Outlet back pressure bidirectional adjusting device and method for plane cascade experiment

Abstract

The invention relates to an outlet back pressure two-way adjusting device for a plane cascade experiment. The outlet back pressure two-way adjusting device comprises a cascade connecting flange, a baffle and a side wall. The cascade connecting flange is positioned at the bottom of the device and is horizontally arranged; the two baffles are vertically arranged in parallel, and the lower ends of the baffles are fixedly connected with the cascade connecting flange; the side wall is of a sectional structure and is composed of a rotating section, a flexible connecting section and a telescopic section, and the telescopic section is connected with the rotating section through the flexible connecting section. Molded lines on the two sides of the rotating section are of bicubic curve structures; side wall sliding blocks are arranged on the side walls, the two side walls are arranged between the two parallel baffles, and rotating sections at the lower ends of the side walls make contact with the edge of a flange opening of the cascade connecting flange to form a horn-mouth-shaped flow channel; the side wall sliding block is in sliding connection with the baffle groove channel. Expansion and contraction of the outlet are realized in the same device; the outlet area can be continuously changed, so that the continuous adjustment of the outlet back pressure is realized; the outlet area can be manually adjusted, and extra power equipment and complex structures are not needed.

Description

Technical Field

[0001] The invention belongs to the technical field of plane blade cascade experiments, and in particular relates to an outlet back pressure bidirectional regulating device and method for plane blade cascade experiments. Background Art

[0002] Plane cascade experiments are a key means to deeply study the flow characteristics inside turbine cascades, evaluate their aerodynamic performance, and optimize their designs. The development of plane cascade test bench technology has always attracted much attention. Turbine cascades have the highest efficiency and economy under design conditions, but their flow parameters will change with the changes in various technical requirements during actual operation. Therefore, in the process of cascade experiments, it is often necessary to measure the pressure, velocity and other parameters of the cascade at multiple operating points.

[0003] At present, the standard plane blade experimental device is mainly composed of an intake section, a stable section, a contraction acceleration section, a plane blade experimental section, and an outlet section. Among them, the outlet section not only plays the role of exhaust, but also plays the role of controlling the blade outlet back pressure. In the open-design outlet section, the outlet back pressure cannot be adjusted due to the fixed flow area. In order to meet the experimental requirements of variable outlet back pressure, a back pressure regulating device can be designed in the blade outlet section, such as using an orifice plate back pressure regulation or connecting a vacuum box to enhance the flexibility and accuracy of the experiment.

[0004] In open design low-speed wind tunnel test benches, the outlet is usually directly connected to the atmosphere. This is because, in the low-speed range (i.e., wind speeds from tens of meters per second to hundreds of meters per second), this design does not cause significant pressure differences or airflow disturbances. On this test bench, in order to change the static pressure at the outlet of the blade grid so that it is different from the outlet static pressure of the entire device (usually atmospheric pressure), an expansion section or contraction section with a fixed shape is usually connected after the blade grid test section. In the expansion section, as the cross-sectional area of ​​the flow channel gradually increases, the fluid velocity decreases accordingly, and the pressure increases accordingly, so that the static pressure at the outlet of the blade grid is lower than atmospheric pressure. On the contrary, in the contraction section, the gradual decrease in the cross-sectional area of ​​the flow channel causes the fluid velocity to increase and the pressure to decrease, resulting in the static pressure at the outlet of the blade grid being higher than atmospheric pressure. Such as Figure 1 As shown, the experimental section is connected to a diffuser section to demonstrate this pressure adjustment mechanism.

[0005] The back pressure regulating device of the outlet section of the plane cascade wind tunnel is composed of a pressure box, an upper diffuser, and a lower diffuser. These components are all located downstream of the plane cascade and together constitute the outlet section of the wind tunnel. Structurally, an upper support component is fixedly installed on the upper surface of the pressure box or the upper diffuser, and the upper end of the upper support component is connected to the upper wall of the wind tunnel in an adjustable manner. At the same time, a lower support component is fixedly installed on the lower surface of the lower diffuser, and its lower end is also connected to the lower wall of the wind tunnel in an adjustable manner. On the lower surface of the upper diffuser, a throttle plate with an adjustable angle is movably connected. By adjusting the opening angle of the throttle plate, the flow area of ​​the plane cascade outlet can be effectively changed, thereby realizing the adjustment of the back pressure of the wind tunnel outlet section. In addition, the lower wall of the pressure box is designed as a porous structure with a cavity inside. This design is intended to inhale the low-speed fluid on the lower wall to inhibit the development of the boundary layer, enhance the flow capacity, improve the periodicity of the cascade outlet, and thus improve the overall flow quality of the wind tunnel. For example, the patent with publication number CN112985742B.

[0006] The orifice plate back pressure regulating device uses circumferentially distributed flange holes and is tightly connected to the outlet section of the blade test bench by bolts. The core part of the device is a matching installation unit consisting of an orifice plate and a plugging plate, in which the orifice plate is fixed and cannot rotate, while the plugging plate is located inside the orifice plate and is designed to be a rotatable structure. Exhaust ports are provided on both the orifice plate and the plugging plate. By rotating the plugging plate, the area opening angle of the exhaust port can be adjusted, thereby controlling the exhaust volume of the back pressure regulating device to meet the needs under different experimental conditions. For example, the patent with application number 201611211125.4.

[0007] Connecting the vacuum box design By starting the vacuum pump, the air in the vacuum box can be extracted to adjust the pressure in the box. Accurately controlling the pumping speed of the vacuum pump can achieve accurate management of the speed and amplitude of the pressure drop in the vacuum box. Connecting the cascade outlet section to the vacuum box through a pipeline can create a low-pressure environment at the cascade outlet section. By adjusting the pressure in the vacuum box, the back pressure of the cascade outlet section can be effectively changed. In order to ensure the stability and safety of the experiment, the design of the pipeline must have sufficient strength and good sealing performance to withstand the pressure difference between the cascade outlet section and the vacuum box.

[0008] The above prior art has the following technical defects:

[0009] 1. The back pressure adjustment range is discontinuous: the open design cannot adjust the back pressure, and the back pressure adjustment of the orifice type adjustment device usually relies on a fixed geometric shape or aperture size, resulting in a discrete adjustment range and unable to achieve smooth and continuous adjustment.

[0010] 2. The back pressure adjustment range does not meet the universal requirements: Each adjustment method has its inherent adjustment direction, that is, reducing speed and increasing pressure or increasing speed and reducing pressure, and two-way adjustment cannot be achieved.

[0011] 3. System complexity and cost: Connecting the vacuum box requires additional equipment, which increases the complexity of the system and also increases the difficulty of operation and maintenance. The orifice type adjustment device also has higher requirements for processing accuracy.

[0012] 4. Failure to consider the pressure loss in the outlet section design: Failure to consider the impact of the outlet section curve on the pressure loss may result in a large pressure loss at the outlet, which does not meet the experimental requirements. Summary of the invention

[0013] The purpose of the present invention is to provide an outlet back pressure bidirectional adjustment device and method for plane blade experiment, in which outlet expansion and contraction are realized in the same device; the outlet area can be continuously changed, thereby realizing continuous adjustment of the outlet back pressure; the outlet area can be manually adjusted without the need for additional power equipment and complex structure.

[0014] The present invention provides an outlet back pressure bidirectional regulating device for a plane cascade experiment, comprising a cascade connecting flange, a baffle, and a side wall;

[0015] The blade cascade connection flange is located at the bottom of the device, arranged horizontally, and is used to connect with the outlet flange of the blade cascade test section; the two baffles are arranged vertically and in parallel, and their lower ends are fixedly connected with the blade cascade connection flange;

[0016] The side wall adopts a segmented structure, consisting of a rotating section, a flexible connecting section, and a telescopic section, wherein the telescopic section is connected to the rotating section through the flexible connecting section; the profile lines on both sides of the rotating section adopt a bicubic curve structure;

[0017] The side wall is provided with a side wall slider, and the baffle is provided with a baffle groove; the side wall slider includes a telescopic section slider and a rotating section slider; the baffle groove includes a telescopic section sliding groove and a rotating section sliding groove;

[0018] The two side walls are arranged between the two parallel baffles, and the rotating sections at the lower ends thereof are in contact with the flange opening edge of the blade cascade connecting flange to form a trumpet-shaped flow channel;

[0019] The side wall slider is slidably connected to the baffle groove. When the rotating section rotates with its starting point as the axis, the telescopic section moves horizontally and telescopes up and down, driving the flexible connection section to move and bend accordingly.

[0020] Furthermore, slots are provided at the four corners of the blade connection flange, and two latches are provided under the baffle. The latches are slidably inserted into the slots corresponding to the blade connection flange and are fixedly connected to the blade connection flange by bolts.

[0021] Furthermore, the telescopic section is formed by nesting a telescopic section inner component and a telescopic section outer component, and is used to achieve upward and downward telescopic extension of the assembly through the relative sliding of the telescopic section inner component and the telescopic section outer component; the telescopic section inner component is provided with a bolt hole, and the telescopic section outer component is provided with a slide groove, and the bolt passes through the bolt hole, acting as a slider and playing a fixing role after the telescopic extension is completed.

[0022] Furthermore, the flexible connecting section is made of rubber material and can be bent and deformed, and is used for smooth transition of the side wall of the flow channel to reduce flow loss.

[0023] Furthermore, the shape and position of the sliding groove of the rotating section correspond to the motion trajectory of the sliding block of the rotating section, and the shape and position of the sliding groove of the telescopic section correspond to the motion trajectory of the sliding block of the telescopic section.

[0024] Furthermore, the double-sided profiles of the rotating section adopt bicubic curves of different shapes, wherein the profile on one side is used for flow channel contraction to achieve pressure reduction and speed increase, and the profile on the other side can be used for flow channel expansion to achieve pressure increase and speed decrease.

[0025] The present invention also provides a method for bidirectionally regulating the outlet back pressure using the device, wherein the back pressure regulation process of the contraction flow channel includes:

[0026] 1) In the initial state, the side wall is in the original position, the telescopic section is retracted to the shortest, and the flexible connection section is not deformed;

[0027] 2) If the outlet area needs to be further reduced, the side wall slider is moved along the baffle groove to move the telescopic section toward the center of the flow channel to the target diameter;

[0028] 3) When the minimum outlet area is reached, the telescopic section is fully extended to its longest state, ensuring that the outlet area reaches the set minimum value.

[0029] Furthermore, in step 2), the inner component of the telescopic section slides downward relative to the outer component of the telescopic section, and the rotating section simultaneously rotates inward to cooperate and adjust. As the telescopic section moves, the flexible connecting section begins to bend to adapt to changes in the flow channel.

[0030] Furthermore, the expansion channel back pressure adjustment process includes:

[0031] (1) The positions of the two side walls are exchanged so that the side walls are in the initial position when expanded. At this time, the telescopic section is shortened to the shortest and the flexible connection section is not deformed;

[0032] (2) If the outlet area needs to be further increased, the side wall slider is moved along the baffle groove to move the telescopic section away from the center of the flow channel to the target diameter;

[0033] (3) When the maximum outlet area is reached, the retractable section is fully extended to its longest state, ensuring that the outlet area reaches the set maximum value.

[0034] Furthermore, in step (2), the inner component of the telescopic section slides downward relative to the outer component of the telescopic section, and the rotating section rotates outward in coordination to adjust the flow channel area, and as the telescopic section moves, the flexible connecting section bends accordingly.

[0035] By means of the above scheme, the outlet back pressure bidirectional adjustment device and method for plane cascade experiment have the following technical effects:

[0036] 1) Reducing gas flow loss: Through the bicubic curve design and the flexible connection section, the present invention can reduce the flow loss of the gas in the flow channel and improve the overall efficiency.

[0037] 2) Accurately adjust the outlet area and back pressure: The design of the retractable section and the manual adjustment of the slider enable the present invention to accurately control the flow channel outlet area, and then adjust the back pressure to meet the requirements of different working conditions.

[0038] 3) Improve the adaptability of the device: The double-sided profile design of the rotating section enables the device to adapt to the needs of flow channel contraction and expansion, increasing the application scenarios of the device.

[0039] 4) Convenient operation and maintenance: The side wall position can be adjusted by manually moving the slider, which is simple to operate and easy to maintain.

[0040] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present invention in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 A schematic diagram of the structure of the existing open design;

[0042] Figure 2 It is a schematic structural diagram of the outlet back pressure bidirectional regulating device used for plane cascade experiment of the present invention;

[0043] Figure 3 It is a structural schematic diagram of the blade cascade connection flange of the present invention;

[0044] Figure 4 This is a schematic diagram of the baffle structure of the present invention;

[0045] Figure 5 It is a schematic diagram of the side wall structure of the present invention;

[0046] Figure 6 This is a schematic diagram of the double-sided profile design of the rotating section of the present invention.

[0047] Figure 7 This is a schematic diagram of the back pressure adjustment process of the present invention;

[0048] Figure 8 It is a schematic diagram of the contraction flow channel and the expansion flow channel of the present invention.

[0049] Numbers in the figure:

[0050] 1. Blade connection flange; 11-slot;

[0051] 2. Baffle; 21- latch; 22- sliding groove of rotating section; 23- sliding groove of telescopic section;

[0052] 3-side wall; 31-rotating section; 311-rotating section slider; 32-flexible connecting section; 33-retractable section; 331-retractable section inner component; 332-retractable section outer component; 333-bolt hole; 334-slideway; 335-retractable section slider. DETAILED DESCRIPTION

[0053] The specific implementation of the present invention is further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention.

[0054] Ginseng Figures 1 to 5 As shown, this embodiment provides an outlet back pressure bidirectional regulating device for a plane cascade experiment, which consists of three parts: a cascade connection flange 1, a baffle 2, and a side wall 3. The cascade connection flange 1 is located at the bottom of the device and is connected to the outlet flange of the cascade experimental section. Slots 11 are provided at its four corners for installing the baffle 2. Two latches 21 are provided below the baffle 2. These latches 21 can be slidably inserted into the slots 11 of the cascade connection flange 1 until the inner wall of the baffle 2 is aligned parallel to the inner wall of the flange, and then the baffle 2 is fixed with bolts.

[0055] The side wall 3 adopts a segmented design, consisting of a rotating section 31, a flexible connection section 32, and a telescopic section 33. Among them, the surface profile of the rotating section 31 adopts a bicubic curve design, the purpose of which is to minimize the gas flow loss when the flow channel area changes along the flow direction. The telescopic section 33 is composed of two nested inner and outer components, and the upward and downward telescopic movement of the assembly is achieved through the relative sliding of the telescopic section inner component 331 and the telescopic section outer component 332. The telescopic section inner component 331 is provided with a bolt hole 333, and the telescopic section outer component 332 is provided with a slide groove 334. The bolt acts as a slider and plays a fixing role after the telescopic movement is completed. The side wall is divided into a rotating section, a flexible connection section and a telescopic section, which realizes the flexible adjustment of the side wall when the flow channel outlet area changes and reduces the flow loss.

[0056] The flexible connecting section 32 is made of rubber material and can be bent and deformed. It is used to connect the rotating section 31 and the telescopic section 33, so as to achieve a smooth transition of the side wall of the flow channel and reduce flow losses. When the rotating section 31 rotates with its starting point as the axis, the telescopic section 33 can move laterally and stretch up and down, and the flexible connecting section 32 also moves and bends accordingly. This design can minimize the loss of gas flow when adjusting the flow channel outlet area, and ensure that the gas flows out evenly in the flow channel in a direction perpendicular to the outlet.

[0057] The side wall 3 is provided with a plurality of side wall sliders, and the baffle 2 is provided with a plurality of baffle grooves; the side wall sliders include a telescopic section slider 335 and a rotating section slider 311; the baffle grooves include a telescopic section sliding groove 23 and a rotating section sliding groove 22, and the shape and position of the grooves correspond to the movement trajectory of the sliders on the side wall. Therefore, the position of the side wall can be adjusted by manually moving the sliders, so as to achieve the purpose of changing the outlet back pressure. In this embodiment, a telescopic section slider 335 is provided on the telescopic section 33, and two rotating section sliders 311 are provided on the rotating section 31; a linear telescopic section sliding groove 23 is provided above the baffle 2, corresponding to the shape and position of the telescopic section slider 335, and an arc-shaped rotating section sliding groove 22 is provided in the middle of the baffle 2, corresponding to the shape and position of the rotating section slider 311.

[0058] Although the profiles on both sides of the rotating section 31 are both bicubic curves, their shapes are different and need to be determined through precise design.

[0059] The calculation formula of the bicubic curve is as follows:

[0060]

[0061] Where: L is the length of the rotating section along the gas flow direction, x m is the inflection point of the bicubic curve, set to 0.5.

[0062] When designing the shrinkage side profile, R 1 R is the radius of the inlet section of the contraction section, 2 is the radius of the contraction section outlet, and R is the radius of the section at the distance x from the contraction section inlet. When designing the expansion side profile, R 1 R is the radius of the expansion section outlet, 2 is the radius of the expansion section inlet section, and R is the radius of the section at the distance x from the expansion section outlet section. From this, the contraction side profile and expansion side profile of the rotating section can be calculated respectively. Figure 6 shown.

[0063] The contraction side profile of the rotating section is used for flow channel contraction to achieve pressure reduction and speed increase, while the expansion side profile can be used for flow channel expansion to achieve pressure increase and speed reduction. Through this double-sided double cubic curve profile design, the rotating section can adjust the use side as needed to achieve the purpose of pressure reduction and speed increase and pressure increase and speed reduction. The double-sided profile design of the rotating section increases the flexibility and scope of application of the device.

[0064] Ginseng Figure 7 , Figure 8 As shown in the figure, the back pressure adjustment process of the contraction flow channel: in the initial state, the side wall is in the original position, the retractable section is retracted to the shortest, and the flexible connection section is not deformed. If the outlet area needs to be further reduced, the side wall slider needs to be moved along the baffle groove to move the retractable section toward the center of the flow channel to the target diameter. During this process, the inner component slides downward relative to the outer component, and the rotating section rotates inward at the same time to cooperate and adjust. As the retractable section moves, the flexible connection section begins to bend to adapt to the changes in the flow channel. When the minimum outlet area is reached, the retractable section is fully extended to its longest state to ensure that the outlet area reaches the set minimum value.

[0065] Back pressure adjustment process of expansion channel: First, swap the positions of the two side walls so that the side walls are in the initial position of the expansion state. At this time, the retractable section is shortened to the shortest and the flexible connection section is not deformed. If the outlet area needs to be further increased, the side wall slider needs to be moved along the baffle groove to move the retractable section away from the center of the flow channel to the target diameter. During this process, the inner component slides downward relative to the outer component, and the rotating section rotates outward to adjust the flow channel area. As the retractable section moves, the flexible connection section bends accordingly. When the maximum outlet area is reached, the retractable section is fully extended to its longest state to ensure that the outlet area reaches the set maximum value.

[0066] In other examples, the rotating section may also use multiple sections of rotatable small blades instead of the integral rotating section, and each small blade may be rotated independently to adjust the shape of the flow channel. The retractable section may also use elastic materials to change the length of the flow channel by stretching or compressing. The flexible connecting section may also use a flexible plate with pre-bent lines.

[0067] The outlet back pressure bidirectional adjustment device and method for plane cascade experiment has the following technical effects:

[0068] 1) Reducing gas flow loss: Through the bicubic curve design and the flexible connection section, the present invention can reduce the flow loss of the gas in the flow channel and improve the overall efficiency.

[0069] 2) Accurately adjust the outlet area and back pressure: The design of the retractable section and the manual adjustment of the slider enable the present invention to accurately control the flow channel outlet area, and then adjust the back pressure to meet the requirements of different working conditions.

[0070] 3) Improve the adaptability of the device: The double-sided profile design of the rotating section enables the device to adapt to the needs of flow channel contraction and expansion, increasing the application scenarios of the device.

[0071] 4) Convenient operation and maintenance: The side wall position can be adjusted by manually moving the slider, which is simple to operate and maintain. The groove on the baffle and the slider on the side wall cooperate to realize the function of manually adjusting the outlet back pressure, which is easy to operate.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A bidirectional regulating device for outlet back pressure used in plane cascade experiments, characterized in that: It comprises a blade cascade connecting flange (1), a baffle (2), and a side wall (3); The blade cascade connection flange (1) is located at the bottom of the device, arranged horizontally, and is used to connect with the outlet flange of the blade cascade test section; the two baffles (2) are arranged vertically and in parallel, and their lower ends are fixedly connected to the blade cascade connection flange (1); The side wall (3) adopts a segmented structure, consisting of a rotating section (31), a flexible connecting section (32), and a telescopic section (33); the telescopic section (33) is connected to the rotating section (31) through the flexible connecting section (32); the profile lines on both sides of the rotating section (31) adopt a bicubic curve structure; The side wall (3) is provided with a side wall slider, and the baffle (2) is provided with a baffle groove; the side wall slider comprises a telescopic section slider (335) and a rotating section slider (311); the baffle groove comprises a telescopic section sliding groove (23) and a rotating section sliding groove (22); The two side walls (3) are arranged between the two parallel baffles, and the rotating sections (31) at the lower ends thereof are in contact with the flange opening edge of the blade cascade connection flange (1), thereby forming a bell-shaped flow channel; The side wall slider is slidably connected to the baffle groove. When the rotating section (31) rotates with its starting point as the axis, the telescopic section (33) moves laterally and telescopes up and down, driving the flexible connection section (32) to move and bend accordingly.

2. The outlet back pressure bidirectional regulating device for plane cascade experiment according to claim 1 is characterized in that: The blade cascade connection flange (1) is provided with slots (11) at four corners, and two latches (21) are provided below the baffle (2). The latches (21) are slidably inserted into the slots (11) corresponding to the blade cascade connection flange (1) and are fixedly connected to the blade cascade connection flange (1) by bolts.

3. The outlet back pressure bidirectional regulating device for plane cascade experiment according to claim 2 is characterized in that: The telescopic section (33) is formed by nesting a telescopic section inner component (331) and a telescopic section outer component (332), and is used to realize the upward and downward telescopic extension of the assembly through the relative sliding of the telescopic section inner component (331) and the telescopic section outer component (332); the telescopic section inner component (331) is provided with a bolt hole (333), and the telescopic section outer component (332) is provided with a slide groove (334), and the bolt passes through the bolt hole (333), acts as a slider and plays a fixing role after the telescopic extension is completed.

4. The outlet back pressure bidirectional regulating device for plane cascade experiment according to claim 3 is characterized in that: The flexible connecting section (32) is made of rubber material and can be bent and deformed, and is used for smooth transition of the side wall of the flow channel to reduce flow loss.

5. The outlet back pressure bidirectional regulating device for plane cascade experiment according to claim 4 is characterized in that: The shape and position of the rotating section sliding groove (22) correspond to the motion trajectory of the rotating section slider (311), and the shape and position of the telescopic section sliding groove (23) correspond to the motion trajectory of the telescopic section slider (335).

6. The outlet back pressure bidirectional regulating device for plane blade cascade experiment according to claim 1, characterized in that: The double-sided profiles of the rotating section adopt bicubic curves of different shapes, wherein the profile on one side is used for flow channel contraction to achieve pressure reduction and speed increase, and the profile on the other side can be used for flow channel expansion to achieve pressure increase and speed decrease.

7. A method for bidirectionally regulating outlet back pressure using the device according to any one of claims 1 to 6, characterized in that: The back pressure adjustment process of the contraction flow channel includes: 1) In the initial state, the side wall is in the original position, the telescopic section is retracted to the shortest, and the flexible connection section is not deformed; 2) If the outlet area needs to be further reduced, the side wall slider is moved along the baffle groove to move the telescopic section toward the center of the flow channel to the target diameter; 3) When the minimum outlet area is reached, the telescopic section is fully extended to its longest state, ensuring that the outlet area reaches the set minimum value.

8. The outlet back pressure bidirectional regulation method according to claim 7, characterized in that: In the step 2), the inner component of the telescopic section slides downward relative to the outer component of the telescopic section, and the rotating section rotates inward to cooperate and adjust. As the telescopic section moves, the flexible connecting section begins to bend to adapt to the changes in the flow channel.

9. The outlet back pressure bidirectional regulation method according to claim 8, characterized in that: The expansion channel back pressure adjustment process includes: (1) The positions of the two side walls are exchanged so that the side walls are in the initial position when expanded. At this time, the telescopic section is shortened to the shortest and the flexible connection section is not deformed; (2) If the outlet area needs to be further increased, the side wall slider is moved along the baffle groove to move the telescopic section away from the center of the flow channel to the target diameter; (3) When the maximum outlet area is reached, the retractable section is fully extended to its longest state, ensuring that the outlet area reaches the set maximum value.

10. The outlet back pressure bidirectional regulation method according to claim 9, characterized in that: In the step (2), the inner component of the telescopic section slides downward relative to the outer component of the telescopic section, and the rotating section rotates outward in coordination to adjust the flow channel area. As the telescopic section moves, the flexible connecting section bends accordingly.

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