Abstract: An after-fan system for an engine may comprise an after-fan turbine an electrical generator operationally coupled to the after-fan turbine, and an electric motor electrically coupled to the electrical generator. The electrical generator may be configured to generate an electrical current in response to rotation of the after-fan turbine. The electric motor may be configured to generate torque.

Abstract: An after-fan system for an engine may comprise an after-fan turbine an electrical generator operationally coupled to the after-fan turbine, and an electric motor electrically coupled to the electrical generator. The electrical generator may be configured to generate an electrical current in response to rotation of the after-fan turbine. The electric motor may be configured to generate torque.

Abstract: A nacelle assembly of a gas turbine engine includes an annular structure defining a central axis, and having a radially inward surface and a radially outward surface, the radially inward surface at least partially defining a bypass duct. An aft portion of the radially inward surface at least partially defines an axially extending convergent-divergent exit nozzle. A secondary nozzle flap is radially spaced from the aft portion of the radially inward surface. The secondary nozzle flap and the aft portion of the radially inward surface define a secondary bypass duct therebetween. The secondary nozzle flap is operably connected to the annular structure such that the secondary nozzle flap is selectably movable relative to the aft portion of the radially inward surface, thereby changing a cross-sectional area of a secondary bypass duct exit.

Abstract: A nacelle may comprise an inlet cowling comprising an inlet cowling aft edge having an aft edge length; a boat tail cowling comprising a boat tail cowling forward edge having a forward edge length, wherein the boat tail cowling forward edge is disposed adjacent to the inlet cowling aft edge. The forward edge length may be shorter than the aft edge length, forming a step being defined by a portion of the inlet cowling aft edge that is radially outward of the boat tail cowling forward edge. The nacelle may further comprise a transition fairing coupled to the boat tail cowling, wherein the transition fairing comprises a fairing forward edge disposed adjacent to the inlet cowling aft edge and a fairing ramp surface spanning between the inlet cowling aft edge and a boat tail cowling external surface.

Abstract: A nacelle may comprise an inlet cowling defining an inlet of the nacelle, wherein the inlet cowling comprises an inlet cowling maximum point and an inlet cowling aft edge, wherein the inlet cowling aft edge comprises an aft edge length; and a boat tail cowling disposed aft of the inlet cowling, wherein the boat tail cowling comprises a boat tail cowling forward edge having a forward edge length, and wherein the boat tail cowling forward edge is disposed adjacent to the inlet cowling aft edge. The forward edge length may be smaller than the aft edge length, forming a step, the step being defined by a portion of the inlet cowling aft edge that is radially outward of the boat tail cowling forward edge.

Abstract: A nacelle may comprise an inlet cowling comprising an inlet cowling aft edge having an aft edge length; a boat tail cowling comprising a boat tail cowling forward edge having a forward edge length, wherein the boat tail cowling forward edge is disposed adjacent to the inlet cowling aft edge. The forward edge length may be shorter than the aft edge length, forming a step being defined by a portion of the inlet cowling aft edge that is radially outward of the boat tail cowling forward edge. The nacelle may further comprise a transition fairing coupled to the boat tail cowling, wherein the transition fairing comprises a fairing forward edge disposed adjacent to the inlet cowling aft edge and a fairing ramp surface spanning between the inlet cowling aft edge and a boat tail cowling external surface.

Abstract: A nacelle for a gas turbine engine includes a ring shaped body defining a center axis and having a radially outward surface and a radially inward surface. An aft portion of the radially inward surface includes an axially extending convergent-divergent exit nozzle. An axially extending secondary duct passes through the nacelle in the convergent-divergent exit nozzle. The axially extending secondary duct includes an inlet at a convergent portion of the convergent-divergent exit nozzle and an outlet at a divergent portion of the convergent-divergent exit nozzle.

Abstract: An after-fan system for an engine may comprise an after-fan turbine an electrical generator operationally coupled to the after-fan turbine, and an electric motor electrically coupled to the electrical generator. The electrical generator may be configured to generate an electrical current in response to rotation of the after-fan turbine. The electric motor may be configured to generate torque.

Abstract: A nacelle assembly of a gas turbine engine includes an annular structure defining a central axis, and having a radially inward surface and a radially outward surface, the radially inward surface at least partially defining a bypass duct. An aft portion of the radially inward surface at least partially defines an axially extending convergent-divergent exit nozzle. A secondary nozzle flap is radially spaced from the aft portion of the radially inward surface. The secondary nozzle flap and the aft portion of the radially inward surface define a secondary bypass duct therebetween. The secondary nozzle flap is operably connected to the annular structure such that the secondary nozzle flap is selectably movable relative to the aft portion of the radially inward surface, thereby changing a cross-sectional area of a secondary bypass duct exit.

Abstract: A gas turbine engine according to an exemplary embodiment of this disclosure includes, among other possible things, a fan including a plurality of fan blades rotatable about an axis, a plurality of inlet guide vanes mounted forward of the plurality of fan blades, the plurality of inlet guide vanes selectively rotatable about the axis independent of the plurality of fan blades; and a motor for controlling rotation of the plurality of inlet guide vanes about the axis.

Abstract: A nacelle may comprise an inlet cowling comprising an inlet cowling aft edge having an aft edge length; a boat tail cowling comprising a boat tail cowling forward edge having a forward edge length, wherein the boat tail cowling forward edge is disposed adjacent to the inlet cowling aft edge. The forward edge length may be shorter than the aft edge length, forming a step being defined by a portion of the inlet cowling aft edge that is radially outward of the boat tail cowling forward edge. The nacelle may further comprise a transition fairing coupled to the boat tail cowling, wherein the transition fairing comprises a fairing forward edge disposed adjacent to the inlet cowling aft edge and a fairing ramp surface spanning between the inlet cowling aft edge and a boat tail cowling external surface.

Abstract: Core housings for gas turbine engines are described. The core housings include a housing surface defining an exterior surface of the core housing, a housing aperture arranged on the housing surface, the housing aperture configured to enable fluid communication between an external environment and an interior of the core housing, a drainage hole arranged upstream relative to the housing aperture, the drainage hole configured to enable draining of a fluid from an interior of the core housing to the external environment, and a redirection device arranged to receive a fluid from the drainage hole and direct such fluid away from the housing aperture.

Abstract: A method to predict an onset of flow separation from a surface of an inner barrel of a nacelle is disclosed. In various embodiments, the method includes determining a static pressure distribution about the inner barrel surface of the nacelle; determining a mean static pressure value and a minimum static pressure value using the static pressure distribution; determining a separation indicator value using the mean static pressure value and the minimum static pressure value; and comparing the separation indicator value against a separation threshold value.

Abstract: A nacelle may comprise an inlet cowling defining an inlet of the nacelle, wherein the inlet cowling comprises an inlet cowling maximum point and an inlet cowling aft edge, wherein the inlet cowling aft edge comprises an aft edge length; and a boat tail cowling disposed aft of the inlet cowling, wherein the boat tail cowling comprises a boat tail cowling forward edge having a forward edge length, and wherein the boat tail cowling forward edge is disposed adjacent to the inlet cowling aft edge. The forward edge length may be smaller than the aft edge length, forming a step, the step being defined by a portion of the inlet cowling aft edge that is radially outward of the boat tail cowling forward edge.

Abstract: An after-fan system for a gas turbine engine includes a variable pitch fan exit guide vane array. An after-fan turbine downstream of the variable pitch fan exit guide vane array and a control operable to vary a pitch of the variable fan exit guide vane array. A method of generating thrust for a gas turbine engine includes rotating a fan section with an array of fan blades; rotating an after-fan turbine downstream of the fan section; and varying a pitch of a variable fan exit guide vane array downstream of the fan section and upstream of the after-fan turbine.

Abstract: A nacelle may comprise an inlet cowling defining an inlet of the nacelle, wherein the inlet cowling comprises an inlet cowling maximum point and an inlet cowling aft edge, wherein the inlet cowling aft edge comprises an aft edge length; and a boat tail cowling disposed aft of the inlet cowling, wherein the boat tail cowling comprises a boat tail cowling forward edge having a forward edge length, and wherein the boat tail cowling forward edge is disposed adjacent to the inlet cowling aft edge. The forward edge length may be smaller than the aft edge length, forming a step, the step being defined by a portion of the inlet cowling aft edge that is radially outward of the boat tail cowling forward edge.

Abstract: A gas turbine engine according to an exemplary embodiment of this disclosure includes, among other possible things, a fan including a plurality of fan blades rotatable about an axis, a plurality of inlet guide vanes mounted forward of the plurality of fan blades, the plurality of inlet guide vanes selectively rotatable about the axis independent of the plurality of fan blades; and a motor for controlling rotation of the plurality of inlet guide vanes about the axis.

Abstract: A gas turbine engine is disclosed with a first spool having a first turbine connected to a first compressor through a first rotatable shaft; a second spool having a second turbine connected to a second compressor through a second rotatable shaft; and a gearbox having a power input port coupled to each of the first and second shafts and a power output port connected to a third shaft, wherein the rotational speed of the third shaft is lower than the rotational speed of each of the first and second shafts.

Abstract: Core housings for gas turbine engines are described. The core housings include a housing surface defining an exterior surface of the core housing, a housing aperture arranged on the housing surface, the housing aperture configured to enable fluid communication between an external environment and an interior of the core housing, a drainage hole arranged upstream relative to the housing aperture, the drainage hole configured to enable draining of a fluid from an interior of the core housing to the external environment, and a redirection device arranged to receive a fluid from the drainage hole and direct such fluid away from the housing aperture.

Abstract: A method to predict an onset of flow separation from a surface of an inner barrel of a nacelle is disclosed. In various embodiments, the method includes determining a static pressure distribution about the inner barrel surface of the nacelle; determining a mean static pressure value and a minimum static pressure value using the static pressure distribution; determining a separation indicator value using the mean static pressure value and the minimum static pressure value; and comparing the separation indicator value against a separation threshold value.