A splined shaft includes splines evenly distributed over the periphery, wherein the splines being spaced apart from each other. At least one portion of the splines are spaced apart by a modified pitch p with respect to the nominal pitch pn of the splines. The ratio of the absolute value of the difference between the modified pitch and the nominal pitch, to the nominal pitch, i.e. |pn−p|/pn, is different from zero, for example between 0.5 and 5%.

In accordance with at least one aspect of this disclosure, there is provided a drive shaft system. In embodiments, the drive shaft system includes a generator shaft extending along a longitudinal axis with a longitudinal bore defined through the generator shaft. A thru shaft extends through the longitudinal bore of the generator shaft. In embodiments, the thru shaft includes, a front coupler mount at a first end operative to receive torque input, and a rear coupler mount at a second end opposite the first end.

One or more cooling systems for ventilating a turbine and rotary shaft of a gas turbine system is provided. The gas turbine system includes a gas turbine engine and a turbine exhaust collector in separate enclosures. A first cooling system includes an educator that sucks exhaust gas through a diffuser and directs it out of the turbine exhaust collector enclosure based on suction pressure created from the high velocity of exhaust gas. A second cooling system include struts that enable the exhaust gas to flow from the diffusers to a ventilation flow stack. A third cooling system includes exhaust gas sucked from an opening to a top duct based on suction pressure created from the rotation of the rotary shaft disposed about a coupling. A guideway associated with the third cooling system also directs the exhaust gas to flow to the top duct. These cooling systems are designed to increase the efficiency of ventilating the turbine and rotary shaft, prevent misalignments of the rotary shaft, which may result in thermal stresses, and allow the use of the gas turbine systems in higher ambient temperature environments.

A hybrid electric propulsion system includes a gas turbine engine having at least one compressor section and at least one turbine section operably coupled to a shaft. The hybrid electric propulsion system includes an electric motor configured to augment rotational power of the shaft of the gas turbine engine. A controller is operable to determine an estimate of hybrid electric propulsion system parameters based on a composite system model and sensor data, determine a model predictive control state and a prediction based on the hybrid electric propulsion system parameters and the composite system model, determine a model predictive control optimization for a plurality of hybrid electric system control effectors based on the model predictive control state and the prediction using a plurality of reduced-order partitions of the composite system model, and actuate the hybrid electric system control effectors based on the model predictive control optimization.

A stator vane arrangement for a turbomachine comprises a radially inner annular structure, a radially outer annular structure and a plurality of circumferentially spaced vanes extending radially between the inner annular structure and the outer annular structure. At least one of the vanes has a passage extending from the inner annular structure to the outer annular structure. The inner annular structure has at least one radially inwardly extending boss and each boss has a passage extending there-through. The passage in each boss is aligned with a corresponding passage in a vane. Each boss comprises a first portion having a first cross-sectional area and a second portion having a second cross-sectional area which is greater than the first cross-sectional area. The first portion of each boss is positioned between and interconnecting the second portion of the boss and the inner annular structure.

A system includes a gas delivery disk coupled to a second shaft, wherein the second shaft and the gas delivery disk are disposed about an axis. The gas delivery disk includes an inner axial opening configured to facilitate a first axial flow through a first passage within the second shaft, a duct configured to supply a bearing flow in a radial direction toward the axis, and a bearing face disposed within the first passage and radially interior to the inner axial opening. The bearing face is configured to receive the bearing flow, and the bearing face is configured to form a gas bearing between the bearing face and a first shaft disposed about the axis.

A method for controlling a gas turbine assembly includes: a compressor in which compression of the outside air occurs for producing a flow of compressed air; a sequential combustor including a first combustor, in which combustion of a mixture of fuel and compressed air arriving from the compressor occurs for producing a flow of hot gasses, and a second combustor which is located downstream of the first combustor and in which combustion of a mixture of fuel and hot gasses arriving from the first combustor occurs; an intermediate turbine in which a partial expansion of the hot gasses arriving from the first combustor occurs; and a second combustor in which combustion of a mixture of fuel and hot gasses arriving from the intermediate turbine occurs; the method further includes, on a start-up transient operating phase of the gas turbine assembly, the step of controlling the fuel mass flow-rate supplied to the first and/or the second combustor on the basis of the flame temperature inside the first combustor.

There is described a shaft shear event detection method. The method comprises obtaining a demodulated waveform of a shaft oscillation wave superimposed on a shaft rotational speed signal, comparing the amplitude to an amplitude threshold, detecting oscillation when the amplitude threshold is exceeded for a plurality of samples, and detecting a shaft shear when oscillation continues for a predetermined time limit.

An air starter for an engine, such as a turbine engine, that includes a turbine for rotatably extracting mechanical power from a flow of fluid. The turbine includes a drive shaft that can be coupled to an output shaft to provide a rotational output. The interface between the drive shaft and the output shaft can be offset and include piloted portions.

A gas turbine engine includes a low speed spool mechanically interconnecting a low pressure turbine and at least one of a fan and a prop, a high speed spool mechanically interconnecting a high pressure turbine and a high pressure compressor, and an epicyclic gear system mechanically coupled to the high speed spool. The gas turbine engine also includes a low pressure compressor mechanically coupled to the high speed spool via the epicyclic gear system. The low pressure compressor may be mechanically independent of the low speed spool. The gas turbine engine may include a plurality of motor-generators for transferring power between the high speed spool and the low pressure compressor.