A stealth-enabled embedded air intake

Abstract

This invention belongs to the field of aircraft design technology and discloses an embedded air intake with stealth capabilities. It includes a forward air intake, side ridges, side ridge ramps, a rear lip, and a rear lip side plate. The front end of the forward air intake is directly and smoothly rounded to the aircraft surface. Side ridges are located on both sides of the forward air intake, extending rearward to smoothly connect with the rear lip. Both the side ridges and the rear lip are lower than the aircraft surface. The side ridges are connected to the aircraft surface via side ridge ramps, and the rear lip is connected to the aircraft surface via a rear lip side plate. The side ridges and rear lip of this invention employ unconventional, continuous, and smooth curvature designs. Both are located within the transverse cross-section envelope of the aircraft, simplifying the model generation process and avoiding the generation of new scattering sources. The use of two different ramps simplifies the inlet styling design, reduces the difficulty of air intake manufacturing, and can influence the rotation degree and inflow amount of the side ridge vortex.

Description

Technical Field

[0001] This invention belongs to the field of aircraft design technology, and relates to an air intake, specifically an embedded air intake with stealth capabilities. Background Technology

[0002] With the rapid development of military technology, high penetration capability has become a crucial element in aircraft design, and stealth design can significantly enhance this capability. Research indicates that aircraft with surface-like or planar shapes exhibit better stealth performance than those with conventional circular cross-sections. For aircraft air intakes, embedded air intakes offer lower drag, better stealth, and ease of box-launch and maintenance, attracting widespread attention from scholars both domestically and internationally.

[0003] Since embedded air intakes cannot directly utilize the incoming flow for ramming, side-edge vortices are often used to induce the mainstream flow into the intake. While these side-edge vortices enhance the intake capacity of embedded air intakes, they also increase the difficulty of organizing the flow field within the intake channel, making the design of high-performance embedded air intakes challenging. On the other hand, lip design is also one of the design difficulties of embedded air intakes. Some literature provides a smooth design method for continuous curvature of the lip of embedded air intakes, but the process is quite complex.

[0004] To address the aforementioned issues, this paper proposes an embedded air intake duct. The air intake duct lip takes into account the shape constraints of both the inner and outer channels, simplifying the design process and facilitating aerodynamic / stealth design of the air intake duct. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides an embedded air intake with stealth capabilities. The design is simple and easy to implement, and the designed air intake possesses both high aerodynamic performance and high stealth performance.

[0006] The technical solution of the present invention is as follows:

[0007] A stealth-enabled embedded air intake includes a forward air intake, side ridges, side ridge ramps, a rear lip, and a rear lip side plate. The front end of the forward air intake is directly and smoothly rounded to the surface of the aircraft. The two sides of the forward air intake are side ridges, which extend rearward to smoothly connect with the rear lip. The side ridges and the rear lip are both lower than the surface of the aircraft. The side ridges are connected to the surface of the aircraft through side ridge ramps, and the rear lip is connected to the surface of the aircraft through the rear lip side plate.

[0008] Furthermore, the forward airflow inlet extends obliquely downwards towards the aircraft surface, and the connection between the side edge and the forward airflow inlet is lower than the aircraft surface.

[0009] Furthermore, the posterior lip is triangular and serrated.

[0010] Furthermore, the acute angle of the triangular serrations on the rear lip is the same as the acute angle of the wing itself, pointing forward or backward.

[0011] Furthermore, the inclination angle of the posterior lip sideplate is less than 90°.

[0012] Furthermore, the depth of the side edge and rear lip below the aircraft surface is set according to the side edge vortex removal amount. The depth value of the side edge and rear lip below the aircraft surface ensures that the side edge vortex can be completely removed.

[0013] Furthermore, the side edge bevels and the aircraft surface are smoothly rounded to form the outer edge of the side edge, which is a straight edge.

[0014] Furthermore, the angle between the outer edge of the side edge and the aircraft's heading line is called the side edge angle, which is less than 10°.

[0015] The beneficial effects of this invention are as follows:

[0016] 1. The stealth-functional embedded air intake of the present invention adopts an unconventional curvature continuous smooth design for both the side edges and the rear lip. Both are located inside the transverse cross-section envelope of the aircraft, making the model generation process simple. Furthermore, the rear lip adopts a sawtooth design to avoid generating new scattering sources.

[0017] 2. The design of two different inclined plates simplifies the design concept of the inlet shape and reduces the difficulty of the intake duct manufacturing process. It can not only affect the rotation degree of the side vortex and the amount of side vortex entering, but also affect the direct radar wave illumination area.

[0018] 3. The above shows that the unconventional design of the inlet of the embedded air intake can improve the aerodynamic effect and stealth effect of the embedded air intake. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of this invention, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0020] Figure 1 This is a three-dimensional schematic diagram of the embedded air intake model of the present invention;

[0021] Figure 2 This is a partial enlarged schematic diagram of the inlet of the embedded air intake model of the present invention;

[0022] Among them, 1—the surface of the aircraft, 2—the forward guide port, 3—the side edge, 4—the side edge inclined plate, 5—the outer edge of the side edge, 6—the rear lip, 7—the rear lip side plate, and 8—the outer edge of the rear lip. Detailed Implementation

[0023] This section describes embodiments of the present invention, used to explain and illustrate the technical solutions of the present invention. Unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0024] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating directions or positional relationships, are given in the accompanying drawings and are used only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or device referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, features defined with "first," "second," etc., may explicitly or implicitly include more than one of those features. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integrated connection; they can refer to a mechanical connection or a point connection; they can refer to a direct connection or a connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] Figure 1 This is a magnified schematic diagram of the inlet portion of the embedded air intake model, which includes the aircraft surface 1, the forward air guide 2, the side ridge 3, the side ridge ramp 4, the outer edge of the side ridge 5, the rear lip 6, the rear lip side plate 7, and the outer edge of the rear lip 8.

[0027] from Figure 1 As can be seen, a stealth-enabled embedded air intake 3 mainly includes an inlet, an outlet, and a channel connecting the inlet and outlet. The inlet of the embedded air intake mainly includes a forward guide port 2, a side ridge 3, and a rear lip 6. The forward guide port 2 of the embedded air intake is directly and smoothly rounded to the surface of the aircraft.

[0028] Side ridge 3 is a straight edge located inside the transverse cross-section envelope of the aircraft (below the aircraft surface), parallel to the outer edge 5 of the side ridge. It is connected to the surface of the aircraft by a side ridge ramp 4. To ensure the existence of the side ridge ramp 4, its tilt angle is less than 90°. When the side ridge ramp 4 works with the outer edge 5 of the side ridge, it weakens the right-angle reflection between the outer edge 5 of the side ridge and the inner channel, directly reducing the scattering area of ​​lateral radar waves on the air intake surface, and affecting the rotation degree of the vortex generated by the outer edge 5 of the side ridge. The tilt angle of the side ridge ramp 5 should not be too large, as an excessively large angle will increase the difficulty of demolding during the conventional production of the air intake.

[0029] The side ridge plate 4 is directly and smoothly rounded to the surface of the aircraft to form the outer edge 5 of the side ridge. The outer edge 7 of the side ridge is a straight edge with an angle of less than 10° to the longitudinal section. When the side ridge angle is greater than 0°, the entrainment vortex of the side ridge angle is enhanced as the side ridge angle increases, but an excessively large side ridge angle (8.5°) will lead to excessive airflow mixing loss, resulting in a decrease in the total pressure recovery performance of the inlet. [Reference: Sun Shu, Guo Rongwei, Selection and experimental verification of inlet surface parameters of planar embedded inlet [J]. Acta Aeronautica Sinica. 2005.26(3)].

[0030] The rear lip 6 is serrated and located inside the longitudinal section envelope of the aircraft (below the aircraft surface), avoiding direct radar wave illumination. The number of serrations is unlimited, and the acute angle of the serration protrusion is equivalent to the acute angle of the two wings 2 of the aircraft. The rear lip 8 has no straight edges, avoiding direct radar wave illumination and preventing the generation of new dihedral scattering sources when radar waves illuminate it.

[0031] The connection between the rear lip 6 and the aircraft surface is achieved through a transitional overlap using the rear lip side plate 7. The tilt angle of the rear lip side plate 7 is unlimited (maximum 90°, to avoid direct radar illumination and exclude boundary layer interference). Its tilt degree affects not only the amount of side edge vortex rejection but also the area directly illuminated by radar waves. According to Chapter 3 of *Sang Jianhua. Aircraft Stealth Technology [M]. Aviation Industry Press, Beijing, 2013*, if the radar polarization direction of the trailing edges of the wing, horizontal stabilizer, and vertical stabilizer is parallel to the trailing edge, the trailing edge diffraction echo is not sensitive to the trailing edge thickness, and the polarization formula can provide satisfactory results. Based on this, the applicant has also designed the rear lip 6 of the air intake accordingly, and theoretically, corresponding calculation results can also be obtained.

[0032] The rear lip side plate 7 is directly and smoothly rounded to the surface of the aircraft to form the outer edge 8 of the rear lip. This unconventional design of the embedded air intake improves its aerodynamic / stealth performance. The tilt angle of the rear lip side plate 7 is less than 90°, which not only reduces direct radar wave reflection but also affects the amount of vortex removal from the outer edge 5. Airflow over the outer edge 5 inevitably generates side vortexes, which, as the airflow develops and reaches the rear lip side plate 7, affect the removal of these vortexes. However, when the depth of the rear lip side plate 7 is sufficient, the side vortexes can be completely removed.

[0033] This invention designs a baseline prototype embedded air intake and a new embedded air intake, and compares their RCS performance using three-dimensional numerical simulation. An incident wave with a wavelength of 3.33 cm was selected to compare the mean RCS values ​​of the two embedded air intakes at a 5° angle of attack; the results are shown in Table 1. Simulation results demonstrate that the design intent proposed in this invention is well realized, and the aerodynamic performance of the embedded air intake design is significantly improved compared to the baseline prototype design.

[0034] Table 1. Performance comparison between the baseline prototype embedded air intake and the embedded air intake of this invention (obtained from simulation experiments).

[0035]

[0036] As can be seen from the table, after adopting the solution of the present invention, within the 30°RCS mean, the HH polarization is 97% of the reference prototype, while the VV polarization is only 65% ​​of the reference prototype, showing a significant effect.

[0037] This invention is applicable to various aircraft with stealth capabilities.

[0038] There are many specific methods and approaches to implement this invention. The above description is merely a preferred embodiment of this invention. The core idea of ​​this invention is still the design where the opening surface of the air intake is entirely located within the envelope of the aircraft's transverse cross-section. For those skilled in the art, several improvements can be made without departing from the principle of this invention, and these improvements should also be considered within the scope of protection of this invention. All components not explicitly stated in this embodiment can be implemented using existing technologies.

Claims

1. A concealed air intake with stealth capabilities, characterized in that, It includes a front airflow guide (2), a side ridge (3), a side ridge ramp (4), a rear lip (6), and a rear lip side plate (7). The front end of the front airflow guide (2) is directly and smoothly rounded to the surface of the aircraft (1). The two sides of the front airflow guide (2) are side ridges (3), which extend backward to smoothly connect with the rear lip (6). The side ridges (3) and the rear lip (6) are both lower than the surface of the aircraft (1). The side ridges (3) are connected to the surface of the aircraft (1) through the side ridge ramp (4), and the rear lip (6) is connected to the surface of the aircraft (1) through the rear lip side plate (7). The forward guide port (2) extends downwards at an angle to the aircraft surface (1), and the connection between the side ridge (3) and the forward guide port (2) is lower than the aircraft surface (1). The depth of the side ridge (3) and the rear lip (6) below the aircraft surface (1) is set according to the amount of vortex removal from the side ridge. The depth values ​​of the side ridge (3) and the rear lip (6) below the surface of the aircraft surface (1) ensure that the vortex from the side ridge can be completely removed.

2. The embedded air intake with stealth function according to claim 1, characterized in that, The posterior lip (6) is triangular and serrated.

3. The embedded air intake with stealth function according to claim 2, characterized in that, The acute angle of the triangular serrations of the rear lip (6) is the same as the acute angle of the wing itself forward or backward.

4. The embedded air intake with stealth function according to claim 1, characterized in that, The inclination angle of the posterior lip side plate (7) is less than 90°.

5. A concealed air intake with stealth function according to claim 1, characterized in that, The side edge inclined plate (4) and the aircraft surface (1) are smoothly rounded to form the side edge outer edge (5), and the side edge outer edge (5) is a straight edge.

6. A concealed air intake with stealth function according to claim 5, characterized in that, The angle between the outer edge of the side edge (5) and the aircraft's heading line is the side edge angle, which is less than 10°.

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