Wildfire plume electrical conductivity

Abstract

Wildfires are weakly ionized gas. The ionization is mainly due to plant’s inorganic ash content species (more especially potassium), that are emitted from thermally decomposing plant structure into the flame during combustion. The amount of ionization in flames with potassium impurities is influenced by both the temperature and the amount potassium impurities in the flame. A numerical experiment was conducted using a local thermal equilibrium-based model to study the influence of inorganic wildfire contents on wildfire electrical conductivity. Simulated very high intensity wildfires (21–90 MW m^-1) were used to quantify steady-state electrical conductivity. Its variation with wildfire plume height is important for high voltage power flashover research. In the simulation, vegetation potassium content was varied from 0.50% to 3.0% on dry weight basis, a reflection of its content in natural vegetation. The model predicted a maximum conductivity of 0.053 mho m^-1 in 90 MW m^-1 crown fire in vegetation with 3.0% potassium content. A 90 MW m^-1 crown fire in vegetation with potassium content of 0.5% was predicted to produce a maximum conductivity of 0.022 mho m^-1. Electrical conductivities were lower for a shrub fire with an intensity of 21 MW m-^1. The model predicted conductivities of 0.0021 and 0.0009 mhom-1 for potassium content of 3.0 and 0.5% in vegetation, respectively.