Effects of altitude and sample width on the characteristics of horizontal flame spread over wood sheets

Abstract

To explore the effects of altitude and sample width on the burning characteristics of wood, a series of experiments are carried out at two different altitudes with varying widths (W) of thin wood sheets. Flame size and flame spread rate are measured over a range of sample widths from 2cm to 12cm. At both altitudes, the width effects on both the dimensionless flame height (Hf/W) and the spread rate are analyzed. The dimensionless flame heights at both altitudes show negative power law relationships with the sample width, and the decline at a low altitude (50m, Hefei) is much smaller than that at a high altitude (3658m, Lhasa). The spread rate curves at both altitudes contain a turning point: Before the point, the spread rate decreases with sample width, and after it, the rate increases. Furthermore, heat transfer theory was applied to explain the altitude and sample width effects on the flame spread rate, and the experimental results agree well with the theoretical analysis.