Behavior of Flame Spread Downward over Thick Wood Sheets and Heat Transfer Analysis

Abstract

To investigate the flame spreading mechanism over charring materials under natural convection, wood sheets from 0.9 to 3 mm thickness have been chosen. The variation of mean flame spread velocity V with thickness δ is measured. Typical flame shapes over the wood surfaces are recorded using CCD. The temperature fields in the gas phase are examined by a set of fine thermocouples. On the basis of the results, the relative contributions of local heat transfer modes ahead of the pyrolysis front have been evaluated. It is found that heat conduction through solid phase increases notably with δ. A flame spreading model coupled with a pyrolysis structure is proposed.