A turboelectric distributed propulsion based on brushless doubly-fed machines (BDFMs) is provided, which minimizes power conversion, enhances mechanical reliability, and strengthens fault-tolerance capability of a DC-based propulsion system. A turboelectric distributed propulsion (TeDP) architecture using BDFMs for aviation applications, and a designed BDFM, inverter, and controller are provided. Simulations and systems are also provided.

A multi-engine aircraft includes a first engine drivingly engaged to a common rotatable load and a second engine drivingly engaged to the common rotatable load, the second engine having a bleed air system and a control system in communication with a compressed air switching system. The control system controls operation of the second engine and/or the compressed air switching system. The compressed air switching system includes a switching valve that is displaceable between at least a first position and a second position, the first position interconnecting a lower pressure inlet and a switch outlet, and the second position interconnecting a high pressure inlet and the switch outlet. The switch outlet is in communication with the bleed air system of the second engine. The control system actuates the switching valve to switch between the first and second positions.

A multi-engine aircraft includes a first engine drivingly engaged to a common rotatable load and a second engine drivingly engaged to the common rotatable load, the second engine having a bleed air system and a control system in communication with a compressed air switching system. The control system controls operation of the second engine and/or the compressed air switching system. The compressed air switching system includes a switching valve that is displaceable between at least a first position and a second position, the first position interconnecting a lower pressure inlet and a switch outlet, and the second position interconnecting a high pressure inlet and the switch outlet. The switch outlet is in communication with the bleed air system of the second engine. The control system actuates the switching valve to switch between the first and second positions.

Methods and systems of operating a gas turbine engine in a low-power condition are provided. In one embodiment, the method includes supplying fuel to a combustor by supplying fuel to a first fuel manifold and a second fuel manifold of the gas turbine engine. The method also includes, while supplying fuel to the combustor by supplying fuel to the first fuel manifold: stopping supplying fuel to the second fuel manifold; and supplying pressurized air to the second fuel manifold to flush fuel in the second fuel manifold into the combustor and hinder coking in the second fuel manifold and associated fuel nozzles.

Methods and systems of operating a gas turbine engine in a low-power condition are provided. In one embodiment, the method includes supplying fuel to a combustor by supplying fuel to a first fuel manifold and a second fuel manifold of the gas turbine engine. The method also includes, while supplying fuel to the combustor by supplying fuel to the first fuel manifold: stopping supplying fuel to the second fuel manifold; and supplying pressurized air to the second fuel manifold to flush fuel in the second fuel manifold into the combustor and hinder coking in the second fuel manifold and associated fuel nozzles.

A method of operating an engine of a multi-engine aircraft includes sequentially operating the engine through a plurality of cycles, each cycle including a breathing-in phase followed by a breathing-out phase. The breathing-in phase includes: i) in response to a speed of a rotor of the engine being at a sub-idle threshold, opening variable guide vanes upstream a compressor and injecting fuel into the combustor to increase rotor speed to a pre-determined upper threshold, and then ii) in response to the rotor speed reaching the pre-determined upper threshold, reducing a supply rate of fuel into the combustor and substantially closing the variable guide vanes. The breathing-out phase includes maintaining the variable guide vanes closed at least until the speed drops from the pre-determined upper threshold to the pre-determined sub-idle threshold.

A method of operating an engine of a multi-engine aircraft includes sequentially operating the engine through a plurality of cycles, each cycle including a breathing-in phase followed by a breathing-out phase. The breathing-in phase includes: i) in response to a speed of a rotor of the engine being at a sub-idle threshold, opening variable guide vanes upstream a compressor and injecting fuel into the combustor to increase rotor speed to a pre-determined upper threshold, and then ii) in response to the rotor speed reaching the pre-determined upper threshold, reducing a supply rate of fuel into the combustor and substantially closing the variable guide vanes. The breathing-out phase includes maintaining the variable guide vanes closed at least until the speed drops from the pre-determined upper threshold to the pre-determined sub-idle threshold.

An exemplary aircraft includes a turbine engine having a gas generator spool and a power spool, the power spool operational to drive a rotor, a first generator coupled to the gas generator spool, and a controller operable to increase a load on the gas generator spool when the gas generator spool is on a speed limit thereby increasing a speed limit margin in order to increase power available from the turbine engine.

An exemplary aircraft includes a turbine engine having a gas generator spool and a power spool, the power spool operational to drive a rotor, a first generator coupled to the gas generator spool, and a controller operable to increase a load on the gas generator spool when the gas generator spool is on a speed limit thereby increasing a speed limit margin in order to increase power available from the turbine engine.

A method for controlling at least a first turboshaft engine and a second turboshaft engine of a rotorcraft, which set a common kinematic linkage in motion, the rotorcraft having an output electric machine cooperating with a first output kinematic linkage of the first turboshaft engine, the rotorcraft having an input electric machine cooperating with a gas generator of the second turboshaft engine. The method includes the following steps: supplying fuel to the first turboshaft engine, operating the output electric machine in electrical energy generator mode, supplying fuel to the second turboshaft engine, and operating the input electric machine in motor mode in order to supply a second non-zero power to said common kinematic linkage.