An experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel

Abstract

The present invention discloses an experimental device for measuring the wall pressure field downstream of a grid in a rod bundle channel. In view of the problem that the conventional pressure measurement method is difficult to accurately measure the pressure field of the wall downstream of the grid due to the complex structure of the rod bundle and the narrow space of the internal channel, an open metal tube is arranged in the rod bundle flow channel body, and a quartz glass window is arranged on the open metal tube as a working window of a hard rod endoscope; the endoscope is built into the open metal tube, wherein one end of the hard rod endoscope that penetrates into the open metal tube is provided with a front lighting window, and the laser of an external laser generator is irradiated from the quartz glass window to the target rod bundle through an optical fiber light guide; the other end of the endoscope is connected to an optical signal collector for collecting the reflected light signal after the laser is irradiated to the target rod bundle to obtain the corresponding light intensity, so as to obtain the pressure value corresponding to the light intensity according to the pre-obtained calibration curve of light intensity and pressure, so as to effectively obtain the pressure field of the wall downstream of the grid.

Description

Technical Field

[0001] The invention belongs to the technical field of reactor thermal fluid experimental measurement, and in particular relates to an experimental device for measuring the wall pressure field downstream of a grid in a rod bundle channel. Background Art

[0002] If nuclear energy wants to develop in the fierce competition, it must improve its benefits under the premise of safety and reliability. One of the core components of a nuclear reactor is the fuel assembly, and its internal flow and heat transfer characteristics are closely related to the safety, reliability and economy of the reactor. Therefore, the study of heat and mass transfer inside the fuel assembly is an important part of the entire core thermal hydraulic research.

[0003] The spacer grid is one of the components in the fuel assembly that has a greater impact on the thermal hydraulic performance. The mixing wings on the grid disturb the fluid, causing uneven pressure distribution, enhanced turbulent pulsation, and inducing lateral velocity, thereby achieving the purpose of enhancing heat transfer. The study of the spacer grid on the thermal performance of fuel assemblies began in the 1960s. Domestic and foreign scholars have carried out a lot of experimental and computational work, using CFD methods to study the flow characteristics of the fluid in the rod bundle channel, proving that CFD can provide guidance for the design and optimization of the spacer grid.

[0004] In conventional commercial pressurized water reactors, fuel elements are usually installed in the core in the form of square-arranged rod bundles. The rod bundles are positioned by grids and are key resistance components that affect the reactor flow field. The mixing grid can enhance the mixing effect between the rod bundle channels, effectively enhance the heat exchange capacity and critical heat flux density, and improve the safety and economy of the reactor.

[0005] In reactor safety analysis and new grid design, measuring the rod wall pressure field downstream of the grid in the rod bundle flow channel is of great significance for understanding the grid performance. However, due to the complex structure of the rod bundle and the narrow internal channel space, it is difficult to accurately measure the pressure field on the grid downstream wall using conventional pressure measurement methods. Summary of the invention

[0006] The purpose of the present invention is to provide an experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel, which can effectively measure the pressure field of the wall downstream of the grid.

[0007] To solve the above problems, the technical solution of the present invention is:

[0008] An experimental device for measuring the wall pressure field downstream of a grid in a rod bundle channel comprises: a rod bundle channel body, an endoscope, a laser generator, and an optical signal collector;

[0009] The rod bundle in the rod bundle flow channel body includes an open metal tube, and a window is provided on the open metal tube, which serves as a working window of the endoscope;

[0010] The endoscope is built into the open metal tube;

[0011] The endoscope is inserted into one end of the open metal tube to install a front lighting window, and the laser generator irradiates the laser from the quartz glass window to the target rod bundle through optical fiber light guide;

[0012] The other end of the endoscope is connected to the optical signal collector, which is used to collect the reflected light signal after the laser is irradiated on the target rod bundle to obtain the corresponding light intensity, so as to obtain the pressure value corresponding to the light intensity according to the pre-obtained calibration curve of light intensity and pressure.

[0013] According to an embodiment of the present invention, the experimental device further comprises a displacement control assembly for changing the position of the metal grid in the rod bundle flow channel body;

[0014] The displacement control assembly includes a magnetic member, a support block, a connecting member and a driver. The supporting block is placed under the magnetic member and is used to support the magnetic member. One end of the connecting member passes through the magnetic member and is connected to the supporting block. The other end of the connecting member is connected to the driver and is driven by the driver to drive the supporting block to move.

[0015] The displacement control assembly is built into the rod bundle, and the magnetic member is attracted to the metal grid outside the rod bundle, and the position of the metal grid is changed under the operation of the driver.

[0016] According to an embodiment of the present invention, the surface of the rod bundle in the rod bundle flow channel body is evenly coated with pressure-sensitive paint.

[0017] Due to the adoption of the above technical solution, the present invention has the following advantages and positive effects compared with the prior art:

[0018] In one embodiment of the present invention, an experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel is used to solve the problem that the conventional pressure measurement method is difficult to accurately measure the pressure field of the wall downstream of the grid due to the complex structure of the rod bundle and the narrow internal channel space. An open metal tube is set in the rod bundle flow channel body, and a window is set on the open metal tube as the working window of the endoscope; the endoscope is built into the open metal tube, wherein one end of the endoscope that penetrates into the open metal tube is equipped with a front lighting window, which is connected to an external laser generator through an optical fiber, and the generated laser is guided by the optical fiber and irradiated from the working window to the target rod bundle; the other end of the endoscope is connected to an optical signal collector, which is used to collect the reflected light signal after the laser is irradiated to the target rod bundle, and obtain the corresponding light intensity, so as to obtain the pressure value corresponding to the light intensity according to the pre-obtained calibration curve of light intensity and pressure. Compared with the existing measurement method, the pressure field of the downstream wall of the grid can be obtained more effectively. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 A schematic diagram of a pressure field test experimental circuit in one embodiment of the present invention;

[0020] Figure 2 Schematic diagram of a rod bundle flow channel body in one embodiment of the present invention;

[0021] Figure 3 is a schematic diagram of an open metal tube in one embodiment of the present invention;

[0022] Figure 4 is a schematic diagram of the position of an endoscope in one embodiment of the present invention;

[0023] Figure 5 FIG. 4 is a schematic diagram of a displacement control component in an embodiment of the present invention.

[0024] Description of reference numerals:

[0025] 1: rod bundle flow channel body; 2: open metal tube; 3: target rod bundle; 4: endoscope; 5: laser generator; 6: optical signal collector; 7: window; 8: magnetic part; 9: support block; 10: connector; 11: driver; 12: metal grid; 13: acrylic flow channel; 14: fixing pin; 15: fan; 16: rotor flowmeter. DETAILED DESCRIPTION

[0026] The following is a further detailed description of an experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel proposed by the present invention in conjunction with the accompanying drawings and specific embodiments. The advantages and features of the present invention will become more apparent from the following description and claims.

[0027] Please see Figure 1 The experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel in this embodiment is applied to Figure 1 In the pressure field test experimental loop, the flow rate of the loop medium is controlled by the fan 15, and the rotor flowmeter 16 measures the flow rate before entering the experimental stage. After the loop state is stable, the wall pressure field downstream of the grid in the rod bundle channel is measured. When the flow measured by the rotor flowmeter 16 does not change with time, the loop state can be considered stable.

[0028] For details, please see Figure 2 to Figure 4The experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel includes a rod bundle flow channel body 1, an endoscope 4, a laser generator 5, and an optical signal collector 6, wherein the rod bundle in the rod bundle flow channel body 1 includes an open metal tube 2, and a window 7 is provided on the open metal tube 2 as a working window of the endoscope 4. To ensure that the medium in the flow channel does not enter the metal tube, the window 7 can be a quartz glass window or a window of other materials with good light transmittance. The endoscope 4 is built into the open metal tube 2, and the end of the endoscope 4 is installed with a front lighting window deep into the open metal tube 2, which is connected to the external laser generator 5 through an optical fiber. The laser generated by the laser generator 5 is guided by the optical fiber and then irradiated from the working window to the target rod bundle 3. The other end of the endoscope 4 is connected to the optical signal collector 6, which is used to collect the reflected light signal after the laser is irradiated on the target rod bundle 3 to obtain the corresponding light intensity, so as to obtain the pressure value corresponding to the light intensity according to the calibration curve of light intensity and pressure obtained in advance.

[0029] It should be noted that the fuel rod bundles of the experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel in this embodiment are replaced by metal tubes, such as aluminum alloy tubes. The experimental device in this embodiment is described below using a 3×3 rod bundle flow channel body as an example.

[0030] like Figure 2 As shown, the rod bundle flow channel is an acrylic flow channel 13, which has 9 rod bundles (i.e., 9 metal tubes) arranged in a square, and each rod bundle is positioned by a grid. Among them, the rod bundle located at the midpoint of each side of the square is an open metal tube 2. Please refer to Figure 3 The open metal tube is 1500 mm long and has a 10 mm long opening on it. Quartz glass is installed on the opening to form a window 7, which serves as a working window of the endoscope 4. The window 7 can ensure that the laser and its reflected light can pass through the window.

[0031] like Figure 4 As shown, the endoscope 4 is built into the open metal tube 2. The end of the endoscope 4 that goes deep into the open metal tube 2 is installed with a front lighting window, which is connected to the external laser generator 5 through an optical fiber. The laser generated by the laser generator 5 is guided by the optical fiber and then irradiated from the working window to the target rod bundle 3. The other end of the endoscope 4 is connected to the optical signal collector 6, which is used to collect the reflected light signal after the laser is irradiated to the target rod bundle 3 (in actual application, the reflected light signal is received by the camera on the endoscope and then transmitted to the optical signal collector 6 connected thereto) to obtain the corresponding light intensity, so as to obtain the pressure value corresponding to the light intensity according to the pre-obtained calibration curve of light intensity and pressure.

[0032] In order to measure the pressure on the surface of the target rod bundle 3, pressure-sensitive paint needs to be evenly applied on the surface of the target rod bundle 3. The endoscope 4 is an optical hard rod scope, the laser at its front end irradiates the surface of the target rod bundle 3, and the end is connected to the optical signal collector 6 through an interface. The optical signal collector 6 can be a CCD camera, which is a color camera and can obtain the intensity of the optical signal.

[0033] In practical applications, the relationship between light intensity and pressure needs to be calibrated in advance to obtain a calibration curve between light intensity and pressure. The light signal measured in subsequent experiments is converted through the calibration curve to obtain the pressure result. The relationship between the luminous intensity I and the air pressure P is described by the Stern-Volmer relationship:

[0034]

[0035] Among them, I ref and P ref is the luminous intensity and air pressure under reference conditions, which is one of the experimental values ​​in the calibration experiment. A and B are unknown parameters obtained by fitting the calibration data.

[0036] In order to obtain the pressure field at different distances downstream of the grid, the grid position needs to be changed. This embodiment achieves the change of the grid position through a displacement control component. Figure 5 The displacement control assembly includes a magnetic member 8, a support block 9, a connector 10 and a driver 11, wherein the support block 9 is placed under the magnetic member 8 to support the magnetic member 8. One end of the connector 10 passes through the magnetic member 8 and is connected to the support block 9, and the other end of the connector 10 is connected to the driver 11, and is driven by the driver 11 to drive the support block 9 to move. The displacement control assembly is built into the target rod cluster 3, and is attracted to the metal grid 12 outside the rod cluster through the magnetic member 8. Under the operation of the driver 11, the position of the metal grid 12 is changed.

[0037] The magnetic member 8 is a strong magnet that can attract the metal grid 12 outside the rod bundle and can move with the metal grid 12. The metal grid 12 can be made of stainless steel. The driver 11 can be a one-dimensional electric lifting platform, and the connecting member 10 is a connecting rod matched with the driver 11. The connecting rod can be provided with a scale. The position of the metal grid 12 is determined by the height of the connecting rod rising or falling, so that the positioning hole can be arranged at the corresponding position of the acrylic flow channel 13, and the metal grid 12 is fixed by the positioning pin 14.

[0038] In order to obtain the complete surface pressure field of the target rod bundle 3, the endoscope 4 needs to be placed in four metal tubes 2 with different openings for measurement.

[0039] The experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel provided in this embodiment aims at the problem that the conventional pressure measurement method is difficult to accurately measure the pressure field of the wall downstream of the grid due to the complex structure of the rod bundle and the narrow internal channel space. By setting an open metal tube in the rod bundle flow channel body, a window is set on the open metal tube as the working window of the endoscope; the endoscope is built into the open metal tube, wherein one end of the endoscope that penetrates into the open metal tube is equipped with a front lighting window, which is connected to the external laser generator through an optical fiber, and the generated laser is guided by the optical fiber and irradiated from the working window to the target rod bundle; the other end of the endoscope is connected to an optical signal collector, which is used to collect the reflected light signal after the laser is irradiated to the target rod bundle, and obtain the corresponding light intensity, so as to obtain the pressure value corresponding to the light intensity according to the pre-obtained calibration curve of light intensity and pressure. Compared with the existing measurement method, the pressure field of the downstream wall of the grid can be obtained more effectively.

[0040] The embodiments of the present invention are described in detail above in conjunction with 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 still fall within the protection scope of the present invention.

Claims

1. An experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel, characterized in that: include: Rod bundle flow channel body, endoscope, laser generator, optical signal collector; The rod bundle in the rod bundle flow channel body includes an open metal tube, and a window is provided on the open metal tube, which serves as a working window of the endoscope; The endoscope is built into the open metal tube; The endoscope is inserted into one end of the open metal tube to install a front lighting window, and the laser generator irradiates the laser from the window to the target rod bundle through optical fiber light guide; The other end of the endoscope is connected to the optical signal collector, which is used to collect the reflected light signal after the laser is irradiated on the target rod bundle to obtain the corresponding light intensity, so as to obtain the pressure value corresponding to the light intensity according to the pre-obtained calibration curve of light intensity and pressure.

2. The experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel according to claim 1, characterized in that: Also included is a displacement control assembly for changing the position of the metal grid in the rod bundle flow channel body; The displacement control assembly includes a magnetic member, a support block, a connecting member and a driver. The supporting block is placed under the magnetic member and is used to support the magnetic member. One end of the connecting member passes through the magnetic member and is connected to the supporting block. The other end of the connecting member is connected to the driver and is driven by the driver to drive the supporting block to move. The displacement control assembly is built into the rod bundle, and the magnetic member is attracted to the metal grid outside the rod bundle, and the position of the metal grid is changed under the operation of the driver.

3. The experimental device for measuring the wall pressure field downstream of the grid in the rod bundle channel according to claim 1, characterized in that: The surface of the rod bundle in the rod bundle flow channel body is evenly coated with pressure-sensitive paint.

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