Abstract: A fan for a gas turbine engine is provided. The fan includes a rotor including at least one rotor stage having a rotatable disk defining a flowpath surface and an array of rotor airfoils extending outward from the flowpath surface; an array of splitter airfoils extending outward from the flowpath surface, wherein the splitter airfoils and the rotor airfoils are disposed in a sequential arrangement; and a shroud extending between the rotor airfoils and the splitter airfoils.

Abstract: An aircraft includes a fuselage; a propulsion system including a power source and a vertical thrust propulsor driven by the power source; and a wing extending from the fuselage, the vertical thrust propulsor positioned on or at least partially within the wing, the wing including a diffusion assembly, the diffusion assembly including at least one diffusion member fixed in position and located downstream of the vertical thrust propulsor for diffusing an airflow from the vertical thrust propulsor.

Abstract: An aircraft includes a fuselage; a propulsion system including a power source and a plurality of vertical thrust electric fans driven by the power source; and a wing extending from the fuselage. The plurality of vertical thrust electric fans are arranged along the wing, the wing including one or more components being moveable to selectively expose the plurality of vertical thrust electric fans, the wing further including a diffusion assembly positioned downstream of at least one vertical thrust electric fan of the plurality of vertical thrust electric fans, the diffusion assembly defining a diffusion area ratio greater than 1:1 and less than about 2:1.

Abstract: An aircraft includes a fuselage; a propulsion system including a power source and a plurality of vertical thrust electric fans driven by the power source; and a wing extending from the fuselage. The plurality of vertical thrust electric fans are arranged along a length of the wing, the wing including a variable geometry assembly moveable generally along a horizontal direction between a forward thrust position and a vertical thrust position, the variable geometry assembly at least partially covering at least one vertical thrust electric fan of the plurality of vertical thrust electric fans when in the forward thrust position and at least partially exposing the at least one vertical thrust electric fan when in the vertical thrust position.

Abstract: An aircraft includes a fuselage; a propulsion system including a power source and a plurality of vertical thrust electric fans driven by the power source; and a wing extending from the fuselage. The plurality of vertical thrust electric fans are arranged along a length of the wing, the wing including a variable geometry assembly extending along the length of the wing and moveable between a forward thrust position and a vertical thrust position, the variable geometry assembly at least partially covering the plurality of vertical thrust electric fans when in the forward thrust position and at least partially exposing the plurality of vertical thrust electric fans when in the vertical thrust position.

Abstract: A variable-cycle compressor includes: an axial-flow compressor, a flowpath downstream of the compressor, and at least one variable-cycle device operable to vary a choked flow capacity of the downstream flowpath. The compressor includes: a rotor having at least one rotor stage including a rotatable disk defining a rotor flowpath surface and an array of axial-flow rotor airfoils extending outward from the flowpath surface; at least one stator stage including a wall defining a stator flowpath surface, and an array of axial-flow stator airfoils extending away from the stator flowpath surface. At least one stage includes splitter airfoils alternating with the rotor or stator airfoils of the corresponding stage. At least one of a chord dimension of the splitter airfoils and a span dimension of the splitter airfoils is less than the corresponding dimension of the airfoils of the at least one stage.

Abstract: A single unducted rotor engine is provided. The single unducted rotor engine defines an axial direction and a radial direction, the engine including: a power source; a casing surrounding the power source; an unducted rotor assembly driven by the power source comprising a single row of rotor blades; and an outlet guide vane assembly comprising a plurality of pairs of outlet guide vanes, each pair of the plurality of pairs of outlet guide vanes including first outlet guide vane extending from the casing at a location downstream from the single row of rotor blades of the unducted rotor assembly and a second outlet guide vane also positioned downstream from the single row of rotor blades of the unducted rotor assembly; wherein the first outlet guide vane of each pair of outlet guide vanes defines a first geometry, wherein the second outlet guide vane of each pair of outlet guide vanes defines a second geometry, and wherein the first geometry is not equal to the second geometry.

Abstract: A method for operating a vertical takeoff and landing aircraft includes modifying a first variable component of a wing associated with a first portion of the plurality of vertical thrust electric fans relative to a second variable component of the wing associated with a second portion of the plurality of vertical thrust electric fans to adjust an exposure ratio of the first portion of the plurality of vertical thrust electric fans relative to the second portion of the plurality of vertical thrust electric fans.

Abstract: A fan for a gas turbine engine is provided. The fan includes a rotor including at least one rotor stage having a rotatable disk defining a flowpath surface and an array of rotor airfoils extending outward from the flowpath surface; an array of splitter airfoils extending outward from the flowpath surface, wherein the splitter airfoils and the rotor airfoils are disposed in a sequential arrangement; and a shroud extending between the rotor airfoils and the splitter airfoils.

Abstract: A method of controlling a transition from a laminar flow to a turbulent flow for an airfoil of a turbomachine includes forming an airfoil. The airfoil defines a span extending between a root and a tip and a chord extending between a leading edge and a trailing edge. The airfoil includes a suction side surface and a pressure side surface, opposite the suction side surface, each extending between the leading edge, the trailing edge, the root, and the tip. The method also includes finishing a majority of the suction and pressure side surfaces in order to form a finished surface. The finished surface defines a first roughness. The method additionally includes leaving at least a portion of the suction side surface and/or pressure side surface unfinished in order to form an unfinished surface. Furthermore, the unfinished surface defines a second roughness greater than the first roughness.

Abstract: A method is provided of operating a single unducted rotor engine, the single unducted rotor engine comprising a single stage of unducted rotor blades. The method includes operating the single unducted rotor engine to define a flight speed, V0, in a length unit per second and an angular speed, n, in revolutions per second, the single stage of unducted rotor blades defining a diameter, D, in the length unit; wherein operating the single unducted rotor engine comprises operating the single unducted rotor engine to define an advance ratio greater than 3.8 while operating the single unducted rotor engine at a net efficiency of at least 0.8, the advance ratio defined by the equation V0/(n×D).

Abstract: A propulsion system is provided, the propulsion system including a rotor assembly configured to rotate relative to the engine centerline axis, and wherein one or more blades of the rotor assembly are configured to rotate along a blade pitch angle axis. A vane assembly is positioned in aerodynamic relationship with the rotor assembly. The vane assembly includes one or more vanes, wherein each vane includes a vane pitch angle. A controller is configured to execute operations, the operations including moving each blade to a reverse thrust position about its respective blade pitch axis, and adjusting each vane about its respective vane pitch axis when the plurality of blades is in the reverse thrust position to modify an amount of reverse thrust generated by the propulsion system.

Abstract: An aircraft extending between a forward end and an aft end is provided. The aircraft includes an auxiliary power unit positioned proximate the aft end of the aircraft, the auxiliary power unit having an auxiliary power unit inlet duct and an auxiliary power unit exhaust duct, and a boundary layer ingestion fan positioned proximate the aft end of the aircraft, the boundary layer ingestion fan having a support shaft, wherein the auxiliary power unit exhaust duct extends through a portion of the support shaft of the boundary layer ingestion fan.

Abstract: A propulsion system according to aspects of the present disclosure is provided, the propulsion system including a rotor assembly with a plurality of blades extended radially relative to the engine centerline axis, and a vane assembly positioned in aerodynamic relationship with the rotor assembly. The vane assembly includes a plurality of vanes extended radially relative to the engine centerline axis, and the propulsion system includes a ratio of a quantity of blades to a quantity of vanes between 2:5 and 2:1.

Abstract: A unshrouded vane assembly for an unducted propulsion system includes a plurality of vanes which have non-uniform characteristics configured to generate a desired vane exit swirl angle.

Abstract: An apparatus and method of managing negative incidence of an airfoil are provided. The apparatus includes a row of vane pairs including a first row of main vanes extending radially inwardly from a stationary casing member and spaced circumferentially about a first axial location of the stationary casing member. The apparatus also includes a second row of auxiliary vanes extending radially inwardly from the stationary casing member and spaced circumferentially about a second axial location of the stationary casing member. The apparatus also includes a flow channel defined between a pressure side of each auxiliary vane and a suction side of an adjacent main vane proximate a leading edge of the adjacent main vane.

Abstract: An aircraft includes a fuselage; a wing coupled to, and extending from, the fuselage; and a hybrid-electric propulsion system. The hybrid-electric propulsion system includes a power source including a combustion engine and an electric generator; a plurality of vertical thrust electric fans integrated into the wing and oriented to generate thrust along the vertical direction, the plurality of vertical thrust electric fans arranged along a length of the wing and driven by the power source; and a forward thrust propulsor. The forward thrust propulsor it is selectively or permanently mechanically coupled to the combustion engine.

Abstract: An unducted thrust producing system, includes a rotating element, a stationary element. An inlet may be located forward or aft of the rotating element and the stationary element. An exhaust may be located forward, aft, or between the rotating element and the stationary element.

Abstract: A noise reducing airfoil defining a span extending between a root and a tip and a chord at each point along the span extending between a leading edge and a trailing edge. The airfoil includes a pressure side, a suction side, and a trailing edge sheath including an outer surface coupled to the trailing edge of the airfoil. The trailing edge sheath extends at least partially along the chord on the pressure and suction sides at each point along the span within the trailing edge sheath. The trailing edge sheath defines a fluid passageway extending along at least a portion of the span. Further, the trailing edge sheath defines at least one aperture on at least one of the pressure side, the suction side, or trailing edge fluidly coupling the fluid passageway to the outer surface.

Abstract: A unshrouded vane assembly for an unducted propulsion system includes a plurality of vanes which have non-uniform characteristics configured to generate a desired vane exit swirl angle.