Large Eddy Simulation of a 100 kWth swirling oxy-coal furnace

Abstract Large Eddy Simulation (LES) has been applied to the swirling 100 kW th OXYCOAL-AC test facility of Aachen University. A set of models to represent devolatilisation, volatile combustion, char combustion and radiation for oxy-coal combustion in an LES framework has been implemented and tested. A qualitative analysis of the flow behaviour and the overall coal combustion processes occurring within the furnace was made. The LES results for the flow field were compared to axial and tangential mean velocity measurements, showing good agreement, particularly in the upstream regions of the flame. The LES results were also compared to oxygen concentrations (vol.) and gas temperature. Overall good agreement was observed in the upstream central regions of the flame, whilst downstream the LES overestimated the combustion rates. It was also found that the recirculation zones are sensitive to char combustion, not just to the rate of devolatilisation as one might expect. An interesting problem occured in the prediction of the velocity profiles, for which the measurements were taken based on coal-particles, so that the outer-most stream remained invisible in the experiments (but not the LES), due to being free from particles. The results show the potential of using LES for more complex oxy-coal combustion burners and opens the way for applications to industrial furnaces.