Abstract: A gas turbine engine includes a combustor having a combustor air inlet, an axial-centrifugal compressor, a shroud, a secondary flow duct, and a valve. The shroud surrounds at least a portion of the axial-centrifugal compressor and has a surge bleed plenum defined therein that is in fluid communication with, and receives compressed air from, the axial compressor outlet. The secondary airflow duct has a duct inlet that is in fluid communication with the surge bleed plenum, and a duct outlet that is in fluid communication with the combustor air inlet. The valve is mounted on the secondary airflow duct and is movable between a closed position, in which the secondary airflow duct does not provide fluid communication between the surge bleed plenum and the combustor air inlet, and an open position, in which the secondary airflow duct provides fluid communication between the surge bleed plenum and the combustor air inlet.

Abstract: A gas turbine engine includes a combustor having a combustor air inlet, an axial-centrifugal compressor, a shroud, a secondary flow duct, and a valve. The shroud surrounds at least a portion of the axial-centrifugal compressor and has a surge bleed plenum defined therein that is in fluid communication with, and receives compressed air from, the axial compressor outlet. The secondary airflow duct has a duct inlet that is in fluid communication with the surge bleed plenum, and a duct outlet that is in fluid communication with the combustor air inlet. The valve is mounted on the secondary airflow duct and is movable between a closed position, in which the secondary airflow duct does not provide fluid communication between the surge bleed plenum and the combustor air inlet, and an open position, in which the secondary airflow duct provides fluid communication between the surge bleed plenum and the combustor air inlet.

Abstract: Rotor systems and methods for improved performance with extended range to stall fabricated through the use of additive manufacturing. A rotor has blades that extend to tips and rotates about an axis. A casing fits over the rotor so that the tips are configured to pass proximate the casing when the rotor rotates. The casing channels a flow stream across the rotor. Grooves are defined in the casing and extend longitudinally at an acute angle relative to the axis. The grooves extend a distance upstream from a leading edge of the blades and over at least a portion of the blade tips so that the blade tips are configured to pass across the grooves when the rotor rotates.

Abstract: Multistage gas turbine engine (GTE) compressors having optimized stall enhancement feature (SEF) configurations are provided, as are methods for the production thereof. The multistage GTE compressor includes a series of axial compressor stages each containing a rotor mounted to a shaft of a gas turbine engine. In one embodiment, the method includes the steps or processes of selecting a plurality of engine speeds distributed across an operational speed range of the gas turbine engine, identifying one or more stall limiting rotors at each of the selected engine speeds, establishing an SEF configuration in which SEFs are integrated into the multistage GTE compressor at selected locations corresponding to the stall limiting rotors, and producing the multistage GTE compressor in accordance with the optimized SEF configuration.

Abstract: A gas turbine engine includes a shroud with an abradable section and a non-abradable section that cooperatively define a shroud surface. The gas turbine engine also includes a rotor that is supported for rotation within the shroud to generate an aft axial fluid flow. The rotor includes a blade with a blade tip that is crowned and that opposes the abradable section and the non-abradable section of the shroud surface. A crown area of the blade tip opposes the abradable section. A casing treatment feature is provided in the non-abradable section of the shroud to oppose the blade tip of the rotor.

Abstract: A method of manufacturing a multistage axial-centrifugal compressor for a gas turbine engine and a multistage axial-centrifugal compressor that includes a series of axial compressor stages each having a rotor mounted to a common shaft positioned upstream from a centrifugal compressor stage mounted to the common shaft. The method includes determining an operational rotor tip speed for each of the axial stages. The method includes comparing the operational rotor tip speed to a threshold range value and determining to machine an airfoil of the rotor for at least one of the axial stages by an arbitrary manufacturing approach based on the operational rotor tip speed as greater than the threshold range value. The method includes determining to machine an airfoil of the rotor for at least one of the axial stages by a flank manufacturing approach based on the operational rotor tip speed as less than the threshold range value.

Abstract: A compressor for a turbine engine includes a shroud having a grooved section including a plurality of groove segments extending radially into a shroud surface. A rotor assembly rotatably supported in the shroud includes a rotor hub and a plurality of rotor blades. Each rotor blade extends radially from the rotor hub and terminates at a blade tip, which is spaced from the shroud surface by a tip gap and defines a non-constant clearance region between a leading edge position and a medial chord position along the blade chord at the minimum tip clearance. The rotor blades generate an aft axial fluid flow through the shroud and the grooved section is formed in the shroud surface upstream of the medial chord positon within the non-constant clearance region for resisting a reverse axial fluid flow through the tip gap when the compressor section is operated at near stall conditions.

Abstract: Variable vane devices containing rotationally-driven translating vane structures are provided, as are methods for fabricating variable vane devices. In one embodiment, the variable vane device includes a flow assembly having a centerline, an annular flow passage extending through the flow assembly, cam mechanisms, and rotationally-driven translating vane structures coupled to the flow assembly and rotatable relative thereto. The translating vane structures include vane bodies positioned within the annular flow passage and angularly spaced about the centerline. During operation of the variable vane device, the cam mechanisms adjust translational positions of the vane bodies within the annular flow passage in conjunction with rotation of the translating vane structures relative to the flow assembly.

Abstract: A compressor section includes a shroud surface and a rotor with a blade tip that opposes the shroud surface. The rotor is configured to rotate within the shroud about an axis of rotation. Moreover, the compressor section includes a serration groove that is recessed into the shroud surface. The serration groove includes a forward portion with a forward transition and a forward surface that faces in the downstream direction. The forward transition is convexly contoured between the shroud surface and the forward surface. The serration groove includes a trailing portion with a taper surface and a trailing transition. The taper surface tapers inward as the taper surface extends from the forward surface to the trailing transition. The trailing transition is convexly contoured between the taper surface and the shroud surface.

Abstract: A gas turbine engine includes a shroud with an abradable section and a non-abradable section that cooperatively define a shroud surface. The gas turbine engine also includes a rotor that is supported for rotation within the shroud to generate an aft axial fluid flow. The rotor includes a blade with a blade tip that is crowned and that opposes the abradable section and the non-abradable section of the shroud surface. A crown area of the blade tip opposes the abradable section. A casing treatment feature is provided in the non-abradable section of the shroud to oppose the blade tip of the rotor.

Abstract: A gas turbine engine includes a shroud with an abradable section and a non-abradable section that cooperatively define a shroud surface. The gas turbine engine also includes a rotor that is supported for rotation within the shroud to generate an aft axial fluid flow. The rotor includes a blade with a blade tip that is crowned and that opposes the abradable section and the non-abradable section of the shroud surface. A crown area of the blade tip opposes the abradable section. A casing treatment feature is provided in the non-abradable section of the shroud to oppose the blade tip of the rotor.

Abstract: Rotor systems and methods for improved performance with extended range to stall fabricated through the use of additive manufacturing. A rotor has blades that extend to tips and rotates about an axis. A casing fits over the rotor so that the tips are configured to pass proximate the casing when the rotor rotates. The casing channels a flow stream across the rotor. Grooves are defined in the casing and extend longitudinally at an acute angle relative to the axis. The grooves extend a distance upstream from a leading edge of the blades and over at least a portion of the blade tips so that the blade tips are configured to pass across the grooves when the rotor rotates.

Abstract: Multistage gas turbine engine (GTE) compressors having optimized stall enhancement feature (SEF) configurations are provided, as are methods for the production thereof. The multistage GTE compressor includes a series of axial compressor stages each containing a rotor mounted to a shaft of a gas turbine engine. In one embodiment, the method includes the steps or processes of selecting a plurality of engine speeds distributed across an operational speed range of the gas turbine engine, identifying one or more stall limiting rotors at each of the selected engine speeds, establishing an SEF configuration in which SEFs are integrated into the multistage GTE compressor at selected locations corresponding to the stall limiting rotors, and producing the multistage GTE compressor in accordance with the optimized SEF configuration.

Abstract: A compressor section includes a shroud surface and a rotor with a blade tip that opposes the shroud surface. The rotor is configured to rotate within the shroud about an axis of rotation. Moreover, the compressor section includes a serration groove that is recessed into the shroud surface. The serration groove includes a forward portion with a forward transition and a forward surface that faces in the downstream direction. The forward transition is convexly contoured between the shroud surface and the forward surface. The serration groove includes a trailing portion with a taper surface and a trailing transition. The taper surface tapers inward as the taper surface extends from the forward surface to the trailing transition. The trailing transition is convexly contoured between the taper surface and the shroud surface.

Abstract: Multistage gas turbine engine (GTE) compressors having optimized stall enhancement feature (SEF) configurations are provided, as are methods for the production thereof. The multistage GTE compressor includes a series of axial compressor stages each containing a rotor mounted to a shaft of a gas turbine engine. In one embodiment, the method includes the steps or processes of selecting a plurality of engine speeds distributed across an operational speed range of the gas turbine engine, identifying one or more stall limiting rotors at each of the selected engine speeds, establishing an SEF configuration in which SEFs are integrated into the multistage GTE compressor at selected locations corresponding to the stall limiting rotors, and producing the multistage GTE compressor in accordance with the optimized SEF configuration.

Abstract: A method of manufacturing a multistage axial-centrifugal compressor for a gas turbine engine and a multistage axial-centrifugal compressor that includes a series of axial compressor stages each having a rotor mounted to a common shaft positioned upstream from a centrifugal compressor stage mounted to the common shaft. The method includes determining an operational rotor tip speed for each of the axial stages. The method includes comparing the operational rotor tip speed to a threshold range value and determining to machine an airfoil of the rotor for at least one of the axial stages by an arbitrary manufacturing approach based on the operational rotor tip speed as greater than the threshold range value. The method includes determining to machine an airfoil of the rotor for at least one of the axial stages by a flank manufacturing approach based on the operational rotor tip speed as less than the threshold range value.

Abstract: Variable stator vane assemblies and stator vanes thereof having a local swept leading edge are provided. The variable stator vane comprises an airfoil disposed between spaced apart inner and outer buttons centered about a rotational axis. The inner and outer buttons each having a button forward edge portion and the airfoil including leading and trailing edges, pressure and suction sides, and a root and a tip. The leading edge, at least a portion of which extends forward of the buttons, includes a local aft sweep at the tip, thereby forming a locally swept tip of the leading edge thereat. The button forward edge portion of the outer button is substantially vertically aligned with the locally swept tip of the leading edge. Methods are also provided for minimizing endwall leakage in the variable stator vane assembly using the same.

Abstract: A rotor blade comprises a mount and a blade that extends from the mount along a radial axis. The leading edge includes an indent segment. The leading edge has a leading edge radial length measured along the radial axis. The indent segment has an indent radial length measured along the radial axis. The indent segment has an indent depth. A first ratio of the indent radial length to the leading edge radial length is at most 0.5. A second ratio of the indent depth to the indent radial length is at least 0.05.

Abstract: A gas turbine engine includes a shroud with an abradable section and a non-abradable section that cooperatively define a shroud surface. The gas turbine engine also includes a rotor that is supported for rotation within the shroud to generate an aft axial fluid flow. The rotor includes a blade with a blade tip that is crowned and that opposes the abradable section and the non-abradable section of the shroud surface. A crown area of the blade tip opposes the abradable section. A casing treatment feature is provided in the non-abradable section of the shroud to oppose the blade tip of the rotor.

Abstract: A compressor for a turbine engine includes a shroud having a grooved section including a plurality of groove segments extending radially into a shroud surface. A rotor assembly rotatably supported in the shroud includes a rotor hub and a plurality of rotor blades. Each rotor blade extends radially from the rotor hub and terminates at a blade tip, which is spaced from the shroud surface by a tip gap and defines a non-constant clearance region between a leading edge position and a medial chord position along the blade chord at the minimum tip clearance. The rotor blades generate an aft axial fluid flow through the shroud and the grooved section is formed in the shroud surface upstream of the medial chord positon within the non-constant clearance region for resisting a reverse axial fluid flow through the tip gap when the compressor section is operated at near stall conditions.