Combustion Characteristics of Bluff-Body Turbulent Swirling Flames with Coaxial Air Microjet

The interaction between the coaxial air microjet structure and the swirling flow is investigated numerically based on the nonpremixed bluff body stabilized swirling SM1 flame. The effects of microjet velocity and swirl number on flame combustion characteristics are analyzed. The modified standard k-epsilon model and the realizable k-epsilon model are considered for the turbulent model using FLUENT software. The flamelet model is used with the GRI 2.11 detailed kinetic mechanism. In addition, the discrete ordinate model and the weighted-sum-of-gray-gases model are used together to deal with the radiative heat transfer in the combustion process. Results of the modified standard k-epsilon model are in better agreement with the experimental data than the realizable k-epsilon model. Results show that the inner flame generates due to the existence of a microjet configuration. High microjet velocity (such as 50 m/s) can reduce the soot formation and keep the inner flame high temperature region away from the microjet nozzle. The structure of the inner flame depends on the microjet velocity and is independent of the swirl number. Swirl number increases from 0.3 to 0.6, the primary peak temperature is enhanced by 48 K, and the peak soot volume fraction is increased by 49% along the axis centerline.