An outlet back pressure two-way adjusting device and method for planar cascade experiment

Abstract

The application relates to an outlet back pressure two-way adjusting device for a plane cascade experiment, which comprises a cascade connecting flange, a baffle and a side wall. The cascade connecting flange is arranged horizontally at the bottom of the device. Two baffles are arranged vertically and in parallel, and the lower ends of the two baffles are fixedly connected with the cascade connecting flange. The side wall adopts a sectional structure and is composed of a rotating section, a flexible connecting section and an extensible section. The extensible section is connected with the rotating section through the flexible connecting section. The double-side profile lines of the rotating section adopt a double cubic curve structure. The side wall is provided with a side wall sliding block, and the two side walls are arranged between the two parallel baffles. The rotating section at the lower end of the side wall is in contact with the flange opening edge of the cascade connecting flange, so as to form a horn-shaped flow channel. The side wall sliding block is slidably connected with the baffle groove. The outlet expansion and contraction 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 no additional power equipment and complex structure are needed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of planar cascade experiment, and particularly relates to an outlet back pressure bidirectional adjusting device and method for planar cascade experiment. BACKGROUND

[0002] Planar cascade experiment is a key means for in-depth study of internal flow characteristics of turbine cascade, evaluation of its aerodynamic performance and optimization design. The development of planar cascade experiment table technology has always been concerned. The efficiency and economy of turbine cascade are the highest under the design working condition, but in actual operation, the flow parameters will change with the change of various technical requirements. Therefore, in the process of cascade experiment, the pressure, velocity and other parameters of the cascade at multiple working points often need to be measured.

[0003] At present, the standard planar cascade experiment device mainly consists of an inlet section, a stable section, a contraction and acceleration section, a planar cascade experiment section and an outlet section. Among them, the outlet section can not only play the role of exhaust, but also can play the role of cascade outlet back pressure control. In the open design outlet section, since the through-flow area is fixed, the outlet back pressure cannot be adjusted. In order to realize the experimental requirement of variable outlet back pressure, a back pressure adjusting device can be designed at the outlet section of the cascade, such as using a hole plate type back pressure adjusting or connecting a vacuum tank, etc., to enhance the flexibility and accuracy of the experiment.

[0004] In the open design of low-speed wind tunnel experiment table, the outlet is usually directly connected with the atmosphere. This is because, in the low-speed range (i.e. the wind speed from several tens of meters per second to several hundred meters per second), this design will not cause significant pressure difference or air flow disturbance. In order to change the static pressure of the cascade outlet, so that it is different from the outlet static pressure of the whole device (usually atmospheric pressure), a fixed shape expansion section or contraction section is usually connected after the cascade experiment section. In the expansion section, with the gradual increase of the flow passage cross-sectional area, the fluid velocity decreases accordingly, and the pressure increases, so that the static pressure of the cascade outlet is lower than the atmospheric pressure. On the contrary, in the contraction section, the gradual decrease of the flow passage cross-sectional area leads to the increase of the fluid velocity and the decrease of the pressure, and as a result, the static pressure of the cascade outlet is higher than the atmospheric pressure. As shown in Figure 1 , an expansion section is connected after the experiment section to show this pressure adjustment mechanism.

[0005] The outlet section back pressure regulating device of the plane cascade wind tunnel is composed of a pressure box, an upper diffusion plate, and a lower diffusion plate. These components are located downstream of the plane cascade and collectively form the outlet section of the wind tunnel. In terms of structure, the upper surface of the pressure box or the upper diffusion plate is fixedly installed with an upper support component, and the upper end of the upper support component is connected to the upper wall of the wind tunnel in an up-down adjustable manner. At the same time, the lower surface of the lower diffusion plate is fixedly installed with a lower support component, and the lower end of the lower support component is also connected to the lower wall of the wind tunnel in an up-down adjustable manner. On the lower surface of the upper diffusion plate, an angle-adjustable throttle plate is movably connected. By adjusting the opening angle of the throttle plate, the through-flow area of the plane cascade outlet can be effectively changed, thereby realizing the regulation 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 hollow cavity inside, which is designed to suck low-speed fluid from the lower wall surface to suppress the development of the boundary layer, enhance the through-flow capacity, improve the periodicity of the cascade outlet, and thus improve the overall flow quality of the wind tunnel. As disclosed in patent CN112985742B.

[0006] The orifice plate type back pressure regulating device adopts circumferentially distributed flange holes and is tightly connected to the outlet section of the cascade test bench through bolts. The core part of the device is a matching installation unit composed of an orifice plate and a plug plate, wherein the orifice plate is fixed and cannot rotate, and the plug plate is located inside the orifice plate and is designed as a rotatable structure. Both the orifice plate and the plug plate are provided with exhaust ports, and by rotating the plug plate, the area opening angle of the exhaust port can be adjusted to control the exhaust capacity of the back pressure regulating device to meet the requirements under different experimental conditions. As disclosed in patent application No. 201611211125.4.

[0007] The connection vacuum box design can extract air from the vacuum box by starting the vacuum pump to adjust the pressure in the box. Precise control of the pumping speed of the vacuum pump can accurately manage the pressure drop speed and amplitude 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. To ensure the stability and safety of the experiment, the pipeline design 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-mentioned prior art has the following technical defects:

[0009] 1. The back pressure regulation range is discontinuous: the open design cannot regulate the back pressure, and the orifice plate type regulating device usually relies on fixed geometry or orifice size, resulting in discrete regulation range and inability to achieve smooth and continuous regulation.

[0010] 2. The back pressure regulation range does not meet the universal demand: each regulation method has its inherent regulation direction, i.e. speed reduction and pressure increase or speed increase and pressure reduction, and cannot realize bidirectional regulation.

[0011] 3. System complexity and cost: Connecting a vacuum tank requires additional equipment, increasing the complexity of the system, while also increasing the difficulty of operation and maintenance. The orifice type adjustment device also has higher requirements for processing precision.

[0012] 4. Pressure loss not considered in the design of the outlet section: The influence of the outlet section curve on pressure loss is not considered, resulting in a large possible pressure loss at the outlet, which does not meet the experimental requirements. SUMMARY

[0013] The purpose of the present application is to provide an outlet back pressure two-way adjustment device and method for planar cascade experiment, which realizes outlet expansion and contraction in the same device; the outlet area can be continuously changed, thereby realizing continuous adjustment of outlet back pressure; the outlet area can be manually adjusted without additional power equipment and complex structure.

[0014] The present application provides an outlet back pressure two-way adjustment device for planar cascade experiment, comprising a cascade connection flange, a baffle, and a side wall.

[0015] The cascade connection flange is located at the bottom of the device and is horizontally arranged for connection with the outlet flange of the cascade experiment section; two pieces of the baffle are vertically and parallel arranged, with the lower end fixedly connected with the cascade connection flange.

[0016] The side wall adopts a segmented structure, which is composed of a rotating segment, a flexible connection segment, and an extendable segment; the extendable segment is connected with the rotating segment through the flexible connection segment; the double-side profile lines of the rotating segment both adopt a double cubic curve structure.

[0017] The side wall is provided with a side wall sliding block, and the baffle is provided with a baffle channel; the side wall sliding block comprises an extendable segment sliding block and a rotating segment sliding block; the baffle channel comprises an extendable segment sliding channel and a rotating segment sliding channel.

[0018] The two pieces of the side wall are arranged between the two parallel baffles, with the rotating segment at the lower end in contact with the flange opening edge of the cascade connection flange, forming a horn-shaped flow passage.

[0019] The side wall sliding block and the baffle channel are slidingly connected; when the rotating segment rotates with its starting point as the axis, the extendable segment moves horizontally and extends up and down, driving the flexible connection segment to move and bend.

[0020] Further, the cascade connection flange is provided with a slot at each corner, and the baffle is equipped with two pins below; the pins are slidingly inserted into the corresponding slots of the cascade connection flange and are fixedly connected with the cascade connection flange through bolts.

[0021] Further, the telescopic section is nested by an inner telescopic component and an outer telescopic component, and the telescopic section is telescoped up and down by relative sliding of the inner telescopic component and the outer telescopic component; the inner telescopic component is provided with bolt holes, and the outer telescopic component is provided with sliding grooves, and the bolts pass through the bolt holes to serve as sliding blocks and play a fixing role after telescoping.

[0022] Further, 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] Further, the shape and position of the sliding groove of the rotating section correspond to the movement 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 movement trajectory of the sliding block of the telescopic section.

[0024] Further, the double cubic curves of different shapes of the double-side profile of the rotating section are used for flow channel contraction to realize pressure reduction and speed increase, and the other side profile is used for flow channel expansion to realize pressure increase and speed reduction.

[0025] The application also provides an outlet back pressure two-way adjusting method using the device, wherein the contraction flow channel back pressure adjusting process comprises:

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

[0027] 2) If it is required to further reduce the outlet area, the side wall sliding block is moved along the baffle groove to move the telescopic section to the target diameter in the direction of the flow channel center;

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

[0029] Further, in the step 2), the inner telescopic component is slid downward relative to the outer telescopic component, and the rotating section is simultaneously rotated inward to adjust and match, and with the movement of the telescopic section, the flexible connecting section starts to bend to adapt to the change of the flow channel.

[0030] Further, the expansion flow channel back pressure adjusting process comprises:

[0031] (1) The positions of the two side walls are exchanged, and the side wall is located at the initial position in the expansion state, at this time, the telescopic section is retracted to the shortest, and the flexible connecting section is not deformed;

[0032] (2) If it is required to further increase the outlet area, the side wall sliding block is moved along the baffle groove to move the telescopic section to the target diameter away from the flow channel center;

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

[0034] Further, in step (2), the inner assembly of the telescopic section slides downward relative to the outer assembly, and the rotating section rotates outward to adjust the flow passage area. As the telescopic section moves, the flexible connecting section bends accordingly.

[0035] Through the above-mentioned scheme, the outlet back pressure bidirectional adjusting device and method for planar cascade experiment have the following technical effects:

[0036] 1) Reducing gas flow loss: Through the double cubic curve design and the flexible connecting section, the invention can reduce the gas flow loss in the flow passage, improving the overall efficiency.

[0037] 2) Accurate adjustment of outlet area and back pressure: The design of the telescopic section and the manual adjustment of the slider enable the invention to accurately control the outlet area of the flow passage, thereby adjusting the back pressure to meet different working condition requirements.

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

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

[0040] The above description is only a summary of the technical solutions of the invention. In order to more clearly understand the technical means of the invention and to implement the content of the specification, the following describes the preferred embodiments of the invention in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a structural diagram of the existing open design;

[0042] Figure 2 is a structural diagram of the outlet back pressure bidirectional adjusting device for planar cascade experiment of the invention;

[0043] Figure 3 is a structural diagram of the cascade connecting flange of the invention;

[0044] Figure 4 is a structural diagram of the baffle of the invention;

[0045] Figure 5 is a structural diagram of the side wall of the invention;

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

[0047] Figure 7 Schematic diagram of the back pressure regulation process of the present invention;

[0048] Figure 8 Schematic diagram of the contraction channel and expansion channel of the present invention.

[0049] Reference numerals in the figure:

[0050] 1. Cascade connection flange; 11. Slot;

[0051] 2. Baffle; 21. Pin; 22. Rotating section sliding channel; 23. Telescopic section sliding channel;

[0052] 3. Side wall; 31. Rotating section; 311. Rotating section slider; 32. Flexible connection section; 33. Telescopic section; 331. Inner component of telescopic section; 332. Outer component of telescopic section; 333. Bolt hole; 334. Chute; 335. Telescopic section slider. Specific implementation manner

[0053] The following combines the drawings and embodiments to further describe the specific implementation manner of the present invention in detail. The following embodiments are used to illustrate the present invention, but are not used to limit the scope of the present invention.

[0054] Refer Figures 1 to 5 As shown, this embodiment provides a two-way outlet back pressure regulating device for planar cascade experiments. The device 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 experiment section. Slots 11 are provided at its four corners for installing the baffle 2. Two pins 21 are equipped below the baffle 2. These pins 21 can slide and insert into the slots 11 of the cascade connection flange 1 until the inner wall of the baffle 2 is parallel and aligned with the inner wall of the flange, and then the baffle 2 is fixed with bolts.

[0055] The side wall 3 adopts a segmented design and is composed 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 to minimize 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 up and down telescoping of the assembly is achieved through the relative sliding of the inner component 331 and the outer component 332 of the telescopic section. Bolt holes 333 are provided on the inner component 331 of the telescopic section, and chutes 334 are provided on the outer component 332 of the telescopic section. Bolts act as sliders and play a fixing role after the telescoping is completed. The side wall is divided into a rotating section, a flexible connection section, and a telescopic section, realizing the flexible adjustment of the side wall when the outlet area of the flow channel changes and reducing the flow loss.

[0056] The flexible connecting section 32 is made of rubber material and can be bent and deformed, and is used to connect the rotating section 31 and the telescopic section 33, so as to realize smooth transition of the side wall of the flow channel and reduce flow loss. When the rotating section 31 rotates around 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 outlet area of the flow channel, and ensure that the gas flows uniformly in the flow channel in a direction perpendicular to the outlet.

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

[0058] Although the double cubic curve of the rotating section 31 is a double cubic curve on both sides, the shapes are different, and need to be determined by accurate design.

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

[0060]

[0061] Wherein, L is the length of the rotating section along the gas flow direction, x m is the position of the inflection point of the double cubic curve, which is 0.5.

[0062] When designing the contraction side profile, R1 is the radius of the inlet cross section of the contraction section, R2 is the radius of the outlet cross section of the contraction section, and R is the radius of the cross section at a distance x from the inlet cross section of the contraction section. When designing the expansion side profile, R1 is the radius of the outlet cross section of the expansion section, R2 is the radius of the inlet cross section of the expansion section, and R is the radius of the cross section at a distance x from the outlet cross section of the expansion section. Thus, the contraction side profile and the expansion side profile of the rotating section can be calculated respectively, as shown in Figure 6 .

[0063] The contraction side profile of the rotating section is used for flow channel contraction to realize pressure reduction and speed increase, and the expansion side profile can be used for flow channel expansion to realize pressure increase and speed reduction. Through this double-side double cubic curve profile design, the rotating section can be adjusted and used according to the needs, so as to achieve the purposes of pressure reduction and speed increase and pressure increase and speed reduction. The double-side profile design of the rotating section increases the flexibility and application range of the device.

[0064] Referring to FIG. 6, the contraction flow passage back pressure adjustment process is as follows: in the initial state, the side walls are in the original position, the telescopic section is retracted to the shortest, and the flexible connection section has no deformation. If further reduction of the outlet area is required, the side wall slider is moved along the baffle groove, and the telescopic section is moved to the target diameter away from the center of the flow passage. In this process, the inner assembly slides downward relative to the outer assembly, and the rotating section is adjusted by rotating inward. As the telescopic section moves, the flexible connection section begins to bend to adapt to the change in the flow passage. 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. Figure 7 、 Figure 8 Referring to FIG. 6, the contraction flow passage back pressure adjustment process is as follows: in the initial state, the side walls are in the original position, the telescopic section is retracted to the shortest, and the flexible connection section has no deformation. If further reduction of the outlet area is required, the side wall slider is moved along the baffle groove, and the telescopic section is moved to the target diameter away from the center of the flow passage. In this process, the inner assembly slides downward relative to the outer assembly, and the rotating section is adjusted by rotating inward. As the telescopic section moves, the flexible connection section begins to bend to adapt to the change in the flow passage. 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.

[0065] Referring to FIG. 6, the contraction flow passage back pressure adjustment process is as follows: in the initial state, the side walls are in the original position, the telescopic section is retracted to the shortest, and the flexible connection section has no deformation. If further reduction of the outlet area is required, the side wall slider is moved along the baffle groove, and the telescopic section is moved to the target diameter away from the center of the flow passage. In this process, the inner assembly slides downward relative to the outer assembly, and the rotating section is adjusted by rotating inward. As the telescopic section moves, the flexible connection section begins to bend to adapt to the change in the flow passage. 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.

[0066] In other examples, the rotating section can also use multiple rotating small blades instead of a whole rotating section, and each small blade can rotate independently to adjust the shape of the flow passage. The telescopic section can also use elastic materials to change the length of the flow passage by stretching or compression. The flexible connection section can also use a flexible plate with a pre-bending line.

[0067] The outlet back pressure two-way adjustment device and method for planar cascade experiment has the following technical effects:

[0068] 1) Reducing gas flow loss: Through the design of double cubic curves and the flexible connection section, the invention can reduce the flow loss of the gas in the flow passage, improving the overall efficiency.

[0069] 2) Accurate adjustment of outlet area and back pressure: The design of the telescopic section and the manual adjustment of the slider enable the invention to accurately control the outlet area of the flow passage, thereby adjusting the back pressure to meet different working conditions.

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

[0071] 4) Convenient operation and maintenance: The side wall position is adjusted by manually moving the slider, which is simple to operate and easy to 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 simple to operate.

[0072] The above merely describes the preferred embodiments of the present application and is not intended to limit the present application. It should be pointed out that, for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present application, and these improvements and modifications should also be considered as falling within the protection scope of the present application.

Claims

1. A bidirectional adjustment device for outlet back pressure in a planar blade cascade experiment, characterized in that, Includes blade cascade connecting flange (1), baffle (2), and sidewall (3); The blade cascade connecting flange (1) is located at the bottom of the device and is arranged horizontally for connection with the outlet flange of the blade cascade test section; the two baffles (2) are arranged vertically and parallel, and their lower ends are fixedly connected to the blade cascade connecting flange (1); The sidewall (3) adopts a segmented structure, consisting of a rotating section (31), a flexible connecting section (32), and a retractable section (33). The retractable section (33) is connected to the rotating section (31) through the flexible connecting section (32). The rotating section (31) has a double cubic curve structure on both sides. The sidewall (3) is provided with a sidewall slider, and the baffle (2) is provided with a baffle channel; the sidewall slider includes a telescopic slider (335) and a rotating slider (311); the baffle channel includes a telescopic sliding channel (23) and a rotating sliding channel (22); The two sidewalls (3) are located between two parallel baffles, and the rotating section (31) at the lower end of the sidewalls contacts the flange edge of the blade connecting flange (1) to form a funnel-shaped flow channel. The sidewall slider is slidably connected to the baffle channel. When the rotating section (31) rotates with its starting point as the axis, the telescopic section (33) moves laterally and extends and retracts vertically, causing the flexible connecting section (32) to move and bend accordingly.

2. The bidirectional outlet back pressure adjustment device for planar blade cascade experiments according to claim 1, characterized in that, The blade connection flange (1) has slots (11) at its four corners. The baffle (2) is equipped with two pins (21) below it. The pins (21) slide into the corresponding slots (11) of the blade connection flange (1) and are fixedly connected to the blade connection flange (1) by bolts.

3. The bidirectional outlet back pressure adjustment device for planar blade cascade experiments according to claim 2, characterized in that, The retractable section (33) is nested from an inner retractable section component (331) and an outer retractable section component (332), and is used to realize the vertical extension and retraction of the assembly through the relative sliding of the inner retractable section component (331) and the outer retractable section component (332). The inner retractable section component (331) is provided with bolt holes (333), and the outer retractable section component (332) is provided with a sliding groove (334). The bolt passes through the bolt holes (333) and acts as a slider and plays a fixing role after the extension and retraction are completed.

4. The bidirectional outlet back pressure adjustment device for planar blade cascade experiments according to claim 3, characterized in that, The flexible connecting section (32) is made of rubber and can be bent and deformed for a smooth transition of the flow channel sidewall to reduce flow loss.

5. The bidirectional outlet back pressure adjustment device for planar blade cascade experiments according to claim 4, characterized in that, The shape and position of the rotating section sliding channel (22) correspond to the motion trajectory of the rotating section slider (311), and the shape and position of the telescopic section sliding channel (23) correspond to the motion trajectory of the telescopic section slider (335).

6. The bidirectional outlet back pressure adjustment device for planar blade cascade experiments according to claim 1, characterized in that, The rotating section uses bicubic curves of different shapes on both sides. One side profile is used for flow channel contraction to achieve pressure reduction and speed increase, while the other side profile can be used for flow channel expansion to achieve pressure increase and speed decrease.

7. A method for bidirectional adjustment of outlet back pressure using the device according to any one of claims 1 to 6, characterized in that, The process of regulating the back pressure of the constriction channel includes: 1) In the initial state, the sidewall is in its original position, the telescopic section is retracted to its shortest length, and the flexible connecting section is undeformed; 2) If it is necessary to further reduce the outlet area, move the sidewall slider along the baffle channel to move the telescopic section toward the center of the flow channel to the target diameter; 3) When the minimum exit area is reached, the retractable section is fully extended to its longest state to ensure that the exit area reaches the set minimum value.

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

9. The method for bidirectional adjustment of outlet back pressure according to claim 8, characterized in that, The back pressure regulation process of the expansion channel includes: (1) Exchange the positions of the two side walls so that the side walls are in the initial position under expansion. At this time, the telescopic section is shortened to its shortest length and the flexible connecting section is undeformed. (2) If it is necessary to further increase the outlet area, move the sidewall slider along the baffle channel 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 to ensure that the outlet area reaches the set maximum value.

10. The method for bidirectional adjustment of outlet back pressure according to claim 9, characterized in that, 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 to adjust the flow channel area. As the telescopic section moves, the flexible connecting section bends accordingly.

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