Epicyclic gear train
A gas turbine engine according to an example of the present disclosure includes, among other things, a propulsor section including a propulsor supported on a propulsor shaft, a turbine section including a turbine shaft, a compressor section, and an epicyclic gear train interconnecting the propulsor shaft and the turbine shaft. The gear train includes a sun gear coupled to the turbine shaft, intermediary gears arranged circumferentially about and meshing with the sun gear, a carrier supporting the intermediary gears, and a ring gear including first and second portions each having an inner periphery with teeth intermeshing with the intermediate gears. The first and second portions have axially opposed faces abutting one another at a radial interface. The first and second portions have grooves at the radial interface that form a hole that expels oil through the ring gear.
1. A gas turbine engine comprising:
a propulsor section including a propulsor supported on a propulsor shaft;
a turbine section including a turbine shaft, wherein the turbine section has a fan drive turbine including a pressure ratio of greater than 5;
a compressor section having compressor hubs with blades driven by the turbine shaft about an axis; and
an epicyclic gear train interconnecting the propulsor shaft and the turbine shaft, the epicyclic gear train comprising:
a sun gear coupled to the turbine shaft such that the sun gear is rotatable about the axis;
intermediary gears arranged circumferentially about and meshing with the sun gear;
a carrier supporting the intermediary gears, wherein each of the intermediate gears is supported on a respective journal bearing secured to the carrier, each journal bearing has an internal central cavity that extends between axial ends, and each journal bearing has at least one passage that extends radially from the internal central cavity to a peripheral journal surface of the respective journal bearing; and
a ring gear including first and second portions, the first and second portions each having an inner periphery with teeth intermeshing with the intermediate gears, the first and second portions having axially opposed faces abutting one another at a radial interface, the first and second portions including respective flanges extending along the radial interface radially outward from the teeth, and wherein the first and second portions having grooves at the radial interface that form a hole that expels oil through the ring gear.
2. The gas turbine engine as recited in claim 1 , wherein the at least one passage includes a first passage and a second passage axially spaced from the first passage relative to an axis of the internal central cavity.
3. The gas turbine engine as recited in claim 2 , wherein the internal central cavity extends between axial ends, and the first passage and the second passage are non-uniformly spaced with regard to the axial ends.
4. The gas turbine engine as recited in claim 3 , wherein the internal central cavity is axially blind such that one of the axial ends is closed.
5. The gas turbine engine as recited in claim 2 , wherein the hole is arranged to expel oil through the ring gear to a gutter secured to the carrier.
6. The gas turbine engine as recited in claim 5 , wherein the teeth of the first portion and the teeth of the second portion are oppositely angled teeth arranged to force the first and second portions toward one another at the radial interface, and a trough separates the oppositely angled teeth.
7. The gas turbine engine as recited in claim 1 , wherein the epicyclic gear train is a planetary gear system.
8. The gas turbine engine as recited in claim 7 , wherein the epicyclic gear train defines a gear reduction ratio of greater than or equal to 2.5.
9. The gas turbine engine as recited in claim 8 , wherein the at least one passage includes a first passage and a second passage axially spaced from the first passage relative to an axis of the internal central cavity.
10. The gas turbine engine as recited in claim 1 , wherein the epicyclic gear train is a star gear train, and the propulsor shaft is coupled to the ring gear.
11. The gas turbine engine as recited in claim 10 , wherein the epicyclic gear train defines a gear reduction ratio of greater than or equal to 2.3.
12. The gas turbine engine as recited in claim 11 , wherein the carrier is fixed to a housing by a torque frame.
13. The gas turbine engine as recited in claim 11 , wherein the propulsor shaft includes a radially outward extending flange secured to the flanges of the first and second portions of the ring gear.
14. The gas turbine engine as recited in claim 13 , wherein the hole is arranged to expel oil through the ring gear to a gutter secured to the carrier.
15. The gas turbine engine as recited in claim 14 , wherein the gear reduction ratio is greater than or equal to 2.5.
16. The gas turbine engine as recited in claim 15 , further comprising:
seals having knife edges secured to the flanges of the first and second portions; and
wherein the seals include oil return passages provided by slots in the seals, or provided in the radially outward extending flange of the propulsor shaft and an oil baffle secured to the carrier.
17. The gas turbine engine as recited in claim 1 , wherein the gear reduction ratio is greater than or equal to 2.5.
18. The gas turbine engine as recited in claim 17 , wherein the propulsor is a turbo fan, and the propulsor shaft is a fan shaft supporting the fan.
19. The gas turbine engine as recited in claim 18 , wherein the hole is arranged to expel oil through the ring gear to a gutter secured to the carrier.
20. The gas turbine engine as recited in claim 19 , wherein the fan includes a pressure ratio of less than 1.45 across the fan blade alone, the fan has a bypass ratio of greater than 10.5, and the at least one passage includes a first passage and a second passage axially spaced from the first passage relative to an axis of the internal central cavity.
21. The gas turbine engine as recited in claim 20 , wherein the teeth of the first portion and the teeth of the second portion are oppositely angled teeth arranged to force the first and second portions toward one another at the radial interface, and a trough separates the oppositely angled teeth.
22. The turbine engine as recited in claim 21 , further comprising a low corrected fan tip speed of less than 1150 ft/second.
23. The gas turbine engine as recited in claim 22 , wherein the internal central cavity extends between axial ends, the first passage and the second passage are non-uniformly spaced with regard to the axial ends, and the first and second portions include facing recesses that form an internal annular cavity along the radial interface.
24. The gas turbine engine as recited in claim 23 , wherein the internal central cavity is axially blind such that one of the axial ends is closed, and a backside of the respective first and second portions includes a generally S-shaped outer circumferential surface.
25. The gas turbine engine as recited in claim 22 , wherein the epicyclic gear train is a planetary gear system.
26. The gas turbine engine as recited in claim 22 , wherein the epicyclic gear train is a star gear train, a radially outward extending flange of the fan shaft is secured to the flanges of the first and second portions, and the carrier is fixed to a housing by a torque frame.
27. The turbine engine as recited in claim 22 , wherein the epicyclic gear train is intermediate a compressor rotor and a shaft driven by the fan drive turbine such that a fan rotor and a first stage compressor are rotatable at a common speed.
28. A gas turbine engine comprising:
a propulsor section including a propulsor supported on a propulsor shaft;
a turbine section including a turbine shaft;
a compressor section having compressor hubs with blades driven by the turbine shaft about an axis; and
an epicyclic gear train interconnecting the propulsor shaft and the turbine shaft, the epicyclic gear train comprising:
a sun gear coupled to the turbine shaft such that the sun gear is rotatable about the axis;
intermediary gears arranged circumferentially about and meshing with the sun gear;
a carrier supporting the intermediary gears, wherein each of the intermediate gears is supported on a respective journal bearing secured to the carrier, each journal bearing has an internal central cavity that extends between axial ends, and each journal bearing has at least one passage that extends radially from the internal central cavity to a peripheral journal surface of the respective journal bearing; and
a ring gear including first and second portions, the first and second portions each having an inner periphery with teeth intermeshing with the intermediate gears, the first and second portions having axially opposed faces abutting one another at a radial interface, the first and second portions including respective flanges extending along the radial interface radially outward from the teeth, and wherein the first and second portions having grooves at the radial interface that form a hole that expels oil through the ring gear;
wherein the epicyclic gear train is a star gear train, the propulsor shaft is coupled to the ring gear, and the propulsor shaft includes a radially outward extending flange secured to the flanges of the first and second portions of the ring gear; and
wherein the epicyclic gear train defines a gear reduction ratio of greater than or equal to 2.3.
29. The gas turbine engine as recited in claim 28 , wherein the hole is arranged to expel oil through the ring gear to a gutter secured to the carrier.
30. The gas turbine engine as recited in claim 29 , wherein the gear reduction ratio is greater than or equal to 2.5.
31. The gas turbine engine as recited in claim 30 , further comprising:
seals having knife edges secured to the flanges of the first and second portions; and
wherein the seals include oil return passages provided by slots in the seals, or provided in the radially outward extending flange of the propulsor shaft and an oil baffle secured to the carrier.