Abstract: Vehicles, environmental control systems, and methods for operating an environmental control system are provided. In one example, the environmental control system (ECS) includes an ECS refrigeration unit that is configured to receive ambient air and a first portion and a second portion of hot bleed air. The ECS refrigeration unit is operable to indirectly exchange heat between the first portion of the hot bleed air and the ambient air to form a partially cooled, hot air stream, and to compress, further indirect heat exchange, and expand the partially cooled, hot air stream to form a cooled and expanded air stream. A low limit valve control regulates a low limit valve to control a rate of introduction of the second portion of the hot bleed air to the cooled and expanded air stream to form a combined air stream that when exiting the ECS refrigeration unit is a sub-freezing air stream.

Abstract: An assembly is provided for an aircraft propulsion system. This assembly includes a gas turbine engine and a vapor absorption refrigeration system. The gas turbine engine includes a turbine section. The vapor absorption refrigeration system is configured to be driven by waste heat energy received from the turbine section. The vapor absorption refrigeration system includes a condenser.

Abstract: Vehicles, humidification systems for a vehicle, and methods for humidifying an interior of a vehicle are provided. In one example, the vehicle includes a vehicle structure at least partially surrounding an interior containing interior air. A humidification system is in fluid communication with an air stream and the interior. The humidification system includes a humidifier configured to humidify the air stream to form a humidified air stream that is fluidly communicated to the interior. A water recovery zone is in fluid communication with the interior to receive the interior air and is configured to condense and separate water from the interior air. The water recovery zone is further configured to be in fluid communication with the humidifier and to provide the water to the humidifier.

Abstract: A vane for use in a gas turbine engine includes an airfoil having a suction side and a pressure side, and a transpirational flow acoustic liner disposed in the airfoil. The liner includes a face sheet defining a portion of an outer surface of the airfoil and having a plurality of first apertures, a segmented member coupled to the face sheet, and a backing sheet coupled to the segmented member the segmented member such that the segmented member is positioned between the face sheet and the backing sheet. The segmented member includes a plurality of chambers in fluid communication with the outer surface via the plurality of first apertures. The backing sheet has a plurality of second apertures.

Abstract: A compressor with negative coefficient of thermal expansion case material comprising a rotor having blades with tips, the case including an inner case comprising a negative coefficient of thermal expansion material, and a tip clearance located between the tips and the inner case; wherein the tip clearance is maintained responsive to a flow of air over the negative coefficient of thermal expansion material.

Abstract: A vane for use in a gas turbine engine includes an airfoil having a suction side and a pressure side, and a transpirational flow acoustic liner disposed in the airfoil. The liner includes a face sheet defining a portion of an outer surface of the airfoil and having a plurality of first apertures, a segmented member coupled to the face sheet, and a backing sheet coupled to the segmented member the segmented member such that the segmented member is positioned between the face sheet and the backing sheet. The segmented member includes a plurality of chambers in fluid communication with the outer surface via the plurality of first apertures. The backing sheet has a plurality of second apertures.

Abstract: A casing treatment comprising a hub having a surface, the hub being rotatable about an axis within a casing of a gas turbine engine compressor, at least one spiral groove formed in the surface extending axially relative to the axis, a stator blade fixed to the casing, wherein a tip of the stator blade is proximate to the at least one spiral groove.

Abstract: A stator vane for a gas turbine engine section includes a stator vane having an airfoil extending between a leading edge and a trailing edge. The airfoil has a suction side and a pressure side. There is at least one piezoelectric actuator for changing a shape of at least one of the leading edge and the trailing edge. A gas turbine engine is also disclosed.

Abstract: A gas turbine engine includes a plurality of blades circumferentially spaced from each other. A plurality of rings are spaced radially outward from the plurality of blade. At least one actuator is in mechanical communication with the plurality of rings for moving the plurality of rings in an axial direction to create an axial gap adjacent at least one of the plurality of rings.

Abstract: A compressor for use in a gas turbine engine including: an airfoil configured to rotate about an engine central longitudinal axis of the gas turbine engine; a casing, the casing including a radially inward surface; and a groove located within the casing opposite the airfoil, the groove is recessed in a radially outward direction from the radially inward surface of the casing, wherein the groove is defined by a forward groove wall, an aft groove wall opposite the forward groove wall, and a base groove interposed between the forward groove wall and the aft groove wall, and wherein the forward groove wall is operably shaped to generate an aft directed jet.

Abstract: A morphing aerodynamic control surface geometry comprising a control surface having an articulated portion comprising a flexible skin coupled at an exterior of the articulated portion, the flexible skin comprising opposed interlocking elements sandwiched within a flexible polymer coupled to the interlocking elements; wherein the flexible skin is configured compliant responsive to an articulation of the articulated portion.

Abstract: An assembly is provided for an aircraft propulsion system. This assembly includes a gas turbine engine and a vapor absorption refrigeration system. The gas turbine engine includes a turbine section. The vapor absorption refrigeration system is configured to be driven by waste heat energy received from the turbine section. The vapor absorption refrigeration system includes a condenser.

Abstract: A compressor with negative coefficient of thermal expansion case material comprising a rotor having blades with tips, the case including an inner case comprising a negative coefficient of thermal expansion material, and a tip clearance located between the tips and the inner case; wherein the tip clearance is maintained responsive to a flow of air over the negative coefficient of thermal expansion material.

Abstract: A gas turbine engine includes an engine core having a compressor section, a combustor fluidly connected to the compressor section, and a turbine section fluidly connected to the combustor section. At least one compressor bleed connects a compressor flowpath with a first cooled cooling air path. The first cooled cooling air path includes a supplementary coolant injector connected to a supplementary coolant supply. The cooled cooling air path including a portion exterior to the engine core.

Abstract: A method of operating a turbofan engine includes coupling an electric motor to drive a fan rotatable within a nacelle, detecting an in-flight operating condition indicative of an increase in drag, and driving rotation of the fan with the electric motor to redirect a flow of air through the nacelle to reduce drag. A turbofan engine is also disclosed.

Abstract: A stator vane for a gas turbine engine section includes a stator vane having an airfoil extending between a leading edge and a trailing edge. The airfoil has a suction side and a pressure side. There is at least one piezoelectric actuator for changing a shape of at least one of the leading edge and the trailing edge. A gas turbine engine is also disclosed.

Abstract: A variable vane assembly may comprise a first vane and a second vane. The first vane may comprise a first strut portion and a first flap portion. The first flap portion may be configured to pivot relative to the first strut portion. The second vane may comprise a second strut portion and a second flap portion. The second flap portion may be configured to pivot relative to the second strut portion. The first flap may be configured to pivot independently of the second flap.

Abstract: A gas turbine engine includes a plurality of blades circumferentially spaced from each other. A plurality of rings are spaced radially outward from the plurality of blade. At least one actuator is in mechanical communication with the plurality of rings for moving the plurality of rings in an axial direction to create an axial gap adjacent at least one of the plurality of rings.

Abstract: A compressor for use in a gas turbine engine including: an airfoil configured to rotate about an engine central longitudinal axis of the gas turbine engine; a casing, the casing including a radially inward surface; and a groove located within the casing opposite the airfoil, the groove is recessed in a radially outward direction from the radially inward surface of the casing, wherein the groove is defined by a forward groove wall, an aft groove wall opposite the forward groove wall, and a base groove interposed between the forward groove wall and the aft groove wall, and wherein the forward groove wall is operably shaped to generate an aft directed jet.

Abstract: A tandem fan for a boundary layer ingestion engine is disclosed. In various embodiments, the tandem fan includes a fan disk configured for rotation about a longitudinal axis; a primary fan blade extending radially from the fan disk, the primary fan blade having a primary fan blade span; and a secondary fan blade extending radially from the fan disk, the secondary fan blade having a secondary fan blade span within about ninety percent to about one-hundred percent of the primary fan blade span.