Turbojet engine and aircraft

Abstract

The present application provides a turbojet engine and aircraft, relating to the field of aero-engine technology, comprising a casing having a combustion chamber, a compressor and a turbine respectively arranged at the air inlet and air outlet of the casing, and a tail nozzle connected to the turbine, wherein the compressor and the turbine are connected in a transmission manner, and a micro-perforated plate metal foam composite structure is provided along the circumferential direction on the inner wall of the air inlet of the casing to reduce the noise generated when air enters the casing. A plurality of axially extending airflow channels are provided along the circumferential direction on the inner wall of the tail nozzle, each airflow channel including a plurality of interconnected airflow grooves, and the plurality of airflow grooves constituting the same airflow channel are connected end to end along the axial direction of the tail nozzle so that each airflow channel forms a Tesla valve structure. The flow diversion direction of the Tesla valve structure is consistent with the direction of airflow ejected from the casing into the atmosphere, effectively suppressing the generation of noise at the sound source, achieving a broadband noise reduction effect, and reducing the complexity and weight of the system, thereby controlling thrust loss to an extremely low level.

Description

Technical Field

[0001] The present application relates to the field of aviation engine technology, and in particular to a turbojet engine and an aircraft. Background Art

[0002] With growing global environmental awareness and the advancement of sustainable development goals, noise pollution in the aerospace sector has come under increasing scrutiny. Reducing jet noise has become a critical issue that the aviation industry must address. In the field of aircraft engines, the noise problem of traditional turbojet engines is particularly prominent. The main sources of noise include the following: The unevenness of the airflow within the engine inlet duct leads to turbulent airflow, and the interaction of this airflow with the inlet wall becomes one of the main sources of noise; when the engine is operating at high speed, the airflow velocity in the inlet duct increases sharply, and the noise also increases significantly; the high-temperature, high-pressure gas ejected from the engine tail nozzle interacts with the surrounding air, generating aerodynamic noise with a wide spectrum and high intensity, causing serious interference to the surrounding environment.

[0003] To address this issue, existing engine noise control technologies fall into two categories: passive control and active control. Passive control technology achieves noise suppression by using noise-reducing materials (such as metamaterial liners) in the air inlet, optimizing structural design (such as semicircular grooves and porous layers), and optimizing structural geometry (such as serrated and lobed nozzles). Active control technology reduces noise by modulating the shear layer with external energy. This approach not only ensures good aerodynamic performance but also achieves good noise reduction. However, this technology relies on complex additional devices, such as high-pressure air sources and power systems, which increase the weight and energy consumption of the system, thereby limiting its feasibility in practical applications.

[0004] In recent years, the Tesla valve structure has garnered attention in the noise suppression field due to its simplicity, durability, and reliability, requiring no external actuator. It utilizes its internal geometry to block reverse airflow, or to reduce noise through multiple reflections and absorption of sound waves off the valve wall. However, traditional Tesla valves only reduce noise at the reverse outlet and are unable to effectively control noise at the forward exit of the airflow, limiting their direct application in engine noise reduction. Summary of the Invention

[0005] The purpose of this application is to provide a turbojet engine and aircraft to address the deficiencies in the above-mentioned technology.

[0006] To achieve the above objectives, the technical solutions adopted in this application are as follows:

[0007] The present application provides a turbojet engine, comprising a casing having a combustion chamber, a compressor and a turbine respectively arranged at an air inlet and an air outlet of the casing, and a tail nozzle connected to the turbine. The compressor and the turbine are drivingly connected, and a micro-perforated plate metal foam composite structure is circumferentially arranged on the inner wall of the air inlet of the casing to reduce noise generated when air enters the casing.

[0008] A plurality of axially extending airflow channels are provided on the inner wall of the tail nozzle at intervals along the circumferential direction, and each airflow channel includes a plurality of interconnected airflow grooves. The plurality of airflow grooves constituting the same airflow channel are connected end to end in sequence along the axial direction of the tail nozzle so that each airflow channel forms a Tesla valve structure. The flow diversion direction of the Tesla valve structure is consistent with the direction of the airflow ejected from the casing into the atmosphere.

[0009] Furthermore, the micro-perforated plate metal foam composite structure includes a micro-perforated plate, a metal foam layer and a partition that are stacked in sequence, and the partition is arranged to fit the inner wall of the air inlet of the casing.

[0010] Furthermore, the pore size of the micro-perforated plate is 0.1 mm to 1 mm, the perforation rate of the micro-perforated plate is 1% to 3%, and the porosity of the metal foam layer is 60% to 90%.

[0011] Furthermore, a straightening cone is coaxially arranged at the air inlet of the casing. The straightening cone has a cylindrical structure and is used to pre-straighten the air entering the casing.

[0012] Furthermore, the airflow groove includes a first straight side wall, a curved side wall, and a second straight side wall that are sequentially connected to form a teardrop-shaped structure. The first straight side wall includes a first straight inner side wall and a first straight outer side wall that are parallel and spaced apart. The curved side wall includes a curved inner side wall and a curved outer side wall that are parallel and spaced apart. The second straight side wall includes a second straight inner side wall and a second straight outer side wall that are parallel and spaced apart. The first straight inner wall, the curved inner wall, and the second straight inner wall are sequentially connected to form an inner side wall of the teardrop-shaped structure. The first straight outer wall, the curved outer wall, and the second straight outer wall are sequentially connected to form an outer wall of the teardrop-shaped structure.

[0013] The inner wall profile of each air flow slot is expressed as:

[0014]

[0015] in, X S and Y S are the inner side walls of the first straight line x Axis coordinate values ​​and y Axis coordinate values, X R and Y RThe inner side walls are x Axis coordinate values ​​and y Axis coordinate values, X I and Y I are the inner side walls of the second straight line x Axis coordinate values ​​and y Axis coordinate values, x c and y c are the centers of the arc side walls x Axis coordinate values ​​and y Axis coordinate values, r 1 is the radius of the inner wall of the arc, x 1 is the intersection of the first straight line inner wall and the second straight line inner wall x Coordinate values, y 1 is the intersection of the first straight line inner wall and the second straight line inner wall y Coordinate values, t is a linear spacing vector with values ​​ranging from 0 to 1, θ is the angle between the first straight side wall and the second straight side wall;

[0016] The outer wall profile of each air flow slot is expressed as:

[0017]

[0018] in, X S ’ and Y S ’ are the outer side walls of the first straight line x Axis coordinate values ​​and y Axis coordinate values, X R ’ and Y R ’ The outer side walls are curved x Axis coordinate values ​​and y Axis coordinate values, X I ’ and Y I ’ are the outer side walls of the second straight line x Axis coordinate values ​​and y Axis coordinate values, r 2 is the radius of the outer wall of the arc, x 2 is the intersection of the first straight outer wall and the second straight outer wall x Coordinate values,y 2 is the intersection of the first straight outer wall and the second straight outer wall y Coordinate value.

[0019] Furthermore, the depth of the airflow groove ,in, a is the depth coefficient, a The value range is 0.001 to 0.1, D j It is the diameter of the tail nozzle at the end away from the casing.

[0020] Furthermore, the surface roughness R of the air flow channel a Less than or equal to 0.8μm.

[0021] Furthermore, the tail nozzle is made of nickel-based alloy or ceramic-based composite material.

[0022] Furthermore, the tail nozzle and the air flow channel are integrally formed through 3D printing.

[0023] Furthermore, a central cone is coaxially arranged in the tail nozzle, and the central cone is connected to the inner wall of the tail nozzle via a spoiler, and the orthographic projection of the spoiler on the inner wall of the tail nozzle does not coincide with the airflow channel.

[0024] Furthermore, the central cone includes a cylindrical structure and a hemispherical structure connected in sequence along the axial direction of the tail nozzle, and the cylindrical structure is located on the side of the tail nozzle close to the casing.

[0025] Furthermore, the tail nozzle has a conical structure, and the enlarged end of the conical structure is connected to the turbine.

[0026] The present application also provides an aircraft comprising any of the above-mentioned turbojet engines.

[0027] The beneficial effects of this application include:

[0028] The present application provides a turbojet engine and aircraft. The turbojet engine includes a casing having a combustion chamber, a compressor and a turbine respectively disposed at the casing's air inlet and air outlet, and a tail nozzle connected to the turbine, wherein the compressor and the turbine are in transmission connection. A micro-perforated plate metal foam composite structure is circumferentially arranged on the inner wall of the casing's air inlet to reduce the noise generated when air enters the casing. A plurality of airflow channels are circumferentially spaced apart on the inner wall of the tail nozzle, each airflow channel including a plurality of interconnected airflow grooves. The plurality of airflow grooves constituting the same airflow channel are sequentially connected end to end along the axial direction of the tail nozzle so that each airflow channel forms a Tesla valve structure. The flow direction of the Tesla valve structure is consistent with the direction of airflow ejected from the casing into the atmosphere. Thus, the micro-perforated plates in the micro-perforated plate metal foam composite structure can reduce the low-frequency aerodynamic noise generated when air enters the casing, and the metal foam can suppress medium and high-frequency noise, thereby achieving broadband noise suppression. The Tesla valve structure can guide the wall boundary layer airflow to produce a unidirectional flow trend. The boundary layer airflow is ejected into the atmosphere through the Tesla valve structure, while the airflow at other positions is ejected into the atmosphere through other cavities in the tail nozzle. The two jets are in full contact with the surrounding atmosphere at the nozzle outlet and intertwine with each other, forming a multi-point, multi-scale shear and turbulence interaction zone, which significantly improves the uniform mixing efficiency of the airflow and the ambient air. Through this structured flow path distribution and shear layer densification process, large-scale coherent vortices are decomposed into several small-scale vortex clusters in advance, effectively suppressing the generation of noise from the sound source, weakening the vortex-induced noise source originally concentrated in the low-frequency band, and transferring its sound power to the high-frequency band. High-frequency noise is more easily attenuated due to air absorption, thereby achieving a broadband noise reduction effect within the entire auditory spectrum. The passive flow field control technology provided by the present application does not require an additional drive device, reduces the complexity and weight of the system, and also avoids the energy consumption problem of the high-pressure gas source and power supply system. In addition, this passive noise reduction technology can achieve efficient noise reduction while controlling thrust loss at an extremely low level, solving the problems existing in existing technologies such as large thrust loss, complex system, and difficulty in balancing noise reduction effect and aerodynamic performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0030] Figure 1 This is one of the structural schematic diagrams of a turbojet engine provided in this application;

[0031] Figure 2 This is the second structural diagram of a turbojet engine provided by this application;

[0032] Figure 3 This is a schematic structural diagram of a micro-perforated plate metal foam composite structure of a turbojet engine provided in this application;

[0033] Figure 4 A schematic structural diagram of a casing air inlet of a turbojet engine provided in this application;

[0034] Figure 5 A schematic diagram of the three-dimensional structure of a tail nozzle of a turbojet engine provided in this application;

[0035] Figure 6 A side view of a tail nozzle of a turbojet engine provided in this application;

[0036] Figure 7 for Figure 6 AA section view in;

[0037] Figure 8 A front view of a tail nozzle of a turbojet engine provided in this application;

[0038] Figure 9 A rear view of a tail nozzle of a turbojet engine provided in this application;

[0039] Figure 10 A schematic diagram of the flow of air in the Tesla valve structure provided in this application;

[0040] Figure 11 A schematic structural diagram of an airflow slot of a tail nozzle of a turbojet engine provided in this application;

[0041] Figure 12 A schematic structural diagram of an airflow channel of a tail nozzle of a turbojet engine provided in this application;

[0042] Figure 13 Flow field velocity distribution cloud diagrams when using a turbojet engine without an airflow channel and the turbojet engine provided by the present application;

[0043] FIG14( a ) is a far-field noise distribution cloud diagram of a turbojet engine without an airflow channel and a turbojet engine provided by the present application;

[0044] FIG14( b ) is a diagram showing the change in the total sound pressure level of far-field noise when the turbojet engine provided by the present application is used.

[0045] Icons: 1-casing; 11-fairing cone; 12-fairing; 13-micro-perforated plate metal foam composite structure; 131-micro-perforated plate; 132-metal foam layer; 133-partition; 14-compressor; 15-turbine; 2-tail nozzle; 21-mounting edge; 22-center cone; 23-airflow channel; 24-spoiler; L1-first straight line inner wall; L2-second straight line inner wall; M1-arc-shaped inner wall; L3-first straight line outer wall; L4-second straight line outer wall; M2-arc-shaped outer wall. DETAILED DESCRIPTION

[0046] To make the objectives, technical solutions, and advantages of this application more clear, the technical solutions of this application will be clearly and completely described below in conjunction with the accompanying drawings. Obviously, the described embodiments are only some of the embodiments of this application, not all of them. Generally, the components of this application described and shown in the drawings herein can be arranged and designed in various different configurations.

[0047] Therefore, the following detailed description of the embodiments of the present application provided in the accompanying drawings is not intended to limit the scope of the present application as claimed, but merely represents selected embodiments of the present application. It should be noted that, unless there is a conflict, the various features of the embodiments of the present application may be combined with each other, and the combined embodiments are still within the scope of protection of the present application.

[0048] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0049] In the description of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of this application is typically placed when in use. These terms are intended only to facilitate the description of this application and simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, the terms "first," "second," "third," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0050] Furthermore, terms such as "horizontal" and "vertical" do not necessarily mean that a component must be absolutely horizontal or overhanging, but rather that it can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but rather that it can be slightly tilted.

[0051] It should also be noted that, in the description of this application, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0052] The technical solution of the present application is described in detail below with reference to specific embodiments.

[0053] The present application provides a turbojet engine, such as Figures 1 to 9 As shown, it mainly consists of a casing 1 with a combustion chamber, a compressor 14 and a turbine 15 respectively arranged at the air inlet and outlet of the casing 1, and a tail nozzle 2 connected to the turbine 15. The compressor 14 and the turbine 15 are connected by a mechanical transmission. The main function of the compressor 14 is to pressurize the air and send the pressurized air into the combustion chamber to mix and burn with the fuel. The high-temperature and high-pressure gas generated after combustion drives the turbine 15 to rotate, driving the compressor 14 to continue working and ensure the normal operation of the engine. The remaining high-temperature and high-pressure gas is discharged through the tail nozzle 2, and after acceleration, it forms thrust, thereby propelling the aircraft forward.

[0054] However, during the operation of a turbojet engine, the air flow in the air inlet area generates noise. First, when air enters the casing 1 from the air inlet of the casing 1 at high speed, it collides and impacts with the inner wall of the casing 1, the blades of the compressor 14, and other internal components, generating high-intensity aerodynamic noise. In addition, the compressor 14 also causes noise when pressurizing the air. Especially at high speeds, the noise of the compressor 14 usually covers a wide frequency band and is more significant. In order to effectively suppress these noises, especially in the air inlet area, a micro-perforated plate metal foam composite structure 13 is provided along the circumferential direction on the inner wall of the air inlet of the casing 1.

[0055] like Figure 3As shown, the micro-perforated plate metal foam composite structure 13 includes a micro-perforated plate 131, a metal foam layer 132, and a partition 133, which are stacked in sequence. Partition 133 serves as a supporting substrate, adhered to the inner wall of the casing 1, and provides a stable support for the subsequent sound absorption layer. The metal foam layer 132 is arranged in close proximity to the partition 133, and its three-dimensional mesh pores form an independent central cavity space with the partition 133; the micro-perforated plate 131 is attached to the outside of the metal foam layer 132, and utilizes the acoustic damping effect of the micropores to effectively convert sound energy into heat energy and dissipate it through the thermoviscous boundary layer in the micropores. Without the need for additional porous damping materials, by combining appropriate micropores, the micro-perforated plate 131 can match the impedance of air in the required frequency band, thereby achieving a lower-frequency sound absorption effect.

[0056] When noise passes through the micropores of the microperforated plate 131, the acoustic impedance and acoustic quality parameters (such as perforation diameter, perforation thickness, and perforation ratio) of the plate 131 are adjusted to approximate the atmospheric acoustic impedance (approximately 400 kg / (m²·s)). This reduces sound wave reflection and enhances sound wave transmission and absorption. When the acoustic impedance of the microperforated plate 131 matches that of air, sound wave energy is directly converted into heat through friction and viscous losses, achieving low-frequency noise absorption and attenuation. Unabsorbed sound waves enter the metal foam layer 132, where they repeatedly collide and scatter with its irregular three-dimensional pore surface. This process of multiple return propagation continuously attenuates the sound pressure level, enhancing the sound absorption effect and effectively suppressing mid- and high-frequency noise. Furthermore, the porous structure of the metal foam dissipates sound waves layer by layer, achieving even better sound absorption. Furthermore, the baffles 133 further trap remaining sound waves in the interstices of the multi-layer cavity, maximizing sound energy attenuation through repeated reflection and frictional losses.

[0057] This micro-perforated plate and metal foam composite structure 13 design achieves wide-band noise suppression. The micro-perforated plate 131 primarily targets low-frequency noise, while the metal foam primarily suppresses mid- and high-frequency noise, thereby reducing noise intensity across a wide range of the noise spectrum.

[0058] To further enhance the noise reduction effect, a plurality of axially extending airflow channels 23 are circumferentially spaced apart on the inner wall of the tail nozzle 2. Each airflow channel 23 includes a plurality of interconnected airflow slots. The multiple airflow slots forming the same airflow channel 23 are connected end-to-end along the axial direction of the tail nozzle 2, so that each airflow channel 23 forms a Tesla valve structure. The flow diversion direction of the Tesla valve structure is consistent with the direction of the airflow ejected from the casing 1 into the atmosphere. This structure, through geometric layout, achieves nearly unobstructed forward airflow and creates a localized flow resistance difference during reverse flow, thereby finely controlling the jet flow. The connection between the airflow slots not only maintains channel connectivity, but also accelerates the mixing of the airflow with the ambient air by alternating the throttling and expansion zones.

[0059] like Figure 10 As shown, the Tesla valve structure relies on its unidirectional flow-guiding characteristics: its forward inlet is connected to the air inlet of the tail nozzle 2, and its forward outlet is connected to the air outlet of the tail nozzle 2. As a result, the Tesla valve structure can guide the wall boundary layer airflow to produce a unidirectional flow trend. When the jet is discharged from the casing 1 into the atmosphere at high speed (forward), the boundary layer airflow is ejected into the atmosphere through the Tesla valve structure, while the airflow at other locations is ejected into the atmosphere through other cavities in the tail nozzle 2. The two jets fully contact the surrounding atmosphere at the nozzle outlet and intersect with each other, forming a multi-point, multi-scale shear and turbulence interaction zone, which significantly improves the uniform mixing efficiency of the airflow and the ambient air. Through this structured flow distribution and shear layer densification process, large-scale coherent vortices are pre-decomposed into several small-scale vortex clusters, effectively suppressing noise generation at the source. This weakens the vortex-induced noise source originally concentrated in the low-frequency band (<1kHz) and shifts the far-field noise power to the high-frequency band (>1kHz), reducing the lateral low-frequency sound pressure level and achieving a significant reduction in the overall sound pressure level. High-frequency noise is more easily attenuated due to air absorption, thus achieving a broadband noise reduction effect across the entire auditory spectrum. Secondly, this passive flow field control technology does not require additional drive devices, reducing the complexity and weight of the system while also avoiding the energy consumption issues of the high-pressure air source and power supply system. In addition, this passive noise reduction technology can control thrust loss to less than 1% while achieving efficient noise reduction.

[0060] Furthermore, the micro-perforated plate 131 is fabricated through laser precision machining, with apertures precisely controlled between 0.1 mm and 1 mm, with a tolerance of only ±5 μm, and a perforation rate maintained between 1% and 3% with an error of no more than ±0.2%. This high-precision micro-pore array produces significant acoustic damping and viscous dissipation in the low-frequency range. Furthermore, its aperture parameters are tightly coupled with the cavity of the downstream metal foam layer 132, ensuring that acoustic waves receive initial energy attenuation before entering the foam layer.

[0061] Metal foam layer 132 is fabricated using a vacuum-inflated infiltration casting method: CaCl₂ particles with a diameter of 0.5 mm to 5 mm are used as a soluble filler. Molten aluminum is injected into the foam under a vacuum of -0.095 MPa and a flow pressure of 1 MPa. After solidification, the CaCl₂ is removed, resulting in a three-dimensional acoustic energy dissipation network with a porosity between 60% and 90%. This layer not only scatters and reflects sound waves multiple times through its internal irregular pores, further attenuating mid- and high-frequency noise, but also utilizes the metal's inherent high thermal conductivity to increase the conversion of acoustic energy into thermal energy, passively transferring heat to the intake airflow, and optimizing the thermodynamic conditions at the inlet of casing 1.

[0062] Furthermore, the total thickness of the micro-perforated metal foam composite structure 13 can be designed to be an integer multiple of a quarter wavelength of the main peak in the target noise reduction frequency band, thereby forming a suitable standing wave resonant sound absorption cavity. This integer multiple of a quarter wavelength design not only achieves the strongest sound absorption effect at the main peak frequency, but also maintains good broadband attenuation performance in adjacent frequency bands.

[0063] Furthermore, if Figure 1 and Figure 2 As shown, a cylindrical straightening cone 11 is coaxially arranged at the air inlet of the casing 1, which is used to pre-process the air flow field entering the casing 1. The axis of the straightening cone 11 coincides with the center of the air inlet of the casing 1, and its surface is smooth and fluent to minimize its own interference with the incoming flow. The straightening cone 11 is connected to the side wall of one end of the fairing 12 through a plurality of connecting rods distributed at equal intervals in the annular direction, and the other end of the fairing 12 is sleeved on the outer wall of the air inlet of the casing 1. The number and arrangement angles of the connecting rods are optimized through aerodynamic simulation to ensure that the straightening cone 11 maintains a stable position under the impact of high-speed airflow, and at the same time, no local vortex or dead zone is formed at the connection part. The air flowing through the air inlet is first guided by the straightening cone 11, dispersed from both sides of the cylindrical cone, and then evenly enters the subsequent compressor 14 after bypassing the straightening cone 11. This pre-straightening technology smoothes the inlet airflow at its source, allowing air to enter the compressor 14 passage at a more uniform velocity and angle. This reduces impact and shear noise caused by airflow separation and turbulence, significantly lowering aerodynamic noise during the engine's intake phase. Furthermore, this uniform intake flow reduces uneven pressure distribution at the compressor 14 blade inlet, improving compressor efficiency and reducing overall flow resistance, thereby enhancing engine propulsion performance and fuel economy.

[0064] Furthermore, if Figure 11 As shown, the airflow groove includes a first straight side wall, a curved side wall, and a second straight side wall that are sequentially connected to form a teardrop-shaped structure. The first straight side wall includes a first straight inner side wall L1 and a first straight outer side wall L3 that are parallel and spaced apart. The curved side wall includes a curved inner side wall M1 and a curved outer side wall M2 that are parallel and spaced apart. The second straight side wall includes a second straight inner side wall L2 and a second straight outer side wall L4 that are parallel and spaced apart. The first straight inner wall L1, the curved inner wall M1, and the second straight inner wall L2 are sequentially connected to form the inner side wall of the teardrop-shaped structure. The first straight outer wall L3, the curved outer wall M2, and the second straight outer wall L4 are sequentially connected to form the outer wall of the teardrop-shaped structure.

[0065] The inner wall profile of each air flow slot is expressed as:

[0066]

[0067] in, X S andY S are the first straight inner side wall L1 x Axis coordinate values ​​and y Axis coordinate values, X R and Y R They are respectively the arc inner wall M1 x Axis coordinate values ​​and y Axis coordinate values, X I and Y I are the second straight inner side wall L2 x Axis coordinate values ​​and y Axis coordinate values, x c and y c are the centers of the arc side walls x Axis coordinate values ​​and y Axis coordinate values, r 1 is the radius of the arc inner wall M1, x 1 is the intersection of the first straight inner side wall L1 and the second straight inner side wall L2 x Coordinate values, y 1 is the intersection of the first straight inner side wall L1 and the second straight inner side wall L2 y Coordinate values, t is a linear spacing vector with values ​​ranging from 0 to 1, θ is the angle between the first straight side wall and the second straight side wall. The length of the first straight inner wall L1 is 1.5 mm, and the length of the second straight inner wall L2 is 1.8 mm. According to the geometric relationship, the arc length of the arc-shaped inner wall M1, the length of the first straight outer wall L3, the length of the second straight outer wall L4 and the arc length of the arc-shaped outer wall M2 can be calculated.

[0068] The outer wall profile of each air flow slot is expressed as:

[0069]

[0070] in, X S ’ and Y S ’ are the first straight outer side wall L3 x Axis coordinate values ​​and y Axis coordinate values, X R ’ and Y R’ They are respectively the arc-shaped outer side wall M2 x Axis coordinate values ​​and y Axis coordinate values, X I ’ and Y I ’ are the second straight outer side wall L4 x Axis coordinate values ​​and y Axis coordinate values, r 2 is the radius of the arc-shaped outer wall M2, x 2 is the intersection of the first straight outer wall L3 and the second straight outer wall L4 x Coordinate values, y 2 is the intersection of the first straight outer wall L3 and the second straight outer wall L4 y Coordinate values, In this implementation, .

[0071] like Figure 13 As shown in Figure 14(a) and (b), the Tesla valve structure of this embodiment can increase the growth rate of the jet shear layer thickness by 15% to 20% and shorten the core zone length by 4% to 6%, thereby effectively suppressing the development of large-scale coherent structures. As shown in Figures 14(a) and 14(b), this structural design can also reduce the lateral (100° to 150°) low-frequency noise sound pressure level by more than 3dB, and the total sound pressure level by up to 6.1dB, effectively reducing noise exposure in sensitive areas on the ground.

[0072] Overall, this technical solution effectively meets the noise limit requirements for the new generation of turbojet engines and has significant practical significance. Through the rational design of the airflow channel 23 and the Tesla valve structure, the mixing of the jet and ambient airflow is optimized, significantly suppressing engine noise emissions while further balancing the engine's propulsion efficiency and aerodynamic performance. This solution addresses the existing issues of large thrust losses, complex systems, and the difficulty in balancing noise reduction and aerodynamic performance, fully demonstrating the unique advantages of passive flow field control and efficient noise reduction.

[0073] Furthermore, if Figure 12 As shown, the depth of the air flow groove ,in, a is the depth coefficient, a The value range is 0.001 to 0.1, D j is the diameter of the tail nozzle 2 away from the end of the casing 1. The range of the groove depth h is 0.5 mm to 1 mm. In this embodiment, D j =119mm, h =1mm. By increasing the depth of the airflow grooveh According to the outlet diameter of tail nozzle 2 D j The ratio of the depth coefficient can ensure that each airflow slot is neither too shallow (ineffective in disturbing the boundary layer and difficult to form sufficient reverse resistance) nor too deep (avoiding excessive flow resistance due to excessive slot depth, which affects the forward thrust output). a When the value is smaller, the groove depth h Shallow, mainly produces micro-scale disturbances, helps to suppress high-frequency noise, while maintaining low resistance to the forward jet; when the depth coefficient a When the larger value is taken, the groove depth h Increasing it can form stronger turbulence and separation zone in reverse flow and enhance the suppression of low-frequency noise.

[0074] Therefore, by reasonably selecting the depth coefficient a , and according to the outlet diameter of tail nozzle 2 D j Accurate calculation of groove depth h , achieving both suppression of noise across different frequency bands and an optimized balance of jet flow performance. This groove depth design, matched to the pipe geometry, is key to achieving passive flow field control and broadband noise reduction while maximizing thrust.

[0075] Furthermore, if Figure 12 As shown, the width of the air flow slot , slot width w The value range of is 0.50 mm to 3 mm. In this embodiment, the slot width w =1mm. The circumferential spacing between two adjacent airflow channels 23 λ The value range of is 5mm to 20mm. In this embodiment, the spacing is arranged λ =15mm. Designing a reasonable slot width and spacing according to requirements can further achieve the balanced suppression of noise in different frequency bands and the optimal balance of jet flow performance.

[0076] Furthermore, when two adjacent airflow grooves are connected end to end, it is necessary to cut the first straight outer wall L3, the second straight outer wall L4 and the arc-shaped outer wall M2 so that the two adjacent airflow grooves are connected end to end, that is, one end of the two adjacent airflow grooves close to the arc-shaped side wall of the airflow groove is connected to the other end of the airflow groove away from the arc-shaped side wall M2, thereby realizing one-way airflow. It should be noted that the angle between the line connecting one end of the cut arc-shaped outer wall M2 and the center of the circle and the line connecting the other end of the arc-shaped outer wall and the center of the circle is α The value range of is 120° to 160°. Figure 12 As shown, in this embodiment, the angle α=150°. The appropriate cutting position can ensure that the airflow is almost unobstructed when flowing in the forward direction along the airflow channel, and form a local flow resistance difference when flowing in the reverse direction.

[0077] Furthermore, the number of air flow grooves constituting the same air flow channel 23 is 16 to 42.

[0078] Furthermore, the surface roughness R of the air flow channel 23 is a Less than or equal to 0.8μm. Fine surface processing can minimize the unplanned turbulence and attachment flow separation caused by tiny bumps on the wall, thereby ensuring the stability and predictability of the flow in the airflow channel 23. In the Tesla valve structure, the airflow channel 23 must maintain extremely low resistance during forward flow and enhance local resistance during reverse flow - both of which rely on precise control of the boundary layer. Excessively rough surfaces may lead to reduced thrust efficiency and increased noise generation. Therefore, controlling the surface roughness Ra of the airflow channel 23 to within 0.8μm can maintain stable attachment of the boundary layer, ensure low-resistance and high-efficiency output of the forward flow, and achieve broadband and high-efficiency passive noise reduction.

[0079] Furthermore, the tail nozzle 2 must operate for long periods in high-temperature, high-pressure, and high-vibration environments. Therefore, material selection must balance high-temperature strength, oxidation resistance, creep resistance, and machining precision. Specifically, the tail nozzle 2 can be constructed of a high-temperature alloy, preferably a nickel-based high-temperature alloy (such as Inconel 718 or Inconel X-750). These alloys maintain excellent yield strength and creep resistance at temperatures above 700–900°C, resisting high-temperature oxidation and thermomechanical fatigue caused by the combustion gases. Furthermore, the alloy's coefficient of thermal expansion is similar to that of other hot-end engine components, helping to reduce thermal stress. For higher-temperature sections or areas requiring further weight reduction, ceramic-based composites (such as C / SiC and SiC / SiC) can be used. These materials can withstand temperatures exceeding 1200°C and have a density approximately half that of metal. This effectively reduces overall mass and thermal inertia, facilitating transient response and thermal management. Through precision casting, hot isostatic pressing or advanced machining processes, the tail nozzle 2 is guaranteed to maintain structural safety under harsh working conditions, while ensuring the functional performance of the airflow groove and Tesla valve structure, thereby achieving long-term stable noise reduction and propulsion performance.

[0080] Furthermore, the present application employs an additive manufacturing process to integrally form the tail nozzle 2 and the airflow channel 23 via 3D printing. This integrated molding process not only simplifies the assembly process of components and avoids the sealing and strength risks associated with traditional multi-piece welding or mechanical connections, but also allows for the full utilization of topology optimization and lattice structures during the design phase to precisely control the geometry and wall thickness distribution of the airflow channel 23.

[0081] Specifically, the one-piece molding structure makes the overall component more reliable and durable, eliminates the stress concentration and fatigue crack sources caused by traditional processing or welding, and significantly improves the thermal shock and vibration resistance of the tail nozzle 2. In addition, the digital production process of additive manufacturing, combined with online monitoring and post-processing detection, can quickly iterate process parameters to achieve batch and traceable high-quality production. In terms of maintenance, since the overall structure has no assembly gaps, there are no problems such as loose bolts or gasket leakage, and there is almost no need for tedious inspections and adjustments in the later stage, which greatly reduces maintenance costs and downtime. Through 3D printing integrated molding, the tail nozzle 2 has been significantly improved in manufacturing efficiency, structural strength, reliability and ease of maintenance, fully demonstrating the engineering application potential of this technology in the design and production of modern aircraft engines.

[0082] Furthermore, if Figure 5 As shown, a central cone 22 is coaxially arranged within the tail nozzle 2, i.e., the central cone 22 is located at the center of the tail nozzle 2. Ten airflow channels 23 are circumferentially and evenly spaced along the inner wall of the tail nozzle 2, with the angle between each two adjacent channels being 36°, ensuring uniform distribution of the jet flow in the circumferential direction. To further control the jet flow, the central cone 22 is connected to the inner wall via six spoilers 24, which are evenly spaced at 60° intervals. One end of each spoiler 24 is fixed to the central cone 22, and the other end is fixed to the inner wall of the nozzle body. The spoilers 24 are arranged in the gaps between adjacent airflow channels 23, and their orthographic projections on the inner wall do not overlap with any airflow channel 23, thereby avoiding direct obstruction of the main jet channel and preventing interference with the flow field. To balance strength and weight, these spoilers 24 adopt a hollow airfoil structure with a thickness of 2 mm. This design can withstand mechanical loads in high-temperature and high-pressure environments while also reducing flow resistance through the airfoil cross-section.

[0083] Furthermore, if Figure 7 As shown, the central cone 22 comprises a cylindrical structure and a hemispherical structure connected in sequence along the axial direction of the tail nozzle 2. The cylindrical structure is located on the side of the tail nozzle 2 close to the casing 1. The central cone 22 adopts a smooth curved surface design that gradually converges along the direction of airflow discharge. The cylindrical section provides a stable pre-guiding area for the incoming airflow, ensuring the axial symmetry of the flow field; the hemispherical structure reduces vortices at the outlet of the tail nozzle 2, thereby reducing aerodynamic losses.

[0084] Furthermore, if Figure 5As shown, the tail nozzle 2 has a conical structure. The expanded end of the cone serves as the nozzle's air inlet, sealingly connected to the turbine 15 at the air outlet of the casing 1. The narrowed end serves as the nozzle's air outlet, directing the airflow outward. An annular mounting edge 21 is provided around the nozzle's air inlet. Twelve groups of six high-temperature performance bolt holes are spaced along this edge, allowing for threaded connection to the turbine 15. This ensures a reliable mechanical connection and airtightness between the nozzle 2 and the casing 1.

[0085] In this embodiment, the working process of the air flow channel 23 is as follows: when the high-temperature combustion gas (temperature 600-800°C, flow velocity 300-500m / s) enters the tail nozzle 2 from the air inlet of the tail nozzle 2, it is first guided by the central cone 22 to form an axisymmetric flow field, then flows through the air flow channel 23 on the inner wall, and is ejected from the air outlet of the tail nozzle 2.

[0086] The present application also provides an aircraft, such as an airplane, which includes any of the above-mentioned turbojet engines. Since the aircraft uses the above-mentioned turbojet engine, it also has the same beneficial effects as the turbojet engine, which will not be described in detail here.

[0087] The foregoing description is merely a preferred embodiment of the present application and is not intended to limit the present application. Persons skilled in the art will readily appreciate that various modifications and variations are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A turbojet engine, characterized in that: The invention comprises a casing having a combustion chamber, a compressor and a turbine respectively arranged at the air inlet and the air outlet of the casing, and a tail nozzle connected to the turbine. The compressor is in driving connection with the turbine. A micro-perforated plate metal foam composite structure is arranged along the circumferential direction on the inner wall of the air inlet of the casing to reduce the noise generated when air enters the casing. A plurality of air flow channels extending axially are provided on the inner wall of the tail nozzle at intervals along the circumferential direction, each of the air flow channels includes a plurality of interconnected air flow grooves, and the plurality of air flow grooves constituting the same air flow channel are connected end to end in sequence along the axial direction of the tail nozzle so that each air flow channel forms a Tesla valve structure, and the flow diversion direction of the Tesla valve structure is consistent with the direction of the air flow ejected from the casing into the atmosphere.

2. The turbojet engine according to claim 1, characterized in that: The micro-perforated plate metal foam composite structure includes a micro-perforated plate, a metal foam layer and a partition plate which are stacked in sequence, and the partition plate is arranged in contact with the inner wall of the air inlet of the casing.

3. The turbojet engine according to claim 2, characterized in that: The pore size of the micro-perforated plate is 0.1 mm to 1 mm, the perforation rate of the micro-perforated plate is 1% to 3%, and the porosity of the metal foam layer is 60% to 90%.

4. The turbojet engine according to any one of claims 1 to 3, characterized in that: A straightening cone is coaxially arranged at the air inlet of the casing. The straightening cone is a cylindrical structure and is used to pre-straighten the air entering the casing.

5. The turbojet engine according to any one of claims 1 to 3, characterized in that: The airflow groove includes a first straight side wall, a curved side wall, and a second straight side wall that are sequentially connected to form a teardrop-shaped structure, the first straight side wall includes a first straight inner side wall and a first straight outer side wall that are parallel and spaced apart, the curved side wall includes a curved inner side wall and a curved outer side wall that are parallel and spaced apart, the second straight side wall includes a second straight inner side wall and a second straight outer side wall that are parallel and spaced apart, the first straight inner wall, the curved inner wall, and the second straight inner wall are sequentially connected to form the inner side wall of the teardrop-shaped structure, and the first straight outer wall, the curved outer wall, and the second straight outer wall are sequentially connected to form the outer wall of the teardrop-shaped structure; The inner side wall profile expression of each air flow groove is: in, X S and Y S are the inner sidewalls of the first straight line x Axis coordinate values ​​and y Axis coordinate values, X R and Y R are respectively the arc-shaped inner sidewall x Axis coordinate values ​​and y Axis coordinate values, X I and Y I are the inner sidewalls of the second straight line x Axis coordinate values ​​and y Axis coordinate values, x c and y c are the center of the arc side wall x Axis coordinate values ​​and y Axis coordinate values, r 1 is the radius of the arc-shaped inner wall, x 1 is the intersection of the first straight inner side wall and the second straight inner side wall x Coordinate values, y 1 is the intersection of the first straight inner side wall and the second straight inner side wall y Coordinate values, t is a linear spacing vector with values ​​ranging from 0 to 1, θ is the angle between the first straight side wall and the second straight side wall; The outer wall profile of each air flow groove is expressed as: in, X S ’ and Y S ’ are respectively the outer side walls of the first straight line x Axis coordinate values ​​and y Axis coordinate values, X R ’ and Y R ’ are respectively the arc-shaped outer side walls x Axis coordinate values ​​and y Axis coordinate values, X I ’ and Y I ’ are respectively the outer side walls of the second straight line x Axis coordinate values ​​and y Axis coordinate values, r 2 is the radius of the arc-shaped outer side wall, x 2 is the intersection of the first straight outer wall and the second straight outer wall x Coordinate values, y 2 is the intersection of the first straight outer wall and the second straight outer wall y Coordinate value.

6. The turbojet engine according to any one of claims 1 to 3, characterized in that: The depth of the air flow groove ,in, a is the depth coefficient, a The value range is 0.001 to 0.1, D j is the diameter of the tail nozzle at the end away from the casing; The surface roughness R of the air flow channel a Less than or equal to 0.8μm.

7. The turbojet engine according to any one of claims 1 to 3, characterized in that: The tail nozzle is made of nickel-based alloy or ceramic-based composite material.

8. The turbojet engine according to any one of claims 1 to 3, characterized in that: The tail nozzle and the air flow channel are integrally formed by 3D printing.

9. The turbojet engine according to any one of claims 1 to 3, characterized in that: A central cone is coaxially arranged in the tail nozzle. The central cone is connected to the inner wall of the tail nozzle via a spoiler. The orthographic projection of the spoiler on the inner wall of the tail nozzle does not overlap with the airflow channel.

10. An aircraft, characterized in that: A turbojet engine comprising the turbojet engine according to any one of claims 1 to 9.

Images