Flow body for an aircraft with a selectively activatable shock bump

Abstract

A flow body for an aircraft includes a skin having a first flow surface, having a flow influencing section with at least one first layer, at least one separator layer, at least one third layer, and at least one base layer. The first layer includes lithiated carbon fibers embedded into a matrix to form a negative electrode. The third layer includes carbon fibers with an electrode active material coating to form a positive electrode. The separator layer includes a non-conductive material for electrically isolating the first layer and the third layer from each other. The flow influencing section is configured for selectively raising a region of the arrangement of first layer, separator layer and third layer from the base layer upon application of a voltage between the first and third layers to form a bump on the flow body.

Claims

1. A flow body for an aircraft, the flow body comprising an outer skin having a first flow surface, wherein the skin comprises at least one flow influencing section on the first flow surface, the flow influencing section comprising: at least one first layer comprising a first fiber composite material; at least one separator layer; at least one third layer comprising a second fiber composite material; and at least one base layer comprising a third fiber composite material, wherein the at least one first layer, the at least one separator layer and the at least one third layer are arranged upon the at least one base layer in an alternating order, wherein the at least one first layer comprises lithiated carbon fibers embedded into a matrix to form a negative electrode, wherein the at least one third layer comprises carbon fibers with an electrode active material coating to form a positive electrode, wherein the at least one separator layer comprises a non-conductive material for electrically isolating the at least one first layer and the at least one third layer from each other, and wherein the flow influencing section is configured for selectively raising at least a region of the arrangement of first layer, separator layer and third layer from the at least one base layer upon application of a voltage between the first layer and third layer to form a bump on the flow body.

2. The flow body of claim 1, wherein the flow influencing section has a fixed position on the flow body and is configured to expand upon application of the voltage, such that the flow influencing section buckles away from the at least one base layer.

3. The flow body of claim 1, wherein the separator layer comprises a glass fiber reinforced plastics material.

4. The flow body of claim 1, wherein the separator layer comprises carbon fibers having an electrically isolating coating.

5. The flow body of claim 1, wherein the electrode active material coating comprises LiFePO.sub.4.

6. The flow body of claim 1, wherein at least two edges of the flow influencing section that are opposed along an extension direction are fixated to the base layer.

7. The flow body of claim 6, wherein along the at least two edges, the first, separator and third layers are sewn or stitched to layers underneath before a curing process.

8. The flow body of claim 1, wherein the first, separator and third layers of the respective flow influencing section are separated from material layers underneath through a friction reducing coating or layer.

9. The flow body of claim 1, wherein the at least one flow influencing section includes at least two flow influencing sections, which at least partially overlap and which are individually and selectively actuatable to morph the bump from a neutral state to a plurality of different shapes.

10. An aircraft having at least one flow body according to claim 1.

11. The aircraft of claim 10, wherein the flow body is at least one of a group of flow bodies, the group comprising: a wing, a vertical tailplane, a horizontal tailplane, at least a part of a blended wing body, a fuselage, and a fairing.

12. The aircraft of claim 10, further comprising a control system and a voltage source coupled with the control system, wherein the at least one first layer and the at least one third layer are selectively couplable with the voltage source through the control system.

13. The aircraft of claim 12, wherein the aircraft comprises a velocity sensor, and wherein the control system is coupled with the velocity sensor to selectively apply a voltage to the at least one first layer and the at least one third layer upon reaching or exceeding at least one threshold velocity.

14. A method for producing a flow body for an aircraft, the method comprising: laying at least one base layer onto a surface of a molding tool; creating a flow influencing section on the at least one base layer by laying at least one first layer comprising a first fiber composite material onto the base layer, laying at least one separator layer onto the first layer, laying at least one third layer comprising a second fiber composite material onto the separator layer, and fixing the first layer, the separator layer and the third layer onto the base layer, impregnating the arrangement of layers with a matrix material, and curing or hardening and removing the flow body from the molding tool, wherein the at least one first layer comprises lithiated carbon fibers embedded into a matrix to form a negative electrode, wherein the at least one third layer comprises carbon fibers with an electrode active material coating to form a positive electrode, and wherein the at least one separator layer comprises a non-conductive material for electrically isolating the at least one first layer and the at least one third layer from each other.

15. The method according to claim 14, wherein the fixing is conducted by stitching or sewing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Other characteristics, advantages and potential applications of the present invention result from the following description of the exemplary embodiments illustrated in the figures. In this respect, all described and/or graphically illustrated characteristics also form the object of the invention individually and in arbitrary combination regardless of their composition in the individual claims or their references to other claims. Furthermore, identical or similar objects are identified by the same reference symbols in the figures.

(2) FIG. 1 shows a prior art wing with schematically indicated supersonic flow on the top surface.

(3) FIG. 2 a schematic overview of a flow influencing section is shown with and without a shock bump.

(4) FIG. 3a shows the flow influencing section in another view.

(5) FIG. 3b shows the relationship between voltage and elongation.

(6) FIGS. 4a and 4b show two flow influencing section overlapping each other.

(7) FIGS. 5a to 5c show aspects of a manufacturing method.

(8) FIG. 6 shows an aircraft having a flow body with a flow influencing section.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

(9) FIG. 1 shows a schematic overview of a prior art wing 2 for an aircraft having a leading edge 4 and a trailing edge 6, between which a top surface 8 and a bottom surface 10 extend. In some circumstances, on a region of the top surface 8, a supersonic flow may occur, even when the wing 2 travels only with subsonic velocity. By using a bump 12 at a specific location, a separation of flow may be reduced or even completely prevented. However, the bump 12 maintains a fixed shape and position, which may lead to an increased drag compared to a wing without such a bump 12.

(10) FIG. 2 shows an overview of a flow influencing section 14 on a flow body 16 according to an aspect of the invention. It comprises several base layers 18 made of a base fiber composite material. This may include carbon fibers embedded into a matrix material, such as heat curable resin or a thermoplastics material. On top of the top base layers 18, a friction reducing coating 20 is provided. This may include PTFE or another suitable material.

(11) On top of the friction reducing layer 20, a first layer 22 of a first fiber reinforced composite material is placed. Said material comprises lithiated fibers embedded into a matrix material, which is preferably the same as in the base layers 18. By lithiating the carbon fibers, a negative electrode is formed that is capable of releasing Lithium ions.

(12) On top of the first layer 22, a separator layer 24 is placed, which is a second layer in this arrangement. It is made of an electrically isolating material, which is permeable for Lithium ions. For example, it may be a fiber reinforced plastic material that comprises glass fibers embedded into a matrix material. As an alternative, it may also comprise carbon fibers having an electrically isolating coating. Again, the matrix material may be the same as in the first layer 20 and the base layers 18.

(13) On top of the separator layer 24, a third layer 26 of a third fiber reinforced composite material is placed. This layer 26 exemplarily comprises carbon fibers coated with an electrode active material, such as LiFePO.sub.4. It is capable of receiving Lithium ions and acts as a positive electrode.

(14) Together, the first layer 22 and the third layer 26 comprise the same structural stability as the base layers 18, but together act as a piezo actuator upon application of a voltage from a voltage source 28. Due to the piezo effect, the first layer 22, the separator layer 24 and the third layer 26 expand and buckle away from the base layers 18, as shown in the lower part of FIG. 2. Resultantly, they create a bump 29. To increase this effect, further layers can be attached. For example, on top of the third layer 26, a further separator layer 24 can be arranged, which is followed by a first layer 22 and so on. With selected mechanical and electrical parameters the bump 29 may have substantially the same shape as the bump 12 shown in FIG. 1. The first layers 22, the separator layers 24, the third layers 26 and the base layers 18 together form an outer skin 27 of the respective flow body 16.

(15) The voltage source 28 may be coupled with a control system 25, which is configured to connect the flow influencing section 14 to or disconnect it from the voltage source 28 to activate or deactivate the bump 29. Further, it may be configured to modulate the voltage applied to the flow influencing section in order to modulate the strength of the bump 29. The control system 25 may further be coupled with a velocity sensor of the aircraft to selectively apply a voltage to the flow influencing section 14 upon reaching or exceeding at least one threshold velocity to prevent an undesired flow separation. As stated before, several threshold values may be predetermined, which may lead to initiating different strengths or shapes of the bump.

(16) FIG. 3 a shows a section of the flow influencing section 14 in another view. Here, exemplarily reinforcement fibers 30 extend along an x-axis. By application of the voltage they extend along the x-direction.

(17) The relationship between voltage and elongation is shown in FIG. 3b. Here, a voltage is shown with a solid line, while a resulting elongation of the arrangement of FIG. 3a is shown with a dashed line. It is apparent, that both parameters are substantially proportional. This also means, that a bump 29 formed with the flow influencing section 14 can be modulated by the voltage applied to the layers 22 and 26.

(18) In FIGS. 4a and 4b, a further exemplary embodiment is shown, where two flow influencing sections 14a and 14b are provided on the base layers 18. They overlap each other partially, such that the flow influencing section 14b is arranged on top of the flow influencing section 14a. Consequently, the shape of the bump 29 along the x-direction can be modulated.

(19) It is apparent, that the upper flow influencing section 14b is fixed to the lower flow influencing section 14a along opposed edges 32 and 34. The lower flow influencing section 14a in turn fixed to the base layers 18 with a fixation along opposed edges 36 and 34. These may resemble a stitching line through a laminate created by the layers 18, 22, 24 and 26, said stitching lines clearly geometrically delimiting the individual flow influencing sections 14a and 14b and prevent a peeling off from the base layers 18. Both flow influencing sections 14a and 14b can individually be coupled with the voltage source 28, such that the size of each of them can be modulated individually. This may be conducted by the control system 25 shown in FIG. 2.

(20) FIGS. 5a, 5b and 5c exemplarily show aspects of a method for manufacturing the flow body 16. FIG. 5a shows a number of base layers 18 on a molding tool 38. Here, a placement tool 40 places a friction reducing coaching twins he to the base layers 18.

(21) In FIG. 5b, the arrangement of first layer 22, separator layer 24 and the third layer 26 is arranged on the base layers 18. A stitching device 42 prepares holes 44 through the laminate. FIG. 5c shows a sewing process by the stitching device 42. Here, exemplarily fixations 34 and 36 are provided, which delimit the extension of the flow influencing section 14.

(22) FIG. 6 shows an aircraft 46 having wings 48, a vertical tailplane 50, horizontal tailplanes 52 and a fuselage 54. Exemplarily, the wings 48, as a flow body, each comprise a flow influencing section 14 indicated with a dashed line on a first flow surface 56. The first flow surface 56 in this case is a top surface of the respective wing 48 at least partially created by the outer skin 27.

(23) In addition, it should be pointed out that “comprising” does not exclude other elements or steps, and “a” or “an” does not exclude a plural number. Furthermore, it should be pointed out that characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments described above. Reference characters in the claims are not to be interpreted as limitations.

REFERENCE NUMERALS

(24) 2 wing (prior art) 4 leading edge 6 trailing edge 8 top surface 10 bottom surface 12 bump 14 flow influencing section (also: 14a, 14b) 16 flow body 18 base layer 20 friction reducing 22 first layer 24 separator layer (second layer) 25 control system 26 third layer 27 outer skin 28 voltage source 29 bump 30 reinforcement fiber 32 edge 34 edge 36 edge 38 molding tool 40 placement tool 42 stitching device 44 hole 46 aircraft 48 wing 50 a vertical tailplane 52 horizontal tailplane 54 fuselage 56 first flow surface