Aerodynamics improvement device for an aircraft and aircraft equipped with such device

Abstract

An aircraft (5) including an aerodynamic surface (6), an aerodynamics improvement device with a first electrode (27) embedded beneath and electrically isolated from the aerodynamic surface (6), a second electrode (28) electrically isolated from the first electrode (27), a voltage generator (30) adapted to apply a voltage between the first and the second electrode, further comprising a layer of electrically insulating material (26) between the second electrode (28) and the aerodynamic surface (6). Methods for detecting ice on and de-icing an aerodynamic surface (6), and for delaying a boundary layer transition and separation from the aerodynamic surface.

Claims

1. An aircraft including: an aerodynamic surface including an outer exposed surface adapted to be exposed to atmospheric air flowing over the aircraft; a first group of electrodes embedded in the aerodynamic surface and separated by an insulating layer from the outer exposed surface of the aerodynamic surface, wherein the first group of electrodes includes at least one first electrode and at least one second electrode electrically isolated from the at least one first electrode; a second group of electrodes separate from the first group and embedded in the aerodynamic surface and separated by the insulating layer from the outer exposed surface of the aerodynamic surface, wherein the second group of electrodes includes at least one third electrode and at least one fourth electrode electrically isolated from the at least one third electrode; and a voltage generator electrically connected to the first group to apply a de-icing voltage across the first and second electrodes, and connected to the second group to apply an ionizing voltage across the third and fourth electrodes; wherein the application of the de-icing voltage across the first and second electrodes de-ices the aerodynamic surface proximate to the first and second electrodes, and wherein the application of the ionizing voltage across the third and fourth electrodes ionizes air above the aerodynamic surface proximate to the third and fourth electrodes.

2. The aircraft according to claim 1, wherein the voltage generator is configured to apply the ionizing voltage as an anti-stall voltage across the third and fourth electrodes, wherein the ionizing voltage is different than the de-icing voltage.

3. The aircraft according to claim 1, wherein the first group of electrodes is embedded in a leading edge of a wing, a horizontal tail plane or a vertical tail plane.

4. The aircraft according to claim 1, wherein the second group of electrodes is embedded in a fore portion of an upper surface of a wing, horizontal tail plane or a vertical tail plane, and the second group is aft along a chordwise direction of a leading edge of the aerodynamic surface.

5. The aircraft according to claim 1, further comprising a third group of electrodes separate from and aft, along a chordwise direction of the aerodynamic surface, of both the first group and second group, and the third group is embedded in the aerodynamic surface, is separated by the insulating layer from the outer exposed surface of the aerodynamic surface, and the third group includes at least one fifth electrode and at least one sixth electrode electrically isolated from the at least one fifth electrode, wherein the voltage generator is electrically connected to the third group to apply a second ionizing voltage across the fifth and sixth electrodes.

6. The aircraft according to claim 5, wherein the application of the second ionizing voltage across the fifth and sixth electrodes ionizes air above the aerodynamic surface to create flow perturbations in a flow of air over the aerodynamic surface proximate to the third group of electrodes to delay separation of a boundary layer of the flow of air along the aerodynamic surface.

7. The aircraft according to claim 1, wherein, at low angles of attack of the aircraft, the voltage generator is configured to apply an anti-stall voltage, different from the ionizing voltage, across the third and fourth electrodes.

8. The aircraft according to claim 7, wherein the voltage generator is configured to apply the anti-stall voltage across the first and second electrode while the aircraft is flying at a high angle of attack.

9. The aircraft according to claim 1, further comprising an ice detection device configured to: measure a permittivity current between said first electrode and said second electrode while a permittivity voltage is applied across the first electrode and the second electrode, and based on the measured permittivity current, compute a permittivity value representative of an electrical permittivity between said first electrode and said second electrode.

10. The aircraft according to claim 9, further comprising a controller configured to control the voltage generator to alternatively apply between the first and second electrodes a permittivity voltage and an ionizing voltage.

11. The aircraft according to claim 1, further comprising a metallic mesh applied to the aerodynamic surface; wherein at least one electrode from the first group of electrodes or the second group of electrodes is included in the metallic mesh.

12. The aircraft according to claim 1, wherein the at least one first electrode has a comb shape.

13. The aircraft according to claim 12, wherein the at least one first electrode includes a series of first tips and the at least one second electrode includes a series of second tips, wherein the first and second tips are oriented in a forward facing chordwise direction.

14. The aircraft according to claim 1, wherein the at least one second electrode has a comb shape.

15. A method for detecting the ice on an aerodynamic surface of an aircraft comprising: applying a permittivity voltage across two electrodes electrically isolated from each other and embedded in the aerodynamic surface, measuring a current flowing between the two electrodes in response to the permittivity voltage applied to the two electrodes, detecting a change in electrical permittivity between the two electrodes based on the detecting a change in the measured current flow, and generating a signal indicating presence of ice in response to the change in electrical permittivity meeting a certain criterion.

16. The method according to claim 15, in which the permittivity voltage is applied intermittently between the two electrodes and further comprising, between successive applications of the permittivity voltage to the two electrodes, applying an ionizing voltage to ionize air above the aerodynamic surface proximate to the two electrodes.

17. A method comprising: applying a de-icing voltage between first and second electrodes embedded in an aerodynamic surface, wherein the first electrode is electrically isolated from the second electrode and the application of the de-icing voltage de-ices the aerodynamic surface, and applying an ionizing voltage between third and fourth electrodes embedded in the aerodynamic surface aft of the first and second electrodes in a chordwise direction of the aerodynamic surface, ionizing air flowing over the aerodynamic surface proximate to the third and fourth electrodes by the application of the ionizing voltage between the third and forth electrodes, wherein the third electrode is electrically isolated from the fourth electrode and the ionizing voltage differs from the de-icing voltage.

18. The method according to claim 17, further comprising, at low angles of attack of the aircraft, applying: the de-icing voltage across the first and second electrodes, and an anti-stall voltage, different from the de-icing voltage, across the third and fourth electrodes.

19. The method according to claim 18, further comprising, at high angles of attack of the aircraft, applying an anti-stall voltage across the first and second electrodes.

20. The method according to claim 17, wherein the application of the ionizing voltage includes applying the ionizing voltage at an ionizing frequency.

Description

SUMMARY OF DRAWINGS

(1) Some specific exemplary embodiments and aspects of the invention are described in the following description in reference to the accompanying figures.

(2) FIG. 1 is a schematic representation of a cross-section of a portion of a wing of an aircraft and electrical components housed within the wing.

(3) FIG. 2 is a representation of a horizontal tail plane of an aircraft.

(4) FIG. 3 is a perspective representation of a section of a horizontal tail plane of an aircraft.

(5) FIG. 4 is a cross-section representation of leading edge of a wing of an aircraft.

(6) FIG. 5 is a perspective representation of an aircraft.

DETAILED DESCRIPTION

(7) In FIG. 1, a portion of a wing 8 is represented. It comprises a structural layer 25 supporting the loads of the wing. The structural layer 25 forms a part of the skin of the wing 8 and comprises an outer surface providing for an outer shape of the wing. It further comprises an electrically isolating layer 29 on the outer surface of the structural layer 25 with the function of preventing the electrical connection between the electrodes 27 and 28 through the structural layer 25. The structural layer may for example comprise carbon fiber-reinforced polymer.

(8) It comprises an additional external anti-erosion and electrically insulating layer 26 over the electrically isolating layer 29. The anti-erosion layer 26 is adapted to be resistant to erosion, in particular to air, sand and water erosion, while remaining light.

(9) The outer surface of the anti-erosion layer 26 forms the aerodynamic surface 6 of the wing 8.

(10) The anti-erosion layer 26 is also electrically insulating. The material of the anti-erosion layer 26 is beneficially chosen from the electrically insulating materials. The anti-erosion layer 26 may be made in a polymer such as a polyurethane for example.

(11) Additional layer(s) (not-represented) of paint or surface treatments may be added to the anti-erosion layer 26.

(12) The aircraft of which a part is schematically represented on FIG. 1 comprises an aerodynamics improvement device according to the invention.

(13) The aerodynamics improvement device comprises a first electrode 27 and a second electrode 28. Both the first electrode 27 and the second electrode 28 are embedded in the anti-erosion layer 26. The first electrode 27 and the second electrode 28 are thus separated and electrically insulated from the aerodynamic surface 6 by a portion of the anti-erosion layer 26. The first electrode 27 and a second electrode 28 are not exposed to the environment of the aircraft, and do not form part of the aerodynamic surface 6.

(14) The first electrode 27 and the second electrode 28 are separated from each other by a gap 12 adapted to ensure a sufficient electrical insulation between the first electrode and the second electrode. Should the material chosen as anti-erosion layer 26 not be sufficiently electrically insulating or should the distance between the first electrode 27 and the second electrode 28 be reduced, a thin layer of highly-electrically insulating material may be inserted in the anti-erosion layer 26 between the first electrode 27 and the second electrode 28.

(15) The aerodynamics improvement device also comprises a voltage generator 30. The voltage generator 30 comprises a function generator 16 and a voltage amplifier 17. The function generator 16 delivers a voltage signal. The voltage signal may be of any sort. In some embodiments the voltage signal may be a periodic signal. The frequency of the periodic signal may be constant or may be depending on other parameters.

(16) The aerodynamics improvement device also comprises a controller 15. The controller 15 controls the function generator 16. The controller may activate or deactivate the function generator 16. The controller 15 may also provide instructions to the function generator 16. The controller 15 provides instructions for controlling the voltage signal output by the function generator 16. The function generator 16 is adapted to, upon reception of instructions from the controller, deliver a voltage signal of a predetermined type and/or amplitude and/or frequency.

(17) The controller 15 may have further functions in the aircraft or may be specifically dedicated to an aerodynamics improvement device according to the invention.

(18) The controller 15 may receive, as inputs, data representative of multiple parameters relative to the aircraft and/or its environment such as, for example: local electrical permittivity, outside air temperature, outside hygrometry, relative airspeed of the aircraft, angle of attack of the aircraft, etc.

(19) The voltage signal delivered by the function generator 16 is amplified by the voltage amplifier 17, which is powered by a voltage source 18. The voltage amplifier 17 is connected to the first electrode 27 and second electrode 28 to create a voltage difference between the first electrode 27 and the second electrode 28. The voltage amplifier 17 is adapted to supply the first electrode 27 and the second electrode 28 via conductors, e.g., wires 11, with a voltage difference of at least an ionizing voltage, adapted to generating an air plasma current 10 above the aerodynamic surface 6. The air plasma is generated above the gap 12 between the first electrode 27 and the second electrode 28 and creates a local plasma stream. The voltage generator may be adapted to provide a voltage of at least 10 kV.

(20) The aerodynamics improvement device also comprises an ice detection device 20 adapted to measure an electrical permittivity between the first electrode 27 and the second electrode 28. The first electrode 27 and the second electrode 28 being fixedly arranged in the anti-erosion layer 26, the permittivity variation between the first electrode 27 and the second electrode 28 is indicative of a variation of the permittivity of the external environment above the aerodynamic surface 6 due to a change in the local characteristics of the space between the electrodes above the aerodynamic surface, as can be expected when ice is accreted on the surface.

(21) The ice detection device 20 is adapted to output a permittivity voltage adapted to measure a variation of permittivity in the environment directly above the aerodynamic surface 6. The ice detection device 20 is connected to the first electrode 27 and the second electrode 28 so as to be able to apply the permittivity voltage between the first electrode 27 and the second electrode 28. The ice detection device 20 may be configured to monitor the electrodes to detect a change of the permittivity voltage during flight of the aircraft. If the change in the permittivity voltage meets a predetermined value, the ice detection device 20 output a signal or data indicating the presence of ice on the aerodynamic surface associated with the first and second electrode, The signal or data indicating the presence of ice may by applied by the controller 15 to apply ionizing voltages to the first and second electrodes and/or generate an audio and/or visual alert to a pilot in a cockpit of the aircraft.

(22) An isolator 19 is placed between the ice detection device 20 and the first electrode 27 and the second electrode 28 so as to disconnect the ice detection device 20 from the first electrode 27 and the second electrode 28. The controller 15 is adapted to control the isolator 19. The controller 15 is adapted to disconnect the isolator 19 when the voltage generator 30 is activated, and to connect the isolator 19 when the voltage generator 30 is deactivated. The ice detection device 20 is thus protected from high voltages delivered by the voltage generator 30.

(23) In FIG. 2, an aircraft tail surface is represented. Elements of an aerodynamics improvement device according to the invention are represented on one of the horizontal tail plane 9.

(24) The horizontal tail plane 9 comprises: a first group 21 of electrodes placed beneath, e.g., embedded in, the aerodynamic surface 6 at a leading edge of the horizontal tail plane 9; a second group 22 of electrodes placed beneath, e.g., embedded in, the aerodynamic surface 6 behind, e.g., aft in a chordwise direction, the leading edge and on a forward portion of the extrados of the horizontal tail plane 9; and a third group 23 of electrodes placed beneath, e.g., embedded in, the aerodynamic surface behind, e.g., aft in the chordwise direction, the second group 22 of electrodes such as on a forward portion of the extrados of the horizontal tail plane 9.

(25) Similar to the embodiment of FIG. 1, the electrodes of the first group 21, second group 22 and third group 23 may be embedded in an anti-erosion layer such as a polyurethane layer for example.

(26) The three groups 21, 22, 23 are also represented with more details on the FIG. 3.

(27) The first group 21 of electrodes is placed on a leading edge of the horizontal tail plane 9. The main function of the first group 21 of electrodes is to generate plasma discharges at the leading edge to limit the accretion of ice, and de-ice the aerodynamic surface 6 of the horizontal tail plane 9 at the leading edge. The limitation of ice accretion and de-icing occurs by the local heating and supersonic shocks provoked by the plasma discharges along the electrodes of the first group 21.

(28) The electrodes of the first group 21 are elongated. They are arranged in a spanwise direction of the leading edge. Some electrodes may extend along most of the length of the leading edge while some other may have a shorter length and be concentrated towards the tip of the horizontal tail plane 9, as represented on FIG. 2.

(29) The electrodes of the first group 21 are linear and have a regular constant cross-section, such that they do not exhibit tips. The plasma discharges thus happen all along the electrodes.

(30) The first group 21 of electrodes comprises a plurality of electrodes. In particular it comprises more than two electrodes. The electrodes may be alternatively powered by a voltage generator with a first voltage and a second voltage so as to always keep a voltage gap of at least of an ionizing voltage between two successive electrodes along the aerodynamic surface.

(31) At least one of the electrodes of the first group 21 may be electrically connected to the ground plane of the aircraft. Only the other electrode must be supplied with a ionizing voltage.

(32) Alternatively, each electrode may be at a different voltage, each voltage being chosen so that the voltage gap between two successive electrodes is at least of an ionizing voltage. For example a first electrode closest to the leading edge may be at a first voltage. A second electrode, adjacent to the first electrode, is at a second voltage which is at a level equal to the sum of at least a minimum ionizing voltage and the first voltage, such that the voltage applied across (between) the first and second electrode is at least the minimum ionizing voltage. A third electrode adjacent the second electrode at a third voltage which is at a voltage level of at least a sum of the minimum ionizing voltage and the second voltage.

(33) The electrodes may be supplied with a varying voltage, such as for example a periodic voltage signal. The voltages supplied to a first electrode and to a second electrode may have a phase difference between them.

(34) The first group 21 of electrodes may additionally be connected to a permittivity detector 20 for detecting the presence of ice on the aerodynamic surface leading edge. A controller may alternate the powering of the first group 21 of electrodes by the permittivity detector and by the voltage generator.

(35) The second group 22 of electrodes is placed on a forward portion of an extrados of the horizontal tail plane 9. The main function of the second group 21 of electrodes is to generate plasma discharges above the aerodynamic surface 6 at the leading edge of the horizontal tail plane 9. These plasma discharges can create local perturbations in a flow of air around the horizontal tail plane 9, such that the stall angle of the horizontal tail plane 9 may be increased. Higher angles of attack are therefore rendered safe with a device according to the invention.

(36) In the presented embodiment, the second group 22 of electrodes comprises two electrodes. They are arranged in a spanwise direction of the leading edge. These electrodes may extend along most of the length of the leading edge.

(37) The electrodes of the second group 22 each comprise tips 222. The tips 222 are arranged laterally along the length of the electrodes. The tips 222 are oriented along the same direction and all towards the leading edge. The electrodes of the second group 22 have a comb shape with linear tips.

(38) The tips 222 create precise locations at which the two electrodes of the second group 22 are closer to each other, such that the plasma generation is localized at very precise locations on the aerodynamic surface 6. This allows the emission of a pattern of plasma streams. The distance between the tips 222 may be chosen according to predetermined conditions. For example the distance may be chosen to optimally delay the boundary layer transition along the horizontal tail plane 9 at a given speed and angle of attack. The distance and patterns of the tips may be have a spatial frequency tuned to a frequency of cross flow unstable waves in the air flow over the aerodynamic surface 6 at cruise speed of the aircraft.

(39) The distance between tips can vary along the span of the leading edge such that the density of plasma discharges obtained may also vary along the span. An aerodynamics improvement device according to the invention can thus be adapted to an air flow differing along the fuselage and at a tip of a wing or a tail plane.

(40) Moreover the aft electrode 212 situated at the aft of the first group 21 and the forward electrode of the second group 22 may be supplied by the voltage generator such that the voltage gap between them is of at least the ionizing voltage. A second line of local plasma streams may thus be obtained above the gaps between the aft electrode 212 of the first group and the tips 222 of the forward electrode of the second group 22.

(41) The third group 23 of electrodes is placed on a forward portion of an extrados of the horizontal tail plane 9, aft to the second group 22 of electrodes. The main function of the third group 23 of electrodes is to generate plasma discharges above the aerodynamic surface 6 at the front of the extrados of the horizontal tail plane 9. These plasma discharges can create local perturbations in a flow of air around the horizontal tail plane 9, such that the separation of a boundary layer is spatially delayed along the horizontal tail plane 9, towards the trailing edge of the horizontal tail plane 9, such that the drag of the horizontal tail plane 9 is reduced, even at low angles of attack. These plasma discharges may inject momentum in the airflow by creating small local vortices or perturbations in the air flow over the extrados of the horizontal tail plane 9.

(42) In the represented embodiment, the third group 23 comprises four electrodes. The ionizing voltage between two successive electrodes can be obtained by different ways such as explained in connection to the first group of electrodes.

(43) The electrodes of the third group 23 each comprise tips 233. The tips 233 are arranged laterally along the length of the electrodes. The tips 233 are oriented along the same direction and all towards the leading edge. The tips 233 of the electrodes of the third group 23 have a triangular shape.

(44) Other characteristics of the tips 222 of the electrodes of the second group 22 may also apply to the tips 233 of the electrodes of the third group 23.

(45) Moreover the aft electrode of the second group 22 may be supplied by the voltage generator such its voltage gap with the forward electrode of the third group 23 is of at least an ionizing voltage.

(46) At least one electrode of the third group 23 is electrically connected to a lightning strike protective device comprising a metallic mesh 13 integrated at a tip 14 of the horizontal tail plane 9. The tip 14 itself may comprise one or more metallic parts connected to the mesh 13 and/or to an electrode of the third group 23. Said electrode of the third group 23 is also electrically connected at its other end to an electrical ground plane of the aircraft so as to conduct electrical charges from the wing tip to the electrical ground plane of the aircraft in particular in case of lightning strike. At least one of the electrodes of the third group 23 thus forms a bonding strip connecting lightning strike protection metallic meshes 13 and metallic components of the tip 14 to the ground plane of the aircraft.

(47) In FIG. 4 another embodiment of the present invention installed on a wing is represented in cross-section. Similarly to that of FIG. 1, it comprises a structural layer 25 and an anti-erosion layer 26 in which electrodes 27, 28 are embedded and isolated from the aerodynamic surface 6.

(48) In this embodiment a plurality of said first electrode 27 and second electrode 28 are alternated from the leading edge to the forward portion of either surface of the wing.

(49) In FIG. 5, an aircraft is represented which comprises an aerodynamics improvement device comprising electrodes: on a horizontal tail plane, as described in relation to FIG. 2, and on a wing.

(50) The aircraft may beneficially comprise electrodes on the opposite wing and horizontal tail plane, as well as on the vertical tail plane or engine nacelles, which are not represented on FIG. 5.

(51) The invention is not limited to the specific embodiments herein disclosed as examples. In particular any example given in relation to a wing or a horizontal tail plane may be applied to any other lift or control surface, and more generally to any aerodynamic surface, of an aircraft. The invention also encompasses other embodiments not herein explicitly described, which may comprise various combinations of the features herein described.

(52) While at least one exemplary embodiment of the present invention(s) is disclosed herein, it should be understood that modifications, substitutions and alternatives may be apparent to one of ordinary skill in the art and can be made without departing from the scope of this disclosure. This disclosure is intended to cover any adaptations or variations of the exemplary embodiment(s). In addition, in this disclosure, the terms “comprise” or “comprising” do not exclude other elements or steps, the terms “a” or “one” do not exclude a plural number, and the term “or” means either or both. Furthermore, characteristics or steps which have been described may also be used in combination with other characteristics or steps and in any order unless the disclosure or context suggests otherwise. This disclosure hereby incorporates by reference the complete disclosure of any patent or application from which it claims benefit or priority.