An Experimental Investigation of Scalar Mixing and Flame Structure of a Partially Premixed Flame

Abstract

ABSTRACT Experimental investigation of a partially premixed flame stabilized in a combination of bluff body and swirling flowfields is reported. Simultaneous measurement of 2D fuel distribution (Acetone-PLIF) and flame structure (OH-PLIF) are performed with varying thermal power. Two flame stabilization modes – swirl influenced conical shaped, and, bluff-body influenced toroidally shaped – are observed in OH chemiluminescence measurements. Upstream propagation of the flame with decreasing global equivalence ratios is noticed, with the flame being transferred from the swirl-influenced to the bluff body influenced flowfields. The average flame stabilization location in both modes is found to be approximately close to the stoichiometric surface with the flame base oriented toward the inner shear layer. The degree of fuel/air mixing calculated from Acetone PLIF images by determining the unmixedness shows that the stabilization locations overlap with regions of perfect mixing. The swirl-influenced flames are stabilized at the farthest distance from the burner exit, with the flame base closer to the stoichiometric surface, whereas the bluff body influenced flames oriented along the stoichiometric surface in the inner shear layer.