Turbofan engine bearing and gearbox arrangement
A turbofan engine ( 20 ) has a fan shaft ( 120 ) coupling a fan drive gear system ( 60 ) to the fan ( 28 ). A low spool includes a low pressure turbine ( 50 ) and a low shaft ( 56 ) coupling the low pressure turbine to the fan drive gear system. A core spool comprises a high pressure turbine ( 46 ), a compressor ( 44 ), and a core shaft ( 52 ) coupling the high pressure turbine to the core spool compressor. A first bearing ( 150 ) engages the fan shaft, the first bearing being a thrust bearing. A second bearing ( 160 ) engages the fan shaft on an opposite side of the fan drive gear system from the first bearing, the second bearing being a roller bearing. A third bearing ( 180 ) engages the low spool shaft and the fan shaft.
1. A turbofan engine comprising:
a fan;
a fan drive gear system;
a fan shaft coupling the fan drive gear system and the fan;
a low spool rotatable about a centerline axis, the low spool including a low pressure turbine driving the fan gear drive system through a low shaft;
an intermediate spool including an intermediate pressure turbine driving an intermediate pressure compressor through an intermediate shaft;
a core spool including a high pressure turbine driving a high pressure compressor through a core shaft;
a first bearing engaging the fan shaft;
a second bearing engaging the fan shaft and the low shaft; and
said second bearing being axially aft of the fan drive gear system with respect to the centerline axis.
2. The engine of claim 1 , wherein:
the fan drive gear system defines a speed reduction ratio between 2:1 and 13:1.
3. The engine of claim 1 , wherein:
the first bearing is axially aft of the fan drive gear system with respect to the centerline axis.
4. The engine of claim 3 , wherein:
an eighth bearing is oriented to resist at least forward movement of the fan shaft relative to the centerline axis.
5. The engine of claim 3 , wherein:
the second bearing is nested within the first bearing relative to the centerline axis.
6. The engine of claim 3 , further comprising:
a third bearing engaging the low shaft and a fixed frame that extends across a core flow path.
7. The engine of claim 6 , wherein:
one of the second and third bearings is a non-thrust bearing.
8. The engine of claim 6 , wherein:
the fixed frame is aft of the high pressure turbine with respect to the centerline axis.
9. The engine of claim 6 , wherein:
one of the second and third bearings is a thrust bearing.
10. The engine as set forth in claim 3 , wherein an eighth bearing supports said fan shaft and is axially forward of the fan drive gear system with respect to the centerline axis.
11. The engine of claim 1 , further comprising:
a fourth bearing engaging the low shaft and the intermediate shaft; and
a fifth bearing engaging the intermediate shaft.
12. The engine of claim 11 , wherein:
at least one of the fourth and fifth bearings is a thrust bearing.
13. The engine of claim 12 , wherein:
the second bearing is nested within the first bearing relative to the centerline axis.
14. The engine of claim 1 , further comprising:
a sixth bearing engaging the core shaft and a case; and
a seventh bearing engaging the core shaft and the case.
15. The engine of claim 1 , wherein:
the intermediate pressure turbine is a single or double stage turbine.
16. The engine of claim 15 , wherein:
the fan is a single-stage fan.
17. The engine of claim 16 , wherein:
the fan drive gear system defines a speed reduction ratio between 2:1 and 13:1.
18. A turbofan engine comprising:
a fan;
a fan drive gear system;
a fan shaft coupling the fan drive gear system and the fan;
a low spool rotatable about a centerline axis, the low spool including a low pressure turbine driving the fan gear drive system through a low shaft;
an intermediate spool including an intermediate pressure turbine driving an intermediate pressure compressor through an intermediate shaft;
a core spool including a high pressure turbine driving a high pressure compressor through a core shaft;
a first bearing engaging the fan shaft;
a second bearing engaging the fan shaft and the low shaft;
the fan drive gear system defines a speed reduction ratio between 2:1 and 13:1;
the first bearing is oriented to resist at least forward movement of the fan shaft relative to the centerline axis; and
the first bearing is axially forward of the second bearing with respect to the centerline axis.
19. The engine of claim 18 , wherein:
the first bearing engages a support extending inwardly from a forward frame.
20. A turbofan engine comprising:
a fan;
a fan drive gear system;
a fan shaft coupling the fan drive gear system and the fan;
a low spool rotatable about a centerline axis, the low spool including a low pressure turbine driving the fan gear drive system through a low shaft;
an intermediate spool including an intermediate pressure turbine driving an intermediate pressure compressor through an intermediate shaft;
a core spool including a high pressure turbine driving a high pressure compressor through a core shaft;
a first bearing engaging the fan shaft;
a second bearing engaging the fan shaft and the low shaft;
a sixth bearing engaging the core shaft and a case;
a seventh bearing engaging the core shaft and the case;
at least one of the sixth and seventh bearings is a thrust bearing; and
the first bearing is a non-thrust bearing.