Experimental Study on the Dynamic Combustion Behavior of Thin Fuel Layer Caused by Instantaneous Leakage of Ethanol and Gasoline

This paper presents an experimental and theoretical research on the instantaneous leakage fire of ethanol and gasoline. A horizontal substrate without vertical boundaries was used, and the leaked fuel could spread freely. The fuel leakage volume was set from 7 mL to 75 mL, and the ignition time was set from 10 s to 40 s. Results showed that the fuel thickness in this study is observed less than 1 mm and decreases continuously throughout the whole process. Different fuels showed different combustion behaviors in same cases. For ethanol, its combustion does not change the surface morphology, and the combustion process includes three stages, namely spreading, quasi-stable and shrinking. The quasi-stable stage is caused by the dynamic balance between flame development and fuel consumption. The quasi-stable burning rate of ethanol leakage fire is about 70–90% to pool fire with same diameter, however, their flame heights are similar. Theoretical analysis was conducted on the heat radiation absorption in the fuel, and found that at longer ignition times, the smaller absorption ratio caused by the lower thickness plays a more important role than the larger radiation feedback from the larger burning area. For gasoline, the soot from insufficient combustion adheres to the substrate impeded the flow of fuel during combustion process, and the burning area includes two parts, i.e. the center constant flame and flash flames intermittently appearing at the edge. The burning area, burning rate and flame height of gasoline decrease continuously during the whole combustion process. In addition, some interesting phenomena are observed before extinguishing, such as the revolved flash flame for gasoline, and the relevant explanations have been attempted.