Large-eddy simulation of a turbulent sooting flame in a swirling combustor

Large eddy simulation has gained prominence in the simulation of complex reacting flows, especially in the computational modeling of practical combustors. In this work, the use of LES for simulating soot formation in a model aircraft combustor is explored. For this purpose, the DLR swirl combustor that emulates the rich-quench-lean (RQL) configuration using secondary oxidation air injection is used. To begin with, simulations of non-reacting swirling flow are compared with experimental data and found to agree reasonably well. In particular, the mean flow statistics are reproduced quite accurately. LES of the sooting case shows that simulations overpredict soot volume fraction considerably but qualitatively capture the variation in soot evolution when the secondary injection of air is turned off. The simulations indicate a weaker jet trajectory that dissipates faster than in experiments, which leads to ignition and flame stabilization at shorter distance from the inlet. It is also found that the intermittency of soot varies considerably between the cases, with the recirculation zone showing highly intermittent soot structures when the secondary air injection is present.