Turbulent mixing of a passive scalar in confined multiple jet flows of a micro combustor

The turbulent mixing characteristics of multiple jet flows in a micro can type combustor are investigated by means of large eddy simulation (LES). The micro combustor can be used for a micro gas turbine which is hybridized with solid oxide fuel cell. Attention is paid for a micro combustor having a circular disk baffle plate with a fuel injection nozzle in the center and oxidant injection holes allocated annularly. Downstream the baffle plate, a complex flow is produced from the interaction of multiple jet flows and study is made for three different configurations of the baffle plates resulting in different mixing pattern. From the results, it is substantiated that the turbulent mixing is promoted by complex flow fields caused by the jet flows and large vortical flow regions in the micro combustor. This is effective to accelerate the slow mixing between fuel and oxidant suffering from low Reynolds number in such a small combustor. In particular, the vortical flow region formed downstream the fuel jet core region plays an important role for rapid mixing coupled with another flow recirculation region. Discussion is made for the instantaneous and time and space averaged flow and passive scalar quantities which show peculiar turbulent flow and mixing characteristics corresponding to the different flow structures for each baffle plate shapes, respectively.