Plug assembly and plug using the same

Abstract

The present disclosure provides a plug assembly and a plug using the same. It is used to solve the problem of unstable constant flow caused by gap leakage between the valve core and the main body of the existing orifice constant flow plug. It is characterized in that: this plug includes a salvage head, an upper cover, a sealing ring, an upper main body, a spring, a connecting sleeve, a lower main body, a main spring, a constant flow plug, a baffle, a gear, a downward closer and a filter; the first-level throttling injection water flows through the gap between the constant flow plug and the lower main body, and the gap liquid flow between the constant flow plug and the lower main body decreases as the constant flow plug moves upward, and the downward closer moves upward with the constant flow plug to close the outlet opening, which is equivalent to changing the first-level throttling nozzle area during constant flow, so as to better correspond to the spring stiffness. This plug solves the problem of gap leakage between the valve core and the main body of the constant flow plug under different pressure conditions by gap liquid flow, and solves the problem of irregular force changes on the valve core under different displacements by changing the matching gap area.

Description

Technical Field

[0001] The content disclosed in this article relates to a downhole tool used in the field of oil and gas field development, specifically, it relates to a downhole constant flow water injection plug. Background Art

[0002] The constant flow plug is an important component of the stratified water injection technology. When a stable constant flow water injection is required in the well, the constant flow plug is used in conjunction with the eccentric water distributor to inject constant flow water into the well. At present, the constant flow plug is mainly an orifice throttling constant flow plug, but the orifice throttling constant flow plug has the following technical problems, resulting in a certain error in the constant flow rate. Taking CN 108590606A as an example, its main disadvantages are three points: when the flow rate is constant, the valve core will have a certain amount of displacement under different pressure conditions, but during the displacement process, the force change of the valve core is not linear, that is, the fixed first-level throttling area cannot meet the constant flow demand, and there will be a certain deviation; there is a certain gap between the valve core and the plug body, which is constant at 10m 3 / d-30m 3 / d flow rate, there will be a lot of gap leakage when the injection pressure changes, resulting in a large constant flow error. The leakage will increase with the increase of pressure, which is not conducive to achieving the constant flow purpose; the valve core will suffer eccentric wear under the action of water pressure and spring elastic force, reducing the life of the valve core, and when the injection pressure increases, the water pressure needs to overcome the spring elastic force and friction to move the valve core upward. When the injection pressure decreases, the spring elastic force needs to overcome the water pressure and friction to move the constant flow plug downward, which is not conducive to achieving the constant flow purpose. Summary of the invention

[0003] This specification provides a specific technical solution for a constant-current plug and gives several specific embodiments. The plug provided by these specific embodiments can solve the technical problems raised in the background technology and will not cause constant-current control errors caused by gap leakage.

[0004] One or more embodiments of this specification are implemented according to the following schemes:

[0005] First embodiment: A plug assembly, including a descending closer and a gear for closing a water outlet of the plug, is unique in that:

[0006] The main body of the descending closer is a hollow cylinder, a first rack is vertically fixed on one side of the hollow cylinder, and sliding grooves are arranged on both sides of the fixed position of the rack, and the sliding grooves do not penetrate the cylinder surface of the hollow cylinder in the vertical direction;

[0007] The gear has a gear shaft meshed with the first rack, and when the gear rotates clockwise, the first rack can move vertically downward.

[0008] Second embodiment: the plug assembly further includes a constant flow plug;

[0009] The constant flow plug comprises a second positioning connector, a variable cross-section cylinder and a second rack; the second positioning connector is a cross-shaped body, which is vertically fixed to the center of the variable cross-section cylinder; the second rack is vertically fixed to the outer wall of the positioning connector and can mesh with the gear;

[0010] The outer circle with the largest cross-sectional diameter of the variable-section cylinder appears in the middle section of the variable-section cylinder.

[0011] Further optimization scheme: the variable cross-section cylinder adopts any one of a horizontal plate structure, a straight chamfer structure or an elliptical arc structure, and the three structures have the same maximum cross-sectional diameter, and the distance between the maximum cross-sectional area and the bottom of the variable cross-sectional cylinder is also the same.

[0012] The third embodiment: The plug assembly also includes a baffle; the baffle includes a base plate and a first positioning connector, and the first positioning connector is fixed in the center of the base plate; the first positioning connector is a cross-shaped body with a cross-shaped hollow, and the internal size of the cross-shaped hollow is larger than the external size of the second positioning connector, so that the second positioning connector can be inserted into the first positioning connector.

[0013] Fourth embodiment: Based on the third embodiment, the following technical contents are added to obtain the following solution, which is constructed into a constant flow plug, specifically:

[0014] The plugger also includes a fishing head, an upper cover, a cam, an upper body, a first spring, a connecting sleeve, a lower body and a filter screen, and its unique features are:

[0015] Using the plug assembly constructed according to the third embodiment;

[0016] including a second spring;

[0017] The upper body is provided with a threaded surface, an inner cylindrical surface, a pin hole, a notched surface, an outer threaded surface and a lower bottom surface;

[0018] The threaded surface is used to cooperate with the upper cover to fix the two together; the inner cylindrical surface is used for the bottom of the fishing head to move up and down in the inner cylindrical surface when the plugging device is lowered and the plugging device is salvaged; the pin hole is used for the pin to pass through the cam and limit the displacement of the cam; the notch surface is used for the front end of the cam to extend and get stuck inside the water distributor to prevent the plugging device from slipping out of the water distributor during the constant flow process; the outer threaded surface is used to cooperate with the outer threaded surface of the connecting sleeve; the lower bottom surface is used to support the upper end surface of the second spring;

[0019] The lower body is provided with a water outlet, a first buffer step surface and a second buffer step surface; the arc radius of the arc surface of the first buffer step surface is a first set value, the upper part of the arc surface of the first buffer step surface is tangent to the straight line, and the lower part is tangent to the second buffer step surface; the arc radius of the arc surface of the second buffer step surface is a second set value, and the second set value is greater than the first set value; the upper part of the arc surface of the second buffer step surface is tangent to the arc surface of the first buffer step surface, and the lower part is tangent to the straight line;

[0020] The first buffer step surface and the second buffer step surface cooperate with the variable cross-section cylinder in the constant flow plug to achieve: when the constant flow plug moves up and down, the gap area between the constant flow plug and the buffer step surface changes;

[0021] The pin passes through the sliding groove of the descending closer and is riveted on the lower body, so as to limit the rotation of the descending closer and allow it to slide up and down; the descending closer is located in the lower body and is used to control the opening of the water outlet; the gear shaft of the descending closer is fixed in the inner cavity of the lower body, and after being fixed, the gear is respectively engaged with the first rack and the second rack, so that when the constant flow plug moves upward, the descending closer moves downward;

[0022] The second spring is arranged between the baffle and the upper body, and is used to press the constant flow plug;

[0023] The constant flow plug is located in the lower body, the upper cover is threadedly connected to the upper body, the salvage head passes through the first spring and is squeezed on the cam with the upper cover, and the lower body and the upper body are threadedly connected to the connecting sleeve at the same time; the filter is threadedly connected to the lower body, and the injected water enters the plug through the filter.

[0024] Further optimization based on the above basic solution:

[0025] Optimization solution 1: The upper body is provided with an inner "cross"-shaped hole, and the inner "cross"-shaped hole can cooperate with the first positioning connector of the baffle, so that the baffle cannot move left and right, and can only slide up and down.

[0026] Optimization solution 2:

[0027] The arc radius of the arc surface of the first buffer step surface in the lower body is a first set value, and the arc radius of the arc surface of the second buffer step surface is a second set value, and the second set value is greater than the first set value; the upper wall thickness of the lower body is a third set value, and the lower wall thickness is a fourth set value, and the third set value is greater than the fourth set value.

[0028] Optimization scheme 3: The maximum diameter of the cross-section circle of the variable-section cylinder in the constant flow plug and the stiffness of the second spring are calculated according to the following path: using the numerical simulation method, the internal fluid domain of the plug is calculated by Fluent software, and after extracting the overall force of the constant flow plug, the spring stiffness of the second spring is matched; after matching, the plug maintains a constant flow rate.

[0029] At least one of the above technical solutions adopted in one or more embodiments of this specification can achieve the following beneficial effects: the injected water enters the plug through the filter screen, flows out from the outlet of the lower body through the gap between the constant flow plug and the lower body, and all the injected water of this constant flow plug is gap liquid, and there is no leakage problem. By calculating and matching the appropriate spring stiffness, when the injection pressure increases, the constant flow plug moves up, the liquid gap area between the constant flow plug and the lower body decreases, the lower closure moves down, the outlet area decreases, and the flow rate is limited to increase, so as to achieve the purpose of constant flow. This constant flow plug is provided with an inner and outer double arc buffer structure on the inner surface of the lower body, which can achieve a better constant flow effect. In addition, the two-stage "cross" shape constructed in the upper and lower bodies prevents the constant flow plug from shaking in the lower body, which can extend the service life of the constant flow plug, and converts the friction between the constant flow plug and the lower body into the friction between the "cross" font and the "cross" groove, which reduces the friction and is conducive to achieving the purpose of constant flow. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the embodiments of this specification, the drawings required for use in the embodiments will be briefly introduced below: the drawings described below are only some of the embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0031] Figure 1 The schematic diagram of the buffer step structure of different inner surfaces of the lower body in the specific embodiment of the present disclosure shows that the buffer step can be designed as a double arc structure, a straight double chamfer structure and a double arc structure with different radii.

[0032] Figure 2 Schematic diagram of different external step structures of the constant current plug given in the specific embodiment of the present disclosure. The figure shows that the lower part of the constant current plug can be designed as a horizontal plate structure, a straight chamfer structure or an elliptical arc structure.

[0033] Figure 3 This is a structural diagram of the plug provided in a specific embodiment of the present disclosure.

[0034] Figure 4 It is a schematic diagram of the minimum gap of the plug given in the specific embodiment of the present disclosure. The minimum gap is the smallest area ring obtained by the cooperation between the thickest part of the elliptical arc surface of the constant flow plug and the buffer step surface of the lower body, and the injected water flows through this ring.

[0035] Figure 5 This is a three-dimensional structural parts drawing of the upper body given in a specific embodiment of the present disclosure.

[0036] Figure 6 It is a three-dimensional structural parts diagram of the connecting sleeve given in a specific embodiment of the present disclosure.

[0037] Figure 7 This is a three-dimensional structural parts diagram of the lower body provided in a specific embodiment of the present disclosure.

[0038] Figure 8 It is a three-dimensional structural parts drawing of the baffle provided in a specific embodiment of the present disclosure.

[0039] Fig. 9 It is a three-dimensional structural parts diagram of the downlink closer provided in a specific embodiment of the present disclosure.

[0040] Fig.10 This is a three-dimensional structural parts diagram of a constant flow plug provided in a specific embodiment of the present disclosure.

[0041] In the figure: 1-fishing head; 2-upper cover; 3-upper cover sealing ring; 4-first spring; 5-upper body, 501-upper body threaded surface, 502-upper body inner cylindrical surface, 503-pin hole, 504-notch surface, 505-inner "cross" hole, 506-upper body outer threaded surface, 507-upper body lower bottom surface; 6-cam; 7-connecting sleeve, 701-connecting sleeve first inner threaded surface, 702-connecting sleeve second outer threaded surface; 8-lower body, 801-lower body outer threaded surface, 802-water outlet, 803-first buffer step surface, 804-second buffer step surface, 805-lower body inner threaded surface; 9-second spring; 10-baffle, 1001 -first positioning connector, 1002-bottom plate, 1003-cross-shaped hollow; 11-downward closer, 1101-first rack, 1102-sliding groove, 1103-hollow cylinder; 12-gear; 13-gear shaft; 14-constant flow plug, 1401-second positioning connector, 1402-second rack, 1403-variable cross-section cylinder, 1404-lower bottom surface of variable cross-section cylinder; 15-pin; 16-filter. DETAILED DESCRIPTION

[0042] The technical solution provided in the present disclosure is further described below in conjunction with the accompanying drawings:

[0043] Depend on Figures 3 to 10 As shown, a constant flow plug is provided. Figure 3It can be seen that the plug includes a salvage head 1, an upper cover 2, an upper cover sealing ring 3, a first spring 4, an upper body 5, a cam 6, a connecting sleeve 7, a lower body 8, a second spring 9, a baffle 10, a downward closer 11, a gear 12, a gear shaft 13, a constant flow plug 14, a pin 15 and a filter 16.

[0044] The upper cover 2 is threadedly connected to the upper body 5, the fishing head 1 passes through the spring 4 and the upper cover 2 to be squeezed on the cam 7, the lower body 8 is threadedly connected to the upper body 5 and the connecting sleeve 7 at the same time, and there is a buffer step inside the lower body 8 that cooperates with the constant flow plug 14 to change the gap area that cooperates with the constant flow plug when the displacement is different, that is, to change the first-level throttling area. The pin 15 is riveted on the lower body to limit the rotation of the descending closer 11. The first rack of the descending closer can be meshed with the gear 12, and the gear shaft 13 passes through the gear 12 and is fixed on the lower body 8. The second rack on the constant flow plug 14 can be meshed with the gear 12 to change the upward displacement of the constant flow plug 14 into the downward displacement of the descending closer 11. The "cross" shaped body on the upper part of the constant flow plug 14 can be inserted into the baffle 10 to limit the rotation and left and right movement of the constant flow plug 14. The second spring 9 is between the baffle 10 and the upper body 5. Under the action of the spring force, the baffle 10 is pressed tightly against the constant flow plug 14. The "cross" shaped body on the upper part of the baffle 10 can be inserted into the upper body 5 to limit the rotation and left and right movement of the baffle 10. The filter screen 16 is threadedly connected to the lower body 8. The injected water enters the plug through the filter screen, passes through the gap between the constant flow plug and the lower body, and flows out from the outlet matched by the lower closing device and the lower body. When the injection pressure increases, the constant flow plug moves up, the gap area between the constant flow plug and the lower body decreases (that is, the first-level throttling area decreases), the lower closing device moves down, and the outlet area decreases (that is, the second-level throttling area decreases), limiting the increase in flow and achieving the purpose of constant flow.

[0045] As shown in the figure: the upper body has a threaded surface 501, an inner cylindrical surface 502, a pin hole 503, a notch surface 504, an inner "cross" hole 505, an outer threaded surface 506, and a lower bottom surface 507 in sequence. The threaded surface 501 cooperates with the upper cover to fix the two together. When the plug is lowered and the plug is salvaged, the bottom of the salvage head moves up and down in the inner cylindrical surface 502, which is convenient for salvage. The pin passes through the cam and limits the displacement of the cam. The pin passes through the pin hole and is welded to the upper body. The front end of the cam extends out of the notch surface 504 and is stuck inside the water distributor to prevent the plug from slipping out of the water distributor during the constant flow process. The inner "cross" hole 505 cooperates with the "cross" surface 801 of the baffle to limit the left and right movement of the baffle, and the baffle can only slide up and down. The outer threaded surface 506 cooperates with the outer threaded surface 701 of the connecting sleeve, and the upper end surface of the spring is pressed on the lower bottom surface 507 of the upper body.

[0046] The lower body mainly includes an external threaded surface 801, a water outlet 802, buffer step surfaces 803, 804 and an internal threaded surface 805, and the external threaded surface 801 cooperates with the internal threaded surface 702 of the connecting sleeve. The water outlet is 802. When the descending closer moves up and down, the exposed area of ​​the water outlet is different, that is, the secondary throttling area is different. Surfaces 803 and 804 are buffer step surfaces. The arc radius of the arc surface 803 is 12mm. The upper part is tangent to the straight line, and the lower part is tangent to the surface 804. The arc radius of the arc surface 804 is 16mm. The upper part is tangent to the arc surface 803, and the lower part is tangent to the straight line. The upper wall thickness of the lower body is 1.75mm, and the lower wall thickness is 1.5mm. The buffer step surface cooperates with the constant flow plug. When the constant flow plug moves up and down, the gap area between the constant flow plug and the buffer step surface changes, that is, the primary throttling area changes. The reason that the buffer step surface is arranged like this is that the injection water needs to expand the primary throttling area when the pressure is low pressure, so that the injection water flows out conveniently, and the primary throttling area is reduced when the pressure is high, and the flow rate of the injection water is reduced. When the injection pressure is within 1MPa, the primary throttling area does not need to change too much, so that the water flows out conveniently, so the arc surface 804 is set to the inscribed state, so that the primary throttling area is reduced when the constant flow plug moves up, and the face that cooperates with the thickest part of the constant flow plug elliptical arc surface 1403 is the bottom of the arc surface 804. When the injection pressure is 1-5MPa, the primary throttling area is correspondingly reduced, so as to achieve the constant flow purpose, and the face that cooperates with the thickest part of the constant flow plug elliptical arc surface 1403 is the bottom of the arc surface 803 and the top of the arc surface 804. The minimum gap is the annular ring of the minimum area obtained by the thickest part of the constant flow plug elliptical arc surface 1403 and the lower main body buffer step surface 803, and the injection water flows through from this ring. When the constant flow plug moves up and down, the minimum gap area between the constant flow plug and the buffer step surface changes, the position and area of ​​this ring change, and the first-level throttling area changes.

[0047] When the injection pressure is above 5MPa, the primary throttling effect is weakened, and the plug mainly relies on the secondary throttling to keep the flow constant. Therefore, the arc surface 803 is set to an external tangent state, so that the primary throttling area decreases at a lower speed when the constant flow plug moves upward. At this time, the surface that matches the thickest part of the elliptical arc surface 1403 of the constant flow plug is the upper part of the arc surface 803. At the same time, the buffer surface can reduce the erosion of the injected water on the inner wall of the lower body through the three-segment tangent relationship. The internal thread surface 705 matches the filter screen.

[0048] like Figure 1As shown, the buffer step can be designed as a double arc structure, a straight double chamfer structure and a double arc structure with different radii. Regardless of the structure, the wall thickness of the upper part of the lower body and the wall thickness of the lower part of the lower body remain consistent, and there are no protruding corners, and the dividing line between the upper and lower parts of the lower body remains consistent. When the injection pressure increases, the constant flow plug of the plug moves up, and the matching gap between the plug and the lower body decreases, reducing the influence of pressure on the flow rate, and finally reaching a dynamic balance in the pressure fluctuation to achieve the purpose of constant flow. When the injection pressure decreases, the constant flow plug of the plug moves down, and the matching gap between the plug and the lower body increases, reducing the influence of pressure on the flow rate, and finally reaching a dynamic balance in the pressure fluctuation to achieve the purpose of constant flow. By changing the wall thickness of the upper and lower parts of the lower body, the constant flow of the plug assembly and the plug used therein can be changed to adapt to different constant flow requirements.

[0049] The baffle has a "cross" shaped surface 1001, a round table 1002, and an inner "cross" shaped hole 1003, wherein the "cross" shaped surface 1001 matches with the "cross" shaped hole in the upper body, and the lower end surface of the spring is pressed on the round table 1002, pressing the baffle tightly against the constant flow plug. The inner "cross" shaped hole 1003 matches with the "cross" shaped surface 1401 of the constant flow plug, limiting the constant flow plug from moving left and right, and can only move up and down.

[0050] The down closer has a rack 1101, a notch surface 1102, and a bottom surface 1103. The rack 1101 meshes with the gear, converting the upward movement of the constant flow plug into the downward movement of the down closer. The pin is inserted into the notch surface 1102, so that the down closer can only move up and down but cannot rotate. The down closer cooperates with the water outlet 802 of the lower body. When the down closer moves, the secondary throttling area is changed.

[0051] The constant flow plug has a "cross" shaped surface 1401, a rack 1402, an elliptical arc surface 1403, and a lower bottom surface 1404. The "cross" shaped surface 1401 cooperates with the "cross" shaped surface in the baffle, so that the constant flow plug can only move up and down, but cannot rotate. The rack 1402 is meshed with the gear, so that the constant flow plug and the downward closer are displaced in opposite directions. The thickest part of the elliptical arc surface 1403 cooperates with the buffer step surface 803 of the lower body. When the constant flow plug moves up and down, the gap area between the constant flow plug and the buffer step surface changes, that is, the primary throttling area changes. The lower bottom surface 1404 presses on the filter screen.

[0052] The maximum diameter of the cross-section circle of the variable cross-section cylinder in the constant flow plug and the stiffness of the second spring are matched according to the following path: using the numerical simulation method, the internal fluid domain of the plug is calculated by Fluent software, and the overall force of the constant flow plug is extracted, and then the spring stiffness of the second spring is matched; after matching, the plug maintains a constant flow rate. The specific process is as follows:

[0053] The maximum diameter of the elliptical arc section circle is 17.8mm. The maximum diameter of the elliptical arc section circle and the spring stiffness of the constant flow plug are obtained by numerical simulation method. The internal fluid domain of the plug is calculated by Fluent19.0 software, the overall force of the constant flow plug is extracted, and the appropriate spring stiffness is matched.

[0054] Design 30m 3 / d flow plug as an example, the internal flow field conditions of the constant flow plug at different positions of 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, 5mm, and 5.5mm and the stress conditions of each surface of the valve core are analyzed using the numerical simulation method of Fluent19.0 software to find out the change law of the overall force at different displacements of the constant flow plug. It was extracted that the displacement of the constant flow plug under the injection pressure of 1.5-6MPa is 3.5-5.5mm, but the force difference of the 3.5-4.5mm constant flow plug is 1.65N, and the force difference of the 4.5mm-5.5mm constant flow plug is 4.1N. Therefore, the wall thickness of the lower body of the plug is changed, and the numerical simulation is performed again using Fluent19.0 software, so that the overall force increases or decreases uniformly when the displacement of the constant flow plug is different, so as to achieve the purpose of selecting the appropriate spring stiffness. Finally, for 30m 3 / d flow rate, a spring stiffness of 3.2N / mm was selected.

[0055] This plug assembly and the plug used therein can only maintain a constant flow rate. When the constant flow rate needs to be changed, the maximum diameter of the elliptical arc section circle of the constant flow plug, the thickness of the inner wall of the lower body and the spring stiffness need to be changed.

[0056] like Figure 2 As shown, the lower part of the constant flow plug can be designed as a horizontal plate structure, a straight line guide angle structure, or an elliptical arc structure. Regardless of the structure, the diameter of the thickest cross-section circle of the constant flow plug remains consistent, and the distance from the bottom is also consistent. When the injection pressure increases, the constant flow plug of the plug moves upward, and the matching gap between the thickest cross-section circle and the lower body decreases, reducing the impact of pressure on flow, and ultimately achieving dynamic balance in pressure fluctuations to achieve the purpose of constant flow, and vice versa.

[0057] The constant flow principle of the constant flow plug in the prior art is that the elastic force of the spring is balanced with the fluid pressure on the valve core to achieve constant flow. However, the valve core will have a certain amount of displacement under different pressure conditions. However, during the displacement process, the force change on the valve core is not linear, and there will be a certain deviation in the constant flow. The plug provided in the present disclosure achieves the purpose of constant flow by changing the gap area between the constant flow plug and the lower main body and the outlet area between the downward closer and the lower main body when the constant flow plug is displaced differently, that is, by changing the primary throttling area and the secondary throttling area at the same time, thereby reducing the constant flow error; there is a certain gap between the valve core and the main body of the orifice throttling constant flow plug, and there will be leakage in the gap when the injection pressure changes. The leakage amount increases with the increase of pressure, which is not conducive to achieving the purpose of constant flow. The water injected into this plug is all liquid passing through the gap, and there is no leakage problem; the constant flow plug of the orifice throttling constant flow plug has no displacement restriction, and eccentric wear will occur under the action of water pressure and spring elastic force, which reduces the life of the plug. When the injection pressure increases, the water pressure needs to overcome the spring elastic force and friction to make the constant flow plug move upward. When the injection pressure decreases, the spring elastic force needs to overcome the water pressure and friction to make the constant flow plug move downward, which is not conducive to achieving the purpose of constant flow. This plug uses two-stage "cross" coordination to prevent the constant flow plug from shaking in the lower body, extending the service life of the constant flow plug, and converting the friction between the constant flow plug and the lower body into the friction between the "cross" font and the "cross" groove, reducing friction and facilitating the realization of constant flow.

[0058] To sum up, the solution provided in the present invention adopts the gap cooperation between the lower main body and the constant flow plug to replace the water nozzle of the orifice throttling constant flow plug, and achieves the constant flow purpose by changing the primary throttling area and the secondary throttling area at the same time. The liquid flow mode is changed to gap liquid flow to reduce leakage and prevent eccentric wear of the constant flow plug, which can save costs, realize stable constant flow water injection underground, and effectively improve oil recovery rate.

Claims

1. A plug assembly, comprising a descending closer, a gear and a constant flow plug for closing a water outlet of the plug; the main body of the descending closer is a hollow cylinder, a first rack is vertically fixed to one side of the hollow cylinder, sliding grooves are arranged on both sides of the fixed position of the first rack, and the sliding grooves do not penetrate the cylinder surface of the hollow cylinder in the vertical direction; The gear has a gear shaft meshing with the first rack, and the gear can make the first rack move vertically downward when rotating clockwise; The constant flow plug comprises a second positioning connection piece, a variable cross-section cylinder and a second rack; the second positioning connection piece is a cross-shaped body, which is vertically fixed to the center position of the variable cross-section cylinder; the second rack is vertically fixed to the outer wall of the second positioning connection piece and can mesh with the gear; The outer circle with the largest cross-sectional diameter of the variable-section cylinder appears in the middle section of the variable-section cylinder; Features: The variable cross-section cylinder adopts any one of a horizontal plate structure, a straight chamfer structure or an elliptical arc structure. The three structures have the same maximum cross-sectional diameter, and the distance between the maximum cross-sectional area and the bottom of the variable cross-sectional cylinder is also the same.

2. A plug assembly according to claim 1, characterized in that: The component also includes a baffle; the baffle includes a base plate and a first positioning connector, the first positioning connector is fixed in the center of the base plate; the first positioning connector is a cross-shaped body with a cross-shaped hollow, the internal size of the cross-shaped hollow is larger than the external size of the second positioning connector, so that the second positioning connector can be inserted into the first positioning connector.

3. A plugging device, comprising a fishing head, an upper cover, a cam, an upper body, a first spring, a connecting sleeve, a lower body and a filter screen, characterized in that: The plug assembly comprising claim 2; The plugger also includes a second spring; The upper body is provided with a threaded surface, an inner cylindrical surface, a pin hole, a notched surface, an outer threaded surface and a lower bottom surface; The threaded surface is used to cooperate with the upper cover to fix the two together; the inner cylindrical surface is used for the bottom of the fishing head to move up and down in the inner cylindrical surface when the plugging device is lowered and the plugging device is salvaged; the pin hole is used for the pin to pass through the cam and limit the displacement of the cam; the notch surface is used for the front end of the cam to extend and get stuck inside the water distributor to prevent the plugging device from slipping out of the water distributor during the constant flow process; the outer threaded surface is used to cooperate with the outer threaded surface of the connecting sleeve; the lower bottom surface is used to support the upper end surface of the second spring; The lower body is provided with a water outlet, a first buffer step surface and a second buffer step surface; the arc radius of the arc surface of the first buffer step surface is a first set value, the upper part of the arc surface of the first buffer step surface is tangent to the straight line, and the lower part is tangent to the second buffer step surface; the arc radius of the arc surface of the second buffer step surface is a second set value, and the second set value is greater than the first set value; the upper part of the arc surface of the second buffer step surface is tangent to the arc surface of the first buffer step surface, and the lower part is tangent to the straight line; The first buffer step surface and the second buffer step surface cooperate with the variable cross-section cylinder in the constant flow plug to achieve: when the constant flow plug moves up and down, the gap area between the constant flow plug and the first buffer step surface and the second buffer step surface changes; The pin passes through the sliding groove of the descending closer and is riveted on the lower body, so as to limit the rotation of the descending closer and allow it to slide up and down; the descending closer is located in the lower body and is used to control the opening of the water outlet; the gear shaft of the gear is fixed in the inner cavity of the lower body, and after being fixed, the gear is respectively meshed with the first rack and the second rack, so that when the constant flow plug moves upward, the descending closer moves downward; The second spring is arranged between the baffle and the upper body, and is used to press the constant flow plug; The constant flow plug is located in the lower body, the upper cover is threadedly connected to the upper body, the salvage head passes through the first spring and is squeezed on the cam with the upper cover, and the lower body and the upper body are threadedly connected to the connecting sleeve at the same time; the filter is threadedly connected to the lower body, and the injected water enters the plug through the filter.

4. A plugging device according to claim 3, characterized in that: The upper body is provided with an inner cross-shaped hole, and the inner cross-shaped hole can cooperate with the first positioning connector of the baffle, so that the baffle cannot move left and right, and can only slide up and down.

5. A plugging device according to claim 4, characterized in that: The upper wall thickness of the lower body is a third set value, and the lower wall thickness is a fourth set value, and the third set value is greater than the fourth set value.

6. The plugging device according to claim 5, characterized in that: The maximum diameter of the cross-section circle of the variable-section cylinder in the constant flow plug and the stiffness of the second spring are obtained according to the following path: using the numerical simulation method, the internal fluid domain of the plug is calculated through the Fluent software, and after the overall force of the constant flow plug is extracted, the spring stiffness of the second spring is matched; after matching, the plug maintains a constant flow rate.

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