Geared gas turbine engine
A gas turbine engine including: an engine core including turbine, compressor, and core shaft connecting the turbine to the compressor; a fan; an epicyclic gearbox that: (i) receives input from the core shaft to drive the fan at a lower rotational speed than the core shaft, and (ii) includes a sun gear, ring gear, planet carrier, and planet gears; and a gearbox support. The gearbox has a cross sectional area greater than or equal to 2.4×10 −1 m 2 . A first gearbox support strength ratio of: torsional strength of gearbox support radial bending stiffness of gearbox support × cross sectional area of gearbox is greater than or equal to 7.0×10 −3 ; and/or a second gearbox support strength ratio of: torsional strength of gearbox support tilt stiffness of gearbox support × planet gear spacing angle ( β ) is greater than or equal to 1.0×10 −1 , where the angle (β) is 2π/N, and N is the number of planet gears.
1. A gas turbine engine for an aircraft comprising:
an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;
a fan located upstream of the engine core, the fan comprising a plurality of fan blades;
a gearbox that is configured to: (i) receive an input from the core shaft and (ii) output drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, the gearbox being an epicyclic gearbox comprising a sun gear, a plurality of planet gears, a ring gear, and a planet carrier arranged to have the plurality of planet gears mounted thereon; and
a gearbox support arranged to at least partially support the gearbox within the engine, wherein:
the gearbox has a cross sectional area in a range from 2.4×10 −1 m 2 to 1.10 m 2 ; and
a first gearbox support strength ratio of:
a
torsional
strength
of
the
gearbox
support
a
radical
bending
stiffness
of
the
gearbox
support
×
the
cross
sectional
area
of
the
gearbox
is in a range from 7.0×10 −3 to 2.5×10 −1 .
2. The gas turbine engine according to claim 1 , wherein the first gearbox support strength ratio is in a range from 1.0×10 −2 to 2.5×10 −1 .
3. The gas turbine engine according to claim 1 , wherein the radial bending stiffness of the gearbox support is in a range from 1.0×10 7 N/m to 4.0×10 8 N/m.
4. The gas turbine engine according to claim 1 , wherein the torsional strength of the gearbox support is in a range from 1.60×10 5 Nm to 2.00×10 7 Nm.
5. The gas turbine engine according to claim 1 , wherein:
a planet gear spacing angle in radians (β) is defined as 2π/N, where N is a number of the planet gears; and
a second gearbox support strength ratio of:
a
torsional
strength
of
the
gearbox
support
a
tilt
stiffness
of
the
gearbox
support
×
the
planet
gear
spacing
angle
(
β
)
is in a range from 1.0×10 −1 to 3.5.
6. A gas turbine engine for an aircraft comprising:
an engine core comprising a turbine, a compressor, and a core shaft connecting the turbine to the compressor;
a fan located upstream of the engine core, the fan comprising a plurality of fan blades;
a gearbox that is configured to: (i) receive an input from the core shaft and (ii) output drive to the fan so as to drive the fan at a lower rotational speed than the core shaft, the gearbox being an epicyclic gearbox comprising a sun gear, a plurality of planet gears, a ring gear, and a planet carrier arranged to have the plurality of planet gears mounted thereon; and
a gearbox support arranged to at least partially support the gearbox within the engine, wherein:
a planet gear spacing angle in radians (β) is defined as 2π/N, where N is a number of the planet gears;
the gearbox has a cross sectional area in a range from 2.4×10 −1 m 2 to 1.10 m 2 ; and
a second gearbox support strength ratio of:
a
torsional
strength
of
the
gearbox
support
a
tilt
stiffness
of
the
gearbox
support
×
the
planet
gear
spacing
angle
(
β
)
is in a range from 1.0×10 −1 to 3.5.
7. The gas turbine engine according to claim 6 , wherein the second gearbox support strength ratio is in a range from 1.5×10 −1 to 1.7.
8. The gas turbine engine according to claim 6 , wherein the tilt stiffness of the gearbox support is in a range from 1.2×10 5 Nm/rad to 2.1×10 7 Nm/rad.
9. The gas turbine engine according to claim 6 , wherein the torsional strength of the gearbox support is in a range from 1.60×10 5 Nm to 2.00×10 7 Nm.
10. The gas turbine engine according to claim 6 , wherein:
a first gearbox support strength ratio of:
a
torsional
strength
of
the
gearbox
support
a
radical
bending
stifffness
of
the
gearbox
support
×
the
cross
sectional
area
of
the
gearbox
is in a range from 7.0×10 −3 to 2.5×10 −1 .
11. The gas turbine engine according to claim 1 , wherein the gearbox is in a star configuration.
12. The gas turbine engine according to claim 6 , wherein the planet gear spacing angle (β) is in a range between 9.0×10 −1 rad to 2.1 rad.
13. The gas turbine engine according to claim 1 , wherein the cross sectional area of the gearbox is in a range from 2.6×10 −1 m 2 to 1.10 m 2 .
14. The gas turbine engine according to claim 1 , wherein:
a torsional shear stress of the gearbox support, at maximum take-off conditions, is in a range from 1.40×10 8 N/m 2 to 4.90×10 8 N/m 2 .
15. The gas turbine engine according to claim 1 , wherein:
the turbine is a first turbine, the compressor is a first compressor, and the core shaft is a first core shaft;
the engine core further comprises a second turbine, a second compressor, and a second core shaft connecting the second turbine to the second compressor; and
the second turbine, the second compressor, and the second core shaft are arranged to rotate at a higher rotational speed than the first core shaft.
16. The gas turbine engine according to claim 1 , wherein at least one of the following is satisfied:
i) the gearbox is configured to have a gear ratio in a range from 3.2 to 4.5;
ii) the gas turbine engine is configured to have a specific thrust in a range from 70 to 90 NKg −1 ; and
iii) the gas turbine engine is configured to have a bypass ratio at cruise conditions in a range from 12.5 to 18.
17. The gas turbine engine according to claim 1 , wherein:
the fan has a fan diameter greater than 240 cm and less than or equal to 380 cm.
18. A propulsor for an aircraft, comprising:
a fan comprising a plurality of fan blades;
a gearbox;
a power unit for driving the fan via the gearbox, the gearbox being arranged to: (i) receive an input from the power unit via a core shaft and (ii) output drive to a fan shaft so as to drive the fan at a lower rotational speed than the core shaft, the gearbox being an epicyclic gearbox comprising a sun gear, a plurality of planet gears, a ring gear, and a planet carrier arranged to have the plurality of planet gears mounted thereon; and
a gearbox support arranged to at least partially support the gearbox within the propulsor,
wherein:
the gearbox has a cross sectional area in a range from 2.4×10 −1 m 2 to 1.10 m 2 , and
at least one of the following is satisfied:
a) a first gearbox support strength ratio of:
a
torsional
strength
of
the
gearbox
support
a
radical
bending
stifffness
of
the
gearbox
support
×
the
cross
sectional
area
of
the
gearbox
is in a range from 7.0×10 −3 to 2.5×10 −1 ; and
b) a planet gear spacing angle in radians (β) is defined as 2π/N, where N is a number of the planet gears ( 32 ); and a second gearbox support strength ratio of:
a
torsional
strength
of
the
gearbox
support
a
tilt
stiffness
of
the
gearbox
support
×
the
planet
gear
spacing
angle
(
β
)
is in a range from 1.0×10 −1 to 3.5.
19. A method of operating the gas turbine engine according to claim 1 ,
the method comprising operating the gas turbine engine to provide propulsion for the aircraft under cruise conditions.
20. The method of claim 19 , further comprising driving the gearbox with an input torque in a range from:
i) 10,000 to 50,000 Nm at cruise conditions; and/or
ii) 28,000 to 135,000 Nm at max-take off conditions.
21. A method of operating the gas turbine engine according to claim 6 , comprising operating the gas turbine engine to provide propulsion for the aircraft under cruise conditions.
22. The method according to claim 21 , further comprising driving the gearbox with an input torque in a range from:
i) 10,000 to 50,000 Nm at cruise conditions; and/or
ii) 28,000 to 135,000 Nm at max-take off conditions.
23. The gas turbine engine according to claim 1 , wherein the first gearbox support strength ratio is in a range from 7.0×10 −3 to 2.0×10 −2 .
24. The gas turbine engine according to claim 1 , wherein the first gearbox support strength ratio is in a range from 2.0×10 −2 to 2.5×10 −1 .
25. The gas turbine engine according to claim 1 , wherein the radial bending stiffness of the gearbox support is in a range from 3.0×10 7 N/m to 2.0×10 8 N/m.
26. The gas turbine engine according to claim 1 , wherein the torsional strength of the gearbox support is in a range from 1.8×10 5 Nm to 1.5×10 6 Nm.
27. The gas turbine engine according to claim 6 , wherein the second gearbox support strength ratio is in a range from 1.0×10 −1 to 2.5×10 −1 .
28. The gas turbine engine according to claim 6 , wherein the second gearbox support strength ratio is in a range from 2.5×10 −1 to 3.5.
29. The gas turbine engine according to claim 6 , wherein the tilt stiffness of the gearbox support is in a range from 3.9×10 5 Nm/rad to 9×10 6 Nm/rad.
30. The gas turbine engine according to claim 6 , wherein the torsional strength of the gearbox support is in a range from 1.8×10 5 Nm to 1.5×10 6 Nm.
31. The gas turbine engine according to claim 1 , wherein:
a torsional shear stress of the gearbox support, at maximum take-off conditions, is in a range 2.0×10 8 N/m 2 to 3.5×10 8 N/m 2 .