Turbo machine and method for operating such turbo machine
A turbo machine, such as a gas turbine, includes a rotor, which rotates about a horizontal machine axis, and which is enclosed by a coaxial enclosure. The turbo machine includes a metal casing, whereby an electrical heating system is provided on the lower half of the metal casing. A safe operation is achieved by having the heating system configured as a redundant system.
1. A turbo machine configured as a gas turbine, comprising:
a rotor, which rotates about a horizontal machine axis, and which is enclosed by a coaxial enclosure having a metal casing;
an electrical heating system provided on the lower half of said metal casing, wherein said heating system is configured as a redundant system, wherein said heating system comprises at least one electrical heating module with two similar redundant lines running in parallel alongside each other, and wherein said heating system includes at least one heating cable and measuring means for measuring temperatures and/or electrical properties within said heating system including at least a temperature of said at least one heating cable.
2. The turbo machine as claimed in claim 1 , wherein said at least one heating module is connected to a power supply unit such that either each of said redundant lines is supplied with 50% of the electrical power supplied to said heating module from the power supply unit or only one of said redundant lines is supplied with 100% of said electrical power.
3. The turbo machine as claimed in claim 1 , wherein said measuring means is configured as a redundant measuring means.
4. The turbo machine as claimed in claim 3 , wherein said at least one heating cable is attached to said metal casing, and said measuring means comprises at least one thermocouple box attached to said at least one heating cable to measure the temperature of said at least one heating cable.
5. The turbo machine as claimed in claim 4 , wherein said at least one thermocouple box encloses a section of said at least one heating cable at a predetermined place of said at least one heating cable, that said at least one heating cable runs through said thermocouple box between an upper part and a lower part of said thermocouple box, and that at least three thermocouples for measuring the temperature of said thermocouple box are attached to said thermocouple box.
6. A method for operating a turbo machine according to claim 5 , wherein said at least one thermocouple box creates an artificial hot spot at said heating cable, and that said three thermocouples attached to said thermocouple box are evaluated by a control unit with a 2-out-of-3 logic.
7. The turbo machine as claimed in claim 4 , wherein said at least one thermocouple box is covered with a thermal insulation in order to increase the temperature of the thermocouple box.
8. The turbo machine as claimed in claim 1 , wherein said at least one heating cable, which is attached to said metal casing by means of metal holding strips.
9. The turbo machine as claimed in claim 8 , wherein said metal holding strips are placed between said metal casing and said at least one heating cable and hold said heating cable by means of hook elements.
10. The turbo machine as claimed in claim 9 , wherein said at least one heating cable is provided with a bend between two distant holdings strips holding said heating cable.
11. The turbo machine as claimed in claim 1 , wherein a plurality of heating modules are symmetrically arranged on said metal casing with regard to a vertical symmetry plane through the machine axis, and that said heating modules are individually and controllably supplied with electric power by means of a power supply unit.
12. A method for operating a turbo machine according to claim 11 , wherein a heating module on one side of said vertical symmetry plane is turned off when its symmetric counterpart on the other side of said vertical symmetry plane fails.
13. A method for operating a turbo machine according to claim 11 , wherein in case of an asymmetric cool-down with respect to said vertical symmetry plane the heating system is powered asymmetrically to counter said temperature asymmetry.
14. A method for operating a turbo machine according to claim 1 , wherein a control unit within said heating system decides on the electrical power supplied to said heating system based on measurements of the temperature of the metal casing and/or the clearance of the machine and/or electric parameters of the heating system and/or operating parameters of the turbo machine.