Diffusion-premix nozzle for a gas turbine combustor and related method

In a gas turbine, a plurality of combustors, each having a plurality of fuel nozzles arranged about a longitudinal axis of the combustor, and a combustion zone, each fuel nozzle having a diffusion gas passage connected to a diffusion gas inlet and a premix gas passage connected to a premix gas inlet, the premix gas passage communicating with a plurality of premix fuel injectors extending radially away from said premix gas passage, and located within a dedicated premix tube adapted to mix premix fuel and combustion air prior to entry into the combustion zone located downstream of the premix tube, and wherein said diffusion gas passage terminates at a forward discharge end of said fuel nozzle downstream of said premix fuel injectors but within said dedicated premix tube, and wherein said plurality of premix fuel injectors are located upstream of said forward end;

• and further wherein said diffusion gas passage is defined in part by a forward wall portion of the fuel nozzle, said forward wall portion formed with a circumferential array of regions of lesser wall thickness than remaining regions of said forward wall portion.

A method of minimizing flashback damage in a gas turbine combustor which includes a plurality of combustors, each of which includes a premix zone, a combustion zone and a plurality of nozzles, each nozzle having a diffusion gas passage connected to a diffusion gas inlet and a premix gas passage connected to a premix gas inlet, the premix gas passage communicating with a plurality of premix fuel injectors extending radially away from said premix gas passage, and located within a dedicated premix tube adapted to mix premix fuel and combustion air prior to entry into the single combustion zone located downstream of the premix tube, and wherein said diffusion gas passage terminates at a forward discharge end of said fuel nozzle downstream of said premix fuel injectors but within said dedicated premix tube, and wherein said premix fuel injectors are located upstream of said forward end;

• and further wherein said diffusion gas passage is defined in part by a forward wall portion of the fuel nozzle, the method including the step of providing weakened regions in a wall partially defining said premix passage so that, in the event of a flashback of flame into the premix zone, said weakened regions will burn through, allowing a substantial portion of premix fuel to bypass said premix fuel injectors, such that any premix fuel exiting said injectors is insufficient to sustain a flame.

In a fuel nozzle for a gas turbine combustor having a nozzle body defining a fuel-air passage and an injector in fluid communication with said passage for injecting a fuel-air mixture from said passage into a burning zone, the improvement comprising a weakened region of the nozzle body adapted to burn through in the event of combustion flashback, thereby permitting a portion of said fuel-air mixture to bypass said injector and to exit said nozzle body at said weakened region.