S-shaped binary convergent-divergent nozzle with low infrared characteristic

Abstract

The invention relates to the technical field of engine exhaust system design and infrared suppression, and discloses a low-infrared-characteristic S-shaped binary convergent-divergent spray pipe which comprises an S-shaped binary convergent spray pipe, an S-shaped binary divergent spray pipe and a straight section which are connected in sequence. Wherein the S-shaped two-dimensional convergent nozzle is a circular torque convergent bent pipeline, circular torque transition profiles are all in a rounded rectangle mode, the S-shaped two-dimensional divergent nozzle is a rectangular divergent bent pipeline, and the straight section is a section of rectangular pipeline with the same area. On the premise that the aerodynamic performance of the spray pipe is guaranteed, the spray pipe has the low infrared radiation characteristic, the length is greatly shortened, and installation and arrangement of the spray pipe on an aircraft are facilitated.

Description

Technical Field

[0001] The present invention relates to the technical fields of engine exhaust system design and infrared suppression technology, and more specifically, to a low-infrared-signature S-shaped dual convergent-divergent nozzle. Background Art

[0002] As the main infrared radiation contributor of an aircraft, the exhaust system of an engine is usually equipped with an axisymmetric convergent-divergent nozzle. A large number of high-temperature components are exposed, with obvious infrared radiation characteristics. In the key angle of infrared detection (the small-angle domain in the directly aft direction), the high-temperature solid wall and high-temperature gas of its exhaust system contribute approximately 90% and 10% of the total infrared radiation, respectively. Traditional S-shaped convergent-divergent nozzles can suppress the infrared radiation of the engine, but they are all composed of a convergent S-shaped nozzle and a convergent-divergent rectangular nozzle, with a relatively long overall length, making it difficult to install in the rear body of an aircraft.

[0003] For example, the invention patent with the publication number CN103993982A discloses a dual-S-bend infrared stealth nozzle structure that can achieve multi-directional thrust vector control. The nozzle designed in this invention consists of components such as a dual-S-bend convergent nozzle, a rectangular convergent-divergent nozzle, and a secondary flow injection pipeline, and uses secondary flow to achieve the vector thrust state. However, this type of nozzle has a complex composition, incurring a great cost in terms of weight and size, and its excessive length also makes it difficult to install in the rear body of an aircraft.

[0004] Another example is the invention patent with the publication number CN113107705A, which discloses a dual-S-bend convergent-divergent nozzle with infrared suppression measures. The dual-S-bend convergent-divergent nozzle designed in this invention consists of an S-shaped convergent nozzle and a rectangular divergent nozzle, and includes active infrared suppression measures such as cooling channels. However, the combination of the S-shaped convergent nozzle and the rectangular divergent nozzle further lengthens the overall length of the nozzle. It is difficult to install due to the limited space in the rear body of the aircraft, and additional connection measures such as flange rings need to be added, increasing the overall weight. Summary of the Invention

[0005] In order to solve the problems and deficiencies existing in the prior art, the present invention proposes an S-shaped dual convergent-divergent nozzle composed of an S-shaped dual convergent nozzle and an S-shaped dual divergent nozzle, which has low infrared radiation characteristics while ensuring its aerodynamic performance, and its length is greatly shortened, facilitating installation and layout on an aircraft.

[0006] To achieve the above-mentioned invention objectives, the technical solution of the present invention is as follows:

[0007] On the one hand, the present invention discloses a low-infrared-signature S-shaped dual convergent-divergent nozzle, as Figure 1As shown in the figure, it includes a converging section, a diverging section, and a straight section connected in sequence; the converging section includes an S-shaped two-dimensional converging nozzle, the inlet of the S-shaped two-dimensional converging nozzle is connected to the turbine outlet section of the engine, the cross-section where the inlet is located corresponds to the inlet section A7 of the nozzle, and the inlet section A7 is circular; the diverging section includes an S-shaped two-dimensional diverging nozzle, the inlet of the S-shaped two-dimensional diverging nozzle is connected to the outlet of the S-shaped two-dimensional converging nozzle, and the connection between the two corresponds to the throat section A8 of the nozzle, and A8 is a rounded rectangle; the straight section is a rectangular pipe with a constant cross-sectional area, the inlet of the rectangular pipe is connected to the outlet of the S-shaped two-dimensional diverging nozzle, and the cross-section where the outlet of the rectangular pipe is located corresponds to the outlet section A9 of the nozzle; wherein, further, the S-shaped two-dimensional converging nozzle is an S-bend circular torque converging pipe, which is gradually converging from the pipe inlet to the outlet, and the circular torque transition profile of the converging nozzle is in the form of a rounded rectangle, that is, each characteristic cross-section is a rounded rectangle; the S-shaped two-dimensional diverging nozzle is an S-bend rectangular diverging pipe, which is gradually diverging from the pipe inlet to the outlet, and each characteristic cross-section of the S-shaped two-dimensional diverging nozzle is a rounded rectangle. The circular torque process of the entire nozzle of the present invention is completed in the S-shaped two-dimensional converging nozzle to reduce the profile change of the S-shaped two-dimensional diverging nozzle, thereby improving the aerodynamic performance of the entire nozzle.

[0008] For the converging-diverging nozzle composed of the S-shaped two-dimensional converging nozzle, the S-shaped two-dimensional diverging nozzle, and the rectangular pipe, after the air flow enters the nozzle, it passes through the first downward-bending S-bend channel (i.e., the S-shaped two-dimensional converging nozzle), the air flow deviates axially downward and deflects, and after passing through the throat, it enters the second upward-bending S-bend channel (i.e., the S-shaped two-dimensional diverging nozzle), the air flow returns to the axial direction, and finally is ejected through the straight rectangular pipe.

[0009] Preferably, each characteristic cross-section of the S-shaped two-dimensional converging nozzle, the S-shaped two-dimensional diverging nozzle, and the rectangular pipe is perpendicular to the center line of the nozzle, and the center line of the nozzle is as shown by the red line in Figure 1 and the characteristic cross-section is as shown by the dashed line in Figure 1 .

[0010] Preferably, in order to ensure the aerodynamic performance, the center line of the S-shaped two-dimensional converging nozzle changes continuously and monotonically, and the corresponding function expression is:

[0011]

[0012] wherein, (x7,y7) is the starting coordinate of the center line of the converging section, is a function of the relative position , and should satisfy the following constraints:

[0013] Preferably, the center line of the S-shaped two-dimensional diverging nozzle changes continuously and monotonically, and the corresponding function expression is:

[0014]

[0015] Among them, (x8, y8) is the starting coordinate of the center line of the expansion section, is a function of the relative position and should satisfy the following constraints: φ(0) = 0, φ(1) = 1, φ'(0) = 0, φ'(1) = 0.

[0016] Preferably, as Figure 1 shown, the cross-section A7 is the inlet cross-section of the S-shaped dual-convergent nozzle, the cross-sectional shape is circular, L c is the length of the S-shaped dual-convergent nozzle, H8 is the height of the throat cross-section, W8 is the width of the throat cross-section, and S8 is the center line offset of the S-shaped dual-convergent nozzle; assuming the diameter of the inlet cross-section A7 is D, then there are:

[0017] L c = 0.8 - 1.2D;

[0018] S8 = 0.5 - 0.8D;

[0019] H8 = 0.2 - 0.4D;

[0020] W8 = 0.6 - 1.2D;

[0021] For the length of the S-shaped dual-convergent nozzle, it is usually adjusted and designed according to the actual length, generally not greater than D.

[0022] Preferably, as Figure 1 shown, within the expansion section, L D is the length of the S-shaped dual-expansion nozzle, S9 is the center line offset of the S-shaped dual-expansion nozzle, then there are:

[0023] L D = 0.4D - 0.7D;

[0024] S9 = 0 - 0.1D.

[0025] For the center line offset S9 of the S-shaped dual-expansion nozzle, it is usually adjusted in coordination with the center line offset S8 of the S-shaped dual-convergent nozzle to complete the shielding of the high-temperature components of the engine.

[0026] Preferably, as Figure 1 shown, in order to make the jet flow direction tend to the engine axis direction and avoid thrust loss, a straight section is designed; within the straight section, L p is the length of the rectangular pipe, W9 is the width of the outlet cross-section, H9 is the height of the outlet cross-section, then there are:

[0027] L p = 0 - 0.2D;

[0028] W9 = 0.8 to 1.3D;

[0029] H9 = 0.2 to 0.5D.

[0030] Advantages of the present invention:

[0031] 1. In the S-shaped dual contraction-expansion nozzle of the present invention, the expansion section often has a greater impact on the aerodynamic performance. Therefore, the circular torque process of the S-shaped dual contraction-expansion nozzle designed in the present invention is completed in the convergent section, and the characteristic sections of the expansion section are all rounded rectangles to reduce the profile change of the expansion section, thereby improving the aerodynamic performance of the entire nozzle.

[0032] 2. The present invention uses a segmented method to design the convergent section and the expansion section respectively, and uses two single S-shaped centerlines that are connected end to end and have the same slope at the connection to control the bending of the nozzle. It is easy to distinguish the convergent section from the expansion section, and it is easy to control the profile parameters of the throat, forming two independently variable aspect ratios at the throat and the outlet section, thereby controlling the aerodynamic performance and infrared stealth performance of the nozzle.

[0033] 3. While ensuring the aerodynamic performance, the overall length of the present invention is shorter than that of the traditional S-shaped contraction-expansion nozzle. The total length is only about 2 times the inlet diameter of the nozzle. The processing can adopt an integral casting method, saving weight and space, which is beneficial for installation and arrangement on the rear body of the aircraft. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The foregoing and following specific descriptions of the present invention become clearer when read in conjunction with the following drawings, in which:

[0035] Figure 1 is a side view of the dual contraction-expansion nozzle of the present invention;

[0036] Figure 2 is an isometric view of the dual contraction-expansion nozzle of the present invention.

[0037] In the drawings:

[0038] 1. S-shaped dual convergent nozzle; 2. Length of the S-shaped dual expansion nozzle; 3. Rectangular duct. DETAILED DESCRIPTION OF THE INVENTION

[0039] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions for achieving the purpose of the present invention will be further described below through specific embodiments. It should be noted that the technical solutions claimed by the present invention include but are not limited to the following embodiments. Based on the embodiments in the present invention, all other embodiments obtained by those skilled in the art without making creative efforts shall fall within the protection scope of the present invention.

[0040] Embodiments of the present invention propose a low-infrared-signature S-shaped two-dimensional convergent-divergent nozzle. The nozzle includes a convergent section, a divergent section, and a straight section. The convergent section is an S-shaped two-dimensional convergent nozzle, which has a gradually convergent structure from the inlet to the outlet of the duct. The divergent section is an S-shaped two-dimensional divergent nozzle, which has a gradually divergent structure from the inlet to the outlet of the duct. The straight section is a rectangular duct with a constant cross-sectional area. The S-shaped two-dimensional convergent nozzle, the S-shaped two-dimensional divergent nozzle, and the rectangular duct are connected in sequence. The inlet of the S-shaped two-dimensional convergent nozzle is connected to the turbine outlet section of the engine. The cross-section corresponding to the inlet is the inlet section A7 of the nozzle, and the inlet section A7 is circular. The inlet of the S-shaped two-dimensional divergent nozzle is connected to the outlet of the S-shaped two-dimensional convergent nozzle, and the connection between the two corresponds to the throat section A8 of the nozzle, and A8 is a rounded rectangle. The inlet of the rectangular duct of the straight section is connected to the outlet of the S-shaped two-dimensional divergent nozzle, and the cross-section corresponding to the outlet of the rectangular duct is the outlet section A9 of the nozzle.

[0041] Further, the S-shaped two-dimensional convergent nozzle is an S-bend circular torque convergent duct, and the circular torque transition profile of the convergent nozzle is in the form of a rounded rectangle, that is, each characteristic cross-section is a rounded rectangle.

[0042] Further, the S-shaped two-dimensional divergent nozzle is an S-bend rectangular divergent duct, and each characteristic cross-section of the S-shaped two-dimensional divergent nozzle is a rounded rectangle.

[0043] Further, the characteristic parameters of the S-shaped two-dimensional convergent nozzle 1 are as Figure 1 shown. The A7 section is the inlet section, its shape is circular, the A8 section is the throat section, its shape is a rounded rectangle, D is the diameter of the A7 section, L C is the length of the S-shaped two-dimensional convergent nozzle 1, H8 is the height of the throat section, W8 is the width of the throat section, and S8 is the offset of the centerline of the S-shaped two-dimensional convergent nozzle 1. In the embodiment described in the present invention, L C = 0.9D, W8 = 0.8D, H8 = 0.2D, S8 = 0.6D.

[0044] Further, to ensure the aerodynamic performance, the centerline of the S-shaped two-dimensional convergent nozzle 1 changes continuously and monotonically, and its Figure 1 function expression in (x7, y7) is the starting coordinate of the centerline of the convergent section, is a function of the relative position and should satisfy the following constraints: In the embodiment described in the present invention,

[0045] Further, the characteristic parameters of the S-shaped two-dimensional divergent nozzle 2 are as Figure 1 shown, LD is the length of the S-shaped dual-expansion nozzle 2, and S9 is the offset of the centerline of the S-shaped dual-expansion nozzle 2. In the embodiment depicted in the present invention, L D = 0.6D, S9 = 0.03D.

[0046] Furthermore, the centerline of the S-shaped dual-expansion nozzle 2 changes continuously and monotonically, and its Figure 1 function expression in (x8, y8) is the starting coordinate of the centerline of the expansion section, is a function of the relative position , and is subject to the same constraints as the converging section, i.e., φ(0) = 0, φ(1) = 1, φ'(0) = 0, φ'(1) = 0. In the embodiment depicted in the present invention,

[0047] Furthermore, the straight section is a rectangular channel with a constant cross-sectional area, and its characteristic parameters are as Figure 1 shown. The A9 section is the outlet section, and its shape is rectangular. L P is the length of the straight section, H9 is the height of the outlet section, and W9 is the width of the outlet section. In the embodiment depicted in the present invention, L P = 0.1D, W9 = 1.2D, H9 = 0.3D.

[0048] The above are only the preferred embodiments of the present invention and do not impose any form of limitation on the present invention. Any simple modification or equivalent change made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A low-infrared-signature S-shaped variable-area nozzle, characterized in that, It includes a converging section, a diverging section, and a straight section connected in sequence; wherein, the converging section includes an S-shaped dual-flow converging nozzle (1), and the diverging section includes an S-shaped dual-flow diverging nozzle (2); wherein, the S-shaped dual-flow converging nozzle (1) is a circular torque converging and bending duct, and the circular torque transition surfaces are all in the form of rounded rectangles, the S-shaped dual-flow diverging nozzle (2) is a rectangular diverging and bending duct, and the straight section is a rectangular duct (3) with a constant cross-sectional area.

2. The S-shaped dual-mode variable-area nozzle with low infrared signature according to claim 1, wherein Each characteristic cross-section of the S-shaped dual-flow converging nozzle (1), the S-shaped dual-flow diverging nozzle (2), and the rectangular duct (3) is perpendicular to the centerline of the nozzle.

3. The S-shaped dual-mode variable-area nozzle with low infrared signature according to claim 1, wherein The centerline of the S-shaped dual-flow converging nozzle (1) changes continuously and monotonically, and the function expression is: where (x7, y7) is the starting coordinate of the center line of the converging section, is the relative position of the function, and should satisfy the following constraints:

4. The S-shaped dual-mode inlet and outlet nozzle with low infrared signature according to claim 1, characterized in that, The centerline of the S-shaped dual-flow diverging nozzle (2) changes continuously and monotonically, and the function expression is: Among them, (x8, y8) is the starting coordinate of the center line of the expansion section, is a function of the relative position and should satisfy the following constraints: φ(0) = 0, φ(1) = 1, φ'(0) = 0, φ'(1) = 0.

5. The S-shaped binary convergent-divergent nozzle with low infrared signature according to claim 1, wherein, Within the convergent section, the length L of the S-shaped two-dimensional convergent nozzle (1) c = 0.8 - 1.2D, the centerline offset S8 of the S-shaped two-dimensional convergent nozzle is 0.5 - 0.8D, the throat section height H8 is 0.2 - 0.4D, and the throat section width W8 is 0.6 - 1.2D; where D is the inlet section diameter of the S-shaped two-dimensional convergent nozzle.

6. The S-shaped binary convergent-divergent nozzle with low infrared signature according to claim 1, wherein Within the divergent section, the length L of the S-shaped two-dimensional divergent nozzle (2) D is 0.4D to 0.7D, and the centerline offset S9 of the S-shaped two-dimensional divergent nozzle is 0 to 0.1D; where D is the inlet cross-sectional diameter of the S-shaped two-dimensional convergent nozzle.

7. The S-shaped dual-mode variable area nozzle with low infrared signature according to claim 1, characterized in that, In the straight section, the length L of the rectangular duct (3) p = 0 to 0.2D, the width W9 of the outlet cross-section = 0.8 to 1.3D, and the height H9 of the outlet cross-section = 0.2 to 0.5D; where D is the diameter of the inlet cross-section of the S-shaped dual-convergent nozzle.

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