Three-duct S-bend nozzle for adaptive cycle engine with hot spot cooling structure

Abstract

The present invention discloses a three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure, which belongs to the field of aeroengines; it includes a convergent section, an expansion section, a third duct and a mixing section; the third duct and the mixing section are arranged at the outlet end of the nozzle expansion section; the third duct includes an upper third duct, a lower third duct, an air bleed structure and a cooling channel; the upper third duct and the lower third duct are respectively arranged on the outer sides of the upper and lower wall surfaces of the nozzle expansion section outlet end, and the gap arranged between the upper third duct and the upper wall surface of the nozzle expansion section outlet end serves as a cooling channel, and the inlet of the gap is an air bleed structure; the main airflow ejected from the nozzle expansion section and the secondary airflow ejected from the ducts of the upper and lower third ducts are mixed in the mixing section; part of the secondary airflow in the upper third duct enters the cooling channel through the air bleed structure, and then is discharged from both sides of the gap. The present invention solves the problem of a hot spot generated on the upper wall surface of the outlet of the existing three-duct S-bend nozzle, which causes a strong infrared radiation feature.

Description

Technical Field

[0001] The invention belongs to the field of aviation engines, and in particular relates to a three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure. Background Art

[0002] The three-duct S-bend nozzle is an important component for reducing the infrared radiation intensity of the exhaust system and enhancing the stealth capability of the aircraft. The center of the nozzle inlet is a high-temperature inner airflow, and the outside is a low-temperature outer airflow. Under the protection of the outer airflow, most of the nozzle wall is not in contact with the inner high-temperature airflow, so the temperature is relatively low. However, at the nozzle outlet, due to the curved shape, the high-temperature gas will pass through the low-temperature gas and directly contact the nozzle wall, which will inevitably produce a hot spot on the outlet wall that can emit a strong infrared radiation intensity. Therefore, on the basis of not affecting the internal flow, reducing the temperature of the hot spot on the nozzle outlet wall through external heat dissipation is a crucial link in reducing the infrared radiation intensity of the three-duct S-bend nozzle for adaptive engines.

[0003] The three-duct S-bend nozzle disclosed in the prior art is provided with spoiler ribs at the mainstream outlet of the nozzle, but the spoiler ribs prevent the hot spots generated by the mainstream gas on the upper wall of the nozzle from dissipating heat outwards and affect the entry of the third airflow, thereby affecting the flow of the airflow. Summary of the invention

[0004] Technical issues to be solved:

[0005] In order to avoid the shortcomings of the prior art, the present invention provides a three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure, which adopts a nozzle convergence section, a nozzle expansion section, a mixing section, an upper third duct, a lower third duct, an air bleed structure and a cooling channel structure to solve the problem of hot spots generated on the upper wall surface of the outlet in the existing three-duct S-bend nozzle, resulting in strong infrared radiation characteristics.

[0006] The technical solution of the present invention is: a three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure, comprising a nozzle convergent section, a nozzle expansion section, a third duct and a mixing section; the inlet of the nozzle convergent section serves as the inlet of the S-bend nozzle, and the connection between its outlet and the inlet of the nozzle expansion section serves as the nozzle throat; the third duct and the mixing section are arranged at the outlet end of the nozzle expansion section; the third duct comprises an upper third duct, a lower third duct, an air bleed structure and a cooling channel; the upper third duct and the lower third duct are respectively arranged on the outer sides of the upper and lower wall surfaces of the outlet end of the nozzle expansion section, the gap arranged between the upper third duct and the upper wall surface of the outlet end of the nozzle expansion section serves as a cooling channel, and the inlet of the gap is an air bleed structure;

[0007] The main airflow ejected from the nozzle expansion section and the secondary airflow ejected from the upper and lower third ducts are mixed in the mixing section; part of the secondary airflow in the upper third duct enters the cooling channel through the air bleed structure and is then discharged from both sides of the gap.

[0008] A further technical solution of the present invention is: the air induction structure adopts a downward convex induction design to divert the secondary airflow in the upper third duct from the third duct and partially introduce it into the cooling channel.

[0009] A further technical solution of the present invention is: the air bleed structure includes a front support plate, a drainage chute and a leak-proof side plate; the front support plate is a lower channel plate of the upper third duct, and the gap between the front support plate and the upper wall surface of the nozzle expansion section is the cooling channel, which is provided with a notch at the front end of the inlet, and the air flow in the upper third duct is split at the notch, with one part flowing through the upper surface of the front support plate of the upper third duct and the other part flowing through the drainage chute from the notch;

[0010] The drainage chute is arranged at the entrance of the gap, the upper edge coincides with the lower edge of the entrance of the upper third duct, and the lower edge is fixed to the upper wall of the nozzle expansion section, which is used to introduce part of the airflow in the upper third duct into the cooling channel; the two anti-leakage side plates are arranged on both sides of the drainage chute to laterally close the drainage chute to prevent air leakage along the left and right sides when the airflow flows through the drainage chute.

[0011] A further technical solution of the present invention is that the drainage chute is an arc-shaped plate, and the lower end of the plate is tangent to the upper wall surface of the nozzle expansion section.

[0012] A further technical solution of the present invention is: a cooling channel structure is arranged in the cooling channel, and the cooling channel structure includes a plurality of symmetrically arranged guide vanes, and the airflow entering the cooling channel is discharged along the left and right sides of the nozzle under the action of the guide vanes.

[0013] A further technical solution of the present invention is: the cooling channel structure includes five groups of guide vanes, the upper ends of which are fit-connected to the lower channel plate of the upper third duct, and the lower ends are fit-connected to the upper wall surface of the nozzle expansion section; the five groups of guide vanes are arranged in sequence from the symmetrical surface of the nozzle to the outside.

[0014] A further technical solution of the present invention is that the guide vane is in a crescent shape, and the crescent geometric shape is composed of two arcs with different diameters, the radius of the arcs differs by 1 / 15 of the nozzle outlet width, and the centers of the arcs are both located on the outside.

[0015] A further technical solution of the present invention is: four groups of guide vanes among the five groups of guide vanes are axially connected to the outlet of the air bleed structure, the spanwise distances between each starting point and the side wall of the nozzle are 1 / 6, 1 / 4, 1 / 3 and 3 / 8 of the nozzle width, respectively, and the axial lengths are 1 / 2, 2 / 3, 5 / 6 and 5 / 6 of the axial length of the cooling channel, respectively, wherein the ends of three groups of guide vanes lead to the outlets on both sides of the gap, and the ends of another group of guide vanes extend inward and are 1 / 3 away from the side wall of the nozzle; the spanwise position of the starting point of the fifth group of guide vanes is 1 / 3 away from the side wall of the nozzle, the axial position is 1 / 3 of the axial length of the cooling channel from the outlet of the air bleed structure, the lateral position of the end is 1 / 5 of the nozzle width from the side wall of the nozzle, and the axial position is 5 / 6 of the cooling channel length.

[0016] A further technical solution of the present invention is: the nozzle convergent section and the nozzle divergent section are both S-shaped, the nozzle convergent section inlet is circular, including an inner inlet and an outer inlet, and the outlet is rectangular; the nozzle divergent section inlet is smoothly connected with the nozzle convergent section outlet, and the outlet is rectangular; wherein the axial length ratio of the nozzle convergent section to the divergent section is between 1:2 and 1:4, and the width-to-height ratio of the outlet rectangle is between 3 and 6.

[0017] A further technical solution of the present invention is: the upper and lower third ducts both include upper, lower, left and right side channel plates, forming a duct with a rectangular radial cross-section, whose width is consistent with the width of the nozzle expansion section, and the axial length is 2 / 3 of the axial length of the nozzle convergence section; the upper and lower third duct outlets are in the same axial position as the nozzle expansion section outlet, and both are connected to the mixing section inlet, and the mixing section outlet is the nozzle outlet.

[0018] Beneficial Effects

[0019] The beneficial effects of the present invention are as follows: the three-duct S-bend nozzle with a hot spot cooling structure for an adaptive cycle engine using the technical solution of the present invention introduces part of the airflow from the upper third duct into a cooling channel structure containing five groups of guide vanes symmetrically distributed along the center plane of the nozzle, and introduces gas to cool the hot spots on the upper wall of the nozzle; the air bleed structure will not affect the third airflow while introducing the third airflow, so that the flow characteristics do not change; the cooling channel structure can make the introduced airflow flow as required to cool hot spots of different sizes; because the hot spots are concentrated at the center of the upper wall of the nozzle expansion section outlet, the difficulty of the present invention lies in how to distribute more of the introduced airflow to the center and increase the turbulence of the airflow.

[0020] The wall temperature distribution diagram of the double-ducted S-bend nozzle was obtained from the 6th issue of Volume 39 of the Journal of Aerospace Power in December 2021, pages 1331-1339. It can be seen from the figure that a hot spot will be generated on the upper wall of the double-ducted S-bend nozzle outlet, and a strong infrared radiation signal will be emitted to the rear. Therefore, the adaptive cycle engine with a hot spot cooling structure proposed in the present invention uses a three-ducted S-bend nozzle, which adds upper and lower third ducts on the basis of the double duct. On the one hand, the airflow of the upper and lower third ducts can adjust the flow field of the mainstream airflow. On the other hand, by allowing part of the airflow of the upper third duct to enter the bleed structure, the cooling airflow of the third duct enters the cooling channel, which can realize the heat exchange of the cold airflow with the hot spot and play a role in heat dissipation, thereby reducing the temperature of the hot spot and reducing the thermal radiation intensity of the hot spot.

[0021] The five groups of guide vanes in the present invention are arranged in a certain step order and placed according to the parameters given in the present invention. First, the cooling airflow can be better distributed, so that the airflow can have a better heat dissipation effect; second, it can increase the turbulence of the airflow and ensure that the airflow is discharged more smoothly, so that it will not accumulate at the hot spot and cause a decrease in heat dissipation efficiency; third, the flow channel formed by the guide vanes presents a contraction shape, and the airflow will accelerate when passing through, thereby further enhancing the heat exchange effect. Therefore, according to the definition of the parameters in the present invention, on the one hand, the wall hot spots can be cooled without affecting the flow of the third duct airflow on the upper and lower sides, and on the other hand, the cooling airflow and the wall surface have a better heat exchange capacity. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 Schematic diagram of a three-duct S-bend nozzle with a hot spot cooling structure for a turbofan engine, which can be selected according to an embodiment of the present invention;

[0023] Figure 2 It is a schematic diagram of a three-ducted S-bend nozzle bleed air structure with a hot spot cooling structure for a turbofan engine that can be selected according to an embodiment of the present invention;

[0024] Figure 3 It is a schematic diagram of a cooling channel structure of a three-duct S-bend nozzle with a hot spot cooling structure for a turbofan engine, which can be selected according to an embodiment of the present invention;

[0025] Figure 4 It is a partial cross-sectional view of a cooling channel of a three-duct S-bend nozzle with a hot spot cooling structure for a turbofan engine, which can be selected according to an embodiment of the present invention;

[0026] Figure 5 This is a top view of the interior of a three-duct S-bend nozzle cooling channel with a hot spot cooling structure for a turbofan engine that can be selected according to an embodiment of the present invention.

[0027] Explanation of the reference numerals in the accompanying drawings: 1. Converging section of the nozzle: 12. Inlet of the outer duct, 13. Inlet of the inner duct; 2. Expanding section of the nozzle; 3. The third duct on the lower side: 31. Inlet of the third duct on the lower side, 32. The upper channel plate of the third duct on the lower side, 33. The lower channel plate of the third duct on the lower side; 4. Air bleed structure: 41. Inlet of the air bleed structure, 42. Drainage chute, 43. Front support plate, 44. Leakage-proof side plate, 45. Outlet of the air bleed structure; 5. Cooling channel structure: 50. Inlet of the cooling channel, five groups of guide vanes (51, 52, 53, 54 and 55), and side outlets (56, 57, 58 and 59); 6. The third duct on the upper side; 7. Mixing section. DETAILED DESCRIPTION

[0028] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0029] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0030] The present invention discloses a three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure, comprising a nozzle convergent section, a nozzle divergent section, a third duct and a mixing section; the nozzle convergent section and the nozzle divergent section are both S-shaped, the nozzle convergent section inlet is circular, including an inner inlet and an outer inlet, and the outlet is quasi-rectangular; the inlet of the nozzle convergent section serves as the S-bend nozzle inlet, and the connection between the outlet and the inlet of the nozzle divergent section is the nozzle throat; wherein the axial length ratio of the nozzle convergent section to the divergent section is between 1:2 and 1:4, and the width-to-height ratio of the outlet rectangle is between 3 and 6.

[0031] The third duct and the mixing section are arranged at the outlet end of the nozzle expansion section; the third duct includes an upper third duct, a lower third duct, an air bleed structure and a cooling channel; the upper third duct and the lower third duct are respectively arranged on the outer side of the upper and lower walls of the nozzle expansion section outlet end, and both include upper, lower, left and right channel plates, forming a channel with a rectangular radial cross section, whose width is consistent with the width of the nozzle expansion section, and the axial length is 2 / 3 of the axial length of the nozzle convergence section; the outlets of the upper and lower third ducts are in the same axial position as the outlet of the nozzle expansion section, and both are connected to the inlet of the mixing section, and the outlet of the mixing section is the nozzle outlet. Among them, the end of the lower channel plate of the upper third duct is connected to the end of the upper wall of the nozzle expansion section through a radial connecting plate, which is used to support and connect the upper third duct and the airflow guide; the end of the upper channel plate of the lower third duct is connected to the end of the lower wall of the nozzle expansion section through a radial connecting plate, which is used to support and connect the lower third duct.

[0032] The gap arranged between the upper third duct and the upper wall surface at the outlet end of the nozzle expansion section serves as a cooling channel, and the inlet of the gap is an air entrainment structure; the main airflow ejected from the nozzle expansion section and the secondary airflow ejected from the ducts of the upper and lower third ducts are mixed in the mixing section; part of the secondary airflow in the upper third duct enters the cooling channel through the air entrainment structure, and then is discharged from both sides of the gap.

[0033] like Figure 1 As shown, in this embodiment, a three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure comprises: a nozzle convergent section 1, a nozzle expansion section 2, a lower third duct 3, an air bleed structure 4, a cooling channel structure 5, an upper third duct 6, and a mixing section 7. Two airflows enter the inlet of the nozzle convergent section 1, namely, a high-temperature inlet 13 for the inner airflow and a low-temperature inlet 12 for the outer airflow. The two airflows flow in from the inlet of the convergent section 1 and flow into the expansion section 2 through the outlet 14 of the convergent section 1. The main airflow merges with the third airflow entering the upper third duct 6 through the lower third duct 3 and the air bleed structure inlet 41 and enters the mixing section 7. After passing through the air bleed structure inlet 41, part of the airflow passes through the drainage chute 42 and enters the drainage cooling channel 5. After passing through the five groups of guide vanes 51, 52, 53, 54, and 55 of the drainage cooling channel, the airflow cools and discharges the hot spot 9 on the wall surface of the expansion section outlet 8, thereby achieving the purpose of reducing the temperature of the hot spot.

[0034] The adaptive cycle engine with a hot spot cooling structure using the technical solution of the present invention uses a three-duct S-bend nozzle. Through the guide vanes 51, 52, 53, 54, 55 in the air bleed structure 4 and the bleed cooling channel 5, part of the gas introduced at the air bleed structure inlet 41 cools the upper wall surface 8 of the nozzle expansion section outlet 9, and is discharged symmetrically from the side outlets 56, 57, 58, 59 of the nozzle, without causing a serious impact on the airflow at the mixing outlet 7, reducing the infrared radiation intensity while having no impact on the aerodynamic performance of the nozzle.

[0035] Specifically, Figure 1 As shown, the main body of the nozzle convergent section 1 is a cavity from circular to square, which is connected to the main body of the nozzle expansion section at 14. The third airflow enters from the lower third duct 3 and the inlet 41 of the diversion section respectively, and after merging with the airflow passing through the nozzle convergent section 1 and the nozzle expansion section 2, it is discharged through the nozzle mixing section 7.

[0036] like Figure 2 , 4 As shown, the air bleed structure 4 adopts a downward convex drainage design, which diverts the secondary airflow in the upper third duct from the third duct and partially introduces it into the cooling channel. Its main body includes a drainage chute 42, a leakproof side plate 44, and a front support plate 43. The front support plate 43 is the lower channel plate of the upper third duct. The gap between the front support plate 43 and the upper wall of the nozzle expansion section is the cooling channel, and a gap is opened at the front end of the inlet; the third airflow passes through the cavity of the third duct, and under the action of the front support plate 43, one airflow continues to flow backward, and the other airflow enters from the gap and flows through the drainage chute 42 and enters the cooling channel inlet 50; in order to prevent the airflow from flowing out from the side of the nozzle, leakproof side plates 44 are set on both sides of the drainage chute 42, and the leakproof side plates 44 only seal the airflow at the drainage chute; the drainage chute 42 is an arc-shaped plate, and its lower end is tangent to the upper wall of the nozzle expansion section. The drainage chute 42 and the anti-leakage side plate 44 guide the airflow into the cooling channel structure 5 .

[0037] like Figure 3 , 5 As shown, a cooling channel structure 5 is provided in the cooling channel, and the cooling channel structure 5 includes a plurality of groups of symmetrically arranged guide vanes. The airflow entering the cooling channel is discharged along the left and right sides of the nozzle under the action of the guide vanes. The cooling channel structure 5 is mainly composed of five groups of axially symmetrical guide vanes 51, 52, 53, 54, and 55. Each group of guide vanes includes two guide vanes symmetrically arranged with respect to the nozzle symmetry plane. The guide vane is supported by the lower wall of the third duct on the upper side and the upper wall of the nozzle expansion section near the outlet on the lower side. The shape of the guide vane is crescent-shaped. The crescent geometric shape is composed of two arcs of different diameters. The radius of the arcs differs by 1 / 15 of the nozzle outlet width, but the length and placement position are different.

[0038] Four of the five groups of guide vanes are axially connected to the outlet of the air bleed structure, with starting points laterally 1 / 6, 1 / 4, 1 / 3 and 3 / 8 of the nozzle width away from the nozzle side wall, and axial lengths of 1 / 2, 2 / 3, 5 / 6 and 5 / 6 of the axial length of the cooling channel, respectively. Three groups of guide vanes are in contact with the side wall outlet, and the other group of guide vanes extends inward and ends at 1 / 3 of the nozzle side wall; the front end of the fifth group of blades is laterally positioned at 1 / 3 of the nozzle side wall, and longitudinally positioned at 1 / 3 of the channel axial length away from the outlet of the air bleed structure, and the end is laterally positioned at 1 / 5 of the nozzle width away from the nozzle side wall, and longitudinally at 5 / 6 of the cooling channel length. After the guide air flow passes through the cooling channel inlet 50, it enters the cooling channel 5. First, the air flow is diverted at the front end of the guide vanes 51, 52, 53, and 55. After a part of the air flow passes through the guide vane group 51, 52, and 53, it flows out from the side outlets 56, 57, and 58. Finally, the largest part of the flow passes through the channel directly between the guide vanes 53 and 55, and is diverted by the guide vane 54 and flows out through the side outlet 59. Since the high-temperature hot spot is close to the wall of the support plate, the guide vane 55 increases the turbulence of the air flow. Therefore, the guide vane 55 not only guides the air flow, but also enhances the heat exchange of the air flow. Figure 2 Figure 3 and Figure 4 respectively show the axonometric views of the cooling channel structure including and excluding the upper third duct.

[0039] like Figure 4 and Figure 5 As shown, the nozzle bleed structure 4 and the cooling channel structure 5 are determined by the nozzle structure to be cooled, and can be any type of nozzle structure, and the guide vanes 51, 52, 53, 54, 55 proposed in the cooling channel structure 5, their shape, number and position can be determined by the position and shape of the hot spot to be cooled. The present invention adopts five groups of guide vanes symmetrically distributed along the symmetric plane of the nozzle, and according to Figure 3 The nozzle is placed in the shape, size and position given in the figure, and the overall nozzle takes the three-duct S-bend divergent nozzle as an example.

[0040] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure, comprising a nozzle convergent section, a nozzle divergent section, a third duct and a mixing section; the inlet of the nozzle convergent section serves as the S-bend nozzle inlet, and the connection between the outlet and the inlet of the nozzle divergent section serves as the nozzle throat; the third duct and the mixing section are arranged at the outlet end of the nozzle divergent section; characterized in that: The third duct comprises an upper third duct, a lower third duct, an air bleed structure and a cooling channel; the upper third duct and the lower third duct are respectively arranged on the outer sides of the upper and lower walls of the nozzle expansion section outlet end, the gap arranged between the upper third duct and the upper wall of the nozzle expansion section outlet end serves as a cooling channel, and the inlet of the gap is an air bleed structure; The main airflow ejected from the nozzle expansion section and the secondary airflow ejected from the upper and lower third ducts are mixed in the mixing section; part of the secondary airflow in the upper third duct enters the cooling channel through the air bleed structure and is then discharged from both sides of the gap.

2. The three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure according to claim 1, characterized in that: The air induction structure adopts a downward convex induction design, which diverts the secondary airflow in the upper third duct from the third duct and partially introduces it into the cooling channel.

3. The three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure according to claim 1, characterized in that: The air bleed structure includes a front support plate, a drainage chute and a leak-proof side plate; the front support plate is the lower channel plate of the upper third duct, and the gap between the front support plate and the upper wall of the nozzle expansion section is the cooling channel, which has a notch at the front end of the inlet, and the air flow in the upper third duct is split at the notch, with one part flowing through the upper surface of the front support plate of the upper third duct and the other part flowing through the drainage chute from the notch; The drainage chute is arranged at the entrance of the gap, the upper edge coincides with the lower edge of the entrance of the upper third duct, and the lower edge is fixed to the upper wall of the nozzle expansion section, which is used to introduce part of the airflow in the upper third duct into the cooling channel; the two anti-leakage side plates are arranged on both sides of the drainage chute to laterally close the drainage chute to prevent air leakage along the left and right sides when the airflow flows through the drainage chute.

4. The three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure according to claim 3, characterized in that: The drainage chute is an arc-shaped plate, and the lower end thereof is tangent to the upper wall surface of the nozzle expansion section.

5. A three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure according to any one of claims 1 to 4, characterized in that: A cooling channel structure is arranged in the cooling channel, and the cooling channel structure includes a plurality of symmetrically arranged guide vanes. The airflow entering the cooling channel is discharged along the left and right sides of the nozzle under the action of the guide vanes.

6. The three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure according to claim 5, characterized in that: The cooling channel structure includes five groups of guide vanes, the upper ends of which are fitted and connected to the lower channel plate of the upper third duct, and the lower ends of which are fitted and connected to the upper wall surface of the nozzle expansion section; the five groups of guide vanes are arranged in sequence from the symmetrical surface of the nozzle to the outside.

7. The three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure according to claim 6, characterized in that: The guide vane is in a crescent shape, and the crescent geometric shape is composed of two arcs with different diameters. The radius of the arcs differs by 1 / 15 of the nozzle outlet width, and the centers of the arcs are both located on the outside.

8. The three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure according to claim 7, characterized in that: Among the five groups of guide vanes, four groups of guide vanes are axially connected to the outlet of the air bleed structure, and the spanwise distances between each starting point and the side wall of the nozzle are 1 / 6, 1 / 4, 1 / 3 and 3 / 8 of the nozzle width, respectively, and the axial lengths are 1 / 2, 2 / 3, 5 / 6 and 5 / 6 of the axial length of the cooling channel, respectively. The ends of three groups of guide vanes lead to the outlets on both sides of the gap, and the ends of another group of guide vanes extend inward and are 1 / 3 away from the side wall of the nozzle; the starting point of the fifth group of guide vanes is spanwise located at 1 / 3 of the distance from the side wall of the nozzle, and the axial position is 1 / 3 of the axial length of the cooling channel from the outlet of the air bleed structure, the lateral position of the end is 1 / 5 of the nozzle width from the side wall of the nozzle, and the axial position is 5 / 6 of the length of the cooling channel.

9. The three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure according to claim 1, characterized in that: The nozzle convergent section and the nozzle divergent section are both S-shaped, the nozzle convergent section inlet is circular, including an inner inlet and an outer inlet, and the outlet is rectangular; the nozzle divergent section inlet is smoothly connected to the nozzle convergent section outlet, and the outlet is rectangular; the axial length ratio of the nozzle convergent section to the divergent section is between 1:2 and 1:4, and the width-to-height ratio of the outlet rectangle is between 3 and 6.

10. The three-duct S-bend nozzle for an adaptive cycle engine with a hot spot cooling structure according to claim 1, characterized in that: The upper and lower third ducts both include upper, lower, left and right side channel plates, forming a duct with a rectangular radial cross-section, whose width is consistent with the width of the nozzle expansion section, and the axial length is 2 / 3 of the axial length of the nozzle convergence section; the upper and lower third duct outlets are in the same axial position as the nozzle expansion section outlet, and both are connected to the mixing section inlet, and the mixing section outlet is the nozzle outlet.

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