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The device and method are used for heating a central section of a rotor mounted for rotation in a gas turbine engine.

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What is claimed is: 1. A device for heating a central section of a rotor of a gas turbine engine with eddy currents, the device comprising: at least one magnetic field producing element adjacent to an electrical conductive portion on the central section of the rotor of the gas turbine engine; and a

What is claimed is: 1. A device for heating a central section of a rotor of a gas turbine engine with eddy currents, the device comprising: at least one magnetic field producing element adjacent to an electrical conductive portion on the central section of the rotor of the gas turbine engine; and a support structure on which the magnetic field producing element is mounted, the support structure being configured and disposed for a relative rotation with reference to the electrical conductive portion. 2. The device as defined in claim 1, wherein the magnetic field producing element includes a permanent magnet. 3. The device as defined in claim 1, wherein the electrical conductive portion comprises a sleeve made of a material having an electrical conductivity higher than that of a remainder portion of the rotor. 4. The device as defined in claim 3, wherein the sleeve is made of a material including copper. 5. The device as defined in claim 4, wherein the sleeve is connected to the remainder portion of the rotor by an outer sleeve made of a different material. 6. The device as defined in claim 5, wherein the material of the outer sleeve includes steel. 7. The device as defined in claim 1, wherein the support structure and the magnet are positioned inside a shaft independent from the rotor and coaxially positioned therewith. 8. The device as defined in claim 1, wherein the support structure is non-rotating. 9. The device as defined in claim 1, wherein the support structure is made of a material having a Curie temperature, the material being selected to have a Curie temperature associated with a desired shut-down temperature of the device. 10. The device as defined in claim 9, wherein the support structure is made of ferrite. 11. The device as defined in claim 9, further comprising means for selectively heating the support structure above its Curie temperature. 12. A device for heating a central section of a rotor of a gas turbine engine, the device comprising: means for producing a magnetic field adjacent to an electrical conductive portion on the central section of the rotor of the gas turbine engine; and means for moving the magnetic field with reference to the electrical conductive portion of the rotor, thereby generating eddy currents therein and heating the central section of the rotor. 13. The device as defined in claim 12, wherein the means for producing a magnetic field includes a permanent magnet. 14. The device as defined in claim 12, wherein the electrical conductive portion comprises a sleeve made of a material having an electrical conductivity higher than that of a remainder portion of the rotor. 15. The device as defined in claim 14, wherein the sleeve is made of a material including copper. 16. The device as defined in claim 15, wherein the sleeve is connected to the remainder portion of the rotor by an outer sleeve made of a different material. 17. The device as defined in claim 16, wherein the material of the outer sleeve includes steel. 18. The device as defined in claim 12, wherein the means for producing a magnetic field and the means for moving the magnetic field are positioned inside a shaft independent from the rotor and coaxially positioned therewith. 19. The device as defined in claim 12, wherein the means for producing a magnetic field are mounted on a non-rotating support structure, the rotor being moved with reference to the magnetic field. 20. The device as defined in claim 12, further comprising means for providing a shut-down temperature, including a support structure made of a material having a Curie temperature selected to match the desired shut-down temperature. 21. The device as defined in claim 20, wherein the support structure is made of ferrite. 22. The device as defined in claim 20, further comprising means for selectively heating the support structure above its Curie temperature. 23. A method of reducing transient thermal stresses in a gas turbine engine rotor having a central section, the method comprising: producing a moving magnetic field adjacent to an electrical conductive portion on the central section of the rotor; and heating the electrical conductive portion using eddy currents generated in the electrical conductive portion of the rotor by the moving magnetic field. 24. The method as defined in claim 23, wherein said heating is terminated once the engine reaches a desired temperature. 25. The method as defined in claim 24, comprising the step of directing a flow of engine air to a temperature sensing apparatus. 26. The method as defined in claim 23, wherein the step of heating occurs automatically as a result of increasing the speed of the engine upon start-up. 27. The method as defined in claim 23, wherein the step of heating is terminated before takeoff. 28. The method as defined in claim 24, wherein heating is terminated by interrupting said eddy currents. 29. The method as defined in claim 23, further comprising the steps of providing a plurality of magnets to provide said magnetic field and providing a material adjacent to the plurality of magnets for conducting said magnetic field, wherein the material has a Curie point selected to correspond to a desired maximum heating temperature, and wherein the maximum heating temperature is selected below a maximum operating temperature of the engine, and further comprising the step of using engine heat to heat the material above the Curie point to terminate the step of heating. 30. The method as defined in claim 29, wherein the desired maximum heating temperature corresponds to an engine temperature at which transient heating is no longer desired. 31. A gas turbine engine comprising: a rotor supporting blades disposed in a gas path of the engine, the rotor mounted for rotation on a rotor shaft, the rotor having a central bore; a heating apparatus including a plurality of permanent magnets adjacent an electrically conductive material, the electrically conductive material being on the rotor disposed around the bore, the permanent magnets inside the bore, the rotor rotatable independently of the permanent magnets to thereby induce eddy currents in the electrically conductive material when the rotor rotates; a temperature control apparatus configured to interrupt said eddy currents while the rotor is rotating. 32. The gas turbine engine as defined in claim 31, wherein the permanent magnets are disposed on a second shaft disposed concentrically inside said rotor shaft. 33. The gas turbine engine as defined in claim 32, wherein the permanent magnets are disposed inside the second shaft. 34. The gas turbine engine as defined in claim 31, wherein the temperature control apparatus includes a material having a Curie temperature, the material for conducting magnetic flux from the permanent magnets, and wherein the engine in use has an operating temperature and the Curie temperature is less than the operating temperature. 35. The gas turbine engine as defined in claim 31, wherein the temperature control apparatus is in air flow communication with an engine air flow indicative of a temperature of the gas path.