Turbofan engine assembly and method of assembling same

1. A method of assembling a turbofan engine assembly comprises:

providing a core gas turbine engine including a high-pressure compressor, a combustor disposed downstream from the high-pressure compressor, and a high-pressure turbine disposed downstream from the combustor, the high-pressure turbine being coupled to the high-pressure compressor by a first shaft;

drivingly coupling a first gearbox to a second shaft of a low-pressure turbine, the first gearbox being disposed upstream from the core gas turbine engine, the low-pressure turbine being disposed downstream of the high-pressure turbine, and the second shaft being concentric with the first shaft;

coupling a first fan assembly to the first gearbox;

coupling a second gearbox to the first gearbox such that during operation the second gearbox is driven by the first gearbox; and

coupling a booster compressor to the second gearbox, the booster compressor being disposed downstream from the first fan assembly, wherein the booster compressor rotates in a rotational direction opposite to a rotational direction of the first fan assembly.

2. A method in accordance with claim 1 , further comprising coupling a second fan assembly to the booster compressor such that the booster compressor and the second fan assembly rotate in the same rotational direction.

3. A method in accordance with claim 1 , further comprising coupling the booster compressor to a splitter and coupling the splitter to the second fan assembly such that the booster compressor and the second fan assembly rotate in the same rotational direction.

4. A method in accordance with claim 1 , further comprising coupling a low-pressure turbine to the first gearbox such that the low-pressure turbine drives the first gearbox.

5. A method in accordance with claim 1 , further comprising coupling an extension shaft between the first and second gearboxes to enable the first gearbox to drive the second gearbox.

6. A method in accordance with claim 5 , further comprising coupling a first drive shaft between the first fan assembly and the first gearbox such that the first gearbox drives the first fan assembly.

7. A method in accordance with claim 1 , further comprising coupling the first gearbox to the first fan assembly such that the first fan assembly rotates at a rotational speed that is different than the rotational speed of the low-pressure turbine.

8. A method in accordance with claim 1 , further comprising coupling a thrust bearing assembly between the first fan assembly and the low-pressure turbine to minimize pressure balance differences between the low-pressure turbine and the first fan assembly.

9. A method in accordance with claim 1 , further comprising coupling a thrust bearing assembly between the booster compressor and a fan frame.

10. A turbofan engine assembly comprising:

a core gas turbine engine including a high-pressure compressor, a combustor downstream from the high-pressure compressor, and a high-pressure turbine downstream from the compressor, said high-pressure turbine coupled to said high- pressure compressor;

a first fan assembly coupled within said turbofan engine assembly and located upstream from said core gas turbine engine;

a first gearbox coupled to said first fan assembly;

a booster compressor coupled within said turbofan engine assembly and located downstream from said first fan assembly;

a second gearbox coupled to said booster compressor such that said booster compressor rotates in a rotational direction that is opposite to the rotational direction of said first fan assembly, wherein during operation the second gearbox is driven by the first gearbox; and

a low-pressure turbine coupled to said first gearbox such that said low-pressure turbine drives said first gearbox.

11. A turbofan engine assembly in accordance with claim 10 , further comprising a second fan assembly coupled to said booster compressor such that said booster compressor and said second fan assembly rotate in the same rotational direction.

12. A turbofan engine assembly in accordance with claim 11 , further comprising a splitter cowling coupled between said booster compressor and said second fan assembly.

13. A turbofan engine assembly in accordance with claim 12 , wherein said second fan assembly is disposed downstream from said booster compressor.

14. A turbofan engine assembly in accordance with claim 10 , further comprising an extension shaft coupled between said first and said second gearboxes to enable said first gearbox to drive said second gearbox.

15. A turbofan engine assembly in accordance with claim 14 , further comprising a drive shaft coupled between said first fan assembly and said first gearbox such that the first gearbox drives the first fan assembly.

16. A turbofan engine assembly in accordance with claim 10 , further comprising a drive shaft coupled between a low-pressure turbine and said first gearbox, said first gearbox coupled to said first fan assembly such that said first fan assembly rotates at a rotational speed that is different than the rotational speed of the low-pressure turbine.

17. A turbofan engine assembly in accordance with claim 10 , further comprising a thrust bearing assembly coupled between said first fan assembly and a low-pressure turbine to minimize pressure balance differences between said low-pressure turbine and said first fan assembly.

18. A turbofan engine assembly in accordance with claim 10 , further comprising a thrust bearing assembly coupled between said booster compressor and a fan frame.

19. A turbofan engine assembly in accordance with claim 10 , further comprising a thrust bearing assembly coupled between said first fan assembly and a stationary support structure to facilitate transmitting residual thrust generated by said first fan assembly and a low-pressure turbine to said stationary support structure.