Dynamic Flame Structure in a Low NO_x Premixed Combustor

Flame emittance images phase-locked to acoustic fluctuations have been acquired to study flame structure variations in lean premixed gas-fueled swirl-stabilized combustor systems used in industrial gas turbines. Images have been acquired through a specially-designed optical probe that makes use of the limited optical access typical of these combustors. A number of observations appear to be consistent under widely varying operating conditions. While flame stabilization was anticipated in the central vortex and outer recirculation zone of the nozzle, no optical emissions have been observed in the outer region. Oscillations in the flame emittance appear to be primarily in intensity rather than structure suggesting that the major contributor to acoustic coupling may be equivalence ratio variations rather than the motions of large scale fluid structures.