Flame speed measurements at the tip of a slot burner: Effects of flame curvature and hydrodynamic stretch

Abstract

The effects of flame curvature and stretch upon the laminar flame speed are investigated experimentally and compared to theoretical predictions. The flame speed at the tip and side of a slot burner is measured using particle tracking velocimetry. Temperatures are measured using Rayleigh scattering. Flame tip curvatures are measured using direct flame photography. For a range of mean exit velocities from 1 to 2.5 m/s and a diffusionally neutral mixture, the flame speed at the tip is found to exceed that at the side by a factor as high as 6.25. The flame speed ratio is found to depend linearly upon the hydrodynamic stretch factor as predicted by the analysis of Matalon and Matkowsky. Equivalently, the flame speed ratio is found to increase nonlinearly with the flame curvature. Comparison with published results from a cylindrical burner shows similar trends.