A heat shield structure for afterburner with grille at the outlet

Abstract

The present application belongs to the field of aircraft engine technology, and particularly relates to an afterburner heat shield structure with a grille at the outlet. The afterburner heat shield structure with a grille at the outlet of the present application comprises: a heat shield, a grille, and a barrel casing; the interior of the heat shield has high-temperature internal air, and an external duct channel with external duct air is formed between the heat shield and the barrel casing, and the grille is installed at the tail end of the heat shield; the grille comprises a barrel section and an annular disk formed by radial extension of the barrel section outlet, the inlet end of the barrel section is docked with the tail end of the heat shield, the annular disk is blocked at the outlet of the external duct channel, and an annular gap is formed between the outer edge of the annular disk and the barrel casing, wherein the barrel section has a plurality of cooling holes distributed circumferentially, and the annular disk has a plurality of exhaust holes distributed circumferentially, which realizes an increase in the static pressure of the external duct airflow, ensures the smooth outflow of the airflow from the outlet cooling holes, reduces the heat load of the outlet heat shield, and improves its service life.

Description

Technical Field

[0001] The present application belongs to the field of aviation engine technology, and in particular relates to an afterburner heat shield structure with an outlet grille. Background Art

[0002] The afterburner of a turbofan engine is a device that injects fuel into the turbine outlet gas again to further increase the temperature and speed of the air flow and increase the engine thrust in a short period of time.

[0003] The heat shield is a crucial component of the afterburner of a turbofan engine. Mounted on the inside of the barrel casing via a bracket, it separates the high-temperature combustion gases from the casing. Cooling holes are provided to draw culvert air onto the shield's inner surface, forming an air film. This ensures the shield's wall temperature meets long-term operating requirements and protects the barrel casing from high-temperature combustion gases. Typically, its outlet is open, allowing culvert air to mix with the internal combustion gases before being discharged through the nozzle.

[0004] The existing open type heat insulation screen structure has the following main disadvantages:

[0005] 1. Static pressure balance between the external and internal airflows near the heat shield outlet. Since the airflow lacks driving force, the external cold air struggles to escape from the cooling holes, failing to form an effective air film on the heat shield surface, which negatively impacts the shield's service life. In some areas, the constricted passages can even cause the static pressure of the airflow to fall below the mainstream static pressure, leading to backflow of internal gas, a sharp increase in the heat shield's temperature, and potentially ablation damage.

[0006] 2. The heat shield is a large, thin-walled component mounted to the casing using a limited number of brackets. Profiling is typically performed to ensure uniform height across the outlet channel. Under hot conditions, stress release from the heat shield can easily cause deformation at the outlet, leading to uneven height across the outlet channel and uneven distribution of coolant flowing downstream. This can lead to uneven heating of the nozzle and reduce structural strength.

[0007] 3. With the demand for higher average afterburner outlet temperatures, more bypass air must enter the mainstream combustion, leaving less cooling air for the nozzle. This has led to a shrinking heat shield outlet height, sometimes even below 4mm. This extremely small channel height poses significant challenges to heat shield manufacturing and assembly, significantly increasing production costs. Summary of the Invention

[0008] In response to the current problems of low static pressure at the outlet channel of open heat shields, difficulty in ensuring circumferentially uniform outlet height, and difficulty in achieving small channel outlet height, a heat shield structure with a grille at the outlet is proposed. By adding a grille at the outlet of the heat shield, the airflow flows out from the exhaust holes of the grille, reducing the flow area of ​​the outlet. The fluid pressure of the airflow in the channel is more converted into static pressure, which increases the static pressure of the airflow. The exhaust hole area is adjusted according to the cooling air volume demand of the nozzle without lowering the height of the heat shield channel. The grille is formed by forging machine and welded to the tail end of the heat shield, which enhances the rigidity of the heat shield and facilitates the maintenance of the heat shield surface. The afterburner heat shield structure with a grille at the outlet of the present application includes:

[0009] Heat shield, grille, barrel casing;

[0010] There is high-temperature internal air inside the heat shield, and an external channel with external air is formed between the heat shield and the barrel casing. The grille is installed at the tail end of the heat shield;

[0011] The grille includes a barrel section and a ring disk formed by radially extending from the barrel section outlet. The inlet end of the barrel section is connected to the tail end of the heat insulation screen. The ring disk blocks the outlet of the outer culvert channel. An annular gap is formed between the outer edge of the ring disk and the barrel casing. The barrel section has multiple cooling holes distributed circumferentially, and the ring disk has multiple exhaust holes distributed circumferentially.

[0012] Preferably, the grid is located at the axial position where the barrel casing is connected to the nozzle casing.

[0013] Preferably, an axially extending flange is provided at the outer edge of the annular disk, and the flange facilitates the formation of a cooling air film on the inner surface of the nozzle casing in the annular gap.

[0014] Preferably, the radial width of the outer channel gradually decreases along the airflow direction.

[0015] Preferably, the heat shield has axial corrugations or circumferential corrugations.

[0016] Preferably, the heat insulation screen has a plurality of air holes for introducing external air into the internal air.

[0017] Advantages of this application include:

[0018] 1) The static pressure of the outer duct airflow is increased, which ensures the smooth outflow of the airflow from the outlet cooling hole, reduces the heat load of the outlet heat insulation screen, and improves its service life.

[0019] 2) The exhaust hole area can be adjusted according to the nozzle cooling air volume demand without reducing the heat shield channel height. This avoids the problem of the channel being too narrow when the nozzle has low cooling air volume, which makes heat shield processing and assembly difficult.

[0020] 3) The grid is machined from forgings and welded to the rear end of the heat shield, providing excellent rigidity and more uniform outlet height, thus improving the quality of nozzle cooling air.

[0021] 4) Simple structure and easy processing and manufacturing. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of the grid structure of a preferred embodiment of the present application;

[0023] Figure 2 This is a grille exhaust hole structure of a preferred embodiment of the present application;

[0024] Figure 3 It is to add the static pressure cloud diagram of the inner and outer culverts of the heat insulation screen behind the grille;

[0025] Figure 4 This is the static pressure cloud diagram inside and outside the traditional insulation screen. DETAILED DESCRIPTION

[0026] 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.

[0027] 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.

[0028] 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.

[0029] In response to the current problems of low static pressure at the outlet channel of open heat shields, difficulty in ensuring circumferentially uniform outlet height, and difficulty in achieving small channel outlet height, a heat shield structure with a grille at the outlet is proposed. By adding a grille at the outlet of the heat shield, the airflow flows out from the exhaust holes of the grille, reducing the flow area of ​​the outlet. The fluid pressure of the airflow in the channel is more converted into static pressure, which increases the static pressure of the airflow. The exhaust hole area is adjusted according to the cooling air volume demand of the nozzle without lowering the height of the heat shield channel. The grille is formed by forging machine and welded to the tail end of the heat shield, which enhances the rigidity of the heat shield and facilitates the maintenance of the heat shield surface. The afterburner heat shield structure with a grille at the outlet of the present application includes:

[0030] Heat shield 1, grille 2, cylinder casing 3;

[0031] There is high-temperature internal air inside the heat shield 1, and an external channel with external air is formed between the heat shield 1 and the barrel casing 3. The grille 2 is installed at the rear end of the heat shield 1;

[0032] The grid 2 includes a barrel section and a ring disk formed by radially extending from the barrel section outlet. The inlet end of the barrel section is connected to the tail end of the heat insulation screen 1. The ring disk blocks the outlet of the outer culvert channel. An annular gap is formed between the outer edge of the ring disk and the barrel casing 3. The barrel section has multiple cooling holes 2b distributed circumferentially, and the ring disk has multiple exhaust holes 2a distributed circumferentially.

[0033] The above-mentioned technical features explain the following cooling principle for the casing: Grille 2 is an annular forging, with the exhaust holes 2a sized according to the nozzle cooling air demand. This avoids the problem of a narrow channel under low cooling air flow conditions, which would complicate heat shield machining and assembly. Grille 2 is welded to the rear end of the heat shield 1, providing good rigidity and ensuring uniform outlet height. A gap is provided between grille 2 and the barrel casing 3, which not only accommodates expansion between the two during hot conditions but also allows some cooling air to flow out of the gap and cool the nozzle casing 4 wall.

[0034] By adding a grille 2 at the outlet of the heat shield 1, air flows out through the grille's exhaust holes 2a, reducing the flow area at the heat shield outlet. This converts more of the dynamic pressure within the channel into static pressure, increasing the static pressure. Bypass air can flow smoothly into the main cooling wall through cooling holes 2b at the outlet, reducing the heat load on the outlet heat shield and extending its service life.

[0035] Preferably, the grid 2 is located at the axial position where the barrel casing 3 and the nozzle casing 4 are connected.

[0036] Preferably, an axially extending flange is provided at the outer edge of the annular disk, and the flange facilitates the formation of a cooling air film on the inner surface of the nozzle casing 4 in the annular gap, thereby improving the cooling effect on the nozzle casing.

[0037] Preferably, the radial width of the outer channel gradually decreases along the airflow direction to maintain the pressure difference between the outer channel airflow and the inner channel air.

[0038] Preferably, the heat shield 1 has axial corrugations or circumferential corrugations to improve the thermal expansion and cooling effect of the heat shield.

[0039] Preferably, the heat insulation screen 1 has a plurality of air holes for introducing external air into the internal air.

[0040] Advantages of this application include:

[0041] 1) The static pressure of the outer duct airflow is increased, which ensures the smooth outflow of the airflow from the outlet cooling hole, reduces the heat load of the outlet heat insulation screen, and improves its service life.

[0042] 2) The exhaust hole area can be adjusted according to the nozzle cooling air volume demand without reducing the heat shield channel height. This avoids the problem of the channel being too narrow when the nozzle has low cooling air volume, which makes heat shield processing and assembly difficult.

[0043] 3) The grid is machined from forgings and welded to the rear end of the heat shield, providing excellent rigidity and more uniform outlet height, thus improving the quality of nozzle cooling air.

[0044] 4) Simple structure and easy processing and manufacturing.

[0045] 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. An afterburner heat shield structure with an outlet grille, characterized in that: include: Heat shield (1), grille (2), barrel casing (3); The heat shield (1) has high-temperature internal air inside, and an external channel with external air is formed between the heat shield (1) and the barrel casing (3), and the grille (2) is installed at the rear end of the heat shield (1); The grid (2) includes a barrel section and a ring disk formed by radially extending from the barrel section outlet, the barrel section inlet end is butted against the tail end of the heat shield (1), the ring disk blocks the outlet of the outer culvert channel, and an annular gap is formed between the outer edge of the ring disk and the barrel casing (3), wherein the barrel section has a plurality of cooling holes (2b) distributed circumferentially, and the ring disk has a plurality of exhaust holes (2a) distributed circumferentially; The grid (2) is located at an axial position where the barrel casing (3) and the nozzle casing (4) are connected; An axially extending flange is provided at the outer edge of the ring disk, and the flange facilitates the formation of a cooling air film on the inner surface of the nozzle casing (4) in the annular gap.

2. The afterburner heat shield structure with an outlet grille according to claim 1, characterized in that: The radial width of the outer channel gradually decreases along the airflow direction.

3. The afterburner heat shield structure with an outlet grille according to claim 1, characterized in that: The heat shield (1) has axial corrugations or circumferential corrugations.

4. The afterburner heat shield structure with an outlet grille according to claim 1, characterized in that: The heat insulation screen (1) has a plurality of air holes for introducing external air into the internal air.

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