A gas turbine engine is provided. The gas turbine engine includes a turbomachine comprising a low speed spool; a rotor assembly coupled to the low speed spool; an electric machine mechanically coupled to the low speed spool at a connection point of the low speed spool; and a clutch positioned in the torque path of the low speed spool between the connection point and the rotor assembly

A gas turbine engine is provided. The gas turbine engine defines a radial direction. The engine includes: an airfoil positioned within an airflow and extending between a root end and a tip along the radial direction; and a mount coupled to or formed integrally with the root end of the airfoil for mounting the airfoil to the engine, the mount including an outer surface along the radial direction exposed to the airflow and defining an air-cooling channel extending between an inlet and an outlet, the inlet positioned on the outer surface of the mount.

A propulsion system according to aspects of the present disclosure is provided, the propulsion system including a rotor assembly with a plurality of blades extended radially relative to the engine centerline axis, and a vane assembly positioned in aerodynamic relationship with the rotor assembly. The vane assembly includes a plurality of vanes extended radially relative to the engine centerline axis, and the propulsion system includes a ratio of a quantity of blades to a quantity of vanes between 2:5 and 2:1.

A computing system for an unducted rotor engine with a variable pitch vane assembly in aerodynamic relationship with an unducted rotor assembly, including a sensor-based controller configured to execute a first set of operations and a model-based controller configured to execute a second set of operations. The first set of operations includes obtaining a first signal corresponding to a commanded low spool speed; obtaining a second signal indicative of a pitch angle corresponding to thrust output from the unducted rotor assembly and variable pitch vane assembly; generating a pitch feedback signal corresponding to a commanded adjustment to the pitch angle based at least on one or both of a variable blade pitch angle or a variable vane pitch angle. The second set of operations include obtaining a desired thrust output via a throttle input; determining, at least via a power management block, a commanded thrust output signal; receiving the commanded thrust output signal; and generating an output signal.

A propulsion system is provided, the propulsion system including a variable pitch rotor assembly including a plurality of blades coupled to a disk. The plurality of blades includes a first blade configured to articulate a first blade pitch separately from a second blade configured to articulate a second blade pitch. A vane assembly is positioned in aerodynamic relationship with the variable pitch rotor assembly. A core engine including a high speed spool and a low speed spool, wherein the low speed spool is operably coupled to the rotor assembly. One or more controllers is configured to execute operations. The operations include articulating the first blade of the rotor assembly, wherein articulating the first blade alters the first blade pitch, and articulating the second blade of the rotor assembly, wherein articulating the second blade alters the second blade pitch.

A method is provided of operating a single unducted rotor engine, the single unducted rotor engine comprising a single stage of unducted rotor blades. The method includes operating the single unducted rotor engine to define a flight speed, V.sub.0, in a length unit per second and an angular speed, n, in revolutions per second, the single stage of unducted rotor blades defining a diameter, D, in the length unit; wherein operating the single unducted rotor engine comprises operating the single unducted rotor engine to define an advance ratio greater than 3.8 while operating the single unducted rotor engine at a net efficiency of at least 0.8, the advance ratio defined by the equation V.sub.0/(nD).

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.

A carbon dioxide cycle power generation system includes a first carbon dioxide storage configured to store a first portion of carbon dioxide and a second carbon dioxide storage configured to store a second portion of the carbon dioxide. The carbon dioxide cycle power generation system also includes a generator configured to generate electrical power based on a flow of at least part of the carbon dioxide between the first and second carbon dioxide storages. The carbon dioxide cycle power generation system is configured to cycle between different underwater depths in order to employ water pressure and/or water temperature in creating the flow of the at least part of the carbon dioxide through the generator. The second carbon dioxide storage includes an annular region surrounding a central region, where the annular region has a variable internal volume configured to receive at least part of the second portion of the carbon dioxide.

One example aspect of the present disclosure is directed to a method for operating a gas turbine engine. One example aspect of the present disclosure is directed to a method for operating a gas turbine engine, the gas turbine engine including at least a high pressure spool and a low pressure spool. The method includes causing, by one or more control devices, electrical power to be drawn from the high pressure spool and the low pressure spool into a power distribution system. The method includes determining, by the one or more control devices, a power adjustment event associated with the high pressure spool. The method includes initiating, by the one or more control devices, a power assist operation to redirect electrical power to the high pressure spool based at least in part on the power adjustment event.

A gas turbine engine includes a compressor section having a first portion and an aft portion. A compressor case clearance (CCC) control system is configured to adjust an amount of bleed air delivered to the front portion and the aft portion based on an in-flight phase of an aircraft. In response to invoking a first mode, the CCC control system delivers air to both the front portion and the aft portion. In response to invoking a second mode, the CCC control system reduces the amount of air delivered to the aft portion prior to transitioning from the cruise phase to the descent phase. Accordingly, clearance areas within the compressor section can be selectively increased during specific portions of the flight to avoid contact between blade tips and the engine case.