초록 ▼

A gas turbine engine having an electric generator includes a transmission shaft extending along a longitudinal axis of the engine and drivingly interconnecting a turbine shaft of the engine and a rotor shaft of the electric generator. The transmission shaft is engaged by splined mating connections w

A gas turbine engine having an electric generator includes a transmission shaft extending along a longitudinal axis of the engine and drivingly interconnecting a turbine shaft of the engine and a rotor shaft of the electric generator. The transmission shaft is engaged by splined mating connections with the turbine shaft and the rotor shaft. The transmission shaft has a shear neck defining a reduced radial wall thickness with respect to a remainder of the transmission shaft such as to provide a weakened region of the transmission shaft. An annular support structure, concentric with and surrounding the transmission shaft, is axially located between the shear neck and a forward end of the transmission shaft engaged to the turbine shaft, and includes a bearing operable to rotationally support the transmission shaft.

대표청구항 ▼

1. A gas turbine engine having an electric generator, comprising: a transmission shaft extending along a longitudinal axis of the engine and drivingly interconnecting a turbine shaft of the engine and a rotor shaft of the electric generator, opposed forward and rearward ends of the transmission shaf

1. A gas turbine engine having an electric generator, comprising: a transmission shaft extending along a longitudinal axis of the engine and drivingly interconnecting a turbine shaft of the engine and a rotor shaft of the electric generator, opposed forward and rearward ends of the transmission shaft being respectively engaged in splined mating connection with the turbine shaft of the engine and the rotor shaft of the electrical generator, such that the transmission shaft is axially movable relative to at least one of the turbine shaft and the rotor shaft, the transmission shaft having a shear neck proximate the rearward end thereof, the shear neck defining a reduced radial wall thickness with respect to a remainder of the transmission shaft such as to provide a weakened region of the transmission shaft; andan annular support structure concentric with and surrounding the transmission shaft, the support structure being axially located between the shear neck and the forward end of the transmission shaft and including a bearing operable to rotationally support the transmission shaft, the bearing including an annular bumper surrounding the transmission shaft with a radial clearance being defined therebetween, an oil source adjacent the bumper and providing oil to the clearance, and a pressurized oil film created by the oil source circulating around and along the transmission shaft within the clearance, the support structure defining a hydrodynamic journal bearing rotationally supporting the transmission shaft. 2. The engine as defined in claim 1, wherein the shear neck has a reduced diameter, relative to the remainder of the transition shaft, about a full circumference of the transmission shaft. 3. The engine as defined in claim 1, wherein the oil source includes an actuation mechanism to alternately allow and prevent a flow of oil therefrom, the actuation mechanism preventing the flow of oil when the weakened region remains intact. 4. The engine as defined in claim 3, wherein the generator is contained in an air-exposed cavity, the engine further comprising an air-filled sealed buffer cavity surrounding the transmission shaft between the support structure and the shear neck to prevent the oil from entering the air-exposed cavity. 5. The engine as defined in claim 4, wherein the transmission shaft includes a hollow core for circulation of pressurized air, the core being in fluid communication with the sealed buffer cavity, the pressurized air within the core and pressurized oil film around the transmission shaft being in heat exchange relationship with one another. 6. The engine as defined in claim 1, wherein the bumper including at least one angled slot defined in an inner surface thereof adjacent the oil source and directing the oil to form the pressurized oil film around the transmission shaft. 7. The engine as defined in claim 6, wherein the bumper is located between the oil source and the weakened region, the bumper including at least one wind back angled groove defined in the inner surface adjacent a weakened region side of the bumper, the wind back groove being angled opposite of the angled slot to direct the oil back toward the oil source, and at least one release hole extending through the bumper and providing fluid communication between the clearance and an oil-exposed cavity through which the transmission shaft extends. 8. A gas turbine engine comprising: a transmission shaft drivingly interconnecting a driving shaft and a driven shaft, the transmission shaft having a weakened region defining a reduced radial wall thickness sized to rupture upon being subjected to a torque exceeding a predetermined threshold to separate the transmission shaft into two portions, a first portion and a second portion;the second portion being rotationally supported by the driven shaft; anda hydrodynamic bearing rotationally supporting the first portion of the transmission shaft and axially located between the weakened region and the driving shaft, the hydrodynamic bearing including a stationary annular support structure concentric with and surrounding the first portion with an annular radial clearance being defined between the support structure and the transmission shaft, and an oil nozzle connected to an oil source and providing oil within the clearance, the clearance being sized to create a pressurized oil film therewithin. 9. The engine as defined in claim 8, wherein the weakened region is defined by a shear neck formed in the transmission shaft. 10. The engine as defined in claim 8, wherein the oil nozzle provides oil to the clearance during both normal engine operation and when the weakened region is ruptured. 11. The engine as defined in claim 8, wherein the driven shaft extends at least partially through an air-exposed cavity, the assembly further including an air-filled sealed buffer cavity surrounding the transmission shaft between the support structure and the weakened region to prevent the oil from entering the air-exposed cavity. 12. The engine as defined in claim 11, wherein the transmission shaft includes a hollow core for circulation of pressurized air, the core being in fluid communication with the sealed buffer cavity, the pressurized air within the core and pressurized oil film around the transmission shaft being in heat exchange relationship with one another. 13. The engine as defined in claim 8, wherein the support structure includes a bumper concentric with the transmission shaft and defining the annular clearance, the bumper including at least one angled slot defined in an inner surface thereof at an end of the bumper adjacent the oil nozzle, the slot being oriented to direct the oil film away from the nozzle. 14. The engine as defined in claim 13, wherein the bumper includes a collecting groove defined in the inner surface, the collecting groove being in fluid communication with release holes defined through the bumper to expel the oil away from the transmission shaft, the collecting groove being located away from an end of the bumper adjacent the oil nozzle. 15. The engine as defined in claim 8, wherein the support structure includes a bumper concentric with the transmission and defining the annular clearance, the bumper being made of bronze. 16. A method of allowing continued operation of a gas turbine engine in the event of a failure of a tail-mounted electric generator disposed rearwardly of a turbine shaft of the engine, comprising: rotating a rotor shaft of the generator using a transmission shaft driven by the turbine shaft and axially extending therebetween, the transmission shaft having opposed forward and rearward ends that are respectively supported by the turbine shaft of the engine and the rotor shaft of the electrical generator, the transmission shaft extending through an annular support structure disposed between the forward and rearward ends thereof;allowing a rupture of the transmission shaft to occur at a weakened region axially located between the rearward end of the transmission shaft and the annular support structure when the transmission shaft is exposed to a torque exceeding a predetermined threshold; andat least when the transmission shaft is ruptured, rotationally supporting the forward end of the transmission shaft driven by the turbine shaft by the annular support structure, including creating a pressurized oil film between the forward end and the annular support structure, and using the pressured oil film as a hydrodynamic bearing to rotationally support the forward end of the transmission shaft. 17. The method as defined in claim 16, further including, prior to the transmission shaft being ruptured, cooling the transmission shaft within the annular structure by creating the pressurized oil film between the transmission shaft and the annular structure. 18. The method as defined in claim 16, further comprising creating the pressurized oil film by circulating the oil toward the rearward end of the transmission shaft, preventing the oil from entering a generator cavity containing the generator and at least part of the rearward end of the transmission shaft by circulating pressurized air within the transmission shaft in heat exchange relationship with the pressurized oil film to a pressurized buffer cavity which surrounds the transmission shaft and seals an entry of the generator cavity around the transmission shaft.