A method for operating a hybrid-electric propulsion system of an aircraft, the hybrid-electric propulsion system comprising a gas turbine engine having a compressor and an electric machine coupled to the compressor, the method comprising: sensing data indicative of a pressure within the compressor of the gas turbine engine; determining conditions within the compressor are within a threshold of a stall limit for the compressor based at least in part on the sensed data indicative of the pressure within the compressor of the gas turbine engine; and modifying a torque of the compressor using the electric machine in response to determining the conditions within the compressor are within the threshold of the stall limit for the compressor to reduce a risk of compressor stall.

A method for compensating torsional loads applied to a shaft coupled to a main engine, comprising measuring values indicative of torsional loads applied on the shaft or power demand from the main engine; computing from the values the torsional load over time and a parameter indicative of a cycle; after measuring the group of values, measuring a subsequent value indicative of torsional loads applied on the shaft, and applying a compensating moment or load in a direction determined by whether the subsequent value is greater than or smaller than the value representing the torsional load over time. The direction is a torque direction applied to the shaft by the main engine or the opposite direction.

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.

Processes for controlling at least one process condition of a chemical processing unit with a turbine. In the processes, a flow of a fluid is adjusted with a turbine in order to provide the fluid with a flow associated with at least one process condition of a chemical processing unit. The turbine wheel is rotated within the turbine, and the turbine wheel is configured to transmit rotational movement to an electrical generator. The resistance of the turbine is modulated and adjusts the flow of the fluid through the turbine. A response time of at least one steady state process condition to a new steady state process condition of at least 10% difference is at least one second to reach 50% of the difference between the at least one steady state process condition and the new steady state process condition after modulating the resistance of the turbine.

Herein provided are methods and systems for controlling an engine having a variable geometry mechanism. A pressure ratio between a first pressure at an inlet of the engine and a predetermined reference pressure is determined. An output power for the engine is determined. The output power is adjusted based at least in part on the pressure ratio to obtain a corrected output power. A position control signal for a variable geometry mechanism of the engine is generated based on the corrected output power and the pressure ratio. The position control signal is output to a controller of the engine to control the variable geometry mechanism.

Methods and systems for operating a gas turbine engine are described. The method comprises obtaining, at a control system associated with the gas turbine engine, a measured engine core speed and an actual power demand for the gas turbine engine during operation thereof, determining an expected engine core speed based on the actual power demand from a predicted relationship between engine core speed and engine output power, comparing the measured engine core speed to the expected engine core speed, detecting a torque-related fault when the measured engine core speed differs from the expected engine core speed by more than a threshold; and accommodating the torque-related fault when detected.

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.

Hybrid electric systems and methods therefore are provided. In one exemplary aspect, a hybrid electric system includes an engine, an electric machine operatively coupled thereto and configured to generate electrical power when driven by the engine. One or more electrical loads are electrically connectable with the electric machine. An engine controller of the engine receives load state data indicative of electrical loads that anticipate electrically disconnecting from or electrically connecting to the electric machine at a predetermined time. In this way, the engine controller can anticipate electrical load changes and the engine can be controlled to adjust its torque output in anticipation of the electrical load change. In another exemplary aspect, a hybrid electric system is provided that includes features for nearly instantaneously reacting to load changes on the engine based on load state data received from feed forward inputs of the electrical system of the hybrid electric system.

Herein provided are methods and systems for controlling an engine having a variable geometry mechanism. A pressure ratio between a first pressure at an inlet of the engine and a predetermined reference pressure is determined. An output power for the engine is determined. The output power is adjusted based at least in part on the pressure ratio to obtain a corrected output power. A position control signal for a variable geometry mechanism of the engine is generated based on the corrected output power and the pressure ratio. The position control signal is output to a controller of the engine to control the variable geometry mechanism.

A power turbine control system for a gas turbine engine may comprise a controller comprising one or more processors in communication with the gas turbine engine. The processors may comprise an engine control module configured to receive a torque request signal and generate a torque achieved signal. A rate of change of power turbine speed estimation module may generate an estimated rate of change of power turbine speed signal. A dynamic inversion power turbine governor module may generate the torque request signal based on the torque achieved signal and estimated rate of change of power turbine speed signal.