An electrical system having a first dual-wound rotary electric machine mechanically coupled with a first gas turbine spool and having a first three-phase sub-machine and a second three-phase submachine; a second dual-wound rotary electric machine mechanically coupled with a second gas turbine spool and having a third three-phase sub-machine and a fourth three-phase submachine; and a set of N = 4 bidirectional converter circuits for conversion of alternating current (ac) to and from direct current (dc), each of which has an associated index n = (1, ... , N), and for all n, the ac side of the nth bidirectional converter circuit is connected with the nth three-phase sub-machine. The dc side of the first converter circuit is connected with the dc side of the third converter circuit, and the dc side of the second converter circuit is connected with the dc side of the fourth converter circuit.

A system includes a gas turbine engine of an aircraft, the gas turbine engine having a low speed spool, a high speed spool, and a combustor. The system also includes a low spool motor configured to augment rotational power of the low speed spool and a high spool motor configured to augment rotational power of the high speed spool. The system further includes a controller configured to cause fuel flow. The controller is configured to control a thrust response of the gas turbine engine to a thrust target between zero and a thrust level to move the aircraft during engine start and during engine idle. The controller is also configured to control the low spool motor to drive rotation of the low speed spool responsive to a thrust command while the controller does not command fuel flow to the combustor.

A system includes a gas turbine engine of an aircraft, the gas turbine engine having a low speed spool, a high speed spool, and a combustor. The system also includes a low spool motor configured to augment rotational power of the low speed spool and a high spool motor configured to augment rotational power of the high speed spool. The system further includes a controller configured to cause fuel flow. The controller is configured to control a thrust response of the gas turbine engine to a thrust target between zero and a thrust level to move the aircraft during engine start and during engine idle. The controller is also configured to control the low spool motor to drive rotation of the low speed spool responsive to a thrust command while the controller does not command fuel flow to the combustor.

A fracturing apparatus and a fracturing system are provided. The fracturing apparatus includes: a plunger pump configured to pressurize a fracturing fluid to form a high-pressure fracturing fluid; a turbine engine coupled to the plunger pump and configured to provide a driving force to the plunger pump; an auxiliary unit including a driving electric motor, the auxiliary unit being configured to provide the fracturing apparatus with at least one selected from the group consisting of start-up assist function, lubrication function, cooling function, and air supply function; and a power supply electrically coupled to the driving electric motor of the auxiliary unit to provide driving power.

A system for bleeding air from a core flow path of a gas turbine engine is disclosed. In various embodiments, the system includes a bleed valve having a bleed valve inlet configured to receive a bleed air from a first access point to the core flow path and a bleed valve outlet; and an air motor having a first air motor inlet configured to receive the bleed air from the bleed valve outlet and a first air motor outlet configured to exhaust the bleed air, the air motor configured to pump the bleed air from the core flow path of the gas turbine engine.

A fuel power transfer system for an engine may include a cryogenic fuel supply, a fuel pump in fluid communication with the cryogenic fuel supply, a multi-position valve in fluid communication with the fuel pump and a combustion chamber of the engine, a fuel turbine operatively coupled to the fuel pump and having a primary discharge port in fluid communication with the combustion chamber, a primary heat exchanger in fluid communication between the multi-position valve and the fuel turbine, and a gearbox operatively coupled to the fuel turbine and the fuel pump and configured to transfer power from the fuel turbine to the engine.

Methods and systems for starting an aircraft gas turbine engine are described. The method comprises, in a first phase of a startup upon receipt of a start request, modifying a first set of engine control parameters to cause light-up; in a second phase of the startup, modifying a second set of engine control parameters to set conditions for light-around; and in a third phase of the startup, modifying a third set of engine control parameters to propagate a flame around a combustor of the gas turbine engine.

Methods and systems for starting an aircraft gas turbine engine are described. The method comprises, in a first phase of a startup upon receipt of a start request, modifying a first set of engine control parameters to cause light-up; in a second phase of the startup, modifying a second set of engine control parameters to set conditions for light-around; and in a third phase of the startup, modifying a third set of engine control parameters to propagate a flame around a combustor of the gas turbine engine.

Electrical systems for connecting rotary electric machines with gas turbine spools are provided. One such electrical system includes: a first rotary electric machine; a second rotary electric machine; a first set of bidirectional converter circuits; a second set of bidirectional converter circuits; and DC outputs for connection with an R-channel network. Each electrical machine is mechanically coupled with a respective gas turbine spool and has an identical even number N≥4 of phases, each phase having a respective index and including 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. Each of the first and second converter circuits converts AC to and from DC, has a respective index n, and is connected with the P coils in the nth phase of the first and second rotary electric machines, respectively.

A method and system for controlling fuel flow to an aircraft engine during start are provided. Following light-off, an actual value of at least one engine operating parameter is obtained. Based on a difference between the actual value and a target value, a first command is generated to cause fuel flow to be provided to the engine's combustor according to a computed fuel flow rate defined by a fuel schedule of the engine. When the computed fuel flow rate is within a fuel flow rate limit, the first command is output. Otherwise, a limiting factor is applied to the computed fuel flow rate to limit a reduction in fuel flow to the combustor and a limited fuel flow rate is obtained, and a second command is output to cause fuel flow to be provided to the combustor according to the limited fuel flow rate.