Patent Description:
A modern aircraft propulsion system may include a gas turbine engine housed within a nacelle. The nacelle includes an inlet structure for directing incoming air to the gas turbine engine. This inlet structure includes an inlet lip, an inner barrel and an outer barrel. The inlet lip forms a leading edge of the inlet structure. The inner barrel is connected to a radial inner end of the inlet lip, and at least partially forms an outer peripheral boundary of an inlet duct into the aircraft propulsion system. The outer barrel is connected to a radial outer end of the inlet lip, and circumscribes the inner barrel.

Under certain environmental conditions, the inlet lip may be susceptible to ice accumulation. To melt ice that may accumulate on the inlet lip, the inlet structure may be configured with a thermal anti-icing system. A lip skin of the inlet lip, for example, may be configured with an electrical resistance heater. Such an electrical resistance heater may be attached to an interior surface of the lip skin to minimize a thermal conduction path length from the heater to an exterior surface of the lip skin / the inlet lip. While such electrical resistance heaters have various benefits, there is still room in the art for improvement. Damage to the lip skin and the electrical resistance heater arranged therewith following a foreign object impact, for example, may render a portion of or the entire electrical resistance heater inoperable where the damage severs one or more electrical resistance circuits within the electrical heater Prior art includes ,<CIT> and <CIT>.

Furthermore, <CIT> describes a system in which microwaves are propagated over a dielectric substrate being in contact with an ice layer. Additionally, <CIT> describes a susceptor and a coil, which creates an eddy current in the susceptor. Both the susceptor and the coil are integrated into a composite skin.

According to an aspect of the present invention, an assembly is provided for a structure as claimed in claim <NUM>.

The thermal anti-icing system may also include a reflector configured to direct stray microwaves back towards the susceptor. The reflector may be formed by at least a portion of a third of the plurality of layers of material.

The composite skin may extend between the exterior surface and the interior surface without interruption.

The susceptor may be arranged between the waveguide and the exterior surface.

The composite skin may include a first layer, a second layer and a third layer between the first layer and the second layer. The first layer may be configured as or otherwise include the susceptor. The second layer may be configured as or otherwise include the waveguide.

The third layer may be configured from or otherwise include microwave transparent material.

The composite skin may include a plurality of layers. A first of the layers may include the susceptor and the waveguide. The waveguide may be laterally spaced from the susceptor within the first of the layers.

A second of the layers may be configured from or otherwise include microwave transparent material.

At least one of the susceptor or the waveguide may be configured from or otherwise include metal.

The susceptor may be configured from or otherwise include fiber reinforcement within a polymer matrix.

The thermal anti-icing system may also include a reflector configured to reflect microwaves travelling away from the susceptor and the exterior surface back towards the susceptor.

The reflector may be integrated into the composite skin between the exterior surface and the interior surface.

The reflector may be arranged between the interior surface and the waveguide.

The reflector may be configured from or otherwise include metal.

The microwaves may be transmitted at a frequency between one gigahertz (<NUM>) and ten gigahertz (<NUM>).

The microwaves may be transmitted at a frequency between forty gigahertz (<NUM>) and eighty gigahertz (<NUM>).

The microwaves may be transmitted at a frequency between twenty gigahertz (<NUM>) and twenty-five gigahertz (<NUM>).

The microwaves may be transmitted at a frequency between one-hundred and fifty gigahertz (<NUM>) and two-hundred gigahertz (<NUM>).

The thermal anti-icing system may also include a microwave source configured to generate the microwaves directed by the waveguide.

The microwave sources may be configured as or otherwise include a magnetron, a klystron, a gyrotron or a solid state source.

The assembly may also include a nacelle inlet structure for an aircraft propulsion system. The nacelle inlet structure may include the composite skin.

<FIG> illustrates an assembly <NUM> for an aircraft. This aircraft assembly <NUM> includes an aircraft structure <NUM> and a microwave thermal anti-icing system <NUM>.

The aircraft structure <NUM> includes at least one exterior skin <NUM>; e.g., a multilayered, composite skin. This exterior skin <NUM> is configured to form an exterior surface <NUM> of the aircraft structure <NUM> such as an aerodynamic flow surface. The exterior skin <NUM>, for example, may be configured with a nacelle of a propulsion system for the aircraft; e.g., the aircraft structure <NUM> may be a nacelle structure. The exterior skin <NUM>, more particularly, may be configured as or otherwise included as part of a noselip of the nacelle. Alternatively, the exterior skin <NUM> may be configured with another component / structure of the aircraft such as its fuselage or a wing.

The aircraft structure <NUM> and its exterior skin <NUM> extend laterally in a first direction (e.g., an x-axis direction) along an x-axis. The aircraft structure <NUM> and its exterior skin <NUM> extend laterally in a second direction (e.g., a y-axis direction) along a y-axis. The aircraft structure <NUM> and its exterior skin <NUM> extend vertically in a vertical direction (e.g., a z-axis direction) along a z-axis. Note, the term "lateral" may be used herein to generally describe the first lateral direction, the second lateral direction and/or any other direction within the x-y plane. Also note, the term "vertical" may be used herein to describe a depthwise panel direction and is not limited to a gravitational up/down direction. Furthermore, for ease of illustration, the x-y plane is shown as a generally flat plane. However, in other embodiments, the x-y plane and, thus, the aircraft structure <NUM> and/or its exterior skin <NUM> may be curved and/or follow an undulating geometry. For example, the x-y plane and, thus, the aircraft structure <NUM> and/or its exterior skin <NUM> may be arcuate, cylindrical, conical, frustoconical, or tapered with or without radial undulations. In such embodiments, a solely vertical direction (e.g., z-axis direction) may be defined relative to a position of interest on the x-y plane. For example, on a spherical x-y plane, the vertical direction (e.g., z-axis) direction is a radial direction.

The exterior skin <NUM> is configured as a relatively thin body that extends laterally within the x-y plane. The exterior skin <NUM> has a vertical thickness <NUM>. This skin vertical thickness <NUM> extends vertically between opposing side surfaces <NUM> and <NUM> of the exterior skin <NUM>, where the skin exterior surface <NUM> may form the structure exterior surface <NUM>. The exterior skin body may be solid, non-porous vertically between the skin exterior surface <NUM> and the skin interior surface <NUM>. Material(s) of the exterior skin <NUM> may thereby extend between the skin exterior surface <NUM> and the skin interior surface <NUM> without any interruptions; e.g., pores, voids, chambers, cavities and/or any other types of apertures. The present disclosure, however, is not limited to such an exemplary solid, non-porous exterior skin configuration.

The thermal anti-icing system <NUM> is configured to melt and/or prevent ice accumulation on the exterior surface <NUM>, <NUM>. The thermal anti-icing system <NUM> of <FIG> includes at least one susceptor <NUM> and a microwave system <NUM>.

The susceptor <NUM> is configured to absorb electromagnetic energy (e.g., microwave radiation, also referred to as "microwaves") and convert that absorbed electromagnetic energy into heat. The susceptor <NUM>, for example, may be configured as a thin layer (or strip, or wire) of material. Examples of the susceptor material may include, but are not limited to: indium tin oxide (ITO); aluminum (Al) or an alloy thereof; ferrous metal such as stainless steel; titanium (Ti) or an alloy thereof; Inconel alloys; chromium (Cr) or an alloy thereof; graphite; composites of metal(s) and ceramic(s) (e.g., cermets); doped silicon carbide; and/or metal oxide(s). Another example of the susceptor material includes (e.g., fiber) reinforcement material within a polymer matrix, where a thickness of the susceptor material may be sized to be about or exactly one-quarter (<NUM>/<NUM>) of the wavelength of the microwaves generated by the microwave system <NUM>. An example of the reinforcement material is fiberglass. An example of the polymer matrix is thermoset epoxy resin. The present disclosure, however, is not limited to the foregoing exemplary susceptor materials.

The microwave system <NUM> includes a microwave source <NUM> and a microwave transmission system <NUM>. The microwave source <NUM> may be configured to generate microwaves at a frequency of, for example, between <NUM> gigahertz (GHz) and <NUM> gigahertz; e.g., at exactly or about (e.g., +/- <NUM> or <NUM>) <NUM> gigahertz (GHz). Of course, in other embodiments, the microwave source <NUM> may generate the microwaves at a frequency at or above <NUM> gigahertz and/or at a frequency at or below <NUM> gigahertz. For example, the microwave source <NUM> may be configured to generate microwaves at a frequency between one and ten gigahertz; e.g., between one and three gigahertz, or more specifically between <NUM> and <NUM> gigahertz for example. The microwave source <NUM> may also or alternatively be configured to generate microwaves at a frequency between fifteen and thirty gigahertz; e.g., between twenty and twenty-five gigahertz. The microwave source <NUM> may also or alternatively be configured to generate microwaves at a frequency between forty and eighty gigahertz; e.g., between <NUM> and <NUM> gigahertz. The microwave source <NUM> may also or alternatively be configured to generate microwaves at a frequency between one-hundred and forty (<NUM>) and two-hundred and ten (<NUM>) gigahertz; e.g., between one-hundred and fifty (<NUM>) and two-hundred (<NUM>) gigahertz.

The microwave source <NUM> may be configured as or otherwise include a vacuum electron device (VED) such as, but not limited to, a magnetron, a klystron and a gyrotron. The microwave source <NUM> may alternatively be configured as or otherwise include a solid state device; e.g., a solid state microwave source. Such a solid state device may include one or more radio-frequency (RF) transistors configured to generate the microwaves. Generally speaking, a solid state device may have some advantages over a vacuum electron device. For example, a solid state device may require less (e.g., <NUM>-100x less) operational power than a vacuum electron device; e.g., <NUM>-<NUM> volts versus <NUM> volts. A solid state device may have a longer useful lifetime than a vacuum electron device; e.g., <NUM>-<NUM> plus years versus <NUM>-<NUM> hours. A solid state device may have a lower mass and, thus, weigh less than a vacuum electron device. A solid state device may have improved control over a vacuum electron device.

The microwave source <NUM> may be configured to generate a continuous output (e.g., stream) of the microwaves. The microwave source <NUM> may also or alternatively be configured to generate an intermittent (e.g., pulsed) output of the microwaves.

The microwave transmission system <NUM> is configured to transmit the microwaves generated by the microwave source <NUM> to a desired location or locations. The microwave transmission system <NUM> is further configured to selectively direct the microwaves at / to the susceptor <NUM> as described below in further detail.

The microwave transmission system <NUM> of <FIG> includes one or more waveguides 44A and 44B (generally referred to as "<NUM>"); e.g., electromagnetic feed lines. The upstream waveguide 44A is coupled with the microwave source <NUM>, and is configured to transmit the microwaves generated by the microwave source <NUM> to the downstream waveguide 44B. The downstream waveguide 44B is configured to direct the microwaves received from the upstream waveguide 44A at / to the susceptor <NUM>. These waveguides <NUM> may be configured as segments of a common waveguide. Alternatively, the waveguides <NUM> may be configured as discrete waveguide with common or different configurations.

The waveguides <NUM> may be configured as dielectric waveguides. Examples of a dielectric waveguide include, but are not limited to, a microstrip, a coplanar waveguide and a stripline. Each waveguide <NUM>, for example, may be configured as a layer (or strip, or wire) of material. This waveguide material may be metal such as, but not limited to, indium tin oxide (ITO). The waveguide material may be a fluoropolymer such as, but not limited to, polytetrafluoroethylene (PTFE) (e.g., Teflon® material) or polyvinylidene fluoride (PVDF). The waveguide material may also or alternatively include other polymeric materials and/or ceramics. The present disclosure, however, is not limited to the foregoing exemplary waveguide materials.

One or more of the waveguides <NUM> (e.g., the upstream waveguide 44A) may be at least partially or completely covered by an insulating material <NUM>. This insulating material <NUM> is a microwave resistive material such as, but not limited to, metal or alumina (e.g., Al<NUM>O<NUM>) or silica (e.g., SiO<NUM>). The present disclosure, however, is not limited to the foregoing exemplary insulating materials.

Referring to <FIG>, the susceptor <NUM> and the downstream waveguide 44B are each configured with the aircraft structure <NUM> and its exterior skin <NUM>. The susceptor <NUM> is also thermally coupled with the exterior surface <NUM>, <NUM>. The susceptor <NUM> of <FIG>, for example, is integrated into the exterior skin <NUM> vertically between the skin exterior surface <NUM> and the skin interior surface <NUM>. The downstream waveguide 44B of <FIG> is also integrated into the exterior skin <NUM> vertically between the skin exterior surface <NUM> and the skin interior surface <NUM>, where the downstream waveguide 44B is vertically between the susceptor <NUM> and the skin interior surface <NUM>.

The exterior skin <NUM> of <FIG> includes a plurality of skin layers 48A-E (generally referred to as "<NUM>"); e.g., intra-skin layers. These skin layers <NUM> are arranged together in a stack to form the exterior skin <NUM>. The skin layers <NUM> are bonded to one another by an adhesive <NUM>; e.g., a microwave transparent adhesive. Examples of the adhesive <NUM> may include, but are not limited to, thermoset epoxy resin or any other bonding material with low dielectric loss. The present disclosure, however, is not limited to the foregoing exemplary adhesive materials.

The interior skin layer 48B may form the skin interior surface <NUM>. The exterior skin layer 48A may form the exterior surface <NUM>, <NUM>. The intermediate skin layers 48C-D are arranged sequentially vertically between the other skin layers 48A and 48B.

At least one of the skin layers <NUM> (e.g., 48C) may at least partially or completely form the susceptor <NUM>. The (e.g., exterior) intermediate skin layer 48C of <FIG>, for example, forms the susceptor <NUM>. More particularly, the intermediate skin layer 48C of <FIG> is (or otherwise includes) the thin layer of the susceptor material that forms the susceptor <NUM>. The susceptor <NUM> may thereby be located within the exterior skin <NUM> at (e.g., on, adjacent or proximate) the exterior surface <NUM>, <NUM>. For ease of description, this intermediate skin layer 48C that forms the susceptor <NUM> may be referred to below as a susceptor layer <NUM>.

The susceptor <NUM> of <FIG> is configured to laterally overlap (along the x-axis and/or the y-axis) an entirety of the aircraft structure <NUM>, the exterior skin <NUM> and/or the exterior surface <NUM>, <NUM>. The susceptor <NUM>, for example, may extend along an entire lateral extent of the exterior surface <NUM>, <NUM>. Alternatively, the susceptor <NUM> may laterally overlap (along the x-axis and/or the y-axis) a select portion of the exterior surface <NUM>, <NUM>. For example, referring to <FIG>, the susceptor layer <NUM> may be configured as a strip of material with a lateral width (along the x-axis and/or the y-axis) that is less than a lateral width of the exterior skin <NUM> and a lateral width of the exterior surface <NUM>, <NUM>. With such an arrangement, thermal anti-icing of the exterior surface <NUM>, <NUM> may be focused to a select region corresponding to the susceptor <NUM>. In other embodiments, referring to <FIG>, the susceptor <NUM> may include one or more (e.g., discrete or interconnected) susceptor segments <NUM>. Each of these susceptor segments <NUM> may be configured to focus thermal anti-icing to multiple corresponding regions, or provide effective coverage for the entire exterior surface <NUM>, <NUM>.

Referring again to <FIG>, at least one of the skin layers <NUM> (e.g., 48E) may at least partially or completely form the downstream waveguide 48B. The (e.g., interior) intermediate skin layer 48E of <FIG>, for example, forms the downstream waveguide 44B. More particularly, the intermediate skin layer 48E of <FIG> is (or otherwise includes) the layer of waveguide material that forms the downstream waveguide 44B. The downstream waveguide 44B may thereby be located within the exterior skin <NUM> at (e.g., on, adjacent or proximate) the skin interior surface <NUM>. For ease of description, this intermediate skin layer 48E that forms the downstream waveguide 44B may be referred to below as a waveguide layer <NUM>.

The downstream waveguide 44B of <FIG> is configured to laterally overlap (along the x-axis and/or the y-axis) the entirety of the aircraft structure <NUM>, the exterior skin <NUM>, the exterior surface <NUM>, <NUM> and/or the susceptor <NUM>. The downstream waveguide 44B, for example, may extend along the entire lateral extent of the exterior surface <NUM>, <NUM>. Alternatively, the downstream waveguide 44B may laterally overlap (along the x-axis and/or the y-axis) a select portion of the exterior surface <NUM>, <NUM>. For example, referring to <FIG>, the waveguide layer <NUM> may be configured as a strip of material with a lateral width (along the x-axis and/or the y-axis) that is less than the lateral width of the exterior skin <NUM> and the lateral width of the exterior surface <NUM>, <NUM>. In other embodiments, referring to <FIG>, the downstream waveguide 44B may include one or more (e.g., discrete or interconnected) waveguide segments <NUM>. Each of these waveguide segments <NUM> may be configured to focus the microwaves to a respective one of the susceptor segments <NUM>.

Referring again to <FIG>, one or more of the remaining skin layers 48A, 48B and 48D may be configured as structural layers, support layers and/or filler layers. Each of the skin layers 48A and 48B, for example, may be configured as a thin sheet of reinforcement material embedded within (or otherwise arranged with) a matrix. The reinforcement material may include fibrous and/or granular (e.g., powder) material that is transparent to the electromagnetic energy; e.g., the microwave radiation. Examples of the reinforcement material may include, but are not limited to, fiberglass or any other material with low dielectric loss. The matrix material is a bonding material that is also transparent to the electromagnetic energy; e.g., the microwave radiation. This matrix material may be the same type as (or may be) the adhesive <NUM> (e.g., a microwave transparent adhesive) bonding the skin layers <NUM> together. In other embodiments, however, the matrix material may be different than, but complementary to for example, the adhesive material. The remaining (e.g., middle, intra-susceptor-waveguide) intermediate skin layer 48D may be configured as a layer of the adhesive <NUM> / the matrix material. Of course, in other embodiments, the intermediate skin layer 48D may alternatively be configured as a thin sheet of the reinforcement material embedded within (or otherwise arranged with) the matrix. The present disclosure, however, is not limited to the foregoing exemplary reinforcement or matrix materials.

Each of the skin layers <NUM> has a vertical thickness along the z-axis. The susceptor layer <NUM> vertical thickness may be equal to or different (e.g., less or greater) than the vertical thicknesses of any one or more of the remaining skin layers <NUM>. Generally speaking, the susceptor layer <NUM> vertical thickness is selected based on a frequency of interest of the electromagnetic radiation. The susceptor layer <NUM> vertical thickness may also or alternatively be selected to be one-quarter (<NUM>/<NUM>) of a wavelength of the electromagnetic radiation at the frequency of interest. The waveguide layer <NUM> vertical thickness may similarly be equal to or different (e.g., less or greater) than the vertical thicknesses of any one or more of the remaining skin layers <NUM>. The present disclosure, however, is not limited to such exemplary susceptor and/or waveguide layer vertical thicknesses.

The intermediate skin layer 48C is described above as forming the susceptor <NUM>. The present disclosure, however, is not limited to such an exemplary construction. In some embodiments, for example referring to <FIG>, the susceptor <NUM> may alternatively (or also) be formed by another one of the intermediate skin layers (e.g., 48D). In some embodiments, referring to <FIG>, the susceptor <NUM> may alternatively (or also) be formed by the exterior skin layer 48A. With each of the foregoing configurations, the susceptor <NUM> is arranged within the exterior skin <NUM> vertically between the downstream waveguide 44B and the exterior surface <NUM>, <NUM>.

The intermediate skin layer 48E is described above as forming the downstream waveguide 44B. The present disclosure, however, is not limited to such an exemplary construction. In some embodiments, for example referring to <FIG>, the downstream waveguide 44B may alternatively (or also) be formed by another one of the intermediate skin layers (e.g., 48D). In some embodiments, referring to <FIG>, the downstream waveguide 44B may alternatively (or also) be formed by the interior skin layer 48B. With each of the foregoing configurations, the downstream waveguide 44B is arranged within the exterior skin <NUM> vertically between the susceptor <NUM> and the skin interior surface <NUM>.

During operation of the thermal anti-icing system <NUM> of <FIG>, the microwave source <NUM> generates microwaves. These microwaves are received by the downstream waveguide 44B through the upstream waveguide 44A. Referring to <FIG>, the downstream waveguide 44B directs the received microwaves <NUM> in a first vertical direction towards / to the susceptor <NUM> through one or more other layers <NUM> of the exterior skin <NUM>. These transmitted microwaves <NUM> impinge against and are absorbed by the susceptor <NUM>, and are then transformed by the susceptor <NUM> into thermal energy <NUM>. This thermal energy <NUM> may be transferred via conduction from the susceptor <NUM> into a region of the aircraft structure exterior skin <NUM> adjacent and/or proximate the susceptor <NUM>. This transfer of the thermal energy <NUM> may heat the region of the exterior surface <NUM>, <NUM> and thereby melt and/or prevent ice accumulation over and/or about the aircraft structure exterior skin region.

Referring to <FIG>, the downstream waveguide 44B may also direct some of the received microwaves <NUM> in a second vertical direction (e.g., opposite the first vertical direction) away from the susceptor <NUM>. The thermal anti-icing system <NUM> may therefore include a reflector <NUM>. This reflector <NUM> is configured to reflect (e.g., redirect) the microwaves <NUM> that are traveling away from the susceptor <NUM> and the exterior surface <NUM>, <NUM> back towards / to the susceptor <NUM>. The reflector <NUM> may thereby utilize / refocus otherwise potentially wasted microwave energy back towards the susceptor <NUM> to generate additional thermal energy <NUM>. The reflector <NUM> may therefore increase efficiency of the thermal anti-icing system <NUM>.

The reflector <NUM> may be configured as a layer (or strip) of material. This reflector material may be metal such as, but not limited to, indium tin oxide (ITO). Typically, the reflector material has a conductance of less than one ohm-per-square inch (<NUM>Ω/in<NUM>). The present disclosure, however, is not limited to the foregoing exemplary reflector materials or reflector conductance.

The reflector <NUM> of <FIG> is configured with the aircraft structure <NUM> and its exterior skin <NUM>. The reflector <NUM> of <FIG>, for example, is integrated into the exterior skin <NUM> vertically between the skin exterior surface <NUM> and the skin interior surface <NUM>, where the reflector <NUM> is typically vertically between the downstream waveguide 44B and the skin interior surface <NUM>.

The exterior skin <NUM> of <FIG> may have a similar construction as the exterior skin <NUM> of <FIG>. However, the exterior skin <NUM> of <FIG> further includes one or more addition intermediate skin layers 48F and <NUM> (also generally referred to as "<NUM>"). At least one of the intermediate skin layers (e.g., <NUM>) may at least partially or completely form the reflector <NUM>. The intermediate skin layer <NUM> of <FIG>, for example, forms the reflector <NUM>. More particularly, the intermediate skin layer <NUM> of <FIG> is (or otherwise includes) the layer of reflector material that forms the reflector <NUM>. The reflector <NUM> may be located within the exterior skin <NUM> at (e.g., on, adjacent or proximate) the skin interior surface <NUM>. For ease of description, this intermediate skin layer <NUM> that forms the reflector <NUM> may be referred to below as a reflector layer <NUM>.

The reflector <NUM> of <FIG> is configured to laterally overlap (along the x-axis and/or the y-axis) the entirety of the aircraft structure <NUM>, the exterior skin <NUM>, the exterior surface <NUM>, <NUM> and/or one or more other thermal anti-icing system components <NUM> and 44B. The reflector <NUM>, for example, may extend along the entire lateral extent of the exterior surface <NUM>, <NUM>. Alternatively, the reflector <NUM> may laterally overlap (along the x-axis and/or the y-axis) a select portion of the exterior surface <NUM>, <NUM>. For example, referring to <FIG>, the reflector layer <NUM> may be configured as a strip of material with a lateral width (along the x-axis and/or the y-axis) that is less than the lateral width of the exterior skin <NUM> and the lateral width of the exterior surface <NUM>, <NUM>. In other embodiments, referring to <FIG>, the reflector <NUM> may include one or more (e.g., discrete or interconnected) reflector segments <NUM>. Each of these reflector segments <NUM> may refocus the microwaves to a respective one of the susceptor segments <NUM>.

Referring to <FIG>, the remaining skin layer 48F may be configured as a structural layer, a support layer and/or a filler layer. The remaining (e.g., intra-reflector-waveguide) intermediate skin layer 48F may be configured as a layer of the adhesive <NUM> / the matrix material. Of course, in other embodiments, the intermediate skin layer 48F may alternatively be configured as a thin sheet of the reinforcement material embedded within (or otherwise arranged with) the matrix. The present disclosure, however, is not limited to the foregoing exemplary reinforcement or matrix materials.

The reflector layer <NUM> vertical thickness may be equal to or different (e.g., less or greater) than the vertical thicknesses of any one or more of the remaining skin layers <NUM>.

In some embodiments, each of the thermal anti-icing system components <NUM>, 44B and <NUM> may be formed by or otherwise includes in a discrete one of the skin layers <NUM> of the exterior skin <NUM>; e.g., see <FIG> and <FIG>. In other embodiments, referring to <FIG> for example, two or more of the thermal anti-icing system components (e.g., <NUM> and 44B) may be configured together / formed in a common one of the skin layers <NUM>. At least one downstream waveguide 44B and one or more of the susceptors <NUM> (or susceptor segments <NUM>) of <FIG>, for example, are all arranged in the same intermediate skin layer 48C. The downstream waveguide 44B and the susceptors <NUM> are vertically aligned / vertically overlap within the exterior skin <NUM>. However, the downstream waveguide 44B is laterally displaced from each of the susceptors <NUM>. The downstream waveguide 44B of <FIG>, for example, is laterally separated from the susceptors <NUM> by microwave transparent material; e.g., the adhesive <NUM>, the matrix, etc. The downstream waveguide 44B of <FIG> is also located laterally between the susceptors <NUM>. Of course, various other arrangements of the thermal anti-icing system components within the exterior skin <NUM> are possible and contemplated by the present disclosure.

In some embodiments, the microwave source <NUM> of <FIG> may be tuned to an absorption frequency of the susceptor <NUM>. This may facilitate provision of higher electromagnetic radiation frequencies, while reducing a footprint of the electromagnetic radiation. For example, the microwave source <NUM> may be tuned for a V-band frequency between forty gigahertz and eighty gigahertz; e.g., between <NUM> and <NUM>. Within such a frequency range, absorption by other aircraft structure materials is relatively low and the susceptor <NUM> may be made relatively small. The susceptor <NUM>, for example, may be about <NUM> thick for a microwave transmission frequency of about <NUM>. The present disclosure, however, is not limited to the forgoing exemplary frequencies or sizes.

In addition to facilitating heating of the exterior skin <NUM>, the thermal anti-icing system <NUM> of the present disclosure is also relatively resistant to foreign object damage (FOD). For example, during operation, the aircraft structure <NUM> of <FIG> may be subject to a foreign object impact. Under certain conditions, such an impact may crack and/or fracture, inter alia, the susceptor <NUM>; e.g., material within the susceptor layer <NUM> (e.g., see <FIG>). Even when cracked / fractured, however, the susceptor <NUM> may still be operable to transform the microwaves into heat energy since no electrical interconnection within the susceptor <NUM> is required. Furthermore, provision of the relatively light weight susceptor(s) <NUM> and waveguide(s) <NUM>, 48B may reduce aircraft weight by obviating the need for ducting and valve associated with a traditional forced hot air anti-icing system.

<FIG> illustrates an inlet structure <NUM> of a nacelle for an aircraft propulsion system; e.g., a turbofan or a turbojet propulsion system. This inlet structure <NUM> includes an inlet lip <NUM>, an inner barrel <NUM> and an outer barrel <NUM>. The inlet lip <NUM> forms a leading edge <NUM> of the inlet structure <NUM>. The inner barrel <NUM> is connected to a radial inner end <NUM> of the inlet lip <NUM>, and at least partially forms an outer peripheral boundary of an inlet duct <NUM> into the aircraft propulsion system. The outer barrel <NUM> is connected to a radial outer end <NUM> of the inlet lip <NUM>, and circumscribes the inner barrel <NUM>.

The inlet structure <NUM> of <FIG> is configured with the exterior skin <NUM>. This exterior skin <NUM> may form at least an inner portion of the inlet lip <NUM>. The exterior skin <NUM> of <FIG>, for example, extends axially along an axial centerline <NUM> of the aircraft propulsion system from (or about) the leading edge <NUM> to (or towards) the radial inner end <NUM> of the inlet lip <NUM>. The exterior skin <NUM> may also extend axially along the axial centerline <NUM> from (or about) the leading edge <NUM> to (or towards) the radial outer end <NUM> of the inlet lip <NUM>. The exterior skin <NUM> extends circumferentially about (e.g., completely around) the axial centerline <NUM>. Alternatively, the inlet structure <NUM> may be configured with a plurality of the exterior skins <NUM>, where each exterior skin <NUM> forms an arcuate segment of the inlet lip <NUM>.

While the exterior skin <NUM> and the thermal anti-icing system <NUM> is described above as being configured with the inlet structure <NUM>, the present disclosure is not limited to such an exemplary application. Rather, the exterior skin <NUM> and the thermal anti-icing system <NUM> of the present disclosure may be configured with any aircraft structure which would benefit from including de-icing capability. Furthermore, the exterior skin <NUM> and the thermal anti-icing system <NUM> of the present disclosure may alternatively be configured for non-aircraft applications. For example, the exterior skin <NUM> may form an exterior surface of an airfoil such as, but not limited to, a wind turbine blade. In another example, the exterior skin <NUM> may for an exterior surface of another type of vehicle that would benefit from anti-icing; e.g., an automobile, a boat, etc..

Claim 1:
An assembly (<NUM>) for a structure, comprising:
a composite skin (<NUM>) extending between an exterior surface (<NUM>) and an interior surface (<NUM>); and
a thermal anti-icing system (<NUM>) comprising a susceptor (<NUM>) and a waveguide, the susceptor (<NUM>) and the waveguide (44A, 44B) integrated into the composite skin (<NUM>) between the exterior surface (<NUM>) and the interior surface (<NUM>), and the waveguide (44A, 44B) configured to direct microwaves to the susceptor (<NUM>) for melting and/or preventing ice accumulation on the exterior surface (<NUM>).