Prediction of ammonia ignition/quenching and emissions of NOx, NH3 and H2 in a non-premixed swirl combustor using the EDC model

The standard Eddy Dissipation Concept model with a modified San Diego mechanism was applied to account for nitrogen chemistry to predict ammonia flame quenching during lean non-premixed combustion in a swirl burner. This study examined the combustion of ammonia- air and ammonia-hydrogen-air flames within a two-stage swirl burner that can be used in a micro gas turbine rated at 50 kW. Various fuel energy inputs at different equivalence ratios were examined regarding flame quenching. The objective of this work was to present a series of experimental results to validate computational fluid dynamics model based on experimental data and determination of best operating conditions from the point of view of emission of pollutants. The results show that the applied San Diego mechanism, which predicts well the flame speeds in lean and stoichiometric conditions, along with the eddy decipation model can accurately predict the flame quenching at various fuel loads and is suitable for CFD simulations due to relatively small number of reactions. The results indicate that the inclusion of the radiation model and heat losses to the surroundings is necessary even for a small size combustor. Excluding the heat loss and radiation was the reason for predicting the quenching limit in much leaner conditions, especially for small fuel loads. This phenomenon was ascribed to the significantly greater impact of heat transfer (reduction in temperature) on the combustion at lower flow rates.