# US 10,118,706 B2 · Hybrid acoustic and induction-heating systems and methods for impeding formation of ice > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,118,706 B2 - Document ID: US10118706B2 - Status: Granted - Kind: B2 - Application number: 15/183,593 - Filed: 2016-06-15 - Published: 2017-12-21 - Granted: 2018-11-06 - Earliest claimed: 2016-06-15 - Assignees: The Boeing Company - Applicants: The Boeing Company - Inventors: John Ralph Hull; Minas H. Tanielian - Web page: https://patentgrep.com/patent/US10118706B2 ## CPC - B64D 15/12: by electric heating (heating arrangements specially adapted for transparent or reflecting areas H05B3/84) - B64D 15/22: Automatic initiation by icing detector - B64D: EQUIPMENT FOR FITTING IN OR TO AIRCRAFT; FLIGHT SUITS; PARACHUTES; ARRANGEMENT OR MOUNTING OF POWER PLANTS OR PROPULSION TRANSMISSIONS IN AIRCRAFT ## Abstract An airfoil comprises a skin, comprising an external surface and an internal surface. The skin has a controlled region. The airfoil also comprises an interior space, formed by the skin. The airfoil additionally comprises a hybrid acoustic induction-heating system, configured to impede formation of ice on the external surface. The hybrid acoustic induction-heating system comprises an induction coil and a control system. At least a portion of the induction coil is sufficiently close to the internal surface to produce an eddy current within the controlled region when an alternating electrical current is flowing in the induction coil. The control system is configured to generate inductive heat and acoustic pressure in the controlled region by supplying the alternating electrical current to the induction coil based, at least in part, on an ambient temperature of a layer of fluid flowing over the external surface. ## Claims ### Claim 1 An airfoil, comprising: a skin, comprising an external surface and an internal surface, opposite the external surface, wherein the skin is magnetically and electrically conductive, and wherein the skin has a controlled region; an interior space, formed by the skin, wherein the internal surface of the skin faces the interior space; a leading edge along the external surface of the skin; and a hybrid acoustic induction-heating system, configured to impede formation of ice on the external surface of the skin and comprising: an induction coil within the interior space, wherein at least a portion of the induction coil is sufficiently close to the internal surface of the skin to produce an eddy current within the controlled region of the skin when an alternating electrical current is flowing in the induction coil; and a control system, configured to generate inductive heat and acoustic pressure in the controlled region of the skin by supplying the alternating electrical current to the induction coil based, at least in part, on an ambient temperature of a layer of fluid flowing over the external surface of the skin. ### Claim 2 (depends on 1) The airfoil according to claim 1, wherein the induction coil has a sheet form. ### Claim 3 (depends on 1) The airfoil according to claim 1, wherein the induction coil has a volumetric form. ### Claim 4 (depends on 1) The airfoil according to claim 1, wherein at least the portion of the induction coil is parallel to the skin. ### Claim 5 (depends on 1) The airfoil according to claim 1, wherein the airfoil is selected from the group consisting of a wing, an erosion shield, an empennage, a horizontal stabilizer, a vertical stabilizer, a winglet, a turbine-engine inlet, an engine nacelle, and a turbine blade. ### Claim 6 (depends on 1) The airfoil according to claim 1, wherein at least the portion of the induction coil is closer to the leading edge than any other portion of the induction coil and is positioned to heat the leading edge. ### Claim 7 (depends on 1) The airfoil according to claim 1, wherein at least the portion of the induction coil in transverse to the leading edge in the controlled region. ### Claim 8 (depends on 1) The airfoil according to claim 1, wherein at least the portion of the induction coil is parallel to the leading edge in the controlled region. ### Claim 9 (depends on 1) The airfoil according to claim 1, further comprising a temperature sensor, configured to measure the ambient temperature of the layer of fluid flowing over the external surface of the skin. ### Claim 10 (depends on 1) The airfoil according to claim 1, wherein the skin comprises a nickel-iron alloy. ### Claim 11 (depends on 1) The airfoil according to claim 1, wherein the skin has a thickness of less than 1 mm and greater than 0.0001 mm. ### Claim 12 (depends on 1) The airfoil according to claim 1, wherein the skin is ferromagnetic. ### Claim 13 (depends on 1) The airfoil according to claim 1, wherein the skin has a relative magnetic permeability of greater than 1,000 and less than 10,000,000. ### Claim 14 (depends on 1) The airfoil according to claim 1, wherein the skin has a Curie temperature of less than 300° C. and greater than 50° C. ### Claim 15 (depends on 1) The airfoil according to claim 1, wherein the control system is configured to supply a direct electrical current to the induction coil to generate a steady-state magnetic field within the skin to interact with the eddy current to generate the acoustic pressure in the controlled region. ### Claim 16 (depends on 15) The airfoil according to claim 15, wherein the steady-state magnetic field, induced by the direct electrical current, supplied to the induction coil, is transverse to the skin at the internal surface of the skin. ### Claim 17 (depends on 15) The airfoil according to claim 15, wherein, at a location in the skin between the leading edge and a portion of the internal surface of the skin that is closest to the leading edge, the steady-state magnetic field is transverse to the leading edge. ### Claim 18 (depends on 15) The airfoil according to claim 15, wherein, at a location in the skin between the leading edge and a portion of the internal surface of the skin that is closest to the leading edge, the steady-state magnetic field is parallel to the leading edge. ### Claim 19 (depends on 15) The airfoil according to claim 15, wherein a magnitude of the steady-state magnetic field is greater than 0.1 T (tesla) and less than 100 T. ### Claim 20 (depends on 15) The airfoil according to claim 15, wherein the alternating electrical current generates an alternating magnetic field with an amplitude that is less than a magnitude of the steady-state magnetic field. ### Claim 21 (depends on 20) The airfoil according to claim 20, wherein a ration of the amplitude of the alternating magnetic field to the magnitude of the steady-state magnetic field is less than 0.1 and greater than 0.0001. ### Claim 22 (depends on 15) The airfoil according to claim 15, wherein an amplitude of the alternating electrical current is less than a magnitude of the direct electrical current. ### Claim 23 (depends on 22) The airfoil according to claim 22, wherein a ration of the amplitude of the alternating electrical current and the magnitude of the direct electrical current is less than 0.1 and greater than 0.0001. ### Claim 24 (depends on 1) The airfoil according to claim 1, wherein the control system comprises: a power supply, configured to supply the alternating electrical current to the induction coil; and a controller programmed to: receive signals, representative of first ambient conditions known to cause formation of the ice on the external surface of the skin and second ambient conditions known to impede formation of the ice on the external surface, wherein the first ambient conditions and the second ambient conditions both comprise the ambient temperature of the layer of fluid flowing over the external surface of the skin, cause the power supply to supply the alternating electrical current to the induction coil to generate inductive heat and acoustic pressure in the controlled region of the skin based upon the first ambient conditions, and cause the power to discontinue supplying the alternating electrical current to the induction coil based upon the second ambient conditions. ### Claim 25 (depends on 24) The airfoil according to claim 24, wherein the controller is further programmed to cause the power supply to supply the alternating electrical current to the induction coil when the ambient temperature of the layer of fluid, flowing over the external surface of the skin, is below a first threshold temperature. ### Claim 26 (depends on 25) The airfoil according to claim 25, wherein the first threshold temperature is above a freezing point of water and below 5° C. ### Claim 27 (depends on 25) The airfoil according to claim 25, wherein the controller is further programmed to cause the power supply to discontinue supplying the alternating electrical current to the induction coil when the ambient temperature of the layer fluid, flowing over the external surface of the skin, is above a second threshold temperature. ### Claim 28 (depends on 27) The airfoil according to claim 27, wherein the second threshold temperature is different than the first threshold temperature. ### Claim 29 (depends on 27) The airfoil according to claim 27, wherein the second threshold temperature is greater than the first threshold temperature. ### Claim 30 (depends on 27) The airfoil according to claim 27, wherein the second threshold temperature is above 2° C. and below 10° C. ### Claim 31 (depends on 1) The airfoil according to claim 1, wherein at least the portion of the induction coil is no more than 10 mm away from the internal surface of the skin. ### Claim 32 (depends on 31) The airfoil according to claim 31, wherein at least the portion of the induction coil is no more than 1 mm away from the intern surface of the skin. ### Claim 33 (depends on 1) The airfoil according to claim 1, wherein the alternating electrical current has a frequency that is at least 100 kHz (kilohertz) and at most 10 MHz (megahertz). ### Claim 34 (depends on 33) The airfoil according to claim 33, wherein the frequency of the alternating electrical current is at least 1 MHz. ### Claim 35 (depends on 1) The airfoil according to claim 1, further comprising an electrical insulator in the interior space, wherein the electrical insulator is coupled to the skin. ### Claim 36 (depends on 35) The airfoil according to claim 35, wherein the electrical insulator supports the skin. ### Claim 37 (depends on 35) The airfoil according to claim 35, wherein the electrical insulator supports at least one magnet.