Binary convergent-divergent nozzle with composite gas film cooling structure

Abstract

The present application belongs to the technical field of cooling design of nozzle, and particularly relates to a two-dimensional converging-diverging nozzle with a composite gas film cooling structure, which comprises a main flow channel and two sub-flow channels distributed on the upper and lower parts of the main flow channel, and an outer wall surface structure of the nozzle is designed, and a flow guide structure is designed at different positions of the outer wall surface, so that the problem of impact of the outer wall surface of the nozzle under the condition of high pressure of the sub-flow is solved, the impact and abrasion of the outer wall surface of the nozzle are protected, and the service life of the outer wall surface of the nozzle is prolonged; the hole type and hole inclination angle of the gas film hole on the inner wall surface of the converging section and the diverging section are designed, so that the problem of poor cooling efficiency of the traditional cylindrical gas film hole is solved, the cooling efficiency of the inner wall surface of the nozzle is improved, and the influence of the high temperature of the main flow on the inner wall surface of the nozzle is reduced; the flow guide structure is designed on the sub-flow sealing surface, so that the infrared radiation intensity of the nozzle wake flow is effectively inhibited, and the infrared stealth capability of the nozzle is improved.

Description

Technical Field

[0001] This invention belongs to the field of nozzle cooling design technology, and particularly relates to a binary converging-diverging nozzle with a composite gas film cooling structure. Background Technology

[0002] Current research on film cooling for nozzles, both domestically and internationally, primarily focuses on subsonic nozzles. For supersonic nozzles, the flow field during cooling is complex, and the cooling effect is influenced by multiple factors, resulting in relatively little research both domestically and internationally. However, as the performance requirements of fighter jets gradually increase, the mainstream velocity of nozzles in mainstream aero-engines is gradually shifting from subsonic to supersonic. The development of complex wave systems in the mainstream of supersonic nozzles leads to regional variations in mainstream pressure and velocity during contraction and expansion. Wall reflections of these complex wave systems cause adverse pressure gradients and flow separation phenomena in the nozzle mainstream. Furthermore, unlike subsonic film cooling, in supersonic nozzles using traditional cylindrical film cooling orifices, secondary inflows during supersonic flow cooling result in bow-shaped oblique shock waves in front of the orifices. Simultaneously, the velocity behind the orifices is slower, preventing rapid mixing with the mainstream, leading to lower cooling efficiency. Therefore, reducing nozzle wall temperature and improving cooling efficiency under these conditions has become a major research direction for supersonic nozzles.

[0003] Furthermore, in supersonic nozzle film cooling, the secondary flow, due to its high pressure and velocity, exerts a significant impact on the nozzle's outer wall during cooling. With increasing usage time, this secondary flow causes wear and damage to the secondary flow channels, particularly at the wall connections, impacting the nozzle's actual performance and reducing the lifespan of the outer wall. This significantly increases the construction and maintenance costs of the nozzle. Meanwhile, the high-temperature airflow at the nozzle tail greatly enhances the infrared radiation intensity of modern fighter jets, reducing their stealth capabilities. Currently, research on infrared radiation suppression at the nozzle tail is limited. Aside from low-emissivity coatings, there are no other effective infrared suppression methods, and low-emissivity coating technology alone is far from sufficient to meet the infrared stealth requirements of aircraft. Summary of the Invention

[0004] To address the aforementioned deficiencies in the prior art, this invention discloses a binary expansion / contraction nozzle with a composite gas film cooling structure, which is implemented using the following technical solution.

[0005] A binary convergent-divergent nozzle with a composite film cooling structure includes a main flow channel and two secondary flow channels distributed above and below the main flow channel. The wall surrounding the main flow channel includes two symmetrically distributed side plates and two symmetrically distributed convergent-divergent nozzle assemblies. Each convergent-divergent nozzle assembly includes an initial transition structure, a first inner wall surface of the convergent section, a second inner wall surface of the convergent section, a throat transition structure, and an inner wall surface of the diverging section. The initial transition structure, the first inner wall surface of the convergent section, the second inner wall surface of the convergent section, the throat transition structure, and the inner wall surface of the diverging section are sequentially connected and fixed to the inner walls of the two side plates. The secondary flow channels are composed of the convergent-divergent nozzle assemblies and the outer wall surface of the nozzle. The outer wall surface of the nozzle includes... The initial outer wall surface, transition outer wall surface, convergence section outer wall surface one, convergence section outer wall surface two, throat outer wall surface, expansion section outer wall surface, and secondary flow sealing surface are sequentially connected and fixed to the inner walls of the two side plates. The first drainage outlet is opened between the transition outer wall surface and the convergence section outer wall surface one, the second drainage outlet is opened between the convergence section outer wall surface two and the throat outer wall surface, and the third drainage outlet is opened between the expansion section outer wall surface and the secondary flow sealing surface. Each of the three drainage outlets has a drainage baffle structure for opening and closing the drainage outlet.

[0006] Both the inner wall surface of the converging section and the inner wall surface of the expanding section have a composite cooling structure. The composite cooling structure consists of an impact plate and an air film plate. A pressure stabilizing zone is formed between the impact plate and the air film plate. Impact holes are arranged on the impact plate and air film holes are arranged on the air film plate. Cooling holes are arranged on the inner wall surface of the converging section.

[0007] As a further improvement of the present invention, the first drainage outlet, the second drainage outlet, and the third drainage outlet are all slit-shaped outlets. The first drainage outlet is 7% of the outer surface area of ​​the outer wall of the transition section; the second drainage outlet is 3.3% of the outer surface area of ​​the outer wall of the convergence section; and the third drainage outlet is 10% of the outer surface area of ​​the secondary flow sealing surface.

[0008] As a further improvement of the present invention, the impact holes on the impact plate of the inner wall of the above-mentioned converging section are all oblique cylinders, and the opening direction is at a 60° angle to the wall surface; the air film holes on the air film plate of the inner wall of the above-mentioned converging section are oblique cuboids with a square cross-section, and the opening direction is at a 60° angle to the wall surface; the cooling holes on the inner wall of the above-mentioned converging section are oblique cuboids with a square cross-section, and the opening direction is at a 60° angle to the wall surface.

[0009] As a further improvement of the present invention, the impact holes on the inner wall impact plate of the expansion section are all oblique cylinders, and the opening direction is inclined at a 60° angle to the wall surface; the air film holes on the inner wall air film plate of the expansion section are conical, with an area ratio of 2:1 between the upper and lower end faces, and the straight line containing the center of the two end faces is inclined at a 57° angle to the wall surface.

[0010] As a further improvement of the present invention, the impact holes on the impact plate on the inner wall surface of the converging section and the impact plate on the expansion section, the air film holes on the air film plate on the inner wall surface of the converging section and the air film plate on the inner wall surface of the expansion section, and the cooling holes on the inner wall surface of the converging section are arranged in the same way.

[0011] As a further improvement of the present invention, the diameter of the impact hole on the impact plate on the inner wall of the converging section and the impact plate on the expansion section is d, the hypotenuse length of the air film hole on the air film plate on the inner wall of the converging section is d, the upper end face diameter of the air film hole on the air film plate on the inner wall of the expansion section is d, and the diameter of the cooling hole on the inner wall of the converging section is d; the hole with a diameter of d or a hypotenuse length of d is called an airflow hole.

[0012] The spacing between rows and columns of airflow holes is 20d. The distance between an air film hole and an impact hole on the inner wall of the expansion section or the inner wall of the convergence section along the normal direction of the inner wall is 10d. The impact holes and air film holes are arranged alternately. The distance from the start of the impact hole to both sides is 5d. The thickness of the air film plate, the impact plate, and the pressure stabilizing zone is d.

[0013] As a further improvement of the present invention, the above-mentioned secondary flow channel includes a starting zone secondary flow channel, a transition zone secondary flow channel, a convergence zone secondary flow channel, and an expansion zone secondary flow channel. The outer wall surface of the transition zone is an arc, and the ratio of its radius of curvature to the height of the secondary flow inlet is 0.85. The first and second outer wall surfaces of the convergence section are both straight plates, and the second outer wall surface of the convergence section is perpendicular to the first inner wall surface of the convergence section. The height of the convergence zone continuously increases along the flow direction, and the ratio of the inlet to outlet height of the secondary flow channel in the convergence zone is 1:1.1.

[0014] As a further improvement of the present invention, the outer wall surface of the expansion section is composed of a circular arc plate and a straight plate, and the ratio of the radius of curvature of the circular arc plate to the height of the secondary flow inlet is 0.93; the height of the secondary flow channel in the expansion region remains unchanged, and the ratio of the height of the secondary flow channel outlet in the convergence region is 1:5.

[0015] Compared to traditional nozzle cooling technologies, this invention addresses the issue of impact on the nozzle outer wall surface under high secondary flow pressure by designing a flow-guiding structure at different locations on the outer wall surface. This protects the nozzle outer wall surface from impact wear and extends its service life. Furthermore, by designing the orifice shape and inclination angle of the film cooling holes on the inner wall surfaces of the converging and expanding sections, this invention solves the problem of poor cooling efficiency of traditional cylindrical film cooling holes, improving the cooling efficiency of the nozzle inner wall surface and reducing the impact of high mainstream temperatures. Finally, by designing a flow-guiding structure on the secondary flow sealing surface, this invention effectively suppresses the infrared radiation intensity of the nozzle wake, improving the nozzle's infrared stealth capability. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the overall model structure of the vector nozzle.

[0017] Figure 2 This is a schematic diagram of the cross-sectional model of a vector nozzle.

[0018] Figure 3 This is a schematic diagram of the cross-section of a vector nozzle.

[0019] Figure 4 Schematic diagram of the composite cooling structure.

[0020] Figure 5 Schematic diagram of cooling hole layout.

[0021] Figure 6 This is a schematic diagram illustrating the effect of different hole inclination angles on the wall temperature.

[0022] Figure 7 This is a schematic diagram illustrating the effect of different ratios of the upper and lower areas of the frustum on the wall temperature.

[0023] Figure 8 These are schematic diagrams of the shapes of air film pores in two different locations.

[0024] The labels in the diagram are as follows: 1. Initial outer wall surface; 2. Transition outer wall surface; 3. Converging section outer wall surface one; 4. Diverging section outer wall surface; 5. Side plate; 6. Drainage baffle; 7. Secondary flow channel; 8. Initial transition structure; 9. Converging section inner wall surface one; 10. Converging section inner wall surface two; 11. Throat transition structure; 12. Diverging section inner wall surface; 13. Main flow channel; 14. Initial zone secondary flow channel; 15. Transition zone secondary flow channel; 16. Converging zone secondary flow channel; 17. Diverging zone secondary flow channel; 18. Converging section; 19. Transition section; 20. Diverging section; 21. Impact plate; 22. Impact hole; 23. Pressure stabilizing zone; 24. Film membrane plate; 25. Film membrane hole; 26. Converging section outer wall surface two; 27. Throat outer wall surface; 28. Secondary flow sealing surface. Detailed Implementation

[0025] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following embodiments and drawings are used to illustrate the present invention, but are not intended to limit the scope of protection of the present invention.

[0026] A binary converging-diverging nozzle with a composite film cooling structure, the nozzle structure is as follows: Figure 1-4As shown, the system includes a main flow channel 13 and two secondary flow channels 7 distributed above and below the main flow channel. The walls surrounding the main flow channel 7 include two symmetrically distributed side plates and two symmetrically distributed converging and expanding nozzle assemblies. The converging and expanding nozzle assemblies include an initial transition structure 8, a first converging section inner wall surface 9, a second converging section inner wall surface 10, a throat transition structure 11, and a diffusing section inner wall surface 12. The initial transition structure 8, the first converging section inner wall surface 9, the second converging section inner wall surface 10, the throat transition structure 11, and the diffusing section inner wall surface 12 are sequentially connected and fixed to the inner walls of the two side plates 5. The layered cooling structures on the first converging section inner wall surface 9 and the diffusing section inner wall surface 12 of the secondary flow channel cool the main flow. The secondary flow channel 7 is composed of a converging and expanding nozzle assembly and a nozzle outer wall surface. The nozzle outer wall surface includes an initial outer wall surface 1, a transition outer wall surface 2, a converging section outer wall surface 1 3, a converging section outer wall surface 2 26, a throat outer wall surface 27, an expanding section outer wall surface 4, and a secondary flow sealing surface 28. When the secondary flow passes through the transition outer wall surface 2, the impact of the secondary flow outer wall surface can be reduced because it is a smooth transition. At the end of the secondary flow channel 16 in the converging region, the pressure of the cooling fluid increases due to the reduction in its area, that is, the secondary flow velocity of the secondary flow channel (17) in the expanding region increases, thereby improving the mixing efficiency of the secondary flow in the expanding section with the mainstream, reducing the temperature of the mainstream wall surface, and improving the wall cooling efficiency of the expanding section.

[0027] The initial outer wall surface 1, transition outer wall surface 2, converging section outer wall surface 19, converging section outer wall surface 20, throat outer wall surface 11, expansion section outer wall surface 12, and secondary flow sealing surface 28 are sequentially connected and fixed to the inner walls of the two side plates 5. A first drainage outlet is opened between the transition outer wall surface 2 and the converging section outer wall surface 31, a second drainage outlet is opened between the converging section outer wall surface 26 and the throat outer wall surface 27, and a third drainage outlet is opened between the expansion section outer wall surface 4 and the secondary flow sealing surface 28. Each of the three drainage outlets has a drainage baffle 6 structure for opening and closing the drainage outlet. All drainage outlets are slit-shaped outlets. The first drainage outlet is 7% of the outer surface area of ​​the transition section outer wall surface; the second drainage outlet is 3.3% of the outer surface area of ​​the converging section outer wall surface 2; and the third drainage outlet is 10% of the outer surface area of ​​the secondary flow sealing surface. When the mainstream temperature of the expanding nozzle increases under different operating conditions, the secondary flow inlet pressure needs to increase, thus increasing the pressure on the outer wall of the nozzle. When the outer wall pressure reaches a certain value, all the guide baffles 6 open simultaneously, reducing the pressure near the corresponding outer wall surface. Since the size of the guide outlet corresponding to the guide baffle 6 is small, the pressure change caused by opening the guide baffle 6 has a small impact range. Calculations show that when the ratio of the guide structure size to the area of ​​the structure it occupies is less than 1:9.56, the impact of opening the guide structure on the mainstream wall temperature is less than 1.2%, indicating that the guide structure has a small impact on the wall at this time. At the same time, opening the guide structure at the end of the expanding section allows some cooling gas to be ejected from the nozzle tail. The fluid ejected from the secondary flow channel 7, because its temperature is lower than the mainstream temperature at the nozzle outlet, can wrap around the mainstream, thereby reducing the infrared radiation intensity at the mainstream outlet. Calculations show that after opening the guide structure at the end of the expanding section, the infrared radiation intensity at the position perpendicular to the nozzle axis decreases by 17.2% compared to before.

[0028] Studies show that the cooling effect of the composite cooling structure is higher than that of the traditional single-layer air film cooling. The inner wall surface 9 of the converging section and the inner wall surface 12 of the expanding section both have composite cooling structures. The composite cooling structure consists of an impact plate and an air film plate. A pressure stabilizing zone is formed between the impact plate and the air film plate. Impact holes 22 are arranged on the impact plate 21, and air film holes 25 are arranged on the air film plate 24. Cooling holes are arranged on the inner wall surface 10 of the converging section.

[0029] To achieve a stable cooling airflow in the pressure-stabilizing zone 23 of the composite cooling structure, the impact holes 22 on the impact plate 21 of the inner wall surface 9 of the converging section are all oblique cylinders, with the opening direction at a 60° angle to the wall surface. Since the mainstream temperature in the converging section 18 is relatively low, the requirements for composite cooling are also lower. Therefore, the air film holes 25 on the air film plate 24 of the inner wall surface 9 of the converging section are designed as oblique cuboids. This design ensures a reduction in the mainstream wall temperature while forming a thinner air film wall, thereby reducing the damage of secondary flow to the mainstream and minimizing thrust loss caused by secondary flow. The cuboid has a square cross-section, and different hole inclination angles correspond to different wall temperatures, such as... Figure 6As shown, the inclination angle of the film pore in the converging section At 60°C, the wall temperature The lowest performance and best cooling effect are achieved; therefore, the opening direction is chosen to be at a 60° angle to the wall surface. The cooling holes on the inner wall surface 10 of the aforementioned convergent section are oblique cuboids with square cross-sections, and the opening direction is at a 60° angle to the wall surface. Figure 8 As shown in the left figure.

[0030] Similarly, to achieve a stable cooling airflow in the pressure-stabilizing zone 23 of the composite cooling structure, the impact holes 22 on the impact plate 21 of the inner wall surface 12 of the expansion section are all oblique cylinders, with the opening direction at a 60° angle to the wall surface. The air film holes 25 on the air film plate 24 of the inner wall surface 12 of the expansion section are conical. When the cooling airflow passes through the air film holes 24, the hole area continuously decreases, increasing the cooling flow velocity and enhancing the mixing effect between the secondary and mainstream flows, thus improving the air film cooling efficiency. The wall temperature corresponding to different hole inclination angles and the ratio of the upper and lower end face areas of the cone is as follows: Figure 6 , 7 As shown, through calculation, the area ratio λ of the upper and lower bottom surfaces of the air film pore in the expansion section is 2:1, and the pore inclination angle is... At 55°C, the wall temperature It exhibits the lowest performance but the best cooling effect. Therefore, the area ratio of the upper and lower end faces of the air film vent 24 is set to 2:1, and the straight line containing the centers of the two end faces forms a 55° angle with the wall surface. Figure 8 As shown in the figure on the right.

[0031] The impact holes 22 on the impact plate 21 on the inner wall surface 9 of the converging section and the impact plate 21 on the inner wall surface 12 of the expanding section, the air film plate 24 on the inner wall surface 9 of the converging section and the air film plate 24 on the inner wall surface 12 of the expanding section, and the cooling holes on the inner wall surface 10 of the converging section have the same hole arrangement.

[0032] The diameter of the impact hole 22 on the impact plate 21 on the inner wall surface 9 of the converging section and the inner wall surface 12 of the expanding section is d. The hypotenuse length of the air film hole 25 on the air film plate 24 on the inner wall surface 9 of the converging section is d. The upper end face diameter of the air film hole 25 on the air film plate 24 on the inner wall surface 12 of the expanding section is d. The diameter of the cooling hole on the inner wall surface 10 of the converging section is d. The holes with a diameter of d or a hypotenuse length of d are called airflow holes.

[0033] like Figure 5 As shown, in order to increase the number of airflow holes while ensuring that adjacent airflow holes do not interfere with each other, the row spacing and column spacing of the airflow holes are both set to 20d. The distance between the air film holes 25 and the impact holes 22 along the normal direction of the inner wall surface 12 of the expansion section or the inner wall surface 9 of the convergence section is 10d. The impact holes 22 and the air film holes 25 are arranged alternately. The distance from the start of the impact hole 22 to both sides is 5d. The thickness of the air film plate 24, the impact plate 21, and the pressure stabilizing zone 23 is all d.

[0034] Secondary flow channel 7 includes initial secondary flow channel 14, transition secondary flow channel 15, convergence secondary flow channel 16, and expansion secondary flow channel 17. The influence of the geometric parameters of each wall surface on the cooling efficiency of the main flow wall surface is numerically calculated, and the optimal geometric parameters of each outer wall surface are finally given. The profile curve of the transition outer wall surface 2 is an arc, and the ratio of its radius of curvature to the height of the secondary flow inlet is 0.85. The outer wall surface 3 of the convergence section and the outer wall surface 4 of the convergence section are both straight plates, and the outer wall surface 26 of the convergence section is perpendicular to the inner wall surface 9 of the convergence section. The height of the convergence zone increases continuously along the flow direction, and the ratio of the inlet to outlet height of the secondary flow channel 16 in the convergence zone is 1:1.1.

[0035] The outer wall of the expansion section consists of a circular arc plate and a straight plate. The ratio of the radius of curvature of the circular arc plate to the height of the secondary flow inlet is 0.93. The height of the secondary flow channel in the expansion zone remains unchanged, and the ratio of the height of the secondary flow channel outlet in the convergence zone is 1:5. Calculations show that the secondary flow pressure is relatively stable at this time.

[0036] Compared to traditional converging and expanding nozzles, this invention addresses the issue of impact on the nozzle's outer wall surface under high secondary flow pressure by designing a unique outer wall structure and incorporating flow-guiding structures at different locations. This protects the nozzle's outer wall surface from impact wear and extends its service life. Furthermore, by designing the orifice shape and inclination angle of the film cooling holes on the inner walls of the converging and expanding sections, this invention solves the problem of poor cooling efficiency of traditional cylindrical film cooling holes, improving the cooling efficiency of the nozzle's inner wall surface and reducing the impact of high mainstream temperatures. Finally, by designing flow-guiding structures on the secondary flow sealing surface, this invention effectively suppresses the infrared radiation intensity of the nozzle wake, enhancing the nozzle's infrared stealth capability.

Claims

1. A binary expansion / contraction nozzle with a composite film cooling structure, characterized in that: It includes a main flow channel and two secondary flow channels distributed above and below the main flow channel. The walls surrounding the main flow channel include two symmetrically distributed side plates and two symmetrically distributed converging-diverging nozzle assemblies. The converging-diverging nozzle assembly includes an initial transition structure, a first converging section inner wall surface, a second converging section inner wall surface, a throat transition structure, and a dilating section inner wall surface. The initial transition structure, the first converging section inner wall surface, the second converging section inner wall surface, the throat transition structure, and the dilating section inner wall surface are sequentially connected and fixed to the inner walls of the two side plates. The secondary flow channels are composed of the converging-diverging nozzle assemblies and the nozzle outer wall surface; the nozzle outer wall surface includes an initial outer wall surface and a transition outer wall surface. The outer wall surfaces of the following sections are connected and fixed in sequence to the inner walls of the two side plates: the first outer wall surface of the converging section, the second outer wall surface of the converging section, the outer wall surface of the throat, the outer wall surface of the expansion section, and the secondary flow sealing surface. The first drainage outlet is opened between the outer wall surface of the transition section and the first outer wall surface of the converging section, the second drainage outlet is opened between the outer wall surface of the converging section and the outer wall surface of the throat, and the third drainage outlet is opened between the outer wall surface of the expansion section and the secondary flow sealing surface. Each of the three drainage outlets has a drainage baffle structure for opening and closing the drainage outlet. Both the inner wall surface of the converging section and the inner wall surface of the expanding section have a composite cooling structure. The composite cooling structure consists of an impact plate and an air film plate. A pressure stabilizing zone is formed between the impact plate and the air film plate. Impact holes are arranged on the impact plate and air film holes are arranged on the air film plate. Cooling holes are arranged on the inner wall surface of the converging section.

2. The binary expansion / contraction nozzle with a composite gas film cooling structure according to claim 1, characterized in that: The first, second, and third drainage outlets mentioned above are all slit-shaped outlets. The first drainage outlet is 7% of the outer surface area of ​​the outer wall of the transition section; the second drainage outlet is 3.3% of the outer surface area of ​​the outer wall of the convergence section; and the third drainage outlet is 10% of the outer surface area of ​​the secondary flow sealing surface.

3. The binary expansion / contraction nozzle with a composite film cooling structure according to claim 1, characterized in that: The impact holes on the impact plate on the inner wall of the aforementioned convergence section are all oblique cylinders, with the opening direction at a 60° angle to the wall surface; the air film holes on the air film plate on the inner wall of the aforementioned convergence section are oblique cuboids with a square cross-section, and the opening direction at a 60° angle to the wall surface; the cooling holes on the inner wall of the aforementioned convergence section are oblique cuboids with a square cross-section, and the opening direction at a 60° angle to the wall surface.

4. The binary expansion / contraction nozzle with a composite film cooling structure according to claim 1, characterized in that: The impact holes on the inner wall impact plate of the expansion section are all oblique cylinders, and the opening direction is inclined at a 60° angle to the wall surface; the air film holes on the inner wall air film plate of the expansion section are conical, with an area ratio of 2:1 between the upper and lower end faces, and the straight line containing the center of the two end faces is inclined at a 57° angle to the wall surface.

5. A binary expansion / contraction nozzle with a composite gas film cooling structure according to claim 3 or 4, characterized in that: The impact holes on the impact plate on the inner wall surface of the converging section and the impact plate on the expansion section, the air film holes on the air film plate on the inner wall surface of the converging section and the air film plate on the inner wall surface of the expansion section, and the cooling holes on the inner wall surface of the converging section are arranged in the same way.

6. The binary expansion / contraction nozzle with a composite gas film cooling structure according to claim 5, characterized in that: The diameter of the impact holes on the impact plate on the inner wall of the converging section and the impact plate on the expansion section is d. The hypotenuse length of the air film hole on the air film plate on the inner wall of the converging section is d. The diameter of the upper end face of the air film hole on the air film plate on the inner wall of the expansion section is d. The diameter of the cooling hole on the second inner wall of the converging section is d. The holes with a diameter of d or a hypotenuse length of d are called airflow holes. The spacing between rows and columns of airflow holes is 20d. The distance between an air film hole and an impact hole on the inner wall of the expansion section or the inner wall of the convergence section along the normal direction of the inner wall is 10d. The impact holes and air film holes are arranged alternately. The distance from the start of the impact hole to both sides is 5d. The thickness of the air film plate, the impact plate, and the pressure stabilizing zone is d.

7. The binary expansion / contraction nozzle with a composite film cooling structure according to claim 1, characterized in that: The aforementioned secondary flow channels include the initial secondary flow channel, the transition secondary flow channel, the convergence secondary flow channel, and the expansion secondary flow channel. The outer wall profile of the transition zone is an arc, and the ratio of its radius of curvature to the height of the secondary flow inlet is 0.

85. Both the first and second outer wall surfaces of the convergence section are straight plates, and the second outer wall surface of the convergence section is perpendicular to the first inner wall surface of the convergence section. The height of the convergence zone continuously increases along the flow direction, and the ratio of the inlet to outlet height of the secondary flow channel in the convergence zone is 1:1.

1.

8. The binary expansion / contraction nozzle with a composite film cooling structure according to claim 1, characterized in that: The outer wall surface of the expansion section is composed of a circular arc plate and a straight plate. The ratio of the radius of curvature of the circular arc plate to the height of the secondary flow inlet is 0.

93. The height of the secondary flow channel in the expansion region remains unchanged, and the ratio of the height of the secondary flow channel outlet in the convergence region is 1:5.

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