Abstract: An engine system includes a gas turbine engine with a first compressor, a first combustor, and first turbine. The engine system also includes a secondary power unit with a second compressor, a second combustor, a second turbine, a third compressor coupled to the second compressor, and an electric motor-generator, where the secondary power unit is coupled to the gas turbine engine and includes a heat exchanger. A controller is operable to determine an operating mode of the engine system, select an input energy source and an output type of the secondary power unit based on the operating mode, control the secondary power unit based on the input energy source and the output type as selected, detect a change in the operating mode of the engine system, and modify the input energy source and/or the output type of the secondary power unit based on the change in the operating mode.

Abstract: An engine system includes a gas turbine engine with a first compressor, a first combustor, and a first turbine. The engine system also includes a secondary power unit with a second compressor, a second combustor, a second turbine, a third compressor coupled to the second compressor, and an electric motor-generator, where the secondary power unit is coupled to the gas turbine engine. A controller is operable to determine an operating mode of the engine system, select an input energy source and an output type of the secondary power unit based on the operating mode, control the secondary power unit based on the input energy source and the output type as selected, detect a change in the operating mode of the engine system, and modify the input energy source and/or the output type of the secondary power unit based on the change in the operating mode.

Abstract: An engine system is provided that includes a compressor section, a combustor section, a turbine section, a flowpath and a flow regulator. The combustor section includes a combustion chamber. The flowpath extends sequentially through the compressor section, the combustor section and the turbine section. The flow regulator is configured to open the flowpath between the compressor section and the combustion chamber during a first mode of operation. The flow regulator is configured to at least substantially close the flowpath between the compressor section and the combustion chamber during a second mode of operation.

Abstract: A starter assembly for a gas turbine engine according to an example of the present disclosure includes, among other things, a fluid-actuated starter coupled to a spool, and a controller operable to cause a reduction in torque output of the starter in response to determining that a first threshold is met. The first threshold relates to an engine operational condition. A method for starting a gas turbine engine is also disclosed.

Abstract: A gas turbine engine includes a compressor section, a combustor fluidly connected to the compressor section via a primary flowpath, a turbine section fluidly connected to the combustor via the primary flowpath, and a plurality of fuel injectors disposed within the combustor. The plurality of fuel injectors including at least one start fuel injector. Also included is a controller having a memory and processor. The memory stores instructions configured to cause the at least one start fuel injector to pulse fuel through the start injector nozzle, thereby preventing stagnant fuel in the start injector nozzle from exceed a coking temperature threshold.

Abstract: A starter assembly for a gas turbine engine according to an example of the present disclosure includes, among other things, a fluid-actuated starter coupled to a spool, and a controller operable to cause a reduction in torque output of the starter in response to determining that a first threshold is met. The first threshold relates to an engine operational condition. A method for starting a gas turbine engine is also disclosed.

Abstract: A starter assembly for a gas turbine engine according to an example of the present disclosure includes, among other things, a fluid-actuated starter coupled to a spool, and a controller operable to cause a reduction in torque output of the starter in response to determining that a first predefined threshold is met. The first predefined threshold relates to an engine operational condition. A method for starting a gas turbine engine is also disclosed.

Abstract: An engine system includes a gas turbine engine with a first compressor, a first combustor, and a first turbine. The engine system also includes a secondary power unit with a second compressor, a second combustor, a second turbine, a third compressor coupled to the second compressor, and an electric motor-generator, where the secondary power unit is coupled to the gas turbine engine. A controller is operable to determine an operating mode of the engine system, select an input energy source and an output type of the secondary power unit based on the operating mode, control the secondary power unit based on the input energy source and the output type as selected, detect a change in the operating mode of the engine system, and modify the input energy source and/or the output type of the secondary power unit based on the change in the operating mode.

Abstract: A fuel assembly for a gas turbine engine according to an example of the present disclosure includes, among other things, a fuel valve that meters flow of fluid between a combustor and a fuel supply, and a controller in communication with the fuel assembly. The controller is programmed to receive data corresponding to a present rotational speed of a gas turbine engine component and data corresponding to at least one present flight condition, and is programmed to cause a flow rate from the fuel valve to change in response to determining that a rate of change in an acceleration rate relating to the present rotational speed meets at least one predetermined threshold. At least one predetermined threshold relates to an engine light-off event of the combustor and is based upon the at least one present flight condition.

Abstract: A gas turbine engine includes a compressor section, a combustor fluidly connected to the compressor section via a primary flowpath, a turbine section fluidly connected to the combustor via the primary flowpath, and a plurality of fuel injectors disposed within the combusto. The plurality of fuel injectors including at least one start fuel injector. Also included is a controller having a memory and processor. The memory stores instructions configured to cause the at least one start fuel injector to pulse fuel through the start injector nozzle, thereby preventing stagnant fuel in the start injector nozzle from exceed a coking temperature threshold.

Abstract: A starter assembly for a gas turbine engine according to an example of the present disclosure includes, among other things, a fluid-actuated starter coupled to a spool, and a controller operable to cause a reduction in torque output of the starter in response to determining that a first predefined threshold is met. The first predefined threshold relates to an engine operational condition. A method for starting a gas turbine engine is also disclosed.

Abstract: A fuel assembly for a gas turbine engine according to an example of the present disclosure includes, among other things, a fuel valve that meters flow of fluid between a combustor and a fuel supply, and a controller in communication with the fuel assembly. The controller is programmed to receive data corresponding to a present rotational speed of a gas turbine engine component and data corresponding to at least one present flight condition, and is programmed to cause a flow rate from the fuel valve to change in response to determining that a rate of change in an acceleration rate relating to the present rotational speed meets at least one predetermined threshold. At least one predetermined threshold relates to an engine light-off event of the combustor and is based upon the at least one present flight condition.

Abstract: A method for controlling fuel flow to a gas turbine engine during starting includes monitoring acceleration of the gas turbine engine to determine actual acceleration value, and calculating a fuel flow rate for a setpoint acceleration using the actual acceleration value as a factor. The method further includes commanding the calculated fuel flow for the setpoint acceleration to the gas turbine engine.

Abstract: An example method of fuel delivery to a turbomachine includes reaching a light-off speed of a turbomachine and delivering fuel to a combustor of the turbomachine at a first rate. The method also increases the rate of the delivery. The combustor achieves light-off at a fuel flow rate on or in-between the first rate and a second rate that is greater than the first rate. An example turbomachine fuel delivery assembly includes a fuel delivery component and a controller configured to adjust the fuel pump to increase a rate of fuel delivery from a fuel supply to a combustor of a turbomachine.

Abstract: A method includes receiving an indication of exhaust gas temperature (EGT) for a gas turbine engine, and determining, by at least one processor, based on the received indication of the EGT, a representation of a second derivative with respect to time of the EGT. The method further includes comparing the representation of the second derivative of the EGT to a threshold value, and determining, based on the comparing, an engine flameout condition of the gas turbine engine. In some embodiments, the at least one processor can determine a representation of a first derivative with respect to time of the EGT. The representation of the first derivative of the EGT can be compared to a threshold value, determined based on the received indication of the EGT, to determine the engine flameout condition.

Abstract: A gas turbine engine inlet door control system includes an actuator, an engine controller and a door controller. The actuator opens and closes an inlet door of a gas turbine engine. The engine controller determines an intermediate door position based upon one or more engine start factors. The door controller operates the actuator to open the inlet door to the intermediate door position based on the one or more engine start factors.

Abstract: A method of starting a gas turbine engine includes maintaining the gas turbine engine at the dwelling speed after light-off until a predetermined magnitude of combustor warm-up is determined then increasing the speed of the starter motor to accelerate the gas turbine engine after the predetermined magnitude of combustor warm-up is achieved.

Abstract: A method for controlling a flow of fuel to a starting gas turbine engine includes controlling the flow of fuel to the engine by controlling fuel pressure to the engine, and modulating the flow of fuel to the engine if engine exhaust gas temperature approaches a given exhaust gas temperature to lower the engine exhaust gas temperature below the given exhaust gas temperature.

Abstract: A method for controlling fuel flow to a gas turbine engine during starting includes monitoring acceleration of the gas turbine engine to determine actual acceleration value, and calculating a fuel flow rate for a setpoint acceleration using the actual acceleration value as a factor. The method further includes commanding the calculated fuel flow for the setpoint acceleration to the gas turbine engine.

Abstract: A method of indicating low oil level of lubrication oil for a gas turbine engine automatically eliminates false low oil readings due to temperature-induced lubrication oil shrinkage and operation-induced changes in lubrication oil level.