Wing construction for an aircraft

Abstract

The invention relates to a wing structure for an aircraft (1), comprising a wing having at least two half-wings (3), two wings (3), and at least two struts (4), wherein the wings (half-wings) and the struts (4) are connectable to an aircraft fuselage (2) of an aircraft (1), wherein the half-wings (3) are each supported at a respective support point (7) by at least one strut (4), characterized in that a tank (5) is arranged between each half-wing (3) and the strut (4) supporting it, the tank (5) being arranged to connect the strut (4) and the half-wing (3). The invention further relates to an aircraft (1) comprising an aircraft fuselage (2), in which the aircraft fuselage (2) is connected to a wing structure according to one of the preceding claims.

Description

[0001] The present invention relates to an airfoil construction for aircraft, in particular for the use of high aspect ratio airfoil shapes.

[0002] The aspect ratio of wing shapes is often maximized in aircraft design to reduce induced drag, which opposes airspeed. This optimizes flight characteristics and reduces fuel consumption.

[0003] Therefore, it is generally desirable, at least in the speed range typically used by commercial aircraft, to increase the aspect ratio of the wings. This results in comparatively narrow and long wings. However, it is more difficult to achieve the necessary structural strength with narrow wings. The general trend is that wing mass increases with increasing aspect ratio. The optimal aspect ratio is therefore often the best compromise between wing mass and induced drag.

[0004] Against this background, it is known to support the wings with struts. This measure allows for a significantly higher aspect ratio while simultaneously reducing wing mass. The idea of ​​braced wings was already pursued in the 1950s. It has been revived more recently and is currently the subject of several research projects, including NASA's SUGAR program.

[0005] However, the struts also create additional drag, which is a disadvantage. A significant portion of this is due to interference drag occurring between the wing and the strut(s).

[0006] To reduce drag, the distance between the two components can be increased, according to the state of the art. For this purpose, the struts have a vertical offset at one wing-side end, so that they support the wing almost perpendicularly at the support point. However, with the support point remaining the same, this leads to a reduction in the strut's structural strength. This is because, in this known design, the strut must withstand not only tensile and compressive forces, but also bending moments caused by the kink near the support point. The structural measures to counteract this result in a thickening of the strut. This, in turn, leads to a detrimental increase in the strut's mass and drag.

[0007] On the other hand, it is known to equip the support point between the strut and the wing with a type of aerodynamic fairing to reduce parasitic interference between the strut and the wing. However, the fairing also introduces drag and mass. Furthermore, it reduces the lift-generating area of ​​the wing, which is associated with additional drag.

[0008] In conventional aircraft, the main wing is used as a fuel tank. Therefore, in most cases, the full potential of a strutted wing cannot be exploited. The available volume for kerosene storage in a wing decreases with increasing aspect ratio. This limitation can be mitigated if the fuel is stored in a different way – for example, in the fuselage or in external nacelles. For this reason, wing bracing is of particular interest for hydrogen-powered aircraft.

[0009] For hydrogen-powered aircraft concepts, fuel reduction is crucial not only from a resource and environmental perspective: Storing liquid hydrogen requires a tank volume more than three times that of kerosene. Especially for longer flights, the necessary tank sizes are incompatible with typical aircraft configurations, making fuel consumption essential. Furthermore, liquid hydrogen tanks have specific requirements, including material and thermal tightness, and typically require pressurization above 1 bar. Currently, only largely cylindrical, conical, or spherical aircraft tanks for liquid hydrogen are feasible. This means that the space often used for fuel storage in the wings is either unusable or only partially utilized, necessitating additional tank space and thus making fuel savings and tank volume reduction even more critical.Therefore, an optimized wing design is particularly important for the economically viable operation of hydrogen-powered aircraft.

[0010] To create additional tank volume, it is known to arrange the tanks outside the wings. However, in hydrogen aircraft designs, it is generally preferred to integrate the hydrogen tanks into the fuselage. From a structural and aerodynamic perspective, it is better to use a single fuselage for both the payload and hydrogen volume than to use multiple bodies for integration. Therefore, it is better to integrate all components into a larger fuselage than to have a smaller fuselage solely for the payload and two separate nacelles for hydrogen storage. Distributing volume across multiple separate bodies ultimately increases the overall surface area. On the other hand, decoupling fuel storage from the payload offers significant operational and safety advantages. This is evident, for example, during refueling, maintenance, in the event of leaks, or in the case of a crash.

[0011] US Patent 2,507,069 A also discloses an aircraft with multiple strut-braced wings, which has variable auxiliary fuel tanks arranged on the struts. However, the disclosed arrangement is extremely disadvantageous with regard to drag, both between the strut and the wing and at the external fuel tanks.

[0012] US Patent 9,493,246 B2 concerns a cryogenic tank structure within a braced wing. This wing structure also exhibits a detrimentally increased induced drag.

[0013] It is therefore an object of the invention to propose a stable wing structure for an aircraft which, while avoiding the disadvantages of the prior art with regard to structural mass, enables the space-saving integration of a hydrogen tank while simultaneously reducing the drag of the wings. It is a further object of the invention to propose a corresponding aircraft.

[0014] This problem is solved in a wing construction for an aircraft, comprising a wing having at least two half-wings and at least two struts, wherein the half-wings and the struts are connectable to an aircraft fuselage, wherein the half-wings are each supported at a respective support point by at least one strut, by arranging a tank between the half-wing and the strut supporting the half-wing, wherein the tank is arranged connecting the strut and the half-wing at a wing-side end of the strut at the support point.

[0015] In the invention, a strut is defined as an elongated support element for supporting the wing. Generally, its possible forms are known from the concept of strut-braced wings. The precise shape and its arrangement relative to the fuselage and wing depend on the exact wing and aircraft configuration. According to the invention, as a wing-supporting element, it is arranged below the supported wing, pointing towards the ground, when the wing structure is in operation. However, in principle, an arrangement of the wing and strut offset along the fuselage is also possible, so that the strut is not located directly below the wing. The invention also generally encompasses configurations in which the strut is arranged above the wing.

[0016] The struts each have a fuselage-side end, where they are connected to an aircraft fuselage during operation, and a wing-side end, where they are connected to the wing half to be supported. Due to the lower additional mass, narrow struts are particularly advantageous, whereby, when selecting the strut width, potential buckling caused by compression forces must be taken into account. The invention also extends, in principle, to so-called "truss-braced wings," which have one or more supports or reinforcements between the strut and the wing to prevent possible buckling of the struts in certain operating modes. The wing construction according to the invention can also be combined with twin-fuselage aircraft, in which case each wing, with a supporting strut, is arranged on an outer side of each fuselage facing away from the other fuselage.

[0017] In a special embodiment of the invention, the fuselage-side end of the strut is indirectly connected to the aircraft fuselage in the operating state, preferably via another component, in particular a landing gear structure, another fuel tank and / or a battery holder.

[0018] The generally known use of struts advantageously allows for the use of longer, narrower, and lighter wings, as they provide the necessary stability. According to the invention, the tank, arranged between the wing and the strut, enables better decoupling of the fuel storage from the payload (passenger cabin), since the tank volume is (at least partially) shifted outwards. Additionally, it increases the distance between the wing and the strut and provides shielding between these components where they are closest, thereby advantageously reducing their interference drag. The fuel storage thus simultaneously assumes the function of an aerodynamic fairing.

[0019] By connecting the strut to the wing via the tank, shorter strut lengths can be used.

[0020] Furthermore, the distance between the wing and the strut is greater, which advantageously reduces interference effects. Additionally, the tank allows for an increase in the strut's contact area with the wing, thereby reducing potential compression forces between the strut and wing under certain circumstances. This enables the advantageous use of narrower struts, and, depending on the precise wing and strut configuration, may even eliminate the need for additional supports or reinforcements between the strut and the wing. A person skilled in the art will determine the optimal configuration in each case through optimization calculations.

[0021] The invention thus creates several synergistic effects between the additional tank, the strut, and the wing, each with a positive impact on fuel consumption. While the additional external tank surface does cause parasitic drag, this can be at least partially compensated for by the aforementioned positive effects with a suitable configuration of the components. Furthermore, with regard to the generally known use of external tanks, the invention enables a more stable attachment of the tank through the additional connection to the aircraft fuselage via the strut.

[0022] In strut-type wings, the struts can advantageously also be used as airfoils. This reduces the amount of lift generated by the main wing. The main wing can therefore be made smaller. Distributing the lift across multiple airfoils further reduces induced drag. On the other hand, the interference drag between the main wing and the secondary strut-type airfoils can become more difficult to manage.

[0023] Furthermore, by arranging the tank at a wing-side end of the strut at a support point, shielding is achieved in an area that is particularly critical for induced drag.

[0024] Furthermore, in a further development of the invention, it is envisaged that the tank is a fuel tank, in particular a hydrogen tank, a liquid hydrogen tank, a kerosene tank, a synthetic kerosene tank or a liquid nitrogen tank, or that the tank contains batteries.

[0025] In this way, the advantageous wing design can be used with different drive types.

[0026] Furthermore, in an advantageous embodiment, it can be provided that at least one engine is arranged on each of the at least two half-wings, in particular a hydrogen-powered turboprop engine and / or a hydrogen-powered turbofan engine, which is arranged in particular between the wing and the strut.

[0027] This allows the wing design to be combined with a commonly used engine configuration. Of course, other common engine types can also be used in embodiments of the invention.

[0028] Furthermore, in an advantageous embodiment of the invention, the engine is arranged between the wing and the strut. This allows the engines to be positioned close to the aircraft's centerline. As is known, this is particularly advantageous for twin-engine or multi-engine aircraft, preventing uncontrolled yaw in the event of an engine failure.

[0029] Furthermore, in an embodiment of the invention, the tank can have a spherical, cylindrical, or conical shape and / or be thermally insulated. This allows the use of common liquid hydrogen storage tanks.

[0030] In a further development of the invention, it is also provided that the wing structure has a tank bracket, wherein the tank bracket is arranged to hold the tank on the wing.

[0031] According to the invention, the connection between the tank mount and the wing can be located either in front of or behind the tank. In another embodiment of the invention, a tank can be located both in front of and behind the connection between the tank mount and the wing, with both tanks preferably being insulated with a common foam thermal insulation that fills the shared nacelle. In principle, the invention also allows for multiple tanks to be arranged in a single nacelle, advantageously providing greater flexibility with regard to structural and aerodynamic properties as well as the position of the center of gravity.

[0032] This allows for a stable mounting of the tank to the wing. Regarding the material and weight of the tank mount, the expert will make an optimized choice between maximum stability and minimum mass. The external shape of the tank mount will be adapted to the tank in such a way as to achieve the greatest possible reduction in induced drag.

[0033] Furthermore, in an advantageous embodiment of the wing construction according to the invention, the tank mount is connected to the strut. This results in the most stable possible configuration of the elements involved.

[0034] Furthermore, in this embodiment of the invention, the wing and the at least one strut supporting it each have additional connection points via supports or reinforcements. This additionally supported wing-strut configuration corresponds to the so-called truss-braced wing configuration, which allows for better compensation of compression forces acting on the strut.

[0035] The problem with regard to the proposed aircraft is solved according to the invention in an aircraft having an aircraft fuselage by the fact that the aircraft fuselage is connected to a wing structure according to one of claims 1 to 7.

[0036] In this way, an aircraft with the aforementioned positive effects of the suitable combination of an outwing tank and the desired wing design is proposed. Outwing tanks offer increased safety as well as advantages with regard to maintenance, particularly due to easier accessibility. These advantages favor an aircraft with outwing tanks, although integrating the tanks into the fuselage, along with the payload, is generally simpler from a technical standpoint and more aerodynamic.

[0037] In a further development of the invention, the aircraft fuselage is connected to several wing structures, wherein at least one of the wing structures is configured according to one of claims 1 to 7. For example, the aircraft fuselage can be connected to two wing structures, only one of which is configured according to claims 1 to 7. The second wing structure may, for example, not be braced within the scope of the invention.

[0038] In one embodiment of the invention, the aircraft can have a propulsion system based on kerosene and / or hydrogen and / or liquid hydrogen and / or fuel cells.

[0039] This means that the advantageous fuel optimization achieved by the wing design according to the invention can be used both in aircraft with conventional, kerosene-based engines and, in particular, in those with climate-friendly hydrogen or fuel cell-based engines.

[0040] The invention is described in a preferred embodiment by way of example with reference to a drawing, further advantageous details of which can be seen in the figures of the drawing.

[0041] Functionally identical parts are marked with the same reference symbols.

[0042] The figures in the drawing show, in detail: Fig. 1: A schematic diagram of an aircraft with a wing structure according to the invention Fig. 2: A computer model of an aircraft according to the invention.

[0043] In the Fig. Figure 1 shows a cross-section of an aircraft 1 with a wing structure according to the invention in a sketched representation. The aircraft 1 has a fuselage 2. The cross-section of the fuselage 1 can be widened in a lower area 14, which, when stationary, points towards the ground, for better connection to struts 4, as shown in the sketch. A widening is also possible in an opposite upper area 15, on which two half-wings 3 are arranged in a mirrored configuration. The invention is not limited to the arrangement of the half-wings 3 and the struts 4 on the fuselage 2 shown; the half-wings 3 can also be arranged in a middle or lower area of ​​the fuselage. The exact configuration is selected by those skilled in the art to optimize it depending on the aircraft type, application, propulsion system, flight path, etc.In the illustrated embodiment, the aircraft 1 has two half-wings 3, each supported by a strut 4. A support point 7, at which the half-wing 3 is supported by the strut 4, is formed within a tank 5 located below the respective half-wing 3. In this case, the support point 7 is designed as an enlarged support surface. This surface is formed by the area where the tank 5 intersects the half-wing 3. It can be further enlarged by a tank bracket 8, which may be arranged on the half-wing 3, to support the tank 5. The support point 7 divides the half-wing 3 into an inner wing 11 and an outer wing 12. The respective ratio of the lengths of the inner and outer wings 11 and 12, as well as the length of the respective strut 4 and the angle at which a fuselage-side end 10 of the strut is connected to the aircraft fuselage 2, are specified in the diagram.The position of the wing-side end 9 of the strut 4 relative to the half-wing 3 is also dependent on the respective aircraft configuration.

[0044] The increase in the distance between the strut 4 and the half-wing 3, as described in the invention, via the integration of the tank 5, reduces the interaction between the components, particularly the formation of vortices and the like, and thus also the interference drag between the strut 4 and the wing 3. This is achieved in particular by preventing the formation of an acute angle between the wing 3 and the strut 4, in which vortices are most likely to occur. It is also possible to select a larger angle between the fuselage-side end 10 and the aircraft fuselage 2, which generally increases the space between the wing 3 and the strut 4. In the embodiment shown, an engine 6 is arranged between the strut 4 and the wing 3.

[0045] The Fig. Figure 2 shows an exemplary computer model of an aircraft 1 according to the invention. The aircraft 1 has a fuselage 2. Two half-wings 3 and struts 4 are arranged mirrored on the fuselage approximately in a central region of its length. The struts 4 are arranged such that they support the half-wings 3. In the embodiment shown, the width of the struts 4 is only slightly reduced compared to the width of the half-wings 3. Narrower struts 4, which have less than half, less than one-third, or less than one-fifth the width of the wings 3, are also according to the invention. These thinner struts are sometimes additionally connected to the wing 3 by means of supports not present in the illustrated embodiment.

[0046] The fuselage 2 is widened in an upper area 15 and in a lower area 14. This enables a stable connection of the half-wings 3 or the struts 4 to the fuselage 2.

[0047] A tank 5 is arranged at each wing-side end 8 of the struts 4. This tank connects the strut 4 to the half-wing 3, thus creating a support point within the tank 5, or rather within the intersection of the tank 5 and the half-wing 3, as a section surface. Force is transmitted between the two components via the support point 7 or the support surface. The tank has the shape of an acute ellipsoid. The wing 3 and the strut 4 are arranged approximately midway along a length of the ellipsoid. The aircraft configuration shown has two half-wings, each arranged and attached to an inner wing 11 between the wing 3 and the strut in a manner known per se. REFERENCE MARK LIST 1 airplane 2 aircraft fuselages 3 wings 4 strut 5 Tank 6 engines 7 Support point 8 Tank bracket 9 wing-side end 10 hull-side end 11 inner wing 12 outer wing 13 14 lower area 15 upper area

Claims

Wing structure for an aircraft (1), comprising a wing having at least two half-wings (3) and at least two struts (4), wherein the half-wings (3) and the struts (4) are connectable to an aircraft fuselage (2) of an aircraft (1), wherein the half-wings (3) are each supported at a respective support point (7) by at least one strut (4), wherein a tank (5) is arranged between the half-wing (3) and the strut (4) supporting it, wherein the tank (5) is arranged connecting the strut (4) and the half-wing (3), characterized in that the tank (5) is arranged at a wing-side end (9) of the strut (4) at the support point (7). Wing construction according to claim 1, characterized in that the tank (5) is a fuel tank, in particular a hydrogen tank, a liquid hydrogen tank, a kerosene tank, a synthetic kerosene tank or a liquid nitrogen tank and / or that the tank (5) contains batteries. Wing construction according to claim 1 or 2, characterized in that at least one engine (6) is arranged on each of the at least two half-wings (3), in particular a hydrogen-powered turboprop engine and / or a hydrogen-powered turbofan engine, which is arranged in particular between the wing (3) and the strut (4). Wing construction according to one of the preceding claims, wherein the tank (5) has a spherical, cylindrical or conical shape and / or wherein the tank has thermal insulation. Wing construction according to one of the preceding claims, characterized in that it has a tank bracket (8), wherein the tank bracket (8) is designed to hold the tank (5) on the wing (3). Wing construction according to claim 5, characterized in that the tank support (8) is connected to the strut (4). Wing construction according to one of the preceding claims, characterized in that the wing (3) and the at least one strut (4) supporting the wing (3) each have additional connection points via supports or reinforcements. Aircraft (1) comprising an aircraft fuselage (2), characterized in that the aircraft fuselage (2) is connected to one or more wing structures, wherein at least one of the wing structures is designed according to one of the preceding claims. Aircraft (1) according to claim 8, characterized in that the aircraft fuselage (2) is connected to several wing structures, wherein at least one of the wing structures is designed according to one of claims 1 to 7. Aircraft (1) according to claim 8 or 9, wherein it has a propulsion system based on kerosene and / or hydrogen and / or liquid hydrogen and / or fuel cells.

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