Geared gas turbine engine
Gas turbine engine for aircraft includes: an engine core including a turbine, compressor, and core shaft connecting the turbine to the compressor; a fan located upstream of the core; a gearbox; and a gearbox support arranged to at least partially support the gearbox. The fan has a mass in a range of 150 kg to 1200 kg. A moment of inertia of the fan is greater than or equal to 7.40×10 7 kgmm 2 . A radial bending stiffness to moment of inertia ratio of: the radial bending stiffness of at least one of the fan shaft at the output of the gearbox and the gearbox support the moment of inertia of the fan may be greater than or equal to 2.5×10 −2 Nkg −1 m −1 mm −2 . A tilt stiffness to moment of inertia ratio of: the tilt stiffness of at least one of the fan shaft at the output of the gearbox and the gearbox support the moment of inertia of the fan may be greater than or equal to 4.0×10 −4 Nmrad −1 kg −1 mm −2 .
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 receive an input from the core shaft, and output drive to a fan shaft via an output of the gearbox 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 moment of inertia of the fan is in a range from 7.40×10 7 kgmm 2 to 9.00×10 8 kgmm 2 ;
at least one radial bending stiffness to moment of inertia ratio selected from the group consisting of:
a first ratio of:
a
radial
bending
stiffness
of
the
fan
shaft
at
the
output
of
the
gearbox
the
moment
of
inertia
of
the
fan
,
and
a second ratio of:
a
radial
bending
stiffness
of
the
gearbox
support
the
moment
of
inertia
of
the
fan
is in a range from 2.5×10 −2 Nkg −1 m −1 mm −2 to 6.0 Nkg −1 m −1 mm −2 , and
the fan has a mass in a range of 150 kg to 1200 kg.
2. The gas turbine engine according to claim 1 , wherein the at least one radial bending stiffness to moment of inertia ratio is in a range from 0.05 Nkg −1 m −1 mm −2 to 3.0 Nkg −1 m −1 mm −2 .
3. The gas turbine engine according to claim 1 , wherein:
a) the first ratio of the radial bending stiffness of the fan shaft at the output of the gearbox to the moment of inertia of the fan is in a range from 0.05 Nkg −1 m −1 mm −2 to 3.0 Nkg −1 m −1 mm −2 ; and/or
b) the second ratio of the radial bending stiffness of the gearbox support to the moment of inertia of the fan is in a range from 3.0×10 −2 Nkg −1 m −1 mm −2 to 4.0 Nkg −1 m −1 mm −2 .
4. The gas turbine engine according to claim 1 , wherein:
a) the radial bending stiffness of the fan shaft at the output of the gearbox is in a range from 3.7×10 7 N/m to 1.0×10 9 N/m; and/or
b) the radial bending stiffness of the gearbox support is in a range from 2.0×10 7 N/m to 3.0×10 8 N/m.
5. The gas turbine engine according to claim 1 , wherein:
a) a diameter of the fan is in a range from 240 cm to 280 cm, and the at least one radial bending stiffness to moment of inertia ratio is in a range from 0.05 Nkg −1 m −1 mm −2 to 4.0 Nkg −1 m −1 mm −2 ; or
b) the diameter of the fan is in a range from 330 cm to 380 cm and the at least one radial bending stiffness to moment of inertia ratio is in a range from 0.025 Nkg −1 m −1 mm −2 to 2.0 Nkg −1 m −1 mm −2 .
6. The gas turbine engine according to claim 1 , wherein at least one product selected from the group consisting of:
a first product of:
(the radial bending stiffness of the fan shaft at the output of the gearbox)×(the moment of inertia of the fan), and
a second product of:
(the radial bending stiffness of the gearbox support)×(the moment of inertia of the fan)
is in a range from 2.0×10 14 Nkgmm 2 m −1 to 1.4×10 18 Nkgmm 2 m −1 .
7. The gas turbine engine according to claim 1 , wherein at least one tilt stiffness to moment of inertia ratio selected from the group consisting of:
a first tilt stiffness ratio of:
a
tilt
stiffness
of
the
fan
shaft
at
the
output
of
the
gearbox
the
moment
of
inertia
of
the
fan
,
and
a second tilt stiffness ratio of:
a
tilt
stiffness
of
the
gearbox
support
the
moment
of
inertia
of
the
fan
is in a range from 4.0×10 4 Nmrad −1 kg −1 mm −2 to 2.7×10 −1 Nmrad −1 kg −1 mm −2 .
8. The gas turbine engine according to claim 1 , wherein the moment of inertia of the fan is in a range from 8.3×10 7 kgmm 2 to 6.5×10 8 kgmm 2 .
9. The gas turbine engine according to claim 1 , wherein either:
a) the plurality of fan blades are formed from a metallic material; or
b) the plurality of fan blades are formed at least partly from an organic matrix composite.
10. The gas turbine engine according to claim 1 , wherein:
the fan shaft connects the output of the gearbox to the fan;
a gearbox output position is defined as a point of connection between the fan shaft and the gearbox;
the fan has an axial centreline;
a fan-gearbox axial distance is defined as an axial distance between an axial position of the gearbox output position and the axial centreline of the fan; and
the fan-gearbox axial distance multiplied by the moment of inertia of the fan is in a range from 1.9×10 7 kgmm 2 m to 6.2×10 8 kgmm 2 m.
11. The gas turbine engine according to claim 1 , wherein:
i) the gearbox has a gear ratio of 3.2 to 4.5; and/or
ii) the gas turbine engine is configured to have a specific thrust from 70 to 90 NKg −1 ; and/or
iii) the gas turbine engine is configured to have a bypass ratio at cruise conditions of 12.5 to 18; and/or
iv) the fan has a fan diameter greater than 240 cm and less than or equal to 380 cm; and/or
v) the mass of the fan is between 150 kg and 250 kg; and/or
vi) the fan has a fan pressure ratio at cruise conditions of between 1.40 and 1.43.
12. 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 receive an input from the core shaft, and output drive to a fan shaft via an output of the gearbox 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 moment of inertia of the fan is in a range from 7.40×10 7 kgmm 2 to 9.00×10 8 kgmm 2 ; and
at least one tilt stiffness to moment of inertia ratio selected from the group consisting of:
a first ratio of:
a
tilt
stiffness
of
the
fan
shaft
at
the
output
of
the
gearbox
the
moment
of
inertia
of
the
fan
,
and
a second ratio of:
a
tilt
stiffness
of
the
gearbox
support
the
moment
of
inertia
of
the
fan
is in a range from 4.0×10 4 Nmrad −1 kg −1 mm −2 to 2.7×10 −1 Nmrad −1 kg −1 mm 2 .
13. The gas turbine engine according to claim 12 , wherein the at least one tilt stiffness to moment of inertia ratio is in a range from 1.0×10 −3 Nmrad −1 kg −1 mm −2 to 0.1 Nmrad −1 kg −1 mm −2 .
14. The gas turbine engine according to claim 12 , wherein:
a) the first ratio of the tilt stiffness of the fan shaft at the output of the gearbox to the moment of inertia of the fan is in a range from 1.0×10 −3 Nmrad −1 kg −1 mm −2 to 0.1 Nmrad −1 kg −1 mm −2 ; and/or
b) the second ratio of the tilt stiffness of the gearbox support to the moment of inertia of the fan is in a range from 1.0×10 −3 Nmrad −1 kg −1 mm-2 to 7.0×10 2 Nmrad −1 kg −1 mm −2 .
15. The gas turbine engine according to claim 12 , wherein:
a) the tilt stiffness of the fan shaft at the output of the gearbox is in a range from 7.00×10 4 Nm/rad to 7.00×10 7 Nm/rad; and/or
b) 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.
16. The gas turbine engine according to claim 12 , wherein at least one radial bending stiffness to moment of inertia ratio selected from the group consisting of:
a first ratio of:
a
radial
bending
stiffness
of
the
fan
shaft
at
the
output
of
the
gearbox
the
moment
of
inertia
of
the
fan
a second ratio of:
a
radial
bending
stiffness
of
the
gearbox
support
the
moment
of
inertia
of
the
fan
is in range from 2.5×10 −2 Nkg −1 m −1 mm −2 to 6.0 Nkg −1 m −1 mm −2 .
17. The gas turbine engine according to claim 12 , wherein:
a) a diameter of the fan is in a range from 240 cm to 28 cm, and the at least one tilt stiffness to moment of inertia ratio is in a range from 1.0×10 −3 Nmrad −1 kg −1 mm −2 to 1.45×10 −2 Nmrad −1 kg −1 mm −2 ; or
a) the diameter of the fan is in a range from 330 cm to 380 cm, and the at least one tilt stiffness to moment of inertia ratio is in a range from 4.0×10 4 Nmrad −1 kg −1 mm −2 to 3.0×10 −2 Nmrad −1 kg −1 mm −2 .
18. The gas turbine engine according to claim 12 , wherein at least one product selected from the group consisting of:
a first product of:
(the tilt stiffness of the fan shaft at the output of the gearbox)×(the moment of inertia of the fan), and
a second product of:
(the tilt stiffness of the gearbox support)×(the moment of inertia of the fan)
is in a range from 3.0×10 12 Nmrad −1 kgmm 2 to 6.0×10 16 Nmrad −1 kgmm 2 .
19. A method of operating a gas turbine engine for an aircraft, the gas turbine engine 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, the fan having a moment of inertia in a range from 7.40×10 7 kgmm 2 to 9.00×10 8 kgmm 2 ;
a gearbox that is configured to receive an input from the core shaft, and output drive to a fan shaft via an output of the gearbox 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) at least one radial bending stiffness to moment of inertia ratio selected from the group consisting of:
i) a first ratio of:
a
radial
bending
stiffness
of
the
fan
shaft
at
the
output
of
the
gearbox
the
moment
of
inertia
of
the
fan
,
and
ii) a second ratio of:
a
radial
bending
stiffness
of
the
fan
shaft
at
the
output
of
the
gearbox
the
moment
of
inertia
of
the
fan
,
and
is in a range from 2.5×10 −2 Nkg −1 m −1 mm −2 to 6.0 Nkg −1 m −1 mm −2 ; and/or
b) at least one tilt stiffness to moment of inertia ratio selected from the group consisting of:
i) a first ratio of:
a
tilt
stiffness
of
the
fan
shaft
at
the
output
of
the
gearbox
the
moment
of
inertia
of
the
fan
,
and
ii) a second ratio of:
a
tilt
stiffness
of
the
gearbox
support
the
moment
of
inertia
of
the
fan
is in a range from 4.0×10 4 Nmrad −1 kg −1 mm −2 to 2.7×10 1 Nmrad −1 kg −1 mm −2 ,
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:
i) in a range from 10,000 Nm to 50,000 Nm at cruise; and/or
ii) in a range from 28,000 Nm to 135,000 Nm at max-take off conditions.