A hybrid electric propulsion system includes a gas turbine engine having a low speed spool and a high speed spool. The low speed spool includes a low pressure compressor and a low pressure turbine, and the high speed spool includes a high pressure compressor and a high pressure turbine. The hybrid electric propulsion system also includes an energy storage system, an electric motor configured to augment rotational power of the high speed spool, and a controller. The controller is operable to detect a start condition of the gas turbine engine, control power delivery from the energy storage system to the electric motor based on detecting the start condition, and provide a compressor stall margin using a power-assist provided by the electric motor to the high speed spool over a targeted speed range during starting of the gas turbine engine.

A gas turbine engine includes a low speed spool mechanically interconnecting a low pressure turbine and at least one of a fan and a prop, a high speed spool mechanically interconnecting a high pressure turbine and a high pressure compressor, and an epicyclic gear system mechanically coupled to the high speed spool. The gas turbine engine also includes a low pressure compressor mechanically coupled to the high speed spool via the epicyclic gear system. The low pressure compressor may be mechanically independent of the low speed spool. The gas turbine engine may include a plurality of motor-generators for transferring power between the high speed spool and the low pressure compressor.

A turbine engine includes integrated electric machines in the compressor section and the turbine section to supplement power produced from fuel with electric power. The example compressor section includes a compressor electric motor that is coupled to a compressor generator. The example turbine section includes a turbine electric motor that is coupled to the geared architecture to supplement power driving the fan section. A turbine generator provides electric power to the turbine electric motor.

A gas turbine engine has a compression system blade ratio defined as the ratio of the height of a fan blade to the height of the most downstream compressor blade in the range of from 45 to 95. This results in an optimum balance between installation benefits, operability, maintenance requirements and engine efficiency when the gas turbine engine is installed on an aircraft.

A gas turbine engine has a compression system blade ratio defined as the ratio of the height of a fan blade to the height of the most downstream compressor blade in the range of from 45 to 95. This results in an optimum balance between installation benefits, operability, maintenance requirements and engine efficiency when the gas turbine engine is installed on an aircraft.

A gas turbine engine includes a first spool rotationally coupled to a plurality of accessories via a first gearing and a second spool rotationally coupled to a third spool via a second gearing. The first gearing and the second gearing rotate independently and are enclosed within a housing of an accessory gearbox. A method of operating the gas turbine engine includes supplying a first fuel flow rate to a primary combustor associated with the first and third spools and supply a second fuel flow rate a secondary combustor associated with the second spool based on a power lever angle within an intermediate power level range.

A hybrid electric engine of an aircraft includes a compressor, a turbine operably connected to the compressor via a variable gear ratio gearbox and a combustor configured to drive the turbine via a flow of combustion products. An electric motor is operably connected to the variable gear ratio rear box and configured to input rotational energy into the gearbox. The input of rotational energy into the gearbox from the electric motor changes a rotational speed of one of the compressor or the turbine relative to the other of the compressor or the turbine.

Electrical systems for connecting rotary electric machines with gas turbine spools are provided. One such electrical system comprises: a first rotary electric machine mechanically coupled with a first gas turbine spool and a second rotary electric machine mechanically coupled with a second gas turbine spool, each said electric machine having an identical even number N≥4 of phases, each phase having a respective index n=(1, . . . , N), and each phase comprising an identical number P≥1 of coils wound in a P-plex configuration in which adjacent phases are radially separated by 2π/NP mechanical radians; a first set of N bidirectional converter circuits for conversion of alternating current (ac) to and from direct current (dc), each converter circuit having a respective index n and being connected with the P coils in the nth phase of the first rotary electric machine; and a second set of N bidirectional converter circuits for conversion of ac to and from dc, each converter circuit having a respective index n and being connected with the P coils in the nth phase of the second rotary electric machine. For all n, a dc side of the nth converter circuit in said first set is connected with a dc side of the nth converter circuit in said second set to facilitate dc power transfer between the first gas turbine spool and the second gas turbine spool.

Electrical systems for connecting rotary electric machines with gas turbine spools are provided. One such electrical system comprises: a first rotary electric machine mechanically coupled with a first gas turbine spool and a second rotary electric machine mechanically coupled with a second gas turbine spool, each said electric machine having an identical even number N≥4 of phases, each phase having a respective index n=(1, . . . , N), and each phase comprising an identical number P≥1 of coils wound in a P-plex configuration in which adjacent phases are radially separated by 2π/NP mechanical radians; a first set of N bidirectional converter circuits for conversion of alternating current (ac) to and from direct current (dc), each converter circuit having a respective index n and being connected with the P coils in the nth phase of the first rotary electric machine; and a second set of N bidirectional converter circuits for conversion of ac to and from dc, each converter circuit having a respective index n and being connected with the P coils in the nth phase of the second rotary electric machine. For all n, a dc side of the nth converter circuit in said first set is connected with a dc side of the nth converter circuit in said second set to facilitate dc power transfer between the first gas turbine spool and the second gas turbine spool.

A gas turbine engine is provided. The gas turbine engine includes a turbomachine having a low speed spool and a high speed spool; a rotor assembly coupled to the low speed spool; an electric machine rotatable with the low speed spool for extracting power from the low speed spool, for adding power to the low speed spool, or both; and an inter-spool clutch positioned between the low speed spool and the high speed spool for selectively coupling the low speed spool to the high speed spool.