An air inlet passage air flow optimization system based on boundary layer internal circulation and an aircraft

Abstract

The application belongs to the technical field of air inlet design, and particularly relates to an air inlet airflow optimization system based on boundary layer internal circulation and an aircraft. The system comprises at least one flow leakage slot arranged on the surface of the aircraft body upstream of the air inlet inlet; an injection pipeline embedded in the aircraft body, the inlet of the injection pipeline being communicated with the flow leakage slot, the outlet end of the injection pipeline extending to the inside of the main flow channel of the special-shaped air inlet and being located in the pressure gradient area of the outer side wall of the first bend; and the outlet of the injection pipeline is configured as a porous array structure for atomizing the low-energy flow and spraying the low-energy flow into the high-speed main flow of the main flow channel in a tangential manner. The application realizes omnidirectional low detectability, optimizes the aerodynamic performance and realizes internal circulation of energy, and has compact structure and strong applicability.

Description

Technical Field

[0001] This application belongs to the field of air intake design technology, and specifically relates to an air intake airflow optimization system and aircraft based on boundary layer internal circulation. Background Technology

[0002] The dorsal-mounted, irregularly shaped air intake is a key feature of modern low-observable aircraft, significantly reducing the radar cross-section of the engine fan through physical shielding. However, this configuration also presents significant aerodynamic challenges. The intake is directly embedded in the fuselage, allowing low-energy boundary layer flow from the fuselage surface to directly enter it. This low-energy flow is highly susceptible to flow separation when experiencing complex pressure gradient changes within the irregularly shaped duct, leading to distortion of the total intake pressure. In severe cases, this can trigger engine surge or shutdown, threatening flight safety.

[0003] In existing technologies, aircraft often use boundary layer diverters to physically isolate the boundary layer of the fuselage. However, this structure creates a strong radar reflective surface, which is detrimental to low observability design. Another approach is to directly exhaust the boundary layer airflow, but this requires opening exhaust ports on the fuselage surface, which also compromises the aircraft's low observability and creates new radar and infrared signal sources.

[0004] Therefore, existing technologies lack an effective solution to fundamentally solve the boundary layer problem of dorsal irregular air intakes without compromising the shape of the aircraft. There is an urgent need for an integrated system that can capture, transport, and convert low-energy flow in the boundary layer internally. Summary of the Invention

[0005] To address the aforementioned issues, this application provides an inlet airflow optimization system and aircraft based on boundary layer internal circulation. This system can convert harmful low-energy boundary layer flow into usable intake air through internal circulation without relying on external exhaust or compromising the aircraft's shape. This effectively suppresses flow separation, reduces intake distortion, and improves engine operational stability.

[0006] The first aspect of this application provides an inlet airflow optimization system based on boundary layer internal circulation, mainly comprising:

[0007] At least one venting slot is opened on the surface of the engine body upstream of the air intake;

[0008] An ejector pipe embedded inside the body has its inlet connected to the venting seam, and its outlet extends into the main channel of the irregularly shaped air intake, located in the pressure gradient region on the outer wall of the first bend.

[0009] The outlet of the ejector channel is constructed as a porous array structure to atomize the low-energy flow and inject it tangentially into the high-speed mainstream of the main channel.

[0010] Preferably, the opening of the venting slot smoothly transitions to the skin, and a concave cavity with an increased inner diameter is provided inside. The concave cavity is constructed as a low-detectability structure that guides radar waves to reflect and attenuate multiple times within the cavity through its geometric shape.

[0011] Preferably, the extension direction of the seam forms an acute angle with the airflow direction on the body surface at the seam joint.

[0012] Preferably, the internal flow channel of the ejector pipe includes a Venturi effect acceleration section, which has a streamlined profile that first contracts and then expands, to increase the flow velocity through the low-energy flow and enhance the suction capacity of the venting slot.

[0013] Preferably, the injection direction of the porous array structure forms an angle of 10° to 45° with the tangent direction of the inner wall of the main channel at the connection with the porous array structure.

[0014] Preferably, the included angle is set to 20°.

[0015] Preferably, a pre-swirl guide vane is integrated upstream of the porous array structure to generate a swirling component in the outflowing airflow that is consistent with the mainstream direction of the irregularly shaped air intake.

[0016] The second aspect of this application provides an aircraft equipped with an inlet airflow optimization system based on boundary layer internal circulation as described above.

[0017] This application achieves omnidirectional low detectability, optimizes aerodynamic performance and internal energy circulation, and features a compact structure and strong applicability. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the working principle of a preferred embodiment of the inlet airflow optimization system based on boundary layer internal circulation in this application.

[0019] Figure 2 This is a magnified schematic diagram of a portion of the effluent gap.

[0020] Figure 3 This is a schematic diagram of the ejector pipe structure.

[0021] Figure 4 This is a schematic diagram of a multi-pore array structure with micro-pores.

[0022] Figure 5 This is a schematic diagram of the pre-swirling guide vane structure inside a micro-orifice.

[0023] Among them, 1-fuselage surface, 2-irregular air intake, 3-exhaust slit, 31-slit opening, 32-cavity, 4-ejector pipe, 41-Venturi effect acceleration section, 5-multi-hole array structure, 51-micro-hole, 52-pre-swirl guide vane. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below with reference to the accompanying drawings. In the drawings, the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The described embodiments are only some, not all, of the embodiments of this application. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain this application, and should not be construed as limiting this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application. The embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0025] The first aspect of this application provides an inlet airflow optimization system based on boundary layer internal circulation, such as... Figures 1-5 As shown, it mainly includes:

[0026] At least one venting slit 3 is opened on the surface of the engine body upstream of the air intake;

[0027] The ejector pipe 4, which is embedded inside the body, has its inlet connected to the venting slot 3, and its outlet extends into the main channel of the irregular air intake duct 2, and is located in the pressure gradient region on the outer wall of the first bend.

[0028] The outlet of the ejector pipe 4 is constructed as a porous array structure 5, which is used to atomize the low-energy flow and inject it tangentially into the high-speed mainstream of the main channel.

[0029] In this application, as Figure 1 As shown, the vent 3 is located on the fuselage surface upstream of the inlet of the inlet, for example, 1.5 to 2 characteristic lengths upstream of the leading edge of the inlet of the inlet 2, to capture the low-energy boundary layer flow before it enters the inlet's influence zone. The inlet of the ejector duct 4 is connected to the vent 3, and its outlet extends into the main channel of the inlet, precisely located along the pressure gradient region on the outer wall of the curved section of the inlet. The porous array outlet structure 5 is located at the outlet of the ejector duct 4, used to atomize the collected low-energy flow into multiple fine jets, which are then injected tangentially into the high-speed mainstream of the main channel.

[0030] In some alternative embodiments, the opening 31 of the venting slot 3 smoothly transitions to the skin, and a recessed cavity 32 with an increased inner diameter is provided inside. The recessed cavity 32 is constructed as a low-detectability structure that guides radar waves to be reflected and attenuated multiple times within the cavity through its geometry.

[0031] refer to Figure 2The vent 3 is not vertically oriented; its opening 31 smoothly transitions to the aircraft surface. In some alternative embodiments, the extension direction of the opening 31 forms an acute angle with the airflow direction on the aircraft surface at the junction of the opening 31, in order to reduce interference with the incoming flow and its own radar reflection characteristics. Its interior is designed with a special cavity 32, which guides the reflection and attenuation of incident radar waves through its geometry, improving the aircraft's low-observable performance.

[0032] The venting slot 3 is connected to the inlet of the ejector pipe 4 embedded inside the machine body, and the ejector pipe 4 is connected to the outlet of the multi-hole array, such as... Figure 3 As shown. The ejector duct 4 extends inward close to the outer wall of the intake duct. In some alternative embodiments, the internal flow channel of the ejector duct 4 includes a Venturi effect acceleration section 41, which has a streamlined profile that first contracts and then expands, used to increase the flow velocity of the low-energy flow and enhance the suction capacity of the vent slot, so that the flow velocity is significantly increased when the low-energy flow passes through its throat.

[0033] The outlet end of the ejector duct 4 penetrates the wall of the irregularly shaped air intake duct 2, enters its main flow channel, and terminates precisely at the outer wall of the first bend of the air intake duct. This location is a region of pressure gradient in the airflow, with high main flow velocity and low static pressure, which can generate a strong natural ejection (suction) effect.

[0034] like Figure 4 As shown, the outlet of the ejector tube 4 is processed into a porous array structure 5. This panel is densely covered with dozens to hundreds of micro-holes 51. (As shown...) Figure 5 As shown, a tiny pre-swirl vane 52 is optionally installed upstream of each micro-orifice 51. In some alternative embodiments, the injection direction of the porous array structure 5 forms an angle of 10° to 45° with the tangential direction of the inner wall of the main channel at the connection with the porous array structure 5. In particular, the angle is set to 20°, and this outlet design is intended to achieve fine control of the airflow.

[0035] System working principle as follows Figure 1 As shown, in flight, the low-energy boundary layer flow A from the fuselage surface is captured by the venting slot 3 and enters the ejector sleeve 4, forming an inner boundary layer flow B. Under the combined action of the Venturi effect acceleration section 41 and the high-speed, low-pressure zone of the main air intake channel, the low-energy flow is accelerated and transported to the porous array panel 5. Here, the low-energy flow is broken down into smaller jets, atomized into numerous fine jets D through micro-holes 51, and obtains a swirling component aligned with the main air intake C under the action of the pre-swirling guide vanes 52. These fine jets D are injected tangentially into the high-speed main air intake, where they are rapidly sheared, entrained, and completely merged, resulting in a significant energy boost. This allows them to be smoothly delivered to the engine, completely avoiding large-scale flow separation within the air intake and effectively reducing total pressure distortion.

[0036] The second aspect of this application provides an aircraft equipped with an inlet airflow optimization system based on boundary layer internal circulation as described above.

[0037] Compared with the prior art, the beneficial effects of this application include:

[0038] 1. Achieved omnidirectional low detectability: The entire boundary layer processing is completed inside the aircraft, with no mission-functional openings on the surface of the fuselage, fundamentally eliminating the resulting increase in radar scattering and maintaining the overall shape of the aircraft very well.

[0039] 2. Achieved optimized aerodynamic performance and internal energy circulation: This application does not simply exclude low-energy flow, but through ingenious design, it transports it to the region with the highest energy for regeneration and fusion. This eliminates the harm of the boundary layer, recovers the quality of this airflow, slightly increases the intake flow rate, and achieves a leap from exhaust gas treatment to recycling, thus optimizing the overall aerodynamic efficiency.

[0040] 3. High efficiency and reliability: Utilizing the main energy of the intake duct itself as power, the system requires no additional complex actuation mechanisms or energy sources. It operates passively, ensuring high reliability. Through multi-hole array atomization and tangential injection, the mixing process between the low-energy flow and the main energy flow is ensured to be smooth and efficient, without inducing new flow distortions.

[0041] 4. Compact structure and strong applicability: The system is integrated into the existing air intake and airframe structure, without taking up extra space, making it particularly suitable for use on compact aircraft.

[0042] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. An inlet airflow optimization system based on boundary layer internal circulation, characterized in that, include: At least one venting slit (3) is opened on the surface of the engine body upstream of the air intake. The ejector pipe (4) buried inside the body has its inlet connected to the venting slot (3), and its outlet extends into the main channel of the irregular air intake (2) and is located in the pressure gradient region of the outer wall of the first bend. The outlet of the ejector pipe (4) is constructed as a porous array structure (5) for atomizing low-energy flow and injecting it tangentially into the high-speed mainstream of the main channel.

2. The inlet airflow optimization system based on boundary layer internal circulation according to claim 1, characterized in that, The opening (31) of the venting slit (3) is smoothly transitioned to the skin, and a cavity (32) with an increased inner diameter is provided inside it. The cavity (32) is constructed as a low-detectability structure that guides radar waves to be reflected and attenuated multiple times within the cavity through its geometric shape.

3. The inlet airflow optimization system based on boundary layer internal circulation according to claim 2, characterized in that, The extension direction of the seam (31) forms an acute angle with the airflow direction on the body surface at the junction of the seam (31).

4. The inlet airflow optimization system based on boundary layer internal circulation according to claim 1, characterized in that, The internal flow channel of the ejector pipe (4) includes a Venturi effect acceleration section (41) which has a streamlined profile that first contracts and then expands, used to increase the flow velocity of the low-energy flow and enhance the suction capacity of the venting slot.

5. The inlet airflow optimization system based on boundary layer internal circulation according to claim 1, characterized in that, The injection direction of the porous array structure (5) forms an angle of 10° to 45° with the tangential direction of the inner wall of the main channel at the connection with the porous array structure (5).

6. The inlet airflow optimization system based on boundary layer internal circulation according to claim 5, characterized in that, The included angle is set to 20°.

7. The inlet airflow optimization system based on boundary layer internal circulation according to claim 1, characterized in that, The porous array structure (5) has a pre-swirl guide plate (52) integrated upstream, which is used to generate a swirling component in the outflow airflow that is consistent with the mainstream direction of the irregular air intake (2).

8. An aircraft, characterized in that, It is equipped with an inlet airflow optimization system based on boundary layer internal circulation as described in any one of claims 1 to 7.

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