A wing lift-to-drag ratio adjustment device and method

Abstract

This application discloses a wing lift-to-drag ratio adjustment device and method, belonging to the field of aircraft aerodynamics design. At least two airflow passing elements are symmetrically arranged on the lower surfaces of the left and right wings of the aircraft, and can switch between a retracted state and an operational state. In the operational state, the airflow passing elements at least partially protrude from the lower wing surface, with at least the surface facing the leading edge being arc-shaped, and their cross-sectional area decreasing along the protrusion direction. This accelerates the local airflow, reduces static pressure, thereby reducing lift, while simultaneously generating form drag to increase overall aircraft drag. A drive mechanism is used to switch the state of the airflow passing elements in response to control commands; a controller is used to generate and send control commands. This application also provides a corresponding adjustment method. This application has a simple structure, low cost, and can flexibly adjust the lift-to-drag ratio according to the landing environment, with minimal impact on the aircraft's pitch moment, making it particularly suitable for long-endurance aircraft without flaps.

Description

Technical Field

[0001] This application relates to the field of aircraft aerodynamic design technology, and in particular to a wing lift-to-drag ratio adjustment device and method. Background Technology

[0002] During the glide path of an aircraft, the engine usually needs to be at idle. At this time, it is desirable for the aircraft to have aerodynamic characteristics of high lift and high drag (i.e., low lift-to-drag ratio) in order to obtain a large glide angle, thereby shortening the horizontal distance of the glide flight and ensuring a safe landing within the limited runway length.

[0003] In existing technologies, landing flaps are mainly used to achieve this purpose. However, for long-endurance aircraft, flap systems are usually not designed due to cost and structural weight considerations. Even if flaps are designed, they have the following drawbacks: the performance of flaps is usually optimized for a specific design point, and their adaptability is insufficient when the landing environment (such as airport altitude, runway length, and weather conditions) changes, making it impossible to flexibly adjust the lift-to-drag ratio to adapt to various landing scenarios.

[0004] Therefore, for aircraft without flaps or requiring enhanced landing performance, how to provide a simple, low-cost lift-to-drag reduction device that can flexibly adjust the lift-to-drag ratio according to the landing environment is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] This application provides a wing lift-to-drag ratio adjustment device and method, which solves the technical problems mentioned in the background art.

[0006] In a first aspect, embodiments of this application provide a wing lift-to-drag ratio adjustment device, comprising: At least two airflow passing elements are symmetrically arranged on the lower wing surfaces of the left and right wings of the aircraft. Each airflow passing element is configured to switch between a retracted state and an operational state. In the operational state, the airflow passing element at least partially protrudes from the lower wing surface, and its surface facing at least the leading edge is arcuate, and its cross-sectional area decreases along the protrusion direction. A drive mechanism, connected to the airflow passing component, is used to drive the airflow passing component to switch between the storage state and the working state in response to a control command; The controller, electrically connected to the drive mechanism, is used to send the control commands.

[0007] In conjunction with the first aspect, in one possible implementation, the shape of the airflow passage component protruding from the lower wing surface in the working state is at least one of a spherical cap and an ellipsoidal cap.

[0008] In conjunction with the first aspect, in one possible implementation, the longitudinal mounting position of each of the airflow passing components is consistent with or within a predetermined allowable deviation range of the longitudinal position of the aircraft's center of gravity.

[0009] In conjunction with the first aspect, in one possible implementation, the center-to-center distance between two adjacent airflow passages in the spanwise direction is not less than three times the maximum lateral dimension of a single airflow passage.

[0010] In conjunction with the first aspect, in one possible implementation, the airflow overpass is installed in a region extending from the wing-body junction to a distance of at least d from the inner end of the aileron, where d is the maximum lateral dimension of the airflow overpass.

[0011] In conjunction with the first aspect, in one possible implementation, the convex surface of the airflow-through component is a spherical cap, and its radius is configured such that, within the range of the aircraft's landing angle of attack, the increase in the overall lift coefficient ΔC caused by adding the airflow-through component is [value missing]. L and the overall drag coefficient increment ΔC D All conditions meet the preset constraints.

[0012] In conjunction with the first aspect, in one possible implementation, the controller is configured to determine the number of airflow components that need to be switched to the working state based on the target glide angle or target lift-to-drag ratio required for the aircraft landing state and a pre-stored aerodynamic effect model of the airflow components, and generate corresponding control commands, wherein the airflow components switched to the working state are symmetrically distributed in pairs on the left and right wings.

[0013] Secondly, embodiments of this application provide a wing lift-to-drag ratio adjustment method for controlling the wing lift-to-drag ratio adjustment device described in the first aspect or any possible implementation of the first aspect, comprising the following steps: Determine the target glide angle or target lift-to-drag ratio required by the aircraft during the landing phase; Based on the pre-stored aerodynamic effect model of the airflow passing components, the number and layout scheme of the airflow passing components that match the target glide slope angle or target lift-to-drag ratio are determined, wherein the extended airflow passing components are symmetrically distributed in pairs on the left and right wings. The control drive mechanism switches the corresponding number and layout of airflow components to the working state.

[0014] In conjunction with the second aspect, in one possible implementation, the wing lift-to-drag ratio adjustment method further includes a database construction step: Based on the wing parameters of the aircraft and the aerodynamic data of individual airflow components, the increments of the lift coefficient, drag coefficient, and pitch moment coefficient of the entire aircraft under different landing angles of attack by combinations of different numbers and symmetrical layouts of airflow components are calculated, forming the aerodynamic effect model of the airflow components.

[0015] In conjunction with the second aspect, in one possible implementation, the step of determining the number of airflow through the protruding component includes: The maximum usable glide angle is determined based on the aircraft's maximum permissible landing load. and the corresponding minimum lift-to-drag ratio ; Calculate the overall lift-to-drag ratio satisfy ≥ The minimum number of pairs, n, where n represents the number of airflow pairs arranged on each of the left and right wings. The safety factor is greater than 1.

[0016] One or more technical solutions provided in the embodiments of this application have at least the following technical effects: The wing lift-to-drag ratio adjustment device provided in this application embodiment symmetrically arranges retractable airflow passage components on the lower wing surface. The drive mechanism switches the required number of airflow passage components to the working state, so that at least part of them protrude from the lower wing surface. On the one hand, the design of the surface facing the leading edge being arc-shaped and the cross-sectional area decreasing along the protrusion direction is beneficial to utilizing the principle of local airflow acceleration and static pressure reduction to form a low-pressure area on the lower wing surface to actively reduce lift. On the other hand, the device itself increases the overall drag by increasing the drag of the aircraft. Thus, without the need for flaps or to compensate for the limitations of flap performance, the lift-to-drag ratio can be flexibly and on demand adjusted, enabling the aircraft to obtain a larger glide angle, significantly shortening the horizontal distance of glide flight, and ensuring safe and reliable landing within a limited runway length in different landing environments. Moreover, the structure is simple, the cost is low, and it is easy to integrate and apply to long-endurance aircraft. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments of this application will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the aircraft landing process provided in an embodiment of this application; Figure 2 This is a schematic diagram showing the position of the airflow passage component on the lower surface of the wing, as provided in the embodiments of this application. Figure 3 This is a schematic diagram showing the spacing and numbering of airflow components provided in the embodiments of this application; Figure 4 Pitch moment curve provided for embodiments of this application; Figure 5 The lift coefficient / lift-to-drag ratio curves provided in the embodiments of this application; Figure 6 Pressure diagram of the core influence area of ​​the airflow through the component provided in the embodiments of this application; Figure 7 This is a schematic diagram of the structure of the airflow passage component facing the leading edge in an embodiment of this application.

[0019] Icon: 1 - Airflow through component. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] In the description of the embodiments of this application, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing the embodiments of this application and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. The terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance. Furthermore, the terms "installed," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this application according to the specific circumstances.

[0022] This application provides a wing lift-to-drag ratio adjustment device, such as... Figures 1 to 7 As shown. The wing lift-to-drag ratio adjustment device includes at least two airflow passing components 1, a drive mechanism, and a controller.

[0023] At least two airflow overlays 1 are symmetrically arranged on the lower surfaces of the left and right wings of the aircraft. Each airflow overlay 1 is configured to switch between a retracted state and an operational state: in the retracted state, the airflow overlay 1 is completely retracted into the lower surface of the wing and does not protrude from the wing surface to avoid increasing drag and reducing lift during cruise flight; in the operational state, the airflow overlay 1 at least partially protrudes from the lower surface, with its surface facing at least the leading edge being curved, and its cross-sectional area decreasing along the protrusion direction. According to Bernoulli's theorem, this causes the local airflow velocity across the surface of the airflow overlay 1 to increase, dynamic pressure to increase, and static pressure to decrease, thereby creating a local low-pressure area on the lower surface of the wing to reduce lift. At the same time, the airflow overlay 1 itself generates form drag, thereby increasing the overall drag of the aircraft, achieving the goals of reducing lift, increasing drag, reducing lift-to-drag ratio, and increasing glide angle. The curved shape of the airflow overlay 1 can be determined according to the lift-to-drag ratio required for aircraft landing, such as... Figure 7 As shown.

[0024] In this application, "leading edge direction" refers to the direction toward the leading edge of the wing, that is, the direction toward the nose of the aircraft.

[0025] In existing technologies, lift-to-drag ratio adjustment is typically achieved through spoiler design. Spoilers are usually located on the upper wing surface and deflect upwards when needed. When the deflection angle is small, the reduction in lift is minimal, and the drag-increasing efficiency is limited. Only when the deflection angle is large can a significant lift reduction and drag increase effect be achieved. If the spoiler is placed on the lower wing surface, the spoiler deflects downwards, increasing the wing camber and lift, but drag also increases accordingly. However, this does not achieve efficient lift reduction and drag increase, thus failing to reduce the lift-to-drag ratio. Furthermore, placing the spoiler on either the upper or lower wing surface affects the pitching moment, introducing additional trim requirements. Both solutions require large servos and strong linkage mechanisms to achieve a significant reduction in lift-to-drag ratio. The airflow component 1 in this application effectively reduces the lift-to-drag ratio while avoiding the impact on the pitching moment and eliminating additional trim requirements.

[0026] The drive mechanism is connected to the airflow passage component 1 and is used to drive the airflow passage component 1 to switch between a retracted state and an operating state in response to control commands. The drive mechanism can be a miniature electric actuator, a rotary electromagnet, or a pneumatic or hydraulic drive.

[0027] In this embodiment, the drive mechanism is powered by the aircraft's main power system. Specifically, the drive mechanism draws power from the aircraft's existing DC power supply bus (depending on the aircraft model), and voltage conversion and current protection are performed by the power management module inside the controller. In the aircraft's engine idle state or emergency power supply mode, the drive mechanism can still be powered by the aircraft's battery or backup power system to ensure the reliable execution of the lift-to-drag ratio adjustment function during landing.

[0028] The controller is electrically connected to the drive mechanism and is used to send control commands. The controller is part of the flight management computer and has a pre-stored aerodynamic effect model of the airflow through component 1.

[0029] In this embodiment, the longitudinal installation position of each airflow component 1 is consistent with or within a predetermined allowable deviation range (e.g., ±5mm) of the longitudinal position of the aircraft's center of gravity. This ensures that the additional aerodynamic force generated by the airflow component 1 during operation does not significantly alter the aircraft's pitch moment, thus avoiding additional trim requirements for the elevator and ensuring the stability of the landing attitude.

[0030] In the embodiments of this application, such as Figure 3 and Figure 6 As shown, the center-to-center distance between two adjacent airflow passage components 1 in the spanwise direction is not less than three times the maximum lateral dimension of a single airflow passage component 1. This effectively avoids the superposition effect of aerodynamic interference between airflow passage components 1, ensuring that each airflow passage component 1 can independently and efficiently generate the expected lift loss and drag gain, thereby simplifying the aerodynamic evaluation and CFD calculation iteration process.

[0031] like Figure 6 As shown in the figure, the static pressure cloud map of the upper and lower wing surfaces after the airflow through component 1 is activated shows that the pressure gradually increases from blue to yellow. The light green area is where the pressure of the device is the same as that of the wing surface. It can be seen from the figure that the pressure influence area of ​​the airflow through component 1 is within a 3d range centered on the device.

[0032] In the embodiments of this application, such as Figure 2 As shown, the airflow pass-through component 1 is installed in an area extending from the wing-body junction to a distance of at least d from the inner end of the aileron, where d is the maximum lateral dimension of the airflow pass-through component 1. This installation area makes full use of the effective space in the wing spanwise direction while avoiding interference with the aileron control efficiency, ensuring the stability and safety of lateral control, and is particularly suitable for long-endurance aircraft with a high aspect ratio.

[0033] In one embodiment of this application, the convex surface of the airflow over-part 1 is a spherical cap, and its radius is configured such that, within the range of the aircraft's landing angle of attack, the increase in the overall lift coefficient ΔC caused by the addition of the airflow over-part 1 is [value missing]. L and the overall drag coefficient increment ΔC D All conditions are satisfied by the preset constraints. In one embodiment of this application, the preset constraints are specifically: the increase in the overall lift coefficient ΔC. L ≤-0.01, and the overall drag coefficient increment ΔC D ≥0.001.

[0034] It should be noted that this application does not limit the overall lift coefficient increment ΔC. L and the overall drag coefficient increment ΔC DThe specific range can be adjusted by the user based on experience or the specific device model or application environment. Determining this radius involves the following three steps: Step 1: Determine the range of landing angle of attack values Based on the aerodynamic characteristics and landing performance requirements of the aircraft type, the range of actual landing angles of attack during the approach and glide phase is determined. For example, this can be determined based on the aircraft's stall speed V. stall The landing descent velocity V = 1.3V stall And by taking advantage of the equilibrium condition that lift equals gravity, the landing lift coefficient can be deduced, and then the corresponding landing angle of attack can be obtained by interpolation from the original aerodynamic data table of the aircraft.

[0035] Step 2: Obtain the aerodynamic coefficient of the device Within this landing angle range, the airflow passes through the pre-stored aerodynamic data table of component 1 (such as the lift coefficient C at different landing angles). LH and drag coefficient C DH Select the corresponding value from the range. To ensure that the device can still meet the constraints under the most severe conditions, the value that minimizes the increase in the lift coefficient (i.e., C) within the landing angle of attack range is usually chosen. LH The landing angle of attack with the most negative result and the most conservative increase in drag coefficient, or directly taking the C value corresponding to the landing angle of attack. LH and C DH .

[0036] Step 3: Solve for the radius based on the constraints. Establish the effect of a single airflow passage component 1 (a pair symmetrically arranged on the left and right wings) on the overall lift coefficient increment ΔC of the aircraft. L_single and drag coefficient increment ΔC D_single Contribution expression: ΔC L_single = ΔC D_single = ; in, The reference projected area of ​​a single airflow passing through component 1 (for a hemisphere, take...). =0.5×π×r²), where S is the wing area of ​​the aircraft. Substituting the above expressions into the preset constraints: ≤-0.01, ≥0.001; Solve inversely to obtain the first radius r that satisfies the lift constraint. L and the second radius r that satisfies the resistance constraint DThe larger of the two values ​​is taken as the radius. For ease of engineering and manufacturing, the integer closest to the larger of the two values ​​is generally used as the radius (e.g., rounded to the nearest millimeter or centimeter), while ensuring that the airflow over component 1 does not exceed the leading edge of the wing during operation.

[0037] The radius determined by the above method can ensure that each airflow component 1 independently generates a clear and sufficient lift reduction and drag increase effect within the actual landing angle of attack range of the aircraft, laying a reliable individual aerodynamic data foundation for subsequent precise adjustment of the overall lift-to-drag ratio by selectively activating different numbers of devices.

[0038] In this embodiment of the application, the controller is configured to determine the number of airflow passing components 1 that need to be switched to the working state based on the target glide angle or target lift-to-drag ratio required for the landing state of the aircraft and the pre-stored aerodynamic effect model of the airflow passing components 1, and generate corresponding control commands. The airflow passing components 1 switched to the working state are symmetrically distributed in pairs on the left and right wings.

[0039] This application also provides a method for adjusting the lift-to-drag ratio using the above-described device, comprising the following steps: S1: Determine the target glide angle or target lift-to-drag ratio required for the aircraft during the landing phase.

[0040] like Figure 1 As shown, during the approach level flight phase, the onboard navigation system obtains the current airport's runway length and the aircraft's altitude (h) for the approach glide flight. obst And meteorological conditions (such as wind speed, temperature, air pressure, altitude, etc.). The controller is based on the formula s1=h obst / tanγ (where s1 is the available horizontal glide distance) is used to inversely calculate the required glide angle γ. target Then by γ target =arctan(1 / K target Calculate the corresponding target lift-to-drag ratio K target If the airport runway is short, a larger γ is required. target (i.e., the smaller K) target ).

[0041] S2: Based on the pre-stored aerodynamic effect model of airflow passing component 1, determine the number and layout scheme of airflow passing component 1 that match the target glide slope angle or target lift-to-drag ratio, wherein the extended airflow passing components 1 are symmetrically distributed in pairs on the left and right wings. The controller calls up pre-stored aerodynamic effect models (see Tables 2 to 7 and...). Figure 5 (Lift coefficient / lift-to-drag ratio curve), find the overall lift-to-drag ratio that satisfies "after activating airflow through component 1". ≤K targetThe minimum number of airflow components is selected based on the combination of 1. To ensure safety, the actual selection usually takes the following value. Slightly less than K target (i.e., the actual glide angle is slightly larger than the required glide angle). The airflow through component 1 must be used symmetrically in pairs on the left and right to ensure that it does not affect the lateral stability.

[0042] S3: Control the drive mechanism to switch the corresponding number and layout of airflow passing components 1 to the working state.

[0043] The controller sends a command to the drive mechanism to switch the selected airflow through component 1 from the storage state to the working state.

[0044] S4: After the grounding roll is completed or during the go-around, the controller sends a retraction command, and all airflow through component 1 returns to the retracted state to reduce subsequent flight drag.

[0045] It should be noted that the wing lift-to-drag ratio adjustment method provided in this application first determines the target glide angle or target lift-to-drag ratio required by the aircraft during the landing phase. Then, based on a pre-stored aerodynamic effect model of the airflow passing element 1, it quickly matches the optimal number of airflow passing elements 1 extended and the symmetrical layout scheme to meet the target. Finally, it controls the drive mechanism to switch the corresponding airflow passing elements 1 to the working state, forming a complete, closed-loop adaptive adjustment process. This method allows the aircraft to automatically calculate and accurately execute the required combination of airflow passing elements 1 under different runway lengths, airport altitudes, and weather conditions without relying on flaps or complex manual judgments. This ensures that the actual glide angle matches the target glide angle, thereby effectively shortening the landing roll distance and reducing the risk of runway overrun. At the same time, the mandatory requirement for the extended airflow passing elements 1 to be symmetrically distributed in pairs on the left and right wings fundamentally eliminates additional rolling and yaw moments, ensuring lateral stability and handling safety during landing. Compared to traditional methods that rely on experience or fixed configurations, this method significantly improves the automation, response speed, and reliability of lift-to-drag ratio adjustment during the landing phase. It is also easy to implement through software upgrades in existing flight management systems and has good engineering application value.

[0046] In this embodiment of the application, the wing lift-to-drag ratio adjustment method further includes a database construction step: Based on the wing parameters of the aircraft and the aerodynamic data of a single airflow passing component 1, the increments of the lift coefficient, drag coefficient and pitch moment coefficient of the entire aircraft under different landing angles of attack by different numbers and symmetrical layouts of airflow passing components 1 are calculated, thus forming the aerodynamic effect model of the airflow passing component 1.

[0047] In this embodiment of the application, the step of determining the number of extensions of the airflow passing through the component 1 includes: The maximum usable glide angle is determined based on the aircraft's maximum permissible landing load. and the corresponding minimum lift-to-drag ratio ; Calculate the overall lift-to-drag ratio satisfy ≥ The minimum number of pairs, n, where n represents the number of airflow passage pairs arranged on each of the left and right wings. The safety factor is greater than 1.

[0048] Specifically, this embodiment takes a certain type of flapless long-endurance aircraft as an example to explain in detail how to determine the radius and total number of airflow passing through component 1 based on the aircraft parameters.

[0049] The aircraft has a wing area of ​​S = 7.5㎡, a landing weight of W = 480kg (gravity), and a stall speed of V. stall= 29.065 m / s, landing glide velocity V = 1.3V stall =37.78 m / s (where V is the incoming flow velocity). The air density ρ is taken as the standard value.

[0050] (a) Raw aerodynamic data The original aerodynamic data of the aircraft are shown in Table 1.

[0051] Table 1 Raw aerodynamic data of a certain aircraft

[0052] From the lift formula L=½ρV²SC L (ρ is air density, S is wing area, C) L Given the lift coefficient (L = W) and the lift during landing equals the weight, the required lift coefficient C for landing is calculated. L =0.717245, corresponding to an interpolation value of approximately 6.66° for the landing angle of attack in Table 1.

[0053] (ii) Airflow data of component 1 The pre-stored aerodynamic data of the airflow through component 1 (hemispherical) are shown in Table 2.

[0054] Table 2 Lift / Drag Coefficients of Airflow Through Component 1 (Subsonic)

[0055] (III) Determining the radius Take C as the landing angle of attack of 6° around 6.66°. LH =-1.22949, C DH =0.295891. Substituting into the constraint inequality: 2×(-1.22949)×0.5πr² / 7.5≤-0.01→r≥0.1523m; 2×0.295891×0.5πr² / 7.5≥0.001→r≥0.0898m; The larger of the two values, r ≥ 0.1523m, is taken, and the integer closest to this larger value, 150mm, is used as the final radius. It has been verified that the device operates within this radius without extending beyond the leading edge of the wing.

[0056] (iv) Determination of the total number of airflow passing through component 1 Based on the maximum landing load of the landing gear (maximum vertical ground load F) N And the maximum compression), using the energy conservation equation, the maximum usable glide angle γ can be derived. max Calculations show that the aircraft's γ... max =5.16°, corresponding to the minimum lift-to-drag ratio K min =11.08. Taking a safety factor λ=1.1, the design target is the overall lift-to-drag ratio. ≥1.1×11.08=12.188.

[0057] Using the formula: , ; Where 2n is the total number of airflow passing through component 1, C LH C DH The values ​​for a landing angle of attack of 6° are taken from Table 2 (this angle of attack represents the most severe operating condition near the landing angle of attack). Calculations show that 2n ≤ 11.38, therefore 2n should be an even number not greater than 11.38. Initially, 2n = 10, i.e., n = 5 (5 on each wing). The lift coefficient, drag coefficient, and lift-drag ratio after adding 10 airflow passage components are then calculated and are shown in Table 3. The landing lift-drag ratio at this point is... The angle of attack is 13.43 (landing angle of attack 7.17°), which meets the requirements. Therefore, the total number of airflow passing through component 1 is selected as 10.

[0058] This application achieves a scientific and quantitative determination of the number of extended airflow components 1. This method uses the landing gear structure's load-bearing capacity as a safety boundary, ensuring that the vertical ground load during actual landing does not exceed the maximum allowable value, thus avoiding landing gear overload damage due to excessive glide angles. Simultaneously, by introducing a safety factor λ greater than 1, it fully considers the aerodynamic efficiency gain caused by flow interference between the airflow components 1 and the wing, as well as the uncertainties of the landing environment, providing a reliable engineering margin for selecting the number of airflow components 1. The resulting number of paired, symmetrically arranged airflow components 1 ensures both a safe landing of the aircraft with a sufficiently large glide angle within a limited runway length and that the landing gear always operates within a safe load range, achieving an optimal balance between lift reduction and drag increase effects and structural integrity, significantly improving the safety margin and design reliability of the landing process.

[0059] (v) Aerodynamic data after activating all airflow through component 1 Table 3 presents theoretical estimates of aerodynamic data at various landing angles of attack after activating all 10 airflow passage components 1. Based on these theoretical estimates, a preliminary assessment is made as to whether adding airflow passage component 1 can achieve the aerodynamic effects of reducing the lift coefficient, increasing the drag coefficient, and lowering the lift-to-drag ratio.

[0060] Table 3. Theoretical estimates of aerodynamic data for the entire machine plus 10 airflow passage components.

[0061] As can be seen, due to the activation of airflow component 1, the lift coefficient decreases, the landing angle of attack increases from 6.66° to 7.17°, and the lift-to-drag ratio decreases from 20.31 corresponding to 6.66° to 13.43 corresponding to 7.17°. The effect of reducing lift and increasing drag is significant, and it meets the requirements. Design requirement ≥12.188.

[0062] Example 2: Construction and Use of Aerodynamic Effect Model During the approach and glide of the aircraft in idle mode, the controller can send commands based on the landing environment (such as airport altitude, runway length, and weather conditions). To facilitate rapid online decision-making by the controller, an aerodynamic effect model of the airflow passage component 1 is pre-established through CFD calculations or wind tunnel tests. This model includes data on the overall lift coefficient, drag coefficient, and pitch moment coefficient of different combinations of airflow passage components 1 (activated in pairs numbered 1 to 5) at different landing angles of attack, as shown in Tables 4 to 7 below. In the tables, "1" indicates the use of airflow passage component 1 at position 1, "2" indicates the use of airflow passage component 1 at positions 1+2, and so on.

[0063] Table 4 Lift Coefficient Table

[0064]

[0065] Table 5 Drag Coefficient Table

[0066]

[0067] Table 6 - Pitch Moment Coefficient /

[0068]

[0069] Among them, Table 6 This represents the increment of the pitch moment coefficient.

[0070] Table 7 - Rise-to-Drag Ratio ( Table of Changes in the Number of Components 1 Used in Flow Processing with Airflow

[0071] The lift coefficient / lift-to-drag ratio curve obtained from the table above is as follows: Figure 5 As shown, the lift coefficient during descent can be determined by looking up a table or by linear interpolation. and rise-to-drag ratio A unique point can be determined in the curve. If the point is not on the curve, then a point on the curve with smaller lift drag under the same lift coefficient can be selected, and the airflow passage component 1 to be used can be determined.

[0072] During actual landing, the controller adjusts the target lift-to-drag ratio K accordingly. target Linear interpolation was performed on the data in Table 4 for landing angles of 6° and 8° to obtain the lift-to-drag ratios for each combination at a landing angle of 7.13°: the 1+2+3+4 combination was approximately 13.33, and the 1+2+3+4+5 combination was approximately 12.22. According to... ≤K target Choose combinations based on the principle.

[0073] For example, if K is calculated target =12.7, then 13.33>12.7 is not satisfied, therefore all 10 airflows are selected to flow through component 1. If K target If the value is less than 12.22, it means that even if all airflow is used through component 1, the requirements for a safe landing cannot be met. The controller may issue an alarm and suggest a go-around or an alternate landing.

[0074] Example 3: Pitch moment does not generate additional trim requirements By aligning the longitudinal center of each airflow pass-through component 1 with the aircraft's center of gravity, and arranging the airflow pass-through components 1 symmetrically in the spanwise direction, the change in pitch moment coefficient after activating different numbers of airflow pass-through components 1 was measured. See [link to relevant documentation]. Figure 4 (Pitch moment curve diagram) Based on the original pitch moment coefficient of the entire aircraft, after activating 1, 2, ..., 5 pairs of airflow over component 1, the change in pitch moment coefficient at each landing angle of attack is within ±0.02, which is much smaller than the moment change caused by conventional landing flaps (usually exceeding ±0.1). This indicates that this device hardly changes the longitudinal static balance of the aircraft during operation, eliminating the need for additional elevator deflection for trim, thereby reducing the burden on the flight control system and ensuring the stability of the landing attitude.

[0075] In this embodiment, the shape of the airflow passage component 1 protruding from the lower wing surface in the working state is at least one of a spherical cap and an ellipsoidal cap.

[0076] Furthermore, the spherical airflow passage component 1 in the above embodiments can be replaced by other convex curved surface structures such as ellipsoidal caps, as long as its aerodynamic characteristics meet the preset ΔC. L ≤-0.01、ΔC DA constraint of ≥0.001 is sufficient. The drive mechanism can also be pneumatic, hydraulic, or shape memory alloy driven. Furthermore, the number of airflow passing through component 1 is not limited to 10; it can be designed to be 4, 6, 8, or other multiples of 2, depending on the requirements of different models. The radius and total number still need to be recalculated according to the method described in this application. These alternative solutions all fall within the protection scope of this application.

[0077] This device can be manufactured through conventional machining, can be installed on the wings of aircraft, and can be reused.

[0078] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0079] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A wing lift-drag ratio adjustment device, characterized by, include: At least two airflow passing elements (1) are symmetrically arranged on the lower wing surfaces of the left and right wings of the aircraft. Each airflow passing element (1) is configured to switch between a retracted state and an operational state. In the operational state, the airflow passing element (1) at least partially protrudes from the lower wing surface, and the surface facing at least the leading edge is arcuate, and its cross-sectional area decreases along the protrusion direction. A drive mechanism, connected to the airflow passing component (1), is used to drive the airflow passing component (1) to switch between the storage state and the working state in response to a control command; The controller, electrically connected to the drive mechanism, is used to send the control commands.

2. The wing lift-drag ratio adjustment device of claim 1, wherein The airflow passing component (1) in the working state protrudes from the lower wing surface in the shape of at least one of a spherical cap and an ellipsoidal cap.

3. The wing lift-to-drag ratio adjustment device of claim 1, wherein, The longitudinal installation position of each of the airflow passing components (1) is consistent with the longitudinal position of the center of gravity of the aircraft or within a predetermined allowable deviation range.

4. The wing lift-to-drag ratio adjustment device of claim 1, wherein, The center-to-center distance between two adjacent airflow passage elements (1) in the span direction is not less than 3 times the maximum lateral dimension of a single airflow passage element (1).

5. The wing lift-to-drag ratio adjustment device of claim 1, wherein, The airflow passage element (1) is installed in the area from the wing-body junction to a distance of at least d from the inner end of the aileron, where d is the maximum lateral dimension of the airflow passage element (1).

6. The wing lift-to-drag ratio adjustment device according to claim 5, characterized in that, The convex curved surface of the airflow passing piece (1) is a spherical cap, and a radius of the spherical cap is configured to satisfy a preset constraint condition in a range of a landing angle of attack of the aircraft. L And a total machine drag coefficient increment ΔC D Both satisfy the preset constraint condition.

7. The wing lift-to-drag ratio adjustment device according to claim 1, characterized in that, The controller is configured to determine the number of airflow components (1) that need to be switched to the working state based on the target glide angle or target lift-to-drag ratio required for the aircraft landing state and the pre-stored aerodynamic effect model of the airflow components (1), and generate corresponding control commands, wherein the airflow components (1) switched to the working state are symmetrically distributed in pairs on the left and right wings.

8. A method for adjusting the lift-to-drag ratio of an airfoil, used to control the airfoil lift-to-drag ratio adjusting device according to any one of claims 1 to 7, characterized in that, Includes the following steps: Determine the target glide angle or target lift-to-drag ratio required by the aircraft during the landing phase; Based on the pre-stored aerodynamic effect model of the airflow passing component (1), the number and layout scheme of the airflow passing component (1) that match the target glide angle or target lift-to-drag ratio are determined, wherein the extended airflow passing components (1) are symmetrically distributed in pairs on the left and right wings. Control the drive mechanism to switch the corresponding number and layout of airflow passing parts (1) to the working state.

9. The wing lift-to-drag ratio adjustment method according to claim 8, characterized in that, It also includes the database creation step: Based on the wing parameters of the aircraft and the aerodynamic data of a single airflow component (1), the increments of the lift coefficient, drag coefficient and pitch moment coefficient of the whole aircraft under different landing angles of attack by combinations of different numbers and symmetrical layouts of airflow components (1) are calculated, thus forming the aerodynamic effect model of the airflow component (1).

10. The wing lift-to-drag ratio adjustment method according to claim 9, characterized in that, The steps for determining the number of extensions of the airflow through component (1) include: The maximum usable glide angle is determined based on the aircraft's maximum permissible landing load. and the corresponding minimum lift-to-drag ratio ; Calculate the overall lift-to-drag ratio satisfy ≥ The minimum number of pairs n, where n represents the number of airflow passage components (1) arranged on each of the left and right wings. The safety factor is greater than 1.

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