Air inlet structure

Abstract

The air inlet structure comprises an air inlet channel and an anti-backfire device, and the inner wall of the air inlet channel is of a cambered surface structure; the anti-backfire device comprises a blade and a driving assembly, the blade is arranged at one end of the air inlet channel and is of an arc-shaped structure, and the driving assembly is connected with the blade and is configured as follows: in a normal state, the driving assembly drives the blade to open; when tempering occurs, the driving assembly drives the blades to be closed so as to prevent tempering gas from entering the gas inlet channel. According to the anti-backfire device, the gas inlet channel of a cambered surface structure is combined with the arc-shaped blades of the anti-backfire device, so that gas flows in an accelerated mode when passing through the gas inlet channel, the tumble effect is further enhanced by the arc-shaped blades in the gas flowing process, and therefore the uniformity and flowability of mixed gas are remarkably improved; meanwhile, when tempering occurs, the driving assembly pushes the blades to be closed, reverse flowing of tempering gas is effectively blocked, stable operation of the gas inlet system is ensured, and then the combustion efficiency and power output of the engine are improved.

Description

Technical Field

[0001] This application relates to the field of engines, and in particular to an intake structure. Background Technology

[0002] Currently, natural gas engines on the market are getting larger and larger. Without changing the engine structure, the most direct way to increase engine power is to allow more fuel to participate in combustion. However, due to the characteristics of gaseous fuel combustion, during operation, natural gas engines and other gaseous fuel engines sometimes experience backfire when combustion is abnormal, causing the air-fuel mixture in the cylinder to return from the intake valve to the intake manifold. Backfire reduces the engine's intake air volume and power. Because backfire occurs at high temperatures, it can severely damage related components in the intake manifold. Currently, improving the power of existing gas-fuel engines and controlling the occurrence and frequency of backfire is a very challenging problem. Various manufacturers are trying different methods to increase engine power and reduce backfire, but many problems remain. Summary of the Invention

[0003] This application provides an intake structure that can solve the problems of reduced intake volume, power loss, and component damage caused by backfire in natural gas engines in related technologies.

[0004] This application provides an intake structure comprising: an intake duct and a backfire prevention device. The inner wall of the intake duct has an arc-shaped structure. The backfire prevention device includes blades and a drive assembly. The blades are disposed at one end of the intake duct and have an arc-shaped structure. The drive assembly is connected to the blades and configured such that: in a normal state, the drive assembly drives the blades to open; in the event of backfire, the drive assembly drives the blades to close, thereby preventing backfire gas from entering the intake duct. By combining the arc-shaped intake duct with the arc-shaped blades of the backfire prevention device, the gas achieves accelerated flow when passing through the intake duct. The arc-shaped blades further enhance the tumble effect during gas flow, thereby significantly improving the uniformity and flowability of the air-fuel mixture. Simultaneously, in the event of backfire, the drive assembly pushes the blades to close, effectively blocking the reverse flow of backfire gas, ensuring the stable operation of the intake system, and thus improving the engine's combustion efficiency and power output.

[0005] In conjunction with the first aspect, in one embodiment, the relationship between the outer cavity size, inner cavity size, and middle size of the air intake duct is as follows: the middle size is smaller than the inner cavity size, and the difference between the inner cavity size and the middle size is within a first set interval; the outer cavity size is larger than the inner cavity size, and the difference between the outer cavity size and the inner cavity size is within the first set interval, so that the inner wall of the air intake duct forms an arcuate structure, and the lower limit of the first set interval is greater than 1.

[0006] In conjunction with the first aspect, in one embodiment, the upper top surface and the lower bottom surface profile of the inner wall of the air intake are tangent.

[0007] In conjunction with the first aspect, in one embodiment, the space between the inner cavity and the middle portion of the air intake duct is a first inner wall, and the space between the outer cavity and the middle portion of the air intake duct is a second inner wall; The ratio of the radius to the central dimension of the first inner wall is within a second set range, and the ratio of the radius to the central dimension of the second inner wall is within a third set range. The lower limits of both the second and third set ranges are greater than 1.

[0008] In conjunction with the first aspect, in one embodiment, the ratio of the radius of curvature of the blade to the width of the blade is located within a fourth predetermined interval, wherein the lower limit of the fourth predetermined interval is greater than 1.

[0009] In conjunction with the first aspect, in one embodiment, the backfire prevention device further includes a frame disposed at one end of the air intake, and the blades are rotatably connected to the frame.

[0010] In conjunction with the first aspect, in one embodiment, the drive assembly includes: a drive motor assembly, a drive rod, and a connector. The drive rod is slidably connected to the frame, and one end is connected to the drive motor assembly. The connector is connected between the drive rod and the blade. The drive motor assembly drives the drive rod to move up and down, so that the connector drives the blade to open or close.

[0011] In conjunction with the first aspect, in one embodiment, the connecting member includes: a slide rod and a connecting rod, the slide rod being fixed to a drive rod; the connecting rod being fixed to one end of the blade, and the slide rod being slidably connected to a groove in the connecting rod.

[0012] In conjunction with the first aspect, in one embodiment, the drive rod has a through groove in the middle, the slide rod is disposed in the through groove, and the connecting rod passes through the through groove and is slidably connected to the slide rod.

[0013] In conjunction with the first aspect, in one embodiment, the air intake structure further includes a pressure sensor and a controller. The pressure sensor is used to detect and send a first pressure value at the air intake port of the air intake duct and a second pressure value inside the air intake duct. The controller is used to compare the received first pressure value and second pressure value with a set pressure value. When the first pressure value is greater than or equal to the set pressure value and the ratio of the set pressure value to the second pressure value is greater than or equal to a set threshold, the drive component drives the blades to close.

[0014] The beneficial effects of the technical solutions provided in this application include: This application provides an intake structure that combines an intake duct with an arc-shaped blade of a backfire prevention device. This allows the gas to flow more rapidly as it passes through the intake duct. The arc-shaped blade further enhances the tumble effect during gas flow, thereby significantly improving the uniformity and flowability of the air-fuel mixture. Simultaneously, when backfire occurs, the drive assembly pushes the blade to close, effectively blocking the reverse flow of backfire gas and ensuring the stable operation of the intake system. This, in turn, improves the engine's combustion efficiency and power output. Attached Figure Description

[0015] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the air intake structure provided in an embodiment of this application; Figure 2 A schematic diagram of the framework provided for an embodiment of this application; Figure 3 A schematic diagram of the backfire prevention device provided in the embodiments of this application; Figure 4 A schematic diagram of the backfire prevention device provided in the embodiments of this application; Figure 5 A schematic diagram of the backfire prevention device provided in the embodiments of this application; Figure 6 A schematic diagram of the blades and frame provided in an embodiment of this application; Figure 7 A schematic diagram of the drive rod, blade, and frame provided in an embodiment of this application; Figure 8 A schematic diagram of the connector provided in an embodiment of this application; Figure 9 A schematic diagram of the connector provided in an embodiment of this application; Figure 10 A schematic diagram of the drive rod provided in an embodiment of this application; Figure 11 A schematic diagram of the intake duct dimensions provided for an embodiment of this application; Figure 12 This is a schematic diagram of the blade provided in an embodiment of this application.

[0017] In the diagram: 1. Air intake; 2. Backfire prevention device; 21. Frame; 22. Limiting block; 23. Blade; 230. Connecting rod; 24. Drive rod; 240. Through slot; 241. Slide rod. Detailed Implementation

[0018] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0019] This application provides an intake structure that can solve the problems of reduced intake volume, power loss, and component damage caused by backfire in natural gas engines in related technologies.

[0020] Currently, natural gas engines on the market are getting larger and larger. Without changing the engine structure, the most direct way to increase engine power is to allow more fuel to participate in combustion. However, due to the characteristics of gaseous fuel combustion, during operation, natural gas engines and other gaseous fuel engines sometimes experience backfire when combustion is abnormal, causing the air-fuel mixture in the cylinder to return from the intake valve to the intake manifold. Backfire reduces the engine's intake air volume and power. Because backfire occurs at high temperatures, it can severely damage related components in the intake manifold. Currently, improving the power of existing gas-fuel engines and controlling the occurrence and frequency of backfire is a very challenging problem. Various manufacturers are trying different methods to increase engine power and reduce backfire, but many problems remain.

[0021] Therefore, see Figures 1-12 This application provides an air intake structure, which includes an air intake duct 1 and a backfire prevention device 2. The inner wall of the air intake duct 1 is an arc-shaped structure. The backfire prevention device 2 includes a blade 23 and a drive assembly. The blade 23 is disposed at one end of the air intake duct 1. The blade 23 is an arc-shaped structure, and the radius of curvature of the arc surface is optimized through fluid dynamics simulation to improve flow efficiency. The drive assembly is connected to the blade 23 and configured such that: in the normal state, the drive assembly drives the blade 23 to open; when backfire occurs, the drive assembly drives the blade 23 to close to prevent backfire gas from entering the air intake duct 1.

[0022] This application combines the curved structure of the intake duct 1 with the curved blades 23 of the backfire prevention device 2, so that the gas can be accelerated when passing through the intake duct 1. The curved blades 23 further enhance the tumble effect during the gas flow. The curvature of the blades 23 is matched with the curvature of the intake duct 1 to optimize the airflow guidance path, thereby significantly improving the uniformity and flowability of the mixture. At the same time, when backfire occurs, the drive component pushes the blades 23 to close, effectively blocking the reverse flow of backfire gas, ensuring the stable operation of the intake system, and thus improving the combustion efficiency and power output of the engine.

[0023] The backfire prevention device 2 of this application adopts a modular installation structure and is fixed to the intake duct 1 with standard bolts, which facilitates quick maintenance and replacement. The modular design shortens the replacement time of the blade 23 without disassembling the engine body.

[0024] Based on some embodiments, in this embodiment, the relationship between the outer cavity size, inner cavity size and middle size of the air intake duct 1 is as follows: the middle size is smaller than the inner cavity size, and the difference between the inner cavity size and the middle size is within a first set interval; the outer cavity size is larger than the inner cavity size, and the difference between the outer cavity size and the inner cavity size is within a first set interval, so that the inner wall of the air intake duct 1 forms an arc surface structure, and the lower limit of the first set interval is greater than 1.

[0025] See Figure 11 As shown, h1 is the narrowest dimension of the air intake duct 1, i.e., the middle dimension, h2 is the inner dimension of the air intake duct 1, and h3 is the outer dimension of the air intake duct 1.

[0026] The inner cavity height h2 of the air intake duct 1 is the same as the size of the air intake port. In this embodiment, the first set range is 2~3. The relationship between the outer cavity size, inner cavity size, and middle size of the air intake duct 1 is: h1=h2-2~3, h3=h2+2~3. The dimensional differences between the outer cavity size, inner cavity size, and middle size of the air intake duct 1 can be achieved by CNC milling to ensure smooth surface transition. Furthermore, the inner cavity and the middle part of the air intake duct 1 form a first inner wall, and the outer cavity and the middle part of the air intake duct 1 form a second inner wall; the ratio of the radius of the first inner wall to the size of the middle part is set within a second set range, and the ratio of the radius of the second inner wall to the size of the middle part is set within a third set range, and the lower limit values ​​of the second set range and the third set range are both greater than 1.

[0027] In this embodiment, the second set interval is set to 6~7, and the third set interval is set to 7~8. The first inner wall radius R1 = h1*(6~7), the second inner wall radius R2 = h1*(7~8), and the upper top surface and lower bottom surface of the inner wall of the air intake duct 1 are tangent.

[0028] It is important to note that h1 cannot be too large or too small, otherwise it will affect the gas flow rate: too large a value will not provide acceleration, while too small a value will restrict the gas flow rate. This design ensures a smooth transition of gas flow through intake duct 1, effectively avoiding airflow separation and turbulence. The value of h1 has a crucial impact on the gas flow rate. If h1 is too large, it will not effectively increase the gas flow rate and will not provide acceleration; if h1 is too small, it will excessively restrict the gas flow rate, resulting in a reduction in intake volume, thereby affecting engine power. By reasonably setting the range of h1, intake duct 1 can both ensure an increase in gas flow rate and maintain a sufficient intake volume, thereby achieving an effective increase in engine power and effective control of backfire.

[0029] Based on some embodiments, in this embodiment, the ratio of the arc radius of the blade 23 to the width of the blade 23 is located within a fourth set interval, and the lower limit of the fourth set interval is greater than 1.

[0030] The accelerated gas will be further accelerated and its tumble will be increased when it passes the curved blade 23, because the tilt angle of the blade 23 is 78°~82° (see...). Figure 7 As shown, limiting blocks 22 are set on both sides of the frame 21 to maximize the control of the opening angle of the blade 23. The blade 23 has an arc-shaped design with an arc radius R = 12~15 * the width of the blade 23. The arc radius is preset in conjunction with the elastic modulus parameter of the blade 23 material to ensure the stability of the curved surface under airflow impact and reduce turbulence generation. If the arc radius is too large, it will not accelerate the tumble flow; if the radius is too small, it will greatly increase the tumble ratio, but the airflow will not enter the combustion chamber, which will instead reduce the intake volume and reduce engine power. When the engine is working normally, after passing through the arc-shaped intake duct 1 and the concave blade 23, the intake air velocity will increase by 1.5 to 3 times, and at the same time, the tumble flow of the air-fuel mixture will be improved, resulting in better air-fuel mixing, higher combustion efficiency, and increased engine power.

[0031] There is a gap of 0.1 to 0.2 mm between adjacent blades 23 in the height direction, which allows for proper gas flow and prevents difficulty in opening the blades after they have been closed. The gap is controlled by the manufacturing process of the arc radius of the blades 23 and adapts to the thermal expansion characteristics of the material to maintain the reliability of the flow channel.

[0032] Based on some embodiments, in this embodiment, the backfire prevention device 2 further includes a frame 21, which is disposed at one end of the air intake duct 1, and the blade 23 is rotatably connected to the frame 21.

[0033] In this embodiment, the frame 21 is designed with an inner groove, and the blade 23 is arranged in the inner groove. The side wall of the inner groove is provided with a micro guide groove structure, which cooperates with the positioning protrusion of the blade 23 to ensure the stability of the movement trajectory of the blade 23 and avoid deviation caused by engine vibration.

[0034] Based on some embodiments, in this embodiment, the drive assembly includes: a drive motor assembly, a drive rod 24, and a connector. The drive rod 24 is slidably connected to the frame 21, and one end is connected to the drive motor assembly. The connector connects the drive rod 24 and the blade 23. The drive motor assembly drives the drive rod 24 to move up and down, so that the connector drives the blade 23 to open or close. The drive motor can be positioned far away from the air intake to avoid backflow of high-temperature gas. In addition, the drive motor can be equipped with a protective cover to ensure stable operation in the harsh environment of the engine compartment.

[0035] In this embodiment, the drive rod 24 passes through the middle of the frame 21 and slides up and down along the height of the frame 21 to ensure the linearity of the movement trajectory. Since the blade 23 is rotatably connected to the frame 21, the movement of the drive rod 24 can cause the blade 23 to flip through the connecting member. The drive rod 24 also serves as a blocking function to prevent the blade 23 from reversing to the inside of the intake duct 1 when closed, thus preventing backfire from failing and preventing combustion gases from backfireing into the intake duct 1.

[0036] Furthermore, in this embodiment, the connecting component includes a slide rod 241 and a connecting rod 230. The slide rod 241 is fixed to the drive rod 24; the connecting rod 230 is fixed to one end of the blade 23, and the slide rod 241 is slidably connected to the groove of the connecting rod 230. The drive rod 24 has a through groove 240 in its middle, the slide rod 241 is disposed within the through groove 240, and the connecting rod 230 passes through the through groove 240 and is slidably connected to the slide rod 241. In this embodiment, the contact surface between the connecting rod 230 and the slide rod 241 adopts a spherical transition design to accommodate minute angle changes.

[0037] See Figure 8 and Figure 9 As shown, the process of blade 23 opening is illustrated: when the drive rod 24 moves the slide rod 241 downward, the slide rod 241 can press down the connecting rod 230 to form a stable thrust transmission. Since blade 23 is rotatably connected to frame 21, blade 23 will not move down with slide rod 241, but will only rotate. At this time, blade 23 opens.

[0038] To ensure that the blade 23 closes when the drive rod 24 moves upward, a hinge is hinged to the bottom of the slide rod 241, and a groove is opened on the connecting rod 230. The shape of the groove matches the hinge to ensure smooth sliding. The hinge is slidably connected inside the groove, so that when the drive rod 24 moves upward, it can drive the connecting rod 230 back to its original position through the hinge.

[0039] Based on some embodiments, in this embodiment, the air intake structure also includes a pressure sensor and a controller. The pressure sensor is used to detect and send a first pressure value at the air intake port of the air intake duct 1 and a second pressure value inside the air intake duct 1. The controller is used to compare the received first pressure value and second pressure value with a set pressure value. When the first pressure value is greater than or equal to the set pressure value and the ratio of the set pressure value to the second pressure value is greater than or equal to a set threshold, the drive component drives the blade 23 to close.

[0040] In this embodiment, the pressure in the air inlet is continuously monitored. When the first pressure value of the air inlet reaches the set pressure value P, and the second pressure value of the air inlet 1 is P0, when P / P0≥2, that is, P≥2P0, the drive component is used to drive the blade 23 to close.

[0041] The dimensions of the backfire prevention device 2 in this application can be designed based on the engine displacement and the size of the intake port of each cylinder, including the frame 21 and the blades 23. The height of the frame 21 is consistent with the intake port 1, and the length is the same as the length of the intake port 1 of each cylinder. The blades 23 are generally designed with a width of 9 to 10, and are made of a special material with a thickness of about 0.5 mm to ensure that there is a backfire prevention device 2 for each cylinder intake port. Simultaneously, there is a drive rod 24 on the blade 23, which is connected to a small drive motor. The addition of a drive motor allows for synchronous monitoring of the pressure before and after the intake manifold through a control program, ensuring that the blades 23 must be closed when needed, and automatically initiating the opening and closing of the backfire prevention blades 23.

[0042] In summary, the integrated design of the arc-shaped intake duct 1, concave blades 23, and backfire prevention device 2 can accelerate fuel flow and improve tumble flow, significantly increasing intake efficiency, volume, and engine power. Through the coordinated optimization of the curvature of the intake duct 1 and the angle of the blades 23, airflow separation is ensured, improving energy utilization. The arc-shaped intake duct 1 increases the fuel intake velocity, while the controllable angle and concave blades 23 further enhance the fuel intake velocity and tumble flow. Multiple blades 23 with pressure feedback devices protect the engine in case of backfire, and the pressure sensor uses a ceramic encapsulation structure to effectively resist high-temperature vibration interference. The structure and arrangement of the arc-shaped intake duct 1 and blades 23 are rational and meet general design and manufacturing requirements. This design effectively prevents occasional backfire in a single cylinder caused by gas engine combustion. The problem is that each air intake is independently equipped with a backfire prevention device 2 to achieve single-cylinder fault isolation and avoid chain reactions; only the air intake pressure is monitored as feedback, and the synchronization threshold setting is reasonable to prevent abnormal start-up of the backfire prevention device 2; this application is generally a mechanical structure, but it can also add two systems combined with electronic control to play a double insurance role (the electronic control system is integrated through the engine ECU and supports backup power supply). In the event of failure of the mechanical backfire prevention structure, the electronic control system will immediately start to play a backfire prevention role; and this application can be extended to other gaseous fuel engines such as hydrogen and ammonia; at the same time, in view of the high diffusion characteristics of hydrogen fuel, the surface of the blade 23 is treated with a corrosion-resistant coating; this application makes the engine layout and maintenance convenient. The structure of this application is compact, and maintenance only requires replacing the blade 23 module without disassembling the engine body, which improves engine power while avoiding abnormal engine combustion problems.

[0043] In the description of this application, it should be noted that the terms "upper," "lower," etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. Unless otherwise expressly specified and limited, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication between two elements. For those skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0044] It should be noted that in this application, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0045] The above description is merely a specific embodiment of this application, enabling those skilled in the art to understand or implement this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. An air intake structure, characterized in that, It includes: Air intake (1), the inner wall of the air intake (1) is an arc surface structure; The backfire prevention device (2) includes a blade (23) and a drive assembly. The blade (23) is located at one end of the air intake (1). The blade (23) has an arc-shaped structure. The drive assembly is connected to the blade (23) and configured such that: in normal conditions, the drive assembly drives the blade (23) to open; and in the event of backfire, the drive assembly drives the blade (23) to close to prevent backfire gas from entering the air intake (1).

2. The intake structure as described in claim 1, characterized in that: The relationship between the outer cavity size, inner cavity size and middle size of the air intake (1) is as follows: the middle size is smaller than the inner cavity size, and the difference between the inner cavity size and the middle size is within a first set interval; the outer cavity size is larger than the inner cavity size, and the difference between the outer cavity size and the inner cavity size is within a first set interval, so that the inner wall of the air intake (1) forms an arc surface structure, and the lower limit of the first set interval is greater than 1.

3. The intake structure as described in claim 2, characterized in that: The upper top surface and the lower bottom surface of the inner wall of the air intake (1) are tangent.

4. The intake structure as described in claim 2, characterized in that: The inner cavity and the middle part of the air intake (1) form a first inner wall, and the outer cavity and the middle part of the air intake (1) form a second inner wall; The ratio of the radius to the central dimension of the first inner wall is within a second set range, and the ratio of the radius to the central dimension of the second inner wall is within a third set range. The lower limits of both the second and third set ranges are greater than 1.

5. The intake structure as described in claim 1, characterized in that: The ratio of the arc radius of the blade (23) to the width of the blade (23) is within the fourth set interval, and the lower limit of the fourth set interval is greater than 1.

6. The intake structure as described in claim 1, characterized in that: The backfire prevention device (2) also includes a frame (21), which is located at one end of the air intake (1), and the blade (23) is rotatably connected to the frame (21).

7. The intake structure as described in claim 6, characterized in that, The driving component includes: Drive motor assembly; Drive rod (24), which is slidably connected to frame (21) and one end is connected to drive motor assembly; A connector that connects the drive rod (24) and the blade (23); The drive motor unit drives the drive rod (24) to move up and down, so that the connecting piece drives the blade (23) to open or close.

8. The intake structure as described in claim 7, characterized in that, The connector includes: A slide bar (241) is fixed to a drive rod (24); The connecting rod (230) is fixed to one end of the blade (23), and the sliding rod (241) is slidably connected in the groove of the connecting rod (230).

9. The intake structure as described in claim 8, characterized in that: The drive rod (24) has a through groove (240) in the middle, the slide rod (241) is set in the through groove (240), and the connecting rod (230) passes through the through groove (240) and is slidably connected with the slide rod (241).

10. The intake structure as described in claim 1, characterized in that: The intake structure also includes a pressure sensor and a controller. The pressure sensor is used to detect and send a first pressure value at the intake port of the intake channel (1) and a second pressure value inside the intake channel (1). The controller is used to compare the received first pressure value and second pressure value with a set pressure value. When the first pressure value is greater than or equal to the set pressure value and the ratio of the set pressure value to the second pressure value is greater than or equal to a set threshold, the drive assembly drives the blade (23) to close.

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