The effect of moisture content on the pyrolysis and gas-phase ignition of live fuels is investigated. Live fuels contain moisture content (dry basis) in the range of 30-200%. Here the fuel is modeled as a thin cellulosic material that is subjected to radiative heating on one side. The solid fuel has a dimensions of a typical Manzanita leaf. The coupled Gpyro3D/FDS model (Lautenberger, 2014) that simulates both solid phase thermal degradation and gas phase combustion was used. In addition, a five-step extended Broido-Shafizadeh reaction model that accounts for thermal degradation, moisture evaporation, and pyrolysis of cellulose was incorporated in Gpyro3D. The solid-phase model was initially validated against Blasi (1994) and a thermo-gravimetric analysis experiment (Reed and Posey, 1980). Subsequently, the coupled Gpyro3D/FDS model was utilized to study the ignition of cellulosic fuel with an initial, uniformly distributed moisture content of 40% and 80%. The case with lower moisture content underwent pyrolysis and ignition earlier in time, resulting in higher solid and gas phase temperatures. Furthermore, a local moisture evaporation and temperature rise were observed in both cases and a significant amount of moisture remained in the sample during ignition. The numerical results suggested that moisture content not only affected the gas phase combustion and ignition time of the fuel, but also influenced the pyrolysis process.
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