A method for designing the shape of the concave leading edge ventral fin of a high-speed aircraft

Abstract

This invention discloses a method for designing the concave leading-edge ventral fin shape of a high-speed aircraft, belonging to the field of aerodynamic shape design technology for high-speed aircraft. It solves the problems of discontinuous leading-edge surface pressure and low and unevenly distributed surface pressure at the root of the ventral fin in existing technologies, and is applied to the aerodynamic shape design of high-speed aircraft. The method includes: selecting the starting position of the ventral fin on the centerline of the windward lower surface of the high-speed aircraft, and establishing a coordinate system for the leading-edge centerline of the ventral fin with the starting position of the ventral fin as the origin; determining the sweep angle of the concave leading-edge ventral fin; obtaining the sweep length of the concave leading-edge ventral fin based on the sweep angle and the height of the concave leading-edge ventral fin; obtaining the leading-edge centerline of the concave leading-edge ventral fin; and determining the leading-edge radius of the concave leading-edge ventral fin. This invention improves the efficiency of the ventral fin of high-speed aircraft, reduces the ventral fin area, and provides support for weight reduction and overall performance improvement of the aircraft.

Description

Technical Field

[0001] This invention belongs to the field of aerodynamic shape design technology for high-speed aircraft, and particularly relates to a method for designing the shape of the concave leading edge ventral fin of a high-speed aircraft. Background Technology

[0002] In the aerodynamic design of high-speed aircraft, ventral fins are typically used on the windward side to meet the requirements for strong lateral static stability. To improve ventral fin efficiency and minimize drag, the ventral fins of high-speed aircraft are generally positioned near the bottom of the windward side and feature a triangular design with a swept-back leading edge. However, the ventral fins themselves increase the aircraft's weight; therefore, improving ventral fin efficiency is crucial to enhancing the overall performance of the aircraft. Because the swept-back triangular ventral fin has a straight leading edge, the surface pressure at the leading edge is discontinuous during flight, resulting in lower and unevenly distributed surface pressure at the fin root. Summary of the Invention

[0003] The technical problem solved by this invention is to overcome the shortcomings of the prior art and provide a design method for the concave leading edge ventral fin of a high-speed aircraft, which improves the efficiency of the ventral fin of the high-speed aircraft, reduces the ventral fin area, and provides support for the weight reduction and overall performance improvement of the aircraft.

[0004] The objective of this invention is achieved through the following technical solution: a method for designing the shape of a concave leading edge ventral fin of a high-speed aircraft, comprising: selecting the starting position of the ventral fin on the centerline of the windward lower surface of the high-speed aircraft, and establishing a coordinate system of the ventral fin leading edge centerline with the starting position of the ventral fin as the origin; wherein, in the coordinate system of the ventral fin leading edge centerline, the X-axis is perpendicular to the bottom surface of the aircraft and points to the bottom of the aircraft; the Y-axis is perpendicular to the X-axis in the longitudinal symmetry plane of the aircraft and points downwards from the aircraft; determining the sweep angle of the concave leading edge ventral fin; obtaining the sweep length of the concave leading edge ventral fin based on the sweep angle and the height of the concave leading edge ventral fin; obtaining the leading edge centerline of the concave leading edge ventral fin based on the length of the concave leading edge ventral fin, the sweep length of the concave leading edge ventral fin, and the height of the concave leading edge ventral fin; and determining the leading edge radius of the concave leading edge ventral fin.

[0005] In the above-mentioned design method for the concave leading edge ventral fin of a high-speed aircraft, the sweep angle of the concave leading edge ventral fin... satisfy: ; The sweep length of the concave leading edge of the ventral fin is obtained by the following formula: ; in, The length of the outward sweep of the concave anterior margin of the ventral fin. The height of the ventral fin at the concave anterior margin.

[0006] In the above-mentioned design method for the concave leading edge ventral fin of a high-speed aircraft, the formula for the centerline of the leading edge of the concave leading edge ventral fin is as follows: ; in, The length of the concave anterior margin of the pelvic fin. The length of the outward sweep of the concave anterior margin of the ventral fin. The height of the pelvic fin at the concave anterior margin. The coefficient used to control the degree of concavity of the anterior edge of the pelvic fin. Let x be the x-coordinate of the center line of the anterior margin of the pelvic fin in the coordinate system of the center line of the anterior margin of the pelvic fin. The y-coordinate of the center line of the anterior margin of the pelvic fin in the coordinate system of the center line of the anterior margin of the pelvic fin.

[0007] In the above-mentioned design method for the concave leading edge ventral fin of a high-speed aircraft, the length of the concave leading edge ventral fin... Satisfy the following formula: ; in, For the length of the aircraft, The origin of the coordinate system for the centerline of the ventral fin's leading edge is located in the aircraft's geometric coordinate system. x Coordinate values.

[0008] In the above-mentioned design method for the concave leading edge ventral fin of a high-speed aircraft, the origin of the coordinate system is the apex of the aircraft's nose. Oa , Xa The axis is perpendicular to the bottom surface of the aircraft and points towards the bottom of the aircraft. Ya The axis is perpendicular to the longitudinal plane of symmetry of the aircraft. Xa The axis points upwards from the aircraft.

[0009] In the above-mentioned design method for the concave leading edge ventral fin of a high-speed aircraft, the height of the concave leading edge ventral fin... Satisfy the following formula: ; in, For the length of the aircraft, The lower cone angle of the aircraft. The angle of the oblique shock wave on the lower surface of the aircraft.

[0010] In the above-mentioned design method for the concave leading edge ventral fin of a high-speed aircraft, the oblique shock wave angle on the lower surface of the aircraft... Satisfy the following formula: ; in, The flight Mach number of the aircraft. The value is the lower cone angle of the aircraft in radians.

[0011] In the aforementioned method for designing the shape of the concave leading edge ventral fin of a high-speed aircraft, the coefficient used to control the degree of concavity of the concave leading edge ventral fin is... The value range is 1.4 to 1.8.

[0012] In the above-mentioned design method for the concave leading edge ventral fin of a high-speed aircraft, the leading edge radius of the concave leading edge ventral fin is 15mm~35mm.

[0013] A design system for the concave leading edge ventral fin of a high-speed aircraft includes: a first module for selecting the starting position of the ventral fin on the centerline of the windward lower surface of the high-speed aircraft, and establishing a coordinate system for the leading edge centerline of the ventral fin with the starting position of the ventral fin as the origin; wherein, in the coordinate system for the leading edge centerline of the ventral fin, the X-axis is perpendicular to the bottom surface of the aircraft and points to the bottom of the aircraft; the Y-axis is perpendicular to the X-axis in the longitudinal symmetry plane of the aircraft and points downwards from the aircraft; a second module for determining the sweep angle of the concave leading edge ventral fin; and obtaining the sweep length of the concave leading edge ventral fin based on the sweep angle and the height of the concave leading edge ventral fin; a third module for obtaining the leading edge centerline of the concave leading edge ventral fin based on the length of the concave leading edge ventral fin, the sweep length of the concave leading edge ventral fin, and the height of the concave leading edge ventral fin; and a fourth module for determining the leading edge radius of the concave leading edge ventral fin.

[0014] Compared with the prior art, the present invention has the following advantages: This invention effectively improves the efficiency of the ventral fin of high-speed aircraft. Under the condition of obtaining the same lateral stability, the ventral fin has a smaller area and lighter weight, providing strong support for the improvement of the overall performance of the aircraft. Attached Figure Description

[0015] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of preferred embodiments. The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Furthermore, the same reference numerals denote the same parts throughout the drawings. In the drawings: Figure 1 This is a schematic diagram of the ventral fin of a high-speed aircraft provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the concave anterior edge of the pelvic fin provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the coordinate system of the center line of the anterior edge of the pelvic fin provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the coordinate system of the center line of the anterior edge of the pelvic fin provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the aircraft geometric coordinate system provided in an embodiment of the present invention. Detailed Implementation

[0016] Exemplary embodiments of the present disclosure will now be described in more detail with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0017] Figure 1 This is a schematic diagram of the ventral fin of a high-speed aircraft provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of the concave anterior edge of the pelvic fin provided in an embodiment of the present invention; Figure 3 This is a schematic diagram of the coordinate system of the center line of the anterior edge of the pelvic fin provided in an embodiment of the present invention; Figure 4 This is a schematic diagram of the coordinate system of the center line of the anterior edge of the pelvic fin provided in an embodiment of the present invention; Figure 5 This is a schematic diagram of the aircraft geometric coordinate system provided in an embodiment of the present invention.

[0018] This embodiment provides a method for designing the shape of the concave leading-edge ventral fin of a high-speed aircraft, the method comprising: On the centerline of the windward lower surface of the high-speed aircraft, select the starting position of the ventral fin, and establish a coordinate system of the ventral fin leading edge centerline with the starting position of the ventral fin as the origin; in the coordinate system of the ventral fin leading edge centerline, the X-axis is perpendicular to the bottom surface of the aircraft and points to the bottom of the aircraft; the Y-axis is perpendicular to the X-axis in the longitudinal symmetry plane of the aircraft and points downward of the aircraft. Determine the sweep angle of the concave anterior pelvic fin; obtain the sweep length of the concave anterior pelvic fin based on the sweep angle and the height of the concave anterior pelvic fin. The centerline of the anterior edge of the concave anterior edge ventral fin is obtained based on the length of the concave anterior edge ventral fin, the outward sweep length of the concave anterior edge ventral fin, and the height of the concave anterior edge ventral fin. Determine the radius of the anterior edge of the concave anterior edge of the pelvic fin.

[0019] Outer sweep angle of the concave anterior margin of the pelvic fin satisfy: .

[0020] The sweep length of the concave leading edge of the ventral fin is obtained by the following formula: ; in, The length of the outward sweep of the concave anterior margin of the ventral fin. The height of the ventral fin at the concave anterior margin.

[0021] The formula for the center line of the anterior margin of the concave anterior margin pelvic fin is as follows: ; in, The length of the concave anterior margin of the pelvic fin. The length of the outward sweep of the concave anterior margin of the ventral fin. The height of the pelvic fin at the concave anterior margin. The coefficient used to control the degree of concavity of the anterior margin of the pelvic fin. Let x be the x-coordinate of the center line of the anterior margin of the pelvic fin in the coordinate system of the center line of the anterior margin of the pelvic fin. The y-coordinate of the center line of the anterior margin of the pelvic fin in the coordinate system of the center line of the anterior margin of the pelvic fin.

[0022] Length of the concave anterior margin of the pelvic fin Satisfy the following formula: ; in, For the length of the aircraft, The origin of the coordinate system for the centerline of the ventral fin's leading edge is located in the aircraft's geometric coordinate system. x Coordinate values.

[0023] In the aircraft's geometric coordinate system, the origin is the vertex of the aircraft's nose. Oa , Xa The axis is perpendicular to the bottom surface of the aircraft and points towards the bottom of the aircraft. Ya The axis is perpendicular to the longitudinal plane of symmetry of the aircraft. Xa The axis points upwards from the aircraft.

[0024] Height of the concave anterior edge of the pelvic fin Satisfy the following formula: ; in, For the length of the aircraft, The lower cone angle of the aircraft. The angle of the oblique shock wave on the lower surface of the aircraft.

[0025] Satisfy the following formula: ; in, The flight Mach number of the aircraft. The value is the lower cone angle of the aircraft in radians.

[0026] Coefficient used to control the degree of concavity of the anterior edge of the pelvic fin. The value range is 1.4 to 1.8.

[0027] The radius of the anterior edge of the concave anterior edge pelvic fin is 15mm~35mm. The sweep angle of the concave anterior edge pelvic fin is 45°~90°.

[0028] Specifically, the method includes the following steps: Step 1: On the center line of the windward lower surface of the high-speed aircraft, select the starting position of the ventral fin, and use this as the origin O ( Figure 3 Establish a coordinate system with the centerline of the leading edge of the ventral fin. The X-axis is perpendicular to the bottom surface of the aircraft and points to the bottom of the aircraft. The Y-axis is perpendicular to the X-axis within the longitudinal symmetry plane of the aircraft and points downwards from the aircraft. Figure 4 ).

[0029] The pelvic fins should originate after the aircraft's center of gravity, i.e. ,in Xo The origin O of the coordinate system for the centerline of the ventral fin's leading edge is located in the aircraft's geometric coordinate system. x Coordinate values Xcg Let the center of mass of the aircraft be in the geometric coordinate system of the aircraft. x Coordinate values.

[0030] Step 2: Determine the sweep angle of the concave anterior edge pelvic fin; based on the sweep angle and the height of the concave anterior edge pelvic fin, obtain the sweep length of the concave anterior edge pelvic fin.

[0031] Determine the outer sweep angle of the pelvic fin ( Figure 4 Outer sweep angle It should meet the following requirements:

[0032] Under the condition that the above requirements are met, the pelvic fin sweep angle The smaller the better. Given a fixed pelvic fin height H, the outer sweep angle... The smaller the effective lateral area of ​​the ventral fin, the greater the distance between it and the aircraft's center of mass, the longer the lever arm of the yaw moment that generates lateral stability of the aircraft, and the higher the efficiency of the ventral fin.

[0033] Outer sweep angle The determination of the ventral fin also needs to meet the requirements of the aircraft's installation structure: since the swept-out ventral fin extends beyond the aircraft's fuselage, the design should avoid interference with surrounding structures such as the aircraft's rear booster.

[0034] In the design of the ventral fin of a certain aircraft, the straight leading edge triangular ventral fin was changed to an outward sweep fin (sweep angle 60°) while keeping the bottom side length L and height H of the ventral fin unchanged. The ventral fin side area (weight) remained unchanged, and the ventral fin efficiency (the yaw moment of the aircraft generated per unit side area of ​​the ventral fin) could be increased by more than 30%.

[0035] Step 3: Obtain the center line of the anterior edge of the concave pelvic fin using the following formula: , ; in, LThe length of the pelvic fin. H This refers to the height of the pelvic fin. n This can be used to control the degree of inward concavity of the pelvic fins. The coordinate system of the center line of the anterior margin of the pelvic fin. x coordinate, The y-coordinate of the centerline of the anterior margin of the pelvic fin in the coordinate system of the centerline of the anterior margin of the pelvic fin.

[0036] By employing a power-law curve to obtain the centerline of the ventral fin's leading edge, compared to a straight leading edge, the concave power-law curve surface can produce an approximately isentropic compression effect under high-speed flight conditions. This concentrates the high-pressure zone of the ventral fin in the rear region, away from the aircraft's center of mass, achieving a more than 20% increase in ventral fin efficiency while reducing its area (weight). Furthermore, the concave power-law curve of the ventral fin's leading edge can eliminate shock wave interference that might occur with a straight leading edge, effectively reducing the leading edge thermal environment.

[0037] The starting point of the anterior margin centerline of the pelvic fin is the origin O of the coordinate system of the anterior margin centerline of the pelvic fin, and the ending point is the vertex D of the anterior margin centerline of the pelvic fin. Figure 4 Once the positions of point O, Lw, and H are determined, the position of point D can be determined. Generally, L , H and n The value of is determined based on the lateral stability requirements of the high-speed aircraft. Specific values ​​can be referenced from the following requirements: 1. Length of the base of the pelvic fin L After determining the starting position of the pelvic fin (point O), L Since it has been determined, ,in, For the length of the aircraft, The origin of the coordinate system for the centerline of the ventral fin's leading edge is located in the aircraft's geometric coordinate system. x Coordinate values.

[0038] 2. Pelvic fin height H To achieve higher lateral stability of the aircraft, H The larger the better, but it is necessary to avoid shock wave interference between the aircraft's nose shock wave and the leading edge of the ventral fin. H The value should meet the following requirements:

[0039] in, La The length of the aircraft; θ The lower cone angle of the aircraft, i.e., the angle between the centerline of the lower surface of the aircraft and the geometric coordinate system of the aircraft. Xa The equivalent included angle of the axis.

[0040] The angle of the oblique shock wave on the lower surface of the aircraft is obtained by the following formula, where, The flight Mach number of the aircraft. In radians θ Angle value.

[0041]

[0042] The lower cone angle θ of the aircraft and the flight Mach number By calculating the oblique shock wave angle β on the lower surface of the aircraft, the position of the nose shock wave on the lower surface of the aircraft can be determined. The method of determining the height H of the pelvic fin can effectively avoid interference between the head shock wave and the leading edge of the pelvic fin. Compared with the interference state, the maximum heat flux at the leading edge of the pelvic fin can be reduced by more than 50%, effectively reducing the thermal environment of the pelvic fin.

[0043] 3. Length of pelvic fin sweep

[0044] From the height of the pelvic fin H and outer sweep angle Sure:

[0045] 4. n value Given a fixed lateral area of ​​the pelvic fin n The higher the value, the greater the inward concavity of the anterior edge of the pelvic fin, the more concentrated the surface pressure of the pelvic fin becomes at the rear, resulting in higher pelvic fin efficiency, but also greater drag from the anterior edge. During the design process... n The value typically ranges from 1.4 to 1.8. When n When the value is less than 1.4, the effect of the inward concavity of the anterior margin of the pelvic fin is not obvious; when n When the value is greater than 1.8, the efficiency of the pelvic fin will still increase, but the additional drag will offset the benefits of the increased efficiency of the pelvic fin, or even bring negative benefits. n A value of 1.4 to 1.8 can improve ventral fin efficiency by 20% to 50% while ensuring that the increase in drag does not exceed 5%.

[0046] A certain high-speed aircraft, in terms of ventral fin length L and pelvic fin height H Under certain conditions, when n When the value is 1.6, it is similar to the straight leading edge ( n Compared to option 1), pelvic fin efficiency can be increased by 25%, while drag only increases by 3%.

[0047] Step 3: Determine the radius R of the leading edge of the pelvic fin based on its heat protection requirements. Generally, the value is between 15mm and 35mm.

[0048] Definition of aircraft geometric coordinate system ( Figure 5): The origin of the coordinate system is the vertex of the aircraft's tip. Oa , Xa The axis is perpendicular to the bottom surface of the aircraft and points towards the bottom of the aircraft. Ya The axis is perpendicular to the longitudinal plane of symmetry of the aircraft. Xa The axis points upwards from the aircraft.

[0049] This embodiment also provides a design system for a concave leading-edge ventral fin of a high-speed aircraft. The system includes: a first module for selecting the starting position of the ventral fin on the centerline of the windward lower surface of the high-speed aircraft, and establishing a coordinate system for the leading-edge centerline of the ventral fin with the starting position of the ventral fin as the origin; wherein, in the coordinate system for the leading-edge centerline of the ventral fin, the X-axis is perpendicular to the bottom surface of the aircraft and points to the bottom of the aircraft; the Y-axis is perpendicular to the X-axis in the longitudinal symmetry plane of the aircraft and points downwards from the aircraft; a second module for determining the sweep angle of the concave leading-edge ventral fin; and obtaining the sweep length of the concave leading-edge ventral fin based on the sweep angle and the height of the concave leading-edge ventral fin; a third module for obtaining the leading-edge centerline of the concave leading-edge ventral fin based on the length of the concave leading-edge ventral fin, the sweep length of the concave leading-edge ventral fin, and the height of the concave leading-edge ventral fin; and a fourth module for determining the leading-edge radius of the concave leading-edge ventral fin.

[0050] This embodiment effectively improves the efficiency of the ventral fin of a high-speed aircraft. Under the condition of obtaining the same lateral stability, the ventral fin has a smaller area and lighter weight, providing strong support for the improvement of the overall performance of the aircraft.

[0051] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A method for designing the shape of a concave leading-edge ventral fin of a high-speed aircraft, characterized in that... include: On the centerline of the windward lower surface of the high-speed aircraft, select the starting position of the ventral fin, and establish a coordinate system of the ventral fin leading edge centerline with the starting position of the ventral fin as the origin; in the coordinate system of the ventral fin leading edge centerline, the X-axis is perpendicular to the bottom surface of the aircraft and points to the bottom of the aircraft; the Y-axis is perpendicular to the X-axis in the longitudinal symmetry plane of the aircraft and points downward of the aircraft. Determine the sweep angle of the concave anterior pelvic fin; obtain the sweep length of the concave anterior pelvic fin based on the sweep angle and the height of the concave anterior pelvic fin. The centerline of the anterior edge of the concave anterior edge ventral fin is obtained based on the length of the concave anterior edge ventral fin, the outward sweep length of the concave anterior edge ventral fin, and the height of the concave anterior edge ventral fin. Determine the radius of the anterior edge of the concave anterior edge of the pelvic fin.

2. The method for designing the concave leading edge ventral fin shape of a high-speed aircraft according to claim 1, characterized in that: Outer sweep angle of the concave anterior margin of the pelvic fin satisfy: ; The sweep length of the concave leading edge of the ventral fin is obtained by the following formula: ； in, The length of the outward sweep of the concave anterior margin of the ventral fin. The height of the ventral fin at the concave anterior margin.

3. The method for designing the concave leading edge ventral fin shape of a high-speed aircraft according to claim 1, characterized in that: The formula for the center line of the anterior margin of the concave anterior margin pelvic fin is as follows: ； in, The length of the concave anterior margin of the pelvic fin. The length of the outward sweep of the concave anterior margin of the ventral fin. The height of the pelvic fin at the concave anterior margin. The coefficient used to control the degree of concavity of the anterior margin of the pelvic fin. Let x be the x-coordinate of the center line of the anterior margin of the pelvic fin in the coordinate system of the center line of the anterior margin of the pelvic fin. The y-coordinate of the center line of the anterior margin of the pelvic fin in the coordinate system of the center line of the anterior margin of the pelvic fin.

4. The method for designing the concave leading edge ventral fin shape of a high-speed aircraft according to claim 3, characterized in that: Length of the concave anterior margin of the pelvic fin Satisfy the following formula: ； in, For the length of the aircraft, The origin of the coordinate system for the centerline of the ventral fin's leading edge is located in the aircraft's geometric coordinate system. x Coordinate values.

5. The method for designing the concave leading edge ventral fin shape of a high-speed aircraft according to claim 4, characterized in that: In the aircraft's geometric coordinate system, the origin is the vertex of the aircraft's nose. Oa , Xa The axis is perpendicular to the bottom surface of the aircraft and points towards the bottom of the aircraft. Ya The axis is perpendicular to the longitudinal plane of symmetry of the aircraft. Xa The axis points upwards from the aircraft.

6. The method for designing the concave leading edge ventral fin shape of a high-speed aircraft according to claim 3, characterized in that: Height of the concave anterior edge of the pelvic fin Satisfy the following formula: ； in, For the length of the aircraft, The lower cone angle of the aircraft. The angle of the oblique shock wave on the lower surface of the aircraft.

7. The method for designing the concave leading edge ventral fin shape of a high-speed aircraft according to claim 6, characterized in that: Shock wave angle on the lower surface of the aircraft Satisfy the following formula: ； in, The flight Mach number of the aircraft. The value represents the aircraft's downward cone angle in radians. The angle of the oblique shock wave on the lower surface of the aircraft.

8. The method for designing the concave leading edge ventral fin shape of a high-speed aircraft according to claim 3, characterized in that: Coefficient used to control the degree of concavity of the anterior edge of the pelvic fin. The value range is 1.4 to 1.

8.

9. The method for designing the concave leading edge ventral fin shape of a high-speed aircraft according to claim 1, characterized in that: The radius of the anterior edge of the concave anterior edge of the pelvic fin is 15mm~35mm.

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