Combustion instabilities are a major challenge in the development of low-emissions premixed gas turbine combustors. The development and demonstration of predictive capabilities for instabilities has progressed considerably. One of the major fundamental mechanisms demonstrated in several instances is the convection of fuel concentration fluctuations from the fuel injector to the reaction zone. A one-dimensional model has been developed which captures this mechanism coupled to solutions for standing acoustic waves. Since many real combustion systems include multiple flow paths for mixing and/or staged fuel injection, the model has been extended to include a parallel acoustic path and two fuel injection locations. Splitting of fuel between two injection positions is a common method to influence combustion dynamics toward a more operable system. A relatively simple model which only partially couples acoustics and heat release was applied to an axially staged combustor and the predictions are compared with the experimental behavior. The results from this model successfully predict the overall dynamics behavior as a function of the fuel split between the two injection locations.

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