Techniques are described for using an electrical motor to slow down or stop a propulsor during an operation mode where the engine is to be otherwise running but the speed of the propulsor should be low or the propulsor should be stopped.

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.

An enhanced engine starter system controls an air turbine starter at the startup of operation of a turbine engine. The engine starter system includes an air turbine starter (ATS) that operates in accordance with more than one speed/torque curve during the startup procedure. A controller commands the starter control valve to provide a regulated pressure to the ATS in accordance with a first speed/torque curve to initiate the gas turbine engine startup without exceeding a maximum or design limiting torque. Overall duration of the startup procedure is reduced by the controller subsequently operating the ATS in accordance with a second speed/torque curve having a higher operational pressure once the ATS reaches a predetermined transition speed. The torque at the predetermined transition speed on the higher pressure second curve remains less than the design limiting torque, but provides a higher torque as compared to the first speed/torque curve to reduce the duration of the startup procedure.

A turbomachine for a vehicle is provided. The turbomachine includes a first rotatable component; a first power source operatively coupled with the first rotatable component; a second power source selectively coupled with the first rotatable component; and a controller having one or more processors and one or more memory devices, the one or more memory devices storing instructions that when executed by the one or more processors cause the one or more processors to perform operations, in performing the operations, the one or more processors are configured to: receive an input indicating an engine shutdown of the turbomachine; and in response to the engine shutdown, cause the second power source to provide power to and rotate the first rotatable component.

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.

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 a turbomachine comprising an electric motor forming a torque injection device on a high-pressure rotation shaft, in which method a fuel flow setpoint Q.sub.CMD and a torque setpoint TRQ.sub.CMD provided at the electric motor are determined, the control method comprising: •a step of implementing a first fuel control loop in order to determine the fuel flow set point QCMD, •a step of implementing a second, torque control loop in order to determine the torque setpoint TRQ.sub.CMD comprising i. a step of determining a torque correction variable ΔTRQ.sub.CMD as a function of a transitory speed setpoint NHTrajAccelCons, NHTrajDecelCons and ii. a step of determining the torque setpoint TRQ.sub.CMD as a function of the torque correction variable ΔTRQ.sub.CMD.

The present disclosure provides methods and systems for operating a multi-engine rotorcraft. The method comprises driving a rotor of the rotorcraft with a first engine while a second engine is de-clutched from a transmission clutch system that couples the rotor and the second engine, instructing the second engine to accelerate to a re-clutching speed, and controlling an output shaft speed of the second engine during acceleration of the second engine to the re-clutching speed by applying a damping function to a speed control loop of the second engine.

The present disclosure is directed to a system for controlling an output of a gas generator via an operator manipulated input device. The system includes one or more sensors measuring one or more environmental conditions, a gas generator shaft speed, and a power turbine torque. The system further includes an operator manipulated input device and one or more controllers including one or more processors and one or more memory devices. The one or more memory devices stores instructions that when executed by the one or more processors cause the one or more processors to perform operations. The operations include receiving, via an operator manipulated input device, a throttle lever position defining at least an idle position, a takeoff position, and one or more intermediate positions therebetween; receiving, via one or more sensors, one or more environmental conditions, wherein the environmental condition includes one or more of an ambient air temperature, an ambient air pressure, and an ambient airflow rate; determining, via the controller, a first commanded fuel flow of the gas generator based on a gas generator speed output curve based at least on the throttle lever position, the one or more environmental conditions, and a coefficient reference table; determining, via the controller, a second commanded fuel flow of the gas generator based on a power turbine torque output curve based at least on the one or more environmental conditions; and generating, via the gas generator, a gas generator output based on the first commanded fuel flow or the second commanded fuel flow.