Abstract: A bowed rotor prevention system includes a gas turbine engine, an electric motor, and a core turning controller in signal communication with the electric motor. The gas turbine engine includes a rotor that is rotatably coupled to a drive shaft. The electric motor rotatably is coupled to a motor shaft, which is mechanically coupled to the drive shaft so as to rotate therewith. The core turning controller is configured to invoke an anti-rotor bowing mode, and to control the electric motor to periodically rotate the rotor into a plurality of rotor positions during a given time period in response to invoking the anti-rotor bowing mode.

Abstract: A machine comprising a rotor having: an inner member; an outer member encircling the inner member; and a groove in one of the inner member and the outer member. The groove has a first side wall, a second side wall and a base. A split ring seal is accommodated in the groove and contacts a surface of the other of the inner member and the outer member The first side wall has a plurality of open radial first channels and the second side wall has a plurality of open radial second channels.

Abstract: A bowed rotor prevention system includes a gas turbine engine, and electric motor, and a core turning controller. The gas turbine engine includes a rotor that is rotatably coupled to a drive shaft. The electric motor is rotatably coupled to a motor shaft, which is mechanically coupled to the drive shaft so as to rotate therewith. The core turning controller in signal communication with the electric motor. The core turning controller determines whether a rotor bow is present in the rotor based on an operating time of the gas turbine engine, determines a motoring time based on the operating time, and invokes an anti-rotor bowing mode configured to control the electric motor to rotate the rotor according to the motor time.

Abstract: A split ring seal has: a first circumferential end and a second circumferential end; an inner diameter surface and an outer diameter surface; a first axial end face and a second axial end face. A circumferentially distributed first plurality of open channels are along the first axial end face. A circumferentially distributed second plurality of open channels are along the second axial end face.

Abstract: A split ring seal has: a first circumferential end and a second circumferential end; an inner diameter surface and an outer diameter surface; a first axial end face and a second axial end face. A circumferentially distributed first plurality of open channels are along the first axial end face. A circumferentially distributed second plurality of open channels are along the second axial end face.

Abstract: A system for starting a gas turbine engine of an aircraft is provided. The system includes a pneumatic starter motor, a discrete starter valve switchable between an on-state and an off-state, and a controller operable to perform a starting sequence for the gas turbine engine. The starting sequence includes alternating on and off commands to an electromechanical device coupled to the discrete starter valve to achieve a partially open position of the discrete starter valve to control a flow from a starter air supply to the pneumatic starter motor to drive rotation of a starting spool of the gas turbine engine below an engine idle speed, where the controller modulates a duty cycle of the discrete starter valve via pulse width modulation.

Abstract: A system for controlling a start sequence of a gas turbine engine includes an electronic engine control system, a thermal model, memory, a model for determining a time period (tmotoring), and a controller. The thermal model synthesizes a heat state of the gas turbine engine. The memory records the current heat state at shutdown and a shutdown time of the gas turbine engine. The model for determining the time period is for motoring the gas turbine engine at a predetermined speed Ntarget that is less than a speed to start the gas turbine engine, where tmotoring is a function of the heat state recorded at engine shutdown and an elapsed time of an engine start request relative to a previous shutdown time. The controller modulates a starter valve to maintain the gas turbine engine within a predetermined speed range of NtargetMin to NtargetMax for homogenizing engine temperatures.

Abstract: An aspect includes a system including a high compressor of a gas turbine engine having a ratio of a cold-rotor build clearance to a span between 0.7% and 7%. The cold-rotor build clearance is defined for a plurality of rotor blades of the high compressor with respect to an engine casing assembly interior surface of the high compressor, and the span is defined as a gap between a rotor disk of the high compressor and the engine casing assembly interior surface of the high compressor for at least a last two stages of the high compressor closest to a combustor section of the gas turbine engine. The system also includes at least two bowed rotor management systems for the gas turbine engine to prevent damage to the rotor blades for a bowed rotor condition of the high compressor under a plurality of operating conditions.

Abstract: A bowed rotor start mitigation system for a gas turbine engine is provided. The bowed rotor start mitigation system includes a controller operable to receive a vibration input indicative of an actual vibration level of the gas turbine engine and a speed input indicative of a rotor speed of the gas turbine engine. The controller generates a bowed rotor start mitigation request based on comparing the actual vibration level to a modeled vibration level at the rotor speed.

Abstract: A bowed rotor start mitigation system for a gas turbine engine is provided. The bowed rotor start mitigation system includes a controller operable to receive a vibration input indicative of an actual vibration level of the gas turbine engine and a speed input indicative of a rotor speed of the gas turbine engine. The controller generates a bowed rotor start mitigation request based on comparing the actual vibration level to a modeled vibration level at the rotor speed.

Abstract: A system for starting a gas turbine engine of an aircraft is provided. The system includes a pneumatic starter motor, a discrete starter valve switchable between an on-state and an off-state, and a controller operable to perform a starting sequence for the gas turbine engine. The starting sequence includes alternating on and off commands to an electromechanical device coupled to the discrete starter valve to achieve a partially open position of the discrete starter valve to control a flow from a starter air supply to the pneumatic starter motor to drive rotation of a starting spool of the gas turbine engine below an engine idle speed, where the controller modulates a duty cycle of the discrete starter valve via pulse width modulation.

Abstract: A system for controlling a start sequence of a gas turbine engine includes an electronic engine control system, a thermal model, memory, a model for determining a time period (fmotoring), and a controller. The thermal model synthesizes a heat state of the gas turbine engine. The memory records the current heat state at shutdown and a shutdown time of the gas turbine engine. The model for determining the time period is for motoring the gas turbine engine at a predetermined speed Ntarget that is less than a speed to start the gas turbine engine, where tmotoring is a function of the heat state recorded at engine shutdown and an elapsed time of an engine start request relative to a previous shutdown time. The controller modulates a starter valve to maintain the gas turbine engine within a predetermined speed range of NtargetMin to NtargetMax for homogenizing engine temperatures.

Abstract: An aspect includes a system including a high compressor of a gas turbine engine having a ratio of a cold-rotor build clearance to a span between 0.7% and 7%. The cold-rotor build clearance is defined for a plurality of rotor blades of the high compressor with respect to an engine casing assembly interior surface of the high compressor, and the span is defined as a gap between a rotor disk of the high compressor and the engine casing assembly interior surface of the high compressor for at least a last two stages of the high compressor closest to a combustor section of the gas turbine engine. The system also includes at least two bowed rotor management systems for the gas turbine engine to prevent damage to the rotor blades for a bowed rotor condition of the high compressor under a plurality of operating conditions.

Abstract: A system for starting a gas turbine engine of an aircraft is provided. The system includes a pneumatic starter motor, a discrete starter valve switchable between an on-state and an off-state, and a controller operable to perform a starting sequence for the gas turbine engine. The starting sequence includes alternating on and off commands to an electromechanical device coupled to the discrete starter valve to achieve a partially open position of the discrete starter valve to control a flow from a starter air supply to the pneumatic starter motor to drive rotation of a starting spool of the gas turbine engine below an engine idle speed.

Abstract: A system for starting a gas turbine engine of an aircraft is provided. The system includes a pneumatic starter motor, a discrete starter valve switchable between an on-state and an off-state, and a controller operable to perform a starting sequence for the gas turbine engine. The starting sequence includes alternating on and off commands to an electromechanical device coupled to the discrete starter valve to achieve a partially open position of the discrete starter valve to control a flow from a starter air supply to the pneumatic starter motor to drive rotation of a starting spool of the gas turbine engine below an engine idle speed.

Abstract: A bowed rotor start mitigation system for a gas turbine engine is provided. The bowed rotor start mitigation system includes a controller operable to receive a vibration input indicative of an actual vibration level of the gas turbine engine and a speed input indicative of a rotor speed of the gas turbine engine. The controller generates a bowed rotor start mitigation request based on comparing the actual vibration level to a modeled vibration level at the rotor speed.

Abstract: A disclosed gas turbine engine includes a case for a case for a compressor section including a bleed air slot. The bleed air slot includes an inlet having a first area radially inward of an outlet having a second area with the second area being greater than the first area. The bleed air slot further includes a center portion disposed along a radial line extending from an axis of the engine and an elongated portion extending from the opening at an angle relative to a line normal to the radial line.

Abstract: A disclosed gas turbine engine includes a case for a case for a compressor section including a bleed air slot. The bleed air slot includes an inlet having a first area radially inward of an outlet having a second area with the second area being greater than the first area. The bleed air slot further includes a center portion disposed along a radial line extending from an axis of the engine and an elongated portion extending from the opening at an angle relative to a line normal to the radial line.