Short-distance take-off and landing type thrust vectoring nozzle based on airfoil-shaped guide plate and design method thereof

Abstract

The invention discloses a short-distance take-off and landing type thrust vectoring nozzle based on a wing-shaped flow guide plate and a design method of the short-distance take-off and landing type thrust vectoring nozzle. The nozzle comprises a nozzle inlet, an equal straight section, a convergent section, a throat, an expansion section and a nozzle outlet which are sequentially communicated, and the wing-shaped flow guide plate and a rotating shaft are arranged at the nozzle outlet; the wing-shaped flow guide plate can rotate around the rotating shaft from the horizontal position in the clockwise or anticlockwise direction by the maximum geometric deflection angle gamma, and wall surface interference does not occur in the rotating process. Only one specially designed wing-shaped flow guide plate is arranged near an outlet of a conventional convergent-divergent nozzle, the convergent-divergent nozzle has the dual functions of level flight vector adjustment and short-distance take-off and landing on the premise that the thrust performance change of the nozzle is small, the level flight vector adjustment and the short-distance take-off and landing can be achieved only through rotation of one flow guide plate, the adjustment method is simple and reliable, and the adjustment cost is low. The controllable thrust vector angle range is large, the linearity is good, and a thrust vectoring nozzle design scheme is provided for development of high-performance and short-distance take-off and landing aircrafts in the future.

Description

Technical Field

[0001] The present invention relates to the field of aviation propulsion systems, and in particular focuses on thrust vector control technology for short take-off and landing aircraft, and more particularly to a mechanical guide vane type vector nozzle with both level flight vector and short take-off and landing functions and a design method thereof. Background Art

[0002] In the field of aviation, especially for short-distance / vertical take-off and landing (Vertical / Short Take-off and Landing, V / STOL) aircraft, in addition to the vector thrust control required for conventional flight, an additional lift generation mechanism is also required during the take-off and landing phase to reduce runway dependence. For example, the Harrier fighter uses a rotating nozzle to achieve vertical take-off. However, existing V / STOL design schemes are usually accompanied by complex structures, high maintenance costs, and problems that affect the overall performance of the aircraft. In addition, most of the current mechanical vector nozzles and lift systems operate independently, lacking a highly integrated design scheme, and cannot take into account both efficient short-distance take-off and landing and excellent flight performance. In addition, the gas rudder vector nozzle, which has a working principle similar to the vector nozzle of the present invention, has a small thrust vector angle adjustment range and does not have a short-distance take-off and landing function.

[0003] In summary, the existing vector nozzle technology and V / STOL scheme have many shortcomings and cannot fully meet the requirements of modern aviation industry for performance optimization and cost-effectiveness. Therefore, it is necessary to develop a short take-off and landing vector nozzle based on wing-shaped guide vanes, which not only has a wide range of level flight vector adjustment capabilities, but also has efficient and reliable short take-off and landing capabilities, and can also reduce drag loss, simplify mechanical structure and reduce weight, thereby improving the overall performance of the entire flight system. Summary of the invention

[0004] In order to overcome the deficiencies in the prior art, the present invention provides a short take-off and landing type vector nozzle based on an airfoil guide plate and a design method thereof, which realizes efficient and reliable level flight vector and short take-off and landing functions through the deflection of a specially designed airfoil guide plate structure.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] A short take-off and landing vector nozzle based on an airfoil guide plate comprises a nozzle inlet, a straight section, a convergent section, a throat, an expansion section and a nozzle outlet which are connected in sequence. An airfoil guide plate and a rotating shaft are arranged at the nozzle outlet. The airfoil guide plate can rotate around the rotating shaft in a clockwise or counterclockwise direction from a horizontal position to a maximum geometric deflection angle γ, and no wall interference occurs during the rotation process.

[0007] The airfoil guide plate can switch between different modes by rotating at different angles, as follows:

[0008] In the non-vector mode of level flight, the airfoil guide vane is in a horizontal state and does not rotate at any angle;

[0009] In the level flight vector mode, the thrust vector angle of the nose is continuously and smoothly changed from 0° to more than γ / 5 by rotating the airfoil guide vane counterclockwise around the rotation axis at an angle not exceeding γ / 5, and the nozzle thrust performance is met; on the contrary, the thrust vector angle of the nose is continuously and smoothly changed from 0° to more than γ / 5 by rotating the airfoil guide vane clockwise around the rotation axis at an angle not exceeding γ / 5, and the nozzle thrust performance is also met;

[0010] In the short takeoff and landing mode, the airfoil guide vane rotates until the tip of its leading edge touches the upper side of the nozzle outlet. The thrust vector angle is continuously and smoothly changed in the range of 0° to greater than γ by rotating the airfoil guide vane at an angle not exceeding γ, thereby realizing the mutual switching between the level flight mode and the short takeoff and landing mode.

[0011] As an optimal technical solution, the external profile of the airfoil guide plate is a supersonic wedge, including four sections AB, BC, CD, and AD connected in sequence, wherein the AB and AD sections constitute the leading edge profile of the airfoil guide plate, the BC and CD sections constitute the trailing edge profile of the airfoil guide plate, the AB and BC sections constitute the upper profile of the airfoil guide plate, the AD and CD sections constitute the lower profile of the airfoil guide plate, and the upper profile and the lower profile are symmetrical about the horizontal center line of the nozzle.

[0012] During the rotation of the airfoil guide plate, the sum of the minimum heights of the flow channels on the upper and lower sides is always greater than the height of the throat. As a preferred technical solution, the maximum geometric deflection angle γ of the airfoil guide plate needs to satisfy γ≤cos -1 (H t / H e1 ), where Ht is the throat height, He 1 is the nozzle exit height.

[0013] The center point O of the rotating shaft on the airfoil guide plate is located on the horizontal center line of the nozzle and outside the nozzle outlet, so that the circular outer contour formed by the AO connecting line rotating 360° around point O passes through the upper side of the nozzle outlet. As a preferred technical solution, the length of the airfoil guide plate is L 2 +L 3 +L 4 , where L 2 L is the axial distance from the leading edge point A of the horizontal airfoil guide plate to the nozzle outlet. 2 satisfy L 3 is the axial distance from the center of the shaft to the nozzle outlet, L 3 satisfy L 4L is the axial distance from the trailing edge point C of the horizontal airfoil guide vane to the center of the shaft, 4 Satisfy (0.5~1)(L 2 +L 3 ).

[0014] Preferably, the included angle of the leading edge profile of the airfoil guide plate is β, and the included angle of the trailing edge profile is θ, where θ≤β.

[0015] Preferably, the leading edge line angle β of the airfoil guide plate needs to satisfy:

[0016]

[0017] Where α is the angle between the line from the leading edge point A of the horizontal airfoil guide plate to the upper side of the nozzle outlet and the central symmetry line of the horizontal airfoil guide plate; k is the specific heat ratio; M 1 is the incoming flow Mach number at the tip A of the leading edge of the airfoil guide vane, which is determined by calculating the one-dimensional isentropic flow conservation equation.

[0018] A design method for a short take-off and landing type vector nozzle based on an airfoil guide plate comprises the following steps:

[0019] Step a, determining the maximum geometric deflection angle γ of the airfoil guide plate, requiring that the sum of the minimum heights of the flow channels on the upper and lower sides of the airfoil guide plate during the rotation process is always greater than the height of the throat;

[0020] Step b, determining the position and length of the airfoil guide plate, requiring that the center point O of the rotating shaft on the airfoil guide plate is located on the horizontal center line of the nozzle and outside the nozzle outlet, and that the circular outer contour formed by the AO connecting line rotating 360° around point O passes through the upper side of the nozzle outlet;

[0021] Step c, determining the outer profile of the airfoil guide plate. In order to avoid the oblique shock wave at the leading edge of the airfoil guide plate from being reflected on the expansion section and causing greater thrust loss, it is required that the shock angle of the oblique shock wave at the leading edge of the airfoil guide plate is smaller than the angle α between the line connecting the tip A of the leading edge of the horizontal airfoil guide plate to the upper side of the nozzle outlet and the central symmetry line of the horizontal airfoil guide plate.

[0022] In step a, in the short takeoff and landing mode, the sum of the minimum heights of the flow channels on the upper and lower sides of the airfoil guide plate reaches the minimum, and the minimum flow height of the nozzle outlet at this time is defined as H e2 The throat height given by the original convergent-divergent nozzle design is Ht, and the nozzle exit height given by the original convergent-divergent nozzle design is He 1 , then H e2 =H e1 cos(γ)≥H t Therefore, the maximum geometric deflection angle γ of the airfoil guide plate must satisfy γ≤cos -1 (Ht / H e1 ).

[0023] In step b, the axial length of the expansion section is defined as L 1 , the axial distance from the leading edge point A of the horizontal airfoil guide plate to the nozzle outlet is L 2 , the axial distance from the center of the shaft to the nozzle outlet is L 3 , the axial distance from the trailing edge point C of the horizontal airfoil guide plate to the center of the shaft is L 4 , where L 1 Given by the original convergent-divergent nozzle design, L 2 satisfy L 3 satisfy L 4 Satisfy (0.5~1)(L 2 +L 3 ); therefore, the length of the airfoil guide plate is L 2 +L 3 +L 4 .

[0024] In step c, the leading edge angle formed by the leading edge profile line AB and the AD segment of the airfoil guide plate is defined as β, and the trailing edge angle formed by the trailing edge profile line BC and the CD segment of the airfoil guide plate is defined as θ; the angle between the line connecting the leading edge point A of the horizontal airfoil guide plate to the upper side of the nozzle outlet and the central symmetry line of the horizontal airfoil guide plate is defined as α, satisfying α=tan -1 (H e1 / 2L 2 )=(180-γ) / 2; When designing, it is necessary to avoid the reflection of the leading edge oblique shock wave of the airfoil guide plate on the expansion section to cause greater thrust loss, and the shock wave angle of the leading edge oblique shock wave is required to be less than α. Therefore, according to the calculation formula of the plane oblique shock wave, it can be known that the leading edge angle β of the airfoil guide plate must meet the following requirements:

[0025]

[0026] Where k is the specific heat ratio; M 1 is the incoming flow Mach number at the tip A of the leading edge of the airfoil guide vane, which is determined by calculating the one-dimensional isentropic flow conservation equation;

[0027] Without considering factors such as point ablation and point strength, from the perspective of aerodynamic performance alone, the smaller the leading edge angle β and the trailing edge angle θ of the airfoil guide plate, the better, θ≤β; on the premise that the leading edge angle β, the trailing edge angle θ and the length of the airfoil guide plate are determined, the outer surface of the airfoil guide plate is further determined.

[0028] Beneficial effects: Compared with the prior art, the present invention has the following technical effects:

[0029] (1) Compared with the traditional mechanical vector nozzle technology and vertical / short take-off and landing scheme, the nozzle of the present invention can achieve efficient and reliable level flight vector and short take-off and landing functions only by deflecting the specially designed airfoil guide plate structure. The adjustment method is simple and reliable, and the controllable thrust vector angle range is large and the linearity is good. In addition, the nozzle of the present invention does not need to deflect the nozzle as a whole, has smaller drag loss, simpler mechanical structure and lighter weight, and has less impact on the overall performance of the aircraft.

[0030] (2) Compared with the gas rudder vector nozzle, the present invention optimizes the position and external surface of the airfoil guide plate to ensure that the vector nozzle has excellent thrust performance, a larger vector angle adjustment range, and short-distance takeoff and landing capabilities.

[0031] (3) Most of the profiles of the configuration nozzle of the present invention are mainly straight lines, and the design method is simple and quick, which is convenient for improvement and rapid optimization of the design in combination with actual engineering application requirements. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a structural schematic diagram of a short take-off and landing type vector nozzle based on an airfoil guide plate of the present invention;

[0033] Figure 2 It is a structural schematic diagram of the airfoil guide plate in the present invention;

[0034] Figure 3 It is a geometric constraint diagram of the short take-off and landing vector nozzle of the present invention;

[0035] Figure 4 The figure is a comparison of Mach number cloud diagrams of the short take-off and landing vector nozzle of the present invention during the mode switching process;

[0036] Figure 5 It is a curve diagram showing the change of the vector angle, thrust coefficient and flow coefficient of the short take-off and landing vector nozzle of the present invention with the percentage of mode switching;

[0037] Figure 6 A curve diagram showing the lift efficiency and lift of the short take-off and landing vector nozzle of the present invention as a function of the mode switching percentage;

[0038] In the figure: 1, nozzle inlet, 2, straight section, 3, convergent section, 4, throat, 5, divergent section, 6, nozzle outlet, 7, airfoil guide plate, 8, rotating shaft. DETAILED DESCRIPTION

[0039] The present invention will be further explained below in conjunction with the accompanying drawings.

[0040] like Figure 1As shown, a short take-off and landing vector nozzle based on an airfoil guide plate of the present invention comprises a nozzle inlet 1, an equal straight section 2, a convergent section 3, a throat 4, an expansion section 5 and a nozzle outlet 6 which are connected in sequence. An airfoil guide plate 7 and a rotating shaft 8 are arranged at the nozzle outlet 6. The airfoil guide plate 7 can rotate around the rotating shaft 8 in a clockwise or counterclockwise direction from a horizontal position to a maximum geometric deflection angle γ, and no wall interference occurs during the rotation process.

[0041] The airfoil guide plate 7 can switch between different modes by rotating at different angles, as follows:

[0042] (a) In the non-vector mode of level flight, the airfoil guide plate 7 is in a horizontal state and does not rotate at any angle; this is equivalent to adding a drag profile to the conventional convergent-divergent nozzle outlet, which will produce a drag effect on the nozzle as a whole, resulting in thrust loss, but this effect can be effectively reduced by optimizing the position and external profile of the airfoil guide plate 7; in addition, the advantage is that this arrangement has little effect on the internal flow field of the nozzle, and the flow capacity of the nozzle is almost unchanged;

[0043] (b) In the level flight vector mode, the nose-up thrust vector angle is continuously and smoothly changed within the range of 0° to greater than γ / 5 by rotating the airfoil guide plate 7 counterclockwise around the rotation axis 8 at an angle not exceeding γ / 5, and the nozzle thrust performance is excellent; on the contrary, the nose-down thrust vector angle is continuously and smoothly changed within the range of 0° to greater than γ / 5 by rotating the airfoil guide plate 7 clockwise around the rotation axis 8 at an angle not exceeding γ / 5, and the nozzle thrust performance is also excellent; the specific change range of the pitch thrust vector angle can be adjusted according to the overall design requirements of the aircraft, while taking into account the thrust performance of the nozzle;

[0044] (c) In the short takeoff and landing mode, the airfoil guide plate 7 rotates until the tip of its leading edge touches the upper side of the nozzle outlet 6. The rotation of the airfoil guide plate 7 not exceeding the angle γ realizes the continuous and smooth change of the thrust vector angle in the range of 0° to greater than γ, thereby realizing the mutual switching between the level flight mode and the short takeoff and landing mode.

[0045] like Figure 2 As shown, the external profile of the airfoil guide plate 7 is similar to the supersonic wedge airfoil, which is a supersonic wedge, including four sections AB, BC, CD, and AD connected in sequence, wherein the AB and AD sections constitute the leading edge profile of the airfoil guide plate 7, the BC and CD sections constitute the trailing edge profile of the airfoil guide plate 7, the AB and BC sections constitute the upper profile of the airfoil guide plate 7, the AD and CD sections constitute the lower profile of the airfoil guide plate 7, and the upper profile and the lower profile are symmetrical about the horizontal center line of the nozzle. The leading edge profile AB and AD sections of the airfoil guide plate 7 constitute the leading edge angle β, and the trailing edge profile BC and CD sections of the airfoil guide plate 7 constitute the trailing edge angle θ.

[0046] Next, combine Figure 3 The geometric constraint diagram of the short take-off and landing vector nozzle shown in the figure introduces the design method of the nozzle of the present invention. Its design goal is to design an airfoil guide plate with a specific position and external surface at the outlet of a conventional convergent-divergent nozzle to meet the requirements of thrust vectoring performance under different modes. The core of its design lies in the position and external surface of the airfoil guide plate. The specific design requirements and process are as follows:

[0047] (1) Determine the maximum geometric deflection angle γ of the airfoil guide plate 7: In order to make the nozzle airflow expand and accelerate more fully in the expansion section and reduce the thrust loss caused by under-expansion, the design requires that the sum of the minimum heights of the flow channels on the upper and lower sides of the airfoil guide plate 7 during the rotation process is always greater than the height of the throat 4. In the short takeoff and landing mode, the sum of the minimum heights of the flow channels on the upper and lower sides of the airfoil guide plate 7 reaches the minimum, and the minimum flow height of the nozzle outlet at this time is defined as H e2 , the throat height 4 given by the original convergent-divergent nozzle design is H t , the nozzle outlet height 6 given by the original convergent-divergent nozzle design is He 1 , then H e2 =H e1 cos(γ)≥H t Therefore, the maximum geometric deflection angle γ of the airfoil guide plate 7 must satisfy γ≤cos -1 (H t / H e1 ). Since the important performance parameter thrust vector angle δ is positively correlated with the maximum geometric deflection angle γ, the maximum geometric deflection angle γ is the main design parameter of the present invention and needs to be finally determined in combination with the overall design requirements of the aircraft.

[0048] (2) Determine the position and length of the airfoil guide plate 7: In order to minimize the bottom resistance of the nozzle in the short takeoff and landing mode, the design requires that the center point O of the rotating shaft 8 on the airfoil guide plate 7 is located on the horizontal center line of the nozzle and outside the nozzle outlet 6, so that the circular outer contour formed by the AO connecting line rotating 360° around point O passes on the upper side of the nozzle outlet 6. The axial length of the expansion section 5 is defined as L 1 , the axial distance from the leading edge point A of the horizontal airfoil guide plate 7 to the nozzle outlet 6 is L 2 , the axial distance from the center of the shaft 8 to the nozzle outlet 6 is L 3 The axial distance from the trailing edge point C of the horizontal airfoil guide plate 7 to the center of the rotating shaft 8 is L 4 , where L 1 Given by the original convergent-divergent nozzle design, L 2 satisfy L 3 satisfy L 4 Satisfy (0.5~1)(L 2 +L3 ). Therefore, the length of the airfoil guide plate is L 2 +L 3 +L 4 .

[0049] (3) Determine the outer profile of the airfoil guide plate 7: define the angle between the line connecting the leading edge point A of the horizontal airfoil guide plate 7 to the upper side of the nozzle outlet and the central symmetry line of the horizontal airfoil guide plate 7 as α (the angle unit is degree), satisfying α=tan -1 (H e1 / 2L 2 )=(180-γ) / 2. In order to avoid the oblique shock wave at the leading edge of the airfoil guide plate 7 from being reflected on the expansion section 5 and causing greater thrust loss, the design requires that the shock wave angle of the leading edge oblique shock wave be less than α. Therefore, according to the calculation formula of the plane oblique shock wave, it can be known that the leading edge angle β of the airfoil guide plate 7 needs to satisfy:

[0050]

[0051] Where k is the specific heat ratio; M 1 is the Mach number of the incoming flow at the leading edge point A of the airfoil guide plate (7). According to the flow conservation formula of one-dimensional isentropic flow, M 1 It can be obtained by solving the following equation:

[0052]

[0053] Without considering factors such as point ablation and point strength, from the perspective of aerodynamic performance, the smaller the leading edge angle β and the trailing edge angle θ of the airfoil guide plate 7, the better. Generally, θ≤β. On the premise that the leading edge angle β, the trailing edge angle θ and the length of the airfoil guide plate 7 are determined, the outer surface of the airfoil guide plate 7 can be further determined. In addition, in actual engineering applications, if the above factors are considered, the fillet at the leading edge point A and the trailing edge point C needs to be considered. The specific fillet size is determined by actual engineering requirements and material properties.

[0054] The present invention will be further described below in conjunction with specific embodiments.

[0055] Embodiment 1:

[0056] like Figure 3 As shown, the geometric constraints of the original convergent-divergent nozzle are as follows: Throat height H t =20mm, outlet height H e1 =51mm, the axial length of the expansion section is L 1=56.7mm. The short take-off and landing vector nozzle of the present invention is provided with a specially designed airfoil guide plate near the outlet of the original convergent-divergent nozzle. The specific geometric constraints are as follows: the maximum geometric deflection angle γ = 55°, the axial distance L from the leading edge point A of the horizontal airfoil guide plate to the nozzle outlet 2 =13.3mm, axial distance L from the center of the shaft to the nozzle outlet 3 =17.8mm, the axial distance L from the trailing edge point C of the horizontal airfoil guide plate to the center of the shaft 8 4 =31.1mm, the leading edge line AB and AD of the airfoil guide plate form a leading edge angle β = 10°, the trailing edge line BC and CD of the airfoil guide plate form a trailing edge angle θ = 2.1°, and the minimum flow height of the nozzle outlet in the short takeoff and landing mode is H e2 =29.2mm, meeting the design requirement H e2 ≥H t .

[0057] Two-dimensional numerical simulation calculations were carried out on the short take-off and landing vector nozzle of the present invention under the designed pressure drop ratio (NPR=14) working condition, and the relevant performance parameters were summarized.

[0058] Figure 4 The Mach number cloud diagram of the short take-off and landing vector nozzle of the present invention during the mode switching process is compared. It can be found that when the mode switching is 0% (non-vector state), the weak oblique shock wave generated by the leading edge of the airfoil guide plate is not reflected on the expansion section, which meets the design requirements, and the thrust coefficient is maintained at about 0.98, which is within the allowable range; in the process of mode switching from 0% to 60%, as the angle of attack of the airfoil guide plate further increases, the leading edge oblique shock wave gradually strengthens; when the mode switching is 80%, the upper wall surface of the nozzle expansion section and the guide plate form a leaky concave cavity, and a separation zone is generated under the action of the adverse pressure gradient and fluid viscosity, the stronger leading edge oblique shock wave disappears, and the weaker λ separation shock wave is generated; when the mode switching is 100%, the upper wall surface of the nozzle expansion section and the guide plate form a closed concave cavity, the separation zone is further increased, the separation point moves forward to the throat position, the upper surface λ separation shock wave disappears, and the weaker λ shock wave on the lower wall is generated. In general, the flow field in the nozzle changes little, and the lift is mainly generated by the pressure difference between the upper and lower walls of the airfoil guide vane.

[0059] Figure 5 The following is a graph showing the vector angle, thrust coefficient and flow coefficient of the short take-off and landing vector nozzle of the present invention as the percentage of mode switching changes. It can be found that the thrust vector angle changes continuously in the range of 0° to 60° with the percentage of mode switching, and the linearity is good; the thrust coefficient shows a trend of decreasing first and then increasing as a whole, and is above 0.87. Figure 4From the Mach number cloud diagram in , it can be found that in the process of mode switching from 0% to 60%, as the angle of attack of the airfoil guide vane further increases, the leading edge oblique shock wave gradually strengthens, so the thrust coefficient gradually decreases; when the mode switching is 80%, the stronger leading edge oblique shock wave disappears, and the weaker λ separation shock wave is generated, so the thrust coefficient increases; when the mode switching is 100%, the upper surface λ separation shock wave disappears, and the weaker λ shock wave is generated on the lower wall, so the thrust coefficient increases. The additional arrangement of the airfoil guide vane at the outlet has little effect on the internal flow field of the nozzle, and the sound velocity surface at the throat changes very little, so the flow coefficient hardly changes. Figure 6 This is a curve diagram of the lift efficiency and lift of the short take-off and landing vector nozzle of the present invention as the mode switching percentage changes. Since the ideal thrust of the nozzle does not change much, the lift coefficient and lift change rules are relatively consistent, and both gradually increase with the mode switching. In general, the thrust coefficient of the nozzle can reach 0.98 in the level flight non-vector mode; when the thrust vector angle changes in the range of 0° to 15° in the level flight vector mode, the thrust coefficient is above 0.96; in the short take-off and landing mode, the thrust vector angle can reach 60°, the thrust coefficient can reach above 0.94, and the lift efficiency can reach above 0.8.

[0060] In summary, the numerical simulation results effectively verify that the short take-off and landing vector nozzle of the present invention has a large controllable thrust vector angle range, good linearity and excellent thrust performance during the mode switching process.

[0061] The thrust vector angle is changed continuously and smoothly within a large angle range by rotating the airfoil guide vane at a certain angle, thereby realizing the mutual switching between the level flight mode and the short takeoff and landing mode. The present invention only sets a specially designed airfoil guide vane near the conventional convergent-divergent nozzle outlet, which ensures that the nozzle thrust performance changes less, and has the dual functions of level flight vector adjustment and short takeoff and landing. Both of them only require the rotation of one guide vane, the adjustment method is simple and reliable, the controllable thrust vector angle range is large and the linearity is good, and a vector nozzle design scheme is provided for the development of future high-performance, short takeoff and landing aircraft.

[0062] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A short take-off and landing type vector nozzle based on an airfoil guide plate, characterized in that: The invention comprises a nozzle inlet (1), a straight section (2), a convergent section (3), a throat (4), an expansion section (5) and a nozzle outlet (6) which are connected in sequence. An airfoil guide plate (7) and a rotating shaft (8) are arranged at the nozzle outlet (6). The airfoil guide plate (7) can be rotated clockwise or counterclockwise around the rotating shaft (8) from a horizontal position to a maximum geometric deflection angle γ, and no wall interference occurs during the rotation process.

2. According to claim 1, a short take-off and landing vector nozzle based on an airfoil guide plate is characterized in that: The airfoil guide plate (7) can switch between different modes by rotating at different angles, as follows: In the level flight non-vector mode, the airfoil guide plate (7) is in a horizontal state and does not rotate at any angle; In the level flight vector mode, the wing guide plate (7) rotates counterclockwise around the rotation axis (8) at an angle not exceeding γ / 5 to achieve a continuous and smooth change in the range of 0° to greater than γ / 5 for the head-up thrust vector angle, and the nozzle thrust performance is satisfied; conversely, the wing guide plate (7) rotates clockwise around the rotation axis (8) at an angle not exceeding γ / 5 to achieve a continuous and smooth change in the range of 0° to greater than γ / 5 for the head-down thrust vector angle, and the nozzle thrust performance is also satisfied; In the short take-off and landing mode, the airfoil guide plate (7) rotates until the tip of its leading edge touches the upper side of the nozzle outlet (6), and the thrust vector angle is continuously and smoothly changed in the range of 0° to greater than γ by the rotation of the airfoil guide plate (7) at an angle not exceeding γ, thereby realizing the mutual switching between the level flight mode and the short take-off and landing mode.

3. The short take-off and landing type vector nozzle based on an airfoil guide plate according to claim 1, characterized in that: The outer profile of the airfoil guide plate (7) is a supersonic wedge, comprising four sections AB, BC, CD, and AD connected in sequence, wherein the AB and AD sections constitute the leading edge profile of the airfoil guide plate (7), the BC and CD sections constitute the trailing edge profile of the airfoil guide plate (7), the AB and BC sections constitute the upper profile of the airfoil guide plate (7), and the AD and CD sections constitute the lower profile of the airfoil guide plate (7), and the upper profile and the lower profile are symmetrical about the horizontal center line of the nozzle.

4. The short take-off and landing type vector nozzle based on an airfoil guide plate according to claim 1, characterized in that: During the rotation of the airfoil guide plate (7), the sum of the minimum heights of the flow channels on the upper and lower sides thereof is always greater than the height of the throat (4); The maximum geometric deflection angle γ of the airfoil guide plate (7) must satisfy γ≤cos -1 (H t / H e1 ), where Ht is the height of the throat (4), H e1 is the height of the nozzle outlet (6).

5. The short take-off and landing type vector nozzle based on an airfoil guide plate according to claim 1, characterized in that: The center point O of the rotating shaft (8) on the airfoil guide plate (7) is located on the horizontal center line of the nozzle and outside the nozzle outlet (6), so that the circular outer contour formed by the AO connecting line rotating 360° around the point O passes through the upper side of the nozzle outlet (6); The length of the airfoil guide plate (7) is L2+L3+L4, wherein L2 is the axial distance from the leading edge point A of the airfoil guide plate (7) in the horizontal state to the nozzle outlet (6), and L2 satisfies L3 is the axial distance from the center of the rotating shaft (8) to the nozzle outlet (6), and L3 satisfies L4 is the axial distance from the trailing edge point C of the horizontal airfoil guide plate (7) to the center of the rotating shaft (8), and L4 satisfies (0.5-1)(L2+L3).

6. The short take-off and landing type vector nozzle based on an airfoil guide plate according to claim 1, characterized in that: The included angle of the leading edge profile of the airfoil guide plate (7) is β, and the included angle of the trailing edge profile is θ, θ≤β; The leading edge profile angle β of the airfoil guide plate (7) must satisfy: Wherein, α is the angle between the line from the leading edge point A of the horizontal airfoil guide plate (7) to the upper side of the nozzle outlet and the central symmetry line of the horizontal airfoil guide plate (7); k is the specific heat ratio; M1 is the incoming flow Mach number at the leading edge point A of the airfoil guide plate (7), which is calculated and determined by the one-dimensional isentropic flow conservation equation.

7. A design method for a short take-off and landing vector nozzle based on an airfoil guide plate according to any one of claims 1 to 6, characterized in that: The following steps are involved: Step a, determining the maximum geometric deflection angle γ of the airfoil guide plate (7), requiring that the sum of the minimum heights of the flow channels on the upper and lower sides of the airfoil guide plate (7) during the rotation process is always greater than the height of the throat (4); Step b, determining the position and length of the airfoil guide plate (7), requiring that the center point O of the rotating shaft (8) on the airfoil guide plate (7) is located on the horizontal center line of the nozzle and outside the nozzle outlet (8), and that the circular outer contour formed by the AO connecting line rotating 360° around the point O passes through the upper side of the nozzle outlet (8); Step c, determining the outer profile of the airfoil guide plate (7). In order to avoid the oblique shock wave at the leading edge of the airfoil guide plate (7) from being reflected on the expansion section (5) to cause a greater thrust loss, it is required that the shock wave angle of the oblique shock wave at the leading edge of the airfoil guide plate (7) is smaller than the angle α between the line connecting the leading edge point A of the horizontal airfoil guide plate (7) to the upper side of the nozzle outlet and the central symmetry line of the horizontal airfoil guide plate (7).

8. The design method according to claim 7, characterized in that: In step a, in the short takeoff and landing mode, the sum of the minimum heights of the flow channels on the upper and lower sides of the airfoil guide plate (7) reaches the minimum, and the minimum flow height of the nozzle outlet at this time is defined as H e2 The throat height (4) given by the original convergent-divergent nozzle design is H t , the nozzle outlet height (6) given by the original convergent-divergent nozzle design is He1, then H e2 =H e1 cos(γ)≥H t Therefore, the maximum geometric deflection angle γ of the airfoil guide plate (7) must satisfy γ≤cos -1 (H t / H e1 ).

9. The design method according to claim 7, characterized in that: In step b, the axial length of the expansion section (5) is defined as L1, the axial distance from the leading edge point A of the horizontal airfoil guide plate (7) to the nozzle outlet (6) is defined as L2, the axial distance from the center of the rotating shaft (8) to the nozzle outlet (6) is defined as L3, and the axial distance from the trailing edge point C of the horizontal airfoil guide plate (7) to the center of the rotating shaft (8) is defined as L4, wherein L1 is given by the original convergent-divergent nozzle design, and L2 satisfies L3 Satisfaction L4 satisfies (0.5-1)(L2+L3); therefore, the length of the airfoil guide plate (7) is L2+L3+L4.

10. The design method according to claim 7, characterized in that: In step c, the leading edge angle formed by the leading edge profile line AB and the AD segment of the airfoil guide plate (7) is defined as β, and the trailing edge angle formed by the trailing edge profile line BC and the CD segment of the airfoil guide plate (7) is defined as θ; the angle between the line connecting the leading edge point A of the horizontal airfoil guide plate (7) to the upper side of the nozzle outlet and the central symmetry line of the horizontal airfoil guide plate (7) is defined as α, satisfying α=tan -1 (H e1 / 2L2)=(180-γ) / 2; when designing, it is necessary to avoid the leading edge oblique shock wave of the airfoil guide plate (7) from being reflected on the expansion section (5) to cause greater thrust loss, and the shock wave angle of the leading edge oblique shock wave is required to be less than α. Therefore, according to the calculation formula of the plane oblique shock wave, it can be known that the leading edge angle β of the airfoil guide plate (7) needs to satisfy: Wherein, k is the specific heat ratio; M1 is the incoming flow Mach number at the leading edge point A of the airfoil guide plate (7), which is determined by calculating the one-dimensional isentropic flow conservation equation; Without considering factors such as point ablation and point strength, from the perspective of aerodynamic performance alone, the smaller the leading edge angle β and the trailing edge angle θ of the airfoil guide plate (7), the better, θ≤β; on the premise that the leading edge angle β, the trailing edge angle θ and the length of the airfoil guide plate (7) are determined, the outer profile of the airfoil guide plate (7) is further determined.

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