A system and method for adaptively controlling a cooldown cycle of an auxiliary power unit (APU) that is operating and rotating at a rotational speed includes reducing the rotational speed of the APU to a predetermined cooldown speed magnitude that ensures combustor inlet temperature has reached a predetermined temperature value, determining, based on one or more of operational parameters of the APU, when a lean blowout of the APU is either imminent or has occurred, and when a lean blowout is imminent or has occurred, varying one or more parameters associated with the shutdown/cooldown cycle.

Herein provided are methods and systems for setting an acceleration schedule for engine start of a gas turbine engine. A rotational acceleration measurement of the engine after the engine is energized in response to a start request is obtained. The rotational acceleration measurement of the engine is compared to an acceleration band having a maximum threshold and a minimum threshold. An acceleration schedule is determined based on a position of the rotational acceleration measurement of the engine in the acceleration band.

One aspect is an electrical augmentation system for a gas turbine engine. The electrical augmentation system includes an electric motor operably coupled to a shaft of the gas turbine engine, and an energy storage device operable to provide a temporary increased current source to the electric motor. The electrical augmentation system includes a control system having a torque demand anticipation circuit operable to determine an anticipated torque increase condition for the gas turbine engine. Based on the anticipated torque increase condition, the torque demand anticipation circuit commands a temporary torque increase by the electric motor using the energy storage device.

Systems and methods for controlling a gas turbine engine are provided. The system comprises an interface to a fuel flow metering valve for controlling a fuel flow to the engine in response to a fuel flow command and a controller connected to the interface and configured for outputting the fuel flow command to the fuel flow metering valve in accordance with a required fuel flow. The controller comprises a feedforward controller configured for receiving a requested engine speed and acceleration, obtaining a steady-state fuel flow for the requested engine speed and a relationship between fuel flow and gas generator speed, and determining the required fuel flow to obtain the requested engine acceleration as a function of the requested engine speed, the steady-state fuel flow, and the relationship between fuel flow and gas generator speed.

A turbomachine train with two shaft parts which each have a fixedly attached grooved wheel, with a first overrunning clutch, with two rotational speed sensors and with a control device. The clutch is designed to couple and decouple the first shaft part to and from the second shaft part. The first rotational speed sensor measures the rotational speed of the first grooved wheel. The second rotational speed sensor measures the rotational speed of the second grooved wheel. The control device determines the differential angle between the first shaft part and the second shaft part and accelerates the turbomachines, with an acceleration value determined on the basis of the measured rotational speeds and on the basis of the differential angle, such that the two shaft parts couple together at a predetermined target coupling angle.

In accordance with one aspect of the present technique a method includes receiving at least one of a speed and an acceleration of a rotating component in a rotating machine. The method includes determining whether at least one of the speed and the acceleration of the rotating component exceeds a non-trip operating (NTO) space in a speed-acceleration plane, wherein the NTO space is based on a trip overshoot model. The method further includes sending a notification for tripping the rotating machine in response to determining that at least one of the speed and the acceleration of the rotating component exceeds the NTO space.

Systems and methods for controlling a gas turbine engine are provided. The system comprises an interface to a fuel flow metering valve for controlling a fuel flow to the engine in response to a fuel flow command and a controller connected to the interface and configured for outputting the fuel flow command to the fuel flow metering valve in accordance with a required fuel flow. The controller comprises a feedforward controller configured for receiving a requested engine speed, obtaining a steady-state fuel flow for the requested engine speed as a function of the requested engine speed, the steady-state fuel flow, and the relationship between fuel flow and gas generator speed, and determining the required fuel flow to obtain the requested engine speed and the relationship between fuel flow and gas generator speed.

A method for controlling a gas turbine when the gas turbine is started may include measuring the number of rotations of the gas turbine, determining a target acceleration rate based on the number of rotations of the gas turbine, measuring a current acceleration rate, determining a flow rate of fuel based on a difference between the current acceleration rate and the target acceleration rate, and supplying fuel to the gas turbine at the determined flow rate. The flow rate of the fuel may be determined between a maximum flow rate of the fuel that has been previously stored and a minimum flow rate of the fuel. A temperature of the exhaust gas after controlling the flow rate of the fuel may be monitored.

A hybrid-electric propulsion system includes a propulsor, a turbomachine, and an electrical system, the electrical system including an electric machine coupled to the turbomachine. A method for operating the propulsion system includes operating, by one or more computing devices, the turbomachine such that the turbomachine rotates the propulsor; receiving, by the one or more computing devices, a command to accelerate the turbomachine while operating the turbomachine; and providing, by the one or more computing devices, electrical power to the electric machine to add power to the turbomachine, the propulsor, or both in response to the received command to accelerate the turbomachine.

Herein provided are methods and systems for setting an acceleration schedule for engine start of a gas turbine engine. A rotational acceleration measurement of the engine after the engine is energized in response to a start request is obtained. The rotational acceleration measurement of the engine is compared to an acceleration band having a maximum threshold and a minimum threshold. An acceleration schedule is determined based on a position of the rotational acceleration measurement of the engine in the acceleration band.