A double-wall afterburner vibration-proof screen with multiple frequency absorption

Abstract

This application belongs to the field of aero-engine design, and it is a double-layer wall afterburner vibration-proof screen with multiple absorption frequencies, including a coaxially arranged afterburner casing, an outer vibration-proof screen, and an inner vibration-proof screen; when the afterburner is operating, different modes of combustion pulsation are generated through structural changes, and a structure of two Helmholtz absorption cavities is formed through the outer absorption holes opened on the outer vibration-proof screen and the inner absorption holes opened on the inner vibration-proof screen; when the inner absorption holes correspond to the wall surface of the outer vibration-proof screen, the height of its absorption cavity is the spacing "H1" between the double-layer vibration-proof screens, and the corresponding volume is "V1", which can have an obvious absorption effect on the pulsation of frequency f1; when the absorption holes of the inner vibration-proof screen correspond to the angular position of the absorption holes of the outer vibration-proof screen, the absorption cavity is approximately extended, and the height of the absorption cavity is "H1 + H2", which can have an obvious absorption effect on the pulsation of frequency f2.

Description

Technical Field

[0001] The present application belongs to the field of aero-engine design, and in particular relates to a double-wall afterburner anti-vibration screen with multiple frequency absorption. Background Art

[0002] The afterburner is an important component of military aircraft engines. It can increase engine thrust in a short period of time and improve the acceleration and maneuverability of the aircraft. As a low-pressure component for ignition and combustion organization of aircraft engines, the afterburner is prone to combustion pulsation during the combustion process. In severe cases, it will develop into oscillating combustion, which will endanger the hardware structure. Its generation is related to the coupling of the inherent sound field mode of the afterburner itself and the heat release of the afterburner, and its mechanism is relatively complex. In order to reduce the impact of afterburner pulsation, an anti-vibration screen is usually set in the afterburner. Through its porous thin-walled structure, it forms a combination structure similar to the Helmholtz vibration absorption cavity with the casing to absorb the pulsation.

[0003] With the development of aircraft engine afterburner combustion chambers, their structural changes have brought about changes in inherent sound field modes, fuel atomization, oil droplet evaporation, ignition combustion, turbulent mixing, flame stabilizer vortex shedding, etc. These will cause afterburner combustion to produce combustion pulsations of different modes, and generally produce pulsations in multiple frequency bands at the same time, increasing the risk of use.

[0004] Traditional aircraft engine afterburner anti-vibration screens are mostly single-layer porous thin-walled structures. Their structural characteristics determine that they can only actively absorb pulsations of a certain frequency by adjusting the openings, but have no obvious inhibitory effect on pulsations in other frequency bands. They can no longer meet the needs of advanced aircraft engine afterburner for multi-frequency band pulsation absorption. Summary of the invention

[0005] The purpose of the present application is to provide a double-wall afterburner anti-vibration screen with multiple frequency absorption, so as to solve the problem that the existing afterburner of an aircraft engine cannot absorb pulsation in multiple frequency bands.

[0006] The technical solution of the present application is: a double-layer wall afterburner vibration-proof screen with multiple absorption frequencies, comprising a coaxially arranged afterburner casing, an outer vibration-proof screen and an inner vibration-proof screen; the outer vibration-proof screen is arranged between the inner vibration-proof screen and the combustion chamber casing, an outer cooling channel is formed between the outer vibration-proof screen and the afterburner casing, and a high-temperature inner channel is formed on the inner vibration-proof screen; the outer vibration-proof screen is provided with outer vibration-absorbing holes, the inner vibration-proof screen is provided with inner vibration-absorbing holes, and the inner vibration-proof screen is provided with inner vibration-absorbing holes. The number of holes is greater than the number of external vibration absorbing holes, a part of the internal vibration absorbing holes are arranged radially corresponding to the external vibration absorbing holes, and another part of the internal vibration absorbing holes are arranged corresponding to the wall surface of the outer anti-vibration screen, a first vibration absorbing cavity is formed between the outer anti-vibration screen and the inner anti-vibration screen, and a second vibration absorbing cavity is formed between the inner anti-vibration screen and the afterburner casing; an anti-vibration screen bracket is connected between the outer anti-vibration screen and the afterburner casing, and an anti-vibration screen support ring is connected between the outer anti-vibration screen and the inner anti-vibration screen.

[0007] Preferably, the outer vibration absorbing holes have the same diameter as the inner vibration absorbing holes, and the number of the inner vibration absorbing holes is twice the number of the outer vibration absorbing holes.

[0008] Preferably, the anti-vibration screen bracket is arranged at the front and rear ends of the outer anti-vibration screen, and multiple groups of the anti-vibration screen bracket are arranged at intervals along the circumference of the outer anti-vibration screen. Each group of the anti-vibration screen brackets has a trapezoidal structure and the side of the anti-vibration screen bracket with a larger width is connected to the outer anti-vibration screen.

[0009] Preferably, the axial length of the outer vibration-proof screen is greater than the axial length of the inner vibration-proof screen, the vibration-proof screen support ring is arranged at the front end and the rear end of the inner vibration-proof screen, the vibration-proof screen support ring is arranged as a wavy circular ring structure along the circumferential direction, and the vibration-proof screen support ring forms a stepped structure along the axial direction.

[0010] Preferably, the diameter of the outer vibration absorbing hole is smaller than the diameter of the inner vibration absorbing hole.

[0011] The present invention discloses a multi-frequency absorbing double-wall afterburner vibration-proof screen, comprising a coaxially arranged afterburner casing, an outer vibration-proof screen and an inner vibration-proof screen; when the afterburner is working, combustion pulsations of different modes are generated through structural changes, and two types of Helmholtz vibration-absorbing cavity structures are formed through outer vibration-absorbing holes opened on the outer vibration-proof screen and inner vibration-absorbing holes opened on the inner vibration-proof screen; when the inner vibration-absorbing holes correspond to the wall surface of the outer vibration-proof screen, the vibration-absorbing cavity height is the double-layer vibration-proof screen spacing "H 1 ”, the corresponding volume is “V 1 ”, can be used to 1 The pulsation of the frequency has an obvious absorption effect; when the vibration absorption holes of the inner anti-vibration screen correspond to the vibration absorption holes of the outer anti-vibration screen in angular position, the vibration absorption cavity is approximately extended, and the height of the vibration absorption cavity is "H 1 +H 2”, can be used to 2 The pulsation of frequency has a significant absorption effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solution provided by the present application, the following is a brief introduction to the accompanying drawings. Obviously, the accompanying drawings described below are only some embodiments of the present application.

[0013] Figure 1 This is a schematic diagram of the overall structure of this application;

[0014] Figure 2 This is a schematic diagram of the cross-sectional structure of the anti-vibration screen of this application;

[0015] Figure 3 This is a schematic diagram of the arrangement structure of the external vibration absorption holes of this application;

[0016] Figure 4 This is a schematic diagram of the arrangement structure of the vibration absorbing holes in this application;

[0017] Figure 5 This is a schematic diagram of the cooling gas circulation structure of the anti-vibration screen of this application.

[0018] 1. Afterburner casing; 2. Outer anti-vibration screen; 3. Inner anti-vibration screen; 4. Anti-vibration screen support ring; 5. Anti-vibration screen bracket; 6. Outer vibration absorption hole; 7. Inner vibration absorption hole. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solutions and advantages of the implementation of this application clearer, the technical solutions in the embodiments of this application will be described in more detail below in conjunction with the drawings in the embodiments of this application.

[0020] A double-wall afterburner chamber vibration-proof screen with multiple absorption frequencies is provided. By setting the distance between the double-walls and the distance design of the casing wall, the double-wall vibration-proof screen and the casing wall together form two combined structures similar to the Helmholtz vibration-absorbing cavity, which can absorb pulsations of two frequency bands generated by afterburner combustion.

[0021] like Figure 1-2 As shown, it includes a coaxially arranged afterburner casing 1, an outer anti-vibration screen 2 and an inner anti-vibration screen 3; the outer anti-vibration screen 2 is arranged between the inner anti-vibration screen 3 and the combustion chamber casing, an external cooling channel is formed between the outer anti-vibration screen 2 and the afterburner casing 1, and the inner side of the inner anti-vibration screen 3 is a high-temperature internal channel.

[0022] Combination Figure 3-4The outer vibration-absorbing holes 6 are opened on the outer vibration-absorbing screen 2, and the inner vibration-absorbing holes 7 are opened on the inner vibration-absorbing screen 3. The number of the inner vibration-absorbing holes 7 is greater than the number of the outer vibration-absorbing holes 6. A part of the inner vibration-absorbing holes 7 is arranged radially corresponding to the outer vibration-absorbing holes 6, and the other part of the inner vibration-absorbing holes 7 is arranged corresponding to the wall surface of the outer vibration-absorbing screen 2. A first vibration-absorbing cavity is formed between the outer vibration-absorbing screen 2 and the inner vibration-absorbing screen 3, and a second vibration-absorbing cavity is formed between the inner vibration-absorbing screen 3 and the afterburner casing 1.

[0023] An anti-vibration screen bracket 5 is connected between the outer anti-vibration screen 2 and the afterburner casing 1 , and an anti-vibration screen support ring 4 is connected between the outer anti-vibration screen 2 and the inner anti-vibration screen 3 .

[0024] Combination Figure 5 When the afterburner is working, different modes of combustion pulsation are generated through structural changes. The outer vibration absorption holes 6 opened on the outer vibration-proof screen 2 and the inner vibration absorption holes 7 opened on the inner vibration-proof screen 3 form two types of Helmholtz vibration absorption cavity structures. The corresponding vibration absorption frequency can be calculated by formula (1):

[0025]

[0026] Where f is the Helmholtz vibration absorption frequency, Hz; c is the local sound speed, m / s; S is the neck or opening cross-sectional area, m 2 ; L is the length of the neck, m; d is the diameter of the neck or opening, m; V is the volume of the cavity, m 3 .

[0027] When the inner vibration absorbing hole 7 corresponds to the wall surface of the outer anti-vibration screen 2, the height of the first vibration absorbing cavity is equal to the distance "H" between the double-layer anti-vibration screens. 1 ”, the corresponding volume is “V 1 According to formula (1), the vibration absorbing cavity can The pulsation has a significant absorption effect.

[0028] When the vibration absorbing holes of the inner vibration-proof screen 3 correspond to the vibration absorbing holes of the outer vibration-proof screen 2 in angular position, the second vibration absorbing cavity is approximately extended, and the height of the second vibration absorbing cavity is "H 1 +H 2 ”, where H2 is the distance between the outer anti-vibration screen 2 and the afterburner casing 1, and the volume of the second vibration absorbing cavity is “V 2 According to formula (1), the vibration absorbing cavity can The pulsation has a significant absorption effect.

[0029] By adjusting the thickness of the double-walled anti-vibration screen, the wall spacing, the aperture of the opening, the distance from the afterburner casing 1, the opening rate and other parameters, the two main frequency band pulsations in the afterburner can be actively absorbed at the same time, thereby reducing the impact of the afterburner pulsation and effectively avoiding the occurrence of afterburner oscillation combustion.

[0030] The anti-vibration screen bracket 5 can be connected to the afterburner casing 1 and the outer anti-vibration screen 2 by welding or the like, and the anti-vibration screen support ring 4 can be connected to the outer anti-vibration screen 2 and the inner anti-vibration screen 3 by welding or the like.

[0031] Preferably, the diameter of the outer vibration absorption hole 6 is the same as that of the inner vibration absorption hole 7, thereby ensuring that both the first vibration absorption cavity and the second vibration absorption cavity have good vibration absorption capabilities, and the number of the inner vibration absorption holes 7 is twice the number of the outer vibration absorption holes 6, thereby ensuring that the vibration absorption areas of the first vibration absorption cavity and the second vibration absorption cavity are basically the same.

[0032] Combination Figure 5 The anti-vibration screen also needs to take into account the function of the heat insulation screen. Since the anti-vibration screen needs to absorb two pulsations of different frequencies, it will generate a lot of heat. The cooling gas in the outer cooling channel flows in from between the outer anti-vibration screen 2 and the afterburner casing 1. Since the diameters of the outer vibration absorption holes 6 and the inner vibration absorption holes 7 are the same, sufficient cooling gas can enter the anti-vibration screen and cool the anti-vibration screen sufficiently. At the same time, a relatively stable cooling air film can be generated, thereby providing a more efficient heat insulation function for the afterburner.

[0033] Preferably, the anti-vibration screen bracket 5 is arranged at the front end and the rear end of the outer anti-vibration screen 2, and multiple groups of anti-vibration screen brackets 5 are arranged at intervals along the circumference of the outer anti-vibration screen 2, and each group of anti-vibration screen brackets 5 is a trapezoidal structure, and the side with a larger width of the anti-vibration screen bracket 5 is connected to the outer anti-vibration screen 2. When the afterburner is working, the outer anti-vibration screen 2 and the inner anti-vibration screen 3 are heated and thermally deformed. By setting the trapezoidal anti-vibration screen bracket 5, the thermal deformation can be effectively absorbed, and the amount of cold air used when absorbing vibration can be reduced.

[0034] Preferably, the axial length of the outer anti-vibration screen 2 is greater than the axial length of the inner anti-vibration screen 3, the anti-vibration screen support ring 4 is arranged at the front end and the rear end of the inner anti-vibration screen 3, and the anti-vibration screen support ring 4 is arranged as a wavy circular ring structure along the circumferential direction so as to be able to efficiently cooperate with the inner and outer heat insulation screens; the anti-vibration screen support ring 4 forms a stepped structure along the axial direction, which ensures stable support while allowing high-temperature fuel gas to flow in more conveniently.

[0035] As a specific implementation, it can also be set that the diameter of the outer vibration absorption hole 6 is smaller than the diameter of the inner vibration absorption hole 7. When the engine operates in a state where the duct is relatively large, the outer duct cooling air flow is relatively large, and its pressure is significantly higher than the gas pressure on the other side of the anti-vibration screen. Under the effect of the pressure difference, sufficient cooling air can pass through the vibration absorption holes to form a cooling air film on the surface of the anti-vibration screen, which plays a role in cooling and protection. When the engine operates in a state where the duct is relatively small, the outer duct cooling air flow is relatively small. At this time, the smaller aperture of the outer vibration absorption hole 6 ensures a smaller flow coefficient, and only a small amount of cooling air enters the inner flow channel through the vibration absorption hole; if necessary, the opening rate can also be controlled by adjusting the number of openings of the vibration absorption holes of the outer anti-vibration screen 2. This design can allow more cooling air to flow to the rear heat insulation screen, which can better cool and protect the downstream hot end components such as the afterburner cylinder and nozzle, thereby optimizing the overall cooling effect of the afterburner combustion chamber.

[0036] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application shall be based on the protection scope of the claims.

Claims

1. A double-wall afterburner vibration shield with multiple frequency absorption, Features: The invention comprises a coaxially arranged afterburner casing (1), an outer anti-vibration screen (2) and an inner anti-vibration screen (3); the outer anti-vibration screen (2) is arranged between the inner anti-vibration screen (3) and the combustion chamber casing, an outer cooling channel is formed between the outer anti-vibration screen (2) and the afterburner casing (1), and the inner side of the inner anti-vibration screen (3) is a high-temperature inner channel; The outer anti-vibration screen (2) is provided with outer vibration absorbing holes (6), the inner anti-vibration screen (3) is provided with inner vibration absorbing holes (7), the number of the inner vibration absorbing holes (7) is greater than the number of the outer vibration absorbing holes (6), a part of the inner vibration absorbing holes (7) is arranged radially corresponding to the outer vibration absorbing holes (6), and another part of the inner vibration absorbing holes (7) is arranged corresponding to the wall surface of the outer anti-vibration screen (2), a first vibration absorbing cavity is formed between the outer anti-vibration screen (2) and the inner anti-vibration screen (3), and a second vibration absorbing cavity is formed between the inner anti-vibration screen (3) and the afterburner casing (1); An anti-vibration screen bracket (5) is connected between the outer anti-vibration screen (2) and the afterburner casing (1), and an anti-vibration screen support ring (4) is connected between the outer anti-vibration screen (2) and the inner anti-vibration screen (3).

2. The double-walled afterburner vibration shield with multiple frequency absorption as claimed in claim 1, Features: The outer vibration absorbing holes (6) and the inner vibration absorbing holes (7) have the same diameter, and the number of the inner vibration absorbing holes (7) is twice the number of the outer vibration absorbing holes (6).

3. The double-walled afterburner vibration shield with multiple frequency absorption as claimed in claim 1, Features: The anti-vibration screen brackets (5) are arranged at the front and rear ends of the outer anti-vibration screen (2). A plurality of groups of the anti-vibration screen brackets (5) are arranged at intervals along the circumference of the outer anti-vibration screen (2). The cross-section of each group of the anti-vibration screen brackets (5) is a trapezoidal structure, and the side of the anti-vibration screen bracket (5) with a larger width is connected to the outer anti-vibration screen (2).

4. The double-walled afterburner vibration shield with multiple frequency absorption as claimed in claim 1, Features: The axial length of the outer anti-vibration screen (2) is greater than the axial length of the inner anti-vibration screen (3); the anti-vibration screen support ring (4) is arranged at the front end and the rear end of the inner anti-vibration screen (3); the anti-vibration screen support ring (4) is arranged as a wavy circular ring structure along the circumferential direction; and the anti-vibration screen support ring (4) forms a stepped structure along the axial direction.

5. The double-walled afterburner vibration shield with multiple frequency absorption as claimed in claim 1, Features: The diameter of the outer vibration absorbing hole (6) is smaller than the diameter of the inner vibration absorbing hole (7).

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