Modeling of CO emissions in multi-burner systems with fuel staging

This work presents a novel strategy to numerically predict CO emissions in gas turbines that operate under part-load conditions employing fuel-staging concepts. In multi-burner systems, fuel can be redistributed to solely run a fraction of the available burners. The situation of active burners interacting with air from adjacent cold burners may lead to quenching effects. Our group recently published a flamelet-based combustion model for low-reactive conditions. Furthermore, a model was proposed for the prediction of CO beyond the assumption of thin reaction zones. These models are adopted in this work and further extended in order to capture quenching. All models are implemented and applied to a simple geometry for the purpose of demonstrating basic mechanisms that are relevant for fuel-staged gas turbines operating at part load conditions. Furthermore, validation is performed in a silo combustor that comprises 37 burners. Here, burner groups are switched off during part load, leading to intense interaction between hot and cold burners. Major improvement in comparison to CO predictions from the flamelet-based combustion model is achieved. It is demonstrated that the model is able to predict the correct values of global CO emissions. Furthermore, the models capacity of handling fuel-staging mechanisms like the CO drop during a burner switch-off event is shown.