Semi-embedded type air inlet channel with steps

Abstract

The invention provides a semi-embedded type air inlet channel with a step. The semi-embedded type air inlet channel comprises an air inlet channel inner channel, a first air inlet channel flow guide face, a second air inlet channel flow guide face extending forwards from the first air inlet channel flow guide face, and a step part higher than the second air inlet channel flow guide face. The height of the upper surface of the step part is the same as that of the upper surface of the lip cover, so that an air inlet of the air inlet channel has no additional orthographic projection area, the stealth performance is improved, and the windward resistance is reduced; the groove which is gradually expanded towards the two sides from front to back is concavely formed in the step part, and the sweepback triangular wedge which is higher than the second air inlet channel flow guide surface is formed at the junction of the front end of the first air inlet channel flow guide surface and the second air inlet channel flow guide surface, so that high-quality incoming flow at the air inlet is ensured.

Description

Technical Field

[0001] The invention relates to the field of aircraft air inlet design, in particular to a subsonic semi-buried air inlet. Background Art

[0002] Subsonic aircraft are the most widely used type of air-breathing aircraft, and missiles are one of the main application scenarios of subsonic aircraft. The power system of subsonic aircraft usually uses the following three types of inlets: 1. Pitot inlet; 2. S-bend inlet; 3. Embedded inlet.

[0003] As the overall design of aircraft puts forward higher requirements on the additional resistance of subsonic air inlets and radar stealth performance, the Pitot-type air inlet is becoming increasingly difficult to meet the requirements. This has also led to the widespread use of S-curve air inlets and buried air inlets.

[0004] In subsonic aircraft, conventional S-bend air inlets have good aerodynamic performance, but their stealth effect is poor. Compared with embedded air inlets, conventional S-bend air inlets have obvious positive angle projection area (abbreviated as positive projection area), which is easy to form strong radar reflection waves, and the positive projection area will inevitably bring corresponding wind resistance. Embedded air inlets have no positive projection area, have higher stealth performance and lower wind resistance, but poor aerodynamic performance. Therefore, it is urgent to develop a new type of air inlet that combines the advantages of S-bend air inlet and embedded air inlet, so that it has both good aerodynamic performance and good stealth characteristics.

[0005] Please combine Figure 1 , Figure 2 The figure shows an S-bend air inlet in the prior art. The S-bend air inlet is an air inlet with an S-shaped internal pipe. It efficiently realizes the conversion of airflow kinetic energy into pressure energy through the ramming effect of high-speed incoming flow. Subsonic aircraft that commonly use a backpack S-bend air inlet need to design a boundary layer separator to partially or completely remove the boundary layer developed along the fuselage in order to reduce the interference of the boundary layer at the inlet inlet on the flow in the inlet pipe, that is, the air inlet needs to be lifted from the fuselage surface by a certain height. Therefore, the S-bend air inlet has a positive projection area, resulting in poor stealth performance and large wind resistance.

[0006] Please combine Figure 3 , Figure 4As shown, it is a buried air inlet in the prior art. The buried air inlet is a subsonic air inlet that integrates the inlet with the fuselage surface and buries the air inlet duct inside the fuselage. There is no protrusion on the fuselage surface. Since there is no positive projection area, it has the advantages of low headwind resistance and good stealth performance, and is convenient for missile box launch. However, the common buried air inlet cannot fully utilize the ramjet effect of the incoming flow to inlet air, and it is difficult to set up a boundary layer partition similar to the S-bend air inlet, so that a large amount of boundary layer developed along the fuselage is sucked into the inner flow channel, resulting in low performance of the buried air inlet. At present, in order to improve the performance of the buried air inlet for missiles, mechanical vortex generators are usually used to improve the performance of the air inlet. Although it can effectively improve the total pressure recovery coefficient and reduce the outlet total pressure distortion, the vortex generator not only brings a large additional resistance, but also has the risk of falling off.

[0007] Therefore, the S-curve air inlet has high aerodynamic performance but poor stealth performance, while the buried air inlet has good stealth performance but poor aerodynamic performance.

[0008] Please combine Figure 5 , Figure 6 As shown in the figure, there are studies on semi-buried air inlets, and the design principle is to combine buried air inlets with S-bend air inlets, trying to reconcile the contradiction between "aerodynamic performance" and "stealth performance". The specific implementation method is to add a lip protruding from the fuselage or the body of the missile to the buried air inlet, which on the one hand compresses the positive projection area compared to the conventional S-bend air inlet, and on the other hand can simultaneously use the side edge vortex of the buried air inlet and the high-speed airflow ramjet effect of the S-bend air inlet to achieve air intake.

[0009] It is obvious that this type of semi-buried air inlet still has a positive projection area, and its protruding surface will still bring wind resistance, so it has not completely achieved the two major goals of "reducing the positive projection area to zero" and "improving the air intake efficiency", and this air inlet solution is not conducive to the storage of missiles in the launch box. In addition, this type of semi-buried air inlet cannot be equipped with a boundary layer separator, so it will still inhale a large amount of boundary layer developed from the fuselage, and the aerodynamic performance is poor. If you want to improve performance, you still face the various additional disadvantages brought about by the use of mechanical vortex generators, just like the buried air inlet. Summary of the invention

[0010] To solve the above problems, the present invention provides a semi-buried air inlet with steps, the purpose of which is to reduce the windward resistance of the aircraft, improve the radar stealth performance of the aircraft, and effectively improve the total pressure recovery coefficient and flow field distortion index of the air inlet.

[0011] In order to achieve the above-mentioned purpose, the semi-buried air inlet with steps provided by the present invention can adopt the following technical solutions:

[0012] A semi-buried air inlet with a step, comprising an air inlet inner wall, side walls located on both sides of the air inlet inner wall, and lip covers located on the side walls on both sides, wherein the air inlet inner wall, the lip covers and the side walls on both sides together form an air inlet inner channel; a first air inlet guide surface and a second air inlet guide surface extending forward from the first air inlet guide surface are extended forward at the entrance of the air inlet inner channel, a step portion higher than the second air inlet guide surface is provided in front of the second air inlet guide surface; the height of the upper surface of the step portion is the same as the height of the upper surface of the lip cover;

[0013] The step portion is provided with a groove that gradually expands from the front to the rear and to both sides, the front end vertex of the groove is located at the center of the width of the step portion, and the rear end of the groove forms an expanded opening so that the bottom surface of the rear end of the groove and the second air inlet guide surface are located in the same plane;

[0014] A swept-back triangular wedge higher than the second air inlet duct guide surface is formed at the junction of the front end of the first air inlet duct guide surface and the second air inlet duct guide surface. The front end of the swept-back triangular wedge is a tip and extends obliquely backward from the tip to form an edge higher than the second air inlet duct guide surface.

[0015] Furthermore, the front end bottom surface of the groove is at the same height as the step portion at the vertex position, and the front end bottom surface of the groove is gradually recessed downward from the vertex so that the front end bottom surface of the groove forms an inclined surface that gradually sinks from front to back.

[0016] Furthermore, two side surfaces of the groove are arc-shaped surfaces that gradually expand outward, and the arc-shaped surfaces on both sides are symmetrically arranged.

[0017] Furthermore, the height of the step portion is higher than the height of the first air inlet guide surface.

[0018] Furthermore, the first air inlet guide surface is an arc-shaped surface extending and tilting downward from front to rear.

[0019] Furthermore, the inner channel of the air intake duct is an S-shaped inner channel of the air intake duct.

[0020] Furthermore, a line connecting the front end vertex of the groove and the tip of the swept-back triangular wedge coincides with a longitudinal section where the central axis of the inner channel of the air inlet is located.

[0021] Furthermore, the groove and the swept triangular wedge are used to exclude the boundary layer to both sides of the inlet.

[0022] Furthermore, the front end of the lip cover is triangular in shape so that the air inlet entrance is swept back.

[0023] Furthermore, the step portion is a part of the aircraft fuselage.

[0024] Beneficial effect: The present invention adopts a structure in which both sides of the groove gradually expand outward to generate vortices pointing to both sides of the second air inlet guide surface, and can effectively remove the boundary layer formed by the step portion and the boundary layer thickening or possible separation naturally formed by the height difference between the step portion and the second air inlet guide surface to both sides of the second air inlet guide surface, providing a uniform and high-quality airflow for the semi-buried air inlet. The swept-back triangular wedge and the groove jointly realize the removal of the air inlet boundary layer, ensuring high-quality incoming flow at the air inlet. At the same time, the height of the upper surface of the step portion is the same as the height of the upper surface of the lip cover, so that in the projection angle from the aircraft head to the rear, the air inlet will not appear in the projection angle under the full shielding of the step portion, that is, the air inlet has no additional positive projection area, thereby improving the stealth performance and reducing the windward resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a cross-sectional view of an S-bend air inlet in the prior art.

[0026] Figure 2 It is an axonometric diagram of an S-bend air inlet in the prior art.

[0027] Figure 3 It is an axonometric diagram of a buried air intake in the prior art.

[0028] Figure 4 It is a cross-sectional view of a buried air inlet in the prior art.

[0029] Figure 5 It is an axonometric diagram of a semi-buried air intake in the prior art.

[0030] Figure 6 It is a cross-sectional view of a semi-buried air intake in the prior art.

[0031] Figure 7 It is a simulation model diagram of the semi-buried air inlet with steps of the present invention.

[0032] Figure 8 It is an axonometric view of the semi-buried air inlet with steps of the present invention.

[0033] Fig. 9 It is a cross-sectional view of the semi-buried air inlet with steps of the present invention.

[0034] Fig.10 It is a top view of the semi-buried air inlet with steps of the present invention.

[0035] Fig.11 It is a velocity distribution cloud diagram on the symmetry surface obtained by simulating the semi-buried air inlet with steps of the present invention.

[0036] Fig.12It is a three-dimensional streamline diagram obtained by simulation of the semi-buried air inlet with steps of the present invention and emitted at a position 1 mm away from the body wall.

[0037] Fig.13 It is a three-dimensional streamline diagram emitted from the body wall surface obtained by simulating the semi-buried air inlet with steps of the present invention.

[0038] Fig.14 It is a map of the total pressure recovery coefficient at the inlet outlet obtained by simulating the semi-buried inlet with steps of the present invention. DETAILED DESCRIPTION

[0039] See also Figures 7 to 10 As shown, a semi-buried air inlet with steps includes an air inlet inner wall 8, side walls 5 located on both sides of the air inlet inner wall, and lip covers 3 located on the side walls on both sides. The air inlet inner wall 8, lip cover 3 and the side walls 5 on both sides together form an air inlet inner channel 4. In this embodiment, the air inlet inner channel 4 adopts the form of a conventional S-bend air inlet inner pipe, so that the air inlet inner channel 4 is buried inside the aircraft body when extending backward. The front end of the lip cover 3 is triangular in shape, so that the air inlet entrance is swept back, and the air inlet lip is also swept back. The sweep angle of the air inlet lip is determined according to its application scenario. Different sweep angles can be used when placed on different aircraft to enhance the stealth performance of the air inlet.

[0040] A first air intake guide surface 6 and a second air intake guide surface 2 extending forward from the first air intake guide surface 6 are provided at the entrance of the air intake inner passage. A step portion 7 higher than the second air intake guide surface 2 is provided in front of the second air intake guide surface 2, that is, the height of the step portion 7 is higher than the height of the first air intake guide surface 6. A groove 10 is provided in the step portion 7, which gradually expands from the front to the back and to both sides. The front end vertex of the groove 10 is located at the central position of the width of the step portion 7. The rear end of the groove 10 forms an expanded opening 12 so that the bottom surface of the rear end of the groove 10 and the second air intake guide surface 2 are located in the same plane. At the same time, a swept triangular wedge 11 higher than the second air intake guide surface 2 is formed at the junction of the front end of the first air intake guide surface 6 and the second air intake guide surface 2. The front end of the swept triangular wedge 11 is a tip and an edge 12 higher than the second air intake guide surface 2 is extended obliquely backward from the tip.

[0041] In order to achieve full shielding of the air inlet 1 of the semi-buried air inlet, that is, there is no additional orthographic projection area, in the present embodiment, the height of the upper surface of the step portion 7 is made the same as the height of the upper surface of the lip cover 3, so that in the projection angle from the head of the aircraft to the rear, the air inlet 1 will not appear in the projection angle due to the full shielding of the step portion 7, that is, the air inlet 1 has no additional orthographic projection area, thereby improving the stealth performance and reducing the windward resistance.

[0042] Combination Fig. 9 As shown in , the front end bottom surface of the groove 10 is at the same height as the step portion 7 at the vertex position, and the front end bottom surface of the groove 10 gradually sinks downward from the vertex so that the front end bottom surface of the groove 10 forms an inclined surface that gradually sinks from front to back, and the inclined surface is slightly curved in this embodiment. The two side surfaces of the groove 10 are arc-shaped surfaces that gradually expand outward until they expand into an opening 12, and the arc-shaped surfaces on both sides are symmetrically arranged.

[0043] In addition, the first air inlet guide surface 6 is an arc-shaped surface extending downward from the front to the back, that is, the air inlet 1 uses the ramming pressure of the incoming flow to intake air through the downwardly inclined first air inlet guide surface 6, so that the semi-buried air inlet has the characteristics of an S-bend air inlet. In addition, the bottom edge of the air inlet 1 and the first air inlet guide surface 6 are completely in contact, and there is no boundary layer partition that appears in the existing S-bend air inlet, which can effectively reduce the aerodynamic resistance of the aircraft and avoid the strong radar scattering echo formed by the existence of the boundary layer partition. The air inlet inner channel 4 adopts the conventional S-bend air inlet inner pipe form, thereby improving the performance parameters of the semi-buried air inlet and effectively improving the total pressure recovery coefficient and the total pressure distortion index.

[0044] The line between the front vertex of the groove 10 and the tip of the swept triangular wedge 11 coincides with the longitudinal section where the central axis of the inner channel of the air inlet is located; the groove 10 and the swept triangular wedge 11 are used to remove the boundary layer to the two sides of the inlet. Among them, the structure in which the two sides of the groove 10 gradually expand outward can generate vortices pointing to the two sides of the second air inlet guide surface 2, and can effectively remove the boundary layer formed by the step 7 and the boundary layer thickening or possible separation naturally formed by the height difference between the step 7 and the second air inlet guide surface 2 to the two sides of the second air inlet guide surface 2, so as to provide a uniform and high-quality airflow for the semi-buried air inlet 1. The swept triangular wedge 11 is placed on the second air inlet guide surface 2, and the boundary layer on the second air inlet guide surface 2 is naturally removed to the two sides of the air inlet side wall 5 through the two swept surfaces of the triangular wedge 6. Its height and swept angle and other dimensions can be determined according to the development of the boundary layer. The swept-back triangular wedge 6 and the groove 10 together realize the removal of the boundary layer of the air inlet duct, thereby ensuring high quality incoming flow at the air inlet 1 .

[0045] Please combine Fig.11 , Fig.12 , Fig.13 As shown, it is a simulation verification of the semi-buried air intake with steps described in this embodiment. Fig.11It can be seen that the boundary layer on the second air inlet guide surface 2 develops into the boundary layer on the first air inlet guide surface 6 after the action of the swept triangular wedge 11, and the boundary layer on the first air inlet guide surface 6 is obviously thinner than the boundary layer on the second air inlet guide surface 2, thereby ensuring the flow field quality at the air inlet 1. In addition, Fig.12 As can be seen in Figure 13, the vortex induced by the step portion can move the low-energy flow upstream of the inlet to both sides, thereby achieving the expected effect of eliminating the boundary layer of the inlet. Fig.14 It can be seen that through the analysis of the inlet outlet map, when the inlet Mach number is 0.7, the angle of attack is 2°, and the outlet Mach number is 0.57, the total pressure recovery coefficient at the inlet outlet reaches 0.96, which is significantly higher than the performance of the conventional embedded inlet under the same working conditions.

Claims

1. A semi-buried air inlet with a step, comprising an air inlet inner wall, side walls located on both sides of the air inlet inner wall, and lip covers located on the side walls on both sides, wherein the air inlet inner wall, the lip cover and the side walls on both sides together form an inner channel of the air inlet; characterized in that: A first air inlet guide surface (6) and a second air inlet guide surface (2) extending forward from the first air inlet guide surface (6) are provided at the entrance of the air inlet channel, and a step portion (7) higher than the second air inlet guide surface (2) is provided in front of the second air inlet guide surface (2); the height of the upper surface of the step portion (7) is the same as the height of the upper surface of the lip mask; The step portion (7) is provided with a groove (10) which gradually expands from the front to the rear and to both sides, the front end vertex of the groove (10) is located at the center of the width of the step portion, and the rear end of the groove forms an expanded opening so that the bottom surface of the rear end of the groove and the second air inlet guide surface (2) are located in the same plane; A swept-back triangular wedge (11) higher than the second air inlet duct guide surface (2) is formed at the junction between the front end of the first air inlet duct guide surface (6) and the second air inlet duct guide surface (2); the front end of the swept-back triangular wedge (11) is a tip and an edge (12) that is higher than the second air inlet duct guide surface (2) is extended obliquely backward from the tip.

2. The stepped semi-buried air inlet according to claim 1, characterized in that: The front end bottom surface of the groove (10) is at the same height as the step portion (7) at the vertex position, and the front end bottom surface of the groove (10) gradually sinks downward from the vertex so that the front end bottom surface of the groove (10) forms an inclined surface that gradually sinks from front to back.

3. The stepped semi-buried air inlet according to claim 1 or 2, characterized in that: The two side surfaces of the groove (10) are arc-shaped surfaces that gradually expand outwards, and the arc-shaped surfaces on both sides are symmetrically arranged.

4. The stepped semi-buried air inlet according to claim 1 or 2, characterized in that: The height of the step portion (7) is higher than the height of the first air inlet guide surface (6).

5. The stepped semi-buried air inlet according to claim 4, characterized in that: The first air inlet guide surface (6) is an arc-shaped surface extending and tilting downward from front to rear.

6. The stepped semi-buried air inlet according to claim 1, characterized in that: The inner channel of the air inlet duct is an S-shaped inner channel of the air inlet duct.

7. The stepped semi-buried air inlet according to claim 5, characterized in that: The line connecting the front end vertex of the groove (10) and the tip of the swept-back triangular wedge (11) coincides with the longitudinal section where the central axis of the inner channel of the air inlet is located.

8. The stepped semi-buried air inlet according to claim 7, characterized in that: The groove (10) and the swept triangular wedge (11) are used to exclude the boundary layer to both sides of the inlet.

9. The stepped semi-buried air inlet according to claim 1, characterized in that: The front end of the lip cover is triangular in shape, so that the inlet of the air inlet is swept back.

10. The stepped semi-buried air inlet according to claim 1, characterized in that: The step portion (7) is a part of the aircraft fuselage.

Images