Gas turbine engine with electric machines
A gas turbine engine for an aircraft includes, in axial flow sequence, a compressor module, a combustor module, and a turbine module, with a first electric machine being rotationally connected to the turbine module. The first electrical machine is configured to generate a total electrical power P EM1 (W), and the gas turbine engine is configured to generate a total shaft power P SHAFT (W); and a ratio R of: R = ( Total Shaft Power = P SHAFT ) ( Total Electrical Power Generated = P EM 1 ) is in a range of between 0.005 and 0.020.
1. A gas turbine engine for an aircraft, the gas turbine engine comprising;
an outer housing enclosing, in axial flow sequence, a fan assembly, a compressor module, a combustor module, and a turbine module, and
a first electric machine being rotationally connected to the turbine module, the first electrical machine being configured to generate a total electrical power P EM1 (W), and the gas turbine engine being configured to generate a total shaft power P SHAFT (W),
wherein, a ratio R of:
R
=
(
Total
Electrical
Power
Generated
=
P
EM
1
)
(
Total
Shaft
Power
=
P
SHAFT
)
is in a range of between 0.005 and 0.020,
wherein the gas turbine engine further comprises a second electric machine rotationally connected to the fan assembly via a fan shaft, the second electrical machine being configured to generate an electrical power P EM2 (W),
wherein the second electric machine is positioned within the outer housing and upstream of the fan assembly, such that the fan shaft is disposed between the second electric machine and the fan assembly, and
wherein, a ratio R of:
=
(
Total
Electrical
Power
Generated
=
P
EM
1
+
P
EM
2
)
(
Total
Shaft
Power
=
P
SHAFT
)
is in a range of between 0.005 and 0.035.
2. The gas turbine engine as claimed in claim 1 , the fan assembly comprising a plurality of fan blades extending radially from a hub, the plurality of fan blades defining a fan diameter (D FAN ), and wherein the fan diameter D FAN is within the range of 0.3 m to 1.4 m.
3. The gas turbine engine as claimed in claim 1 , wherein the first electric machine is positioned axially between the fan assembly and the compressor module.
4. The gas turbine engine as claimed in claim 1 , the gas turbine engine further comprising an outer casing, the outer casing enclosing the sequential arrangement of the fan assembly, the compressor module, the combustor module, and the turbine module, an annular bypass duct being defined between the outer casing and the sequential arrangement of the compressor module, the combustor module, and the turbine module, a bypass ratio being defined as a ratio of a mass air flow rate through the bypass duct to a mass air flow rate through the sequential arrangement of modules, and wherein the bypass ratio is less than 4.0.
5. The gas turbine engine as claimed in claim 1 , wherein the fan assembly has two or more fan stages, at least one of the fan stages comprising a plurality of fan blades defining a fan diameter D FAN .
6. The gas turbine engine as claimed in claim 1 , wherein at least one of the first electric machine and a second electric machine, comprises an axial length L EM and a diameter D EM , and wherein a ratio of the axial length to the diameter (L EM /D EM ) for the respective electric machine is in a range between 0.5 to 2.0.
7. A method of operating a gas turbine engine for an aircraft the method comprising the steps of:
(i) providing a gas turbine engine, the gas turbine engine comprising an outer housing enclosing, in axial flow sequence, a fan assembly, a compressor module, a combustor module, and a turbine module;
(ii) providing a first electric machine positioned downstream of the fan assembly and rotationally connected to the turbine module;
(iii) providing a second electric machine rotationally connected to the fan assembly via a fan shaft, the second electrical machine being configured to generate an electrical power P EM2 (W); and
(iv) operating the gas turbine engine at a full power condition in which the gas turbine engine generates a total shaft power P SHAFT (W), the first electric machine generates an electrical power P EM1 (W), and the second electric machine generates an electrical power P EM2 (W), and where a ratio R of:
R
=
(
Total
Electrical
Power
Generated
=
P
EM
1
)
(
Total
Shaft
Power
=
P
SHAFT
)
is in a range of between 0.005 and 0.020,
wherein the second electric machine is positioned within the outer housing and upstream of the fan assembly, such that the fan shaft is disposed between the second electric machine and the fan assembly, and
where a ratio R of:
=
(
Total
Electrical
Power
Generated
=
P
EM
1
+
P
EM
2
)
(
Total
Shaft
Power
=
P
SHAFT
)
is in a range of between 0.005 and 0.035.