Electrical generation arrangement for an aircraft
This invention relates to a multi-spool gas turbine engine, including: a first generator for providing electrical power to an electrical system, the generator being driveably connected to a first spool; a second generator for providing electrical power to the electrical system, the generator being driveably connected to a second spool; a disconnection device for disconnecting the second generator from the second spool; and, a controller configured to selectively operate the disconnection device under predetermined powered engine conditions.
1. A multi-spool gas turbine engine, comprising:
a first generator for providing electrical power to an electrical system, the first generator being driveably connected to a first spool;
a second generator for providing electrical power to the electrical system, the second generator being driveably connected to a second spool;
a disconnection device configured to disconnect the second generator from the second spool wherein the second generator is also not connected to the first spool, and,
comprising:
a controller which is configured to selectively operate the disconnection device under predetermined powered engine conditions while the engine is running, the predetermined powered engine conditions corresponding to a rotational speed of the second spool or second generator.
2. An engine as claimed in claim 1 , wherein the controller is configured to determine the speed of rotation of the second spool or second generator from one or more of: a spool speed, a rate of change of spool speed, a rate of fuel consumption, the overall engine pressure ratio, a predetermined schedule of operation.
3. An engine as claimed in claim 1 , further comprising a sensing arrangement to sense the speed of rotation of the second spool or second generator, wherein the controller is configured to disconnect the second generator when the speed of rotation is above at least one predetermined threshold.
4. An aircraft according to claim 3 , wherein the predetermined threshold for the speed of rotation is in a range of 1000 to 3000 rpm.
5. An aircraft according to claim 3 , wherein the predetermined threshold for the speed of rotation is in a range of 400-1000 rpm.
6. An engine as claimed in claim 1 wherein the controller is configured to monitor the rate of change of speed in the spool or rotor of the second generator.
7. An engine as claimed in claim 1 wherein the controller is further configured to connect the disconnection device under windmill conditions or to start the engine.
8. An engine as claimed in claim 1 wherein the disconnection device is a clutch.
9. An engine as claimed in claim 1 further comprising a second disconnection device.
10. An engine as claimed in claim 1 wherein the second disconnection device is an emergency shear.
11. An engine as claimed in claim 1 wherein either or both of the first and second generator are arranged to transfer power between the first and second spools during use.
12. An engine as claimed in claim 1 wherein the second spool is the low pressure spool or intermediate pressure spool.
13. An engine as claimed in claim 1 wherein the second generator is embedded within a core of the engine.
14. An aircraft having an engine as claimed in claim 1 wherein the aircraft includes energy storage which is electrically connectable to at least one of the first and second generators.
15. An aircraft as claimed in claim 1 , comprising at least one power electronic module which is configured to control the electrical output of one or both of the first and second generators.
16. An engine as claimed in claim 1 , further comprising a sensing arrangement to sense the speed of rotation of the second spool or second generator, wherein the controller is configured to disconnect the second generator when the speed of rotation is below at least one predetermined threshold.
17. A method of supplying electrical power from a multi-spool gas turbine engine having a first generator for providing electrical power to an electrical system, the first generator being driveably connected to a first spool; a second generator for providing electrical power to the electrical system, the second generator being driveably connected to a second spool; a disconnection device configured to disconnect the second generator from the second spool wherein the second generator is also not connected to the first spool; and, a controller configured to selectively operate the disconnection device under predetermined powered engine conditions while the engine is running, the method comprising the steps of:
generating power with the first generator;
generating power with the second generator;
determining whether the engine is operating within predetermined powered operating conditions; and
activating the disconnection mechanism when the engine is not operating within the predetermined powered engine conditions,
wherein the predetermined powered operating conditions correspond to a speed of rotation of the second spool or second generator.
18. A method as claimed in claim 17 , wherein determining whether the engine is operating within predetermined powered operating conditions includes monitoring one or more of: a spool speed, a rate of change of spool speed, a rate of fuel consumption and a predetermined schedule of operation.