A diverging double-s-shaped inlet and exhaust passage structure and a design method thereof

Abstract

The application discloses a gradually expanding double-S-bend air inlet and exhaust channel structure and a design method thereof, and belongs to the field of aircraft design. The gradually expanding double-S-bend air inlet and exhaust channel structure comprises an air inlet channel, an exhaust channel and a gradually expanding skin fixed on a nacelle beam. The air inlet channel and the exhaust channel are respectively located on two sides of a control system and are communicated with the control system. The gradually expanding skin is conformal with the air inlet channel, the control system and the exhaust channel. The slope of the air inlet channel and the exhaust channel gradually decreases from large to small, and the area of the cross section of the air inlet channel and the exhaust channel along the path is relatively stable. The application guarantees that the airflow does not separate and backflow when deflecting in the internal pipeline, makes the performance of the S-bend air inlet channel in the envelope range relatively stable, makes the total pressure recovery coefficient relatively high, and makes the outlet distortion index in a small order of magnitude, thereby meeting the actual engineering requirements.

Description

Technical Field

[0001] This invention belongs to the field of electronic pod technology, and particularly relates to a gradually expanding double S-curve intake and exhaust duct structure and its design method. Background Technology

[0002] Electronic pods, as functional expansion compartments of aircraft, are usually suspended under the wings or belly of the aircraft. They have advantages such as flexible mounting and strong versatility. The intake and exhaust ducts serve as the "breathing ducts" of the pod's environmental control system. They are responsible for capturing, compressing, and rectifying the external ram air and introducing it into the pod's environmental control system. The system then uses the rear guide air to exhaust the air to the outside. Their structural and operational characteristics significantly affect the performance indicators of the environmental control system.

[0003] As the heat dissipation of electronic equipment inside the pod increases by orders of magnitude, the environmental control system inside the pod needs to introduce more ram air to increase the cooling capacity and thus solve the problem of high-density heat dissipation of the system. In the existing technology, such as CN200710304700.X, a backpack S-shaped air intake is proposed. Its diffuser centerline design adopts the centerline with the highest total pressure recovery coefficient between the front-fast and rear-slow centerline and the centerline with equal speed. The diffuser friction area variation law is taken as the centerline with the highest total pressure recovery coefficient between the front-fast and rear-slow friction area variation law and the front-fast and rear-slow friction area variation law. This design improves the aircraft's aerodynamic characteristics, increases the total pressure recovery coefficient, and reduces the steady-state distortion index. For example, CN202110628468.5 proposes an internal bulge S-curve inlet with an intermediate control section and a method thereof. The proposed internal bulge structure causes the airflow to undergo two reverse deflections inside the duct through the intermediate control section, achieving all-round shielding of the internal components of the inlet and the compressor blades. For example, CN202110461730.1 proposes a design method to improve the performance of a dorsal-mounted parallel twin-engine twin S-curve inlet. This design includes the design of the inlet position and the design of the inlet centerline. By optimizing various design points of the inlet, this invention has the advantages of taking into account the total pressure recovery coefficient and steady-state distortion index of the inlet.

[0004] Existing technologies focus on optimizing the structural characteristics of the intake duct itself to improve intake performance indicators such as total pressure recovery coefficient and steady-state distortion index. However, none of them take into account the actual limited space structure or how to adapt the performance to the exhaust requirements of the environmental control system. In other words, the existing technologies mentioned above have a limited scope of application in this field and are difficult to truly solve the high-density heat dissipation problem of the system. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies by providing a gradually expanding double S-bend intake and exhaust duct structure and its design method. This structure is compact, has a large intake air flow rate, a high total pressure recovery coefficient, and low aerodynamic resistance. The airflow velocity distribution within the intake and exhaust ducts is full and has strong anti-separation capability, ensuring that the airflow does not separate or backflow when deflected in the internal pipes. This results in relatively stable performance of the S-bend intake duct within its envelope, a high total pressure recovery coefficient, and a relatively small outlet distortion index, meeting practical engineering requirements. Furthermore, the intake and exhaust ducts are distributed at both ends of the energy conversion device of the environmental control system, facilitating disassembly and saving space.

[0006] The objective of this invention is achieved through the following technical solution:

[0007] A gradually expanding double S-curve intake and exhaust duct structure includes an intake duct, an exhaust duct, and a gradually expanding skin fixed to a pod beam. The intake duct and the exhaust duct are located on both sides of an environmental control system and are connected to the environmental control system. The gradually expanding skin is conformal to the intake duct, the environmental control system, and the exhaust duct.

[0008] The slope of the intake duct and the exhaust duct gradually decreases from large to small, and the area of ​​the cross-section of the intake duct and the exhaust duct is relatively uniform along the path.

[0009] In one embodiment, the air intake includes an air intake shroud and an air intake S-bend transition section, the exhaust includes an exhaust S-bend transition section and an exhaust shroud, and the expanding skin includes a first skin section conforming to the air intake and a third skin section conforming to the exhaust. The first skin section and the third skin section are connected by a second skin section. The ram air enters the air intake S-bend transition section through the air intake shroud, decelerates and is pressurized, then enters the environmental control system and is discharged through the exhaust shroud. Through this embodiment, the air intake, exhaust, and expanding skin are arranged in segments, reducing the space occupied by the air intake and exhaust ducts in the cabin. At the same time, installation and disassembly are convenient, greatly enhancing manufacturability and maintainability. Furthermore, the first skin section conforms to the air intake shroud of the air intake, while the third skin section conforms to the exhaust shroud of the exhaust. The second skin section between the first and third skin sections conforms to the environmental control system, effectively reducing the aerodynamic drag of the pod.

[0010] In one embodiment, the height of the exhaust port end of the exhaust hood is lower than the height of the intake port end of the intake hood. This embodiment increases the wake negative pressure effect, thereby increasing the descent volume of the pod and thus increasing the descent flow rate.

[0011] In one embodiment, the side of the gradually expanding skin away from the environmental control system has a streamlined outer contour, which further reduces the aerodynamic drag of the pod.

[0012] In one embodiment, the air intake hood and the air intake S-bend transition section, as well as the exhaust hood and the exhaust S-bend transition section, are all flexibly connected by rubber pads.

[0013] This invention also provides a design method for a gradually expanding double S-curve intake and exhaust duct structure, comprising:

[0014] Determine the shape parameters of the positioning sections for the inlet and outlet and the intermediate control sections;

[0015] The variation law of the constraint centerline and the variation law of the cross-sectional area along the friction;

[0016] Generate the centerline and the shape of the intermediate cross-section along the path;

[0017] If the design requirements are met, the shape of the intake and exhaust ducts will be output.

[0018] If the design requirements are not met, the centerline and the shape of the intermediate cross sections along the path will be regenerated.

[0019] The centerlines of the intake and exhaust ducts are distributed in a pattern of steep front and gentle rear, and the cross-sections of the intake and exhaust ducts are distributed with an area distribution of equal steepness and gentleness along the path.

[0020] In one embodiment, the centerlines of the intake and exhaust ducts are distributed in a manner that is steeper at the front and gentler at the back, including:

[0021]

[0022] Where Y is the longitudinal coordinate of the centerline of the intake and exhaust ducts, ΔY is the longitudinal offset of the intake and exhaust ducts, X is the abscissa of the centerline of the intake and exhaust ducts, L is the length of the intake and exhaust ducts, and A is the area of ​​the intermediate control section. Through this embodiment, the centerline of the intake and exhaust ducts is designed to determine the shape of the intake and exhaust ducts, so that the airflow does not separate or backflow when it deflects inside the intake and exhaust ducts.

[0023] In one embodiment, the intake and exhaust ducts have a relatively even area distribution along their cross-sections, including:

[0024]

[0025] Where X is the axial coordinate of the intake and exhaust ducts, L is the length of the intake and exhaust ducts, A1 is the inlet area of ​​the intake and exhaust ducts, and A2 is the outlet area of ​​the intake and exhaust ducts. Through this implementation method, the cross-sections of the intake and exhaust ducts adopt an area distribution with equal gradients, controlling the change of the flow diffusion ratio in the intake and exhaust ducts and avoiding airflow separation. This further ensures that the airflow does not separate or backflow when it deflects in the intake and exhaust ducts, making the performance of the S-curve intake duct within the envelope more stable, resulting in a higher total pressure recovery coefficient and a smaller outlet distortion index, which can meet the actual engineering requirements.

[0026] In one embodiment, a gradually expanding skin is provided and fixedly connected to the pod. The air intake, exhaust, and gradually expanding skin are separated into multiple parts and spliced ​​together. The air intake and exhaust are separated into a gradually expanding S-curve structure and a cover structure. The gradually expanding skin is sequentially separated into three skin structures along the direction from the air intake to the exhaust, which are respectively conformal to the air intake, conformal to the environmental control system, and conformal to the exhaust. Through this embodiment, the segmented layout structure reduces the space occupied by the air intake and exhaust in the cabin. At the same time, it is easy to install and disassemble, which greatly enhances manufacturability and maintainability. In conjunction with the gradually expanding skin, it can also effectively reduce the aerodynamic drag of the pod.

[0027] In one implementation, it further includes:

[0028] Wax models of intake and exhaust ducts are constructed using 3D printing;

[0029] The wax model is heated to form a casting cavity, and liquid metal is poured into the mold shell to form a casting blank. In this embodiment, the air intake and exhaust channels are manufactured by 3D printing wax model, investment casting, and then machining. This results in higher rigidity and strength, less deformation, a shorter casting production process, flexible design, saving time and economic costs, and reducing manufacturing difficulty.

[0030] The beneficial effects of this invention are as follows:

[0031] The gradually expanding double S-bend intake and exhaust structure provided by this invention is compact, has a large induced airflow, a high total pressure recovery coefficient, and low aerodynamic resistance. The airflow velocity distribution within the intake and exhaust ducts is full and has strong anti-separation capability, ensuring that the airflow does not separate or backflow when deflected within the internal duct. This results in relatively stable performance of the S-bend intake duct within its envelope, leading to a high total pressure recovery coefficient and a relatively small outlet distortion index, meeting practical engineering requirements. Furthermore, the intake and exhaust ducts are distributed at both ends of the energy conversion device of the environmental control system, facilitating disassembly and saving space. By designing the centerline of the gradually expanding double S-bend intake and exhaust ducts and the rate of change of the intake and exhaust duct area, airflow separation within the duct is avoided, improving the performance of the intake duct. Attached Figure Description

[0032] The invention will now be described in more detail with reference to embodiments and the accompanying drawings.

[0033] Figure 1 A schematic diagram of an embodiment of the present invention is shown;

[0034] Figure 2 A schematic diagram of another embodiment of the present invention is shown;

[0035] Figure 3 A flowchart of the design method of the present invention is shown;

[0036] In the accompanying drawings, the same parts use the same reference numerals. The drawings are not to scale.

[0037] Figure label:

[0038] 1-Pod body, 2-Intake hood, 3-Intake S-curve transition section, 4-Environmental control system, 5-Exhaust S-curve transition section, 6-Exhaust hood, 7-First skin section, 8-Second skin section, 9-Third skin section, 100-Intake duct, 200-Exhaust duct, 300-Gradually expanding skin. Detailed Implementation

[0039] The invention will now be further described with reference to the accompanying drawings.

[0040] This invention provides a gradually expanding double S-curve intake and exhaust duct structure, such as... Figure 1 As shown, it includes an air intake 100, an exhaust 200, and a gradually expanding skin 300 fixed to the pod beam. The air intake 100 and the exhaust 200 are located on both sides of the environmental control system 4 and are connected to the environmental control system 4. The gradually expanding skin 300 is conformal with the air intake 100, the environmental control system 4, and the exhaust 200.

[0041] Among them, the slope of the intake duct 100 and the exhaust duct 200 gradually decreases from large to small, and the area of ​​the cross section of the intake duct 100 and the exhaust duct 200 is relatively uniform.

[0042] It should be noted that, through research, the inventors discovered that the airflow velocity distribution in the front boundary layer of the intake duct 100 and exhaust duct 200 is full and has strong anti-separation capability, while the airflow quality in the latter half is poor and easily separated. That is, in this embodiment, the centerline design of the intake duct 100 and exhaust duct 200 adopts a centerline distribution that is sharp at the front and gentle at the back, as shown in the following equation:

[0043]

[0044] Where Y is the ordinate of the centerline of the intake duct 100 and the exhaust duct 200, ΔY is the longitudinal offset of the intake duct 100 and the exhaust duct 200, X is the abscissa of the centerline of the intake duct 100 and the exhaust duct 200, and L is the length of the intake duct 100 and the exhaust duct 200; the design of the centerline of the intake duct 100 and the exhaust duct 200 are both subject to the above equations. When designing the intake duct 100, Y is the ordinate of the centerline of the intake duct 100, ΔY is the longitudinal offset of the intake duct 100, X is the abscissa of the centerline of the intake duct 100, and L is the length of the intake duct 100. The exhaust duct 200 is designed in the same way, that is, the shape of the intake and exhaust ducts is determined by designing the centerline of the intake duct 100 and the exhaust duct 200.

[0045] Meanwhile, the inventors discovered that the area distribution of the intake duct 100 and exhaust duct 200 determines the change in the diffuser ratio of the flow direction within the pipe. The airflow is subject to inertial forces within the intake and exhaust pipes. If the area distribution is inappropriate, under the dual influence, the airflow is prone to separation within the pipe. Therefore, in this embodiment, the intake duct 100 and exhaust duct 200 adopt an area distribution with relatively equal gradients along their cross-sections, as shown in the following equation:

[0046]

[0047] Where X is the axial coordinate of the intake duct 100 and the exhaust duct 200, L is the length of the intake duct 100 and the exhaust duct 200, A1 is the inlet area of ​​the intake duct 100 and the exhaust duct 200, A2 is the outlet area of ​​the intake duct 100 and the exhaust duct 200, and A is the area of ​​the intermediate control section. The area distribution design of the intake duct 100 and the exhaust duct 200 both adopt the above equations. For example, when designing the intake duct 100, X is the axial coordinate of the intake duct 100, L is the length of the intake duct 100, A1 is the inlet area of ​​the intake duct 100, A2 is the outlet area of ​​the intake duct 100, and A is the cross-sectional area corresponding to the axial coordinate of the intake duct. The same applies to the exhaust duct 200.

[0048] In this embodiment, the intake and exhaust ducts and the environmental control system 4 are arranged in the middle section of the pod body 1. By designing the centerline of the gradually expanding double S-curve intake and exhaust ducts and the area change rate of the intake and exhaust ducts, it is ensured that the airflow does not separate or backflow when it deflects in the internal pipes. This makes the performance of the S-curve intake duct 100 within the envelope relatively stable, while also making the total pressure recovery coefficient high and the outlet distortion index at a small level, which can meet the actual engineering requirements. The total pressure recovery coefficient of the pod intake duct 100 is increased by 6.5%, and the bleed air volume is increased by 3.2%.

[0049] Specifically, such as Figure 2As shown, the intake duct 100 includes an intake hood 2 and an intake S-bend transition section 3, the exhaust duct 200 includes an exhaust S-bend transition section 5 and an exhaust hood 6, and the gradually expanding skin 300 includes a first skin section 7 conforming to the intake duct 100 and a third skin section 9 conforming to the exhaust duct 200. The first skin section 7 and the third skin section 9 are connected by a second skin section 8. The ram air enters the intake S-bend transition section 3 from the intake hood 2, decelerates and is pressurized, then enters the environmental control system 4 and is discharged from the exhaust hood 6.

[0050] It should be noted that in this embodiment, the air intake duct 100, the air outlet duct, and the gradually expanding skin 300 are arranged in segments, as follows: Figure 2 As shown, the intake duct 100 is bounded by section 0, with the intake shroud 2 at the left end and the intake S-bend transition section 3 at the right end. The exhaust duct 200 is bounded by section 3, with the exhaust S-bend transition section 5 at the left end and the exhaust shroud 6 at the right end. The gradually expanding skin 300 is bounded by the connection surfaces of the intake duct 100 and the environmental control system 4, and the connection surfaces of the exhaust duct 200 and the environmental control system 4. Figure 2 Sections 1 and 2 divide the gradually expanding skin 300 into three sections. The first skin section 7 is conformal with the air intake 100, and the third skin section 9 is conformal with the exhaust duct 200. This reduces the space occupied by the air intake and exhaust ducts in the cabin, while facilitating installation and disassembly, greatly enhancing manufacturability and maintainability. Furthermore, the first skin section 7 is conformal with the air intake hood 2 of the air intake 100, while the third skin section 9 is conformal with the exhaust hood of the exhaust duct 200. The second skin section 8 between the first skin section 7 and the third skin section 9 is conformal with the environmental control system 4, effectively reducing the aerodynamic drag of the pod.

[0051] In one embodiment, such as Figure 2 As shown, the height of the exhaust port end of the exhaust hood 6 is lower than the height of the air inlet end of the air inlet hood 2. That is, the height of the exhaust port end of the exhaust hood 6 protruding from the gradually expanding skin 300 is higher than the height of the air inlet end of the air inlet hood 2 protruding from the gradually expanding skin 300, which increases the wake negative pressure effect, realizes the improvement of the pod expedited air volume, and thus increases the expedited air flow.

[0052] In one embodiment, such as Figure 2 As shown, the side of the gradually expanding skin 300 away from the environmental control system 4 has a streamlined outer profile, which further reduces the aerodynamic drag of the pod.

[0053] In one embodiment, the outlet cross-sectional area of ​​the exhaust hood 6 is larger than the inlet cross-sectional area of ​​the intake hood 2, which facilitates the introduction and discharge of ram air.

[0054] In one embodiment, the air intake hood 2 and the air intake S-bend transition section 3, and the exhaust hood 6 and the exhaust S-bend transition section 5 are all softly connected by rubber pads.

[0055] This invention also provides a design method for a gradually expanding double S-curve intake and exhaust duct structure, such as... Figure 3 As shown, it includes the following steps:

[0056] Step S1: Determine the shape parameters of the positioning sections of the inlet and outlet and the intermediate control sections;

[0057] Step S2: The variation law of the constraint centerline and the variation law of the cross-sectional area along the friction;

[0058] Step S3: Generate the centerline and the shape of the intermediate cross section along the path;

[0059] Step S4: Determine whether the shape of the intake and exhaust ducts generated in step S3 meets the design requirements;

[0060] If the design requirements are met, the shape of the intake and exhaust ducts will be output.

[0061] If the design requirements are not met, return to step S3 to regenerate the intake and exhaust duct shape;

[0062] Among them, step S3 includes: the centerlines of the intake duct 100 and the exhaust duct 200 are distributed in a form that is steep at the front and gentle at the back, and the cross sections of the intake duct 100 and the exhaust duct 200 are distributed in an area with a relatively steep gradient.

[0063] In this design method, by designing the centerline of the gradually expanding double S-curve intake and exhaust duct and the rate of change of the intake and exhaust duct area, it is ensured that the airflow does not separate or backflow when it deflects in the internal duct, so that the performance of the S-curve intake duct 100 within the envelope is relatively stable, while the total pressure recovery coefficient is high and the outlet distortion index is at a small level, which can meet the actual engineering requirements.

[0064] Specifically, in step S3, the centerlines of the intake duct 100 and the exhaust duct 200 are distributed in a manner that is steeper at the front and gentler at the back, including:

[0065]

[0066] Where Y is the ordinate of the centerline of the intake duct 100 and the exhaust duct 200, ΔY is the longitudinal offset of the intake duct 100 and the exhaust duct 200, X is the abscissa of the centerline of the intake duct 100 and the exhaust duct 200, and L is the length of the intake duct 100 and the exhaust duct 200; when designing the intake duct 100, Y is the ordinate of the centerline of the intake duct 100, ΔY is the longitudinal offset of the intake duct 100, X is the abscissa of the centerline of the intake duct 100, and L is the length of the intake duct 100, and the exhaust duct 200 is designed in the same way; that is, the centerlines of the intake duct 100 and the exhaust duct 200 are designed to determine the shape of the intake and exhaust ducts so that the airflow does not separate or backflow when it deflects inside the intake and exhaust ducts.

[0067] Furthermore, in step S3, the intake duct 100 and exhaust duct 200 adopt an area distribution with relatively even gradients along their cross-sections, including:

[0068]

[0069] Where X represents the axial coordinate of the intake duct 100 and the exhaust duct 200, L represents the length of the intake duct 100 and the exhaust duct 200, A1 represents the inlet area of ​​the intake duct 100 and the exhaust duct 200, A2 represents the outlet area of ​​the intake duct 100 and the exhaust duct 200, and A represents the area of ​​the intermediate control section. When designing the intake duct 100, X represents the axial coordinate of the intake duct 100, L represents the length of the intake duct 100, A1 represents the inlet area of ​​the intake duct 100, and A2 represents the outlet area of ​​the intake duct 100. A represents the cross-sectional area corresponding to the axial coordinate of the intake duct, and the same applies to the exhaust duct 200. That is, the cross-sectional areas of the intake duct 100 and the exhaust duct 200 along the flow path adopt an area distribution with equal gradients, controlling the change in the flow direction diffusion ratio within the intake and exhaust ducts, and avoiding airflow separation. This further ensures that the airflow does not separate or backflow when it deflects within the intake and exhaust ducts, making the performance of the S-curve intake duct 100 within the envelope relatively stable, resulting in a high total pressure recovery coefficient and a small outlet distortion index, which can meet the actual engineering requirements.

[0070] Furthermore, the design method provided in this embodiment also includes:

[0071] Step S5: Set up the gradually expanding skin 300 that is fixedly connected to the pod, and separate the air intake 100, exhaust 200 and the gradually expanding skin 300 into multiple parts for splicing.

[0072] The intake duct 100 and exhaust duct 200 are separated into a gradually expanding S-curve structure and a cover structure. The gradually expanding skin 300 is sequentially separated into three skin sections along the direction from the intake duct 100 to the exhaust duct 200: one conformal to the intake duct 100, one conformal to the environmental control system 4, and one conformal to the exhaust duct 200. This segmented layout reduces the space occupied by the intake and exhaust ducts in the cabin, while also facilitating installation and disassembly, greatly enhancing manufacturability and maintainability. In conjunction with the gradually expanding skin 300, it can also effectively reduce the aerodynamic drag of the pod.

[0073] In one embodiment, a wax model of the intake and exhaust ducts is constructed using 3D printing;

[0074] The wax model is heated to form a casting cavity, and liquid metal is poured into the mold shell to form a casting blank. The air intake duct 100 and exhaust duct 200 are manufactured by 3D printing wax model, investment casting, and then machining. This makes them more rigid and stronger, with less deformation, and shortens the casting production process. The design is flexible, saves time and economic costs, and reduces manufacturing difficulty.

[0075] In the description of this invention, it should be understood that the terms "upper", "lower", "bottom", "top", "front", "rear", "inner", "outer", "left", "right", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention 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. Therefore, they should not be construed as limitations on this invention.

[0076] While the invention has been described herein with reference to specific embodiments, it should be understood that these embodiments are merely examples of the principles and applications of the invention. Therefore, it should be understood that many modifications can be made to the exemplary embodiments, and other arrangements can be designed without departing from the spirit and scope of the invention as defined by the appended claims. It should be understood that different dependent claims and features described herein can be combined in ways different from those described in the original claims. It is also understood that features described in conjunction with individual embodiments can be used in other described embodiments.

Claims

1. A gradually expanding double S-curve intake and exhaust duct structure, characterized in that, The system includes an air intake duct, an exhaust duct, and a gradually expanding skin fixed to the pod beam. The air intake duct includes an air intake hood and an air intake S-bend transition section. The exhaust duct includes an exhaust S-bend transition section and an exhaust hood. Both the air intake S-bend transition section and the exhaust S-bend transition section are S-bend diffuser pipe structures. The air intake duct and the exhaust duct are located on both sides of the environmental control system and are connected to the environmental control system. The gradually expanding skin includes a first skin section conforming to the air intake duct and a third skin section conforming to the exhaust duct. The first skin and the third skin are connected by a second skin section. The ram air enters the air intake S-bend transition section through the air intake hood, decelerates and is pressurized, then enters the environmental control system and is discharged through the exhaust hood. The gradually expanding skin is conforming to the air intake duct, the environmental control system, and the exhaust duct. The height of the exhaust hood's outlet end is lower than the height of the air intake end of the air intake hood. The slope of the intake and exhaust ducts gradually decreases from large to small along the airflow direction, and the centerline of the ducts follows... The air intake and exhaust manifolds are shaped in a gradual, progressive manner, with their cross-sections following a specific pattern. To achieve area changes with relatively uniform pace; Y is the ordinate of the centerline of the intake and exhaust ducts. Y represents the longitudinal offset of the intake and exhaust ducts, X represents the abscissa of the centerline of the intake and exhaust ducts, L represents the length of the intake and exhaust ducts, A1 represents the inlet area of ​​the intake and exhaust ducts, A2 represents the outlet area of ​​the intake and exhaust ducts, and A represents the area of ​​the intermediate control section.

2. The gradually expanding double S-curve intake and exhaust duct structure according to claim 1, characterized in that, The gradually expanding skin has a streamlined outer contour on the side away from the environmental control system.

3. The gradually expanding double S-curve intake and exhaust duct structure according to claim 1, characterized in that, The air intake hood and the air intake S-bend transition section, as well as the exhaust hood and the exhaust S-bend transition section, are all softly connected by rubber pads.

4. A design method for a gradually expanding double S-curve intake and exhaust duct structure as described in any one of claims 1 to 3, characterized in that, include: Determine the shape parameters of the positioning sections for the inlet and outlet and the intermediate control sections; The variation law of the constraint centerline and the variation law of the cross-sectional area along the friction; Generate the centerline and the shape of the intermediate cross-section along the path; If the design requirements are met, the shape of the intake and exhaust ducts will be output. If the design requirements are not met, the centerline and the shape of the intermediate cross sections along the path will be regenerated. in; The centerlines of the intake and exhaust ducts are distributed in a pattern of steep front and gentle rear, and the cross-sections of the intake and exhaust ducts adopt an area distribution with equal steepness and gentleness along the way.

5. The design method of a gradually expanding double S-curve intake and exhaust duct structure according to claim 4, characterized in that, The gradually expanding skin is fixedly connected to the pod. The air intake, exhaust and gradually expanding skin are separated into multiple parts and spliced ​​together. The air intake and exhaust are separated into a gradually expanding S-curve structure and a cover structure. The gradually expanding skin is separated sequentially along the direction from the air intake to the exhaust into three skin structures that are conformal to the air intake, conformal to the environmental control system and conformal to the exhaust.

6. The design method of a gradually expanding double S-curve intake and exhaust duct structure according to claim 4, characterized in that, Also includes: Wax models of intake and exhaust ducts are constructed using 3D printing; The wax model is heated to form a casting cavity, and liquid metal is poured into the mold shell to form a casting blank.

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