A gas turbine engine includes a main compressor section having a downstream most location, and a turbine section, with both the main compressor section and the turbine section housing rotatable components. A first tap taps air compressed by the main compressor section at an upstream location upstream of the downstream most location. The first tap passes through a heat exchanger, and to a cooling compressor. Air downstream of the cooling compressor is selectively connected to reach at least one of the rotatable components. The cooling compressor is connected to rotate at a speed proportional to a rotational speed in one of the main compressor section and the turbine section. A valve system includes a check valve for selectively blocking flow downstream of the cooling compressor from reaching the at least one rotatable component. A dump valve selectively dumps air downstream of the cooling compressor. A method is also disclosed.

An inlet system for a gas turbine includes an integrated inlet bleed heat system, wherein the inlet bleed design is integrated in, e.g., a silencer or inlet.

A turbomachine includes a casing having an inlet end opposite an outlet end along a longitudinal axis of the casing; a shaft assembly provided within the casing, the shaft assembly extending from the inlet end to the outlet end; a plurality of rotating impellers extending radially outward from the shaft assembly; and a communication channel defined between two adjacent impellers to permit a backflow of fluid from a diffuser channel of a downstream impeller to a return channel of an adjacent upstream impeller.

A centrifugal compressor for a turbocharger includes a passive or semi-passive inlet-adjustment mechanism in an air inlet for the compressor, operable to move between an open position and a closed position solely by aerodynamic forces on the mechanism. The inlet-adjustment mechanism includes a plurality of flexible vanes collectively forming a duct, and an effective diameter of the air inlet at the inducer portion of the compressor wheel is determined by a trailing edge inside diameter of the duct. The vanes are movable solely or in part by aerodynamic forces exerted on the vanes by the air flowing to the compressor wheel. The duct has a tapering configuration when the vanes are in a relaxed state, but under aerodynamic force the vanes flex outwardly and increase the trailing edge inside diameter of the duct, thereby increasing an effective diameter of the air inlet.

Axially adjacent annular booster bleed aft and forward plenums with annular common wall therebetween extend radially outwardly from transition duct. Variable bleed valve includes bleed valve door in bleed inlet in transition duct, attached to rotatable valve body rotatable about axis of rotation, operable to open and close bleed inlet to aft plenum. Rotatable plenum door clocked or circumferentially spaced apart from variable bleed valve door and attached to rotatable valve body, operable to close and open up and control flow through an inter plenum aperture in common wall. Aft and forward bleed exhaust ducts extend from booster bleed aft and forward plenums to bypass flow path. One or more heat exchanger, such as from thermal management system, may be disposed in the bleed exhaust ducts. Heat exchangers may be used for cooling oil for power gear box and/or engine bearings, air conditioning, or variable frequency generator.

Systems and methods for adjusting airflow distortion in a gas turbine engine using a translating inlet assembly are provided. In one embodiment, a core engine of a gas turbine engine can include a compressor section, a combustion section, and a turbine section in series flow and defining at least in part an engine airflow path. The compressor section can include an inner flowpath surface. A core casing can enclose the core engine. A forward end of the core casing can include a translating inlet assembly moveable between a first position and a second position. The translating inlet assembly and the inner flowpath surface can together define an inlet to an engine airflow path. A translating inlet assembly can define a first inlet area in the first position and a second inlet area in the second position, the first inlet area being greater than the second inlet area.

A method and system for a turbofan gas turbine engine system is provided. The gas turbine engine system includes a variable pitch fan (VPF) assembly coupled to a first rotatable shaft and a low pressure compressor LPC coupled to a second rotatable shaft. The LPC including a plurality of variable pitch stator vanes interdigitated with rows of blades of a rotor of the LPC. The gas turbine engine system also includes a speed reduction device coupled to said first rotatable shaft and said second rotatable shaft. The gas turbine engine system further includes a modulating pressure relief valve positioned between an outlet of said LPC and a bypass duct and a controller configured to schedule a position of said plurality of variable pitch stator vanes and said modulating pressure relief valve in response to an operational state of said turbofan gas turbine engine system and a temperature associated with said LPC.

Methods and systems for controlling a bleed-off valve of a gas turbine engine are described. The method comprises maintaining a first bleed-off valve associated with a first compressor of the gas turbine engine at least partially open upon detection of an unintended engine disturbance causing a drop in pressure of a combustion chamber of the engine; monitoring a rotor acceleration of the first compressor; and controlling closure of the first bleed-off valve when the rotor acceleration of the first compressor reaches a first threshold for a first duration.

Systems and methods for adjusting airflow distortion in a gas turbine engine using a secondary airflow passage assembly are disclosed. A gas turbine engine can include a compressor section, a combustion section, and a turbine section in series flow and defining at least in part an engine airflow path. A casing can enclose the gas turbine engine and be at least partially exposed to a bypass airflow. The gas turbine engine can further include a secondary airflow passage assembly comprising a door and a duct, the duct defining an inlet located on the casing, the duct defining an outlet in airflow communication with the engine airflow path, the duct comprising an airflow passage extending between the inlet and outlet. The door can be moveable between an open and closed position to allow a portion of the bypass airflow to flow through the airflow passage to adjust airflow distortion.

A centrifugal compressor diffuser (42) includes a plurality of diffuser flow passages (22) extending through an annular diffuser housing (20) and circumferentially bounded by diffuser vanes (23) and axially bounded by forward and aft walls (101, 100). A diffuser boundary layer bleed (96) for the passages may include boundary layer bleed apertures (106) or slots (130) disposed through the forward wall (101) and a downstream facing wall (142) canted at an acute cant angle to a downstream diffuser airflow direction (103) in the passages. Diffuser bleed flow (112) is bled from a diffuser boundary layer. Boundary layer bleed apertures can be located downstream of throat sections (28) of the flow passages near pressure sides of the vanes. A centrifugal compressor (18) may include the diffuser surrounding an annular centrifugal compressor impeller (32) and apparatus for flowing impeller bleed flow (102) from a radial clearance between an impeller tip (36) and a diffuser annular inlet (27) with diffuser bleed flow either mixed or separately to cool a turbine (16).