Exhaust nozzle for piston type aero-engine

Abstract

The utility model relates to the technical field of piston type aero-engines, in particular to an exhaust spray pipe for a piston type aero-engine, which comprises a pipe body, a throat is arranged in the middle of the pipe body, the sectional area from the throat to the air outlet end of the pipe body is gradually increased, and a first expansion part and a second expansion part are sequentially arranged from the throat to the air outlet end of the pipe body. The expansion angle of the second expansion part is larger than that of the first expansion part, and the self-adaptive expansion part is arranged in the second expansion part and can automatically adjust the expansion angle according to the working condition of an engine. The tail gas is tightly attached to the pipe wall to stably flow, energy loss is reduced, then the gas expansion effect is used for accelerating exhaust and increasing the flow speed, and in addition, the self-adaptive expansion part is arranged, so that different load requirements can be met.

Description

An exhaust nozzle for a piston aircraft engine Technical Field

[0001] This utility model relates to the field of piston aircraft engine technology, and in particular to an exhaust nozzle for piston aircraft engines. Background Technology

[0002] During the operation of a piston-type aircraft engine, the exhaust nozzle, as a key airflow guiding component, directly affects the engine's power output, fuel economy, and overall reliability. An efficient exhaust nozzle can promptly and smoothly discharge the exhaust gas after combustion, reduce exhaust back pressure, and improve the engine's working efficiency, which is crucial for ensuring the safe and stable flight of aircraft.

[0003] A search revealed a patent application with application number 202121066120.3, which discloses an exhaust nozzle for a piston-type aircraft engine. By improving the pipe structure, the working efficiency of the engine combustion gas can be increased and the exhaust gas emission speed can be accelerated. However, in actual use, a fixed expansion angle is difficult to dynamically match the changes in exhaust flow and pressure under different engine speeds and loads. For example, large-angle expansion under low-speed conditions may lead to airflow separation, while small-angle expansion under high-speed conditions limits the exhaust flow velocity. Based on this, an exhaust nozzle for a piston-type aircraft engine is proposed here. Summary of the Invention

[0004] To overcome the problems existing in related technologies, this utility model provides an exhaust nozzle for piston-type aircraft engines, which can first delay the separation of the airflow boundary layer, so that the exhaust gas flows smoothly close to the pipe wall and reduces energy loss. Then, the gas expansion effect is used to accelerate the exhaust and increase the flow rate.

[0005] To achieve the above objectives, this utility model provides an exhaust nozzle for a piston-type aircraft engine, comprising a pipe body, the middle portion of which is a throat, the cross-sectional area of ​​which gradually increases from the throat to the outlet end of the pipe body, and the throat to the outlet end of the pipe body sequentially including a first expansion portion and a second expansion portion, wherein the expansion angle of the second expansion portion is greater than that of the first expansion portion, and further comprising:

[0006] An adaptive expansion section is located within the second expansion section and can automatically adjust the expansion angle according to engine operating conditions.

[0007] Preferably, the expansion angle of the first expansion portion is 5°-10°, and the expansion angle of the second expansion portion is 10°-20°.

[0008] Preferably, the adaptive expansion portion includes a fan-shaped flexible wall surface, which is composed of multiple flexible units, and the upper end of the flexible wall surface is fixedly connected to the second expansion portion.

[0009] Preferably, a plurality of elastic elements are connected between the inner walls of the flexible wall and the second expansion portion, and a cavity is provided between the lower end of the flexible wall and the second expansion portion.

[0010] Preferably, a flow guide vane is provided inside the second expansion portion and below the flexible wall.

[0011] Preferably, the guide vane is wavy and forms an angle of 10°-20° with the airflow direction.

[0012] Preferably, the air inlet end of the pipe is fixed with a mounting plate, the mounting plate has a mounting hole, and the upper end face of the mounting plate is provided with a sealing protrusion.

[0013] The technical solution provided by this utility model can include the following beneficial effects:

[0014] 1. By setting up a first expansion section and a second expansion section with different expansion angles, the separation of the airflow boundary layer can be delayed first, so that the exhaust gas flows smoothly close to the pipe wall, reducing energy loss. Then, the gas expansion effect is used to accelerate the exhaust and increase the flow rate.

[0015] 2. In this example, by setting an adaptive expansion section, under low operating conditions, the preload of the elastic element causes the flexible wall to contract, reducing the expansion angle, increasing the exhaust back pressure, and optimizing combustion efficiency; under high operating conditions, the exhaust pressure drives the flexible wall to expand, increasing the expansion angle, reducing exhaust resistance, and adapting to different load requirements.

[0016] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and do not limit the present invention. Attached Figure Description

[0017] The above and other objects, features and advantages of the present invention will become more apparent from the accompanying drawings, in which like reference numerals generally represent like parts.

[0018] Figure 1 is a schematic diagram of the overall structure of this utility model;

[0019] Figure 2 is a schematic diagram of the overall structure of this utility model from another angle;

[0020] Figure 3 is a cross-sectional structural diagram of this utility model;

[0021] Figure 4 is a cross-sectional structural schematic diagram of the tube body of this utility model;

[0022] Figure 5 is a schematic diagram of the adaptive expansion part of this utility model.

[0023] The correspondence between the labels and component names in the attached figures is as follows:

[0024] 1. Pipe body; 2. Throat; 21. First expansion section; 22. Second expansion section; 3. Mounting plate; 4. Sealing ring; 5. Mounting hole; 6. Adaptive expansion section; 61. Flexible wall surface; 62. Elastic element; 7. Guide vane; 8. Cavity. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this utility model clearer, the technical solutions of the embodiments of this utility model will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this utility model, and not all of them. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model. The preferred embodiments of this utility model will now be described in more detail with reference to the accompanying drawings. Although the preferred embodiments of this utility model are shown in the drawings, it should be understood that this utility model can be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to make this utility model more thorough and complete, and to fully convey the scope of this utility model to those skilled in the art.

[0026] The technical solutions of the embodiments of this utility model are described in detail below with reference to the accompanying drawings.

[0027] Referring to Figure 5, this exhaust nozzle for a piston-type aircraft engine includes a pipe body 1 made of high-strength titanium alloy, possessing high-temperature resistance and fatigue resistance. The middle section of the pipe body 1 forms a throat 2. The interior of the pipe body 1 is hollow, allowing exhaust gas to flow through. A connector is provided at the air inlet end of the pipe body 1, connecting it to the engine's exhaust port. The shape of the opening at the upper end of the pipe body 1 is the same as the cross-sectional shape of the engine's exhaust port, allowing exhaust gas to smoothly exit from the exhaust port and enter the upper interior of the pipe body 1. The connector includes a mounting plate 3 fixed to the air inlet end of the pipe body 1, with mounting holes 5 on the mounting plate 3. Bolts are tightened onto the engine through mounting holes 5 on mounting plate 3, thereby fixing the exhaust nozzle. A sealing ring 4 is provided on the upper end face of mounting plate 3, which forms a seal under the preload of the bolts to ensure zero leakage in the exhaust system. The cross-sectional area from throat 2 to the outlet end of pipe body 1 gradually increases. The outlet end from throat 2 to pipe body 1 includes a first expansion section 21 and a second expansion section 22 in sequence. The expansion angle of the second expansion section 22 is greater than that of the first expansion section 21. It also includes an adaptive expansion section 6, which is disposed in the second expansion section 22 and is configured to automatically adjust the expansion angle according to the engine operating conditions.

[0028] The expansion angle of the first expansion section 21 is controlled in the range of 5°-10°. It can adopt an asymmetric gradual expansion design, with the expansion angle gradually increasing from 5° to 7°. The inner wall is formed into a micro-arc guide surface through ultra-precision machining, and the surface is coated with a nano-level molybdenum disulfide coating to reduce the surface friction coefficient to below 0.05. Combined with the slowly increasing cross-sectional area, it effectively delays the separation of the airflow boundary layer, allowing the airflow to smoothly transition close to the pipe wall.

[0029] A transition cone structure is provided between the first expansion section 21 and the second expansion section 22 to form a smooth transition surface, ensuring that no shock wave is generated when the airflow turns to the second expansion section 22. The second expansion section 22 adopts a large-angle expansion design of 10°-20°, which rapidly increases the cross-sectional area. It uses the gas expansion effect to accelerate exhaust and increase the flow rate, which is suitable for high-speed or high-load conditions. Furthermore, a spiral guide groove can be machined on the inner wall of the second expansion section 22 to guide the exhaust gas to form an orderly spiral flow in conjunction with the rapidly increased cross-sectional area.

[0030] Referring to Figures 2-3 and 5, the adaptive expansion section 6 includes a fan-shaped flexible wall 61, which is composed of multiple flexible units. The upper end of the flexible wall 61 is fixedly connected to the second expansion section 22. Multiple elastic elements 62 are connected between the inner walls of the flexible wall 61 and the second expansion section 22. A cavity 8 is provided between the lower end of the flexible wall 61 and the second expansion section 22, which provides space for the deformation of the flexible wall 61. An adjustable expansion angle flexible wall 61 is provided at the exhaust end, which can dynamically match the exhaust flow rate under different engine operating conditions. The flexible wall 61 and the elastic elements 62 can be made of high-temperature resistant elastic alloys (such as nickel-titanium alloys) or shape memory polymers, which can maintain elastic deformation capability in the temperature range of 150-500℃ to meet the exhaust gas temperature requirements of aero-engines.

[0031] When the aero-engine is operating at low speed, the exhaust velocity is low and the impact pressure of the exhaust gas on the flexible wall 61 is small. The elastic element 62 maintains the flexible wall 61 in a contracted state by its own pre-tightening force. At this time, the expansion angle is small, which helps to increase the exhaust back pressure and optimize combustion efficiency. As the engine enters high speed, the exhaust velocity increases sharply and the exhaust pressure forces the flexible wall 61 to overcome the resistance of the elastic element 62 and expand outward. The expansion angle increases accordingly, effectively reducing exhaust resistance.

[0032] Furthermore, referring to Figures 2-3 and 5, a guide vane 7 is provided inside the second expansion section 22 and below the flexible wall 61. The guide vane 7 is wavy, and its angle is 15°-20° with the airflow direction. When the exhaust gas flows into the lower end of the second expansion section 22, it contacts the curved surface of the guide vane 7. Under the guidance of the wavy structure, the exhaust gas generates an asymmetrical pressure distribution on the surface of the guide vane 7. The airflow speed increases and the pressure decreases on the side closer to the convex surface of the vane, while the airflow speed decreases and the pressure increases on the concave side. This pressure difference forms a lateral thrust, causing the exhaust gas to deviate from its original straight trajectory. As the exhaust gas continues to interact with the guide vane 7... The 15°-20° angle between the blades and the airflow further plays a role. Under the action of the tangential force generated at this angle, the exhaust gas, which originally only produced a directional shift, begins to rotate around the central axis. With the continuous action of multiple wave-shaped blade units, the exhaust gas gradually forms a stable and controllable spiral vortex. Compared with the traditional straight-flowing exhaust gas, this spiral vortex significantly increases the contact area and mixing efficiency between the exhaust gas and the surrounding medium, which helps to improve the treatment effect of the exhaust gas purification device. It can also effectively separate particulate matter and other impurities in the exhaust gas through the centrifugal force generated by the vortex, reducing the burden on subsequent treatment stages.

[0033] The present invention has been described in detail above with reference to the accompanying drawings. In the above embodiments, the descriptions of each embodiment have different focuses; for parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments. Those skilled in the art should also understand that the actions and modules involved in the specification are not necessarily essential to the present invention. Furthermore, it is understood that the steps in the method of the present invention embodiments can be adjusted, combined, and deleted according to actual needs, and the structure in the device of the present invention embodiments can be combined, divided, and deleted according to actual needs.

[0034] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments. The terminology used herein is chosen to best explain the principles, practical application, or improvement of the technology in the market, or to enable others skilled in the art to understand the embodiments disclosed herein.

Claims

1. An exhaust nozzle for a piston-type aircraft engine, comprising a pipe body (1), wherein the middle portion of the pipe body (1) is a throat (2), and the cross-sectional area of ​​the throat (2) gradually increases from the outlet end of the pipe body (1), characterized in that, The air outlet from the throat (2) to the pipe body (1) includes a first expansion section (21) and a second expansion section (22) in sequence. The expansion angle of the second expansion section (22) is greater than that of the first expansion section (21). It also includes an adaptive expansion section (6), which is set in the second expansion section (22) and can automatically adjust the expansion angle according to the engine operating conditions.

2. The exhaust nozzle for a piston-type aircraft engine according to claim 1, characterized in that: The expansion angle of the first expansion part (21) is 5°-10°, and the expansion angle of the second expansion part (22) is 10°-20°.

3. The exhaust nozzle for a piston-type aircraft engine according to claim 1, characterized in that: The adaptive expansion section (6) includes a fan-shaped flexible wall (61), which is composed of multiple flexible units, and the upper end of the flexible wall (61) is fixedly connected to the second expansion section (22).

4. The exhaust nozzle for a piston-type aircraft engine according to claim 3, characterized in that: Multiple elastic elements (62) are connected between the inner walls of the flexible wall (61) and the second expansion (22), and a cavity (8) is provided between the lower end of the flexible wall (61) and the second expansion (22).

5. The exhaust nozzle for a piston-type aircraft engine according to claim 1, characterized in that: A flow guide vane (7) is provided inside the second expansion portion (22) and below the flexible wall (61).

6. The exhaust nozzle for a piston-type aircraft engine according to claim 5, characterized in that: The guide vane (7) is wavy, and the guide vane (7) forms an angle of 15°-20° with the airflow direction.

7. The exhaust nozzle for a piston-type aircraft engine according to claim 1, characterized in that: The air inlet end of the pipe (1) is fixed with a mounting plate (3), the mounting plate (3) has a mounting hole (5), and the upper end face of the mounting plate (3) is provided with a sealing ring (4).

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