Numerical analysis of the effect of fuel load on downward flame spread

Abstract

This paper performs parameter studies varying sample thickness and volume density to investigate the effect of surface density on downward flame spread using Direct Numerical Simulation (DNS). Surface density is a significant property that affects fuel loads on the fuel surface greatly. The results reveal that all the thin fuels of 70 – 180 g/m2 attain a steady state, which means that the flame base and pyrolysis front move downstream with the same rate. Moreover, the propagating rates of the flame base and pyrolysis front decrease with the increasing surface density. Subsequently, the flame contour and flame heat feedback in preheated region are studied. Along the flame base downstream, dimensionless flame standoff distance grows gradually till a peak reaches at appropriately (Z-Zb )/Zf of 0.23, and then is reduced to a minimum near the flame front. Radiative heat flux occupies the dominant position upstream the flame base, and its distribution with normalized space (Z-Zb )/Zf is established. The present paper together with previous works can provide further understanding on the effect of fuel loads on downward flame spread.