A single-side expansion double S-bend nozzle with a rear deck

Abstract

The present invention provides a single-sided expansion double S-bend nozzle with a rear deck, which belongs to the field of aviation engines; it comprises a first nozzle section and an S-shaped convergent section installed in sequence at the engine outlet, the inlet of the first nozzle section being the inlet of the internal combustion engine gas and the external air; the outlet of the S-shaped convergent section is sequentially installed with a single-sided expansion section and a rear deck section; the lower wall surface and the two side walls of the single-sided expansion section are both straight sections, and the upper wall surface is an expansion surface, thereby forming a nozzle expansion section of a single-sided expansion form; the rear deck section is connected to the lower wall surface of the single-sided expansion section and is located in the same plane. The present invention designs the expansion section of the S-bend convergent nozzle to be a single-sided expansion form, and the upper wall surface of the expansion section is generated by the characteristic line method. The airflow at the outlet of the nozzle expansion section generated by the characteristic line method has good uniformity. The lower wall surface of the expansion section is a straight section, which ensures the coupling of the nozzle expansion section and the rear deck, and can achieve better nozzle-fuselage integration design requirements.

Description

Technical Field

[0001] The invention belongs to the field of aviation engines, and in particular relates to a single-side expansion double S-bend nozzle with a rear deck. Background Art

[0002] The S-bend nozzle has attracted widespread attention from research institutions at home and abroad due to its excellent infrared and radar stealth performance. On the one hand, the S-bend nozzle's upward and downward curved geometric configuration can completely block high-temperature components inside the engine, such as the center cone and turbine, reducing the intensity of their solid infrared radiation. On the other hand, the S-bend nozzle's outlet shape is mostly rectangular, elliptical, or trapezoidal. Relevant research shows that compared to traditional circular nozzle outlets, special-shaped nozzle outlets can further enhance the mixing between the nozzle's high-temperature gas and the external atmosphere, thereby reducing the infrared radiation intensity of the gas in its tail jet. In addition, on some stealth aircraft, an area of the fuselage called the rear deck is placed downstream of the nozzle outlet to achieve better nozzle-fuselage integration and line-of-sight blocking of the high-temperature gas. The presence of the rear deck will further reduce the intensity of infrared radiation below the nozzle.

[0003] At present, domestic researchers have made a preliminary design for the S-bend convergent-divergent nozzle and have proposed an S-bend convergent-divergent nozzle that completely blocks the high-temperature turbine outlet end face, solving the problem that fighter jets using convergent engine tail nozzles cannot meet the requirements of fighter jets covering sub-, trans- and supersonic flight. Its shortcoming is that its axially symmetrical expansion section profile cannot be well coupled with the rear deck, resulting in poor uniformity of the nozzle outlet airflow.

[0004] When the S-bend convergent-divergent nozzle is applied to actual stealth fighters, the traditional axially symmetrical S-bend nozzle expansion section cannot meet the requirements of integrated design with the fighter. Therefore, a new type of S-bend nozzle is needed that can perfectly couple with the rear deck and enable the fighter to fly at supersonic speed. Summary of the Invention

[0005] Technical issues to be solved:

[0006] In order to avoid the shortcomings of the existing technology, the present invention provides a single-sided expansion double S-bend nozzle with a rear deck. The introduction of the expansion section of the single-sided expansion S-bend nozzle solves the problem of coupling between the expansion section of the traditional S-bend convergent-divergent nozzle and the rear deck while ensuring the uniformity of the airflow at the nozzle outlet, and at the same time can reduce the infrared radiation intensity below the nozzle.

[0007] The technical solution of the present invention is: a single-side expansion double S-bend nozzle with a rear deck, comprising a first nozzle section and an S-shaped convergent section sequentially installed at the engine outlet, wherein the inlet of the first nozzle section is the inlet for the internal combustion engine gas and the external combustion engine air; the outlet of the S-shaped convergent section is sequentially installed with a single-side expansion section and a rear deck section;

[0008] The lower wall and both side walls of the unilateral expansion section are both straight sections, and the upper wall is an expansion surface, thereby forming a nozzle expansion section of a unilateral expansion form; the rear deck section is connected to the lower wall of the unilateral expansion section and is located in the same plane.

[0009] A further technical solution of the present invention is that: the first nozzle section is a straight section, and the ratio of its axial length to the inlet diameter of the S-shaped convergent section is 0.6.

[0010] A further technical solution of the present invention is: the first nozzle section includes an engine outer duct, an engine mixer, an engine inner duct, and an engine center cone, and the ratio of the axial length of the engine mixer to the inlet diameter of the S-shaped convergent section is between 0.2 and 0.6.

[0011] A further technical solution of the present invention is that the engine mixer is a ring mixer, a lobe mixer or a funnel-shaped mixer, and the airflow from the inner and outer ducts is mixed by the mixer and then flows into the inlet of the S-shaped convergent section.

[0012] A further technical solution of the present invention is: a nozzle throat is formed at the connection between the outlet of the S-shaped convergent section and the inlet of the unilateral expansion section. When the nozzle is in the design working state, the airflow reaches the speed of sound at the nozzle throat, and then expands to the supersonic speed in the unilateral expansion section, and the airflow continues to expand in the rear deck section.

[0013] A further technical solution of the present invention is: the upper wall surface of the unilateral expansion section is generated using a characteristic line method, by assigning the airflow parameters of the nozzle throat to the initial expansion line, solving the characteristic line equation and the compatibility equation to obtain the initial expansion zone profile, and then determining the turning section profile according to the principle of flow continuity based on the design state nozzle outlet Mach number or nozzle length constraint, and then stretching the obtained overall profile along the third direction to obtain the upper wall surface of the unilateral expansion section.

[0014] A further technical solution of the present invention is that the ratio of the length of the unilateral expansion section to the height of the nozzle throat is between 2 and 5.

[0015] A further technical solution of the present invention is that the shape of the rear deck section is rectangular, triangular, zigzag or arc-shaped.

[0016] A further technical solution of the present invention is that the ratio of the axial length of the rear deck section to the height of the outlet of the unilateral expansion section is between 2 and 8.

[0017] Beneficial effects

[0018] The beneficial effects of the present invention are as follows: the expansion section of the S-bend convergent-divergent nozzle is designed to be unilaterally expanded, and the upper wall of the expansion section is generated using the characteristic line method. The nozzle expansion section outlet airflow generated by the characteristic line method has good uniformity. The lower wall of the expansion section is a straight section, which ensures the coupling between the nozzle expansion section and the rear deck, and can achieve better nozzle-fuselage integration design requirements. When the nozzle inlet conditions are the same, the thrust coefficients of the traditional double S-bend convergent-divergent nozzle and the unilaterally expanding double S-bend nozzle with a rear deck are 0.9786 and 0.9698, respectively, and the total pressure recovery coefficients are 0.9421 and 0.9293, respectively, ensuring the performance of the nozzle. At the same time, the shielding effect of the rear deck can effectively reduce the intensity of infrared radiation below the nozzle.

[0019] refer to Figure 4 Figure 2 shows the infrared radiation intensity simulation results of a conventional double-S-bend convergent-divergent nozzle and a single-sided expansion double-S-bend nozzle with a rear deck under identical inlet conditions, using the inverse Monte Carlo method in the 3-5 μm band within the elevation detection plane. Dimensionless processing was used to facilitate analysis. The results show that over a wide range of detection angles from -90° to -10° within the elevation detection plane, the infrared radiation intensity of the single-sided expansion double-S-bend nozzle with a rear deck is lower than that of the conventional double-S-bend convergent-divergent nozzle, improving its infrared stealth performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The figure is a schematic diagram of a single-side expansion double S-bend nozzle structure with a rear deck, which is optional according to an embodiment of the present invention.

[0021] Figure 2 It is a cross-sectional view of the middle symmetric surface of a single-sided expansion double S-bend nozzle with a rear deck, which is optional according to an embodiment of the present invention.

[0022] Figure 3 This is a schematic structural diagram of the internal components of a single-sided expansion double S-bend nozzle with a rear deck, which is optional according to an embodiment of the present invention, including an inner culvert, an outer culvert, a central cone, and a mixer.

[0023] Figure 4 This is an angular distribution diagram of infrared radiation intensity within the pitch detection surface of a single-sided expansion double S-bend nozzle with a rear deck, which is optional according to an embodiment of the present invention.

[0024] Explanation of the accompanying symbols: 1. First nozzle section, 2. S-shaped convergent section, 3. Nozzle throat, 4. Single-sided expansion section, 41. Upper wall of the single-sided expansion section, 42. Side wall of the single-sided expansion section, 43. Lower wall of the single-sided expansion section, 5. Rear deck section, 6. Engine duct, 61. Ducted air inlet, 7. Engine mixer, 8. Engine duct, 81. Ducted gas inlet, 9. Engine center cone. DETAILED DESCRIPTION

[0025] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to explain the present invention, but should not be construed as limiting the present invention.

[0026] 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 to 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 device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as limiting the present invention.

[0027] Reference Figures 1 to 3 As shown, the present invention discloses a single-sided expansion double S-bend nozzle with a rear deck, comprising a first barrel 1, an S-shaped convergent section 2, a single-sided expansion section 4, a rear deck section 5, an engine duct 6, an engine mixer 7, an engine duct 8, and an engine center cone 9. The inlet of the S-shaped convergent section 2 is an engine duct 81 and an engine duct 61. The nozzle throat 3 is formed at the connection between the outlet of the S-shaped convergent section 2 and the inlet of the single-sided expansion section 4. The lower wall 43 and the side wall 42 of the single-sided expansion section are equal straight sections. The upper wall 41 of the single-sided expansion section is designed using the characteristic line method to ensure the uniformity of the outlet airflow. The rear deck section 5 is an equal straight section and is connected to the lower wall 43 of the single-sided expansion section.

[0028] The rear deck section 5 is in a rectangular, triangular, sawtooth or arc shape.

[0029] The engine mixer 7 is a ring mixer, a lobe mixer or a funnel-shaped mixer. The airflow from the engine inner duct 8 and the engine outer duct 6 is mixed through the engine mixer 7 and then flows to the inlet of the S-shaped convergent section 2.

[0030] The upper wall surface 41 of the unilateral expansion section is generated using a characteristic line method. By determining parameters such as the total temperature, total pressure, velocity, upstream and downstream curvatures, nozzle outlet back pressure, and design nozzle outlet Mach number at the nozzle throat 3, the profile of the upper wall surface 41 of the unilateral expansion section can be obtained using the characteristic line method.

[0031] In order to avoid the matching problem between the engine and the fighter caused by an overly long expansion section and the uneven airflow at the nozzle outlet caused by an overly short expansion section, the ratio of the length of the unilateral expansion section 4 to the height of the nozzle throat 3 is between 2 and 5.

[0032] In order to avoid the problem of increased engine weight caused by the length of the rear deck being too long and the problem of increased infrared radiation intensity caused by the length of the rear deck being too short, the ratio of the axial length of the rear deck section 5 to the outlet height of the unilateral expansion section 4 should be between 2 and 8.

[0033] Example:

[0034] In this embodiment, the first nozzle section is a straight section, the ratio of its axial length to the inlet diameter of the S-shaped convergent section is 0.6, the ratio of the length of the unilateral expansion section 4 to the height of the nozzle throat 3 is 3, the width of the unilateral expansion section 4 is the same as the outlet of the S-shaped convergent section 2, the rear deck 5 is rectangular, the ratio of its axial length to the outlet height of the unilateral expansion section 4 is 2, and the width is the same as the width of the unilateral expansion section, the engine mixer 7 is an annular mixer, the ratio of its axial length to the inlet diameter of the S-shaped convergent section 2 is 0.5, and the ratio of the axial length of the central cone 9 to the inlet diameter of the S-shaped convergent section 2 is 0.5.

[0035] Reference Attachment Figure 2 The gas in the engine inner duct 8 and the air in the engine outer duct 6 are mixed through the engine mixer 7 and flow to the inlet of the S-shaped convergent section 1. The airflow then expands and accelerates in the S-shaped convergent section 2. When it reaches the nozzle throat 3, the airflow accelerates to the speed of sound. Subsequently, the airflow continues to expand and accelerate to supersonic speed in the unilateral expansion section 4. After reaching the nozzle outlet, the airflow continues to expand and accelerate on the rear deck 5.

[0036] When the nozzle inlet conditions are the same, the thrust coefficients of the conventional double-S-bend convergent-divergent nozzle and the single-side expansion double-S-bend nozzle with a rear deck are 0.9786 and 0.9698, respectively, and the total pressure recovery coefficients are 0.9421 and 0.9293, respectively, ensuring nozzle performance. Furthermore, the shielding effect of the rear deck effectively reduces the intensity of infrared radiation below the nozzle.

[0037] Reference Attachment Figure 4 The results are obtained by using the inverse Monte Carlo method to simulate the infrared radiation intensity of a conventional double-S-bend convergent-divergent nozzle and a single-sided expansion double-S-bend nozzle with a rear deck under identical inlet conditions in the 3-5μm band within the pitch detection plane. For ease of analysis, the results were dimensionless. The results show that over a wide range of detection angles from -90° to -10° in the pitch detection plane, the infrared radiation intensity of the single-sided expansion double-S-bend nozzle with a rear deck is lower than that of the conventional double-S-bend convergent-divergent nozzle, improving its infrared stealth performance.

[0038] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative 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 purpose of the present invention.

Claims

1. A single-side expansion double S-bend nozzle with a rear deck, comprising a first nozzle section and an S-shaped convergent section sequentially mounted at an engine outlet, wherein the inlet of the first nozzle section serves as an inlet for internal combustion engine fuel gas and external combustion engine air; characterized in that: The outlet of the S-shaped convergent section is sequentially equipped with a unilateral expansion section and a rear deck section; The lower wall and both side walls of the unilateral expansion section are straight sections, and the upper wall is an expansion surface, thereby forming a nozzle expansion section of unilateral expansion type; the rear deck section is connected to the lower wall of the unilateral expansion section and is located in the same plane; The upper wall surface of the unilateral expansion section is generated using a characteristic line method. The initial expansion line is assigned to the airflow parameters of the nozzle throat, and the characteristic line equation and the compatibility equation are solved to obtain the initial expansion zone profile. Then, the turning section profile is determined according to the principle of flow continuity based on the nozzle exit Mach number or nozzle length constraint in the design state. The obtained overall profile is then stretched along the third direction to obtain the upper wall surface of the unilateral expansion section. The ratio of the length of the unilateral expansion section to the height of the nozzle throat is between 2 and 5; The ratio of the axial length of the rear deck section to the height of the outlet of the unilateral expansion section is between 2 and 8.

2. The single-side expansion double S-bend nozzle with a rear deck according to claim 1, characterized in that: The first nozzle section is a straight section, and the ratio of its axial length to the inlet diameter of the S-shaped convergent section is 0.

6.

3. The single-side expansion double S-bend nozzle with a rear deck according to claim 1, characterized in that: The first nozzle section includes an engine outer duct, an engine mixer, an engine inner duct, and an engine center cone. The ratio of the axial length of the engine mixer to the inlet diameter of the S-shaped convergent section is between 0.2 and 0.

6.

4. The single-side expansion double S-bend nozzle with a rear deck according to claim 3, characterized in that: The engine mixer is a ring mixer, a lobe mixer or a funnel-shaped mixer. The airflows from the inner and outer ducts are mixed by the mixer and then flow into the inlet of the S-shaped convergent section.

5. The single-side expansion double S-bend nozzle with a rear deck according to claim 1, characterized in that: The nozzle throat is formed at the connection between the outlet of the S-shaped convergent section and the inlet of the unilateral expansion section. When the nozzle is in the design working state, the airflow reaches the speed of sound at the nozzle throat, and then expands to the supersonic speed in the unilateral expansion section. The airflow continues to expand in the rear deck section.

6. The single-side expansion double S-bend nozzle with a rear deck according to claim 1, characterized in that: The shape of the rear deck section is rectangular, triangular, sawtooth or arc.

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