Hypersonic air inlet weak jet transition control method

Abstract

The invention provides a control method for a weak jet flow transition of a hypersonic air inlet channel, and relates to the technical field of flow control of a hypersonic boundary layer. The method comprises the steps that jet flow holes used for achieving weak jet flow are formed in the compression face of the front edge of the air inlet channel, all the jet flow holes are distributed in a continuous and uniform zigzag array mode, and the jet flow holes communicate with a high-pressure air source through a connecting pipeline. The zigzag angle alpha and the zigzag spanwise wavelength lambda are designed according to a two-dimensional global stability analysis result of the air inlet channel compression flow field; a high-pressure air source used for generating disturbance is introduced from a pressurizing flow field behind the air inlet channel and is sprayed out from the zigzag jet holes; three-dimensional disturbance generated by the sawtooth-shaped jet holes can effectively trigger transition of an air inlet channel precursor boundary layer under the wide Mach number incoming flow condition, so that the boundary layer rapidly enters a turbulent flow state in front of an air inlet channel inlet, flow separation caused by reflection shock waves of an air inlet channel lip and interference of the boundary layer is restrained, the total pressure loss of the air inlet channel is reduced, and the service life of the air inlet channel is prolonged. The performance of the air inlet is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of hypersonic boundary layer flow control, and in particular to a hypersonic inlet weak jet transition control method. Background Art

[0002] Hypersonic inlets use shock waves or isentropic waves to compress the incoming flow, and there are complex shock wave / boundary layer interferences in the flow field, among which the most typical is the interference between the shock wave reflected by the inlet lip and the boundary layer on the inlet compression surface. Under different boundary layer flow states, the degree of interference between the shock wave and the boundary layer is significantly different: in laminar flow, the shock wave reflected by the lip can cause a large-scale flow separation in the boundary layer, which is harmful in the form of deterioration of the inlet performance and threat to flight safety; in turbulent flow, due to its strong pulsation characteristics, the flow separation caused by the shock wave / boundary layer interference can be effectively suppressed. In the past two decades, people have found through wind tunnel tests and flight tests that under the influence of background noise, strong shock waves, leading edge bluntness, etc., the forebody of an air-breathing hypersonic aircraft usually remains in a laminar state, making it difficult to achieve a natural transition, and artificial transition control must be performed in front of the inlet to obtain turbulence.

[0003] Artificial transition control is generally divided into two categories: passive control and active control. Vortex generators are a typical representative of passive control. For example, "diamond-shaped" vortex generators are used on the compression surfaces of the forebody of hypersonic aircraft such as X-43A, X-51A, HIFiRE-5, and Hyfly to force transition. From the research situation in the range of Mach numbers Ma=4 to 6, the vortex generator must reach an effective height (about 70% of the thickness of the boundary layer when Mach number Ma=6) to achieve efficient transition of the boundary layer, thereby generating a certain intensity of streamwise vortex, and using the rapid instability of the streamwise vortex to achieve the purpose of transition control. This transition mechanism has the following problems: a) The vortex generator cannot be adjusted with the change of the incoming flow conditions, especially under the condition of high Mach number incoming flow, it faces serious aerodynamic / thermal problems; b) The vortex generator will cause aerodynamic loss and generate additional resistance (obvious shock waves appear in the flow field), which will increase the displacement thickness of the boundary layer, thereby reducing the flow capture capacity, total pressure recovery and anti-backpressure capacity of the inlet; c) The peak value of the thermal flux of the vortex generator is at least one order of magnitude higher than that of the laminar flow, and the aerodynamic heating and heat protection problems are prominent. In order to prevent ablation under long-term flight conditions, high-temperature resistant materials are required. In addition, passive control is also sensitive to factors such as the leading edge radius of the aircraft, the incoming flow Mach number, environmental disturbances, wall temperature, compression corner, etc., and the robustness of transition control is poor.

[0004] Compared with passive control, the use of jet-controlled transition has the advantages of adjustable jet pressure, high transition efficiency, small interference with the flow field, and low thermal protection requirements. However, since a separate air supply system is required, including a high-pressure air source, pressure control system, power supply, etc., the complexity and weight of the system are increased, making it inconvenient for engineering applications.

[0005] Therefore, in order to solve the various problems existing in the current transition control technology, starting from the transition mechanism, an active transition control technology is studied which can be adaptively adjusted under a wide range of incoming flow conditions, has a simple structure, and does not require external energy input. This has important theoretical and engineering value for meeting the transition requirements of future air-breathing hypersonic vehicles. Summary of the invention

[0006] The purpose of the present invention is to provide a method for controlling weak jet transition in a hypersonic inlet, which can efficiently trigger the transition of the boundary layer of the hypersonic inlet while having the technical advantages of low resistance (reducing total pressure loss), low heat flow (reducing thermal protection pressure), self-adaptation (improving transition efficiency), and self-sealing (reducing system weight).

[0007] The present invention provides a method for controlling weak jet transition in a hypersonic inlet, comprising: arranging jet holes for realizing weak jet on a compression surface at a leading edge of the inlet, wherein each of the jet holes is arranged in a continuous and uniform zigzag array, and the jet holes are connected to a high-pressure gas source through a connecting pipe.

[0008] Preferably, the included angle between the axis of the jet hole and the compression surface of the air inlet is β, 0°<β≤90°, and the compression surface is concave or continuous wedge-shaped.

[0009] Preferably, the wavelength λ of the sawtooth wave formed by the center line of the jet holes is designed based on the most unstable wave parameter obtained by performing a two-dimensional global stability analysis on the compression surface of the air inlet.

[0010] Preferably, the angle α between the teeth of the sawtooth wave is 30° to 120°.

[0011] Preferably, the width of the sawtooth wave is the same as the spanwise width of the air inlet duct at the location, and the tip of a single sawtooth faces the incoming flow direction, and the axis of the single sawtooth is parallel to the incoming flow direction.

[0012] Preferably, the jet hole is a circular hole, and the hole diameter Φ thereof is 0.1 mm to 2 mm.

[0013] Preferably, the number of the jet holes on each oblique side of the sawtooth wave is not less than 3.

[0014] Preferably, the inlet of the high-pressure gas source is located in the boost flow field at the rear of the air intake duct, a pressure stabilizing chamber is arranged below the jet hole and below the inlet of the high-pressure gas source, and the connecting pipe is arranged in the pressure stabilizing chamber.

[0015] Preferably, the jet pressure ratio of the jet hole is Pjet / Ps<10.

[0016] The above control method is applicable to air-breathing hypersonic aircraft with a Mach number Ma≥4.5.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. By designing zigzag-shaped jet holes on the compression surface at the front side of the inlet, a three-dimensional disturbance wave is generated by the action of the zigzag jet. Theoretical and practical applications show that the three-dimensional disturbance wave can cause the boundary layer to quickly become unstable under the action of the concave compression surface of the inlet. At the same time, for a single jet hole, it will also generate a stream vortex of a certain intensity, and the stream vortex structure will also change the instability characteristics of the boundary layer. Therefore, considering the above factors, the three-dimensional disturbance wave and stream vortex are introduced through appropriate jet design, and the rapid transition of the boundary layer at the front side of the inlet can be achieved under the action of the compression surface of the inlet. At the same time, the pressure requirement for the jet can be greatly reduced, and efficient transition under weak jet conditions can be achieved.

[0019] 2. The zigzag weak jet transition control method of the present invention has the characteristics of low resistance and high efficiency: compared with various current passive transition controls and "I"-shaped active strong jet transition control, the zigzag arrangement of the jet holes can introduce three-dimensional disturbance waves in the hypersonic boundary layer. Under the joint action of the three-dimensional disturbance waves and the streamwise vortex, the demand for the jet pressure is reduced, the penetration depth of the jet into the mainstream is reduced, and the impact on the original flow field structure and performance of the inlet is reduced, and the aerodynamic loss and heat flow intensity are reduced while achieving efficient transition; therefore, the zigzag jet hole configuration design provides a good prerequisite for realizing transition control using a weak jet, and has the characteristics of low resistance and high efficiency compared with the "I"-shaped active strong jet transition control;

[0020] 3. The sawtooth weak jet transition control method of the present invention also has the characteristics of adaptability and self-sealing: compared with the conventional jet method currently using an independent air supply source system, on the one hand, the jet pressure of the weak jet is introduced from the boost flow field of the intake duct itself, and under wide-range incoming flow conditions, the jet pressure can be adaptively adjusted as the incoming flow conditions change, thereby enhancing the robustness of the transition control; on the other hand, since the air source is obtained from the boost flow field of the intake duct itself, there is no need for a complicated air supply system, pressure regulation system and external energy supply, and it can be achieved through a simple pipeline connection. Therefore, the system itself has a self-sealing characteristic, the system reliability is high, and at the same time it will not cause a significant increase in the weight of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 It is a schematic diagram of the position of the sawtooth-shaped jet hole of the present invention;

[0023] Figure 2 It is a schematic diagram of the arrangement and connection of the jet holes and the high-pressure gas source in the present invention;

[0024] Figure 3 It is a schematic diagram of the structure of the hypersonic dual air inlet in the present invention;

[0025] Figure 4 Schematic diagram of the boundary layer transition space vortex system structure triggered by the sawtooth weak jet of the present invention Figure 1 ;

[0026] Figure 5 Schematic diagram of the boundary layer transition space vortex system structure triggered by the sawtooth weak jet of the present invention Figure 2 ;

[0027] Figure 6 This is a structural diagram of a streamwise vortex pair similar to a Gothic vortex induced by the sawtooth-shaped weak jet of the present invention.

[0028] Description of reference numerals:

[0029] 1: air inlet; 101: compression surface; 2: jet hole; 3: high-pressure gas source; 4: connecting pipeline; 5: pressure stabilizing chamber. DETAILED DESCRIPTION

[0030] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicating directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as limiting the present invention.

[0032] In addition, the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "multiple" means two or more, unless otherwise clearly and specifically defined. In addition, the terms "installed", "connected" and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0033] like Figure 1-3 As shown, the present invention provides a method for controlling weak jet transition of a hypersonic inlet, comprising: arranging a jet hole 2 for realizing a weak jet on a compression surface 101 at a leading edge of an inlet 1, the jet hole 2 being a circular hole, each jet hole 2 being arranged in a continuous and uniform sawtooth array, and the jet hole 2 being connected to a high-pressure gas source 3 through a connecting pipe 4, and a wavelength λ of a sawtooth wave formed by a center line of the jet hole 2 on the surface of the compression surface 101 being designed according to the most unstable wave parameter obtained by performing a two-dimensional global stability analysis on the compression surface 101 of the inlet 1; the width of the sawtooth wave is the same as the width of the inlet 1 at the position, and the tip of a single sawtooth faces the incoming flow direction, the axis of the single sawtooth is parallel to the incoming flow direction, the angle between the axis of the jet hole 2 and the compression surface 101 of the inlet 1 is not greater than 90°, and the compression surface 101 is concave or continuously wedge-shaped.

[0034] By designing a zigzag-shaped jet hole 2 on the compression surface 101 on the front side of the inlet 1, a three-dimensional disturbance wave is generated by utilizing the sawtooth jet action. The three-dimensional disturbance wave can cause the boundary layer to quickly become unstable under the action of the concave compression surface or the multi-stage continuous wedge surface of the inlet 1. At the same time, for a single jet hole, it itself will also generate a stream vortex of a certain intensity, and the stream vortex structure will also change the instability characteristics of the boundary layer. The initial disturbance is formed by relying on the joint action of the three-dimensional disturbance wave and the stream vortex of the jet itself. The initial disturbance quickly becomes unstable under the action of the compression surface 101 of the inlet 1, causing a rapid transition of the boundary layer on the front side of the inlet, greatly reducing the pressure requirement for the jet, and realizing an efficient transition under weak jet conditions.

[0035] In this embodiment, the inlet of the high-pressure gas source 3 is located in the boost flow field at the rear of the intake duct 1, and a pressure stabilizing chamber 5 is arranged below the jet hole 2 and below the inlet of the high-pressure gas source 3, and the connecting pipe 4 is arranged in the pressure stabilizing chamber 5. The gas is introduced from the boost flow field of the intake duct itself, and under the wide-range incoming flow condition, the jet pressure can be adaptively adjusted with the change of the incoming flow condition, thereby enhancing the robustness of the transition control; on the other hand, since the gas source is obtained from the boost flow field of the intake duct itself, there is no need for a complex gas supply system, pressure regulation system and external energy supply, and it can be achieved through a simple pipeline connection, so the system itself has a self-sealing characteristic, the system reliability is high, and it will not cause a significant increase in the weight of the system.

[0036] The control method of the present invention is applicable to air-breathing hypersonic aircraft with a Mach number of Ma≥4.5. The design of the zigzag weak jet scheme directly determines the three-dimensional disturbance wave characteristics, including the shape of the jet hole, the aperture size, the arrangement mode (zigzag angle, spanwise wavelength), etc. The design parameter range is as follows:

[0037] Jet hole shape: round (or elliptical);

[0038] Jet hole diameter: Φ = 0.1mm ~ 2mm;

[0039] Sawtooth angle: α = 30° ~ 120°;

[0040] Span wavelength: λ = 1 ~ 16mm;

[0041] The number of jet holes on the sawtooth bevel: n≥3;

[0042] The angle between the center line of the jet hole and the wall: 0°<β≤90°.

[0043] The jet pressure ratio of the jet hole (i.e. the ratio of the jet pressure to the local static pressure): Pjet / Ps<10.

[0044] Under the following conditions of the Mach number of the incoming flow Ma=5, 6, according to the implementation method described above in this article, the size and installation position of the sawtooth jet hole of the present invention are determined.

[0045] The sawtooth span wavelength λ=8mm; the sawtooth angle α=90°; the jet hole diameter Φ=0.2mm; the distance s=40mm from the leading edge of the tip of the jet hole 2 to the leading edge of the air inlet 1, and three jet holes are arranged on each oblique side of the sawtooth, the jet hole 2 is perpendicular to the surface of the air inlet 1, and below the jet hole 2 is a pressure stabilizing chamber 5, and the high-pressure gas source 3 is introduced from the high-pressure flow field behind the air inlet 1 through the connecting pipeline 4 arranged in the pressure stabilizing chamber 5.

[0046] Under the above-mentioned design parameters of the zigzag weak jet orifice, the large eddy simulation results of the zigzag weak jet-triggered boundary layer transition are as follows: Figure 4-6 As shown, it can be seen that the large eddy simulation clearly reproduces the whole process of the sawtooth weak jet triggering the boundary layer transition, and gives the whole process of the occurrence and development of the vortex structure during the transition.

[0047] In summary, the sawtooth weak jet transition control method of the present invention can effectively trigger the transition of the hypersonic inlet boundary layer, causing the boundary layer to enter a turbulent state before the inlet entrance, thereby effectively suppressing the flow separation caused by shock wave / boundary layer interference, greatly improving the inlet performance, and the control method has a simple process and high reliability. It is a promising passive active hypersonic transition control technology with a wide range of scientific and technological uses.

[0048] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for controlling weak jet transition in a hypersonic inlet, characterized in that: include: Jet holes for realizing weak jet flow are arranged on the compression surface of the leading edge of the air inlet duct, each of the jet holes is arranged in a continuous and uniform zigzag array, and the jet holes are connected to the high-pressure gas source through a connecting pipe.

2. The hypersonic inlet weak jet transition control method according to claim 1, characterized in that: The included angle between the axis of the jet hole and the compression surface of the air inlet is β, 0°<β≤90°, and the compression surface is concave or continuous wedge-shaped.

3. The hypersonic inlet weak jet transition control method according to claim 1, characterized in that: The wavelength λ of the sawtooth wave formed by the center line of the jet holes is designed based on the most unstable wave parameter obtained by performing a two-dimensional global stability analysis on the compression surface of the air inlet.

4. The hypersonic inlet weak jet transition control method according to claim 3, characterized in that: The included angle α between the sawtooths of the sawtooth wave is 30° to 120°.

5. The hypersonic inlet weak jet transition control method according to claim 3, characterized in that: The width of the sawtooth wave is the same as the spanwise width of the air inlet duct at the position, and the tip of a single sawtooth faces the incoming flow direction, and the axis of the single sawtooth is parallel to the incoming flow direction.

6. The hypersonic inlet weak jet transition control method according to claim 1, characterized in that: The jet hole is a circular hole, and the hole diameter Φ thereof is 0.1 mm to 2 mm.

7. The hypersonic inlet weak jet transition control method according to claim 3, characterized in that: The number of the jet holes on each oblique side of the sawtooth wave is not less than 3.

8. The hypersonic inlet weak jet transition control method according to claim 1, characterized in that: The inlet of the high-pressure gas source is located in the boost flow field at the rear of the air intake duct, and a pressure stabilizing chamber is arranged below the jet hole and below the inlet of the high-pressure gas source, and the connecting pipe is arranged in the pressure stabilizing chamber.

9. The hypersonic inlet weak jet transition control method according to claim 1, characterized in that: The jet pressure ratio of the jet hole is Pjet / Ps<10.

10. The method for controlling the weak jet transition in a hypersonic inlet according to any one of claims 1 to 10, characterized in that: Suitable for air-breathing hypersonic aircraft with Mach number Ma≥4.5.

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