Flow control device

Abstract

The invention relates to a flow control device on a structural member such that strain in the structural member is at least partially transferred to the flow control device. The flow control device has at least two states or shapes separated by an elastic unstable region. The flow control device is arranged to rapidly transition or snap from a first state to a second state when strain in the structural member exceeds an activation threshold of the flow control device. In an example, a spoiler on an airfoil has a rest position in which the spoiler is substantially flush with a low pressure surface and an activated position in which the spoiler protrudes from the low pressure surface and changes the airflow over the surface. The spoiler flexes to move from the rest position to the activated position when strain in the airfoil exceeds a threshold. The deployed spoiler reduces lift on the airfoil, thereby reducing strain in the airfoil to which the spoiler is attached due to lift.

Description

Technical Field

[0001] The present invention relates to a flow control device arranged on a structural member, an aircraft wing or wingtip device including the flow control device, a method for controlling airflow above an airfoil, an airfoil having a spoiler, and a method for setting a spoiler on an aerodynamic surface. Background Technology

[0002] Various deformable or adaptive structural components are known that exhibit a wide range of shape changes in response to external stimuli while maintaining load-bearing capacity. Deformable structural components are particularly useful for flow control in aerodynamics. Of particular interest are deformable structural components that do not require active control to change shape.

[0003] Shape adaptation can utilize structural elastic instability. Elastic instability refers to the temporary loss of stiffness in a structural member, which recovers before irreversible deformation occurs. A structural member can be designed to reach an unstable equilibrium from a primary or fundamentally stable state. The member will 'jump' from this unstable equilibrium to a secondary state. If a post-buckling structural member has at least two stable equilibrium states, it is 'multistable'. A 'bistable' structural member has two stable equilibrium states and an intermediate unstable equilibrium state. The member will jump from the primary stable state to the secondary stable state and remain in that secondary stable state, even when the external stimulus is removed. Applying an external stimulus in the secondary stable state can cause the shape to jump back to the primary stable state. A 'monostable' structure can still exhibit jump behavior, but the second state is a stationary (or quasi-stable) rather than a stable state, and therefore, after the external stimulus is removed, the structure will return to the primary state.

[0004] In modified flow control devices, thermal loads, electrical (e.g., piezoelectric) loads, and aerodynamic pressure loads are known to be used as external stimuli. For example, thermally activated flow devices on jet engine cowlings can help suppress acoustic noise.

[0005] It is desirable to make aircraft components as lightweight as possible to improve fuel efficiency and takeoff performance. For aerodynamic components such as wings, weight reduction is typically limited because wings must withstand very large loads and sudden gusts, such as during turbulence. Therefore, providing gust load mitigation allows for weight reduction of the wing without compromising its ability to resist sudden gusts. For gust load mitigation on aircraft wings using variable flow control devices actuated by aerodynamic pressure loads, accurately predicting the magnitude of the local loads generated by gusts can be difficult. Furthermore, under certain maneuvers, aerodynamic pressure loads may resemble gust load scenarios, potentially triggering undesirable hopping phenomena. Summary of the Invention

[0006] According to one aspect of the invention, a flow control device having an aerodynamic surface is provided, the flow control device being arranged on a structural member having a structural aerodynamic surface, such that strain in the structural member is at least partially transferred to the flow control device, the flow control device having a first state corresponding to a first shape of the aerodynamic surface of the device and a second state corresponding to a second shape of the aerodynamic surface of the device, wherein the first state is a stable state of the flow control device and the second state is a smooth state or a second stable state of the flow control device, and the flow control device is arranged to rapidly transition from the first state to the second state when the strain in the structural member exceeds an activation threshold of the flow control device.

[0007] Flow control devices are objects that control the direction of airflow above structural components. In aircraft, flow control devices can be vortex generators, spoilers, blades, vents, etc.

[0008] Here, a rapid transition refers to a 'jump' change from a first stable state to a second stable or steady state within a short time period. This rapid transition is an approximate step change between the first and second shapes of the flow control device via an intermediate unstable equilibrium state. This time period can be on the order of one-tenth of a second or less.

[0009] If a flow control device has a stable second state in addition to a first stable state, then the flow control device is multistable. In each stable state, the flow control device can undergo elastic deformation when loaded. When the load is removed, the flow control device can elastically return to either the first or the second state from which it has just deformed.

[0010] The flow control device can elastically deform from a first stable state to an intermediate unstable equilibrium state as the strain in the structure increases up to an activation threshold. At the activation threshold, the flow control device rapidly transitions to a second stable state. A decrease in strain in the structure will initially bring the flow control device to the second stable state.

[0011] Depending on the potential energy levels of the first and second states and the potential energy threshold between them, additional external stimuli may be required to return the flow control device from the second steady state to the first steady state. In some cases, once the strain in the structure is sufficiently low, the airflow above the flow control device may be sufficient to restore it to the first state. In other cases, external stimuli can be provided by actuators. Another alternative is that external stimuli can be provided manually once the aircraft has landed.

[0012] Alternatively, the flow control device can automatically return to its original state once the strain in the structure is sufficiently low. This can be achieved through negative strain, for example, by bending the structure in the opposite direction to trigger a sudden change to the second state.

[0013] The potential energy levels of the first and second states can be the same or different. The potential energy level of the first state can be lower than that of the second state; for example, the energy input required to reach the activation threshold from the first state to the second state may be higher than the energy input required to reach the (reverse) activation threshold from the second state to the first state. The external force exerted on the flow control device by external stimuli may depend on the operating conditions. For example, when applied to an aircraft, the airflow above the aircraft wing can exert a greater external stimulus (return force) on the flow control device when the aircraft is at high speed compared to when the aircraft is at low speed or zero speed. Therefore, under one operating condition (e.g., low airspeed), the flow control device can function as a multistable device, but under another operating condition (e.g., high airspeed), the flow control may tend not to remain in the second stable state due to external stimuli—thus functioning similarly to a monostable device.

[0014] If a flow control device has a stationary (or quasi-stable) second state in addition to a first stable state, but no second stable state, then the flow control device is monostable. This quasi-stable state can correspond to a local decrease or flattening of the energy level in the potential / deflection diagram. In the first stable state, the flow control device can elastically deform upon loading. When the load is removed, the flow control device can elastically return to the first state. The flow control device can elastically deform from the first stable state until an intermediate unstable equilibrium state is reached when an external stimulus is applied, at which point an activation threshold is reached. At this activation threshold, the flow control device rapidly transitions to the second state. Since this second state is not stable but only stationary or quasi-stable, the removal of the external stimulus can cause the flow control device to return to the first stable state by rapidly transitioning from the second state through the intermediate unstable equilibrium state. In the second state, the flow control device can still elastically deform upon loading.

[0015] When sufficient strain has been transmitted to the flow control device, the flow control device can change from the first steady state to the second state simply by virtue of this. The strain in the structure may be caused by bending, deformation, or movement of the structure, and this strain in the structure will be at least partially transmitted to the flow control device. When the local strain in the structure transmitted to the flow control device reaches or exceeds a threshold T corresponding to the activation threshold, the flow control device will change from the first state to the second state.

[0016] The advantage of using strain within a structural member as the external stimulus for activating the flow control device from a first state to a second state is that, unlike localized aerodynamic loads which can be difficult to predict, the deformation and associated strain levels within the structural member can be accurately modeled. Therefore, the flow control device can be designed to be actuated at specific strain levels unique to the structural member or part thereof on which the flow control device will be used. Activation from the first state to the second state using strain can also be purely passive.

[0017] The first shape of the device's aerodynamic surface can be substantially flush with the aerodynamic surface of the structural component. In this first shape, the flow control device can partially conform to the shape of the structural component. In this first shape, the flow control device can be integrated into the structural component without any obvious aerodynamic steps between the device's aerodynamic surface and the structural component's aerodynamic surface. This ensures that the airflow above the structural component's aerodynamic surface is not interrupted by the flow control device.

[0018] The second shape of the flow control device allows the flow control device to bend away from the structural member and toward the direction of the oncoming flow.

[0019] The aerodynamic surface of the device can have an aerodynamic leading edge (which can be integrated into the structure) and an aerodynamic trailing edge. The aerodynamic surface can be adapted to be rolled into a second shape such that the aerodynamic trailing edge is located away from the aerodynamic surface of the structure. In this second shape, the cross-section of the aerodynamic surface can be curved. This allows the flow control device surface to disrupt airflow on the aerodynamic surface of the structure.

[0020] If the aerodynamic surface of the structural member is an aerodynamic lift surface, the flow control device can be used to disrupt the lift of the aerodynamic surface of the structural member when in the second shape. Disrupting the lift can have the effect of reducing the strain in the structural member below an activation threshold. The flow control device can be configured to return to a first steady state when the strain in the structural member decreases below the activation threshold due to the reduction in lift. This may occur due to a hysteresis in the flow control device. The flow control device can delay the return to the first steady state until the strain in the structural member decreases to a second strain threshold, or there may be a time delay after the strain decreases below the activation threshold.

[0021] Flow control devices can be configured to provide aerodynamic load relief or reduction for structural components. These components may be tensioned due to aerodynamic loads. When the strain in the structural component reaches an activation threshold, the flow control device can change from a first state to a second state, thereby reducing the aerodynamic load on the structural component.

[0022] The activation threshold of the flow control device can be adjustable. The activation threshold can be predetermined. The activation threshold can be adjusted to the strain that is desired or anticipated to be experienced by the structural member or the portion of the structural member directly physically connected to the flow control device.

[0023] The flow control device can be a panel, especially a sheet or plate, preferably having a three-dimensional curvature.

[0024] The activation threshold can be adjusted by selecting one or more of the following: thickness, material, shape, layup (if it is a laminate), fiber layer orientation (if it is a fiber-reinforced composite), prestress, etc. of the flow control device.

[0025] The flow control device may have a first activation threshold for transitioning from a first state to a second state. The flow control device may also have a second activation threshold for transitioning from the second state to the first state. The first and second activation thresholds may be the same, similar, or different. When the activation thresholds differ, the flow control device may exhibit a significant strain activation hysteresis between the first and second states; that is, the device may be deployed at the first strain threshold and then remain deployed until the strain in the wing decreases significantly below the second strain threshold.

[0026] The flow control device can be configured such that the second steady state is maintained only by keeping the strain in the structure above the activation threshold.

[0027] The flow control device can be configured to return to the first state once the strain in the structure decreases below the activation threshold.

[0028] The flow control device can be configured to automatically return to a first stable state once the strain in the structure decreases below an activation threshold; for example, the device is monostable.

[0029] Alternatively, the flow control device can be configured to remain in a second stable state at least initially when the strain in the structure decreases below an activation threshold; for example, the device is bistable.

[0030] The flow control device may not automatically return from the second state to the first steady state, even when the strain in the structure decreases to below or significantly below the activation threshold.

[0031] The aerodynamic surface of the flow control device can be generally rectangular in the first state, and preferably, the shorter side of the rectangle extends generally parallel to the direction of the oncoming flow.

[0032] The aerodynamic surfaces of flow control devices can typically take any shape when viewed in a plan view, such as any regular shape or any irregular shape.

[0033] The flow control device may have a proximal end facing the oncoming flow direction, and the proximal end of the flow control device may be attached to or integrally formed with a structural member. Lateral and / or distal edges of the device's aerodynamic surfaces (relative to the upcoming flow direction) may be free, for example, not directly connected to the structural member. These free edges may allow the device's aerodynamic surfaces to bend away from the structural member.

[0034] The flow control device may have a distal end opposite to the proximal end, wherein the distal end is not attached to the structure, such that the flow control device extends cantileveredly from the structure through its proximal end.

[0035] Strain in the structural component can be at least partially transferred to the flow control device through the proximal end to which it is attached or integrally formed.

[0036] Flow control devices can be retrofitted to existing structures, for example, by creating cutouts in the aerodynamic surfaces of the structure to accommodate the flow control device, or by mounting the flow control device on the structure and aerodynamically integrating it with the structure's aerodynamic surfaces. More typically, the flow control device will be designed and tailored to the new structure.

[0037] Flow control devices can be mechanically attached to structural components, such as, but not limited to, bolting, riveting, and fastening. Alternatively, flow control devices can be attached using adhesives or bonding devices.

[0038] Alternatively, the proximal end of the flow control device can be integrally formed with the structural member. Integrating the flow control device with the structural member avoids any joints between the aerodynamic surfaces of the structural member and the aerodynamic surfaces of the device in the flow direction, and also saves weight.

[0039] The structural component may include composite materials or metallic materials. In the case where the structural component includes a composite material, the composite may be a laminate, and the flow control device may form part of the laminate stack.

[0040] Integrating the flow control device with the structural components can reduce the number of manufacturing steps required to produce the structural components / devices, saving weight and reducing the number of parts.

[0041] Alternatively, structural components may include isotropic materials such as metals.

[0042] Flow control devices may include anisotropic materials.

[0043] Flow control devices may include laminated materials.

[0044] Flow control devices may include prestressed isotropic materials.

[0045] Isotropic flow control devices can be prestressed through various processes, such as bending or shot peening. The prestressed flow control device can be attached to a structural member under stress, or it can be prestressed separately from the structural member and integrally formed with it. The flow control device can be prestressed during installation on the structural member by, for example, bending the structural member (applying stress), attaching the flow control device, and then releasing the structural member, allowing it to relax and applying stress to the flow control device during its relaxation.

[0046] Structural components can form part of an airfoil.

[0047] An airfoil can be adapted to generate lift when moving relative to an airflow. A flow control device can be configured to interact with the airflow around the airfoil in a second state to reduce the lift generated by the airfoil compared to the lift generated by the airfoil when the flow control device is in a first state.

[0048] The aerodynamic surface of a structural component can be the low-pressure surface of an airfoil. Alternatively, the aerodynamic surface of a structural component can be the high-pressure surface of an airfoil. The airfoil can have corresponding flow control devices on each of the high-pressure and low-pressure surfaces.

[0049] A structure with a low-pressure surface can be configured to withstand compressive strain when the airfoil generates lift, and a flow control device can be configured to rapidly transition from a first state to a second state when the compressive strain in the structure exceeds an activation threshold due to the lift generated by the airfoil.

[0050] Flow control devices can be lift spoilers, ailerons, vortex generators, blades, vents, etc.

[0051] The structural components can be located on aircraft (fixed-wing, rotary-wing, or tiltrotor), land vehicles, or space vehicles (for use in the atmosphere).

[0052] Spoilers can be positioned at approximately one-quarter chord of the airfoil.

[0053] Alternatively, the spoiler can be positioned in front of the leading edge of the airfoil at the quarter-chord position, or behind the trailing edge of the airfoil at the quarter-chord position.

[0054] Flow control devices on structural components can be located on the aircraft wing or wingtip assembly. Strain in the wing / wingtip assembly may be caused by loads on the aircraft wing. These loads can be aerodynamic loads or other external loads. Strain may be caused by bending, deformation, or movement of the structural component.

[0055] The flow control device can be located in the transition area between the wing and the upward protrusion of the wingtip device of the aircraft.

[0056] The transition zone is the area where the wing experiences the maximum vertical deflection relative to the fuselage.

[0057] In another aspect of the invention, a method is proposed for controlling airflow above an airfoil having a modified flow control device, the method comprising: manipulating the airfoil to induce strain in a structural member of the airfoil; and activating a modified flow control device disposed on the structural member by utilizing the strain in the structural member to rapidly transition from a stable first state to a stable or smooth second state when the strain level of the flow control device exceeds a threshold due to the increased strain in the structural member, wherein the first state corresponds to a first shape of the aerodynamic surface of the device, and the second state corresponds to a second shape of the aerodynamic surface of the device.

[0058] The flow control device in the second state can interact with the airflow above the airfoil to reduce the lift generated by the airfoil compared to the lift generated by the airfoil when the flow control device is in the first state.

[0059] In another aspect of the invention, the airfoil includes a low-pressure surface and a spoiler disposed on the low-pressure surface, the spoiler having a rest position in which the spoiler is substantially flush with the low-pressure surface and an active position in which the spoiler protrudes from the low-pressure surface and alters the airflow above the surface; wherein the spoiler is a means having a stable state in the rest position and a stable or quasi-stable state in the active position; the spoiler is bent to move from the rest position to the active position; and the connection between the spoiler and the airfoil causes at least some strain to be transmitted from the airfoil to the spoiler, and the movement of the spoiler is triggered by strain in the airfoil exceeding a threshold.

[0060] In another aspect of the invention, a method for arranging a spoiler to an aerodynamic surface is provided, the method comprising: providing an aerodynamic surface; and providing a spoiler having a first state corresponding to a first shape of the spoiler and a second state corresponding to a second shape of the spoiler, wherein the first state is a stable state of the spoiler and the second state is a smooth state or a second stable state of the spoiler, wherein the spoiler has a proximal end facing the direction of oncoming flow, and the proximal end of the spoiler is attached to or integrally formed with the aerodynamic surface, wherein the spoiler is arranged to rapidly transition from the first state to the second state when strain in the aerodynamic surface is transferred to the spoiler and exceeds an activation threshold of the spoiler, such that strain in the aerodynamic surface is transferred to the spoiler, thereby causing the spoiler to bend away from the aerodynamic surface. Attached Figure Description

[0061] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0062] Figure 1 It is a plan view of the aircraft;

[0063] Figure 2 The image shows a front view of the aircraft's wing as seen from the rear.

[0064] Figure 3 A plan view of the outer portion of an aircraft wing with wingtip devices and flow control devices according to the first example is shown;

[0065] Figures 4A to 4G A front view of an aircraft wing that bends upward during different load conditions and the corresponding deployment of flow control devices is shown.

[0066] Figures 5A to 5G It shows crossing with Figures 4A to 4G The corresponding cross-section of the aircraft wing with the relevant flow control devices;

[0067] Figures 6A to 6G A front view is shown of the aircraft wing according to the second example, bending upwards during different load conditions, and the corresponding deployment of the flow control device;

[0068] Figures 7A to 7G It shows crossing with Figures 6A to 6G The corresponding cross-section of the aircraft wing with the relevant flow control devices;

[0069] Figure 8 A schematic diagram showing the correlation between the deflection of the wingtip of an aircraft and the (compressive) strain on the upper surface of the wing is shown.

[0070] Figure 9The potential energy diagram for the bistable system is shown;

[0071] Figure 10 The potential energy diagram for the monostable system is shown;

[0072] Figure 11 An example of a flow control device attached to a structural component is shown;

[0073] Figure 12 An example of a flow control device integrally formed with a structural component is shown;

[0074] Figure 13A An example of a flow control device including an isotropic material is shown;

[0075] Figures 13B to 13D This shows the effect on the structural components. Figure 13A An exemplary method for prestressing a flow control device. Detailed Implementation

[0076] Figure 1 An aircraft 1 is shown, comprising a port fixed wing 2 and a starboard fixed wing 3, and a fuselage 4. The fuselage 4 has a nose section 5 and a tail section 6, the tail section 6 including a horizontal stabilizing surface 6a and a vertical stabilizing surface 6b. Each wing has leading edges 2a, 3a and trailing edges 2b, 3b. Aircraft 1 is a typical jet-powered transonic passenger transport aircraft, but this invention is applicable to various types of fixed-wing aircraft, including commercial, military, passenger, cargo, jet, propeller, and general aviation, with any number of wings attached to the wings or fuselage. In fact, this invention can be applied to various industries requiring aerodynamic flow control, including aviation, aerospace, automotive, wind turbine, marine, and other industries.

[0077] Figure 1 and Figure 2 The axes shown represent the general reference orthogonal axes of aircraft 1. The X-axis defines the longitudinal forward and backward direction of the aircraft; the Y-axis defines the wingspan direction; and the Z-axis defines the vertical up and down direction of the aircraft.

[0078] Each wing 2, 3 of the aircraft has a cantilever structure extending from the root to the tip in the wingspan direction, with the root connected to the fuselage 4. The wing portion near the root is called the inward region. The wing portion near the tip is called the outward region. The wing has an upper surface 8 and a lower surface 9. At the tip of each wing 2, 3 is the wingtip assembly 7, located on the outer side of the main wing portion. The wingtip assembly is used to reduce induced drag of the aircraft.

[0079] Different aircraft have different wingtip devices 7 designs. Between the main body of the wing and the wingtip device 7, there is a transition region 11. This transition region ensures that the aerodynamic profile between the wing and the wingtip device is maintained through a smooth surface blend. The wingtip device has a generally upward-protruding portion. The angle of this generally upward-protruding portion (relative to the vertical) is called the bevel angle. This bevel angle may vary for different wingtip devices. The upper surface of the transition region 11a is a smoothly upward-curved surface. Alternatively, the wing can have different wingtip device configurations, such as wingtip grilles, drooping wingtips, 'shark fins', or sloping winglet designs, or other known designs.

[0080] The wings have external aerodynamic surfaces. Wings 2 and 3 are swept back and have multiple aerodynamic flight control surfaces. These flight control surfaces can be adjusted during flight to regulate the aircraft's attitude or wing performance. They include numerous flight control surfaces such as ailerons, elevators, rudders, spoilers, flaps, slats, and air brakes. These flight control surfaces are typically located on wings 2 and 3 or on the horizontal stabilizer 6a or vertical stabilizer 6b of aircraft 1.

[0081] During flight, the wings are subjected to aerodynamic and inertial loads. Wings 2 and 3 exhibit aeroelastic behavior. For example, when the wings experience increased aerodynamic lift, they bend upwards along the Z-axis. The wings have the following airfoil profile, in which the lower wing cover experiences higher pressure and the upper wing cover experiences lower pressure. Extreme weather conditions, such as extreme gusts, can also cause wings 2 and 3 to deflect and deform in the vertical direction. The upward bending of wings 2 and 3 causes the upper cover 8 to compress and the lower cover 9 to be in a stretched state. As the wingtip device 7 deflects upward, the strain in the wings increases. Wings 2 and 3 experience strain due to bending, deflection, and other motions caused by external forces applied to the wings. Flight control surfaces can be used to limit the amount of strain experienced by the aircraft by controlling airflow on the aerodynamic surfaces of the aircraft. For example, spoilers and ailerons can be used on the aircraft wings to reduce the lift experienced by the aircraft, a so-called load-reduction function.

[0082] The main lift spoiler is typically located on the trailing edge 2b or 3b of the aircraft wing, directly in front of the flaps. For example... Figure 3 As shown, another flow control device 12 is located on the curved upper surface of the wing in the transition region 11a between the wingtip and the upwardly protruding portion of the wingtip device 7. Figure 3 The flow control device 12 shown is configured as a lift spoiler. During the upward bending of the wing 2, for example during extreme gusts, the upper surface of the transition region 11a undergoes relatively large deflection and deformation. Therefore, region 11a experiences (compressive) strain.

[0083] Preferably, the flow control device and spoiler 12 are located at approximately one-quarter of the chord of the partial airfoil profile of the aircraft wing 2, such as... Figure 6A As shown in the diagram, the quarter chord, C / 4, is approximately the point where the aerodynamic resultant force acts. This is the area on the airfoil that generates most of the lift. This allows the spoiler 12 to interfere with the location of the wing's maximum lift, and therefore, positioning the spoiler at this point is most effective in reducing lift.

[0084] The spoiler 12 has a proximal end 12a and a distal end 12b. The proximal end 12a of the spoiler is attached to the wing 2 / wingtip assembly 7 at the upper surface of the transition region 11a. The proximal end 12a can be attached mechanically, for example, by bolting. Alternatively, the proximal end can be integrally formed with the surface of the aircraft wing. The proximal end 12a of the spoiler faces the oncoming airflow direction A. The distal end 12b is not attached to the surface of the aircraft wing, i.e., the distal end 12b is cantilevered. The spoiler has an upper (outer, aerodynamic) surface 12c and a lower (inner, reverse) surface 12d. Figure 3 (Not shown in the image). In this example, the spoiler 12 is roughly rectangular in the plan view, as shown below. Figure 3 As shown in the diagram, the near end 12a and far end 12b of the spoiler 12 may have aerodynamic leading and trailing edges that are slightly curved in plan view.

[0085] Figure 3 The diagram shows a first stable state 20 for the spoiler 12. The shape of the spoiler 12 is substantially similar to or conformal to the local shape of the wing 2 / wingtip assembly 7 on which the spoiler 12 is disposed. The upper surface 12c of the spoiler has a shape corresponding to or conforming to the local surrounding aerodynamic surfaces of the wing 2 / wingtip assembly 7. In the first state, the spoiler 12 is substantially flush with the aerodynamic surfaces of the wing 2 / wingtip assembly 7. It should be understood that the spoiler 12 can be positioned anywhere along the length of the wing 2. Regardless of its position along the wing, in the first state, the upper surface 12c of the spoiler 12 will have a shape substantially similar to that of the airfoil portion of the structure on which the spoiler is disposed.

[0086] Since wings 2 and 3 are structurally similar, wing 3 will have similarly arranged flow control devices to be symmetrical with wing 2.

[0087] Figures 4A to 4G A front view of an aircraft wing with spoiler 12 is shown in the first example. This example involves spoilers arranged to form a bistable system. Figures 4A to 4G The illustration shows an aircraft wing that, for example, is in different degrees of upward deflection in response to the increased lift generated by the wing. Figure 4A The wing 2 and wingtip device 7 are shown in their initial position 13, and Figures 4B to 4D The diagram shows the wing gradually moving through positions 14 and 15 to reach the maximum upward deflection position 16, accompanied by a corresponding decrease (or even a negative) in the angle of the upward protrusion of the wingtip device 7. Figures 4E to 4G The diagram shows the wing returning to its initial position 19 via positions 17 and 18 when the wing deflection is reduced, for example, due to a reduction in wing load.

[0088] Figures 5A to 5G The wing is shown in Figures 4A to 4G Each deflection position shown is 13 to 19 (through) Figure 4A The corresponding cross section of the XX. Each corresponding cross section has the same reference numerals, but with a 'C' after the deflection position mark. For example, 13 indicates the initial position of the wing, while 13C indicates the corresponding cross section of the wing.

[0089] The spoiler 12 is in a first stable state 20, wherein it is in a first shape in the initial position 13 of the wing, such as... Figure 4A As shown in the image.

[0090] Figure 4B The diagram shows an wing deflected upwards to a very small degree from its initial position. As the wing 2 bends and deforms, the compressive stress on the upper skin 8 of the wing increases, and therefore the strain in the wing increases. A spoiler is arranged on the wing, so the strain in the wing 2 is at least partially transferred to the spoiler 12. Therefore, the spoiler 12 will also be subjected to strain and will be elastically deflected to a smaller degree compared to its first shape in the initial position 13. If the strain in the upper surface of the wing / wingtip assembly is sufficiently small, the spoiler will remain in a first stable state 20, i.e., if the wing load decreases, the spoiler shape will elastically return to its initial shape from the deflected position 14 to the initial position 13.

[0091] Figure 4C The diagram shows a wing deflecting upwards to a greater extent. When the strain in wing 2 reaches the activation threshold T, spoiler 12 rapidly transitions from a first stable state 20 to a second stable state 22, which... Figure 4C , Figure 5C and Figure 11 or Figure 12 It is best shown in the middle.

[0092] In the second stable state 22, the spoiler 12 changes to a second shape. In the second shape, the proximal end 12a of the spoiler remains substantially flush with the wing surface. The distal end 12b extends upward from the wing surface. The upper surface 12c of the spoiler curls upward. The final shape of the spoiler 12 is generally curved. The spoiler curves upward and away from the wing's aerodynamic surface. This allows the spoiler to disrupt the oncoming airflow A. The upper surface 12c of the spoiler faces the oncoming airflow A. This alters the airflow above the wing by disrupting lift and reduces the lift of the local airfoil section, thus reducing lift in the outer wing region of the aircraft. The reduction in lift generated by the wing allows for a reduction in the deflection of the wing 2.

[0093] The wing strain activation threshold T can be set to below Figure 4D The strain is shown at the maximum wing deflection position 16. The strain in the wing during the maximum deflection at position 16 is greater than the strain in the wing during positions 13 to 15. Even when the wing strain is above the activation threshold T, the wing load may still increase until the maximum wing deflection. When the spoiler is deployed to the second state, if the wing deflection increases until the maximum wing deflection, the second shape 22 of the spoiler may still deform further. Since the second state is the second stable state in the bistable system, the spoiler shape will tend to elastically deform and recover in the second state.

[0094] If the wing deflects as Figures 4E to 4F As shown in the diagram, the spoiler 12 will remain deployed in the second state 22, where it is engaged, even if the strain is further reduced to below the wing strain activation threshold T. This remains true even if the strain is reduced to below the wing strain activation threshold T, as shown in position 18, because the second state is a steady state.

[0095] Figure 4G The wing position 19 shown is similar to the initial wing position 13, and the spoiler is shown returning to the first state. The spoiler 12 can remain in the second stable state even as the wing deflection in position 19 decreases back to the initial position. In some cases, this is acceptable, and a manual 'reset' of the flow control may be necessary, such as when the aircraft returns to the ground after flight. Alternatively, airflow over the wing can cause a transition back to the first state.

[0096] The spoiler 12 rapidly transitions from a first stable state 20 to a second stable state 22. Here, rapid transition refers to a 'jump' change from the first stable state to the second stable or steady state within a short period of time. This rapid transition is an approximate step change between the first and second shapes of the flow control device through an intermediate unstable equilibrium state.

[0097] Figure 8 A schematic graph 30 is shown illustrating the relationship between wingtip deflection and strain in wing 2. As wingtip deflection increases, strain in the wing increases. The dashed line represents the strain activation threshold 'T' of spoiler 12. Once the strain in the wing exceeds the threshold T, the spoiler rapidly transitions from state 20 to state 22.

[0098] In the above about Figures 4A to 4G In the described example, the spoiler is constructed as a bistable system. The spoiler can exist in two stable equilibrium states: a first stable state 20 and a second stable state 22. Figure 9 The energy potential of a typical bistable system is schematically illustrated. When the strain transmitted to spoiler 12 is below the activation threshold T, the spoiler remains in a first stable state 20 while the energy potential remains in the first well region 32. As the strain transmitted to the spoiler approaches the threshold T, the potential energy / activation energy approaches an unstable equilibrium at 33. At the unstable equilibrium region 33, if the strain threshold is exceeded, the bistable spoiler will rapidly transition to a second equilibrium state. The second equilibrium state is the second stable state 22 of the spoiler, and the energy potential in this state is the second well region 34. Even if the strain in wing 2 subsequently decreases below the activation threshold T, the spoiler will initially remain in the second stable state 22 without any further force acting on it.

[0099] The strain activation threshold T can be adjusted to a specific value. The unstable equilibrium region 33 can be determined to match the expected strain in the wing 2 where the spoiler 12 will be installed by changing the geometry, size, thickness, material, material stack, prestress, etc.

[0100] Figures 6A to 6G A front view of an aircraft wing with spoiler 12 is shown in the second example. This example involves spoilers arranged to form a monostable system. Figures 4A to 4G similar, Figures 6A to 6G The illustration shows an aircraft wing that, for example, is in different degrees of upward deflection in response to the increased lift generated by the wing. Figure 6A The wing 2 and wingtip device 7 are shown in their initial position 43, and Figures 6B to 6D The diagram shows the wing gradually moving through positions 44 and 45 to reach the maximum upward deflection position 46, accompanied by a corresponding decrease (or even a negative) in the angle of the upward protrusion of the wingtip device 7. Figures 6E to 6G The diagram shows the wing returning to its initial position 49 via positions 47 and 48 when the wing deflection is reduced, for example, due to a reduction in wing load.

[0101] Figures 7A to 7G The wing was shown in Figures 6A to 6GEach deflection position shown is at 43 to 49 (through) Figure 6A The corresponding cross-section of the XX. Each corresponding cross-section has the same reference numerals, but with a 'C' after the deflection position mark. For example, 43 indicates the initial position of the wing, while 43C indicates the corresponding cross-section of the wing.

[0102] The spoiler 12 has the same characteristics as previously described in Figures 4 (4A to 4G) and 5 (in the first and second states). Figures 5A to 5G The spoiler has a roughly the same shape as in the first example, and therefore the difference between the monostable and bistable arrangements will now be described only. The 'jump' rapid transition of the spoiler from the first state to the second state when the strain activation threshold 'T' is reached is the same as that of the bistable system in the first example described above. However, in the monostable system of the second example, the second state 24 of the spoiler 12 is not a smooth equilibrium state, but a quasi-stable or smooth state that is not maintained when the strain decreases below the strain activation threshold 'T'.

[0103] Figure 10 The energy potential of a typical monostable system is schematically illustrated. When the strain transferred to the spoiler 12 is below the activation threshold T, the spoiler remains in the first stable state 20 because the energy potential is maintained in the first well region 36. When the strain transferred to the spoiler approaches the threshold T, the potential energy / activation energy approaches the unstable equilibrium region 37. In the unstable equilibrium region 37, if the strain threshold is exceeded, the monostable spoiler will rapidly transition to the second equilibrium region 38. The unstable equilibrium region 7 is a sharp inflection point in the energy / strain curve, but it always maintains a positive gradient or is close to zero gradient.

[0104] The second equilibrium region 38 corresponds to a stable (or quasi-stable) second state 24 for the spoiler. In this second state, the spoiler 12 exhibits a significantly different shape compared to the first shape following a sudden jump in elastic instability at the unstable equilibrium region 37. If the wing strain decreases below a threshold T, the spoiler 12 will revert to the first stable state 20 (first shape). There may be some hysteresis, but this hysteresis is likely to be small. Figure 10 As shown, the second equilibrium region 38 always has a positive gradient, unlike the previously described bistable system where a second well region does not exist. If the wing strain remains above a threshold T, the spoiler will remain in the second stable state 24. Once the wing strain decreases below the threshold T, the spoiler 12 will rapidly transition or abruptly return to the first stable state 20. The monostable spoiler system is inherently a passive system because it has only one stable state. Compared to the bistable spoiler system of the first example, the passive nature of the monostable spoiler system requires fewer components and does not require active / passive control.

[0105] Figures 6A to 6G The spoiler 12 described herein returns to a first stable state after the strain in the wing 2 falls below the activation threshold T. The corresponding cross-section of the wing is shown below. Figures 7A to 7C As shown, when the compressive strain in the wing decreases below the activation threshold, the spoiler 12 returns to the first stable state 20, as... Figure 6F As shown in the image.

[0106] Multiple spoilers 52 can be arranged on the wingtip device 7. Each spoiler is independently actuated by the wing strain of its respective spoiler region. The multiple spoilers can be adjusted to deflect to the second state at the same wing strain activation threshold, or the spoilers can be adjusted to deflect to the second state at different wing strains.

[0107] Figure 11 This illustrates one manner in which spoiler 12 can be attached to wing 2, 3 or wingtip device 7 according to the preceding example. It should be understood that this method can also be used for spoiler 52, or any other spoiler design. Component 60 is an aerodynamic structural member having aerodynamic surfaces 61. The proximal end 12a of the spoiler is attached to this aerodynamic structural member. The proximal end 12a can be attached mechanically, for example, by means of multiple bolts 62. The proximal end 12a can also be attached by any other mechanical means, such as, but not limited to, rivets or fasteners.

[0108] Figure 12 Another method for arranging a spoiler to an aerodynamic structural member is illustrated. The distal end 12b and corresponding edges 12e and 12f of the spoiler are separated from the aerodynamic surface 61 during the manufacturing process, while the proximal end remains integrally formed with the structural member. This allows the distal end 12b and the corresponding edges of the spoiler to remain freely bent upwards and away as the spoiler changes state from a first state to a second state. Figure 12 In both Figure 1 and Figure 13, the aerodynamic surface 61 may have a recess or opening to receive the spoiler 12 when it is stationary. When the spoiler is stationary, the upper surface 12c of the spoiler may be flush with the aerodynamic surface 61.

[0109] Spoilers can include composite materials, such as fiber-reinforced matrix composites, for example, carbon fiber reinforced plastic (CFRP). To achieve multistable and monostable characteristics of the spoiler, multiple laminates formed of composite materials with different fiber orientations can be provided in the stack.

[0110] Multistable and monostable characteristics of spoilers can be achieved by using anisotropic materials. Spoilers can be laminated components made by stacking multiple composite layers. The composite layers can have different fiber orientations to achieve the anisotropic behavior of the spoiler, thus enabling the spoiler to be monostable or multistable.

[0111] Spoilers can also be made of isotropic materials. Figure 13A A spoiler 12 comprising an isotropic material 40 is shown, which is, for example, but not limited to, a metal. To enable the isotropic material to have a monostable or multistable state, it may be necessary to prestress it. Figures 13B to 13D An example of a flow control device that is prestressed and mounted on a structural member is shown.

[0112] The flow control device has an upper surface 20a and a lower surface 20b. Due to the prestress 41, the flow control device 12 exhibits a natural tendency to curl upwards in one of its states. Then, when the aerodynamic structure deforms in a direction opposite to its typical deformation direction—for example, causing the aircraft wing to bend downwards—the flow control device can be fixed to the aerodynamic surface. By releasing the load on the deformed aerodynamic structure, the aerodynamic structure relaxes (the wing deflects upwards back) and loads the flow control device to resist the prestress, such as... Figure 13C As shown, this is to construct the first stable state of the flow control device. However, when the structural member is loaded in its typical deformation direction, for example, when the wing bends upward, the flow control device abruptly jumps to the second upward curled state (shape) 42, as shown. Figure 13D As shown in the figure. Prestressing of isotropic materials can be achieved through various known methods, such as shot peening a surface of a flow control device.

[0113] Monostable and multistable spoiler designs can provide passive load reduction for aircraft wings. Passive designs reduce or eliminate active mechanical components, such as the hydraulic actuators traditionally required to actuate flow control devices. This reduces the overall weight and design complexity of the aircraft. Passively actuated spoilers can be used in thin airfoil sections, such as wingtip devices, where space constraints may preclude the use of traditional actuator components. These thin airfoil sections typically occur at the wingtip, where flow control exerts a significant lever arm effect on wing loads. Reducing the wing bending moment at the wing root allows for a lighter structure and significant weight savings across the entire wing design.

[0114] The example of an upper aerodynamic surface spoiler on an aircraft wing described in detail above is designed to provide load relief in extreme wing 'upward flex' conditions. However, similar spoilers can be attached to the lower aerodynamic surface of the wing to provide load relief in extreme wing 'downward flex' conditions that may occur during certain aileron-driven maneuvers. In this case, the lower aerodynamic surface of the wing will exhibit compressive strain, and the activation threshold selected for this lower surface strain can be used as a trigger to deploy the lower surface spoiler from a flush first shape or state to a 'deployed' second state or shape. The wing can have both these upper and lower surface spoilers.

[0115] Although the present invention has been described with respect to spoilers on aerodynamic structures of aircraft, it should be understood that the present invention can be used for many different flow control devices on different aerodynamic structures subjected to strain.

[0116] When the word 'or' appears, it will be interpreted as meaning 'and / or', meaning that the items referred to are not necessarily mutually exclusive and can be used in any appropriate combination.

[0117] Although the invention has been described above with reference to one or more preferred embodiments, it should be understood that various changes or modifications may be made without departing from the scope of the invention as defined by the appended claims.

Claims

1. A flow control device located on a structural member, the flow control device having a device aerodynamic surface, the structural member having a structural aerodynamic surface, wherein, The flow control device is arranged on the structural member such that strain in the structural member is at least partially transferred to the flow control device. The flow control device is configured to alter the airflow above the aerodynamic surface of the structural member and has a first state corresponding to a first shape of the aerodynamic surface of the device and a second state corresponding to a second shape of the aerodynamic surface of the device. Wherein, the first state is a stable state of the flow control device, and the second state is a steady state or a second stable state of the flow control device, and the flow control device is arranged to rapidly transition from the first state to the second state when the strain in the structural member exceeds the activation threshold of the flow control device. The flow control device has a proximal end facing the oncoming flow direction and a distal end opposite to the proximal end. The proximal end of the flow control device is attached to or integrally formed with the structural member, and the distal end of the flow control device is not attached to the structural member, such that the flow control device extends cantilevered from the structural member through the proximal end. Wherein, the first shape of the aerodynamic surface of the device is substantially flush with the aerodynamic surface of the structural component, and The second shape of the aerodynamic surface of the device is away from the structural member and bends toward the direction of the oncoming flow.

2. The flow control device located on the structural member according to claim 1, wherein, The activation threshold of the flow control device is adjustable.

3. The flow control device located on the structural member according to claim 1 or 2, wherein, The flow control device is configured such that a stable second state is maintained only by keeping the strain in the structure above the activation threshold.

4. The flow control device located on the structural member according to claim 3, wherein, The flow control device is configured to return to the first state once the strain in the structure decreases below the activation threshold.

5. The flow control device located on the structural member according to claim 1 or 2, wherein, The flow control device is configured to remain at least initially in the second stable state when the strain in the structure decreases below the activation threshold.

6. The flow control device located on a structural member according to claim 1 or 2, wherein, The aerodynamic surface of the device is approximately rectangular in the first state.

7. The flow control device located on the structural member according to claim 6, wherein, The shorter side of the rectangle extends approximately parallel to the direction of the oncoming flow.

8. The flow control device located on a structural member according to claim 1 or 2, wherein, The strain in the structural member is at least partially transmitted to the flow control device through the proximal end to which the flow control device is attached or integrally formed.

9. The flow control device located on a structural member according to claim 1 or 2, wherein, The flow control device is monostable or bistable.

10. The flow control device located on a structural member according to claim 1 or 2, wherein, The flow control device includes anisotropic materials.

11. The flow control device located on a structural member according to claim 1 or 2, wherein, The flow control device includes a laminated material.

12. The flow control device located on a structural member according to claim 1 or 2, wherein, The flow control device comprises a prestressed isotropic material.

13. The flow control device located on a structural member according to claim 1 or 2, wherein, The structural component forms part of an airfoil.

14. The flow control device located on a structural member according to claim 13, wherein, The airfoil is adapted to generate lift when moving relative to an airflow, and wherein the flow control device is configured to interact with the airflow around the airfoil in the second state to reduce the lift generated by the airfoil compared to the lift generated by the airfoil when the flow control device is in the first state.

15. The flow control device located on a structural member according to claim 13, wherein, The aerodynamic surface of the structural component is the low-pressure surface of the airfoil.

16. The flow control device located on a structural member according to claim 15, wherein, The structure having the low-pressure surface is configured to withstand compressive strain when the airfoil generates lift, and the flow control device is configured to rapidly transition from the first state to the second state when the compressive strain in the structure exceeds the activation threshold due to the lift generated by the airfoil.

17. The flow control device located on a structural member according to claim 13, wherein, The flow control device is a lift spoiler.

18. The flow control device located on a structural member according to claim 17, wherein, The spoiler is positioned at approximately one-quarter chord of the airfoil.

19. A wingtip device comprising a flow control device located on a structural member according to any one of claims 13-18.

20. An aircraft wing, comprising a flow control device located on a structural member according to any one of claims 13-18.

21. The aircraft wing according to claim 20, wherein, The aircraft wing is provided with a wingtip device at its tip, and the flow control device is arranged in the transition area between the aircraft wing and the upward protrusion of the wingtip device.

22. A method for controlling airflow above an airfoil with a modified flow control device, wherein, The modified flow control device is a flow control device located on a structural member according to any one of claims 1-18, and the method includes: Manipulate the airfoil to induce strain in the airfoil's structural components; and The modified flow control device arranged on the structure is activated by the strain in the structure so that when the activation energy of the flow control device exceeds a threshold due to the increased strain in the structure, it rapidly transitions from a stable first state to a stable or smooth second state. Wherein, the first state corresponds to a first shape of the aerodynamic surface of the flow control device, and the second state corresponds to a second shape of the aerodynamic surface of the device.

23. The method according to claim 22, wherein, The strain is caused by the bending, deformation, or movement of the structural member.

24. The method according to claim 22 or claim 23, wherein, In the second state, the flow control device interacts with the airflow above the airfoil to reduce the lift generated by the airfoil compared to the lift generated by the airfoil when the flow control device is in the first state.

25. An airfoil comprising a low-pressure surface and a spoiler disposed on the low-pressure surface, the spoiler having a resting position in which the spoiler is substantially flush with the low-pressure surface and an activated position in which the spoiler protrudes from the low-pressure surface and alters the airflow above the low-pressure surface; wherein, The spoiler is a device that has a stable state in the rest position and a stable or quasi-stable state in the activated position; the spoiler is bent to move from the rest position to the activated position; Furthermore, the connection between the spoiler and the airfoil allows at least some strain to be transferred from the airfoil to the spoiler, and the movement of the spoiler is triggered by strain exceeding a threshold in the airfoil. Wherein, the spoiler is a flow control device located on a structural member according to any one of claims 1-18, the structural member is the airfoil, and the aerodynamic surface of the structural member is the low-pressure surface.

26. A method for setting a spoiler on an aerodynamic surface, the method comprising: Provides aerodynamic surfaces; as well as A spoiler is provided having a first state corresponding to a first shape of the spoiler and a second state corresponding to a second shape of the spoiler, wherein the first state is a stable state of the spoiler, and the second state is a smooth state or a second stable state of the spoiler, wherein the spoiler has a proximal end facing the oncoming flow direction and a distal end opposite to the proximal end, and the proximal end of the spoiler is attached to or integrally formed with the aerodynamic surface, and the distal end of the spoiler is not attached to the aerodynamic surface, such that the spoiler extends from the aerodynamic surface in a cantilever manner through the proximal end; The spoiler is arranged to rapidly transition from the first state to the second state when the strain in the aerodynamic surface is transmitted to the spoiler and exceeds the spoiler's activation threshold, such that the strain in the aerodynamic surface is transmitted to the spoiler, causing the spoiler to move away from the aerodynamic surface and bend toward the oncoming flow direction.

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