An Experimental-Numerical Investigation of Unsteady Partially Premixed Flames

University Of Illinois At Chicago, Chicago IL

Investigators

Abstract

This is study of the structure and dynamics of unsteady, partially premixed flames including liftoff and stabilization mechanisms associated with triple flames and the effects of stretch and curvature on flame structure and stability. The experimental effort uses established nonintrusive optical diagnostics such as laser Doppler velocimetry, particle image velocimetry, high-speed videography, C2* radical imaging, and holographic interferometry. Numerical simulations of the flames employ higher-order time-accurate multidimensional algorithms incorporating detailed chemical kinetics models for oxidation of such fuels as hydrogen, methane, and n-heptane. Hydrodynamic stretch effects on flames are studied in a counterflow burner, while the contribution of curvature to stretch is investigated in a slot burner. Instabilities in triple flames induced by buoyancy or shear are investigated; simulations suggest that these occur as functions of flow rate. Computationally, a conserved scalar approach based on a modified mixture fraction is used to characterize state relationships.