Hot Surface Ignition of Flammable and Combustible Liquids

Due to the known hazard of ignition of flammable and combustible liquids by hot surfaces, recent studies have been conducted to better understand the influence of various effects such as orientation of the hot surface, its size, surface material, and the residence time of flammable vapors near the hot surface. In this study, tests were conducted with gasoline and other flammable fluids using a hot surface to determine the relative influence of volatility, as represented by boiling point, and the Minimum Auto Ignition Temperature (AIT) (ASTM E 659) on the hot surface ignition temperature. We present the results from over 1,000 ignition tests that were carried out using a highly reproducible test protocol that includes a circular hot plate section. The experimental hot surface was not designed to represent any specific automobile component nor does it necessarily represent the conditions that exist in the engine compartment after an impact. Three different blends of gasoline and 6 other pure liquid fuels were investigated. The 6 fuels were chosen to span AIT ranges of approximately 210-425°C and boiling points of approximately 30-185°C. The results of this testing reaffirm that hot surface ignition has a statistical character that cannot be defined by a single ignition temperature. It was found that the temperature of 50% probability of ignition is strongly correlated with the auto ignition temperature as has been suggested before. The ignition of gasoline exhibited a weak dependence on octane number. The volatility of the fuel was not found to have a noticeable effect on ignition by a hot surface.