Patent ID: 7370478

Claim:
A method of controlling a gas combustor ( 1 ) of a gas turbine; the gas combustor having an axis ( 2 ) and comprising: a central diffusion burner ( 4 ) comprising a nozzle ( 6 ) extending along said axis ( 2 ) and defining a first channel ( 9 ) radially outwards with respect to said axis ( 2 ), conducting an air stream (F 1 ), and housing an ignition device ( 10 ); a second channel ( 11 ) extending along said axis ( 2 ); and a third channel ( 12 ) interposed radially between said first and said second channel ( 9 , 11 ) and separate from said first and said second channel ( 9 , 11 ); and a peripheral premix burner ( 5 ) surrounding said nozzle ( 6 ); the method comprising a first step of starting up said gas turbine, wherein said peripheral premix burner ( 5 ) is off; and, once a given power threshold (C) is exceeded, a second step wherein said peripheral premix burner ( 5 ) is on; said first step comprising the operations of igniting a diffusion flame at the start of said first step, and of feeding a fuel gas stream (F 2 ) along said third channel ( 12 ); during said second step a pilot diffusion flame being held by continuing to feed the fuel gas stream (F 2 ) along said third channel ( 12 ), and by reducing gas flow of said fuel gas stream (F 2 ) at the start of said second step with respect to gas flow (P 1 ) at said first step and to a value greater than zero (P 2 ); characterized in that said first step is carried out by the pilot diffusion flame only up until the start of the second step; and in that part of said fuel gas stream (F 2 ) is diverted from said third channel ( 12 ) to said ignition device ( 10 ) to ignite said pilot diffusion flame at the start of said first step.