Turbofan engine including a double gearbox assembly having a double gearbox engine parameter

1 . A turbofan engine comprising:

a turbo-engine including a compressor section, a turbine section, and a combustor in fluid communication with the compressor section and the turbine section, the turbine section including a low-pressure turbine having a low-pressure shaft and a plurality of low-pressure turbine stages;

a fan having a fan shaft; and

a double gearbox assembly, the fan shaft being drivingly coupled to the low-pressure shaft through the double gearbox assembly, the double gearbox assembly comprising:

a first stage gear assembly coupled to the low-pressure shaft, the first stage gear assembly including a first stage sun gear, a plurality of first stage planet gears meshing with the first stage sun gear, and a first stage ring gear having a plurality of ring gear teeth and meshing with the plurality of first stage planet gears, and an interstage shaft; and

a second stage gear assembly coupled to the interstage shaft, the second stage gear assembly including a second stage sun gear, a plurality of second stage planet gears meshing with the second stage sun gear, and a second stage ring gear having a plurality of ring gear teeth and meshing with the plurality of second stage planet gears, and an output shaft coupled to the fan shaft,

wherein the double gearbox assembly is characterized by a Double Gearbox Engine Parameter (DGEP) in a range from 150 kilograms to 650 kilograms, the DGEP being given by:

k

×

S

×

∑

i

=

1

2

(

P

fan

×

10

6

×

z

i

376

×

ω

ring

⁢

i

×

n

planetsi

×

R

ring

⁢

i

2

×

π

×

R

ring

⁢

i

2

z

i

2

×

(

18.5

×

z

i

+

85.5625

)

)

wherein k is a constant value based on a number of the plurality of first stage planet gears or the plurality of second stage planet gears, S is a number of the plurality of low-pressure turbine stages, i is the first stage gear assembly or the second stage gear assembly, P fan is a power of the fan at high-power conditions, ω ring i is a rotational speed at high-power conditions of the first stage ring gear when i is 1 or the second stage ring gear when i is 2, n planetsi is a number of the plurality of first stage planet gears when i is 1 or the plurality of second stage planet gears when i is 2, R ring i is a ring gear pitch radius of the first stage ring gear when i is 1 or the second stage ring gear when i is 2, and z i is a number of the plurality of ring gear teeth of the first stage gear assembly when i is 1 or the second stage gear assembly when i is 2.

2 . The turbofan engine of claim 1 , wherein DGEP is in a range from 250 kilograms to 550 kilograms.

3 . The turbofan engine of claim 1 , wherein k is 1.59×10 −5 when the number of the plurality of first stage planet gears and the plurality of second stage planet gears is 5, or 1.17×10 −5 when the number of the plurality of first stage planet gears and the plurality of second stage planet gears is 3.

4 . The turbofan engine of claim 1 , wherein S is in a range from 2 to 6.

5 . The turbofan engine of claim 1 , wherein S is in a range from 3 to 5.

6 . The turbofan engine of claim 1 , wherein P fan is in a range from 11,000 kW to 15,000 kW.

7 . The turbofan engine of claim 1 , wherein ω ring i is in a range from 94 rad/s to 450 rad/s.

8 . The turbofan engine of claim 1 , wherein n planetsi is in a range from 3 to 6.

9 . The turbofan engine of claim 1 , wherein R ring i is in a range from 150 mm to 300 mm.

10 . The turbofan engine of claim 1 , wherein z i is in a range from 89 to 151.

11 . The turbofan engine of claim 1 , wherein the low-pressure shaft rotates in a counterclockwise direction and the fan shaft rotates in the counterclockwise direction such that the fan rotates in the counterclockwise direction.

12 . An engine system for an aircraft, the engine system comprising:

a first turbofan engine comprising:

a first turbo-engine including a compressor section, a turbine section, and a combustor in fluid communication with the compressor section and the turbine section, the turbine section including a low-pressure turbine having a first low-pressure shaft and a plurality of low-pressure turbine stages;

a first fan having a first fan shaft; and

a double gearbox assembly, the first fan shaft being drivingly coupled to the first low-pressure shaft through the double gearbox assembly, wherein the first low-pressure shaft rotates in a counterclockwise direction and the first fan shaft rotates in the counterclockwise direction such that the first fan rotates in the counterclockwise direction, the double gearbox assembly comprising:

a first stage gear assembly coupled to the first low-pressure shaft, the first stage gear assembly including a first stage sun gear, a plurality of first stage planet gears meshing with the first stage sun gear, and a first stage ring gear having a plurality of ring gear teeth and meshing with the plurality of first stage planet gears, and an interstage shaft; and

a second stage gear assembly coupled to the interstage shaft, the second stage gear assembly including a second stage sun gear, a plurality of second stage planet gears meshing with the second stage sun gear, and a second stage ring gear having a plurality of ring gear teeth and meshing with the plurality of second stage planet gears, and an output shaft coupled to the first fan shaft,

wherein the double gearbox assembly is characterized by a Double Gearbox Engine Parameter (DGEP) in a range from 150 kilograms to 650 kilograms, the DGEP being given by:

k

×

S

×

∑

i

=

1

2

⁢

(

P

fan

×

10

6

×

z

i

376

×

ω

ring

⁢

i

×

n

planetsi

×

R

ring

⁢

i

2

×

π

×

R

ring

⁢

i

2

z

i

2

×

(

18.5

×

z

i

+

85.5625

)

)

wherein k is a constant value based on a number of the plurality of first stage planet gears or the plurality of second stage planet gears, S is a number of the plurality of low-pressure turbine stages of the low-pressure turbine, i is the first stage gear assembly or the second stage gear assembly, P fan is a power of the first fan at high-power conditions, ω ring i is a rotational speed at high-power conditions of the first stage ring gear when i is 1 or the second stage ring gear when i is 2, n planetsi is a number of the plurality of first stage planet gears when i is 1 or the plurality of second stage planet gears when i is 2, R ring i is a ring gear pitch radius of the first stage ring gear when i is 1 or the second stage ring gear when i is 2, and z i is a number of the plurality of ring gear teeth of the first stage ring gear when i is 1 or the second stage ring gear when i is 2; and

a second turbofan engine comprising:

a second turbo-engine including a compressor section, a turbine section, and a combustor in fluid communication with the compressor section and the turbine section, the turbine section including a second low-pressure shaft;

a second fan having a second fan shaft; and

a gearbox assembly comprising a gear assembly, the second fan shaft being drivingly coupled to the second low-pressure shaft through the gearbox assembly, wherein the second low-pressure shaft rotates in the counterclockwise direction and the second fan shaft rotates in a clockwise direction such that the second fan rotates in the clockwise direction.

13 . The engine system of claim 12 , wherein DGEP is in a range from 250 kilograms to 550 kilograms.

14 . The engine system of claim 12 , wherein k is 1.59×10 −5 when the number of the plurality of first stage planet gears and the plurality of second stage planet gears is 5, or 1.17×10 −5 when the number of the plurality of first stage planet gears and the plurality of second stage planet gears is 3.

15 . The engine system of claim 12 , wherein S is in a range from 2 to 6.

16 . The engine system of claim 12 , wherein P fan is in a range from 11,000 kW to 15,000 kW.

17 . The engine system of claim 12 , wherein ω ring i is in a range from 94 rad/s to 450 rad/s.

18 . The engine system of claim 12 , wherein n planetsi is in a range from 3 to 6.

19 . The engine system of claim 12 , wherein R ring i is in a range from 150 mm to 300 mm.

20 . The engine system of claim 12 , wherein z i is in a range from 89 to 151.