Abstract: A gas turbine engine includes a combustor having a combustor air inlet, an axial-centrifugal compressor, a shroud, a secondary flow duct, and a valve. The shroud surrounds at least a portion of the axial-centrifugal compressor and has a surge bleed plenum defined therein that is in fluid communication with, and receives compressed air from, the axial compressor outlet. The secondary airflow duct has a duct inlet that is in fluid communication with the surge bleed plenum, and a duct outlet that is in fluid communication with the combustor air inlet. The valve is mounted on the secondary airflow duct and is movable between a closed position, in which the secondary airflow duct does not provide fluid communication between the surge bleed plenum and the combustor air inlet, and an open position, in which the secondary airflow duct provides fluid communication between the surge bleed plenum and the combustor air inlet.

Abstract: A gas turbine engine includes a combustor having a combustor air inlet, an axial-centrifugal compressor, a shroud, a secondary flow duct, and a valve. The shroud surrounds at least a portion of the axial-centrifugal compressor and has a surge bleed plenum defined therein that is in fluid communication with, and receives compressed air from, the axial compressor outlet. The secondary airflow duct has a duct inlet that is in fluid communication with the surge bleed plenum, and a duct outlet that is in fluid communication with the combustor air inlet. The valve is mounted on the secondary airflow duct and is movable between a closed position, in which the secondary airflow duct does not provide fluid communication between the surge bleed plenum and the combustor air inlet, and an open position, in which the secondary airflow duct provides fluid communication between the surge bleed plenum and the combustor air inlet.

Abstract: An engine system for starting a gas turbine engine includes a starter coupled to the gas turbine engine and configured to provide torque to the gas turbine engine; and a controller coupled to the starter and configured to evaluate an engine system parameter and to select from a plurality of start modes for starting the gas turbine engine based on the engine system parameter.

Abstract: An engine system for starting a gas turbine engine includes a starter coupled to the gas turbine engine and configured to provide torque to the gas turbine engine; and a controller coupled to the starter and configured to evaluate an engine system parameter and to select from a plurality of start modes for starting the gas turbine engine based on the engine system parameter.

Abstract: A method of supplying mechanical power to an operating gas turbine engine includes supplying mechanical power from the operating gas turbine engine to a starter-generator, to thereby generate electrical power using the starter-generator. One or more operational parameters of the operating gas turbine engine are sensed and, based on the one or more sensed operational parameters, electrical power is selectively supplied to the starter-generator to thereby generate and supply mechanical output power to the operating gas turbine engine.