Spiral S-shaped spray pipe structure and application

Abstract

The invention discloses a spiral S-shaped spray pipe structure and application, and belongs to the field of aero-engines. The device sequentially comprises a coaxial circular pipeline, a first S-shaped spiral section, a second S-shaped spiral section and an equal-straight section in the axial direction, all the sections are connected through a continuous S-shaped center line in a penetrating mode, and the center line of the coaxial circular pipeline is parallel to the center line of the equal-straight section. The on-way sections of the first S-shaped spiral section and the second S-shaped spiral section rotate around the tangential direction of the section center of the S-shaped center line according to a linear increasing function, the initial rotation angle is 1-2 degrees, and the final section rotation angle is 18-48 degrees; the cross section areas of the first S-shaped spiral section and the second S-shaped spiral section are gradually reduced along the S-shaped center line, the cross section width is gradually expanded, and the cross section height is gradually reduced. By optimizing the characteristics of the high-temperature core flow of the spray pipe, the purpose of reducing the infrared radiation characteristics of the high-temperature core flow is achieved.

Description

Technical Field

[0001] The present invention belongs to the field of aero-engines, and particularly relates to a spiral S-bend nozzle structure and its application. Background Art

[0002] The exhaust system of an aero-engine is the main infrared radiation source of an aircraft. Effectively reducing the infrared radiation characteristics of the exhaust system is of great significance for improving the stealth performance of the aircraft. The S-bend stealth nozzle is an exhaust nozzle with large curvature, multiple bends, and special-shaped characteristics. It can not only effectively block high-temperature components such as turbine blades and lobe mixers inside the engine, but also shorten the length of the high-temperature core area of the exhaust flow by intensifying the mixing of the high-temperature jet with the surrounding atmosphere, thereby significantly reducing the infrared radiation signal of the exhaust system. The S-bend nozzle has become one of the key technologies focused on in the research of aero-engines due to its low infrared characteristics brought by its special structure.

[0003] The most fundamental problem of the S-bend nozzle lies in its structural design, including the design of its geometric model, the addition of auxiliary structural design, etc. So far, researchers at home and abroad have designed S-bend nozzles in various configurations according to performance requirements, and mainly designed the S-bend nozzle with the aerodynamic performance, infrared radiation characteristics, and structural deformation characteristics as indicators. Among them, the S-bend nozzle structure mainly takes the infrared stealth performance / aerodynamic performance as the optimization goal. The general design method of the S-bend nozzle is highly constrained by spatial layout, load, etc. to meet the infrared stealth characteristics; and to ensure the rationality of the nozzle layout in the whole machine, modifying its geometric structure may result in the loss of infrared performance / aerodynamic performance; at the same time, most S-bend nozzle design schemes focus on optimizing the nozzle shielding rate or active temperature control to optimize the infrared radiation characteristics.

[0004] Therefore, the present invention designs an S-bend nozzle scheme to passively optimize the characteristics of the high-temperature core flow of the nozzle to reduce infrared radiation under the condition of less damage to the aerodynamic performance. Summary of the Invention

[0005] Technical Problems to be Solved

[0006] To avoid the deficiencies of the prior art, the present invention provides a spiral S-bend nozzle structure and its application. Under the condition of minimizing the impact on the aerodynamic performance of the nozzle, through the passive swirl mixing mechanism of the spiral flow channel and the low-complexity geometric design, the collaborative optimization of aerodynamic efficiency and infrared stealth is achieved within a limited space, breaking through the triangular contradiction of "length-diameter ratio - stealth performance - aerodynamic loss" of the traditional S-bend nozzle; by optimizing the characteristics of the high-temperature core flow in the nozzle, the purpose of reducing the infrared radiation characteristics of the high-temperature core flow is realized. Due to the characteristics of the spiral channel itself, the airflow passes through a longer path inside the nozzle and is affected by the configuration to generate a low degree of rotation, enhancing the friction between the airflow and the pipe wall and the mixing with the outside atmosphere, and intensifying the heat exchange of the high-temperature airflow, thereby effectively shortening the length of the high-temperature core flow.

[0007] The technical solution of the present invention is: a spiral S-bend nozzle structure, which sequentially includes a coaxial circular pipe, a first S-shaped spiral section, a second S-shaped spiral section and a straight section along the axial direction, and the center lines of each section are connected by a continuous S-shaped center line, wherein the center lines of the coaxial circular pipe and the straight section are parallel;

[0008] The cross-sections of the first S-shaped spiral section and the second S-shaped spiral section rotate in the tangential direction of the cross-section center around the S-shaped center line according to a linear increasing function, the initial rotation angle is 1° to 2°, and the final cross-section rotation angle is 18° to 48°;

[0009] The cross-sectional areas of the first S-shaped spiral section and the second S-shaped spiral section gradually contract along the S-shaped center line, the cross-sectional width gradually expands, and the cross-sectional height gradually decreases;

[0010] The total length-diameter ratio of the nozzle is optimized to be 1.8 to 2.4, the offset ratio is compressed to 0.3 to 0.5, and the width-height ratio of the outlet cross-section is limited to 4 to 6.

[0011] A further technical solution of the present invention is: the linear increasing function of the rotation angle satisfies:

[0012] θ i = θ1*i, i = 1, 2,... n;

[0013] θ1 = [1°, 2°];

[0014] θ n = [18°, 48°]

[0015] In the formula, i represents the serial number of the cross-section along the path, and n represents the total number of cross-sections along the path;

[0016] The rotation direction of the rotation angle is clockwise or counterclockwise, and the wide sides of all cross-sections are strictly orthogonal to the Z-axis.

[0017] A further technical solution of the present invention is that the cross-sections along the path are distributed at equal curvature intervals on the S-shaped center line, and the total number of cross-sections along the path is 18 to 24.

[0018] A further technical solution of the present invention is that the ratio of the length of the first S-shaped spiral section in the X-axis direction to the nozzle inlet diameter is 0.9.

[0019] A further technical solution of the present invention is that the ratio of the lengths of the first S-shaped spiral section and the second S-shaped spiral section in the X-axis direction is 0.6 to 1.0; the length of the straight section in the X-direction accounts for one-ninth to one-seventh of the total length of the first S-shaped spiral section, the second S-shaped spiral section, and the straight section in the X-axis direction.

[0020] A further technical solution of the present invention is that the radial cross-sectional shape of the nozzle transitions from a circular shape at the inlet end to a rounded rectangular shape at the outlet end, and the wide sides of all cross-sections along the path are parallel to the Z-axis direction, and the curvature of the flow channel wall is continuous.

[0021] A further technical solution of the present invention is that the total pressure recovery coefficients of the nozzle at pressure ratios NPR = 3, 5, and 7 reach 0.9833, 0.9840, and 0.9841 respectively.

[0022] A further technical solution of the present invention is that the shielding efficiency of the curved configuration at the rear section of the flow channel for the front high-temperature turbine blades is improved, the exposed area is less than 10% of the nozzle inlet area, and the shielding range expands non-linearly in the Y-Z plane.

[0023] An aeroengine includes the spiral S-bend nozzle structure, which is installed at the engine tail nozzle for reducing the infrared radiation characteristics and adapting to the compact space layout of the aircraft.

[0024] Beneficial effects

[0025] The beneficial effects of the present invention are as follows: Through the collaborative design of "spiral flow channel + low aspect ratio", the present invention solves the balance problem among the aerodynamic performance, stealth ability, and engineering applicability of traditional S-bend nozzles, and provides an efficient and reliable technical solution for the power system of the next-generation stealth aircraft.

[0026] 1. By restricting the offset ratio and aspect ratio of the overall S-bend nozzle, the present invention has a relatively small nozzle self-weight, effectively reducing the overall machine load in actual engineering applications. Through the segmented cross-section rotation design (maximum rotation angle of 48°) and the flow channel bending configuration, the shielding range for the front high-temperature components of the engine is expanded, and the exposed area is reduced, significantly reducing the intensity of the forward and backward infrared detection signals. Among them, the reduction of the flow channel cross-sectional area and the control of the aspect ratio (4 to 6) reduce the risk of air flow separation, and the total pressure recovery coefficients reach 0.9833, 0.9840, and 0.9841 at pressure ratios NPR = 3, 5, and 7 respectively.

[0027] 2. The spiral S-shaped flow channel of the present invention increases the wetted perimeter area of the contact between the air flow and the nozzle. During the process of the air flow passing through the S-shaped spiral channel, while having effective friction with the wall surface, it will not cause excessive loss of aerodynamic performance, enhances the heat exchange between the high-temperature air flow and the wall surface, and reduces the air flow temperature.

[0028] 3. The spiral flow channel of the present invention induces the air flow to generate a low-degree rotation, significantly accelerates the mixing of the high-temperature jet flow and the outside cold air, thereby accelerating the cooling of the jet flow. The length of the high-temperature core area of the jet flow is shorter than that of the traditional S-shaped nozzle, effectively weakening the infrared radiation signal of the high-temperature air flow to enhance the stealth performance.

[0029] 4. The spiral S-shaped nozzle structure applying the technical solution of the present invention takes into account both aerodynamic performance and infrared stealth performance. By effectively reducing the length of the high-temperature core of the jet flow, the infrared radiation signal is reduced, and the engineering application value of the S-shaped nozzle is improved. Description of the Drawings

[0030] Figure 1 is an overall structural schematic diagram of a spiral S-shaped nozzle structure that can be selected according to an embodiment of the present invention;

[0031] Figure 2 is a schematic diagram of the Y-direction view of a spiral S-shaped nozzle structure that can be selected according to an embodiment of the present invention;

[0032] Figure 3 is a schematic diagram of the Z-direction view of a spiral S-shaped nozzle structure that can be selected according to an embodiment of the present invention;

[0033] Figure 4 is a rear view of a spiral S-shaped nozzle structure that can be selected according to an embodiment of the present invention;

[0034] Figure 5 is the temperature distribution nephogram of the symmetry plane of a common S-shaped nozzle with a low length-diameter ratio and a low offset ratio under different pressure drop ratios;

[0035] Figure 6 is the temperature distribution nephogram of the symmetry plane of a spiral S-shaped nozzle that can be selected according to an embodiment of the present invention under different pressure drop ratios.

[0036] Description of the reference numerals: 1. Circular pipe; 2. First S-shaped spiral section; 3. Second S-shaped spiral section; 4. Straight section; 5. S-shaped center line; 6. Connection section between the first half and the second half of the first S-shaped spiral section; 7. Connection section between the first S-shaped spiral section and the second S-shaped spiral section; 8. Connection section between the first half and the second half of the second S-shaped spiral section; 9. Outlet section of the second S-shaped spiral section. Detailed Embodiment

[0037] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, and should not be construed as limiting the present invention.

[0038] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. are based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as limiting the present invention.

[0039] The currently disclosed CN106014686A designs "a spiral S-bend nozzle structure for a turbofan engine". This nozzle achieves complete shielding of the high-temperature components of the engine, effectively improving the infrared stealth performance of the S-bend nozzle. However, in order to achieve complete shielding of the high-temperature components, the aspect ratio and offset ratio of this nozzle structure are relatively large, the aerodynamic layout is difficult, and its own length is relatively long and the self-weight is relatively large, which will bring higher installation difficulty and greater load to the overall machine application. CN117145648A discloses "a small-offset S-bend nozzle with a cooling strut". This design arranges a cooling strut in front of the outlet of the S-bend nozzle with a small offset ratio and sets a number of cooling holes to reduce the infrared radiation characteristics through strut shielding and cooling air. However, due to the small offset of the nozzle, when observed on the infrared radiation detection surface in the direct rear direction, the exposed area of the high-temperature components inside the engine is relatively large, and the combined effect of multiple cooling air inlets will also cause damage to the aerodynamic performance.

[0040] Aiming at the core contradiction that it is difficult to balance the aerodynamic efficiency and infrared stealth performance of the existing S-bend nozzle under the constraints of low aspect ratio and low offset ratio, and problems such as the sharp increase in manufacturing cost and the decrease in reliability caused by the traditional scheme relying on high-complexity geometric designs (such as multi-dimensional deflection, active cooling), the present invention proposes a spiral S-bend nozzle structure. This structure synergistically optimizes the swirl induction effect of the spiral flow channel and geometric parameters, and significantly reduces the infrared radiation characteristics of the high-temperature core flow on the premise of minimizing aerodynamic losses (total pressure recovery coefficient > 0.983). The specific technical solution is as follows:

[0041] The present invention relates to a spiral S-bend nozzle structure, which sequentially includes a circular pipe, a first S-shaped spiral section, a second S-shaped spiral section, and a straight section along the axial direction; the circular pipe, the first S-shaped spiral section, the second S-shaped spiral section, and the straight section share an S-shaped center line; the S-shaped nozzle structure sequentially includes four key cross-sections along the center line direction, namely, the connection cross-section of the first half and the second half of the first S-shaped spiral section, the connection cross-section of the first S-shaped spiral section and the second S-shaped spiral section, the connection cross-section of the first half and the second half of the second S-shaped spiral section, and the outlet cross-section of the second S-shaped spiral section; the inlet end of the first S-shaped spiral section is connected to the outlet end of the circular pipe, and its outlet end is connected to the inlet end of the second S-shaped spiral section. The connection cross-section of the first half and the second half of the first S-shaped spiral section is obtained by rotating a small angle clockwise or counterclockwise around the tangent line at the center point of this cross-section with a fillet rectangle control surface whose width line perpendicular to the center line is parallel to the Z-axis direction, and the rotation angle range is 1-2°; the second half of the first S-shaped spiral section and the cross-sections along the way of the second S-shaped spiral section are all rotated 1-2° clockwise or counterclockwise around the tangent line at the center point of each reference surface, that is, the cross-section along the way perpendicular to the center line, and the magnitude of the rotation angle increases linearly and uniformly from front to back, with a total of 18-24 cross-sections along the way, until the rotation angle of the outlet cross-section of the second S-shaped spiral section is the largest, which is 18-48°; the inlet end to the outlet end of the straight section is coaxial and has the same cross-section, and its outlet is the outlet of the entire nozzle, corresponding to the jet outlet of the aircraft; the cross-sectional areas of the first S-shaped spiral section and the second S-shaped spiral section gradually shrink along the direction of the S-shaped center line; the cross-sectional widths of the first S-shaped spiral section and the second S-shaped spiral section gradually increase along the direction of the S-shaped center line; the cross-sectional heights of the first S-shaped spiral section and the second S-shaped spiral section gradually decrease along the direction of the S-shaped center line; the parts of the S-shaped center line corresponding to the circular pipe and the straight section are parallel to the X-axis direction.

[0042] Specifically, the ratio of the length of the first S-shaped spiral section in the X-axis direction to the inlet diameter of the nozzle is 0.9; the ratio of the total length of the first S-shaped spiral section, the second S-shaped spiral section, and the straight section in the X-axis direction to the inlet diameter of the nozzle ranges from 1.8 to 2.4.

[0043] Specifically, the ratio of the length of the first S-shaped spiral section to the length of the second S-shaped spiral section in the X-axis direction is 0.6-1.0; the length of the straight section in the X-axis direction accounts for one-ninth to one-seventh of the total length of the first S-shaped spiral section, the second S-shaped spiral section, and the straight section in the X-axis direction.

[0044] Specifically, the width-to-height ratio of the outlet cross-section of the second S-shaped spiral section and the straight section is 4-6.

[0045] Specifically, starting from the connection between the first half and the second half of the first S-shaped spiral section until the outlet of the second S-shaped spiral section, 18 to 24 reference cross-sections along the path are uniformly arranged perpendicular to the S-shaped center line, ensuring that the wide sides of all reference cross-sections along the path are parallel to the Z-axis direction; the cross-section along the path of the connection between the first half and the second half of the first S-shaped spiral section is the first cross-section where rotation starts, denoted as i = 1, and the rotation angle is denoted as θ i , it rotates clockwise or counterclockwise by θ1 = 1 to 2° around the tangent line at the center point of this cross-section along the S-shaped center line. Similarly, all subsequent cross-sections along the path are rotated in the same direction in the same way, and the rotation angle θ i increases linearly and uniformly, and the variation rule is: θ i = θ1 * i;

[0046] The actual cross-sections along the path of the first S-shaped spiral section and the second S-shaped spiral section are obtained. The rotation angle of the outlet cross-section of the second S-shaped spiral section is the largest, θ i = 18° to 48°.

[0047] Specifically, the flow path of the spiral S-bend nozzle structure is curved. Looking forward from the rear of the nozzle to the internal channel of the nozzle, as a whole, the shielding range for the high-temperature components at the front end of the nozzle is relatively large, the exposed area of the high-temperature components is relatively small, and the infrared radiation characteristics are weakened.

[0048] The above technical solutions are further analyzed in conjunction with the accompanying drawings as follows:

[0049] In one embodiment, as shown in Figures 1 to 4 , the spiral S-bend nozzle structure includes: a circular pipe 1; a first S-shaped spiral section 2; a second S-shaped spiral section 3; a straight section 4; an S-shaped center line 5; a cross-section 6 connecting the first half and the second half of the first S-shaped spiral section; a cross-section 7 connecting the first S-shaped spiral section and the second S-shaped spiral section; a cross-section 8 connecting the first half and the second half of the second S-shaped spiral section; an outlet cross-section 9 of the second S-shaped spiral section.

[0050] Applying the spiral S-bend nozzle structure of the embodiment of the present invention takes into account both aerodynamic performance and infrared stealth performance, effectively adapts to the complex space constraint conditions of the aircraft, and at the same time takes into account reducing the load of the aircraft, improving the engineering application value of the S-bend nozzle.

[0051] In this embodiment, the spiral S-bend nozzle structure is composed of a circular pipe 1, a first S-shaped spiral section 2, a second S-shaped spiral section 3, and a straight section 4, as shown in Figure 1 . The first S-shaped spiral section 2 is connected to the circular pipe 1. The outlet end of the first S-shaped spiral section 2 is connected to the inlet end of the second S-shaped spiral section 3 through the cross-section 7 connecting the first S-shaped spiral section and the second S-shaped spiral section. The outlet end of the second S-shaped spiral section 3 is connected to the inlet end of the straight section 4 through the outlet cross-section 9 of the second S-shaped spiral section. The cross-section of the straight section is a rounded rectangle. The nozzle outlet is the aircraft jet outlet.

[0052] Specifically, according to the aircraft fuselage space constraint conditions in actual engineering applications, the central coordinates of the outlet end position of the circular duct are (0, 0, 0) (unit: m), and the central coordinates of the jet outlet position of the aircraft are (2.25, 0.15, 0). Through numerical calculation and analysis of the S-shaped centerline 5, the central coordinates of the connection section 6 of the first half and the second half of the first S-shaped spiral section are obtained as (0.54, -0.205, 0), the central coordinates of the connection section 7 between the first S-shaped spiral section and the second S-shaped spiral section are (0.9, -0.25, 0), the central coordinates of the connection section 8 of the first half and the second half of the second S-shaped spiral section are (1.25, -0.087, 0), and the central coordinates of the outlet section 9 of the second S-shaped spiral section are (1.95, 0.15, 0). The diameter of the inlet end of the nozzle is 1 m, and the ratio of the total length of the first S-shaped spiral section 2, the second S-shaped spiral section 3, and the straight section 4 in the X-axis direction to the diameter of the inlet end of the nozzle is 2.25. The ratio of the lengths of the first S-shaped spiral section 2 and the second S-shaped spiral section 3 in the X-axis direction is 2:3, and the length of the straight section 4 in the X-axis direction accounts for 0.133 of the total length of the first S-shaped spiral section, the second S-shaped spiral section, and the straight section in the X-axis direction. The offset ratio of the first S-bend section of the nozzle is 0.516, and the offset ratio of the second S-bend section is 0.3.

[0053] Furthermore, the cross-sectional areas of the first S-shaped spiral section 2 and the second S-shaped spiral section 3 gradually shrink along the direction of the S-shaped centerline 5. The cross-sectional widths of the first S-shaped spiral section 2 and the second S-shaped spiral section 3 gradually increase along the direction of the S-shaped centerline. The cross-sectional heights of the first S-shaped spiral section 2 and the second S-shaped spiral section 3 gradually decrease along the direction of the S-shaped centerline. The parts of the S-shaped centerline corresponding to the circular duct 1 and the straight section 4 are parallel to the X-axis direction. The outlet area of the nozzle is 0.454 m 2 , the width is 1.6512 m, the height is 0.2752 m, and the width-to-height ratio is 6.

[0054] Furthermore, starting from the connection section 6 of the first half and the second half of the first S-shaped spiral section, until the outlet section 9 of the second S-shaped spiral section, 19 cross-sectional areas perpendicular to the S-shaped centerline 5 and evenly spaced in the X-axis direction are established, with the wide sides parallel to the Z-axis direction. The connection cross-sectional area 6 of the first half and the second half of the first S-shaped spiral section is the first cross-sectional area to start rotating, denoted as i = 1, and the rotation angle is denoted as θ i , rotating counterclockwise by θ1 = 1.5° around the tangent line of the S-shaped centerline 5 at the center point of this cross-sectional area. Similarly, all subsequent cross-sectional areas are rotated in the same direction in the same way, and the rotation angle θ i increases linearly and uniformly, and the variation law is: θ i = θ1 * i. The actual cross-sectional areas of the first S-shaped spiral section and the second S-shaped spiral section are obtained. The rotation angle of the outlet cross-sectional area of the second S-shaped spiral section is the largest, θ 19= 28.5°.

[0055] The torsional flow channel characteristics of the first S-shaped spiral section 2 and the second S-shaped spiral section 3 can achieve more effective shielding of the high-temperature components of the engine, reducing the detectable area of the high-temperature components of the non-full-shielding S-bend nozzle structure with a small length-diameter ratio and a small offset ratio.

[0056] While improving the infrared stealth performance of the non-full-shielding S-bend nozzle structure with a small length-diameter ratio and a small offset ratio, the spiral S-bend nozzle structure takes into account the aerodynamic performance. The spiral flow channel inside has a very small negative impact on the aerodynamic performance. The difference in the total pressure recovery coefficient between the spiral S-bend nozzle structure and the general form of the S-bend nozzle structure is small under the conditions of pressure ratio NPR = 3, 5, and 7, as shown in Table 1.

[0057] Table 1 Total pressure recovery coefficients of the spiral S-bend nozzle structure and the general form of the S-bend nozzle structure at different pressure ratios

[0058] NPR Spiral S-bend nozzle structure General S-bend nozzle structure 3 0.9833 0.9876 5 0.9840 0.9882 7 0.9841 0.9883

[0059] Due to its spiral channel, the airflow passing through the spiral S-bend nozzle structure will generate a low degree of rotation. After the airflow is ejected, the mixing speed with the outside atmosphere is accelerated, and the jet temperature cools faster. Therefore, the length of the high-temperature core area of the jet is shorter than that of the general form of the S-bend nozzle structure, as Figure 5 、 Figure 6 shown. The shortening of the length of the high-temperature core area of the jet further enhances the infrared stealth performance.

[0060] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention without departing from the principles and purposes of the present invention.

Claims

1. A spiral S-bend nozzle structure, characterized in that: It successively includes a coaxial circular pipe, a first S-shaped spiral section, a second S-shaped spiral section and a straight section along the axial direction. Each section is connected by a continuous S-shaped center line. The center lines of the coaxial circular pipe and the straight section are parallel. The cross-sections along the way of the first S-shaped spiral section and the second S-shaped spiral section rotate in the tangential direction of the cross-section center around the S-shaped center line according to a linear increasing function. The initial rotation angle is 1° - 2°, and the final cross-section rotation angle is 18° - 48°. The cross-sectional areas of the first S-shaped spiral section and the second S-shaped spiral section gradually shrink along the S-shaped center line, the cross-sectional width gradually expands, and the cross-sectional height gradually decreases. The total length-diameter ratio of the nozzle is optimized to be 1.8 - 2.4, the offset ratio is compressed to 0.3 - 0.5, and the width-height ratio of the outlet cross-section is limited to 4 - 6.

2. The spiral S-bend nozzle structure according to claim 1, characterized in that: The linear increasing function of the rotation angle satisfies: θ i = θ1 * i, where i = 1, 2,..., n; θ1 = [1°, 2°]; θ n = [18°, 48°]; In the formula, i represents the serial number of the cross-section along the way, and n represents the total number of cross-sections along the way. The rotation direction of the rotation angle is clockwise or counterclockwise, and the wide sides of all cross-sections are strictly orthogonal to the Z-axis.

3. The spiral S-bend nozzle structure according to claim 1, characterized in that: The cross-sections along the way are distributed on the S-shaped center line at equal curvature intervals, and the total number of cross-sections along the way is 18 - 24.

4. The spiral S-bend nozzle structure according to claim 1, characterized in that: The ratio of the length of the first S-shaped spiral section in the X-axis direction to the inlet diameter of the nozzle is 0.

9.

5. The spiral S-bend nozzle structure according to claim 1, characterized in that: The ratio of the lengths of the first S-shaped spiral section and the second S-shaped spiral section in the X-axis direction is 0.6 - 1.0; the length of the straight section in the X direction accounts for one-ninth to one-seventh of the total length of the first S-shaped spiral section, the second S-shaped spiral section and the straight section in the X-axis direction.

6. The spiral S-bend nozzle structure according to claim 1, characterized in that: The radial cross-sectional shape of the nozzle transitions from circular at the inlet end to a rounded rectangle at the outlet end, and the wide sides of all cross-sections along the way are parallel to the Z-axis direction, and the curvature of the flow channel wall is continuous.

7. The spiral S-bend nozzle structure according to claim 1, characterized in that: The total pressure recovery coefficients of the nozzle at the pressure drop ratios NPR = 3, 5, 7 reach 0.9833, 0.9840, 0.9841 respectively.

8. The spiral S-bend nozzle structure according to claim 1, characterized in that: The shielding efficiency of the curved configuration at the rear section of the flow channel for the front high-temperature turbine blade is improved. The exposed area is less than 10% of the inlet area of the nozzle, and the shielding range expands non-linearly in the Y-Z plane.

9. An aeroengine, characterized in that, It includes the spiral S-bend nozzle structure according to any one of claims 1 - 8, which is installed at the engine tail nozzle for reducing the infrared radiation characteristics and adapting to the compact space layout of the aircraft.

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