Characterizing burning behavior of biomass fuels with discrete distribution

Abstract

Discrete distribution of biomass fuels is an important configuration for the implication of wildland fire. In this study, flame spread and burning behaviors were examined by designing 90 groups of birch array geometries. Five inclination angles (denoted by θ, 15°−90°), three spacings (S, 3 mm, 6 mm, and 9 mm), and five column numbers (n, 3–11) were varied. Flame spread behavior is characterized by three regimes, a steady fire (regime Ⅰ), a growing fire (regime Ⅱ), and a fast-developed fire (regime III). Correlations of determining flame spread regime are proposed. Under these regimes, mass loss rate per unit area (ṁ″) has a power-law dependency on porosity (φ), where the power-law index increases from regime Ⅰ, Ⅱ to regime III. In the regime III, ṁ″ is independent of φ when φ > 1.6 mm. The three spread regimes are attributed to the transition of the controlling mechanism from radiation to convection dominance. Moreover, by introducing the total mass transfer number BT, the influence of the controlling mechanism is classified into two regions, radiation dominance (region I) and convective dominance (region II), in which the three flame spread regimes are evaluated.