A retractable tail nozzle

Abstract

This invention provides a retractable tail nozzle connected to the engine tail section, comprising: a connecting assembly including a connecting element and a first cylindrical thin-walled tube, the air inlet end of the first cylindrical thin-walled tube being detachably connected to the engine tail section via the connecting element; a straight section including a second cylindrical thin-walled tube, the air inlet end of the second cylindrical thin-walled tube being sleeved on the outer wall of the air outlet end of the first cylindrical thin-walled tube; and a round-to-square section connected to the air outlet end of the second cylindrical thin-walled tube. This invention solves the problem of difficult engine installation in modern stealth aircraft by reducing engine installation workload through the retractable tail nozzle and utilizing the different coefficients of linear expansion of different materials to achieve sealing of the tail nozzle during operation.

Description

Technical Field

[0001] This specification relates to the field of aircraft tail nozzle technology, specifically to a retractable tail nozzle. Background Technology

[0002] Modern stealth aircraft, for stealth design considerations, typically have embedded S-shaped air intakes and round-to-square exhaust nozzles located before and after the engine, respectively. Both the air intakes and exhaust nozzles are embedded within the fuselage, requiring high installation precision and precise sealing at their connection to the engine. Engine installation necessitates reserving installation space before and after the engine. To ensure this space, the air intakes or exhaust nozzles often need to be removed first, which can affect the installation precision of the entire power system and significantly increase the workload of engine assembly and disassembly. Another design approach is to use a segmented exhaust nozzle design, removing the connecting section during engine installation and reinstalling it afterward. This approach reduces some of the disassembly and assembly work, but it requires extremely high installation precision and is prone to problems such as insufficient gaps for installation or insufficient sealing, making it difficult to apply in practical engineering. Summary of the Invention

[0003] In view of this, the embodiments of this specification provide a retractable tail nozzle, which can achieve the purpose of easy disassembly and assembly and the tail nozzle can be sealed automatically.

[0004] The embodiments in this specification provide the following technical solutions:

[0005] A retractable tail nozzle, connected to the rear of the engine, includes:

[0006] A connecting assembly, comprising a connecting element and a first cylindrical thin-walled tube, wherein the air intake end of the first cylindrical thin-walled tube is detachably connected to the engine tail via the connecting element;

[0007] The straight section includes a second cylindrical thin-walled tube, the air inlet end of which is sleeved on the outer wall of the air outlet end of the first cylindrical thin-walled tube.

[0008] The round-to-square section is connected to the outlet end of the second cylindrical thin-walled tube.

[0009] Furthermore, the first cylindrical thin-walled tube and the second cylindrical thin-walled tube are made of materials with different coefficients of linear expansion.

[0010] Furthermore, the radius of the first cylindrical thin-walled tube is R1, the coefficient of linear expansion of the material of the first cylindrical thin-walled tube is θ1, the radius of the second cylindrical thin-walled tube is R2, the coefficient of linear expansion of the material of the second cylindrical thin-walled tube is θ2, the engine combustion temperature is T_gas, the indoor temperature is T_room temperature, and the radial gap between the first and second cylindrical thin-walled tubes is δ, where δ≤(R1θ1-R2θ2)(T_gas)燃气 -T 室温 ).

[0011] Furthermore, when the temperature is indoors, the first cylindrical thin-walled tube can move axially along the second cylindrical thin-walled tube.

[0012] Furthermore, when the gas temperature is reached, the first cylindrical thin-walled tube and the second cylindrical thin-walled tube are radially sealed.

[0013] Furthermore, the connection method of the connecting element is one or a combination of several of the following: threaded connection, bolted connection, clamp connection, and flange connection.

[0014] Furthermore, the straight section also includes a guide section, which is a horn structure located on the intake side of the second cylindrical thin-walled tube.

[0015] Furthermore, the radius of the guide section is larger than the radius of the second cylindrical thin-walled tube.

[0016] Compared with the prior art, the beneficial effects that at least one technical solution adopted in the embodiments of this specification can achieve include at least:

[0017] To solve the problem of difficult engine installation in modern stealth aircraft, a retractable tail nozzle is used to reduce the amount of engine installation work, and the different coefficients of linear expansion of different materials are used to achieve a seal of the tail nozzle during operation. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of the overall structure of the retractable tail nozzle according to an embodiment of the present invention;

[0020] Figure 2 This is a partial schematic diagram of the connecting assembly of the retractable tail nozzle in an embodiment of the present invention when it is slid to the engine direction;

[0021] Figure 3 This is a partial schematic diagram of the connecting assembly of the retractable tail nozzle in an embodiment of the present invention when it slides to the straight section direction.

[0022] Explanation of reference numerals in the attached drawings: 1. First cylindrical thin-walled tube; 2. Second cylindrical thin-walled tube; 3. Round-to-square section; 4. Engine; 5. Guide section; 6. Connecting element. Detailed Implementation

[0023] The embodiments of this application will now be described in detail with reference to the accompanying drawings.

[0024] The following specific examples illustrate the implementation of this application. Those skilled in the art can easily understand other advantages and effects of this application from the content disclosed in this specification. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of them. This application can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of this application. It should be noted that, in the absence of conflict, the following embodiments and features in the embodiments can be combined with each other. Based on the embodiments in this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0025] It should be noted that various aspects of embodiments within the scope of the appended claims are described below. It will be apparent that the aspects described herein can be embodied in a wide variety of forms, and any particular structure and / or function described herein is merely illustrative. Based on this application, those skilled in the art will understand that one aspect described herein can be implemented independently of any other aspect, and two or more of these aspects can be combined in various ways. For example, any number and aspects set forth herein can be used to implement the device and / or practice the method. Additionally, this device and / or method can be implemented using structures and / or functionalities other than one or more of the aspects set forth herein.

[0026] It should also be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of this application. The drawings only show the components related to this application and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0027] Furthermore, specific details are provided in the following description to facilitate a thorough understanding of the examples. However, those skilled in the art will understand that the described aspects can be practiced without these specific details.

[0028] The technical solutions provided by the various embodiments of this application are described below with reference to the accompanying drawings.

[0029] refer to Figure 1The retractable tailpipe has an intake end that is detachably mounted at the rear of the engine 4, and an exhaust end that releases gas into the atmosphere. The retractable tailpipe includes: a connecting assembly consisting of a connecting element 6 and a first cylindrical thin-walled tube 1, the first cylindrical thin-walled tube 1 being connected to the engine 4 via the connecting element 6; a straight section including a second cylindrical thin-walled tube 2, the intake end of the second cylindrical thin-walled tube 2 being fitted onto the outer wall of the exhaust end of the first cylindrical thin-walled tube 1; and a round-to-square section 3, integrally connected to the straight section. The intake end of the straight section is provided with a flared guide section 5 for guiding the first cylindrical thin-walled tube 1 when it is inserted into the second cylindrical thin-walled tube 2. Because the diameter difference between the first cylindrical thin-walled tube 1 and the second cylindrical thin-walled tube 2 is small, a guide section 5 with a slightly larger diameter is needed to assist in inserting the first cylindrical thin-walled tube 1 into the second cylindrical thin-walled tube 2.

[0030] In this embodiment of the invention, under room temperature conditions (i.e., non-starting state), the radius of the first cylindrical thin-walled tube 1 is smaller than the radius of the second cylindrical thin-walled tube 2. The first cylindrical thin-walled tube 1 can move axially along the second cylindrical thin-walled tube 2. The radial gap between the first cylindrical thin-walled tube 1 and the second cylindrical thin-walled tube 2 is δ, which should satisfy the following formula: δ≤(R1θ1-R2θ2)(T 燃气 -T 室温 ), where R1 is the radius of the first cylindrical thin-walled tube 1 of the connecting assembly, θ1 is the linear expansion coefficient of the material of the first cylindrical thin-walled tube 1, R2 is the radius of the second cylindrical thin-walled tube 2 of the straight section, θ2 is the linear expansion coefficient of the material of the first cylindrical thin-walled tube 1, and T 燃气 T represents the engine combustion temperature. 室温 Room temperature.

[0031] After engine 4 starts, high-temperature combustion gases are ejected through the exhaust nozzle, causing the nozzle temperature to rise to near the combustion gas temperature (i.e., engine operating temperature). Both the first cylindrical thin-walled tube 1 and the second cylindrical thin-walled tube 2 expand due to heat. To meet the sealing requirements of the exhaust nozzle during engine operation, the first cylindrical thin-walled tube 1 is made of a material with a high coefficient of linear expansion, while the second cylindrical thin-walled tube 2 is made of a material with a low coefficient of linear expansion. After the two cylindrical thin-walled tubes expand due to heat, the first cylindrical thin-walled tube 1 expands more, while the second cylindrical thin-walled tube 2 expands less. Ultimately, the gap is completely eliminated, and a certain amount of interference is generated, achieving a seal between the first cylindrical thin-walled tube 1 and the second cylindrical thin-walled tube 2.

[0032] In addition, after engine 4 starts, the temperature of the entire engine rises due to the combustion of aviation kerosene in the combustion chamber, causing engine 4 to expand due to heat. This causes the first cylindrical thin-walled tube 1 connected to engine 4 to extend backward along the engine axis. The first cylindrical thin-walled tube 1 and the second cylindrical thin-walled tube 2 are sleeved structures and can slide along the axis, effectively releasing the thermal stress generated by the expansion of engine 4.

[0033] It should be noted that the axial dimensions of the first cylindrical thin-walled tube 1 and the second cylindrical thin-walled tube 2 should meet the following conditions:

[0034] 1. For example Figure 2 As shown, when the first cylindrical thin-walled tube 1 slides towards the engine 4 until it can no longer move, the first cylindrical thin-walled tube 1 and the second cylindrical thin-walled tube 2 still have a certain sleeve length.

[0035] 2. For example Figure 3 As shown, when the first cylindrical thin-walled tube 1 slides towards the second cylindrical thin-walled tube 2 until it can no longer move, sufficient installation space can be left for the engine 4.

[0036] In this embodiment of the invention, a connecting element 6 is provided at the front end of the connecting section assembly, which can be connected to the engine 4. The connection method can be threaded connection, bolt connection, clamp connection, flange connection, etc. When installing the engine 4, the connection of the connecting element 6 needs to be disconnected, and the first cylindrical thin-walled tube 1 of the engine connecting assembly is slid towards the straight section to leave sufficient installation space for the engine 4. After the engine 4 is installed, the first cylindrical thin-walled tube 1 is slid towards the engine 4 and then connected to the engine 4.

[0037] The following specific examples illustrate the application of retractable nozzles.

[0038] Assuming the exhaust gas temperature of an aircraft engine is 500℃ and the room temperature is 20℃, the radius of the first cylindrical thin-walled tube 1 and the second cylindrical thin-walled tube 2 of the tail nozzle is approximately 320mm. Based on the radial clearance requirements between the first and second cylindrical thin-walled tubes 1 and 2, stainless steel 1Cr18Ni9Ti is selected for the first cylindrical thin-walled tube 1, and high-temperature alloy GH3039 is selected for the second cylindrical thin-walled tube 2. The linear expansion coefficient of 1Cr18Ni9Ti between 20℃ and 500℃ is 17.9, and the linear expansion coefficient of GH3039 between 20℃ and 500℃ is 13.8. The radial clearance δ≤(R1θ1-R2θ2)(T 燃气 -T 室温 =0.63mm, therefore the radius of the connecting section at room temperature can be set as R1 = (320±0.1)mm, and the radius of the straight section as R2 = (320.5±0.1)mm.

[0039] At room temperature, the radial clearance δ is (0.5±0.2) mm, which allows the first cylindrical thin-walled tube 1 and the straight section of the second cylindrical thin-walled tube 2 to slide axially. When the gas temperature is 500℃, the radial clearance is (-0.13±0.2) mm, which allows for effective sealing between the first cylindrical thin-walled tube 1 and the straight section of the second cylindrical thin-walled tube 2 of the connecting assembly.

[0040] This embodiment simplifies the engine installation process while ensuring the sealing of the tail nozzle, and can release the thermal stress generated by engine expansion, which can be applied to the tail nozzle design of modern stealth aircraft.

[0041] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. In particular, the method embodiments described later are relatively simple in description because they correspond to the system; relevant parts can be referred to the descriptions in the system embodiments.

[0042] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A retractable tail nozzle, connected to the rear of an engine (4), characterized in that, include: The connecting assembly includes a connecting element (6) and a first cylindrical thin-walled tube (1), the air intake end of the first cylindrical thin-walled tube (1) being detachably connected to the rear end of the engine (4) via the connecting element (6); The straight section includes a second cylindrical thin-walled tube (2), the air inlet end of which is sleeved on the outer wall of the air outlet end of the first cylindrical thin-walled tube (1); The circular-to-square section (3) is connected to the outlet end of the second cylindrical thin-walled tube (2); The first cylindrical thin-walled tube (1) and the second cylindrical thin-walled tube (2) are made of materials with different coefficients of linear expansion; The radius of the first cylindrical thin-walled tube (1) is The linear expansion coefficient of the material of the first cylindrical thin-walled tube (1) is The radius of the second cylindrical thin-walled tube (2) is The coefficient of linear expansion of the material of the second cylindrical thin-walled tube (2) is The combustion gas temperature of engine (4) is The indoor temperature is The radial gap between the first cylindrical thin-walled tube (1) and the second cylindrical thin-walled tube (2) is ,in, ; When the indoor temperature is reached, the first cylindrical thin-walled tube (1) can move axially along the second cylindrical thin-walled tube (2); When the gas temperature is reached, the first cylindrical thin-walled tube (1) and the second cylindrical thin-walled tube (2) are radially sealed.

2. The retractable tail nozzle according to claim 1, characterized in that, The connection method of the connecting element (6) is one or a combination of threaded connection, bolted connection, clamp connection, and flange connection.

3. The retractable tail nozzle according to claim 1, characterized in that, The straight section also includes a guide section (5), which is a horn structure set on the air intake side of the second cylindrical thin-walled tube (2).

4. The retractable tail nozzle according to claim 3, characterized in that, The radius of the guide section (5) is greater than the radius of the second cylindrical thin-walled tube (2).

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