The Role of Moisture on Combustion of Pyrolysis Gases in Wildland Fires

The role of water vapor, originated from the moisture content in vegetation, on the combustion process was investigated via simulating an opposed diffusion flame and a laminar premixed flame with pyrolysis gases as the fuel and air as the oxidizer. The fuel was mixed with water vapor, and the simulation was repeated for various water mole fractions. In both of the diffusion and premixed flames, the smaller the water mole fraction, the higher the maximum temperature. No reactions occurred when the water mole fraction was 0.65 or larger in the diffusion flame, and 0.70 or larger in the premixed flame. The maximum energy release rate and the flame speed decreased with the increase of the water mole fraction in the premixed flame. In both flames, O₂ and H were the components that showed dramatic changes with the change of the water mole fraction.