with an antioxidant insulating layer.

[0043] An excitation source and a signal collector are integrated inside the pressure-resistant outer shell 1. The wire groove 6 of the inner sleeve fitting B4 passes through the insulating seal of the inner sleeve fitting A3 and is connected to the wire mesh sensor 5; the wires of the excitation end wire mesh and the receiving end wire mesh of the wire mesh sensor 5 pass through the wire groove 6 of the inner sleeve fitting B4 and are connected to the excitation source and the signal collector through copper conductive nodes. The wire groove 6 is a copper wire groove.

[0044] The wire mesh sensor 5, the inner sleeve fitting A3, the inner sleeve fitting B4, the ceramic insulating sleeve 2, and the pressure-resistant outer shell 1 are axially connected in sequence; the pressure-resistant outer shell 1 is welded to the main pipeline loop, and the wire mesh sensor 5 is arranged perpendicular to the working medium flow direction. The two pressure-resistant outer shells 1 are connected by stud nuts and welded to the main pipeline.

[0045] The excitation source is a micro high-frequency module in a PCB package, with dimensions of 20 mm × 20 mm × 5 mm and a power of 6 mW, powered by a high-temperature lithium battery (Li-SOCl2).

[0046] The signal collector adopts an embedded data acquisition module, which includes a low-power STM32 microcontroller and a high-precision ADC, with a size of 30mm×30mm×10mm and is powered by a high-temperature lithium battery (Li-SOCl2). Both the excitation source module and the signal acquisition module are wrapped with a 10mm heat insulation layer and fixed inside the pressure-resistant shell 1.

[0047] A sealing gasket is provided at the interface between the ceramic insulating sleeve 2 and the pressure-resistant shell 1 to prevent supercritical water from seeping in.

[0048] This embodiment also provides a method for measuring the void fraction of a wire mesh sensing device applicable to supercritical water conditions, including the following steps:

[0049] S1: In supercritical water fluid (pressure ≥ 22MPa, temperature ≥ 374°C), each excitation end wire mesh is excited separately in sequence; during measurement, the main pipeline is connected to an electric heating device, and the fluid working medium flow is pressurized and heated by electric heating to obtain supercritical water fluid. The pressure of this supercritical water fluid is not lower than 22MPa, and the corresponding temperature is not lower than 374°C.

[0050] S2: The signal collector records the conductivity signal of the receiving end wire mesh in real time; the conductivity signal is temporarily stored in an embedded memory card, and the void distribution is analyzed offline after the measurement ends; the excitation source outputs a high-frequency alternating voltage; the signal collector records the current signals at all intersections of the excitation end and the receiving end in units of frames. For all excitation end wire meshes and receiving end wire meshes, each time an excitation end wire mesh is sequentially excited and after the signal is received by the signal collector, a frame of measurement is completed.

[0051] S3: Calculate the local void fraction according to the change in conductivity and statistically analyze the cross-sectional average void fraction. The magnitude of the current received by the receiving end wire mesh characterizes the instantaneous void fraction at the intersection of the emitter and the receiver. Measure the local void fraction at each intersection of the emitter and the receiver, and thereby calculate the average cross-sectional void fraction, and further obtain the void fraction distribution inside the supercritical fluid.

[0052] In the range of 22MPa - 26MPa and a heat flux density change of 0.2MW / m2 - 1.4MW / m2, the void fraction at a specific position is measured using this wire mesh sensor. Some measurement results are shown in the following table:

[0053]

[0054] It can be seen from the measurement results that this measurement method improves the spatial resolution of the void fraction, realizes high-precision measurement; and is resistant to extreme environments and has anti-interference ability.

[0055] The components not elaborated in this embodiment are all existing components that can be purchased through public channels.

[0056] The above description of the embodiments is to enable those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative effort. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention should be within the protection scope of the present invention.

Claims

1. A wire mesh sensing device applicable to supercritical water conditions, characterized in that, Comprising: A pressure-resistant housing (1) with an operating pressure range of 23 MPa to 30 MPa and an operating temperature range of 360 °C to 500 °C; A ceramic insulating sleeve (2) connected to the pressure-resistant housing (1) through a wedge-shaped interface; Inner sleeve fitting A (3) and inner sleeve fitting B (4), which are connected through a wedge-shaped structure and locked by a clamp ring; A wire mesh sensor (5) comprising an excitation end wire mesh and a receiving end wire mesh arranged vertically. The excitation end wire mesh and the receiving end wire mesh are embedded inside the insulating disc after passing through the sensor contacts; An excitation source and a signal collector, integrated inside the pressure-resistant housing (1). The wire groove (6) of the inner sleeve fitting B (4) passes through the inner sleeve fitting A (3) and is connected to the wire mesh sensor (5); The wire mesh sensor (5), inner sleeve fitting A (3), inner sleeve fitting B (4), ceramic insulating sleeve (2) and pressure-resistant housing (1) are axially connected in sequence. The pressure-resistant housing (1) is welded in the main pipeline loop, and the wire mesh sensor (5) is arranged perpendicular to the working fluid flow direction.

2. The wire mesh sensing device applicable to supercritical water conditions according to claim 1, characterized in that The distance between the excitation end wire mesh and the receiving end wire mesh is 1 mm.

3. The wire mesh sensing device applicable to supercritical water conditions according to claim 1, characterized in that The materials of the excitation end wire mesh and the receiving end wire mesh are molybdenum metal, the single wire diameter is not greater than 0.1 mm, and the surface is coated with an antioxidant insulating layer.

4. The wire mesh sensing device applicable to supercritical water conditions according to claim 1, characterized in that, A conical surface positioning structure is provided at the wedge-shaped connection of the inner sleeve fitting A (3) and the inner sleeve fitting B (4).

5. A wire mesh sensing device applicable to supercritical water conditions according to claim 1, characterized in that, The wires of the excitation end wire mesh and the receiving end wire mesh of the wire mesh sensor (5) pass through the wire groove (6) of the inner sleeve fitting B (4) and are connected to the excitation source and the signal collector through copper conductive nodes.

6. The wire mesh sensing device applicable to supercritical water conditions according to claim 1, characterized in that, The excitation source is a micro high-frequency module encapsulated by PCB, powered by a high-temperature lithium battery, and externally wrapped with a heat insulation layer.

7. A wire mesh sensing device applicable to supercritical water conditions according to claim 1, characterized in that, The signal collector adopts an embedded data acquisition module, which includes an STM32 microcontroller and an ADC.

8. A wire mesh sensing device applicable to supercritical water conditions according to claim 1, characterized in that, A sealing gasket is provided at the interface between the ceramic insulating sleeve (2) and the pressure-resistant housing (1) to prevent supercritical water from seeping in.

9. A method for measuring void fraction of the device according to any one of claims 1-8, characterized in that, Including the following steps: S1: In the supercritical water fluid, each excitation end wire mesh is separately excited in sequence. During measurement, the main pipeline is connected to an electric heating device, and the fluid working medium flow is pressurized and heated by electric heating to obtain supercritical water fluid. The pressure of this supercritical water fluid is not less than 22 MPa, and the corresponding temperature is not less than 374 °C; S2: The conductivity signal of the receiving end wire mesh is recorded in real time by the signal collector. The conductivity signal is temporarily stored by an embedded memory card, and the void fraction distribution is analyzed offline after the measurement ends; S3: Calculate the local void fraction according to the conductivity change and statistically calculate the cross-section average void fraction.

10. A method for measuring void fraction according to claim 9, characterized in that, The excitation source outputs a high-frequency alternating voltage; the signal collector records the current signals of all intersections of the excitation end and the receiving end in frames.

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