Double-layer exhaust duct ejector heat insulation structure

Abstract

The application belongs to the technical field of mechanical structure and provides a double-layer exhaust casing injection heat insulation structure. The double-layer exhaust casing injection heat insulation structure comprises an exhaust cylinder, an exhaust casing, an inner mounting edge, a spacer cylinder and a support casing. The exhaust cylinder is fixed at the turbine casing at the air inlet end and is suspended at the air outlet end. The exhaust casing is in a cylindrical shape, is connected with the turbine casing and is sleeved outside the exhaust cylinder. The inner mounting edge is fixed on the exhaust casing by bolts. The spacer cylinder is connected with the outer mounting edge at the air outlet end and is connected with the inner mounting edge at the middle part. The support casing is sleeved outside the spacer cylinder and is connected with the outer mounting edge and the inner mounting edge at both ends. The air inlet end of the spacer cylinder is axially overlapped with the air outlet end of the exhaust cylinder and is sleeved outside the air outlet end of the exhaust cylinder. The radial gap between the air inlet end of the spacer cylinder and the air outlet end of the exhaust cylinder is D. The external airflow is introduced into the spacer cylinder through the injection effect, the air film is formed on the inner wall of the spacer cylinder, and the heat transfer is blocked.

Description

Technical Field

[0001] This invention belongs to the field of mechanical structure technology and provides a double-layer exhaust casing ejector heat insulation structure. Background Technology

[0002] The exhaust system of a rear-output aero-engine should have both exhaust and connection / support functions. It is a stator component and an important part of the rear-output aero-engine. Since the exhaust system needs to connect to other components, the temperature of the outer wall of the exhaust system should not exceed the maximum operating temperature of these other components due to the limitations of their materials and operating temperatures.

[0003] The structure of a conventional exhaust system is shown below. Figure 1 Where A represents the gas jet and B represents the direction of heat conduction. When the gas jet A is discharged through the exhaust device, the temperature of the exhaust device rises rapidly. Since the exhaust device is rigidly connected to other components, a large amount of heat is conducted to the connected components in the direction of B. To avoid failure due to high temperature, these components are usually designed to be resistant to high temperatures in terms of structure and materials.

[0004] Currently, there is no mechanical structure or cooling gas to insulate or cool the outer wall of the exhaust device. Summary of the Invention

[0005] The purpose of this invention is to solve the above problems by providing a double-layer exhaust casing ejector heat insulation structure, which reduces the temperature of the outer wall of the exhaust device and provides heat insulation for the connection between the exhaust device of the rear-output aero-engine and other components.

[0006] Technical solution

[0007] A double-layer exhaust casing ejector insulation structure includes: The exhaust pipe has its intake end fixed to the turbine casing and its outlet end suspended in the air. The exhaust casing is cylindrical and is connected to the turbine casing and fitted outside the exhaust pipe. The inner mounting edge is fixed to the exhaust casing with bolts; The spacer cylinder has its outlet end connected to the outer mounting edge and its middle part connected to the inner mounting edge. The support casing is fitted outside the spacer cylinder and its two ends are connected to the outer mounting edge and the inner mounting edge, respectively. The air inlet end of the spacer cylinder overlaps axially with the air outlet end of the exhaust cylinder and is fitted outside the air outlet end of the exhaust cylinder, with a radial gap of D between them. External airflow is introduced into the spacer cylinder through an ejector effect, forming an air film on the inner wall of the spacer cylinder to block heat transfer. The exhaust cylinder, spacer cylinder, and support casing all adopt an axial overlapping structure to reserve expansion space and avoid axial interference caused by thermal deformation.

[0008] The ejector jacket, consisting of an exhaust pipe and a spacer, utilizes the ejector effect for heat insulation. During engine operation, the high-speed jet passing through the exhaust system channel creates a low-pressure zone at one end of the jacket of the double-layer casing, drawing room temperature air to the jacket position and reducing the temperature of the outer wall of the exhaust casing, thereby providing heat insulation for the connection between the exhaust system and other components.

[0009] Furthermore, the radial gap between the exhaust stack and the spacer is 2~4mm. The size of the gap needs to be designed according to the actual working conditions, taking into account the size of the remaining interlayer after thermal expansion, to ensure the stability of the flowing gas film formed by the ejector effect, a high airflow velocity, and sufficient airflow to carry away the heat from the high-speed jet near the wall surface.

[0010] Furthermore, multiple circular holes with a diameter of 1mm are formed on the surface of the support casing. This improves heat exchange efficiency and reduces the heat conduction area, further minimizing heat transfer.

[0011] Furthermore, the exhaust casing has multiple ventilation holes on the walls on both sides of the exhaust pipe, providing a channel for outside cold air to enter the exhaust casing.

[0012] Furthermore, the vent holes are 15mm in diameter, with three holes on each side. The exhaust casing 2 is an important component ensuring the structural integrity of the engine and is the object isolated from the ejector heat insulation. The exhaust casing 2 has three φ15 vent holes on each side wall of the exhaust pipe 1 to provide the cold air required for ejection (i.e., Figure 2 The airflow in the middle (C and D) provides a channel to ensure that the interlayer between the exhaust stack 1 and the spacer 3 is connected to the outside atmosphere; Furthermore, a radial gap is maintained between the spacer cylinder and the exhaust casing to prevent the spacer cylinder from contacting the exhaust casing due to thermal expansion.

[0013] Furthermore, the radial clearance between the spacer cylinder and the exhaust casing is smaller than the radial clearance between the exhaust pipe and the spacer cylinder. The airflow required to form a sandwich between the exhaust pipe 1 and the spacer cylinder 3 is relatively large, so its width must be greater than the sandwich formed between the spacer cylinder 3 and the exhaust casing 2 to ensure the required airflow. Simultaneously, this overlapping structure can also avoid axial interference caused by inconsistent thermal deformation. Furthermore, two support plates are arranged on both sides of the exhaust casing, with three vent holes located between the two support plates. Since the exhaust device is directly located after the propeller, this structure can increase the pressure on the outside of the air inlet.

[0014] Furthermore, thermal insulation material, such as rock wool or glass wool, is installed on the outer surface of the exhaust pipe and the spacer. The installation of materials with low thermal conductivity further prevents heat transfer.

[0015] Furthermore, the exhaust pipe is Y-shaped overall. The inlet is circular, and the outlets on both sides are nearly elliptical.

[0016] Beneficial effects When the engine discharges high-temperature exhaust gases, the temperature of the exhaust system rises rapidly due to the gases, transferring heat to other connected components. Without considering cooling of the exhaust system, all connected components would require high-temperature resistant designs, inevitably increasing design complexity and production costs. This novel double-layer casing ejector insulation structure is simple in structure and has lower production costs. It can cool the outer wall of the exhaust system without affecting engine efficiency, thereby achieving heat insulation between the exhaust system and other connected components, significantly reducing design complexity and production costs. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. The drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the structure of the background technology of this invention; Figure 2 This is a schematic diagram of the structure of an embodiment of the present invention; Figure 3 This is a schematic diagram of the exhaust casing support plate structure. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0020] The features and illustrative embodiments of various aspects of the present invention will now be described in detail. Numerous specific details are set forth in the following detailed description to provide a thorough understanding of the invention. However, it will be apparent to those skilled in the art that the invention may be practiced without requiring some of these specific details. The following description of embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The invention is by no means limited to any specific setups and methods set forth below, but covers any improvements, substitutions, and modifications to structures, methods, and devices without departing from the spirit of the invention. Well-known structures and techniques are not shown in the drawings and the following description to avoid unnecessarily obscuring the invention.

[0021] In the description of this invention, it should be noted that the directions or positional relationships indicated by terms such as "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer" are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing and simplifying the invention, and should not be construed as limiting the invention. Furthermore, the use of ordinal numbers (e.g., "first and second," etc.) is for distinguishing objects and is not limited to this order, and should not be construed as indicating or implying relative importance.

[0022] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly, encompassing both direct connection and indirect connection via an intermediate medium. Those skilled in the art can understand the specific meaning of these terms in this invention based on the specific circumstances.

[0023] It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other, and the various embodiments can be referenced and cited in each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0025] A schematic diagram of the newly designed double-layer exhaust casing ejector insulation structure can be found below. Figure 2 In the diagram, 1-exhaust pipe, 2-exhaust casing, 3-spacer cylinder, 4-inner mounting edge, 5-support casing, 6-outer mounting edge, 7-bolt, 8-nut, 9-support plate, 10-insulation material, C / D-outdoor air, E-high-speed jet, F-propeller backflow.

[0026] The exhaust pipe 1 and the spacer 3 together form a complete exhaust channel. There is a gap of about 3mm between the exhaust pipe 1 and the spacer 3, and the spacer 3 is larger than the exhaust pipe 1, serving as a channel for injecting cold air into the exhaust channel. Multiple holes with a diameter of φ1 are made along the surface of the support casing. The holes can enhance heat dissipation capacity and reduce the heat transfer area, thereby reducing the heat transferred to the exhaust casing due to heat conduction. The size of the interlayer between exhaust stack 1 and spacer 3 needs to be designed according to the actual working conditions. The size of the remaining interlayer after thermal expansion needs to be considered to ensure that the flow film formed by the ejector effect is stable, the airflow velocity is large, and the airflow is sufficient to carry away the heat of the high-speed jet near the wall. The exhaust casing 2 is an important component ensuring the structural integrity of the engine and is the object isolated from the ejector heat insulation. The exhaust casing 2 has three φ15 vent holes on each side of the exhaust pipe 1 to allow the cool air (i.e., cool air) required for ejection. Figure 2 The airflow in the middle (C and D) provides a channel to ensure that the interlayer between the exhaust stack 1 and the spacer 3 is connected to the outside atmosphere; The maximum outer diameter of the exhaust pipe 1 must be smaller than the inner diameter of the exhaust casing 2 to ensure that the exhaust pipe 1 does not interfere when installed inside the exhaust casing 2; The lower end face of the spacer cylinder 3 must be lower than the upper end face of the exhaust cylinder 1, as shown in the enlarged figure I, to ensure the integrity of the 3mm interlayer and stabilize the ejection. A layer of about 1 mm is formed between the spacer cylinder 3 and the exhaust casing 2 to prevent the spacer cylinder 3 from contacting due to thermal expansion; The airflow required to form a sandwich between the exhaust pipe 1 and the spacer 3 is relatively large, so its width needs to be greater than the sandwich formed between the spacer 3 and the exhaust casing 2 to ensure the airflow requirement. At the same time, this overlapping structure can also avoid axial interference caused by inconsistent thermal deformation. The inner mounting edge 4, the support casing 5, and the outer mounting edge 6 together form a support structure, which on the one hand ensures the integrity of the exhaust channel, and on the other hand provides fixed support for the interlayer between the exhaust pipe 1 and the spacer 3. The screw 7 is arranged on the exhaust casing 2 and forms a complete fastening structure with the nut 9. The inner mounting edge 4, the support casing 5 and the outer mounting edge 6 are together fixed to the exhaust casing 2 to ensure the integrity of the structure. Two support plates 9 are arranged on the exhaust casing 2, forming a U-shaped structure, such as Figure 3 As shown, with the inflow of the airflow F behind the propeller, the pressure in the "U"-shaped area increases, creating a pressure difference with the exhaust casing 2, making it easier for the air behind the propeller to enter the exhaust casing 2; Thermal insulation material 10 is installed on the outer surface of the exhaust pipe and the spacer. The thermal insulation material can be high-temperature resistant rock wool or glass wool to increase thermal resistance and further reduce heat transfer.

[0027] 1-Exhaust pipe, which is Y-shaped in shape, is an exhaust pipe with exhaust from both sides. The inlet end is fixed on the turbine casing, and the outlets on both sides correspond one-to-one with the outlets of the exhaust casing. The whole is located inside the exhaust casing cavity and has a cantilever structure, and does not contact the exhaust casing. 2-Exhaust casing, which is cylindrical in shape, with the turbine casing connected to the left end of the exhaust casing. 3-Spacer cylinder, with the same shape as 1-exhaust pipe outlet, and its outline size is larger than 1-exhaust pipe outlet according to the size of the interlayer; 3-Spacer cylinder, 4-Inner mounting edge, 5-Support casing and 6-Outer mounting edge, with consistent outline shape, are welded together as one piece; The 9-support plate is a common flat plate structure, welded to the 2-exhaust casing, and located on both sides of the 2-exhaust casing intake port.

[0028] The exhaust pipe 1 is a cantilever structure after installation, and only bears a small aerodynamic force. It is a non-load-bearing component and does not have a high strength requirement. Therefore, 1mm thick GH3536 sheet metal is selected for stamping. According to strength calculation, the maximum equivalent stress is only 80MPa, which meets the usage requirements. The exhaust casing 2 is a load-bearing component that needs to withstand the propeller's pull, torque, and the weight of other components. In addition, considering the large size of the exhaust casing, in order to reduce weight, it is made of 3mm thick titanium alloy casting. According to strength calculation, the maximum equivalent stress is 330MPa, which meets the usage requirements. The spacer cylinder 3 is a non-load-bearing component, and its integrity is only required to ensure the integrity of the sandwich structure. It is made of 1mm thick sheet metal and stamped. The support casing 5 mainly serves a supporting function and needs to ensure that its deformation during operation is minimized. At the same time, in order to reduce the heat transfer area, the support casing 5 needs to be as thin as possible while ensuring rigidity. Therefore, it is made of 1.2mm thick sheet metal and stamped. Considering the weldability between 3-spacer cylinder, 4-inner mounting edge, 5-support casing and 6-outer mounting edge, the same grade of material GH3536 is selected. Support plate 9 is a non-load-bearing component, mainly serving a guiding function. Considering that it needs to be welded together with the exhaust casing 2, 1mm thick titanium alloy sheet metal is selected. For insulation material 10, which has no load-bearing requirements, considering the remaining space inside the exhaust casing, 10mm thick rock wool or glass wool is selected. It is relatively soft and can be easily attached to the surface of the part by wrapping it with iron wire.

[0029] During assembly, 1-exhaust pipe is axially assembled into 2-exhaust housing, ensuring that the outlets on both sides of 1-exhaust pipe correspond one-to-one with the outlets of 2-exhaust housing; 3-spacer cylinder, 4-inner mounting edge, 5-support housing, and 6-outer mounting edge are welded together as a whole, serving as the rear section of exhaust pipe, which is radially inserted into 2-exhaust housing and fixed to 2-exhaust housing by fasteners such as 7-studs and 8-nuts; the rear section of exhaust pipe is limited by pins installed on 2-exhaust housing to ensure the size of the interlayer between 1-exhaust pipe and 3-spacer cylinder.

[0030] When the engine is running, the high-speed jet E passes through the exhaust pipe 1, creating a low-pressure zone between the exhaust pipe 1 and the spacer 3. This draws air from points C and D to the 3mm interlayer position, and then discharges it from the exhaust pipe 1. This cycle repeats, forming a flowing heat-insulating air layer on the surface of the spacer 3. The temperature of this heat-insulating air layer is close to and maintained at the outside air temperature, achieving the purpose of heat insulation. At the same time, the air from points C and D enters the interlayer between the spacer 3 and the support casing 5, forming a slower-flowing air layer, which increases the thermal resistance at this point and effectively reduces the radiation of heat from the spacer 3 to the support casing 5. The exhaust casing 2 and the support casing 5 are directly exposed behind the propeller, forming convective heat exchange with the airflow F behind the propeller, effectively reducing the temperature of the exhaust casing 2 and the support casing 5. As the air from points C and D enters the exhaust casing 2, the wall temperature of the exhaust pipe 1 can be significantly reduced, improving reliability and service life. This new type of thermal insulation structure improves the service life and reliability of the exhaust system and related components, while reducing design difficulty and production costs.

[0031] The above detailed embodiments are a description of the present invention. It should not be considered that the specific embodiments of the present invention are limited to these descriptions. For those skilled in the art, several simple deductions and substitutions can be made without departing from the concept of the present invention, and all of these should be considered to fall within the protection scope of the present invention.

Claims

1. A double-layer exhaust casing ejector heat insulation structure, characterized in that: The structure includes: The exhaust pipe has its intake end fixed to the turbine casing and its outlet end suspended in the air. The exhaust casing is cylindrical and is connected to the turbine casing and fitted outside the exhaust pipe. The inner mounting edge is fixed to the exhaust casing with bolts; The spacer cylinder has its outlet end connected to the outer mounting edge and its middle part connected to the inner mounting edge. The support casing is fitted outside the spacer cylinder and its two ends are connected to the outer mounting edge and the inner mounting edge, respectively. The air inlet end of the spacer cylinder overlaps axially with the air outlet end of the exhaust cylinder and is sleeved on the outside of the air outlet end of the exhaust cylinder. The radial gap between the two is D. External airflow is introduced into the spacer cylinder through the ejector effect, forming an air film on the inner wall of the spacer cylinder to block heat transfer.

2. The structure according to claim 1, characterized in that: The radial gap between the exhaust pipe and the spacer is 2~4mm.

3. The structure according to claim 2, characterized in that: Multiple circular holes with a diameter of 1mm are made on the surface of the support casing.

4. The structure according to claim 3, characterized in that: The exhaust casing has multiple ventilation holes on the walls on both sides of the exhaust pipe, providing a channel for outside cold air to enter the exhaust casing.

5. The structure according to claim 4, characterized in that: The ventilation holes are 15mm in diameter, and there are 3 holes on each side.

6. The structure according to claim 5, characterized in that: A radial gap is maintained between the spacer and the exhaust casing to prevent the spacer from contacting the exhaust casing due to thermal expansion.

7. The structure according to claim 6, characterized in that: The radial clearance between the spacer cylinder and the exhaust casing is smaller than the radial clearance between the exhaust casing and the spacer cylinder.

8. The structure according to claim 7, characterized in that: Two support plates are arranged on both sides of the exhaust casing, and three vent holes are located between the two support plates.

9. The structure according to claim 8, characterized in that: Thermal insulation material, such as rock wool or glass wool, is installed on the outer surface of the exhaust pipe and the spacer.

10. The structure according to claim 9, characterized in that: The exhaust pipe is Y-shaped.

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