Passive nuclear power plant air flow channel flow field visualization simulation test system and method

Abstract

The invention provides a visual simulation test system and method for a flow field of an air flow channel of a passive nuclear power plant, and the method comprises the steps: respectively simulating a heat insulation plate and a heating plate on the wall surface of a shielding plant and the outer wall surface of a heated containment after an accident; the at least three positioning windows and the laser emitter cover the middle part, the bottom part and the key area below the air guide plate, and a dynamic flow field visualization result can be obtained through a processing terminal in signal connection with a high-speed camera by combining the high-speed camera on the outer side of the visual plate and an air inlet flow channel for conveying a fluid medium containing adaptive tracer particles; furthermore, the real working condition of the air flow channel of the passive nuclear power plant is precisely restored, clear capture and dynamic presentation of a flow field without an observation blind area in a key flow area are realized, and hardware support is provided for acquiring flow field data required by design optimization of an air guide plate; the problems that an existing testing device is low in working condition reduction degree, incomplete in key area observation and not visual in flow field information obtaining are effectively solved.

Description

Technical Field

[0001] This invention relates to the field of nuclear industry safety technology, specifically to a visualization simulation test system and method for airflow field in passive nuclear power plants. Background Technology

[0002] Air deflectors are key components of the passive containment cooling system (PCS) for third-generation large advanced pressurized water reactors, providing a flow path for air entering the shielded building.

[0003] Air enters the containment building from the inlet and flows downwards along the outer annulus. At the bottom of the baffle, the airflow turns upwards and flows between the inner annulus cavities, eventually exiting through the exhaust port at the top of the containment. After an accident, the PCS can also choose whether to use evaporative cooling with a water film to remove heat from the containment and reduce the pressure inside the containment, depending on the magnitude of core decay heat.

[0004] The number of air deflectors is a crucial factor to consider when conducting design optimization. This is because it significantly impacts not only the construction cost and installation / maintenance of nuclear power plants but also post-accident safety analysis. Reducing the number of deflectors decreases procurement costs, installation time, and the difficulty of periodic dismantling; however, it necessitates an assessment of whether the convective heat transfer capacity meets the requirements of safety analysis.

[0005] However, initial design optimization relies on CFD simulations for performance prediction and scheme modification. Although CFD technology has made significant progress in flow field analysis, its simulation results still have certain biases and limitations, especially under complex flow conditions.

[0006] Based on this, the inventors of this application propose a visualization simulation test system and method for airflow field in passive nuclear power plants, in order to solve one or more of the above-mentioned technical problems. Summary of the Invention

[0007] The present invention solves the above-mentioned technical problems through the following technical solution: This invention provides a visualization simulation test system for airflow field in a passive nuclear power plant, comprising: a housing with a accommodating cavity; two side plates arranged laterally opposite to each other in the housing, namely an insulation plate and a heating plate; the insulation plate is used to simulate the wall of the shielded building; the heating plate is used to simulate the outer wall of the containment vessel that heats up after an accident; and an air guide plate is provided inside the housing and between the insulation plate and the heating plate. The insulation board has at least three positioning windows vertically along the box body. A laser emitter is provided on one side of each positioning window. The light emitted by the laser emitter shines through the positioning window onto the middle area, bottom area and lower area of ​​the air guide plate. The side panel on the housing that is adjacent to both the insulation board and the heating board is a viewing panel. A high-speed camera is installed on the outside of the viewing panel. The high-speed camera is used to capture the area illuminated by the laser emitter. The top plate of the box is a top plate, and an air inlet channel is opened on the side of the top plate near the insulation plate. The air inlet channel is used to fill the accommodating cavity with a fluid medium, which includes a test medium and tracer particles adapted to the test medium. The outer side of the housing is also equipped with a processing terminal that is connected to the high-speed camera signal. The processing terminal is used to receive the image signal transmitted by the high-speed camera to form a dynamic flow field visualization result of the fluid medium.

[0008] According to one embodiment of the present invention, the test medium is air or a mixture of water vapor and air; In the air-cooled condition, the test medium is air, and the suitable tracer particles are oil mist; in the water-cooled condition, the test medium is a mixed gas, and the suitable tracer particles are fluorinated polymers.

[0009] According to one embodiment of the present invention, a beam splitter is provided between the laser emitter and the positioning window; When the test medium is air, the laser emitter emits 532nm green light, which is directly projected onto the positioning window through the beam splitter. When the test medium is a mixed gas, the laser emitter simultaneously emits 532nm green light and 1064nm infrared light, which are projected onto different sections of the high-speed camera by the beam splitter.

[0010] According to one embodiment of the present invention, the accommodating cavity is a scaled-down flow channel structure constructed based on scaled-down modeling analysis; The scaled-down modeling analysis uses Reynolds number... Prandtl numbers and Nusel number The dimensionless reference number is used, and the scaled-down flow channel structure has the same dimensionless reference number as the real air flow channel, so that the flow characteristics and heat transfer characteristics of the fluid medium in the accommodating cavity are consistent with those of the real air flow channel; wherein, The Nusselt number satisfies: and ;in, h λ is the convective heat transfer coefficient, L is the characteristic length, and λ is the fluid thermal conductivity.

[0011] According to one embodiment of the present invention, the image acquisition method of the high-speed camera includes single-camera time-division acquisition, dual-camera independent acquisition, or dual-camera and beam splitter acquisition.

[0012] According to one embodiment of the present invention, a fan is connected to one side of the air intake channel, and the fan is used to transport the fluid medium to the accommodating cavity.

[0013] According to one embodiment of the present invention, the viewing panel is a high-temperature resistant glass panel.

[0014] According to one embodiment of the present invention, the processing terminal has a built-in computer processing program. This program uses a cross-correlation algorithm combined with virtual displacement compensation technology under water-cooling conditions to process the image and generate a two-dimensional velocity vector diagram of the flow field; wherein, The two-dimensional velocity vector map is configured to play in chronological order to form a dynamic flow field visualization animation.

[0015] This invention also provides a method for visual simulation testing of airflow field in passive nuclear power plants, employing the visual simulation testing system for airflow field in passive nuclear power plants as described above. The testing method includes: Step 1: Determine the flow and heat transfer characteristics of the actual airflow channel, and determine the dimensionless criterion number through the flow field conservation equation and heat transfer relation. Step 2: Based on the principle that the dimensionless criterion number of the scaled-down flow channel structure is the same as that of the real air flow channel, determine the proportional relationship of the key parameters of the two, and build the visualization simulation test system after CFD simulation-assisted verification. Step 3: Select the appropriate fluid medium and tracer particles according to the test conditions; for air-cooled conditions, select air as the fluid medium and oil mist as the tracer particles; for water-cooled conditions, select a mixture of steam and air as the fluid medium and fluorinated polymer as the tracer particles, and introduce the fluid medium and tracer particles together into the chamber of the test chamber. Step 4: Turn on the laser emitter and control the high-speed camera to acquire the flow image of the tracer particles in the cavity, and transmit the flow image to the processing terminal; Step 5: The processing terminal uses a built-in computer processing program to analyze the position changes of the tracer particles using a cross-correlation algorithm. Under water-cooling conditions, it combines infrared light to perform virtual displacement compensation and generate a visual animation of the flow field of the visualization simulation test system.

[0016] According to one embodiment of the present invention, the dimensionless criterion number in step 1 includes the Reynolds number Re, the Prandtl number Pr, and the Nusselt number Nu.

[0017] The positive and progressive effects of this invention are as follows: This invention relates to a visualization simulation test system for the airflow field in passive nuclear power plants. It utilizes insulation and heating plates that simulate the walls of the shielded building and the outer walls of the containment vessel after an accident, along with at least three positioning windows and a laser emitter covering the middle, bottom, and lower key areas of the air guide plate. Combined with a high-speed camera on the outside of the visualization plate and an inlet airflow channel conveying a fluid medium containing adaptive tracer particles, the system obtains dynamic flow field visualization results through a processing terminal connected to the high-speed camera signal. This accurately recreates the actual operating conditions of the airflow field in passive nuclear power plants, achieving clear capture and dynamic presentation of the flow field in key flow areas without blind spots. It provides hardware support for acquiring the flow field data required for the design optimization of the air guide plate, effectively solving the problems of low operating condition reproduction, incomplete observation of key areas, and unintuitive flow field information acquisition in existing testing devices. Attached Figure Description

[0018] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein: Figure 1 This is a schematic diagram of the structure of the passive nuclear power plant airflow channel flow field visualization simulation test system of the present invention; Figure 2 This is a scaled-down flowchart of the accommodating cavity of the present invention; Figure 3 This is a visual flowchart of the invention under different operating conditions; Figure 4 This is a diagram illustrating the shooting technology roadmap of one embodiment of the high-speed camera of the present invention. Figure 5 This is a diagram illustrating the imaging technology roadmap for another embodiment of the high-speed camera of the present invention. Figure 6 This is a diagram illustrating the imaging technology roadmap for another embodiment of the high-speed camera of the present invention. Figure 7 This is a roadmap illustrating the shooting technology of another embodiment of the high-speed camera of the present invention.

[0019] 1. Cabinet; 11. Receptacle; 12. Insulation board; 121. Positioning window; 13. Heating plate; 14. Visible panel; 15. Top plate; 2. Air deflector; 3. Laser emitter; 31. Beam splitter; 4. High-speed camera; 5. Air intake duct; 51. Fan; 6. Processing terminal. Detailed Implementation

[0020] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0021] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0022] The core requirements for the design optimization of the air deflector 2 in the passive containment cooling system are: to reduce the construction cost and operation and maintenance difficulty of nuclear power plants by reducing the number of deflectors, and to accurately verify the convective heat transfer capacity to meet the safety analysis requirements. However, existing CFD simulations have deviations under complex flow conditions and cannot meet its optimization requirements.

[0023] Based on this, this application proposes a visualization simulation test system for airflow field in a passive nuclear power plant, including a housing 1. The housing 1 has a accommodating cavity 11. Two side plates arranged laterally opposite to each other in the housing 1 are an insulation plate 12 and a heating plate 13. The insulation plate 12 is used to simulate the wall of the shielded building, and the heating plate 13 is used to simulate the outer wall of the containment vessel that heats up after an accident. An air guide plate 2 is provided inside the housing 1 and between the insulation plate 12 and the heating plate 13.

[0024] like Figure 1 As shown, the enclosure 1 has a rectangular column structure, consisting of a top plate 15, four peripheral side plates, and a bottom plate forming a closed accommodating cavity 11. The two horizontally opposite vertical peripheral side plates correspond to the insulation plate 12 and the heating plate 13, respectively, to simulate the relative positions and thermal environment of the shielded building wall and the outer wall of the containment structure in a real nuclear power plant. The heating plate 13 can be heated by resistance wire heating, fluid heat exchange, or electromagnetic induction heating, and its heating power can be adjusted according to the actual containment accident temperature rise curve to accurately simulate the wall temperature conditions at different accident stages. The specific heating method is not limited here.

[0025] For the accommodating cavity 11 inside the housing 1, the accommodating cavity 11 is a scaled-down flow channel structure constructed based on scaled-down modeling analysis; the scaled-down modeling analysis uses Reynolds number... Prandtl numbers and Nusel number The Nusselt number is a dimensionless criterion number, and the scaled-down flow channel structure has the same dimensionless criterion number as the real air flow channel, so that the flow characteristics and heat transfer characteristics of the fluid medium in the accommodating cavity 11 are consistent with those of the real air flow channel; wherein, the Nusselt number satisfies: and ;in, h λ is the convective heat transfer coefficient, L is the characteristic length, and λ is the fluid thermal conductivity.

[0026] like Figure 2 As shown, the modeling analysis process is as follows: First, the flow field and heat transfer characteristics inside the prototype airflow channel are studied. Based on the flow field conservation equations (including mass conservation, energy conservation, and momentum conservation equations) and heat transfer relations, the above dimensionless criterion numbers are determined. Then, the proportional relationship of key parameters between the model and the prototype can be determined. Subsequently, a three-dimensional model of the prototype and a scaled-down three-dimensional model are established. Then, the two three-dimensional models are imported into CFD simulation software to verify the heat flux density relationship between the prototype and the scaled-down model.

[0027] This application constructs a flow channel structure for cavity 11 based on a scaled-down model analysis using three core dimensionless criteria: Reynolds number, Prandtl number, and Nusselt number. This ensures that the scaled-down model is completely equivalent to the flow and heat transfer characteristics of a real airflow channel, solving the technical pain points of large scale, high experimental cost, and difficult operation of real flow channels. At the same time, by clarifying the calculation formula of the Nusselt number, it provides a scientific basis for the quantitative analysis of experimental data, ensuring the reliability and accuracy of the experimental results.

[0028] Please continue to refer to Figure 1 For the air guide plate 2, the top of the air guide plate 2 is fixedly connected to the top plate 15 of the box 1. The whole is arranged vertically along the box 1, and its bottom end extends towards the bottom plate. A preset distance is reserved between it and the bottom plate to form a channel for the flow of fluid medium, simulating the function of the guide plate in guiding the airflow to turn and split in a real air flow channel.

[0029] The insulation board 12 is provided with at least three positioning windows 121 spaced apart from top to bottom along the box body 1. A laser emitter 3 is provided on one side of the positioning window 121. The laser emitted by the laser emitter 3 can penetrate the positioning window 121 and irradiate the middle area, bottom area and lower area of ​​the air guide plate 2, so as to achieve full coverage illumination of the key flow field area around the guide plate.

[0030] like Figure 1 As shown, this application uses three positioning windows 121 as an example for illustration. Among the three positioning windows 121, the upper positioning window 121 corresponds to the middle area of ​​the air deflector 2, the middle positioning window 121 corresponds to the bottom area of ​​the air deflector 2, and the lower positioning window 121 corresponds to the lower area of ​​the air deflector 2.

[0031] Specifically, the side of the air deflector 2 facing the insulation board 12 forms a projected area on the surface of the insulation board 12. The upper positioning window 121 is opened within this projected area to ensure that the laser emitted through this window can directly irradiate the middle area of ​​the air deflector 2. The middle positioning window 121 is opened at the bottom edge of this projected area to match the bottom area of ​​the air deflector 2. The lower positioning window 121 is opened below the projected area to cover the flow channel area between the bottom of the air deflector 2 and the housing 1.

[0032] Therefore, the laser can be directed to different key areas of the air deflector 2 through three positioning windows 121, meeting the requirements for simultaneous observation of the flow field in multiple regions. Two configuration schemes can be adopted for the laser emitter 3: The first is a one-to-one configuration, where three laser emitters 3 are set up, each equipped with a single laser emitter head, and arranged one-to-one with the three positioning windows 121. This allows for simultaneous laser emission from the middle, bottom, and lower regions of the air deflector, eliminating the need for additional optical components for beam splitting and directly achieving simultaneous observation of the flow field in multiple regions, significantly improving experimental efficiency. The second is a configuration with fewer laser emitters 3 and multiple windows, where only one or two laser emitters 3 are set up. By flexibly combining single or multiple emitters and using optical components such as the beam splitter prism 31 for laser beam splitting and control, the laser output from a single laser emitter 3 can be precisely directed to different positioning windows 121. When using multiple emitters, simultaneous illumination of multiple windows can be achieved through the beam splitter prism 31; when using a single emitter, sequential illumination of different windows can be completed through timing switching. This solution can effectively reduce equipment investment costs and adapt to the needs of test scenarios of different scales.

[0033] Please continue to refer to Figure 1 The side panel adjacent to both the insulation plate 12 and the heating plate 13 on the housing 1 is a viewing panel 14. A high-speed camera 4 is installed on the outer side of the viewing panel 14, which is used to capture images of the area illuminated by the laser emitter 3. The top panel of the housing 1 is a top panel 15. An air inlet channel 5 is opened on the top panel 15 near the insulation plate 12. The air inlet channel 5 is used to fill the accommodating cavity 11 with a fluid medium, which includes the test medium and tracer particles adapted to the test medium. A processing terminal 6 connected to the high-speed camera 4 is also installed on the outer side of the housing 1. The processing terminal 6 is used to receive the image signals transmitted by the high-speed camera 4 to form a dynamic flow field visualization result of the fluid medium.

[0034] Specifically, during the flow field test, the fluid medium is transported to the containment cavity 11 through the air inlet channel 5. It first flows into the area between the air guide plate 2 and the insulation plate 12 and flows vertically downward. When it reaches the gap between the bottom of the air guide plate 2 and the bottom plate of the box 1, it turns and then flows upward into the area between the air guide plate 2 and the heating plate 13. In this process, the turning and heat exchange process of the airflow in the air channel of a real nuclear power plant is fully simulated. Finally, it flows out of the containment cavity 11 through the exhaust outlet of the top plate 15.

[0035] For the air intake channel 5, it can adopt an air intake pipe structure, with one end installed on the top plate 15 of the box 1 and the other end connected to the fan 51. Through the power output of the fan 51, the uniformly mixed test medium and tracer particles are continuously transported into the accommodating cavity 11.

[0036] By configuring a fan 51 on the side of the air inlet duct 5, a stable and controllable fluid transport power can be provided to the accommodating cavity 11, thereby accurately simulating the fluid velocity and flow state in the airflow channel of a real nuclear power plant. This effectively avoids the defects of large fluctuations in medium velocity and uncontrollable flow field state under natural filling methods, and solves the problems of high dispersion and poor repeatability of test data caused by unstable flow velocity. Operators can flexibly adapt to the flow velocity requirements under different test conditions such as air cooling and water cooling by adjusting parameters such as the fan speed and air pressure of the fan 51, further improving the adaptability of the entire testing system and the accuracy and reliability of the test data.

[0037] As described above, this application accurately reproduces the real working environment of the airflow channel in a passive nuclear power plant by constructing a cavity 11 containing an insulation plate 12, a heating plate 13, and an air guide plate 2. At the same time, it uses at least three positioning windows 121 in conjunction with a laser emitter 3 to achieve full coverage illumination of the middle, bottom, and lower key areas of the guide plate. Combined with a high-speed camera 4 on the outside of the visual plate 14 and a signal-connected processing terminal 6, it can directly capture the motion trajectory of tracer particles in the flow field and form dynamic visualization results. This solves the technical problems of blind spots in key areas, low working condition reproduction, and unintuitive flow field information acquisition in existing testing devices, and provides structurally stable and functionally complete hardware support for the design optimization of the air guide plate 2.

[0038] In one embodiment, the aforementioned viewing panel 14 is made of high-temperature resistant glass. This design can effectively cope with two types of complex working conditions: one is the high-temperature environment caused by the heating plate 13 simulating the temperature rise of the outer wall of the containment vessel after an accident, and the other is the high-temperature and high-humidity environment formed in the accommodating cavity 11 under water-cooling conditions. It can completely avoid the risk of test interruption caused by the deformation of ordinary glass due to thermal expansion and contraction and high-temperature cracking, and ensure the continuity of the testing process.

[0039] Meanwhile, the high-temperature resistant glass plate also has excellent light transmittance, which can minimize laser attenuation and imaging distortion, ensuring that the high-speed camera 4 can clearly capture the motion trajectory of the tracer particles in the accommodating cavity 11, laying the foundation for the subsequent processing terminal 6 to accurately analyze the flow field data, thereby ensuring the stable operation of flow field observation and the reliability of experimental results.

[0040] Please refer to Figure 3 Because the test conditions are divided into two containment cooling methods based on the decay heat after the accident: air cooling and water film cooling, corresponding to... Figure 3 Air cooling and water cooling are used. The selection of tracer particles and laser wavelengths are precisely matched to the flow field medium density and environmental conditions under the corresponding operating conditions.

[0041] Under air-cooled conditions, the flow medium is pure air. Therefore, oil mist is selected as the tracer particles because its particle size is well-suited to the air flow field and can diffuse uniformly within the flow field, providing a clear imaging target for the high-speed camera 4. Regarding the selection of the corresponding laser wavelength, the difference in refractive index of 532nm green light propagating in a pure air flow field is extremely small, and the virtual displacement of the imaging is negligible. Therefore, the laser emitter 3 only needs to emit green light to meet the flow field observation requirements.

[0042] Under water film cooling conditions, the evaporation of the water film creates a mixed flow field of steam and air. This environment is characterized by high temperature and high humidity, so fluorinated polymers are selected as tracer particles. Fluorinated polymers possess excellent chemical corrosion resistance, heat resistance, and hydrophobicity, effectively preventing high-temperature steam from damaging the particle structure and avoiding particle aggregation due to liquid water droplets adsorbed. This ensures uniform particle distribution within the mixed flow field, significantly improving the imaging signal-to-noise ratio and particle tracking accuracy. To address the issue of green light being susceptible to steam interference under these conditions, a dual-wavelength combination of 532nm green light and 1064nm infrared light is employed: green light is used to capture the trajectory of the tracer particles, while infrared light, with its strong penetrating power and low scattering interference from steam, can compensate for the virtual displacement caused by the difference in refractive index of the green light due to steam, and also weaken the Mie scattering effect of liquid water droplets in the steam on the laser, reducing imaging background noise. By controlling the beam splitting of the beam splitter 31, two wavelengths of laser light can be projected onto different areas of the high-speed camera 4, such as the upper and lower halves or the left and right sections, so that the subsequent processing terminal 6 can accurately correct the flow field velocity based on the dual-wavelength imaging data.

[0043] Further, please refer to Figures 4 to 7 The high-speed camera 4 can acquire images in several ways, including single-camera time-division acquisition, dual-camera independent acquisition, or dual-camera and beam splitter 31 acquisition.

[0044] like Figure 4Laser emitter 3 emits both green and infrared light simultaneously. The two lights are mixed into a single beam and emitted towards beam splitter 31. Beam splitter 31 separates the infrared and green light. The sensor of high-speed camera 4 is pre-divided, for example, the upper half receives the green light and the lower half receives the infrared light, simultaneously capturing images of tracer particles illuminated by both lights. This is equivalent to taking a picture at the same time, obtaining both the green light flow field map and the infrared light flow field map simultaneously, without any time difference. This method is suitable for water-cooled applications and is relatively low in cost.

[0045] like Figure 5 This method uses a single-camera time-division acquisition system, where the high-speed camera sequentially captures infrared and green light in four short intervals. This single-camera time-division acquisition approach is low-cost, easy to operate, and suitable for small-scale experimental scenarios.

[0046] like Figure 6 and Figure 7 All images were taken with dual cameras and a beam splitter 31. Figure 6 In the process, laser emitter 3 emits green light and infrared light simultaneously, and the mixed light directly illuminates the tracer particles in the flow field; two high-speed cameras 4 take pictures at the same time, and filters are used to ensure that each high-speed camera 4 only receives the reflected light of the corresponding wavelength, and outputs green light flow field map and infrared light flow field map respectively. Figure 7 In the process, the mixed light emitted by the laser emitter 3 is directed toward the beam splitter 31. The beam splitter 31 separates the light by physical optical path, directing the green light to the first camera and the infrared light to the second camera. The two cameras shoot simultaneously under the trigger of the synchronization control system, and the beam splitter 31 ensures that the shooting fields of the two cameras are completely consistent.

[0047] Furthermore, the high-speed camera 4 is connected to the processing terminal 6. The processing terminal 6 has a built-in computer processing program that uses a cross-correlation algorithm combined with virtual displacement compensation technology under water-cooled conditions to process the image and generate a two-dimensional velocity vector map of the flow field. This two-dimensional velocity vector map is configured to play in chronological order to form a dynamic flow field visualization animation. If only air-cooled conditions are used, the computer processing program can generate the two-dimensional velocity vector map of the flow field using only the cross-correlation algorithm.

[0048] This application, by incorporating a computer processing program with cross-correlation algorithm and virtual displacement compensation technology into the processing terminal 6, can accurately analyze the tracer particle image data collected by the high-speed camera 4, calculate the two-dimensional velocity vector diagram of the flow field, and intuitively present the flow field evolution process through dynamic visualization animation. This solves the problems of low accuracy and abstract results of traditional image processing methods, and provides quantitative and intuitive flow field data support for the optimized design of the air guide plate 2.

[0049] This invention also proposes a visualization simulation test method for the airflow field in a passive nuclear power plant's airflow channel, employing the aforementioned visualization simulation test system for the airflow field in a passive nuclear power plant. The test method includes: Step 1: Determine the flow and heat transfer characteristics of the actual airflow channel, and determine the dimensionless criterion number through the flow field conservation equation and heat transfer relation. Step 2: Based on the principle that the dimensionless criterion number of the scaled-down flow channel structure is the same as that of the real air flow channel, determine the proportional relationship of the key parameters of the two, and build a visual simulation test system after CFD simulation-assisted verification. Step 3: Select the appropriate fluid medium and tracer particles according to the test conditions; for air-cooled conditions, select air as the fluid medium and oil mist as the tracer particles; for water-cooled conditions, select a mixture of steam and air as the fluid medium and fluorinated polymer as the tracer particles, and introduce the fluid medium and tracer particles together into the chamber of the test chamber. Step 4: Turn on the laser emitter and control the high-speed camera to acquire images of the flow of tracer particles in the cavity, and transmit the images to the processing terminal. Step 5: The processing terminal uses a built-in computer processing program to analyze the position changes of the tracer particles using a cross-correlation algorithm. Under water-cooled conditions, it combines infrared light to perform virtual displacement compensation and generate a visual animation of the flow field of the visualization simulation test system.

[0050] The above testing method, by combining multiple key steps such as scaled-down modeling analysis, selection of media and particles adapted to operating conditions, dual-wavelength laser irradiation, image acquisition and precise processing, forms a closed-loop process from modeling, construction, testing to analysis. It can efficiently achieve high-precision visualization observation of the flow field, solve the technical pain points of existing CFD simulations having large deviations under complex flow field conditions and being unable to provide experimental verification data, and provide reliable experimental basis for optimizing the number of air deflectors, taking into account both the safe operation and economic cost control of nuclear power plants.

[0051] In step 1, the dimensionless criterion numbers are defined as Reynolds number Re, Prandtl number Pr, and Nusselt number Nu, which further refines the core basis of the scaled-down modeling analysis. This avoids the problem of inconsistency between the scaled-down model and the actual flow channel characteristics caused by the ambiguity of the criterion number selection, further ensuring the scientific nature and rigor of the modeling analysis. It also ensures that the test system built subsequently can accurately reproduce the flow and heat transfer characteristics of the actual flow channel, thereby improving the reliability and repeatability of the entire test method.

[0052] In the description of the embodiments of this application, unless otherwise expressly specified and limited, the technical terms such as "installation", "connection", "joining", and "fixing" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can also refer to mechanical connections. For those skilled in the art, the specific meaning of the above terms in the embodiments of this application can be understood according to the specific circumstances.

[0053] This application uses specific terms to describe embodiments of the application. Terms such as "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic associated with at least one embodiment of the application. Therefore, it should be emphasized and noted that references to "an embodiment," "one embodiment," or "an alternative embodiment" in different locations throughout this specification do not necessarily refer to the same embodiment. Furthermore, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0054] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. A passive nuclear power plant air flow passage flow field visualization simulation test system, characterized in that, The application relates to a non-active nuclear power plant air flow channel flow field visualization simulation test system. The box body has a containing cavity, and two laterally opposite side plates of the box body are a heat insulation plate and a heating plate respectively, the heat insulation plate is used for simulating a shielding plant wall surface, the heating plate is used for simulating an outer wall surface of a safety shell after an accident, and an air guide plate is arranged in the box body and between the heat insulation plate and the heating plate. The heat insulation plate is vertically provided with at least three positioning windows, one side of the positioning windows is provided with a laser emitter, and light emitted by the laser emitter is irradiated to a middle region, a bottom region and a lower region of the air guide plate through the positioning windows. A side plate adjacent to the heat insulation plate and the heating plate on the box body is a visual plate, a high-speed camera is arranged outside the visual plate, and the high-speed camera is used for shooting regions illuminated by the laser emitter. A top plate is arranged on the top of the box body, an air inlet channel is arranged on the top plate and close to the heat insulation plate, the air inlet channel is used for filling fluid medium into the containing cavity, and the fluid medium comprises test medium and tracer particles matched with the test medium. A processing terminal connected with the high-speed camera in signal is further arranged outside the box body, the processing terminal is used for receiving image signals transmitted by the high-speed camera to form dynamic flow field visualization results of the fluid medium.

2. The passive nuclear power plant air flow passage flow field visualization simulation test system according to claim 1, characterized in that, The test medium is air or mixed gas of water vapor and air. When the air cooling condition is adopted, the test medium is air, and the matched tracer particles are oil mist; when the water cooling condition is adopted, the test medium is mixed gas, and the matched tracer particles are fluorinated polymers.

3. The passive nuclear power plant air flow passage flow field visualization simulation test system according to claim 1, characterized in that, A light splitting prism is arranged between the laser emitter and the positioning window. When the test medium is air, the laser emitter emits 532nm green light which is directly irradiated to the positioning window through the light splitting prism. When the test medium is mixed gas, the laser emitter simultaneously emits 532nm green light and 1064nm infrared light which are respectively projected to different partitions of the high-speed camera through the light splitting prism.

4. The passive nuclear power plant air flow passage flow field visualization simulation test system according to claim 1, characterized in that, The containing cavity is a scaled flow channel structure constructed based on scaled modeling analysis. The scaled modeling analysis takes Reynolds number , Prandtl number and Nusselt number as dimensionless criteria numbers, and the scaled flow channel structure is identical with the dimensionless criteria numbers of the real air flow channel, so that the flow characteristics and heat transfer characteristics of the fluid medium in the accommodating cavity are consistent with the real air flow channel; wherein, The Nusselt number satisfies: and ; wherein, h is the convective heat transfer coefficient, L is the characteristic length, and λ is the thermal conductivity of the fluid.

5. The passive nuclear power plant air flow passage flow field visualization simulation test system according to claim 1, wherein, The image acquisition mode of the high-speed camera comprises single-camera time-sharing acquisition, double-camera independent acquisition or double-camera and light splitting prism acquisition.

6. The passive nuclear power plant air flow passage flow field visualization simulation test system according to claim 1, wherein, A fan is connected to one side of the air inlet channel, and the fan is used for conveying the fluid medium to the containing cavity.

7. The passive nuclear power plant air flow passage flow field visualization simulation test system according to claim 1, wherein, The visual plate is a high-temperature-resistant glass plate.

8. The passive nuclear power plant air flow passage flow field visualization simulation test system according to claim 1, wherein, A computer processing program is arranged in the processing terminal, the computer processing program adopts a cross-correlation algorithm and combines with a virtual displacement compensation technology under the water cooling condition to process images and generate a two-dimensional velocity vector diagram of a flow field; wherein The two-dimensional velocity vector diagram is configured to be able to play a dynamic flow field visualization animation in time sequence.

9. A method for visualizing and simulating the flow field of an air flow path of a passive nuclear power plant, characterized in that, The test method comprises the following steps: Step 1, determining flow characteristics and heat transfer characteristics of a real air flow channel, determining dimensionless criteria numbers through flow field conservation equations and heat transfer relationships; Step 2, based on the principle that the dimensionless criterion number of the scaled flow channel structure is the same as that of the real air flow channel, the proportional relationship of the key parameters of the two is determined, and after CFD simulation verification, the visual simulation test system is formed; Step 3, according to the test working condition, the corresponding fluid medium and tracer particle are selected; wherein, under the air cooling condition, air is selected as the fluid medium, and oil mist is selected as the tracer particle; under the water cooling condition, the mixed gas of steam and air is selected as the fluid medium, and fluorinated polymer is selected as the tracer particle, and the fluid medium and the tracer particle are fed into the accommodating cavity of the box body together; Step 4, the laser emitter is turned on, the high-speed camera is controlled to collect the flow image of the tracer particle in the accommodating cavity, and the flow image is transmitted to the processing terminal; Step 5, the processing terminal generates the visual animation of the flow field of the visual simulation test system by using the cross-correlation algorithm to analyze the position change of the tracer particle through the built-in computer processing program, and combining with the virtual displacement compensation of the infrared light under the water cooling condition.

10. The passive nuclear power plant air flow passage flow field visualization simulation test method of claim 9, wherein, The dimensionless criterion number in the step 1 includes Reynolds number Re, Prandtl number Pr and Nusselt number Nu.

Images