Soot formation in co-flowing partially premixed flames over wide range of premixedness

This investigation focuses on the formation of soot in ethylene-air, co-flow, laminar partially premixed flames. A concentric co-flow axisymmetric burner is used to obtain the flame over a wide range of premixedness. The overall stoichiometry (Φoverall) is maintained at 0.8. The thermal power along with the average velocities of the core and annular streams of the burner are held constant. Flame imaging (RGB and bandpass filtered) and laser induced incandescence(LII) is performed to obtain the peak soot locations. In the diffusion and near diffusion cases, soot captured by LII is found to be in the annulus of the flame. With the increase in premixedness, the soot location starts to shift towards the center of the flame. It is observed that the soot formation in the triple flame starts from the rich premixed branch and propagates outward towards the lean branch as the core opens up towards the diffusion flame.