The cup wing A fluid dynamic profile for generating lift with significantly reduced drag, for example for aircraft wings and propeller blades

Abstract

When generating lift - for example in aircraft wings, rotor blades of helicopters and drones, propeller blades and turbine blades - one wants high lift with low drag. In aircraft, turbulence must also be avoided - especially at the wing tips - which, on the one hand, counteracts lift and, on the other hand, can lead to dangers for following air traffic. Thanks to a design that has not yet been used in technology, the cup wing enables high lift with comparatively low drag, while at the same time avoiding edge vortices and utilizing the otherwise turbulent air for further lift.

Description

State of the art

[0001] The profiles of wings, propellers, etc., typically generate lift through the flow of air against an aerodynamic profile, which, depending on the intended use, is characterized by thickness, camber, and angle of incidence, among other factors. The aerodynamic principles formulated by Newton and Bernoulli are used in this process.

[0002] Lift is generated partly by the pressure difference between the top and bottom surfaces of the airfoil, which is characterized by the specific combination of thickness, camber, and other parameters. Secondly, at a certain angle of attack, air hits the bottom of the airfoil and is deflected downward, which in turn lifts the airfoil. Example

[0003] In the case of an aircraft wing, the generation of lift can be thought of as Fig. 1. The static pressure on the upper surface decreases due to its curvature, pulling the wing upward. The underside is lifted independently by the impacting air particles. Disadvantages

[0004] Due to the thickness of typical aerodynamic profiles, the impacting air particles always have a relatively large surface area to bounce off, thereby slowing forward motion. Thus, lift is always counteracted by a comparatively high resistance.

[0005] Some of the impacting air particles - for example at the leading edge or, at an increased angle of attack, at the underside - are caused to change direction abruptly, which in turn leads to vortices and drag.

[0006] The pressure difference between the upper and lower surfaces of the wing also creates tip vortices, which significantly counteract the lift and - in the case of aircraft wings - can also pose a significant threat to following air traffic. Counter-representations

[0007] The prior art includes applications that show similarities to the solution presented below or one of its variations. However, the continuous increase in curvature towards the rear and to the sides, characteristic of the calyx wing, in combination with a very small thickness, has apparently not yet been applied in industry. US 9 145 198 B1 Here, an adjustment mechanism for wing flaps is patented to enable a quick and efficient change in camber. However, the nature of a specific wing profile is not the subject of the invention. Nor is any lift generation principle deviating from the standard applied. DE 103 17 258 A1 This also concerns an adjustment mechanism—in this case for adjusting several surfaces that can be pivoted relative to each other. The patent provides no information about the shape and lift principle of the wing to be equipped with this mechanism. EP 2 423 104 A1 Here, too, a special implementation for changing the camber of a wing is patented, but without involving any innovation regarding shape and lift principle. US 2009 / 0 224 102 A1 Here, a combination of wing and fuselage is presented, in which the wing is comparatively thin and shaped to avoid structural impairments. The motivation is stability with minimal material usage. This also requires a curvature of the Profile. However, a strictly monotonically increasing curvature like that of a calyx wing is not required—especially not to the rear and sides. A buoyancy principle deviating from the standard is not pursued. Solution

[0008] In contrast to a conventional wing, the cup-shaped wing is comparatively thin across its entire profile. It must be as thick as required by design to ensure sufficient stability, but not necessarily thicker. The thickness can, but does not have to, change along the profile. This offers significantly less drag to the oncoming air than a traditional profile. Towards the rear, the wing is increasingly curved downwards. This gently and slowly deflects the oncoming air downwards. It uses Newton's principle of lift, not Bernoulli's: the deflection of the air creates the action, and the counteraction creates lift on the wing.

[0009] Vortex formation caused by abrupt changes in the direction of air particles - such as at the leading edge of a conventional wing or its lower edge at an increased angle of attack - is thus largely avoided. Fig. Figure 2 shows such a profile (thick line) from the side as well as the air flowing towards it and deflected by it to generate lift (thin arrows).

[0010] The rearward camber continues toward the wing tips, so that the air flowing away to the sides is also deflected downward and used to generate lift. At the same time, this counteracts the formation of counterproductive and dangerous tip vortices. Fig. Figure 3 shows the section of an aircraft wing moving towards the observer and on the right side (thick line) with the air trying to equalise pressure and therefore flowing off to the right side (thin arrows).

[0011] It should be noted that this type of lift generation can cause a pitching moment in the aircraft, which can be compensated for by means of elevator deflection or by design measures - such as attaching the wings further forward on the fuselage than usual. Example

[0012] In a simple version, the calyx wing can be imagined as an upside-down antique chalice or Frisbee, cut vertically in half approximately in the middle (or at least some distance from the edge), leaving only the smaller part. The cut surface forms the leading edge of the wing, and the curvature extends downwards both backward and laterally. Fig. 4 - 7 show an aircraft that uses the cup-shaped wing profile as a wing. Fig. Figure 7 illustrates how a simple calyx wing can be shaped. Advantages 1. The lift is counteracted by a significantly reduced drag. 2. Air turbulence caused by abrupt changes in the direction of air particles is greatly reduced. 3. The air flowing away to the side is also used to generate lift. 4. Edge vortices are counteracted, which brings the following advantages 1. Increased safety for following traffic 2. Further increase in lift, as the surface is not pushed downwards by incoming wake vortices.

[0013] This will 1. a much more energy-efficient and therefore more economical and ecologically sustainable way of flying is possible 2. increases air traffic safety 3. increases the capacity utilisation and profitability of airports, which can increase departure frequencies by reducing wake turbulence. 4. The airspace can potentially be used more effectively because parts of the airspace can now be used that were previously inaccessible due to wake turbulence. Variation optionsShaping

[0014] The basic shape described above can be varied as desired, as long as the profile in the normal configuration is characterized by a curvature that increases towards the rear and to the sides. Arrowing

[0015] The wingtips of a cup-shaped wing are naturally subject to higher loads than those of conventional wings, as they are also used to generate lift. This can be counteracted by negatively sweeping the trailing edge of the wing, which causes at least some of the air flowing off laterally to also flow over the trailing edge of the wing. Fig. 8 and Fig. 9 shows two possible variants. Advantage

[0016] The formation and effects of edge vortices – especially on drag – are counteracted to the maximum. Variable curvature

[0017] If the camber on the rear side of the wing or parts of it (flaps) is made variable and controllable, the lift can be regulated as desired. This allows the function of both flaps and ailerons to be performed – depending on whether the camber is applied in the same or opposite direction on both sides.

[0018] For use as an aircraft wing, the cambers on both sides of the wing should be independently controllable to enable coordinated turning.

[0019] A variable curvature can be realized - either completely or at least approximately - e.g. by using 1. of Fowler valves 2. of similar flaps or entire trailing edges of the wing, which - like Fowler flaps - consist of several segments, but do not need to be extended, but simply deflect towards each other in such a way that an approximately increasing camber is achieved towards the rear. This can be achieved, for example, by means of segment surfaces with a decreasing length towards the rear ( Fig. 10) or by those which, the further they are located at the wing tip, deflect more strongly than those in front. 3. a flexible material that, when bent, bends more towards the wing tip ( Fig. 11).

[0020] The camber at the wing tips does not need to be varied, or not too much, because whenever lift is generated, a pressure difference also occurs, which seeks compensation at the wing tip and produces tip vortices if the airflow is not redirected. Advantages • The buoyancy can be continuously adjusted • The angle of attack does not need to be changed to increase lift, which results in better visibility during climb and landing and therefore significantly greater safety. • Virtually any aircraft can be provided with short takeoff and landing (STOL) capabilities. transition edge

[0021] At the end and tips of the profile, the downwardly deflected airflow merges into the regular airflow. At this point, higher-pressure air below the profile meets lower-pressure air above it. This can cause vortices to form again, especially when the airfoil is highly lifted due to strong camber. This can be counteracted by a transition edge that gently redirects the airflow slightly back in the direction it would otherwise flow, while preventing the airflows above and below the profile from converging too early. This also reduces these vortices.

[0022] The edge can be rigid, made of a flexible material, or consist of several or - as in the case of a bird's feathers - many flexible or partially flexible elements. Fig. 12 shows, as an example, the section through a cup-wing profile with a transition edge attached to its rear edge. Areas of application: Wing for aircraft

[0023] When designing this profile, the first thing that was considered was aircraft wings in order to enable energy-efficient lift. Propeller and rotor blades and compressor blades

[0024] Propeller blades (e.g. for aircraft or fans), helicopter rotors, ship propellers and compressor blades in turbine engines can also be constructed according to the cup-shaped wing principle in order to optimize performance and thereby enable higher throughput and / or lower energy consumption and, furthermore, to minimize the impact on the environment through vortex formation, except in the case of compressor blades.

[0025] The leading edge of the wing must point in the direction of rotation. Turbines

[0026] In turbines, cup-shaped blades can be used to optimize fluid flow utilization. The leading edge of the blade must point straight in the direction of the incoming fluid.

Claims

[1] Fluid dynamic profile, characterized by that it is curved downwards towards the rear and to the sides to generate lift. [2] Fluid dynamic profile according to claim 1, characterized by that its curvature is achieved in several steps, e.g. several consecutive and angled surfaces. [3] Fluid dynamic profile according to claim 1, characterized by that its trailing edge is negatively swept and its wing tips are shortened. [4] Fluid dynamic profile according to claim 1, characterized by that the strength of its curvature can be varied, for example by designing the trailing edges of the wing or parts of it (flaps) from 4.1 several links whose angle to each other can be changed by targeted control 4.2 a flexible material provided with a device by means of which the curvature described can be achieved and its intensity can be varied. [5] Fluid dynamic profile according to claim 1, characterized by that a transition edge curved or capable of being curved in the opposite direction to the profile camber is attached to the trailing edge and tips of the profile in order to counteract the further formation of vortices. [6] Fluid dynamic profile according to claim 1, characterized by that it can be used as 6.1 Wing 6.2 Propeller blade (e.g. for aircraft propellers, helicopter rotors, drone rotors, compressor blades in turbine engines, fans) 6.3 Propeller blade 6.4 Turbine blade

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