An engine assembly for use as an aircraft auxiliary power unit, having internal combustion engine(s) in driving engagement with an engine shaft, a generator having a generator shaft directly engaged to the engine shaft such as to be rotatable at a same speed, a compressor having an outlet in communication with the internal combustion engine inlet, and a turbine having an inlet in communication with the internal combustion engine outlet. The turbine may be a first stage turbine, and the assembly may include a second stage turbine having an inlet in communication with the first stage turbine outlet. A method of providing electrical power to an aircraft is also discussed.

The gas turbine power generation system includes a core engine and a low pressure compressor. The core engine includes a high pressure compressor, a combustor, and a high pressure turbine configured in a serial flow arrangement. The high pressure compressor and the high pressure turbine are coupled together by a first shaft. The low pressure compressor is positioned axially forward of the core engine and is coupled to the first shaft.

A hybrid gas-electric turbine engine for turboprop or turboshaft applications is disclosed together with associated methods. In various embodiments disclosed herein, the turbine engine comprises a turbine configured to be driven by a flow of combustion gas; a turbine shaft configured to be driven by the turbine and transfer power to a load coupled to the turbine engine and an electric motor configured to transfer power to the load coupled to the turbine engine. The rotor may have a rotor axis of rotation that is radially offset from a shaft axis of rotation of the turbine shaft. In some embodiments, the electric motor may be a multi-rotor electric motor.

A hybrid gas-electric turbine engine for turboprop or turboshaft applications is disclosed together with associated methods. In various embodiments disclosed herein, the turbine engine comprises a turbine configured to be driven by a flow of combustion gas; a turbine shaft configured to be driven by the turbine and transfer power to a load coupled to the turbine engine and an electric motor configured to transfer power to the load coupled to the turbine engine. The rotor may have a rotor axis of rotation that is radially offset from a shaft axis of rotation of the turbine shaft. In some embodiments, the electric motor may be a multi-rotor electric motor.

Bleed air systems for use with aircraft and related methods are disclosed. An example apparatus includes a compressor having a compressor inlet, a compressor outlet, and a first drive shaft. The compressor outlet is to be fluidly coupled to a system of an aircraft that receives pressurized air, and the compressor inlet is to receive bleed air from a low-pressure compressor of an engine of the aircraft. The example apparatus includes a gearbox operatively coupled to the first drive shaft to drive the compressor. The gearbox is to be operatively coupled to and powered by a second drive shaft extending from the engine. The example apparatus also includes a clutch disposed between the first drive shaft and the gearbox to selectively disconnect the first drive shaft from the gearbox.

Bleed air systems for use with aircraft and related methods are disclosed. An example apparatus includes a compressor having a compressor inlet, a compressor outlet, and a first drive shaft. The compressor outlet is to be fluidly coupled to a system of an aircraft that receives pressurized air, and the compressor inlet is to receive bleed air from a low-pressure compressor of an engine of the aircraft. The example apparatus includes a gearbox operatively coupled to the first drive shaft to drive the compressor. The gearbox is to be operatively coupled to and powered by a second drive shaft extending from the engine. The example apparatus also includes a clutch disposed between the first drive shaft and the gearbox to selectively disconnect the first drive shaft from the gearbox.

A method and system of controlling a turboprop engine are described. The method comprises obtaining a propeller speed and a pressure-based measurement signal from a torque pressure transducer coupled to the turboprop engine, determining an output power of the turboprop engine from the pressure-based measurement and the propeller speed, calculating a gas generator speed request based on an error between the output power and a reference power, determining a fuel flow command based on the gas generator speed request, and issuing the fuel.

A method and system of controlling a turboprop engine are described. The method comprises obtaining a propeller speed and a pressure-based measurement signal from a torque pressure transducer coupled to the turboprop engine, determining an output power of the turboprop engine from the pressure-based measurement and the propeller speed, calculating a gas generator speed request based on an error between the output power and a reference power, determining a fuel flow command based on the gas generator speed request, and issuing the fuel.

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.