ID#: 40
Abstract Title: Surface Density Measurements for Freely-Propagating Premixed Turbulent Flames at Various Lewis Numbers.
Session Title: Premixed Turbulent Flames I
Session Date: 7/30/01
Session Start Time: 8:55 AM
Contributing Author: Renou, B.
Organization: LAME-CORIA UMR 6614 CNRS
Country: France
Authors: B. Renou, A. Mura, E. Samson, A. Boukhalfa
Short Abstract: The flame surface density for non-stationary premixed turbulent flames is measured for different fuel/air mixtures (methane, propane and hydrogen/air) in order to evaluate the influence of the Lewis number. These mixtures are separately spark-ignited in a vertical wind tunnel. The expanding flame freely propagates in a grid-generated decaying isotropic turbulent flow. Two-dimensional laser sheet tomography technique is used to characterize the instantaneous flame front position, from ignition to fully development stages. The flame surface density evolution is obtained from the conditional gradient of the progress variable with 150 flames for each propagation time. The global profiles of the flame surface density are symmetrical about a peak value and globally present a parabolic trend. The maximum of flame surface density decreases as the flame propagates. The evolutions of this maximum are identical for all the Lewis number used in this experimental work, for two levels of turbulence. This result indicates that the effect of the Lewis number on the flame surface density, as observed in these experimental results, is primarily an effect on turbulent flame thickness. The maximum flame surface density presents also a slight influence with u'/SL, for the three fuel/air mixtures. For each propagation time, the maximum of fame surface density decreases for an increasing of the turbulence level u'/SL (at constant laminar flame speed SL), whatever the variation of the integral length scale. These results are then discussed and compared with previous experimental and numerical data available in the literature.