A double-wall heat shield for afterburner

Abstract

The present application belongs to the field of aviation engine technology, and particularly relates to a double-wall heat insulation screen for an afterburner combustion chamber, an afterburner casing and a double-wall heat insulation screen; an outer channel with a cooling airflow is formed between the afterburner casing and the double-wall heat insulation screen, and the double-wall heat insulation screen includes an inner air film plate and an outer impact plate; a sandwich cavity is formed between the impact plate and the air film plate; a plurality of axially distributed support rings are installed between the impact plate and the air film plate, and the plurality of support rings divide the sandwich cavity into a plurality of annular chambers; the inner side of the air film plate is an inner channel with a high-temperature airflow; the impact plate has a plurality of first air holes connecting the outer channel and the chamber at each position of the chamber, and the air film plate has a plurality of second air holes connecting the sandwich cavity and the inner channel at each position of the chamber; under the premise of achieving the same cooling effect and infrared stealth effect, the consumption of the outer cooling gas can be greatly reduced, which helps to reduce flow loss.

Description

Technical Field

[0001] The present application belongs to the field of aviation engine technology, and in particular relates to a double-wall heat shield for an afterburner. Background Art

[0002] The operating conditions and functional requirements of the new generation of aircraft place the following demands on the afterburner heat shield:

[0003] The heat shield uses as little external cooling air as possible. Using cooling air for the heat shield results in flow losses; the less cooling air used, the smaller the flow losses. Furthermore, in afterburner mode, using less cooling air for the heat shield allows more external cooling air to directly participate in combustion in the afterburner, thereby increasing engine thrust in afterburner mode.

[0004] The wall temperature distribution of the heat shield should be as uniform as possible to reduce thermal stress. The better the uniformity of the heat shield wall temperature, the smaller the thermal stress will be, which will help improve reliability and life.

[0005] In the non-afterburner state, the heat shield's wall temperature must meet infrared stealth requirements. If the aircraft and engine are not completely shielded by means of an S-bend nozzle, the heat shield will be visible from the rearward angle upwards. In the non-afterburner state, the heat shield's wall temperature must meet infrared stealth requirements, meaning the overall wall temperature must be low and uniform.

[0006] The heat shield's design must meet radar stealth requirements. If the aircraft and engine are not completely shielded by S-bend nozzles, the heat shield will be visible at an angle upwards in the rearward direction, and its design must meet the requirements of rearward radar stealth.

[0007] The heat shield needs to be strong enough. Afterburner heat shields are thin-walled cylindrical components that withstand greater external pressure than internal pressure. This can lead to buckling in situations such as abnormal afterburner flameout, abnormal nozzle control, and oscillating combustion. Therefore, sufficient strength is essential, especially for the fully separated internal and external afterburner design commonly used in new-generation military engines.

[0008] There is no design solution in the existing afterburner heat insulation screen technology that can fully meet the above requirements;

[0009] The existing afterburner heat shields can be basically divided into two types: transverse corrugated heat shields and longitudinal corrugated heat shields. The shape of the corrugations can be in various forms. Both are single-layer wall structures. Cooling holes are arranged on the wall of the heat shield, such as Figure 1 As shown in the figure, the outer cold air flows into the core flow from the cooling holes of the heat insulation screen under the action of the pressure difference between the outside and the inside, playing the role of cooling the wall of the heat insulation screen.

[0010] From the perspective of heat insulation screen air consumption, wall temperature and infrared radiation, the existing single-layer wall heat insulation screen, if using discrete large-hole cooling scheme, will have problems such as large cooling air consumption, uneven wall temperature, large thermal stress, and large infrared radiation in the non-afterburner state. If a dense small-hole (Φ1 and below) cooling scheme is adopted, these problems such as uneven wall temperature, large thermal stress, and large infrared radiation in the non-afterburner state can be solved, but the problem of large cooling air consumption will still exist.

[0011] From the perspective of radar stealth, the complex shapes of the transverse and longitudinal corrugations will produce radar signal reflections in all directions, which cannot meet the requirements of the rear radar stealth design of the engine exhaust system.

[0012] From the perspective of strength, the thin-walled cylindrical structure of the single-wall heat insulation screen has weak resistance to buckling instability. Under conditions of external and internal pressure difference and high temperature load, especially under abnormal conditions such as abnormal afterburner flameout, abnormal nozzle control, and oscillating combustion, buckling instability problems are prone to occur. Therefore, it is necessary to add fixed supports, reinforcement rings, hoops and other strengthening structures to enhance the resistance to buckling instability, which increases the complexity of the structure.

[0013] Therefore, the existing technical solutions for afterburner heat shields cannot fully meet the requirements of the new generation of military engines, and there is an urgent need to propose new design solutions. Summary of the Invention

[0014] In order to solve the above problems, the present application provides a double-wall heat shield for an afterburner, comprising:

[0015] afterburner receiver and double-walled heat shield;

[0016] An external channel with cooling airflow is formed between the afterburner casing and the double-wall heat shield, which includes an inner air film plate and an outer impact plate.

[0017] A sandwich cavity is formed between the impact plate and the air film plate; a plurality of axially distributed support rings are installed between the impact plate and the air film plate, and the plurality of support rings divide the sandwich cavity into a plurality of annular chambers;

[0018] The inner side of the air film plate is an inner channel with high-temperature airflow; the impact plate has multiple first air holes connecting the outer channel and the chamber at each chamber position, and the air film plate has multiple second air holes connecting the clamping cavity and the inner channel at each chamber position.

[0019] Preferably, the diameter of the second pore is less than 1 mm; and the diameter of the first pore is greater than that of the second pore.

[0020] Preferably, the diameter of the first pore is 1.5 to 4 times the diameter of the second pore.

[0021] Preferably, the air film plate is a uniform cylindrical surface.

[0022] Preferably, the impact plate has at least one conical section at each of the chambers, the outer diameter of which gradually increases along the direction of the external air flow, and the first air hole is provided on the conical section.

[0023] Preferably, the front end of the conical surface has a straight section formed by a depression.

[0024] Preferably, the fixed end of the support ring is fixed to the air film plate, and the other end of the support ring forms an overlapping plane overlapping the inner surface of the impact plate.

[0025] Preferably, the fixed end and the other end of the support ring are not at the same axial position, and the support ring has a plurality of bends between the two ends for improving the elastic deformation capacity of the support ring.

[0026] Preferably, the impact plate is fixed to the afterburner casing through a bracket and a self-locking nut

[0027] The advantages of this application include: while achieving the same cooling effect and infrared stealth effect, it can significantly reduce the consumption of external cooling gas, helping to reduce flow losses, and allowing more external cooling gas to directly participate in the organized combustion in the afterburner, helping to improve the thrust performance in both non-afterburner and afterburner states;

[0028] The inner layer of the double-wall heat shield adopts a flat plate structure, which helps to achieve the radar stealth design of the engine exhaust system;

[0029] Compared with single-wall heat insulation screens, double-wall heat insulation screens have better strength and better resistance to buckling instability;

[0030] The double-wall heat insulation screen has better maintainability. When the inner air film panel has problems such as high-temperature ablation and deformation, only the air film panel can be replaced, which helps to reduce maintenance costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 This is a schematic diagram of a double-wall heat shield for an afterburner in a preferred embodiment of the present application;

[0032] Figure 2 Schematic diagram of a heat shield with traditional transverse corrugation;

[0033] Figure 3 Schematic diagram of a traditional longitudinally corrugated heat shield. DETAILED DESCRIPTION

[0034] To make the technical solution and its advantages of the present application clearer, the technical solution of the present application will be described in further detail below in conjunction with the accompanying drawings. It should be understood that the specific embodiments described herein are only some embodiments of the present application and are only used to explain the present application, not to limit the present application. It should be noted that, for ease of description, only the parts related to the present application are shown in the accompanying drawings, and other related parts can refer to the general design. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other to obtain new embodiments.

[0035] In addition, unless otherwise defined, the technical or scientific terms used in the description of this application should have the ordinary meanings understood by those of ordinary skill in the art to which this application belongs. The words "upper," "lower," "left," "right," "center," "vertical," "horizontal," "inner," and "outer" used in the description of this application are only used to indicate relative directions or positional relationships, and do not imply that the device or component must have a specific orientation, be constructed, or operate in a specific orientation. When the absolute position of the described object changes, its relative positional relationship may also change accordingly. Therefore, they should not be understood as limitations on this application. The words "first," "second," "third," and similar terms used in the description of this application are used only for descriptive purposes to distinguish different components and should not be understood to indicate or imply relative importance. The words "one," "an," or "the" used in the description of this application should not be understood as absolute limitations on quantity, but should be understood as meaning the presence of at least one. The words "include" or "comprises" used in the description of this application mean that the element or object listed before the word includes the elements or objects listed after the word and their equivalents, but does not exclude other elements or objects.

[0036] In addition, it should be noted that, unless otherwise clearly stipulated and limited, the words "install", "connect", "connect" and similar terms used in the description of this application should be understood in a broad sense. For example, the connection 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, an indirect connection through an intermediate medium, or a connection between two components. Technical personnel in the field can understand their specific meanings in this application according to the specific circumstances.

[0037] In order to solve the problem of excessive external cooling air consumption in the existing afterburner single-wall heat shield, whether using discrete large-hole or dense small-hole solutions,

[0038] The single-layer heat shield with discrete large hole cooling scheme has problems of thermal stress and excessive infrared radiation caused by uneven wall temperature.

[0039] Existing afterburner single-wall heat shields, whether using transverse or longitudinal corrugations, have the problem of not being able to meet the design requirements of the engine exhaust system's rearward radar stealth.

[0040] Existing reinforced single-wall heat insulation screens all require a reinforced structure to enhance the ability to resist buckling instability, which increases the complexity of the structure.

[0041] The present application provides a double-wall heat shield for an afterburner, comprising:

[0042] Afterburner casing 1 and double-wall heat shield 2;

[0043] An outer channel with cooling airflow is formed between the afterburner casing 1 and the double-wall heat shield 2. The double-wall heat shield 2 includes an inner air film plate 21 and an outer impact plate 22.

[0044] A sandwich cavity is formed between the impact plate 22 and the air film plate 21; a plurality of axially distributed support rings 3 are installed between the impact plate 22 and the air film plate 21, and the plurality of support rings 3 divide the sandwich cavity into a plurality of annular chambers;

[0045] The inner side of the air film plate 21 is an inner channel with high-temperature airflow. The impact plate 22 has multiple first air holes 7 at each cavity location, connecting the outer channel with the cavity. The air film plate 21 has multiple second air holes 8 at each cavity location, connecting the clamping cavity with the inner channel. The support ring and the impact plate are connected by welding, and the support ring and the air film plate, as well as the impact plate and the air film plate, are connected by rivets. The bracket is also connected to the impact plate via rivets. The double-walled heat shield is fixed to the afterburner casing via the bracket using bolts and self-locking nuts. The box-shaped configuration of the double-walled heat shield, the corrugated structure of the impact plate, and the support ring structure all contribute to structural strength and enhance the heat shield's resistance to buckling instability. When operating under high-temperature conditions, such as under applied force, single-wall heat shields experience a significant decrease in strength due to the high-temperature deterioration of the high-temperature alloy, significantly weakening the shield's structural strength and buckling resistance. However, for double-wall heat shields, while the strength of the air film plate decreases significantly due to the high operating temperature, the impact plate and support ring operate on the side of the outer cold air flow, where the operating temperature is relatively low, resulting in minimal material strength loss. This maintains the overall strength and buckling resistance of the double-wall heat shield. Therefore, the double-wall heat shield of the present invention exhibits high strength and buckling resistance under various operating conditions, eliminating the need for complex reinforcement structures.

[0046] Preferably, the diameter of the second pore 8 is less than 1 mm; the diameter of the first pore 7 is larger than the diameter of the second pore 8 .

[0047] Preferably, the diameter of the first air hole 7 is 1.5 to 4 times the diameter of the second air hole 8. The impact plate of the double-wall heat insulation screen is arranged with large-diameter air inlet holes, namely the first air holes 7, according to the distance between the inner and outer layers at the corresponding positions. The air film plate of the double-wall heat insulation screen is evenly arranged with small-diameter air film holes of the order of Φ1 and below, namely the second air holes 8. The diameter and density of the air film holes can ensure that the cooling air can cover the entire air film plate evenly and without omission. The total opening area of ​​the impact plate is larger than the total opening area of ​​the air film plate, so that the impact plate shares a greater pressure drop than the air film plate. The external cold air flowing in from the large air inlet will first impact the air film plate, playing a role of impact cooling, and then flow out from the air film holes of the air film plate, forming an air film protection on the inner layer of the air film plate. It can be seen from this that compared with the single-wall heat insulation screen of the discrete large-hole cooling solution, the double-wall heat insulation screen not only consumes less cold air, but also has a more uniform wall temperature on the gas side, less thermal stress, and less infrared radiation; compared with the dense small-hole cooling solution such as the air film board of the double-wall heat insulation screen, the double-wall heat insulation screen consumes less cold air.

[0048] Preferably, the air film panel 21 is a uniform cylinder, and the air film panel of the double-wall heat insulation screen visible from the rear part adopts a flat plate shape. The reflection direction of the radar signal is relatively single, which helps to achieve the goal of blocking the radar waves inside the exhaust system cavity and dissipating them through the shape design. Therefore, the double-wall heat insulation screen of the present invention helps to achieve the rear radar stealth of the engine.

[0049] Preferably, the impact plate 22 has at least one conical section at each of the chambers, the outer diameter of which gradually increases along the direction of the external air flow, and the first air hole 7 is provided on the conical section.

[0050] Preferably, the front end of the cone has a straight section formed by a depression, which, combined with the cone, can form a corrugated structure, which on the one hand enhances the rigidity of the structure, and on the other hand can coordinate the thermal deformation difference between the inner and outer layers caused by the working temperature difference.

[0051] Preferably, a fixed end of the support ring 3 is fixed to the air film plate 21 , and the other end of the support ring 3 forms an overlapping plane overlapping the inner surface of the impact plate 22 .

[0052] Preferably, the fixed end of the support ring 3 and the other end are not at the same axial position, and the support ring 3 has multiple bends between the two ends to enhance the elastic deformation ability of the support ring 3. The bends form a stepped shape, which can also enhance the structural rigidity and maintain the structural size, and also help to coordinate the thermal deformation differences between the inner and outer layers.

[0053] The advantages of this application include: while achieving the same cooling effect and infrared stealth effect, it can significantly reduce the consumption of external cooling gas, helping to reduce flow losses, and allowing more external cooling gas to directly participate in the organized combustion in the afterburner, helping to improve the thrust performance in both non-afterburner and afterburner states;

[0054] The inner layer of the double-wall heat shield adopts a flat plate structure, which helps to achieve the radar stealth design of the engine exhaust system;

[0055] Compared with single-wall heat insulation screens, double-wall heat insulation screens have better strength and better resistance to buckling instability;

[0056] The double-wall heat insulation screen has better maintainability. When the inner air film panel has problems such as high-temperature ablation and deformation, only the air film panel can be replaced, which helps to reduce maintenance costs.

[0057] The above description is merely a specific embodiment of the present application, but the scope of protection of the present application is not limited thereto. Any changes or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in this application should be included in the scope of protection of the present application. Therefore, the scope of protection of the present application should be based on the scope of protection of the claims.

Claims

1. A double-wall heat shield for an afterburner, characterized in that: include: Afterburner casing (1) and double-walled heat shield (2); An outer channel with a cooling airflow is formed between the afterburner casing (1) and the double-wall heat shield (2), and the double-wall heat shield (2) includes an inner air film plate (21) and an outer impact plate (22); A sandwich cavity is formed between the impact plate (22) and the air film plate (21); a plurality of axially distributed support rings (3) are installed between the impact plate (22) and the air film plate (21), and the plurality of support rings (3) divide the sandwich cavity into a plurality of annular chambers; The inner side of the air film plate (21) is an inner channel with high-temperature air flow; the impact plate (22) has a plurality of first air holes (7) connecting the outer channel and the chamber at each of the chamber positions; the air film plate (21) has a plurality of second air holes (8) connecting the clamping cavity and the inner channel at each of the chamber positions; the total opening area of ​​the first air holes (7) in each chamber is greater than the total opening area of ​​the second air holes (8).

2. The double-walled heat shield for afterburner according to claim 1, characterized in that: The diameter of the second air hole (8) is less than 1 mm; the diameter of the first air hole (7) is greater than the diameter of the second air hole (8).

3. The double-walled heat shield for afterburner according to claim 2, characterized in that: The diameter of the first air hole (7) is 1.5 to 4 times the diameter of the second air hole (8).

4. The double-walled heat shield for afterburner according to claim 2, characterized in that: The air film plate (21) is a uniform cylindrical surface.

5. The double-walled heat shield for afterburner according to claim 4, characterized in that: The impact plate (22) has at least one conical section at each chamber, the outer diameter of which gradually increases along the direction of the external air flow, and the first air hole (7) is provided on the conical section.

6. The double-walled heat shield for afterburner according to claim 5, characterized in that: The front end of the cone section has a straight section formed by a depression.

7. The double-walled heat shield for afterburner according to claim 5, characterized in that: The fixed end of the support ring (3) is fixed to the air film plate (21), and the other end of the support ring (3) forms an overlapping plane overlapping the inner surface of the impact plate (22).

8. The double-walled heat shield for afterburner according to claim 7, characterized in that: The fixed end and the other end of the support ring (3) are not at the same axial position, and the support ring (3) has a plurality of bends between the two ends for improving the elastic deformation capability of the support ring (3).

9. The double-walled heat shield for afterburner according to claim 1, characterized in that: The impact plate (22) is fixed to the afterburner casing (1) through a bracket (6) and a self-locking nut (5).

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