Abstract: A fan for a gas turbine engine includes: an annular casing; a disk disposed inside the casing and mounted for rotation about an axial centerline, the disk including a row of fan blades extending radially outwardly therefrom; each of the fan blades including an airfoil having circumferentially opposite pressure and suction sides extending radially in span from a root to a tip, and extending axially in chord between spaced-apart leading and trailing edges, with the airfoils defining corresponding flow passages therebetween for pressurizing air; the row including no more than 21 and no less than 13 of the fan blades; and wherein each of the fan blades has a solidity defined by a ratio of the airfoil chord over a circumferential pitch of the fan blades, measured at 60% of a radial distance from the root to the tip, of less than about 1.6.

Abstract: A turbo machine, a computer-implemented method, and a computer system for operating a compressor assembly are provided. The method includes comparing a first data set and a second data set to determine a first correlation factor, comparing the first correlation factor to a first threshold that at least partially determines whether a stall precursor exists, removing mean values from the first data set and the second data set, comparing the first data set and the second data set each removed of mean values to determine a second correlation factor, and comparing the second correlation factor to the first threshold, and classifying the stall precursor as either a spike stall precursor, a modal stall precursor, or a combination stall precursor.

Abstract: A shroud assembly for a turbine engine having a centerline axis. The shroud assembly having a shroud hanger, at least one shroud segment, and at least one biasing element extending between the two. The biasing element configured to radially bias the at least one shroud segment between an outboard position and an inboard position radially outward from the outboard position with respect to the centerline axis.

Abstract: An aircraft equipped with a distributed unducted fan propulsion system is provided. In one aspect, an aircraft includes a body defining a lateral centerline that separates the body into a first side and a second side. One or more first unducted fans are mounted to the first side of the body. The one or more first unducted fans are rotatable in a first direction. One or more second unducted fans are mounted to the second side of the body. The one or more second unducted fans are rotatable in a second direction that is opposite the first direction.

Abstract: An aircraft equipped with a distributed fan propulsion system and methods of operating such aircraft are provided. In one aspect, an aircraft includes a wing having a top surface and a bottom surface. The aircraft also has a distributed propulsion system that includes a suction fan array having one or more fans mounted to the wing and a pressure fan array having one or more fans mounted to the wing. The fans of the suction fan array are each positioned primarily above the top surface of the wing and the fans of the pressure fan array are each positioned primarily below the bottom surface of the wing. The fans of the suction fan array are controllable independent of the fans of the pressure fan array so that the air pressure above and/or below the wing can be locally controlled, allowing for adjustment of lift on the wing.

Abstract: A heat exchanger apparatus includes: spaced-apart peripheral walls extending between an inlet and an outlet, the peripheral walls collectively defining a flow channel which includes a diverging portion downstream of the inlet, in which a flow area is greater than a flow area at the inlet; a plurality of spaced-apart fins disposed in the flow channel, each of the fins having opposed side walls extending between an upstream leading edge and a downstream trailing edge, wherein the fins divide at least the diverging portion of the flow channel into a plurality of side-by-side flow passages; and a heat transfer structure disposed within at least one of the fins.

Abstract: A shroud assembly for a gas turbine engine includes: at least one shroud hanger; an annular array of shroud segments carried by the child hanger at least one and arrayed about an engine centerline axis, each of the shroud segments having a flowpath side defining a portion of a primary engine flowpath, and an opposed backside facing the at least one shroud hanger, wherein the shroud segment is mounted to the at least one shroud hanger such that it is movable in a radial direction between an inboard position and an outboard position, in response to a balance of gas pressures prevailing on the flowpath side and the backside; and biasing means which urge each of the shroud segments towards one of the positions.

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: An aircraft defines a vertical direction and includes a fuselage and a propulsion system comprising a power source and a plurality of vertical thrust electric fans driven by the power source. A wing extends from the fuselage. The plurality of vertical thrust electric fans are arranged along a length of the wing along a lengthwise direction of the wing. The wing comprises a diffusion assembly along the lengthwise direction of the wing and includes a first diffusion member positioned downstream of at least one of the plurality of vertical thrust electric fans. The first diffusion member defines a curved shape relative to a longitudinal direction of the aircraft. The longitudinal direction is generally perpendicular to the lengthwise direction of the wing.

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 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: 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: 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 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.