Flexible coupling for geared turbine engine
A gas turbine engine includes a fan shaft arranged along an engine central axis, a frame supporting the fan shaft, a gear system rotatably coupled with the fan shaft, and a flexible coupling at least partially supporting the gear system. The flexible coupling defines, with respect to the engine central axis, a torsional stiffness TS and a lateral stiffness LS such that a ratio of TS/LS is greater than or equal to about 2.0 to reduce loads on the gear system from misalignment of the gear system with respect to the engine central axis.
1. A gas turbine engine comprising:
a fan shaft arranged along an engine central axis;
a frame supporting the fan shaft, the frame defining a frame lateral stiffness;
a gear system rotatably coupled to the fan shaft, the gear system having a gear reduction ratio that is greater than 2.3; and
a first, non-rotatable flexible coupling and a second, rotatable flexible coupling supporting the gear system, the first flexible coupling and the second flexible coupling being subject to, with respect to the engine central axis, parallel offset guided end motion,
the first flexible coupling having a stiffness (D) that is torsional stiffness under the parallel offset guided end motion, and the first flexible coupling has a ratio of the frame lateral stiffness to the torisional stiffness that is in a range of 0.25 to 0.50.
2. The gas turbine engine as recited in claim 1 , wherein the gear system includes a sun gear in meshed engagement with multiple intermediate gears that are rotatably mounted on bearings in a non-rotatable carrier, each intermediate gear is in meshed engagement with a rotatable ring gear, the sun gear is rotatably coupled to the fan shaft, and the first, non-rotatable flexible coupling is coupled with the non-rotatable carrier.
3. The gas turbine engine as recited in claim 2 , wherein the gear system is coupled through an input shaft to a low pressure turbine, the low pressure turbine having a pressure ratio of greater than 5.
4. The gas turbine engine as recited in claim 3 , wherein the fan has a fan pressure ratio of less than 1.45.
5. The gas turbine engine as recited in claim 1 , wherein the gear system includes a sun gear in meshed engagement with multiple intermediate gears that are rotatably mounted on bearings in a rotatable carrier, each intermediate gear is in meshed engagement with a non-rotatable ring gear, the sun gear is rotatably coupled to the fan shaft, and the first, non-rotatable flexible coupling is coupled with the non-rotatable ring gear.
6. The gas turbine engine as recited in claim 5 , wherein the gear system is coupled through an input shaft to a low pressure turbine, the low pressure turbine having a pressure ratio of greater than 5.
7. The gas turbine engine as recited in claim 6 , wherein the fan has a fan pressure ratio of less than 1.45.
8. A gas turbine engine comprising:
a fan;
a fan shaft coupled with the fan and arranged along an engine central axis;
an input shaft;
a high pressure turbine and a low pressure turbine, the low pressure turbine having a pressure ratio of greater than 5;
a frame supporting the fan shaft, the frame defining a frame lateral stiffness;
a gear system rotatably coupled with the fan shaft and also rotatably coupled with the low pressure turbine through the input shaft; and
a first, non-rotatable flexible coupling and a second, rotatable flexible coupling supporting the gear system, the first flexible coupling and the second flexible coupling being subject to, with respect to the engine central axis, parallel offset guided end motion,
the first flexible coupling having a stiffness (D) that is torsional stiffness under the parallel offset guided end motion, and the first flexible coupling has a ratio of the frame lateral stiffness to the torisional stiffness that is in a range of 0.25 to 0.50.
9. The gas turbine engine as recited in claim 8 , wherein the gear system includes a sun gear in meshed engagement with multiple intermediate gears that are rotatably mounted on bearings in a non-rotatable carrier, each intermediate gear is in meshed engagement with a rotatable ring gear, the sun gear is rotatably coupled to the fan shaft, and the first, non-rotatable flexible coupling is coupled with the non-rotatable carrier.
10. The gas turbine engine as recited in claim 9 , wherein the gear system has a gear reduction ratio of greater than 2.3.
11. The gas turbine engine as recited in claim 10 , wherein the fan has a fan pressure ratio of less than 1.45.
12. The gas turbine engine as recited in claim 8 , wherein the gear system includes a sun gear in meshed engagement with multiple intermediate gears that are rotatably mounted on bearings in a rotatable carrier, each intermediate gear is in meshed engagement with a non-rotatable ring gear, the sun gear is rotatably coupled to the fan shaft, and the first, non-rotatable flexible coupling is coupled with the non-rotatable ring gear.
13. The gas turbine engine as recited in claim 12 , wherein the gear system has a gear reduction ratio of greater than 2.3.
14. The gas turbine engine as recited in claim 13 , wherein the fan has a fan pressure ratio of less than 1.45.
15. A gas turbine engine comprising:
a fan shaft arranged along an engine central axis;
a frame supporting the fan shaft, the frame defining a frame lateral stiffness;
a gear system rotatably coupled to the fan shaft, the gear system including a sun gear in meshed engagement with multiple intermediate gears that are rotatably mounted on bearings in a non-rotatable carrier, each intermediate gear in meshed engagement with a rotatable ring gear, and the sun gear rotatably coupled to the fan shaft; and
a first, non-rotatable flexible coupling and a second, rotatable flexible coupling supporting the gear system, the first flexible coupling and the second flexible coupling being subject to, with respect to the engine central axis, parallel offset guided end motion,
the first flexible coupling having a stiffness (D) that is torsional stiffness under the parallel offset guided end motion, and the first flexible coupling has a ratio of the frame lateral stiffness to the torsional stiffness that is in a range of 0.25 to 0.50.
16. The gas turbine engine as recited in claim 15 , wherein the fan has a fan pressure ratio of less than 1.45.
17. The gas turbine engine as recited in claim 16 , wherein the gear system is coupled through an input shaft to a low pressure turbine, the low pressure turbine having a pressure ratio of greater than 5.
18. The gas turbine engine as recited in claim 17 , wherein the gear system has a gear reduction ratio of greater than 2.3.
19. The gas turbine engine as recited in claim 15 , wherein the gear system is coupled through an input shaft to a low pressure turbine, the low pressure turbine having a pressure ratio of greater than 5.
20. The gas turbine engine as recited in claim 15 , wherein the gear system has a gear reduction ratio of greater than 2.3.
21. A gas turbine engine comprising:
a fan shaft arranged along an engine central axis;
a frame supporting the fan shaft, the frame defining a frame lateral stiffness;
a gear system rotatably coupled to the fan shaft, the gear system including a sun gear in meshed engagement with multiple intermediate gears that are rotatably mounted on bearings in a rotatable carrier, each intermediate gear in meshed engagement with a non-rotatable ring gear, and the sun gear rotatably coupled to the fan shaft; and
a first, non-rotatable flexible coupling and a second, rotatable flexible coupling supporting the gear system, the first flexible coupling and the second flexible coupling being subject to, with respect to the engine central axis, parallel offset guided end motion,
the first flexible coupling having a stiffness (D) defined with respect to the frame lateral stiffness, wherein is torsional stiffness under the parallel offset guided end motion, and the first flexible coupling has a ratio of frame lateral stiffness to the torisional stiffness that is in a range of 0.25 to 0.50.
22. The gas turbine engine as recited in claim 21 , wherein the fan has a fan pressure ratio of less than 1.45.
23. The gas turbine engine as recited in claim 22 , wherein the gear system is coupled through an input shaft to a low pressure turbine, the low pressure turbine having a pressure ratio of greater than 5.
24. The gas turbine engine as recited in claim 23 , wherein the gear system has a gear reduction ratio of greater than 2.3.
25. The gas turbine engine as recited in claim 21 , wherein the gear system is coupled through an input shaft to a low pressure turbine, the low pressure turbine having a pressure ratio of greater than 5.
26. The gas turbine engine as recited in claim 21 , wherein the gear system has a gear reduction ratio of greater than 2.3.