An adaptive resistance regulation device and method for suppressing natural circulation flow oscillations

Abstract

This invention provides an adaptive resistance adjustment device and method for suppressing oscillations in natural circulation flow. Installed on the descending section of a natural circulation system, the adjustment device includes: a rectifier chamber 1, a baffle 2, a spring 3, a sphere 4, a limiting plate 5, and a support rod 6. The size of the rectifier chamber 1 is larger than the size of the descending section of the natural circulation pipe. The baffle 2 is welded to the inner wall of the rectifier chamber 1, and the flow area of ​​the rectifier chamber 1 is not less than the flow area of ​​the main pipe. The spring 3 connects the baffle 2 and the sphere 4. The limiting plate 5 is fixed to the outlet end of the rectifier chamber 1 via the support rod 6 to limit the displacement range of the sphere 4. The spring 3 and the sphere 4 work together to achieve adaptive adjustment of the flow area with the flow velocity, thereby suppressing flow oscillations during the transition from single-phase to two-phase flow. This invention reduces the peak value of natural circulation flow fluctuations and provides system operational stability when single-phase to two-phase transition conditions such as boiling flash occur in natural circulation flow.

Description

Technical Field

[0001] This invention belongs to the field of nuclear power safety technology, and specifically relates to an adaptive resistance regulation device and method for suppressing natural circulation flow oscillations. Background Technology

[0002] Passive natural circulation systems are maturely applied in containment heat dissipation systems. These systems primarily consist of an elevated water tank and heat exchangers within the containment. They transfer heat from the containment to an external cooling water tank via natural circulation to prevent containment overpressure. Natural circulation systems often exhibit flow instability during the single-phase to two-phase transition, mainly due to a mismatch between the natural circulation driving force and flow resistance, as well as low driving head. This instability can lead to system performance degradation and mechanical fatigue damage, thereby affecting the safety of nuclear facilities.

[0003] The AP1000 containment cooling system enhances the stability of the natural circulation system through a combination of airflow channels and condensate film design. Some designs incorporate a throttling valve at the steam generator outlet to limit the migration speed of vapor bubbles in the two-phase flow. While this can suppress instability in the two-phase natural circulation flow, it cannot adaptively adjust to the driving head of the natural circulation.

[0004] Therefore, how to provide an adaptive resistance adjustment device and method to suppress natural circulation flow oscillations, reduce the peak value of natural circulation flow fluctuations and provide system operation stability when natural circulation flow undergoes single-phase to two-phase transition conditions such as boiling flash evaporation, has become an urgent technical problem to be solved. Summary of the Invention

[0005] This invention provides an adaptive resistance adjustment device and method for suppressing natural circulation flow oscillations. When natural circulation flow undergoes single-phase to two-phase transition conditions such as boiling flash evaporation, it reduces the peak value of natural circulation flow fluctuations and provides system operational stability.

[0006] In this embodiment of the invention, an adaptive resistance adjustment device for suppressing natural circulation flow oscillations is provided, which is installed on the descending section pipe of a natural circulation system. The adjustment device includes: a rectifier chamber 1, a baffle 2, a spring 3, a ball 4, a limiting plate 5, and a support rod 6.

[0007] The size of rectifier chamber 1 is larger than the size of the pipe in the natural circulation descent section;

[0008] The baffle 2 is welded to the inner wall of the rectifier chamber 1, and the flow area of ​​the rectifier chamber 1 is not less than the flow area of ​​the main pipeline.

[0009] Spring 3 connects baffle 2 and ball 4;

[0010] The limiting plate 5 is fixed to the outlet end of the rectifier chamber 1 by the support rod 6, and is used to limit the displacement range of the ball 4;

[0011] The spring 3 and the ball 4 work together to achieve adaptive adjustment of the flow area with the flow velocity, so as to suppress the flow oscillation under the single-phase to two-phase transition condition.

[0012] Furthermore, the cross-sectional area of ​​the rectifier chamber 1 is 1.2 to 2.5 times that of the cross-sectional area of ​​the descending section pipe.

[0013] Furthermore, the baffle 2 is an annular structure, and its inner diameter is consistent with the inner diameter of the descending section pipe.

[0014] Furthermore, the sphere 4 is made of corrosion-resistant and high-temperature-resistant stainless steel, and its diameter is larger than the outlet diameter of the rectifier chamber 1 and smaller than the inner diameter of the rectifier chamber 1.

[0015] Furthermore, spring 3 is a pre-compressed helical spring, and its stiffness coefficient satisfies:

[0016] When the flow velocity is ≤0.5m / s, the spring tension of spring 3 makes the distance between ball 4 and limiting plate 5 ≥50% of the outlet diameter of rectifier chamber 1;

[0017] When the flow velocity is ≥2m / s, the spring tension of spring 3 ensures that the distance between ball 4 and limiting plate 5 is ≤20% of the outlet diameter of rectifier chamber 1.

[0018] Furthermore, the limiting plate 5 is a circular plate structure with a central through hole, the diameter of which is 60% to 80% of the outlet diameter of the rectifier chamber 1.

[0019] Furthermore, the support rod 6 is a structure of 3 to 6 radially distributed reinforcing ribs. One end of the support rod 6 is welded to the inner wall of the rectifier chamber 1, and the other end is connected to the limiting plate 5.

[0020] In another embodiment of the present invention, an adaptive resistance adjustment method for suppressing natural circulation flow oscillations, based on any one of the above-mentioned adaptive resistance adjustment devices for suppressing natural circulation flow oscillations, includes:

[0021] Under low flow rate conditions, the fluid passes through the large flow area between the sphere 4 and the limiting plate 5, and the device resistance coefficient is ≤0.3;

[0022] Under high flow rate conditions, a negative pressure zone is formed below the sphere 4, generating an upward pressure difference. The spring 3 is stretched, reducing the flow area and increasing the device resistance coefficient to 1.5-3.0.

[0023] Furthermore, the triggering conditions for high flow rate conditions include:

[0024] When transitioning from single-phase to two-phase, the peak flow fluctuation is ≥150% of the rated flow, or the instantaneous increase in driving head is ≥50%.

[0025] The beneficial effects of this invention are as follows:

[0026] As can be seen from the above scheme, the embodiments of the present invention provide an adaptive resistance adjustment device and method for suppressing natural circulation flow oscillations. Installed on the descending section of the pipe in a natural circulation system, the adjustment device includes: a rectifier chamber 1, a baffle 2, a spring 3, a sphere 4, a limiting plate 5, and a support rod 6. The size of the rectifier chamber 1 is larger than the size of the descending section of the natural circulation pipe. The baffle 2 is welded to the inner wall of the rectifier chamber 1, and the flow area of ​​the rectifier chamber 1 is not less than the flow area of ​​the main pipe. The spring 3 connects the baffle 2 and the sphere 4. The limiting plate 5 is fixed to the outlet end of the rectifier chamber 1 via the support rod 6 to limit the displacement range of the sphere 4. The spring 3 and the sphere 4 work together to achieve adaptive adjustment of the flow area with the flow velocity, thereby suppressing flow oscillations under single-phase to two-phase transition conditions. This invention reduces the peak value of natural circulation flow fluctuations and provides system operational stability when single-phase to two-phase transition conditions such as boiling flash occur in natural circulation flow. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of an adaptive resistance adjustment device for suppressing natural circulating flow oscillations according to an embodiment of the present invention;

[0028] In the diagram, 1 is the rectifier chamber, 2 is the baffle, 3 is the spring, 4 is the sphere, 5 is the limiting plate, and 6 is the support rod. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0030] like Figure 1 As shown, Figure 1 This is a schematic diagram of an adaptive resistance adjustment device for suppressing natural circulating flow oscillations according to an embodiment of the present invention.

[0031] Figure 1 An adaptive resistance regulating device for suppressing natural circulation flow oscillations is installed on the descending section pipe of a natural circulation system. The regulating device includes: a rectifier chamber 1, a baffle 2, a spring 3, a ball 4, a limiting plate 5, and a support rod 6.

[0032] The size of rectifier chamber 1 is larger than the size of the pipe in the natural circulation descent section;

[0033] The baffle 2 is welded to the inner wall of the rectifier chamber 1, and the flow area of ​​the rectifier chamber 1 is not less than the flow area of ​​the main pipeline.

[0034] Spring 3 connects baffle 2 and ball 4;

[0035] The limiting plate 5 is fixed to the outlet end of the rectifier chamber 1 by the support rod 6, and is used to limit the displacement range of the ball 4;

[0036] The spring 3 and the ball 4 work together to achieve adaptive adjustment of the flow area with the flow velocity, so as to suppress the flow oscillation under the single-phase to two-phase transition condition.

[0037] In this embodiment of the invention, an adaptive resistance regulating device for suppressing natural circulation flow oscillations significantly increases the natural circulation driving force and rapidly increases the system flow rate during the transition from single-phase to two-phase processes such as boiling flash in a natural circulation system. The technical solution of this invention features a rapid change in flow resistance with flow rate, which can suppress the instability of natural circulation flow.

[0038] When conditions such as boiling flash occur, which are conditions that transition from a single phase to a two phase, the natural circulation driving force increases significantly, the fluid velocity increases rapidly, the flow area of ​​the device decreases, and the flow resistance increases accordingly, thereby reducing the peak flow fluctuation and further improving the system's operational stability.

[0039] In this embodiment of the invention, an adaptive resistance regulating device for suppressing natural circulation flow oscillations is characterized by a rapid change in flow resistance with flow rate. This function is achieved using a spring 3 and a ball 4.

[0040] Under low flow rate conditions, the spring 3 experiences less tension from the baffle, resulting in a smaller spring tension and a larger fluid flow area, thus reducing the flow resistance of the resistance regulating device.

[0041] Under high flow rate conditions, fluid enters the outlet section from both sides of sphere 4, increasing the flow velocity. According to Bernoulli's principle, the pressure at the bottom of sphere 4 decreases, creating a pressure difference between its upper and lower surfaces. This pressure difference increases the spring tension and reduces the flow area. Since the local pressure drop of the resistance device is proportional to the square of the flow velocity, the reduced flow area and increased flow velocity lead to a sharp increase in flow resistance.

[0042] In one embodiment of the present invention, the cross-sectional area of ​​the rectifier chamber 1 is 1.2 to 2.5 times the cross-sectional area of ​​the descending section pipe.

[0043] It is understood that in some embodiments of the present invention, the cross-sectional area of ​​the rectifier chamber 1 is adjusted according to the cross-sectional area of ​​the descending section pipe, and the specific value is not specifically limited here.

[0044] In one embodiment of the present invention, the baffle 2 is an annular structure, and its inner diameter is consistent with the inner diameter of the descending section pipe.

[0045] In one embodiment of the present invention, the sphere 4 is made of corrosion-resistant and high-temperature-resistant stainless steel, and its diameter is larger than the outlet diameter of the rectifier chamber 1 and smaller than the inner diameter of the rectifier chamber 1.

[0046] In one embodiment of the present invention, spring 3 is a pre-compressed helical spring, and its stiffness coefficient satisfies:

[0047] When the flow velocity is ≤0.5m / s, the spring tension of spring 3 makes the distance between ball 4 and limiting plate 5 ≥50% of the outlet diameter of rectifier chamber 1;

[0048] When the flow velocity is ≥2m / s, the spring tension of spring 3 ensures that the distance between ball 4 and limiting plate 5 is ≤20% of the outlet diameter of rectifier chamber 1.

[0049] In this embodiment of the invention, to prevent flow stagnation, a limiting plate 5 is provided to prevent the sphere 4 from blocking the outlet. Under low flow rate conditions, the spring 3 experiences less tension from the baffle 2, resulting in a smaller spring tension and a larger distance between the sphere 4 and the limiting plate 6. Consequently, the fluid flow area is larger, and the flow resistance of this resistance device is lower. Under high flow rate conditions, the fluid enters the outlet section from both sides of the sphere 4, increasing the flow velocity. According to Bernoulli's principle, the pressure at the bottom of the sphere 4 decreases, creating a pressure difference between its upper and lower surfaces. Under the influence of this pressure difference, the tension of the spring 3 increases, the distance between the sphere 4 and the limiting plate 6 decreases, and thus the fluid flow area decreases.

[0050] Since the local pressure drop of the resistance device is proportional to the square of the flow velocity, a decrease in the flow area leads to an increase in flow velocity and a sharp increase in flow resistance, thereby reducing the peak flow fluctuation. To prevent flow stagnation, a limiting plate 5 is installed to restrict the sphere 4 from blocking the outlet. The support rod 6 serves to fix the limiting plate 5 and increase its strength.

[0051] In one embodiment of the present invention, the limiting plate 5 is a circular plate structure with a central through hole, the diameter of which is 60% to 80% of the outlet diameter of the rectifier chamber 1.

[0052] In one embodiment of the present invention, the support rod 6 is a structure of 3 to 6 radially distributed reinforcing ribs, one end of the support rod 6 is welded to the inner wall of the rectifier chamber 1, and the other end is connected to the limiting plate 5.

[0053] In another embodiment of the present invention, an adaptive resistance adjustment method for suppressing natural circulation flow oscillations, based on any one of the above-mentioned adaptive resistance adjustment devices for suppressing natural circulation flow oscillations, includes:

[0054] Under low flow rate conditions, the fluid passes through the large flow area between the sphere 4 and the limiting plate 5, and the device resistance coefficient is ≤0.3;

[0055] Under high flow rate conditions, a negative pressure zone is formed below the sphere 4, generating an upward pressure difference. The spring 3 is stretched, reducing the flow area and increasing the device resistance coefficient to 1.5-3.0.

[0056] In one embodiment of the present invention, the high flow rate triggering condition includes:

[0057] When transitioning from single-phase to two-phase, the peak flow fluctuation is ≥150% of the rated flow, or the instantaneous increase in driving head is ≥50%.

[0058] This invention provides an adaptive resistance adjustment device and method for suppressing natural circulation flow oscillations. The device is installed on the descending section of a natural circulation system pipe. The adjustment device includes: a rectifier chamber 1, a baffle 2, a spring 3, a sphere 4, a limiting plate 5, and a support rod 6. The size of the rectifier chamber 1 is larger than the size of the descending section of the natural circulation pipe. The baffle 2 is welded to the inner wall of the rectifier chamber 1, and the flow area of ​​the rectifier chamber 1 is not less than the flow area of ​​the main pipe. The spring 3 connects the baffle 2 and the sphere 4. The limiting plate 5 is fixed to the outlet end of the rectifier chamber 1 via the support rod 6 to limit the displacement range of the sphere 4. The spring 3 and the sphere 4 work together to achieve adaptive adjustment of the flow area with the flow velocity, thereby suppressing flow oscillations during the transition from single-phase to two-phase operation.

[0059] The technical solution of this invention is used to reduce the peak value of natural circulation flow fluctuation and provide system operation stability when boiling flash evaporation and other single-phase to two-phase transition conditions occur in natural circulation flow.

[0060] The above are preferred embodiments of the present invention. It should be noted that, for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. An adaptive resistance adjustment device for suppressing natural circulating flow oscillations, characterized in that, The regulating device, installed on the descending section pipe of the natural circulation system, includes: a rectifier chamber (1), a baffle (2), a spring (3), a ball (4), a limiting plate (5), and a support rod (6); The size of the rectifier chamber (1) is larger than the size of the pipe in the natural circulation descent section; The baffle (2) is welded to the inner wall of the rectifier chamber (1), and the flow area of ​​the rectifier chamber (1) is not less than the flow area of ​​the main pipeline; The spring (3) connects the baffle (2) and the ball (4); The limiting plate (5) is fixed to the outlet end of the rectifier chamber (1) by the support rod (6) to limit the displacement range of the sphere (4); The spring (3) and the sphere (4) work together to achieve adaptive adjustment of the flow area with the flow velocity, so as to suppress the flow oscillation under the single-phase to two-phase transition condition.

2. The adaptive resistance adjustment device for suppressing natural circulation flow oscillations according to claim 1, characterized in that, The cross-sectional area of ​​the rectifier chamber (1) is 1.2 to 2.5 times that of the cross-sectional area of ​​the descending section pipe.

3. The adaptive resistance adjustment device for suppressing natural circulating flow oscillations according to claim 1, characterized in that, The baffle (2) is an annular structure, and its inner diameter is consistent with the inner diameter of the descending section pipe.

4. The adaptive resistance adjustment device for suppressing natural circulation flow oscillations according to claim 1, characterized in that, The sphere (4) is made of corrosion-resistant and high-temperature resistant stainless steel. Its diameter is larger than the outlet diameter of the rectifier chamber (1) and smaller than the inner diameter of the rectifier chamber (1).

5. The adaptive resistance adjustment device for suppressing natural circulation flow oscillations according to claim 1, characterized in that, The spring (3) is a pre-compressed helical spring, and its stiffness coefficient satisfies: When the flow velocity is ≤0.5m / s, the spring tension of the spring (3) makes the distance between the ball (4) and the limiting plate (5) ≥50% of the outlet diameter of the rectifier chamber (1); When the flow velocity is ≥2m / s, the spring tension of the spring (3) makes the distance between the ball (4) and the limiting plate (5) ≤20% of the outlet diameter of the rectifier chamber (1).

6. The adaptive resistance adjustment device for suppressing natural circulation flow oscillations according to claim 1, characterized in that, The limiting plate (5) is a circular plate structure with a central through hole, the diameter of which is 60% to 80% of the outlet diameter of the rectifier chamber (1).

7. The adaptive resistance adjustment device for suppressing natural circulation flow oscillations according to claim 1, characterized in that, The support rod (6) is a structure of 3 to 6 radially distributed reinforcing ribs. One end of the support rod (6) is welded to the inner wall of the rectifier chamber (1), and the other end is connected to the limiting plate (5).

8. An adaptive resistance adjustment method for suppressing natural circulation flow oscillations, based on an adaptive resistance adjustment device for suppressing natural circulation flow oscillations as described in any one of claims 1 to 7, characterized in that, The method includes: Under low flow rate conditions, the fluid passes through the large flow area between the sphere (4) and the limiting plate (5), and the device resistance coefficient is ≤0.3; Under high flow rate conditions, a negative pressure zone is formed below the sphere (4), generating an upward pressure difference. The spring (3) is stretched, reducing the flow area and increasing the device resistance coefficient to 1.5 to 3.

0.

9. The adaptive resistance adjustment method for suppressing natural circulating flow oscillations according to claim 8, characterized in that, The high-flow-rate triggering conditions include: When transitioning from single-phase to two-phase, the peak flow fluctuation is ≥150% of the rated flow, or the instantaneous increase in driving head is ≥50%.

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