The authority of an active combustion instability control system was improved by increasing the degree of mixing between a modulated gaseous fuel source and the remainder of the premixed reactants in a low-emissions combustor. Non-reacting acetone PLIF measurements were used to assess the mixedness of various fuel injection configurations, in both time-averaged and phase-locked modes. These configurations were also evaluated in combustion tests in which the authority of the actuator and the ability of the control system to attenuate the instability were measured. The results indicated that both control authority and emissions performance are tied directly to the ability to achieve temporal control over the spatially-averaged fuel/air ratio leaving the premixer at any point in time while simultaneously maintaining the high spatial uniformity of this mixture. The cold-flow diagnostic techniques were proven to be an effective and low-cost method for screening fuel injection concepts.

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