Low pressure ratio fan engine having a dimensional relationship between inlet and fan size

1. A gas turbine engine assembly, comprising:

a fan section including a fan, the fan including a plurality of fan blades, a diameter of the fan having a dimension D that is based on a dimension of the fan blades, each fan blade having a leading edge, and a forward most portion on the leading edges of the fan blades in a first reference plane;

a geared architecture;

a turbine section including a high pressure turbine and a low pressure turbine, the low pressure turbine driving the fan through the geared architecture;

a nacelle surrounding the fan, the nacelle including an inlet portion forward of the fan, a forward edge on the inlet portion in a second reference plane, and a length of the inlet portion having a dimension L measured along an engine axis between the first reference plane and the second reference plane;

wherein the fan delivers a portion of air into a compressor section and a portion of air into a bypass duct, and a bypass ratio of greater than 10, the bypass ratio being a ratio of a volume of air passing to the bypass duct compared to a volume of air passing into the compressor section;

wherein the fan has a pressure ratio between 1.20 and 1.50 at a cruise design point;

wherein a dimensional relationship of L/D is no more than 0.45; and

wherein the low pressure turbine includes an inlet, an outlet, and a pressure ratio of greater than 5:1.

2. The assembly of claim 1 , wherein the geared architecture defines a gear reduction ratio of greater than 2.3.

3. The assembly of claim 2 , wherein the dimensional relationship of L/D is between 0.2 and 0.45.

4. The assembly of claim 3 , wherein the high pressure turbine includes two stages.

5. The assembly of claim 4 , wherein the dimensional relationship of L/D is no less than 0.30.

6. The assembly of claim 5 , further comprising:

an inner shaft concentric with an outer shaft;

wherein the inner shaft connects the fan and a low pressure compressor to the low pressure turbine such that the inner shaft drives the fan through the geared architecture; and

wherein the outer shaft interconnects a high pressure compressor to the high pressure turbine.

7. The assembly of claim 6 , wherein the pressure ratio of the fan is less than 1.45 at the cruise design point.

8. The assembly of claim 6 , wherein the fan has a low corrected fan tip speed of less than 1150 ft/second.

9. The assembly of claim 8 , wherein the dimensional relationship of L/D is between 0.30 and 0.40.

10. The assembly of claim 8 , wherein the turbine section includes a mid-turbine frame between the high pressure turbine and the low pressure turbine.

11. The assembly of claim 10 , wherein the mid-turbine frame includes a plurality of vanes in a core airflow path defined by the turbine section.

12. The assembly of claim 11 , wherein the plurality of vanes are inlet guide vanes.

13. The assembly of claim 12 , wherein the inlet guide vanes set airflow entering the low pressure turbine during operation.

14. The assembly of claim 13 , wherein the dimensional relationship of L/D is about 0.35.

15. The assembly of claim 14 , wherein:

the second reference plane is oriented at an oblique angle relative to the engine axis; and

the oblique angle is approximately 5 degrees.

16. The assembly of claim 3 , further comprising:

an inner shaft concentric with an outer shaft;

wherein the inner shaft connects the fan and a low pressure compressor to the low pressure turbine such that the inner shaft drives the fan through the geared architecture; and

wherein the outer shaft interconnects a high pressure compressor to the high pressure turbine.

17. The assembly of claim 16 , wherein the turbine section includes a mid-turbine frame between the high pressure turbine and the low pressure turbine.

18. The assembly of claim 17 , wherein the mid-turbine frame includes a plurality of vanes in a core airflow path defined by the turbine section.

19. The assembly of claim 18 , wherein:

the plurality of vanes are inlet guide vanes; and

the inlet guide vanes set airflow entering the low pressure turbine during operation.

20. The assembly of claim 19 , wherein the mid-turbine frame supports bearing systems.

21. The assembly of claim 16 , wherein the fan has a low corrected fan tip speed of less than 1150 ft/second.

22. The assembly of claim 21 , wherein the dimensional relationship of L/D is between 0.30 and 0.40.

23. The assembly of claim 22 , wherein the pressure ratio of the fan is less than 1.45 at the cruise design point.

24. The assembly of claim 1 , wherein the dimensional relationship of L/D is between 0.2 and 0.45.

25. The assembly of claim 24 , wherein the pressure ratio of the fan is less than 1.45 at the cruise design point.

26. The assembly of claim 25 , wherein the fan has a low corrected fan tip speed of less than 1150 ft/second.

27. The assembly of claim 25 , wherein:

the turbine section includes a mid-turbine frame between the high pressure turbine and the low pressure turbine;

the mid-turbine frame supports bearing systems; and

the mid-turbine frame includes a plurality of vanes in a core airflow path defined by the turbine section.

28. The assembly of claim 27 , wherein the plurality of vanes are inlet guide vanes.

29. The assembly of claim 25 , wherein the high pressure turbine includes two stages.

30. The assembly of claim 25 , wherein the geared architecture defines a gear reduction ratio of greater than 2.3.