Differential gear system with carrier drive
A differential gear system for a gas turbine engine includes an assembly of a ring gear, a sun gear, and a plurality of planet gears, and a planet carrier. The plurality of planet gears are enmeshed between the ring gear and the sun gear. The planet carrier acts as an input to rotatably drive the planet gears, the sun gear, and ring gear of the gas turbine engine.
1. A method for transferring torque from an intermediate speed turbine to a first and a second rotating shaft of a gas turbine engine, the method comprising the steps of:
driving the intermediate speed turbine with combustion gases of the gas turbine engine;
transferring torque through an intermediate speed shaft from the intermediate speed turbine to a planet carrier of a differential gear system, the differential gear system additionally having a ring gear, a sun gear, and a plurality of planet gears enmeshed between the ring gear and sun gear, wherein the intermediate speed shaft is coupled to the intermediate speed turbine via an epicyclic gear system, and wherein the intermediate speed shaft is coupled to and drives the planet carrier, and wherein the planet carrier acts as an input to rotatably drive the planet gears, the sun gear, and the ring gear;
transferring torque from the planet carrier through the ring gear to the second shaft, wherein the second shaft is coupled to and driven by the ring gear, and wherein the second shaft is coupled to and rotates a fan of the gas turbine engine, and wherein the second shaft couples to a low speed shaft and the low speed shaft is also driven by a low speed turbine of the gas turbine engine; and
transferring torque from the planet carrier through the sun gear to the first shaft, wherein the first shaft is coupled to and driven by the sun gear, and wherein the first shaft is coupled to and rotates a low pressure compressor of the gas turbine engine.
2. The method of claim 1 , wherein the planet carrier, the sun gear, and the ring gear rotate at different rotational speeds.
3. The method of claim 1 , wherein the intermediate speed shaft and the first shaft are part of an intermediate pressure spool of the gas turbine engine.
4. A gas turbine engine, comprising:
a differential gear system having a planet carrier, a ring gear, a sun gear, and a plurality of planet gears enmeshed between the ring gear and sun gear, the planet carrier acting as an input to rotatably drive the planet gears, the sun gear, and the ring gear of the gas turbine engine;
an intermediate speed shaft that is coupled to and drives the planet carrier;
an epicyclic gear system coupling the intermediate speed shaft to an intermediate speed turbine;
a first shaft coupled to and driven by the sun gear, wherein the first shaft is coupled to and rotates a low pressure compressor of the gas turbine engine; and
a second shaft coupled to and driven by the ring gear, wherein the second shaft is coupled to and rotates a fan of the gas turbine engine, and wherein the second shaft couples to a low speed shaft and the low speed shaft is also driven by a low speed turbine of the gas turbine engine.
5. The gas turbine engine of claim 4 , wherein the planet carrier, the planet gears, the sun gear, and the ring gear are not tied to a stator ground.
6. The gas turbine engine of claim 4 , further comprising a journal bearing disposed within and extending from each of the planet gears, the journal bearing supported at one end by the planet carrier.
7. The gas turbine engine of claim 4 , wherein the epicyclic gear system is a planetary or star system type gear system.
8. The gas turbine engine of claim 4 , wherein the gas turbine engine has a high pressure spool, an intermediate pressure spool, and a low pressure spool.