ABSTRACT
Accidental spill of combustible liquids over porous solids such as sand, soil, and concrete may lead to major fires in process industries and residential buildings.
An experimental study has been carried out in order to elucidate the effect of properties of porous bed and liquid fuel on flame spread rate and combustion behaviours, including temperature distribution profile over porous bed soaked with finite amount of liquid fuel. Sand bed depths from 13.3 to 39.9 mm with sand size of 0.5 to 5 mm and Propenol flash point (12 C°) were utilised as porous beds and liquid fuel, respectively.
Results show that flame spread rate in no airflow configuration increases as the bed depth decreases. Similar flame spread deceleration was observed for larger bed particles. Under both assisted and opposed airflow condition the rate of flame spread decreases as airflow is increased, however, the decrease in the flame spread rate was more distinct under opposed airflow. For very deep beds containing large particles flame stopped to a halt when airflow got higher than 1 m/s.
Results corresponding to the temperature distribution indicate that the bed temperature increases quickly, but the rate of increase slows down at a temperature around 82C° which is very close to the boiling point of the fuel. This phenomenon is referred to as the temperature retardation. Beyond retardation, the temperature increases rapidly again to attain its maximum value. The temperature diminishes slowly until spontaneous extinction is achieved. Typically it takes longer for a deeper bed to achieve its maximum temperature.
Keywords: Flame spread, Liquid fuel, Porous bed, Temperature distribution, Assisted and opposed airflow.
