UC Berkeley

The spot ignition of combustible material by hot metal particles is an important pathway by which wildland and urban spot fires and smolders are started. Upon impact with a fuel, such as dry grass, duff, or saw dust, these particles can initiate spot fires by direct flaming or smoldering which can transition to a flame. These particles can be produced by processes such as welding, powerline interactions, fragments from bullet impacts, abrasive cutting, and pyrotechnics. There is little published work that addresses the ignition capabilities of hot metal particles landing on natural fuels. The work presented here investigates the ignition capabilities of these particles by breaking the overall spot ignition process into three distinct subprocesses: generation, simultaneous transport and thermo-chemical change of the particle, and ignition of a fuel. This dissertation will present research on these subprocesses.

The first subprocess, generation, was studied through literature searches and the results are shown in Section \ref{sec:Generation} of Chapter \ref{ch:Introduction} along with background on spot fires and previous and associated literature. Then in Chapter 2 a model for the heterogeneous oxidation of iron and steel particles is presented. In Chapter 3 results are presented on the ability of hot metal particles composed of four different metals to ignite a cellulose powder fuel. Then in Chapter 4, the ability of aluminum particles to ignite six natural fuels of different compositions and morphologies was investigated. Then the ability of aluminum and stainless steel particles to ignite a smolder in a grass powder fuel was investigated through experiments and modelling in Chapter 5.