Apparatus and method of operating a gas turbine engine at start-up
A method of operating a gas turbine engine having a turbine and a compressor connected via a shaft, a main fuel supply line for supplying fuel to a combustor that is positioned to release expanding hot gases to the turbine, the engine further including a starter/generator connected to the shaft via a gearbox assembly, the method is characterised the step of during engine start up fuel is circulated in a re-circulating fuel circuit positioned on the main fuel supply line and which has a first fuel/oil heat exchanger, for cooling the oil, and a fuel accumulator.
1. A gas turbine engine comprising:
a turbine;
a compressor connected via a shaft to said turbine;
a main fuel supply line for supplying fuel;
a combustor for receiving said fuel that is positioned to release expanding hot gases to the turbine, a first fuel and oil heat exchanger associated with an engine starter/generator that is connected to the shaft via a gearbox assembly;
the engine is characterised by a re-circulating fuel circuit positioned on the main fuel supply line and that has a second fuel/oil heat exchanger and a fuel accumulator, the re-circulating fuel circuit thereby cooling the oil in the starter/generator via the first fuel and oil heat exchanger.
2. A gas turbine engine as claimed in claim 1 wherein the second fuel/oil heat exchanger is fluidly connected to an engine oil circuit.
3. A gas turbine engine as claimed in claim 1 wherein the first fuel/oil heater exchanger is fluidly connected to the starter/generator.
4. A gas turbine engine as claimed in claim 1 wherein the circuit comprises a fuel filter.
5. A gas turbine engine as claimed in claim 4 wherein fuel filter is positioned between the second fuel/oil heat exchanger and the combustor.
6. A gas turbine engine as claimed in claim 1 wherein the circuit comprises a shut off valve that is provided to stop fuel return flow during normal engine running.
7. A method of operating a gas turbine engine having a turbine and a compressor connected via a shaft, a main fuel supply line for supplying fuel to a combustor that is positioned to release expanding hot gases to the turbine, the engine further having a starter/generator connected to the shaft via a gearbox assembly, a first fuel/oil heat exchanger for cooling the oil in the starter/generator oil circuit, and a fuel accumulator, the method comprising the steps of:
initiating engine start-up;
circulating fuel in a re-circulating fuel circuit positioned on the main fuel supply line.
8. A method of operating a gas turbine engine as claimed in claim 7 wherein a further step comprises supplying the cooled fuel to the starter/generator for cooling.