A high-dimensional twist inlet passage design method based on waveguide high-order mode loss

Abstract

The application belongs to the field of aircraft inlet design, and particularly relates to a high-dimensional twist inlet design method based on waveguide high-order mode loss. The method comprises the following steps: high-dimensional twist and gradient gradual change design are performed on the throat of the inlet to improve the high-frequency electromagnetic wave energy loss of the inlet; the throat of the inlet is designed into an S-shaped curve to increase the reflection times of electromagnetic waves in the inlet; the inlet comprises a lip section, a throat section and a terminal section which are connected in sequence; the throat section has a gradually changed width-height ratio; and the throat section is a two-section double-S-shaped curve. According to the throat of the aircraft inlet, the throat of the inlet is designed and shaped in combination with domestic and foreign technical foundations, the two-section double-S-shaped throat with high-frequency twist is designed based on the waveguide high-order mode loss theory, the scattered electromagnetic waves are transmitted and lost at the same time, the high-frequency RCS is significantly reduced, the reflection times of electromagnetic waves in the inlet are increased, the backward echo is reduced, and the low-detectable performance of the aircraft in the head direction is effectively improved.

Description

Technical Field

[0001] This application belongs to the field of aircraft air intake design, and specifically relates to a high-dimensional twisted air intake design method based on waveguide high-order mode loss. Background Technology

[0002] The air intake is a crucial component of an aircraft, constrained by both its aerodynamic performance and its low-observable capability. As one of the aircraft's strongest scattering sources, the low-observable design of the air intake plays a vital role in the overall low-observable design. Electromagnetic waves entering through the intake lip, after passing through the throat and reaching the terminal surface, will return along their path, causing a sharp deterioration in the aircraft's low-observable performance. Low-observable treatment of the air intake can significantly reduce the aircraft's scattering characteristics, thus benefiting its low-observable design. However, current research lacks theoretical frameworks for designing the observable performance of air intakes.

[0003] Therefore, it is desirable to have a technical solution to overcome or at least mitigate one of the aforementioned defects of the prior art. Summary of the Invention

[0004] The purpose of this application is to provide a high-dimensional twisted air intake design method based on waveguide high-order mode loss, so as to solve at least one problem existing in the prior art.

[0005] The technical solution of this application is:

[0006] A high-dimensional twisted inlet design method based on waveguide high-order mode loss includes:

[0007] By employing high-dimensional twisting and gradient design on the intake throat, the energy loss of high-frequency electromagnetic waves in the intake is improved.

[0008] By designing the intake throat in an S-shape, the number of times electromagnetic waves are reflected within the intake is increased.

[0009] In at least one embodiment of this application, the air intake includes a lip section, a throat section, and a terminal section connected in sequence.

[0010] In at least one embodiment of this application, the throat segment has a gradually changing aspect ratio.

[0011] In at least one embodiment of this application, the throat segment is a two-segment double S-curve, and the throat segment extends from the first end connected to the lip segment to the second end connected to the terminal segment, with the axial height gradually decreasing and then increasing again.

[0012] In at least one embodiment of this application, the height of the first end axis of the throat segment is higher than the height of the second end axis.

[0013] In at least one embodiment of this application, the arithmetic mean of the cephalic ±30° angular region of the throat segment changes with the relative curvature in the following trend: decreasing, increasing, decreasing, increasing.

[0014] In at least one embodiment of this application, the lip segment adopts a triangular mouth face design.

[0015] In at least one embodiment of this application, the terminal segment is cylindrical.

[0016] The invention has at least the following beneficial technical effects:

[0017] The high-dimensional twisted air intake design method based on waveguide high-order mode loss proposed in this application has significantly improved low detectability performance, while realizing the loss of high-frequency electromagnetic waves, which is beneficial to the design of air intake throats of aircraft with low detectability performance. Attached Figure Description

[0018] Figure 1 This is a front view of a high-dimensional twisted air intake based on waveguide high-order mode loss according to one embodiment of this application;

[0019] Figure 2 This is a top view of a high-dimensional twisted air intake based on waveguide high-order mode loss according to one embodiment of this application;

[0020] Figure 3 This is a left view of a high-dimensional twisted air intake based on waveguide high-order mode loss according to one embodiment of this application;

[0021] Figure 4 This is a schematic diagram comparing the horizontal polarization RCS of the 9GHz intake duct before and after applying the reduction technology in one embodiment of this application;

[0022] Figure 5 This is a schematic diagram comparing the vertical polarization RCS of the 9GHz intake duct before and after applying the reduction technology in one embodiment of this application. Detailed Implementation

[0023] 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 some, but not all, 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.

[0024] In the description of this application, it should be understood that the terms "center", "longitudinal", "lateral", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", 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 application 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 limiting the scope of protection of this application.

[0025] The following is in conjunction with the appendix Figures 1 to 5 This application will be described in further detail.

[0026] This application provides a high-dimensional twisted inlet design method based on waveguide high-order mode loss, including:

[0027] By employing high-dimensional twisting and gradient design on the intake throat, the energy loss of high-frequency electromagnetic waves in the intake is improved.

[0028] By designing the intake throat in an S-shape, the number of times electromagnetic waves are reflected within the intake is increased.

[0029] This application discloses a high-dimensional twisted inlet design method based on waveguide high-order mode loss. The inlet includes a lip section, a throat section, and a terminal section connected sequentially. In a preferred embodiment, the throat section has a gradually changing aspect ratio. The throat section is a two-segment double S-bend, with its axial height gradually decreasing and then increasing from the first end connected to the lip section to the second end connected to the terminal section. The axial height of the first end of the throat section is higher than that of the second end. The arithmetic mean of the throat section in the ±30° head-direction angular region decreases—increases—decreases—increases—considering the impact of the inlet lip on low detectability performance, a triangular mouth face design is preferred for the lip section. In this embodiment, the terminal section is cylindrical.

[0030] The high-dimensional twisted inlet design method based on waveguide higher-order mode loss proposed in this application, in its first aspect, achieves high-frequency throat twist loss design. Specifically, for high frequencies, a design approach of high-dimensional throat twisting and large-range gradient impedance is adopted. This design allows changes in the polarization and transmission characteristics of electromagnetic waves within the throat under finite aspect ratio constraints, and induces oscillation absorption of higher-order modes. Experimental results show that the energy loss of high-frequency electromagnetic waves passing through the throat increases by 6–10 dB.

[0031] In addition to the high-dimensional twisted intake design method based on waveguide high-order mode loss, this application also implements a two-section double S-bend throat design. The throat section of the intake is designed as an S-bend. The purpose of this is to increase the number of reflections of electromagnetic waves within the intake after they reach the end face of the terminal section through the throat, thereby reducing back echoes.

[0032] The high-dimensional twisted air intake design method based on waveguide high-order mode loss proposed in this application addresses the issue that the conventional back-mounted S-curve air intake has an up-and-down bending method, meaning the air intake is higher than the bottom of the air intake. The bending method and relative curvature have a significant impact on the scattering of the S-curve air intake.

[0033] The relative curvature is defined as follows: k = d / D, where d is the lateral distance between the air intake and the bottom surface of the air intake duct, and D is the diameter of the air intake duct. When k = 0, the air intake duct is a straight cylinder, and electromagnetic waves can directly reach the bottom surface of the air intake duct; when k = 1, electromagnetic waves incident along the axis of the air intake duct will not reach the bottom surface of the air intake duct.

[0034] Generally speaking, for various aircraft, the ±30° head-up angle range is the key attitude angle and the area where the aircraft is most threatened. Therefore, the arithmetic mean of the ±30° head-up angle can reflect the low detectability performance of the air intake to a certain extent.

[0035] The forward mean (±30°) changes with relative camber in a W-shaped pattern, decreasing-increasing-decreasing-increasing. When the relative camber is zero, the forward mean is relatively large. As the relative camber increases, the forward mean decreases, reflecting the RCS reduction effect of the intake duct bending measure. When the relative camber increases to a certain extent, the forward mean reaches a minimum and stops decreasing, instead increasing. This indicates that a larger relative camber does not necessarily lead to better reduction. Under horizontal polarization, a relative camber of 0.6 reaches a minimum, indicating the best reduction effect; under vertical polarization, a relative camber of 0.4 also reaches a minimum, indicating the best reduction effect. The forward mean then reaches a maximum after increasing to a certain extent, and then decreases again with increasing relative camber. The relative camber at which the maximum value is reached is 1 under horizontal polarization and 0.8 under vertical polarization. When the relative camber is 1.4, the forward mean again reaches a minimum under both vertical and horizontal polarization, lower than the previous mean.

[0036] This application presents a high-dimensional twisted air intake design method based on waveguide high-order mode loss. The air intake structure designed according to this method is as follows: Figure 1-3 As shown. For the high-frequency band, the relationship between the parameters of the intake throat and the RCS reduction characteristics is studied, and the intake model is simulated and optimized to maximize the loss effect of the throat on high-frequency electromagnetic waves.

[0037] This application presents a high-dimensional twisted inlet design method based on waveguide high-order mode loss, such as... Figure 4-5 As shown, the back-mounted intake throat designed in the above manner achieved a 7.89dB reduction in the 9GHz normalized horizontal polarization RCS and a 7.93dB reduction in the vertical polarization RCS, which greatly reduced the high-frequency scattering of the intake.

[0038] This application presents a high-dimensional twisted air intake design method based on waveguide high-order mode loss. The physical structure of the air intake is similar to a metal waveguide cavity. Mature metal waveguide cavity theory can be used to describe the scattered energy distribution inside the air intake. By controlling the reflected energy inside the air intake, low detectability performance design is achieved. This application focuses on the throat of an aircraft air intake. Combining domestic and international technological foundations, it designs and modifies the air intake throat. Based on waveguide high-order mode loss theory, it realizes a high-frequency twisted two-section double S-bend throat design, achieving simultaneous transmission and loss of scattered electromagnetic waves, significantly reducing high-frequency RCS, and increasing the number of electromagnetic wave reflections within the air intake to reduce back echoes, effectively improving the low detectability performance of the aircraft in the head-on direction.

[0039] 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. A design method for a high-dimensional twisted air intake based on waveguide high-order mode loss, characterized in that, include: By employing high-dimensional twisting and gradient design on the intake throat, the energy loss of high-frequency electromagnetic waves in the intake is improved. By designing the intake throat in an S-shape, the number of times electromagnetic waves are reflected within the intake is increased. The air intake includes a lip section, a throat section, and a terminal section connected in sequence; The throat segment has a gradually changing aspect ratio; The throat segment is a two-segment double S-curve. The throat segment extends from the first end connected to the labial segment to the second end connected to the terminal segment, with the axial height gradually decreasing and then increasing again. The height of the first end axis of the throat segment is higher than the height of the second end axis. The arithmetic mean of the cephalic ±30° angular region of the throat segment changes with the relative curvature in the following trend: decreasing, increasing, decreasing, increasing.

2. The high-dimensional twisted inlet design method based on waveguide high-order mode loss according to claim 1, characterized in that, The lip segment adopts a triangular mouth face design.

3. The high-dimensional twisted inlet design method based on waveguide high-order mode loss according to claim 2, characterized in that, The terminal segment is cylindrical.

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