A power transmission system includes a shaft, a stator disposed within the shaft and substantially concentric with the shaft; and at least one supporting element positioned between the stator and the shaft and configured to support the shaft on the stator to reduce a vibration of the shaft and allow the shaft to rotate relative to the stator. A gas turbine engine including the power transmission system is also described.

A dual-flow turbojet engine having a central shaft surrounded by a high-pressure body which rotate about the same longitudinal axis while being independent in rotation, and including a fan driven by the central pressure shaft; a high-pressure compressor and a high-pressure turbine mounted on the high-pressure body; an inter-turbine casing; a low-pressure turbine mounted on a low-pressure rotor surrounding the central shaft; an exhaust casing on which an output cone is mounted; a reduction gear with which the low-pressure rotor drives the central pressure shaft; two bearings mounted on the exhaust casing and respectively receiving the central shaft and the low-pressure rotor; a bearing mounted on the inter-turbine casing and receiving the low-pressure rotor.

According to an aspect, a system includes a memory system configured to store a plurality of instructions and a processing system. The processing system is configured to communicate with the memory system and execute the instructions that result in determining an initial torque applied to a component stack, determining an assembly torque and an angle of turn applied to the component stack after the initial torque is applied, and determining a friction value associated with the component stack. Execution of the instructions further result in determining a stack load of the component stack based on the friction value, the assembly torque, and the angle of turn, and outputting an indicator of the stack load.

An example embodiment of a turbine engine assembly includes a low spool including a low spool accessory drive gear driven by a low rotor shaft, a high spool including a high spool accessory drive gear driven by a high rotor shaft concentric around a portion of the low rotor shaft, and a differential gear assembly adapted to offtake power from rotation of one or both of the low spool and the high spool to drive one or more accessory loads. The differential gear assembly includes a differential bullgear and one or more idler gears each including a plurality of teeth meshed with the low spool accessory drive gear and the high spool accessory drive gear, and a bearing surface. The differential bull gear includes a plurality of teeth and a corresponding at least one bearing surface engaging with the bearing surface of each of the one or more idler gears. The plurality of teeth are adapted to mesh with an accessory drive system to transfer the power offtake and drive the one or more accessory loads.

A turbomachine engine includes a fan section having a fan shaft, and a core engine having one or more compressor sections, one or more turbine sections that includes a power turbine, and a combustion chamber in flow communication with the compressor sections and turbine sections. The turbomachine engine includes a low-speed shaft coupled to the power turbine and having a midshaft that extends from a forward bearing to an aft bearing. The low-speed shaft is characterized by a midshaft rating (MSR) between two hundred (ft/sec).sup.½ and three hundred (ft/sec).sup.½. The low-speed shaft has a redline speed between fifty and two hundred fifty feet per second (ft/sec). The turbomachine engine includes a gearbox assembly that couples the fan shaft to the low-speed shaft and characterized by a gearbox assembly mode less than 95% of a midshaft mode of the midshaft or greater than 105% of the midshaft mode.

The present disclosure relates to gearboxes for aircraft gas turbine engines, in particular to arrangements for journal bearings such gearboxes, and to related methods of operating such gearboxes and gas turbine engines. Example embodiments include a gearbox for an aircraft gas turbine engine, the gearbox comprising: a sun gear; a plurality of planet gears surrounding and engaged with the sun gear; and a ring gear surrounding and engaged with the plurality of planet gears, each of the plurality of planet gears being rotatably mounted around a pin of a planet gear carrier with a journal bearing having an internal sliding surface on the planet gear and an external sliding surface on the pin.

A bearing arrangement for a turbomachine includes first and second roller element bearings. The first bearing and the second bearing are disposed on opposite axial ends of an intermediate sleeve of the rotating group. The first bearing has a first inner race with a first inner radial surface and a first outer radial surface. The first inner radial surface has a first interference fit with a shaft of the rotating group. The first outer radial surface has a second interference fit with the intermediate sleeve. The second bearing has a second inner race with a second inner radial surface and a second outer radial surface. The second inner race receives the shaft with a clearance fit. The second outer radial surface has a third interference fit with the intermediate sleeve. The second inner race is coaxially aligned with the first inner race and the shaft via coaxial alignment of the intermediate sleeve and the first inner race.

A seal arrangement is disclosed for sealing an interior space between a bearing housing and a rotatable shaft with respect to a surrounding area. The seal arrangement includes a seal body which can be fastened to the bearing housing with a first end and a second end. The seal body is extended in an elongate manner along a main extent direction and is configured to be arranged in an annular manner around the rotatable shaft in a mounted state. The first end and the second end have a common butt joint. A projecting region is arranged at the first end of the seal body and projects tangentially with respect to the rotatable shaft in the direction of a predefined main rotational direction of the rotatable shaft. The projecting region projects beyond the seal body and overlaps the butt joint.

A gas turbine engine including: an exhaust diffuser including an inner tube and an outer tube that form therebetween an annular exhaust passage; a bearing chamber formed radially inside the inner tube for accommodating a bearing that supports a rotor of a turbine; a plurality of hollow struts extending across the exhaust passage; an oil introduction passage extending through one of the struts for introducing oil to be supplied to the bearing chamber; an oil drain passage extending through one of the struts for draining the oil from an exhaust oil inlet opened on a bottom surface of the bearing chamber; and an oil discharge passage for discharging a portion of the oil having passed through the oil introduction passage toward the oil drain inlet.

A compact and unobtrusive rotor control mechanism is presented that provides collective and cyclic pitch change to both rotors of a coaxial rotor system as well as a differential collective pitch change to one or both rotors simultaneously.