A system and method for measuring the concentration at the gas-liquid two-phase flow interface in a channel.

Abstract

This invention discloses a system for measuring the concentration at the gas-liquid two-phase flow interface within a channel. A spiral cross-shaped fuel rod bundle is fixed within a rod bundle experimental section. A gas-water mixer is connected to the bottom of the rod bundle experimental section, receiving and mixing gas and water to form a gas-liquid two-phase flow, which is then introduced into the rod bundle experimental section. Wire mesh probe sensors are horizontally positioned within the rod bundle experimental section. Each wire mesh probe sensor includes two layers of wire mesh probes, each layer comprising an emitter, a receiver, and a measuring point. A circuit acquisition module is connected to the wire mesh probe sensors. The circuit acquisition module provides an excitation voltage to the wire mesh probes and outputs different electrical signal values ​​after passing through a loop to identify different phase states in the rod bundle experimental section. By outputting different electrical signal values ​​to identify different phase states, and based on the wire mesh probe spacing, the phase content of the gas-liquid two-phase flow field can be calculated, enabling more effective acquisition of refined basic experimental data, including phase distribution.

Description

Technical Field

[0001] This invention belongs to the field of multiphase flow parameter measurement and nuclear reactor thermal hydraulics, and particularly relates to a system and method for measuring the concentration of gas-liquid two-phase flow interface in a channel. Background Technology

[0002] Under accident conditions, the gas-liquid flow within the rod bundle channels of boiling water reactors or pressurized water reactors exhibits multidimensional transient flow characteristics. As a novel type of reactor fuel assembly, the helical cross fuel offers numerous advantages, including short thermal conductivity, strong mixing ability, and no need for positioning supports. It can effectively increase core power while ensuring reactor safety margins. Compared to simple pipes, the dynamic behaviors of bubble coalescence, breakup, and migration within the helical cross rod bundle channels are more complex. From the perspective of reactor thermal-hydraulics, a comprehensive understanding of the spatiotemporal distribution of each phase within the rod bundle channels directly relates to the structural design and heat dissipation performance of the rod bundle, and consequently, the reactor's economy and reliability. Furthermore, the verification of multidimensional gas-liquid flow analysis codes (such as sub-channel analysis), the establishment of computational fluid dynamics (CFD) models, and the development of rod bundle gas-liquid flow theory all rely on a database of gas-liquid two-phase flows within the rod bundle channels.

[0003] To study the dynamics of gas-liquid two-phase flow in the helical cross fuel rod bundle region of pressurized water reactors, high-speed cameras and radiation techniques are commonly used. However, while high-speed cameras can identify the flow regime within the bundle, they cannot accurately obtain the void fraction and phase interface concentration of the two-phase flow. Due to the influence of the wall and limitations in temporal resolution, radiation techniques cannot accurately capture the rapid fluctuations in porosity during dynamic gas-liquid flow. Furthermore, the design and construction of such measurement techniques are extremely complex and expensive. The limitations of existing measurement techniques result in a lack of refined experimental data on gas-liquid two-phase flow within the helical cross fuel rod bundle region, and the evolution of phase content during accidents remains unclear, leading to a relative scarcity of relevant experimental mechanisms and physical models.

[0004] Therefore, there is a need to develop measurement techniques with high spatiotemporal resolution that can be applied to the spiral cross fuel rod bundle channel to analyze the gas-liquid two-phase flow field and phase interface concentration in this structure, so as to obtain basic experimental data and provide a guarantee for the development of mechanism research. Summary of the Invention

[0005] The technical objective of this invention is to provide a system and method for measuring the concentration of the gas-liquid two-phase flow interface in a channel, in order to solve the problem of the lack of basic experimental data on gas-liquid two-phase flow in a spiral cross fuel rod bundle channel.

[0006] To solve the above problems, the technical solution of the present invention is as follows:

[0007] A system for measuring the concentration at the gas-liquid two-phase interface in a channel, comprising:

[0008] Experimental setup and circuit acquisition module;

[0009] The experimental setup includes a rod bundle experimental section, a gas-water mixer, and several wire mesh probe sensors. A helical cross-shaped fuel rod bundle is fixed within the rod bundle experimental section. The gas-water mixer is connected to the bottom of the rod bundle experimental section and is configured to receive gas and water respectively, mix them to form a gas-liquid two-phase flow, and then introduce it into the rod bundle experimental section. Several wire mesh probe sensors are horizontally arranged within the rod bundle experimental section. Each wire mesh probe sensor includes two layers of wire mesh probes, and each layer of wire mesh probes includes an emitter, a receiver, and a measuring point.

[0010] The circuit acquisition module is connected to the wire mesh probe sensor signal. The wire mesh probe, the different phase fluid media in the rod bundle experimental section and the circuit acquisition module form a loop, and the different phase fluid media are connected in parallel. The circuit acquisition module is configured to provide excitation voltage to the wire mesh probe, and output different electrical signal values ​​after passing through the loop to identify different phase states in the rod bundle experimental section.

[0011] Among them, the spiral cross fuel rod bundles in the rod bundle test section are set with equal diameter and pitch. The cross section of the rod bundle test section is a square structure of 66.1mm×66.1mm. The hydraulic diameter of the rod bundle test section is 10.28mm. The diameter of the spiral cross fuel rod bundle is 9.5mm. The spacing between adjacent spiral cross fuel rod bundles is 12.6mm. The hydraulic diameter of the flow field region directly enclosed by adjacent spiral cross fuel rod bundles is 8.321mm.

[0012] Specifically, each layer of wire mesh probes includes a mesh structure with 32*32 intersections and a total of 1024 test points. The nodes on the connected ends of the wire mesh structure are the transmitter and receiver, respectively. Each test point, transmitter, and receiver is equipped with a 0.1mm diameter stainless steel electrode wire, which is soldered onto a 2mm thick PCB circuit board. The spacing between adjacent electrode wires is 2mm, and the axial distance between adjacent wire mesh probes is 2mm.

[0013] More preferably, 32 identical insulating connectors are embedded between the transmitter and receiver, and the electrode wires in contact with the cross-section of the insulating connectors are covered with insulating adhesive.

[0014] The gas-water mixer is 1500mm high, and a mixing channel with an inner diameter of about 1.2mm and a length of 1000mm is provided at the connection between the gas-water mixer and the rod bundle experimental section.

[0015] A method for measuring the concentration at the gas-liquid two-phase flow interface in a channel, configured in the aforementioned system for measuring the concentration at the gas-liquid two-phase flow interface in a channel, includes the following steps:

[0016] Water is supplied to the gas-water mixer through the liquid phase inlet, and gas is injected into the gas-water mixer through the gas phase inlet. The gas and liquid phases are fully mixed in the gas-water mixer.

[0017] The mixed gas-liquid two-phase flow enters the rod bundle experimental section;

[0018] When the gas-liquid two-phase flow passes through the wire mesh probe sensor, different electrical signals are generated due to the different electrical conductivities of the gas and liquid phases. The generated signals are received by the circuit acquisition module, and after data processing, the relevant parameters of the gas-liquid two-phase flow field and phase interface concentration in the rod bundle experimental section are obtained.

[0019] Specifically, the calculation of the phase interface satisfies the following formula:

[0020]

[0021] Among them, R i,j,k Let k be the normalized signal collected at time k. The local fluid conductivity is measured by the wire mesh probe sensor. Let a be the conductivity of the single-phase fluid in the rod bundle experimental section. i,j,k Let be the cavitation fraction at time k.

[0022] Specifically, the calculation of the local cavitation fraction satisfies the following formula:

[0023]

[0024] Among them, A i,j,in and A i,j,total These represent the flow channel area and total cross-sectional area of ​​the rod bundle experimental section, respectively, α area The area-average gas content, This represents the time-averaged cavitation fraction.

[0025] Specifically, the gas phase volume within the two layers of wire mesh probes measured satisfies the following functional relationship:

[0026]

[0027] The concentration of the phase interface within the two layers of wire mesh probes is calculated according to the following formula:

[0028]

[0029] Where, j g For apparent air velocity, j f For apparent liquid velocity, A duct t is the cross-sectional area of ​​the flow channel.meas The measurement time.

[0030] Because the present invention adopts the above technical solution, it has the following advantages and positive effects compared with the prior art:

[0031] This invention measures the phase content change of the cross-sectional area of ​​an experimental section, converts the acquired electrical signals into conductivity signals, and calculates the phase interface concentration within the rod bundle region using a processing system. Wire mesh probes are deployed across the entire flow channel cross-section except for the rod bundle, and a circuit acquisition module connected to the wire mesh probes provides the excitation voltage. When different fluid media flow through the wire mesh probes, the circuit acquisition module outputs different electrical signal values ​​to identify different phase states, and the phase content of the gas-liquid two-phase flow field can be calculated based on the spacing between the wire mesh probes. Compared to existing technologies, this invention can more effectively acquire refined fundamental experimental data, including phase distribution, laying the foundation for related theoretical research. Attached Figure Description

[0032] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention.

[0033] Figure 1 This is a schematic diagram of the structure of a gas-liquid two-phase flow phase interface concentration measurement system in a channel according to the present invention;

[0034] Figure 2 This is a schematic diagram of the actual wire mesh probe sensor of the present invention;

[0035] Figure 3 This is a schematic diagram of the spiral cross fuel rod bundle of the present invention;

[0036] Figure 4 This is a schematic diagram of the test cross-section of the wire mesh probe sensor of the present invention;

[0037] Figure 5 This is a circuit diagram of the circuit acquisition module of the present invention.

[0038] Explanation of reference numerals in the attached figures

[0039] 1: Gas phase inlet; 2: Liquid phase inlet; 3: Gas-water mixer; 4: Positioning shelf; 5: Wire mesh probe sensor; 6: Wire; 7: Probe circuit power supply; 8: Transmitter; 9: Receiver; 10: Signal acquisition circuit; 11: Bus. Detailed Implementation

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the specific implementation methods of the present invention will be described below with reference to the accompanying drawings. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings and other implementation methods can be obtained based on these drawings without any creative effort.

[0041] To keep the drawings concise, only the parts relevant to the invention are shown schematically in each figure, and they do not represent the actual structure of the product. Furthermore, for ease of understanding, in some figures, only one of components with the same structure or function is shown schematically, or only one is labeled. In this document, "one" can mean not only "only one" but also "more than one".

[0042] The following detailed description, in conjunction with the accompanying drawings and specific embodiments, provides a system and method for measuring the concentration at the gas-liquid two-phase flow interface within a channel, as proposed in this invention. The advantages and features of this invention will become more apparent from the following description and claims.

[0043] See the example. Figures 1 to 5 This embodiment provides a system for measuring the concentration at the gas-liquid two-phase interface in a channel, which mainly includes an experimental setup and a circuit acquisition module. Based on electrical principles, the system measures the phase state. Under normal experimental conditions, a wire mesh probe sensor is arranged within the flow channel of the experimental section. The multiphase flow field consists of water and gas phase components. The circuit acquisition module provides an excitation voltage to the wire mesh probe system, and current is introduced into the multiphase flow field from the wire mesh probe sensor. Based on the different conductivities of the gas and liquid phases, the gas-liquid two-phase identification is achieved. The equivalent circuit diagram is shown below. Figure 5 As shown, when the wire mesh probe sensor comes into contact with the gas phase component, the gas phase component is equivalent to the equivalent resistance in the equivalent circuit; similarly, when the wire mesh probe comes into contact with the aqueous phase component, the aqueous phase component is equivalent to the equivalent resistance in the acquisition circuit. Based on the different electrical conductivities of the two-phase fluids, different electrical signal values ​​are output, thereby distinguishing the spatial distribution of the two-phase fluids. According to the cross-correlation analysis of the electrical signals between adjacent wire mesh probe sensors, the evolution rate of the phase interface and the change in phase content can be determined. Therefore, based on the wire mesh probe sensor, the coordinated measurement of the gas-liquid two-phase flow field and the phase interface concentration in the spiral cross fuel rod bundle channel can be realized.

[0044] Specifically, see Figure 1In this embodiment, the experimental setup includes a rod bundle experimental section, a gas-water mixer, and several wire mesh probe sensors. A positioning shelf is provided within the rod bundle experimental section to secure the helical cross-shaped fuel rod bundle. The gas-water mixer is connected to the bottom of the rod bundle experimental section, which receives and mixes gas and water to form a gas-liquid two-phase flow, which is then introduced into the rod bundle experimental section. Several wire mesh probe sensors are horizontally arranged within the rod bundle experimental section, i.e., on its cross-section. Each wire mesh probe sensor includes two layers of wire mesh probes, each layer comprising an emitter, a receiver, and a measuring point.

[0045] Specifically, the gas-water mixer has a gas phase inlet at its bottom, which is connected to the air compressor pipeline via a rubber hose. Furthermore, the gas-water mixer has a liquid phase inlet on its side, also connected to a water pump pipeline via a rubber hose. To ensure proper mixing of the gas and liquid phases, the gas-water mixer is 1500 mm high, and a mixing channel with an inner diameter of approximately 1.2 mm and a length of 1000 mm is provided at the connection between the gas-water mixer and the rod bundle experimental section, allowing for the full development of the gas-liquid two-phase flow.

[0046] Next, the spiral cross fuel rod bundles in the rod bundle experimental section are arranged with equal diameter and pitch. The cross-section of the rod bundle experimental section is the rod bundle channel, which is a square structure of 66.1mm × 66.1mm. The hydraulic diameter of the rod bundle channel (the hydraulic diameter is the ratio of four times the cross-sectional area of ​​the flow channel to the circumference of the fuel rods, and the cross-sectional area of ​​the flow channel is the cross-sectional area of ​​the rod bundle channel excluding the rod bundles) is 10.28mm. The diameter of the spiral cross fuel rod bundle is 9.5mm, the spacing between adjacent spiral cross fuel rod bundles is 12.6mm, and the hydraulic diameter of the sub-channel (the flow field region directly enclosed by adjacent spiral cross fuel rod bundles) is 8.321mm. A wire mesh probe sensor is installed 2250mm from the bottom of the rod bundle channel. The wire mesh probe sensor can collect two-phase flow data of the central sub-channel (the central region of the sub-channel), the edge sub-channel (the edge region of the sub-channel), the corner sub-channel (the corner region of the sub-channel), and the sidewall sub-channel (the sub-channel near the wall).

[0047] See Figure 1 , Figure 4 and Figure 5 The wire mesh probe sensor is arranged at the cross-section as follows: Figure 4As shown in the figure, the cross structure represents the cross-section of a spiral cross fuel rod bundle, along with a mesh-like wire mesh structure. This wire mesh structure has 32*32 intersection points, providing 1024 test points. These test points are evenly distributed across the cross-section of the fuel rod bundle channel. The signal transmitter is located on one side of the wire mesh structure, and the side perpendicularly adjacent to the transmitter is the signal receiver. Each test point, transmitter, and receiver is equipped with a 0.1mm diameter stainless steel electrode wire, soldered to a 2mm thick PCB circuit board (the circuit board supports the electrode wires at the transmitter and receiver). The spacing between adjacent electrode wires is 2mm, and the axial distance between adjacent wire mesh probes is 2mm. The data acquisition frequency for the test points is 5000Hz, with each record lasting 20 seconds. During the measurement, the electrodes at the transmitter end are continuously activated while all other transmitter electrodes remain at ground potential. Furthermore, 32 identical insulated connectors are embedded between the electrode wires at the transmitter and receiver ends, and the electrode wires in contact with the insulated connectors are then covered with insulating adhesive. This design ensures that only the intersections in the spiral cross fuel rod bundle channels come into contact with the fluid, while the intersections covered by the rod bundle cross section do not come into contact with the fluid.

[0048] Next, see Figure 5 The circuit acquisition module and the wire mesh probe sensor are connected via probe leads mounted on the side wall of the experimental section. A circuit is formed by the wire mesh probe, different phase fluid media within the rod bundle experimental section, and the circuit acquisition module, with the different phase fluid media connected in parallel. The circuit acquisition module includes an excitation circuit and a signal acquisition circuit. The excitation circuit provides an excitation voltage to the wire mesh probe, outputting different electrical signal values ​​after passing through the circuit. These values ​​are then acquired by the signal acquisition circuit to identify the different phase states within the rod bundle experimental section.

[0049] Further preferably, this embodiment also provides a method for measuring the concentration of the gas-liquid two-phase flow interface within a channel. The method, configured in the aforementioned gas-liquid two-phase flow interface concentration measurement system, includes the following steps: A water pump supplies water to the gas-water mixer through the liquid phase inlet, while an air compressor injects gas into the gas-water mixer through the gas phase inlet. The gas and liquid phases are thoroughly mixed in the gas-water mixer. The mixed gas-liquid two-phase flow enters the rod bundle experimental section. When the gas-liquid two-phase flow passes through the wire mesh probe sensor, different electrical signals are generated due to the different conductivities of the gas and liquid phases. The generated signals are received by the signal acquisition circuit and aggregated via a bus to the host computer for data processing, obtaining relevant parameters such as the gas-liquid two-phase flow field and interface concentration within the rod bundle experimental section. After passing through the experimental section, the gas and liquid phases flow out from the top of the rod bundle channel, undergo two-phase separation by a gas-water separator, with the separated gas phase discharged into the atmosphere and the separated liquid phase entering a water tank.

[0050] Preferably, the signal acquisition circuit filters out noise signals by setting a very low threshold, identifies the core region of the bubble, and assigns the peripheral elements of the bubble to the identified bubble using an automatic cellular calculation method, thus completing the bubble identification.

[0051] Preferably, the cross-correlation velocity is used as the gas phase velocity of the bubble. For node P(i,j), the cross-correlation function of the two layers of wire mesh probes of the same wire mesh probe sensor at this node satisfies the following formula:

[0052]

[0053] Among them, R i,j (Δk) is the cross-correlation coefficient of node P(i,j) when the delay is Δk frames, f i,j (k) and g i,j (k) represents the cavitation fraction measured by the two sets of wire mesh probes at node P(i,j) at the instant.

[0054] Preferably, for node P(i,j), the calculation of the interface satisfies the following formula:

[0055]

[0056] Among them, R i,j,k Let k be the normalized signal collected at time k. The local fluid conductivity is measured by the wire mesh probe sensor. Let a be the conductivity of the single-phase fluid in the rod bundle experimental section. i,j,k Let be the cavitation fraction at time k.

[0057] Preferably, in this embodiment, the number of delayed frames corresponding to the peak value of the cross-correlation coefficient is also used as the average phase velocity of node P(i,j) during the measurement time, which satisfies the following functional formula:

[0058]

[0059] Where L is the axial distance between the two sets of wire mesh probes, and f is its imaging frequency.

[0060] Preferably, in this embodiment, when calculating the bubble phase interface concentration, all elements of the bubble are first extracted, and the phase interface side length, area, and bubble volume within the identified bubble region in each frame are calculated. The phase interface area within the identified bubble region satisfies the following formula:

[0061]

[0062] The gas phase volume within the identified bubble region is:

[0063]

[0064] Where, Δz=v i,j / f sample f is the height between the two layers of wire mesh probe structures. sample A is the sampling frequency of the probe. i,j,k This is the area inside the isocavity fraction line within the region obtained by integrating over the identified gas phase boundary.

[0065] Preferably, in this embodiment, the calculation of the local cavitation fraction satisfies the following formula:

[0066]

[0067]

[0068] Among them, A i,j,in and A i,j,total These represent the flow channel area and total cross-sectional area of ​​the rod bundle experimental section, respectively, α area The area-average gas content, This represents the time-averaged cavitation fraction.

[0069] Preferably, the measured gas phase volume within the double-layer wire mesh probe structure satisfies the following functional relationship:

[0070]

[0071] Preferably, the phase interface concentration within the measured double-layer wire mesh probe structure satisfies the following functional relationship:

[0072]

[0073] Where, j g For apparent air velocity, j f For apparent liquid velocity, A duct t is the cross-sectional area of ​​the flow channel. meas The measurement time.

[0074] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A system for measuring the concentration at the gas-liquid two-phase flow interface within a channel, characterized in that, include: Experimental setup and circuit acquisition module; The experimental setup includes a rod bundle experimental section, a gas-water mixer, and several wire mesh probe sensors. A spiral cross-shaped fuel rod bundle is fixed within the rod bundle experimental section. The gas-water mixer is connected to the bottom of the rod bundle experimental section and is configured to receive gas and water respectively, mix them to form a gas-liquid two-phase flow, and then introduce it into the rod bundle experimental section. Several wire mesh probe sensors are horizontally arranged within the rod bundle experimental section. Each wire mesh probe sensor includes two layers of wire mesh probes, and each layer of wire mesh probes includes an emitter, a receiver, and a measuring point. The circuit acquisition module is connected to the wire mesh probe sensor. The wire mesh probe, the different phase fluid media in the rod bundle experimental section and the circuit acquisition module form a loop, and the different phase fluid media are connected in parallel. The circuit acquisition module is configured to provide an excitation voltage to the wire mesh probe and output different electrical signal values ​​after passing through the loop to identify different phase states in the rod bundle experimental section. The measurement system is configured to perform the following steps: Water is supplied to the gas-water mixer through the water inlet, and gas is injected into the gas-water mixer through the gas inlet. The gas and liquid phases are fully mixed in the gas-water mixer. The mixed gas-liquid two-phase flow enters the rod bundle experimental section; When the gas-liquid two-phase flow passes through the wire mesh probe sensor, different electrical signals are generated due to the different electrical conductivities of the gas and liquid phases. The generated signals are received by the circuit acquisition module through the receiving end. After data processing, the relevant parameters of the gas-liquid two-phase flow field and phase interface concentration in the rod bundle experimental section are obtained. The calculation of the phase interface satisfies the following formula: in, for The normalized signal collected at each moment, The local fluid conductivity is measured by the wire mesh probe sensor. The conductivity is the electrical conductivity of the single-phase fluid in the rod bundle experimental section. for The cavitation fraction at any given moment; The calculation of the local cavitation fraction satisfies the following formula: in, and These represent the flow channel area and total cross-sectional area of ​​the rod bundle experimental section, respectively. The area-average gas content, This represents the average hourly void fraction. The gas phase volume within the two layers of the wire mesh probe measured satisfies the following functional relationship: The phase interface concentration within the two layers of the wire mesh probe is calculated according to the following formula: in, To represent apparent air velocity, For apparent liquid velocity, This represents the cross-sectional area of ​​the flow channel. The measurement time.

2. The system for measuring the concentration at the gas-liquid two-phase flow interface within a channel according to claim 1, characterized in that, The spiral cross fuel rod bundles in the rod bundle experimental section are arranged with equal diameter and pitch. The cross section of the rod bundle experimental section is a square structure with a cross section of 66.1 mm × 66.1 mm. The hydraulic diameter of the rod bundle experimental section is 10.28 mm. The diameter of the spiral cross fuel rod bundle is 9.5 mm. The spacing between adjacent spiral cross fuel rod bundles is 12.6 mm. The hydraulic diameter of the flow field region directly enclosed by adjacent spiral cross fuel rod bundles is 8.321 mm.

3. The system for measuring the concentration at the gas-liquid two-phase flow interface within a channel according to claim 1, characterized in that, Each layer of the wire mesh probe includes a mesh structure with 32*32 intersections and a total of 1024 test points. The nodes on the two connected ends of the wire mesh structure are the transmitter and receiver, respectively. Each test point, transmitter, and receiver is equipped with a 0.1 mm diameter stainless steel electrode wire, which is soldered onto a 2 mm thick PCB circuit board. The spacing between adjacent electrode wires is 2 mm, and the axial distance between adjacent wire mesh probes is 2 mm.

4. The system for measuring the concentration at the gas-liquid two-phase flow interface within a channel according to claim 3, characterized in that, Thirty-two identical insulating connectors are embedded between the transmitter and receiver, and the electrode wires that are in contact with the cross-section of the insulating connectors are covered with insulating adhesive.

5. The system for measuring the concentration at the gas-liquid two-phase flow interface in a channel according to claim 1, characterized in that, The gas-water mixer has a height of 1500 mm, and a mixing channel with an inner diameter of about 1.2 mm and a length of 1000 mm is provided at the connection between the gas-water mixer and the experimental section of the rod bundle.

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