Low infrared signature self-adapting variable cycle engine exhaust system with plug cone

Abstract

The application belongs to the field of engine exhaust system, and particularly relates to a low-infrared-characteristic self-adaptive variable cycle engine exhaust system with plug cone, which further comprises tail support plates, outer plug cone, support, inner plug cone A, inner plug cone B, actuating cylinder A, actuating cylinder B, adjusting sleeve, ring sleeve, first expansion adjusting sheet, second expansion adjusting sheet, baffle B and converging cylinder, wherein a third channel with closed end is connected with a spindle-shaped outer plug cone with opening at tail through a plurality of tail support plates which are uniformly distributed in circumference, and the outer plug cone is provided with the inner plug cone A through the support, and the inner plug cone A forms a third channel throat and a third channel airflow outlet in annular shape. The application adjusts the area of the third channel outlet through the inner plug cone B, so as to ensure that the static pressure at the third channel outlet is basically the same as that at the main flow channel outlet in the cruising state, and further ensure that the loss in the airflow mixing process is small and fuel is saved. In other states, when the main flow throat needs to be shortened, the airflow flow is controlled by adjusting the size of the main flow throat through the adjusting sleeve.

Description

Technical Field

[0001] This invention belongs to the field of engine exhaust systems, and particularly relates to a low-infrared-feature adaptive variable-cycle engine exhaust system with a plug cone. Background Technology

[0002] In 2021, foreign research institutions announced that the first and only adaptive variable cycle engine to enter the test phase had completed testing, achieving two different modes: high thrust and high efficiency. Analysis of the publicly released animations shows that, in addition to the two publicly disclosed modes, it also has a maximum thrust-to-weight ratio mode and a conventional turbofan mode. After being equipped with this engine, fighter jets can increase loiter time by 25%, improve fuel efficiency by 25%, increase range by 35%, and increase thrust by 10%. The test results are consistent with the predictions, indicating that the new generation of foreign fighter jets equipped with the XA100 engine have adaptive variable cycle propulsion capabilities.

[0003] Plug exhaust systems possess unique aerodynamic properties and are used in aviation and aerospace fields. Research on their aerodynamic properties began in the 1950s. The Lewis Aircraft Propulsion Laboratory in the United States conducted research on the internal thrust performance and external drag characteristics of non-adjustable axisymmetric plug nozzles. The results showed that, on the one hand, when deviating from the design point, the thrust coefficient of the plug nozzle changes very little and always maintains a high value. That is, the plug nozzle has high internal thrust characteristics when operating in a large pressure ratio range. On the other hand, in the range of Mach number of the outflow, the drag coefficient of the plug nozzle is lower than that of traditional axisymmetric convergent nozzles and axisymmetric divergent nozzles.

[0004] Plug nozzles also have considerable advantages in infrared suppression. On the one hand, the low-temperature plug cone shields the high-temperature components inside the engine's rear cavity, which helps reduce infrared radiation characteristics. On the other hand, the pressure on the plug nozzle wall is lower than the pressure of the internal high-temperature components, so the required bleed air pressure for cooling is lower when cooling measures are taken, and cooling bleed air is easier to achieve.

[0005] Domestic and international literature discloses the flow channel configuration of adaptive variable cycle engines with plug-type exhaust systems, but does not specifically disclose the adjustment method of the flow channel. For example, in patent EP1533510B1, the airflow in the third duct is discharged from the annular cavity between the outer and inner plug cones, and the flow rate can be adjusted by moving the inner plug cone. The mainstream airflow is discharged from the nozzle, and the mainstream airflow and the third duct airflow are mixed downstream of the nozzle but not mixed in the nozzle. This configuration is equivalent to the mainstream airflow and the third duct airflow being discharged independently. At the same time, the mainstream throat and mainstream outlet are both adjusted by moving the sleeve. This adjustment structure of the mainstream throat and mainstream outlet is much simpler than that of the regulating plate type adjustment.

[0006] The exhaust system in patent EP1533510B1 has poor infrared suppression performance, as specifically demonstrated below: The airflow in the third duct only begins to mix with the mainstream flow downstream of the nozzle, resulting in a poor cooling effect on the tail jet.

[0007] The main airflow outlet is adjusted by a sleeve. Under different conditions, the length of the exposed plug cone varies greatly, resulting in a stronger infrared signal when the plug cone is more exposed. The infrared suppression effect is unstable and the overall effect is poor.

[0008] This invention designs a low-infrared-feature adaptive variable-cycle engine exhaust system with a plug cone to solve the above problems. Summary of the Invention

[0009] To address the aforementioned deficiencies in the prior art, this invention discloses a low-infrared-feature adaptive variable-cycle engine exhaust system with a plug cone, which is implemented using the following technical solution.

[0010] A low-infrared adaptive variable cycle engine exhaust system with a plug cone includes a tail support plate, an outer plug cone, a support, an inner plug cone A, an inner plug cone B, an actuator A, an actuator B, an adjusting sleeve, an annular sleeve, a first expansion adjusting plate, a second expansion adjusting plate, a baffle B, and a convergent cylinder. The third duct, closed at its end, is connected to a spindle-shaped outer plug cone located in the middle of the exhaust nozzle and open at its tail end via several circumferentially evenly distributed tail support plates. An inner plug cone A, forming an annular third duct throat and an annular third duct airflow outlet, is mounted inside the outer plug cone via a support. An inner plug cone B, axially sealed and sliding within the inner plug cone A, adjusts the airflow outlet area of ​​the third duct under the drive of the actuator A. An adjusting sleeve, axially sliding within the end of the third casing, adjusts the main flow throat under the drive of four circumferentially evenly distributed actuators B. A convergent cylinder, forming a main flow convergent section with the outer plug cone, is installed at the end of the third duct.

[0011] The adjusting sleeve has several circumferentially evenly distributed first expansion adjusting plates at its end, which adjust the outlet area of ​​the main airflow. Each first expansion adjusting plate has a second expansion adjusting plate slidingly fitted on its outer side along its length. The end of the axially sealing sliding ring at the end of the outer casing has several baffles B that correspond one-to-one with the second expansion adjusting plates. The end of each baffle B is hinged to the end of the corresponding second expansion adjusting plate. The adjusting sleeve and the first expansion adjusting plates have a structure that drives the first and second expansion adjusting plates to swing synchronously in a contracting or expanding manner.

[0012] As a further improvement of this technology, a connecting rod A is hinged to the fixed rod on the outer side of the first expansion adjustment plate, and a connecting rod B is hinged to the end of the connecting rod A. The connecting rod B is hinged to the actuating ring B nested and sliding on the adjustment sleeve. The actuating ring B is driven by four actuating cylinders C that are circumferentially and evenly installed on the adjustment sleeve.

[0013] As a further improvement to this technology, an actuating ring A, which is connected to an adjusting sleeve, is nested and slidably mounted on the outer side of the end of the third housing. The actuating ring A is driven by four actuating cylinders B that are evenly distributed circumferentially on the outer side of the third housing.

[0014] As a further improvement to this technology, the inner side of the outermost second expansion adjustment piece of all the second expansion adjustment pieces has a locking piece that cooperates with the adjacent second expansion adjustment pieces on both sides.

[0015] As a further improvement to this technology, the inner side of the outermost baffle B in all the baffles B has a locking tab that cooperates with the adjacent baffles B on both sides.

[0016] As a further improvement to this technology, the tail opening of the outer plug cone is circumferentially uniformly distributed with large lobes that increase the mixing degree between the third duct airflow and the mainstream.

[0017] As a further improvement to this technology, the angle between the central axis of the tail support plate and the generatrix of the front end of the outer plug cone is 60-90 degrees.

[0018] As a further improvement to this technology, the angle between the front generatrix of the spindle-shaped outer plug cone and its axis is 30 degrees.

[0019] As a further improvement to this technology, the angle between the rear end generatrix of the spindle-shaped outer plug cone and the rear end generatrix of the inner plug cone A is less than 10 degrees.

[0020] As a further improvement to this technology, the inner plug cone B slides inside the guide tube inside the inner plug cone A; several circumferentially evenly distributed baffles A are hinged at the tail end opening of the inner plug cone A to block the gap between the inner plug cone A and the inner plug cone B; each baffle A is fitted with a spiral spring at its hinge point to allow it to swing and reset.

[0021] Compared to traditional fighter jet engine exhaust systems, the outer plug cone, inner plug cone A, and inner plug cone B in this invention not only provide the aircraft engine with better high-altitude characteristics but also better infrared suppression. The outer plug cone, inner plug cone A, and inner plug cone B can shield high-temperature components such as the center cone or turbine, reducing infrared radiation. Simultaneously, the outer plug cone, inner plug cone A, and inner plug cone B themselves become new sources of infrared radiation. However, because they are located at the nozzle where the airflow velocity is high and the static pressure is low, they are cooled by the low-pressure cold air, thus effectively suppressing the infrared radiation from the outer plug cone, inner plug cone A, and inner plug cone B.

[0022] In this invention, the airflow behind the main throat is fast and has low pressure. The low-pressure airflow in the third duct is discharged from the airflow outlet of the third duct and mixes with the main airflow, thereby reducing the temperature of the main airflow and weakening the infrared radiation signal of the tail jet.

[0023] In this invention, when the airflow in the third duct passes through the outer plug cone, it cools the outer plug cone and wraps around the inner plug cone A and inner plug cone B, thereby reducing the infrared radiation signal of the outer plug cone, inner plug cone A and inner plug cone B.

[0024] This invention uses an adjusting sleeve to adjust the main flow throat, resulting in a simpler structure. The nozzle exit is adjusted via a first and second expansion adjusting plate, ensuring that the exposed dimensions of the inner plug cone B remain relatively constant during nozzle exit adjustment, thus minimizing changes in the infrared radiation signal of the inner plug cone B. The main flow throat and nozzle exit adjustment methods are implemented with a relatively simple structure and provide stable infrared suppression.

[0025] This invention adjusts the outlet area of ​​the third duct by using an inner plug cone B to ensure that the static pressure at the outlet of the third duct is essentially the same as the static pressure at the outlet of the main flow channel during cruising, thereby minimizing losses and saving fuel during airflow mixing. In other states, when the main flow throat needs to be reduced in size, the size of the main flow throat is adjusted by using an adjusting sleeve to control the airflow rate.

[0026] This invention has a simple structure and good performance. Attached Figure Description

[0027] Figure 1 This is a schematic cross-sectional view of the present invention and its overall structure.

[0028] Figure 2 This is a partial cross-sectional schematic diagram of the present invention.

[0029] Figure 3 This is a schematic diagram of the cross-sectional distribution of the first expansion adjustment plate, the second expansion adjustment plate, and the baffle B.

[0030] Figure 4 This is a schematic diagram of the cross-section of the inner plug cone A, the baffle A, and the inner plug cone B.

[0031] Figure 5 This is a schematic diagram of the actuation cross-section of the first expansion adjustment plate and the second expansion adjustment plate.

[0032] Figure 6 This is a schematic cross-sectional view of the structure connecting the outer plug cone and the third duct.

[0033] Figure 7 This is a schematic diagram of the inner plug cone A and its cross-section.

[0034] Figure 8 This is a schematic diagram of the first expansion adjustment plate, the corresponding second expansion adjustment plate, and the baffle B, and their cross-sectional view.

[0035] Figure 9 This is a schematic diagram showing the coordination between any two adjacent second expansion adjustment plates or between any two adjacent baffles B.

[0036] The labels in the diagram are as follows: 1. Outer casing; 2. Third casing; 3. Third duct; 4. Outer duct casing; 5. Power cylinder; 6. Inner casing; 7. Outer duct; 8. Inner duct; 9. Center cone; 10. Heat shield; 11. Tail support plate; 12. Outer plug cone; 13. Large lobe; 14. Support; 15. Inner plug cone A; 16. Guide cylinder; 17. Baffle A; 18. Spiral spring; 19. Inner plug cone B; 20. Actuator A; 21. Actuator B; 22. Actuator ring A; 23. Adjusting sleeve; 24. Ring sleeve; 25. First expansion adjusting plate; 26. Fixed rod; 27. Connecting rod A; 28. Connecting rod B; 29. ​​Actuator ring B; 30. Actuator C; 31. Second expansion adjusting plate; 32. Locking plate; 33. Baffle B; 34. Converging cylinder. Detailed Implementation

[0037] The accompanying drawings are schematic diagrams illustrating embodiments of the present invention to facilitate understanding of the structural operating principle. Specific product structures and dimensions can be determined based on the usage environment and conventional technologies.

[0038] like Figure 1 , 2 As shown in Figure 5, it also includes a tail support plate 11, an outer plug cone 12, a support 14, an inner plug cone A15, an inner plug cone B19, an actuating cylinder A20, an actuating cylinder B21, an adjusting sleeve 23, a ring sleeve 24, a first expansion adjusting plate 25, a second expansion adjusting plate 31, a baffle plate B33, and a converging cylinder 34, wherein... Figure 1 , 2 As shown in Figure 6, the third duct 3, which is closed at the end, is connected to a spindle-shaped outer plug cone 12 located in the middle of the tail nozzle and open at the tail end through a number of circumferentially evenly distributed tail support plates 11. An inner plug cone A15, forming the throat and airflow outlet of the annular third duct 3, is installed inside the outer plug cone 12 via a support 14. An inner plug cone B19, which adjusts the airflow outlet area of ​​the third duct 3 under the drive of the actuating cylinder A20, is axially sealed and slidable inside the inner plug cone A15. Figure 1 , 2 As shown in Figure 5, an adjusting sleeve 23, driven by four circumferentially evenly distributed actuating cylinders B21, slides axially inside the end of the third casing 2 to adjust the main flow throat; a converging cylinder 34, which forms the main flow convergence section with the outer plug cone 12, is installed at the end of the third duct 3. The throat of the third duct is located in front of the maximum radius of the inner plug cone 15.

[0039] like Figure 1 , 2 As shown in Figure 5, the end of the adjusting sleeve 23 is hinged with several circumferentially evenly distributed first expansion adjusting plates 25 that adjust the outlet area of ​​the main airflow; as shown in Figure 5. Figure 5 , 8As shown, each of the first expansion adjustment plates 25 has a second expansion adjustment plate 31 slidingly fitted on its outer side along its length; the first and second expansion adjustment plates form a contraction structure, and the end of the axially sealing sliding ring 24 at the end of the outer casing 1 is hinged with several baffles B33 corresponding one-to-one with the second expansion adjustment plates 31, and the end of each baffle B33 is hinged to the end of the corresponding second expansion adjustment plate 31; as Figure 2 , 5 As shown in Figures 9 and 1, the adjusting sleeve 23 and the first expansion adjusting plate 25 have a structure that drives the first expansion adjusting plate 25 and the second expansion adjusting plate 31 to swing synchronously in a contracting or expanding manner.

[0040] The position of the ring 24 can control the position of the hinge point between the baffle B33 and the second expansion adjustment plate 31, i.e. the end of the nozzle outlet. It can be used to adjust the degree of leakage of the plug cone during the exhaust system test phase. When in formal use, the sliding of the ring 24 and the outer casing is locked and no longer has a sliding relationship.

[0041] A connecting rod A27 is hinged to the fixing rod 26 on the outer side of the first expansion adjustment plate 25. A connecting rod B28 is hinged to the end of the connecting rod A27. The connecting rod B28 is hinged to the actuating ring B29 nested and sliding on the adjustment sleeve 23. The actuating ring B29 is driven by four actuating cylinders C30 that are circumferentially and evenly installed on the adjustment sleeve 23.

[0042] like Figure 2 , 5 As shown, an actuating ring A22, which is connected to the adjusting sleeve 23, is nested and slidably mounted on the outer side of the end of the third housing 2. The actuating ring A22 is driven by four actuating cylinders B21 that are evenly distributed circumferentially on the outer side of the third housing 2.

[0043] like Figure 3 , 9 As shown, the inner side of the second expansion adjustment piece 31 located on the outer side of all the second expansion adjustment pieces 31 has a locking piece 32 that cooperates with the adjacent second expansion adjustment pieces 31 on both sides.

[0044] like Figure 3 , 9 As shown, the inner side of the outermost baffle B33 has a locking piece 32 that cooperates with the adjacent baffles B33 on both sides.

[0045] like Figure 2 , 5 As shown in Figures 6 and 7, the outer plug cone 12 has large lobes 13 evenly distributed circumferentially at the tail opening end to increase the mixing degree between the airflow in the third duct 3 and the mainstream.

[0046] like Figure 5 As shown, the angle between the central axis of the tail support plate 11 and the generatrix of the front end of the outer plug cone 12 is 60-90 degrees.

[0047] like Figure 5 As shown, the angle between the front generatrix of the spindle-shaped outer plug cone 12 and its axis is 30 degrees.

[0048] like Figure 5 As shown, the angle between the rear end generatrix of the spindle-shaped outer plug cone 12 and the rear end generatrix of the inner plug cone A15 is less than 10 degrees.

[0049] like Figure 2 , 4 As shown in Figure 7, the inner plug cone B19 slides within the guide cylinder 16 inside the inner plug cone A15; several circumferentially evenly distributed baffles A17 are hinged at the tail end opening of the inner plug cone A15 to block the gap between the inner plug cone A15 and the inner plug cone B19; each baffle A17 is fitted with a spiral spring 18 at its hinge point to reset its swing.

[0050] When the adjusting sleeve moves, the retractability of the first and second expansion adjusting plates ensures that the leakage of the inner plug cone does not change much when the adjusting sleeve moves to adjust the main throat.

[0051] The workflow of this invention: Different flight states of an aircraft have different requirements for the engine. The engine itself meets the different flight state requirements of the aircraft by adjusting the airflow throat and airflow outlet area through its exhaust system.

[0052] The airflow from the inner duct 8 and the airflow from the outer duct 7 in the engine mix in the afterburner 5 to form the mainstream airflow. The mainstream airflow is discharged through the annular mainstream throat formed between the outer plug cone 12 and the adjusting sleeve 23, and through the outlet formed by the outer plug cone 12, the first expansion adjusting plate 25, and the second expansion adjusting plate 31. Meanwhile, the airflow in the third duct 3 enters the outer plug cone 12 through the tail support plate 11 and is discharged through the throat formed between the inner plug cone A15 and the outer plug cone 12, and through the outlet formed by the inner plug cone B19 and the large wave lobe 13 on the outer plug cone 12. The discharged airflow from the third duct 3 is mixed in the space between the inner plug cone B19 and the first expansion adjusting plate 25 and the second expansion adjusting plate 31 at the tail of the nozzle and is discharged from the tail of the nozzle.

[0053] In this invention, the throat of the third duct 3 is located in front of the maximum radius of the inner plug cone A15, and its area is fixed and cannot be adjusted. This invention adjusts the airflow outlet area of ​​the third duct 3 by activating the actuator A20 to drive the inner plug cone B19 to move axially relative to the inner plug cone A15, so as to ensure that the airflow of the third duct is balanced with the static pressure of the mainstream and reduce losses.

[0054] This invention adjusts the main flow throat by activating four actuators B21 to drive the adjusting sleeve 23 to move axially relative to the outer plug cone 12. It also adjusts the angle between the first and second expansion adjusting plates 25 and 31 and the central axis by activating four actuators C30 to drive the first expansion adjusting plate 25 and 31 to swing, thereby adjusting the main flow outlet area. During adjustment, the sliding of the ring 24 and the outer casing 1 is locked. When the first and second expansion adjusting plates 25 and 31 are adjusted, the outer baffle B33 can only swing. The extension and retraction of the first and second expansion adjusting plates 25 and 31 ensure that they can be adjusted and swung to adjust the nozzle outlet. The adjustment of the main outlet area by the first expansion adjustment plate 25 and the second expansion adjustment plate 31 ensures that the exposed size of the inner plug cone B19 changes little, thereby ensuring that the visible area of ​​the inner plug cone B19 changes little, and thus the infrared radiation signal changes little. The sliding of the ring sleeve 24 and the outer casing ensures the adjustment of the degree of plug cone exposure. It can be used in the aircraft testing phase. After subsequent deployment, the ring sleeve 24 and the outer casing can be fixed.

[0055] In summary, the beneficial effects of this invention are as follows: the outer plug cone 12, inner plug cone A15, and inner plug cone B19 of this invention not only give the aircraft engine better high-altitude characteristics but also better infrared suppression. The outer plug cone 12, inner plug cone A15, and inner plug cone B19 can shield high-temperature components such as the center cone 9 or turbine, reducing infrared radiation. Simultaneously, the outer plug cone 12, inner plug cone A15, and inner plug cone B19 themselves become new sources of infrared radiation. However, because they are located at the nozzle where the airflow velocity is high and the static pressure is low, the outer plug cone 12, inner plug cone A15, and inner plug cone B19 are cooled by the low-pressure cold air, thereby effectively suppressing the infrared radiation of the outer plug cone 12, inner plug cone A15, and inner plug cone B19.

[0056] In this invention, the airflow behind the main throat is fast and has low pressure. The low-pressure airflow in the third duct 3 is discharged from the airflow outlet of the third duct 3 and mixes with the main airflow, thereby reducing the temperature of the main airflow and weakening the infrared radiation signal of the tail jet.

[0057] In this invention, when the airflow in the third duct 3 passes through the outer plug cone 12, it cools the outer plug cone 12 and wraps around the inner plug cone A15 and the inner plug cone B19, thereby reducing the temperature and infrared radiation signal of the outer plug cone 12, the inner plug cone A15 and the inner plug cone B19.

[0058] This invention adjusts the main flow throat by adjusting the sleeve 23, resulting in a simpler structure. The nozzle exit is adjusted via the first expansion adjustment plate 25 and the second expansion adjustment plate 31, ensuring that the exposed dimensions of the inner plug cone B19 do not change significantly during nozzle exit adjustment, thus minimizing changes in the infrared radiation signal of the inner plug cone B19. The main flow throat adjustment method and the nozzle exit adjustment method are implemented with a relatively simple structure and provide stable infrared suppression.

[0059] This invention uses the inner plug cone B19 to adjust the outlet area of ​​the third duct 3, ensuring that the static pressure of the third duct airflow at the outlet of the third duct 3 is basically the same as the static pressure at the outlet of the mainstream flow channel during cruise, thereby ensuring that the aerodynamic loss during the airflow mixing process is small. When it is necessary to adjust the airflow rate of the third duct, after controlling the inner plug cone B19 to adjust the outlet area of ​​the third duct 3 to be smaller than the throat area, the outlet of the third duct becomes a new throat. At this time, the flow rate of the third duct is adjusted by adjusting the outlet area of ​​the third duct. In this process, it is impossible to guarantee that the static pressure at the outlet of the third duct is close to the static pressure of the mainstream. That is, this process makes a trade-off between the adjustment of the third duct flow rate and the static pressure balance.

Claims

1. A low-infrared-signature adaptive variable-cycle engine exhaust system with a plug cone, comprising an outer casing, a third casing, a third bypass duct, an outer bypass casing, an afterburner, an inner casing, an outer bypass duct, an inner duct, a center cone, and a heat shield, characterized in that: It also includes a tail support plate, an outer plug cone, a support, an inner plug cone A, an inner plug cone B, an actuator A, an actuator B, an adjusting sleeve, a ring sleeve, a first expansion adjusting plate, a second expansion adjusting plate, a baffle B, and a convergent cylinder. The third duct, which is closed at the end, is connected to a spindle-shaped outer plug cone located in the middle of the tail nozzle and open at the tail end through several circumferentially evenly distributed tail support plates. The outer plug cone is supported and installed with an inner plug cone A, which forms an annular third duct throat and an annular third duct airflow outlet. The inner plug cone B is axially sealed and slidable in the inner plug cone A, which adjusts the airflow outlet area of ​​the third duct under the drive of the actuator A. An adjusting sleeve that adjusts the main flow throat under the drive of four circumferentially evenly distributed actuators B is axially slidable in the end of the third casing. A convergent cylinder that forms a main flow convergent section with the outer plug cone is installed at the end of the third duct. The adjusting sleeve has several circumferentially evenly distributed first expansion adjusting plates at its end, which adjust the outlet area of ​​the main airflow. Each first expansion adjusting plate has a second expansion adjusting plate slidingly fitted on its outer side along its length. The end of the axially sealing sliding ring at the end of the outer casing has several baffles B that correspond one-to-one with the second expansion adjusting plates. The end of each baffle B is hinged to the end of the corresponding second expansion adjusting plate. The adjusting sleeve and the first expansion adjusting plates have a structure that drives the first and second expansion adjusting plates to swing synchronously in a contracting or expanding manner.

2. The low-infrared-signature adaptive variable-cycle engine exhaust system with a plug cone according to claim 1, characterized in that: A connecting rod A is hinged to the fixed rod on the outer side of the first expansion adjustment plate, and a connecting rod B is hinged to the end of the connecting rod A. The connecting rod B is hinged to the actuating ring B nested and sliding on the adjustment sleeve. The actuating ring B is driven by four actuating cylinders C that are circumferentially and evenly installed on the adjustment sleeve.

3. The low-infrared-signature adaptive variable-cycle engine exhaust system with a plug cone according to claim 1, characterized in that: An actuating ring A, which is connected to an adjusting sleeve, is nested and slidably mounted on the outer side of the end of the third housing. The actuating ring A is driven by four actuating cylinders B that are evenly distributed circumferentially on the outer side of the third housing.

4. The low-infrared-signature adaptive variable-cycle engine exhaust system with a plug cone according to claim 1, characterized in that: All of the second expansion adjustment pieces have a locking piece on the inner side of the outermost second expansion adjustment piece that cooperates with the adjacent second expansion adjustment pieces on both sides.

5. The low-infrared adaptive variable cycle engine exhaust system with a plug cone according to claim 1, characterized in that: All of the baffles B are provided with a locking tab on the inner side of the outer baffle B that cooperates with the adjacent baffles B on both sides.

6. The low-infrared-signature adaptive variable-cycle engine exhaust system with a plug cone according to claim 1, characterized in that: The outer plug cone has large lobes evenly distributed circumferentially at its tail opening end, which increase the mixing degree between the third duct airflow and the mainstream.

7. The low-infrared adaptive variable cycle engine exhaust system with a plug cone according to claim 1, characterized in that: The angle between the central axis of the tail support plate and the generatrix of the front end of the outer plug cone is 60-90 degrees.

8. The low-infrared-signature adaptive variable-cycle engine exhaust system with a plug cone according to claim 1, characterized in that: The angle between the front generatrix of the spindle-shaped outer plug cone and its axis is 30 degrees.

9. The low-infrared-signature adaptive variable-cycle engine exhaust system with a plug cone according to claim 1, characterized in that: The angle between the rear generatrix of the spindle-shaped outer plug cone and the rear generatrix of the inner plug cone A is less than 10 degrees.

10. The low-infrared-signature adaptive variable-cycle engine exhaust system with a plug cone according to claim 1, characterized in that: The inner cone B slides inside the guide tube within the inner cone A; several circumferentially evenly distributed baffles A are hinged at the tail end opening of the inner cone A to block the gap between the inner cone A and the inner cone B; each baffle A is fitted with a spiral spring at its hinge point to allow it to swing and reset.

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