Soot, Temperature, and OH Measurements in a Unsteady Counterflow Diffusion Flame

摘要

The objective of this research project was to increase the current level of understanding of the interaction between an unsteady hydrodynamic field and the chemical kinetics in a laminar diffusion flamelet. A steady counterflow diffusion flame burner has been modified to allow periodic oscillations of the input velocity. Laser diagnostics were used to quantitatively measure soot volume fraction in an unsteady propane-air counterflow diffusion flame. The instantaneous strain rate at global flame extinction for a propane-air flame has been measured as a function of steady strain and both amplitude and frequency of the unsteady component Two component LDV was used to measure the velocities allowing determination of the true strain rate. The phase lag between velocity and strain rate was quantified. Low frequency oscillations in the reactant flow rates increased net soot production by as much as 6 times over the steady flame. At low initial strain rates, high frequency oscillations reduce the maximum soot volume fraction by as much as 90% of the steady flame soot concentration. At high initial strain rates, soot production was insensitive to high frequency oscillations.