Turbine section of high bypass turbofan
View Patent ↗A turbofan engine has an engine case and a gaspath through the engine case. A fan has a circumferential array of fan blades. The engine further has a compressor, a combustor, a gas generating turbine, and a low pressure turbine section. A speed reduction mechanism couples the low pressure turbine section to the fan. A bypass area ratio is greater than about 6.0. The low pressure turbine section airfoil count to bypass area ratio ratio is below about 170.
1. A turbofan engine comprising:
an engine case;
a gaspath through the engine case;
a fan having a circumferential array of fan blades;
a compressor in fluid communication with the fan;
a combustor in fluid communication with the compressor;
a turbine in fluid communication with the combustor, the turbine having a low pressure turbine section having 3 to 6 blade stages; and
a speed reduction mechanism coupling the low pressure turbine section to the fan, wherein:
a ratio of maximum gaspath radius along the low pressure turbine section to maximum radius of the fan is less than about 0.55;
a bypass area ratio is greater than about 6.0; and
a ratio of a low pressure turbine section airfoil count to the bypass area ratio is less than about 170.
2. The engine of claim 1 wherein:
the bypass area ratio is greater than about 8.0.
3. The engine of claim 1 wherein:
the bypass area ratio is between about 8.0 and about 20.0.
4. The engine of claim 1 further comprising:
a fan case encircling the fan blades radially outboard of the engine case.
5. The engine of claim 1 wherein:
a hub-to-tip ratio (R I :R O ) of the low pressure turbine section is between about 0.4 and about 0.5 measured at the maximum R O axial location in the low pressure turbine section.
6. The engine of claim 5 wherein:
the low pressure turbine section has 3 to 5 blade stages.
7. The engine of claim 5 wherein:
a ratio of maximum gaspath radius along the low pressure turbine section to maximum radius of the fan is less than about 0.50.
8. The engine of claim 5 wherein:
an airfoil count of the low pressure turbine section is below about 1600.
9. The engine of claim 1 wherein:
the low pressure turbine section has blade stages interspersed with vane stages.
10. The engine of claim 1 wherein:
said ratio of maximum gaspath radius along the low pressure turbine section to maximum radius of the fan is less than about 0.50.
11. The engine of claim 10 wherein:
said ratio of maximum gaspath radius along the low pressure turbine section to maximum radius of the fan is between about 0.35 and about 0.50.
12. The engine of claim 1 wherein:
said ratio of low pressure turbine section airfoil count to bypass area ratio is between about 10 and about 150.
13. The engine of claim 1 wherein:
the compressor comprises:
a low pressure compressor section; and
a high pressure compressor section.
14. The engine of claim 13 wherein:
the turbine has a high pressure turbine section coupled to drive the high pressure compressor section.
15. The engine of claim 14 wherein:
there are no additional compressor or turbine sections.
16. The engine of claim 13 wherein:
blades of the low pressure compressor section and low pressure turbine section share a shaft; and
the speed reduction mechanism comprises an epicyclic transmission that couples the shaft to a fan shaft to drive the fan with a speed reduction.
17. The engine of claim 1 wherein:
the speed reduction mechanism comprises an epicyclic transmission.
18. The engine of claim 1 wherein:
the low pressure turbine section has 3 to 4 blade stages.
19. The engine of claim 1 wherein:
the low pressure turbine section has 3 blade stages.
20. The engine of claim 1 wherein:
an airfoil count of the low pressure turbine section is below about 1600.
21. The engine of claim 1 in combination with a mounting arrangement wherein an aft mount reacts at least a thrust load.
22. A turbofan engine comprising:
a fan case, and a gas generator including a core cowl, wherein the fan case and core cowl are configured so that a flow-path bypass ratio therebetween is greater than about 6.0; and
wherein:
a ratio of maximum gaspath radius along a low pressure turbine section to maximum radius of the fan is less than about 0.55; and
the gas generator includes a fan drive turbine configured so that a ratio of a turbine airfoil count to the bypass ratio is less than about 170.
23. The engine of claim 22 wherein:
the engine has only a single fan stage; and
the low pressure turbine section has blade stages interspersed with vane stages.