High-lift low-resistance airfoil profile, wing and aircraft

Abstract

The invention discloses a high-lift low-resistance airfoil profile, a wing and an aircraft, and relates to the technical field of aircrafts, the leading edge radius of the high-lift low-resistance airfoil profile is 0.02474 + / -1%, the maximum thickness of the high-lift low-resistance airfoil profile is 0.15096 + / -1%, the high-lift low-resistance airfoil profile is located at the position of 27.7%-29.7% chord length of the high-lift low-resistance airfoil profile, the maximum camber of the high-lift low-resistance airfoil profile is 0.018421 + / -1%, and the high-lift low-resistance airfoil profile is located at the position of 26.3%-28.3% chord length of the high-lift low-resistance airfoil profile. The radius of the leading edge, the maximum thickness and the maximum camber are all described by adopting dimensionless quantities, and the dimensionless process takes the chord length c of the airfoil as a reference. According to the high-lift low-resistance airfoil profile, the lift coefficient at the same angle of attack is increased, the lift coefficient at a low-speed design point is increased to 1.2262 from 1.0779, and the low-speed characteristic is improved; the lift coefficient is increased under the high subsonic velocity condition, the lift-drag ratio at the high-speed design point is increased from 61 to about 66, and in the range with the higher lift coefficient, the lift-drag ratio is increased more remarkably.

Description

Technical Field

[0001] This invention relates to the field of aircraft technology, and in particular to a high-lift, low-drag airfoil, wing, and aircraft. Background Technology

[0002] The aerodynamic configuration of the airfoil is one of the core factors determining the overall performance of large fixed-wing carrier-based unmanned aerial vehicles (UAVs). For carrier-based UAVs, there are two core mission phases: takeoff and landing from the ship and high-altitude long-endurance cruise. Unlike land-based aircraft, carrier-based UAVs face extremely demanding takeoff and landing conditions, requiring them to complete takeoff and landing within a very short distance. This places extremely high demands on the lift of the airfoil under low-speed conditions. Furthermore, once in cruise mode, to ensure sufficient endurance and range, the airfoil must possess excellent high-subsonic cruise efficiency, i.e., a high lift-to-drag ratio. These two design requirements, corresponding to low-speed and high-speed states respectively, present a fundamental design contradiction at the physical level, often resulting in significant performance compromises when conventional airfoils are directly applied to carrier-based UAVs.

[0003] This contradiction is concentrated in the flow field characteristics around the airfoil. During takeoff and landing, the airfoil is usually at a high angle of attack. The key to ensuring its aerodynamic performance lies in maintaining the attached flow of the boundary layer and delaying flow separation as much as possible to obtain a higher maximum lift coefficient. At this time, a larger leading-edge radius and maximum camber are beneficial for maintaining leading-edge suction and establishing a stable leading-edge vortex system, thereby increasing the stall angle of attack. When entering the high subsonic cruise state, the design requirement shifts from increasing lift to suppressing drag, that is, pursuing a higher cruise lift-to-drag ratio. However, the large leading-edge radius and upper surface camber that perform well at low speeds will intensify the acceleration of the airflow on the airfoil surface, which can easily form a local transonic or supersonic region in the middle and rear of the airfoil and induce strong shock waves. These shock waves not only cause a sharp increase in wave drag, but also cause the shock wave and boundary layer to interfere with each other, resulting in flow separation and significantly deteriorating the cruise lift-to-drag ratio and pitching moment characteristics.

[0004] Therefore, while ensuring normal low-speed take-off and landing, the airfoil of shipborne UAVs must also take into account high-speed cruising performance, which places extremely high demands on its airfoil design. Summary of the Invention

[0005] The purpose of this invention is to provide a high-lift, low-drag airfoil, wing, and aircraft. To address the problems existing in the prior art and improve the aerodynamic characteristics of large fixed-wing shipborne UAVs under high and low speed conditions, this application proposes a high-lift, low-drag airfoil suitable for large fixed-wing shipborne UAVs that balances high and low speed characteristics through a high-dimensional multi-objective airfoil optimization design method. This airfoil improves its low-speed lift characteristics while also possessing a high lift-to-drag ratio under high subsonic cruise conditions.

[0006] To achieve the above objectives, the present invention provides a high-lift, low-drag airfoil. The leading-edge radius of the high-lift, low-drag airfoil is 0.02474±1%, the maximum thickness is 0.15096±1%, located at 27.7% to 29.7% of the chord length of the high-lift, low-drag airfoil, and the maximum camber is 0.018421±1%, located at 26.3% to 28.3% of the chord length of the high-lift, low-drag airfoil. The leading-edge radius, maximum thickness, and maximum camber are all described using dimensionless quantities, with the dimensionless process based on the airfoil chord length c.

[0007] The geometric coordinate expressions for the upper and lower surfaces of the airfoil are:

[0008] ;

[0009] in, This represents the x-coordinate of the upper or lower surface of the airfoil. This represents the ordinate corresponding to the upper or lower surface of the airfoil. Represents the order of the CST parameterization method. The y-coordinate represents the step at the root of the airfoil;

[0010] The fitting coefficient for the upper surface of the airfoil is:

[0011] ,

[0012] The fitting coefficient for the lower surface of the airfoil is:

[0013] .

[0014] Preferably, the leading edge radius of the high lift and low drag airfoil is 0.02474, the maximum thickness is 0.15096, located at 28.7% of the chord length of the high lift and low drag airfoil, and the maximum camber is 0.018421, located at 27.3% of the chord length of the high lift and low drag airfoil.

[0015] Preferably, the fitting coefficient for the upper surface of the airfoil is:

[0016] ,

[0017] The fitting coefficient for the lower surface of the airfoil is:

[0018] .

[0019] Preferably, the coordinates of the upper and lower surfaces of the high-lift, low-drag airfoil are as follows:

[0020] Top surface coordinates:

[0021]

[0022] Lower surface coordinates:

[0023] .

[0024] Preferably, the area of ​​the high lift and low drag airfoil is 0.09663±1%.

[0025] Preferably, the area of ​​the high lift and low drag airfoil is 0.09663.

[0026] The preferred design point operating condition for a high-lift, low-drag airfoil is:

[0027] .

[0028] This application also provides an airfoil, calculated based on the above-mentioned high lift and low drag airfoil.

[0029] This application also provides an aircraft including the aforementioned wing.

[0030] Preferably, the aircraft is a fixed-wing unmanned aerial vehicle (UAV).

[0031] Compared with the above-mentioned background technology, the high lift and low drag airfoil provided by the present invention has the following beneficial effects:

[0032] This application's high-lift, low-drag airfoil improves its lift-to-drag ratio at high subsonic speeds while also possessing high-lift characteristics at low speeds. A high-dimensional multi-objective airfoil optimization design method was used to optimize a 15% thickness baseline airfoil. The aerodynamic performance of the designed airfoil was compared with the baseline airfoil at high subsonic speeds and low Mach numbers. The results show that, compared to the classic airfoil, the high-lift, low-drag airfoil of this application significantly increases the lift coefficient at the same angle of attack, with the lift coefficient at the low-speed design point increasing from 1.0779 to 1.2262, resulting in a significant improvement in low-speed characteristics. The lift coefficient at high subsonic speeds is also significantly improved, with the lift-to-drag ratio at the high-speed design point increasing from 61 to approximately 66. Furthermore, the improvement in lift-to-drag ratio is even more significant at higher lift coefficients. Considering the special requirements of large fixed-wing shipborne UAVs, the designed airfoil demonstrates a significant advantage over the baseline airfoil. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0034] Figure 1 The airfoil geometry diagram provided for embodiments of the present invention;

[0035] Figure 2 A comparison diagram of the airfoil geometry and the reference airfoil geometry provided for embodiments of the present invention;

[0036] Figure 3 A comparison diagram of the low-speed lift characteristics of an airfoil provided for an embodiment of the present invention and a reference airfoil (Ma=0.15, Re=3.5e6).

[0037] Figure 4 A comparison diagram of the airfoil geometry provided for an embodiment of the present invention and the low-speed lift-drag characteristics of a reference airfoil (Ma=0.15, Re=3.5e6).

[0038] Figure 5 A comparison diagram of the high-speed lift characteristics of an airfoil provided for an embodiment of the present invention and a reference airfoil (Ma=0.5, Re=4.25e6).

[0039] Figure 6 A comparison diagram of the high-speed lift and drag characteristics of an airfoil provided for an embodiment of the present invention and a reference airfoil (Ma=0.5, Re=4.25e6). Detailed Implementation

[0040] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0041] To enable those skilled in the art to better understand the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0042] This application focuses on the aerodynamic problems and design objectives faced by carrier-based airfoils, and proposes a high-lift, low-drag airfoil suitable for large fixed-wing carrier-based UAVs by using a multi-objective optimization design method.

[0043] The airfoil design requires a high lift-to-drag ratio at high subsonic speeds, high lift at low speeds, and torque characteristics across all conditions. Therefore, based on these requirements, the design model is a typical high-dimensional, multi-objective, complex constrained optimization problem, making it difficult for general multi-objective optimization algorithms to obtain an effective solution set. Thus, we optimize by reducing the mean and variance of airfoil drag at high speeds, aiming to achieve an extremely high cruise lift-to-drag ratio while maintaining torque characteristics. Simultaneously, we optimize the lift coefficient for low-speed, constant angle-of-attack takeoff and landing. Through multiple rounds of optimization using a multi-objective optimization algorithm, we select an aerodynamic shape that balances torque coefficients at both high and low Mach speeds.

[0044] The lift-drag aerodynamic characteristics of the optimized airfoil were analyzed under various operating conditions, with Mach numbers of 0.15 and 0.5, corresponding to Reynolds numbers of 3.5e6 and 4.25e6. The results show that the airfoil meets the design requirements well while satisfying the constraints.

[0045] Please refer to the appendix for the high lift and low drag airfoil provided in this application. Figure 1 To be continued Figure 6 As shown, the leading edge radius is 0.02474±1%, the maximum thickness is 0.15096±1%, located at 27.7% to 29.7% of the chord length of the high lift and low drag airfoil, and the maximum camber is 0.018421±1%, located at 26.3% to 28.3% of the chord length of the high lift and low drag airfoil. The leading edge radius, maximum thickness, and maximum camber are all described using dimensionless quantities, and the dimensionless process is based on the airfoil chord length c.

[0046] The geometric coordinate expressions for the upper and lower surfaces of the airfoil are:

[0047] ;

[0048] in, This represents the x-coordinate of the upper or lower surface of the airfoil. This represents the ordinate corresponding to the upper or lower surface of the airfoil. Represents the order of the CST parameterization method. The y-coordinate represents the step at the root of the airfoil.

[0049] In airfoil design, parameters such as leading-edge radius, maximum thickness, and maximum camber are typically expressed as dimensionless quantities, with units equal to multiples of the chord length (c). For example, the leading-edge radius of 0.02474 in this paper indicates that the airfoil's leading-edge radius is 2.474% of the chord length. For instance, if the airfoil's chord length is 1 meter, then the leading-edge radius is 0.02474 meters (i.e., 24.74 millimeters). This dimensionless description is standard practice in airfoil design, facilitating comparison and scaling of airfoils of different sizes.

[0050] Regarding the optimization model, the design requirements are a high lift-to-drag ratio and low torque coefficient at high subsonic speeds, and a large maximum lift coefficient and low torque coefficient at low speeds. The constraints focus on optimizing the lift-to-drag ratio and torque characteristics.

[0051] Table 1. Operating Conditions for High-Lift, Low-Drag Airfoils Design Points

[0052]

[0053] Search scope , Design goals and constraints.

[0054] Table 2 Design Objectives and Constraints for Low Subsonic High-Lift Low-Drag Rotor Airfoils

[0055]

[0056] Regarding optimizing airfoil data, such as Figure 2 As shown in the comparison between the geometric shape diagram of the airfoil of the present invention and the geometric shape diagram of the reference airfoil, the airfoil of the present invention has a larger upper surface curvature, a slightly smaller leading edge radius, and an increased slope of the leading edge change; the maximum thickness is slightly moved to the rear, and a reverse curvature appears at the trailing edge of the upper surface.

[0057] The high-lift, low-drag airfoil suitable for large fixed-wing shipborne UAVs in this embodiment has the following airfoil characteristics:

[0058]

[0059] Furthermore, the airfoil features are preferred:

[0060]

[0061] The upper and lower surfaces of the airfoil in this invention are constructed using the CST parametric method. This method uses class functions to define geometric configuration categories and shape functions to modify the specific geometric shape. Its general analytical expression is as follows:

[0062] ;

[0063] In a rectangular coordinate system, let x be the normalized coordinate along the chord length ( (y is a normalized coordinate perpendicular to the chord length), then the unified expression for the upper and lower surfaces of the airfoil of this invention is specifically as follows:

[0064] ;

[0065] Among them, class functions The basic characteristics of an airfoil used to define its rounded leading edge and pointed trailing edge are expressed as follows:

[0066] ;

[0067] The shape function is linearly combined using 11th-order Bernstein polynomials as basis functions, and its expression is:

[0068] ;

[0069] in, These are the undetermined weighting coefficients (i.e., fitting coefficients). The coefficients are binomial coefficients. The y-coordinate represents the step at the root of the airfoil.

[0070] Furthermore, the unified expressions obtained by fitting the upper and lower surfaces of the airfoil of the present invention using n-order (n=11) CST parameterization are as follows:

[0071]

[0072] in, This represents the x-coordinate of the upper or lower surface of the airfoil. This represents the ordinate corresponding to the upper or lower surface of the airfoil. Represents the order of the CST parameterization method. The y-coordinate represents the step at the root of the airfoil;

[0073] The fitting coefficient for the upper surface of the airfoil is:

[0074]

[0075] The fitting coefficient for the lower surface of the airfoil is:

[0076] .

[0077] Top surface coordinates:

[0078]

[0079] Lower surface coordinates:

[0080]

[0081] Regarding the comparison of aerodynamic data, such as Figure 3 The diagram shows a comparison of the low-speed lift characteristics of the airfoil geometry of this invention with those of a reference airfoil. Figure 4 The diagram shows a comparison of the low-speed lift and drag characteristics of the airfoil geometry of this invention with those of a reference airfoil. Figure 5 The diagram shows a comparison of the high-speed lift characteristics of the airfoil geometry of this invention with those of a reference airfoil. Figure 6The diagram showing the airfoil geometry of this invention, compared with the high-speed lift-drag characteristics of a reference airfoil, reveals that the designed airfoil exhibits a significantly increased lift coefficient at the same angle of attack. The lift coefficient at the low-speed design point increases from 1.0779 to 1.2262, resulting in a significant improvement in low-speed performance. The lift coefficient at high subsonic speeds is also significantly improved, with the lift-drag ratio at the high-speed design point increasing from 61 to approximately 66. Furthermore, the improvement in lift-drag ratio is even more pronounced at higher lift coefficients. Simultaneously, compared to the reference airfoil, the moment coefficient at the low-speed design point decreases from 0.007721 to -0.007107, and the moment coefficient at the high-speed design point decreases from 0.013694 to -0.003989. This is because, compared with the baseline airfoil, the optimized airfoil has a smaller leading edge radius, and the maximum thickness and maximum camber position are slightly shifted to the rear. This causes the position where the airflow accelerates most violently on the upper surface to shift to the rear, reducing the flow separation area. In addition, compared with the initial airfoil, the trailing edge of the optimized airfoil exhibits a reverse camber at the trailing edge of the upper surface, showing a certain anti-loading characteristic, which provides a certain pitching moment and reduces the absolute value of the moment.

[0082] Based on the above analysis, the high-lift, low-drag airfoil proposed in this invention is suitable for large fixed-wing shipborne UAVs, balancing high lift-drag ratio during cruise and high lift and low torque characteristics at low speeds. It meets the unique aerodynamic design requirements of shipborne UAVs.

[0083] This application also provides an airfoil, which is calculated based on the high lift and low drag airfoil described above. Of course, the high lift and low drag airfoil described above is only the "outline" of a certain section of the airfoil along the span, which is used as input for aerodynamic calculations, wind tunnel tests or three-dimensional airfoil design. Obviously, the span here refers to the "elongation" direction of the airfoil from the root to the tip, also called the span direction.

[0084] To obtain the wing (a three-dimensional solid), additional parameters are needed to complete the 3D modeling. These parameters include, for example, wingspan, tip-to-root ratio, sweep angle, twist angle distribution, and angle of attack or geometric angle of attack distribution. For specific calculation methods of obtaining the wing from a high-lift, low-drag airfoil, refer to relevant technologies such as wing lofting or surface sweeping; these will not be elaborated upon here. Furthermore, the selection of relevant parameters can be determined according to actual needs, and this paper does not impose specific limitations on this.

[0085] This application also provides an aircraft, including the wings described above. Other related components of the aircraft can be found in related technologies and will not be described in detail here.

[0086] The aircraft can be specifically a fixed-wing UAV. A fixed-wing UAV is an unmanned aerial vehicle that generates lift by using a fixed wing, generates thrust by using a propulsion device (propeller, jet, etc.), and controls its attitude and trajectory by using control surfaces (ailerons, elevators, rudders, etc.). By using the wings described above, fixed-wing UAVs can achieve the above-mentioned technical effects.

[0087] Of course, the wing calculated by the high lift and low drag airfoil in this article can also be used on large fixed-wing UAVs. For large fixed-wing UAVs, the industry's common classification standard usually classifies fixed-wing UAVs with a maximum takeoff weight of 600 kg or more as "large". In addition, in other classification standards, the wingspan size is also specified. That is, large fixed-wing UAVs usually refer to fixed-wing UAVs with a maximum takeoff weight of not less than 600 kg and a wingspan of generally more than 9 meters.

[0088] It should be noted that in this specification, relational terms such as first and second are used only to distinguish one entity from several other entities, and do not necessarily require or imply any such actual relationship or order between these entities.

[0089] This article uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of the present invention. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the present invention, and these improvements and modifications also fall within the protection scope of the present invention.

Claims

1. A high-lift, low-drag airfoil, characterized in that, The high-lift, low-drag airfoil has a leading-edge radius of 0.02474±1% and a maximum thickness of 0.15096±1%, with the maximum thickness located at 27.7% to 29.7% of the chord length. The high-lift, low-drag airfoil also has a maximum camber of 0.018421±1%, located at 26.3% to 28.3% of the chord length. The leading-edge radius, maximum thickness, and maximum camber are all described using dimensionless quantities, with the dimensionless process based on the airfoil chord length c. The geometric coordinate expressions for the upper and lower surfaces of the airfoil are: ； in, This represents the x-coordinate of the upper or lower surface of the airfoil. This represents the ordinate corresponding to the upper or lower surface of the airfoil. Represents the order of the CST parameterization method. The y-coordinate represents the step at the root of the airfoil; The fitting coefficient for the upper surface of the airfoil is: ， The fitting coefficient for the lower surface of the airfoil is: 。 2. The high-lift, low-drag airfoil according to claim 1, characterized in that, The high lift and low drag airfoil has a leading edge radius of 0.02474, a maximum thickness of 0.15096, located at 28.7% of the chord length, and a maximum camber of 0.018421, located at 27.3% of the chord length.

3. The high-lift, low-drag airfoil according to claim 2, characterized in that, The fitting coefficient for the upper surface of the airfoil is: ， The fitting coefficient for the lower surface of the airfoil is: 。 4. The high-lift, low-drag airfoil according to claim 2, characterized in that, The coordinates of the upper and lower surfaces of the high-lift, low-drag airfoil are as follows: Top surface coordinates: Lower surface coordinates: 。 5. The high lift, low drag airfoil according to any one of claims 1-4, characterized in that, The area of ​​the high lift and low drag airfoil is 0.09663±1%.

6. The high-lift, low-drag airfoil according to claim 5, characterized in that, The area of ​​the high-lift, low-drag airfoil is 0.09663.

7. The high-lift, low-drag airfoil according to any one of claims 1-4, characterized in that, The design point operating condition for the high-lift, low-drag airfoil is: 。 8. A wing, characterized in that, The calculation was performed based on the high lift and low drag airfoil described in any one of claims 1-7.

9. An aircraft, characterized in that, Includes the wing described in claim 8 above.

10. The aircraft according to claim 9, characterized in that, The aircraft in question is a fixed-wing unmanned aerial vehicle (UAV).

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