An example method includes obtaining a representation of a change in rotational speed of an electric machine; obtaining a representation of an expected change in rotational speed of the electric machine; and determining, based on the obtained representation of the change in rotational speed of the electric machine and the representation of an expected change in rotational speed of the electric machine, whether a disconnect device has failed, wherein, when operating in an engaged state, the disconnect device is configured to couple rotational mechanical energy between the electric machine and a rotating device, and wherein, when operating in a disengaged state, the disconnect device is not configured to couple rotational mechanical energy between the electric machine and the rotating device.

Provided is a gas turbine system in which electricity consumption of a battery when starting or stopping a gas turbine engine is reduced and sufficient battery power during flight can be secured. The present invention includes a plurality of gas turbine engines 21, 22, and 23, generators 41, 42, and 43, a battery 5, and a controller 7. The controller 7 decides at least one main starting gas turbine engine 21 from the plurality of gas turbine engines before the plurality of gas turbine engines are started, starts the main starting gas turbine engine 21 using electricity from the battery 5, and starts the secondary starting gas turbine engines 22 and 23 of the plurality of gas turbine engines other than the main starting gas turbine engine 21 using electricity from the generator 41 connected to the main starting gas turbine engine 21 after the main starting gas turbine engine 21 reaches a steady state.

Provided is a gas turbine system in which electricity consumption of a battery when starting or stopping a gas turbine engine is reduced and sufficient battery power during flight can be secured. The present invention includes a plurality of gas turbine engines 21, 22, and 23, generators 41, 42, and 43, a battery 5, and a controller 7. The controller 7 decides at least one main starting gas turbine engine 21 from the plurality of gas turbine engines before the plurality of gas turbine engines are started, starts the main starting gas turbine engine 21 using electricity from the battery 5, and starts the secondary starting gas turbine engines 22 and 23 of the plurality of gas turbine engines other than the main starting gas turbine engine 21 using electricity from the generator 41 connected to the main starting gas turbine engine 21 after the main starting gas turbine engine 21 reaches a steady state.

Electrical power generation system for an aircraft, including: a gas turbine having a high-pressure shaft and outputting a gas flow to actuate a free turbine, a polyphase permanent magnet generator coupled to the gas turbine and able to output a first alternating voltage for supplying through first conversion means a primary power supply network of the aircraft, the free turbine and the permanent magnet generator being mounted on the same drive shaft concentric with the high-pressure shaft of the gas turbine, a starter mounted on the high-pressure shaft able to ensure the starting of the gas turbine, the starter being a permanent magnet starter/generator able to output a second alternating voltage for supplying a secondary power supply network of the aircraft and auxiliary equipment of the gas turbine and the first conversion means include two first AC/DC converters controlled from a management unit.

Electrical power generation system for an aircraft, including: a gas turbine having a high-pressure shaft and outputting a gas flow to actuate a free turbine, a polyphase permanent magnet generator coupled to the gas turbine and able to output a first alternating voltage for supplying through first conversion means a primary power supply network of the aircraft, the free turbine and the permanent magnet generator being mounted on the same drive shaft concentric with the high-pressure shaft of the gas turbine, a starter mounted on the high-pressure shaft able to ensure the starting of the gas turbine, the starter being a permanent magnet starter/generator able to output a second alternating voltage for supplying a secondary power supply network of the aircraft and auxiliary equipment of the gas turbine and the first conversion means include two first AC/DC converters controlled from a management unit.

Systems and methods to pump fracturing fluid into a wellhead may include a gas turbine engine including a compressor turbine shaft connected to a compressor, and a power turbine output shaft connected to a power turbine. The compressor turbine shaft and the power turbine output shaft may be rotatable at different rotational speeds. The systems may also include a transmission including a transmission input shaft connected to the power turbine output shaft and a transmission output shaft connected to a hydraulic fracturing pump. The systems may also include a fracturing unit controller configured to control one or more of the rotational speeds of the compressor turbine shaft, the power turbine output shaft, or the transmission output shaft based at least in part on target signals and fluid flow signals indicative of one or more of pressure or flow rate associated with fracturing fluid pumped into the wellhead.

Systems and methods to pump fracturing fluid into a wellhead may include a gas turbine engine including a compressor turbine shaft connected to a compressor, and a power turbine output shaft connected to a power turbine. The compressor turbine shaft and the power turbine output shaft may be rotatable at different rotational speeds. The systems may also include a transmission including a transmission input shaft connected to the power turbine output shaft and a transmission output shaft connected to a hydraulic fracturing pump. The systems may also include a fracturing unit controller configured to control one or more of the rotational speeds of the compressor turbine shaft, the power turbine output shaft, or the transmission output shaft based at least in part on target signals and fluid flow signals indicative of one or more of pressure or flow rate associated with fracturing fluid pumped into the wellhead.

A gas turbine engine for an aircraft and a method of operating a gas turbine engine on an aircraft. Embodiments disclosed include a gas turbine engine for an aircraft including: an engine core has a turbine, a compressor, and a core shaft; a fan located upstream of the engine core, the fan has a plurality of fan blades; a nacelle surrounding the engine core and defining a bypass duct and bypass exhaust nozzle; and a gearbox that receives an input from the core shaft and outputs drive to the fan wherein the gas turbine engine is configured such that a jet velocity ratio of a first jet velocity exiting from the bypass exhaust nozzle to a second jet velocity exiting from an exhaust nozzle of the engine core at idle conditions is greater by a factor of 2 or more than the jet velocity ratio at maximum take-off conditions.

Systems and techniques for engine starter control may include determining a current speed band associated with an engine start for a current time increment, determining a previous speed band associated with the engine start for a previous time increment within the engine start, receiving a measured current value, determining a target current value based on the current speed band, the previous speed band, whether an acceleration or deceleration occurred between the current speed band and the previous speed band, and a mode of a system for engine starter control, and adjusting a current for the engine start based on the target current value.

Systems and methods to pump fracturing fluid into a wellhead may include a gas turbine engine including a compressor turbine shaft connected to a compressor, and a power turbine output shaft connected to a power turbine. The compressor turbine shaft and the power turbine output shaft may be rotatable at different rotational speeds. The systems may also include a transmission including a transmission input shaft connected to the power turbine output shaft and a transmission output shaft connected to a hydraulic fracturing pump. The systems may also include a fracturing unit controller configured to control one or more of the rotational speeds of the compressor turbine shaft, the power turbine output shaft, or the transmission output shaft based at least in part on target signals and fluid flow signals indicative of one or more of pressure or flow rate associated with fracturing fluid pumped into the wellhead.