Experimental Study On Flame Spread Over Sand Bed Wetted With Liquid Fuel

Liquid-fuel was widely used in our daily life as well as transportation and industrial production. When a combustible liquid-fuel is spilled in the process of producing, transporting, storing and using, it will permeate into the soil or a porous material such as sand-bed. In the event of fire, a flame will spread over the sand-bed wetted with the spilled combustible liquid-fuel quickly, and cause the occurrence of an fire accident that leads to property damage and casualties. In addition, sand is identified as extinguishant after the fire. Thus, it is essential to explore the fire mechanisms of flame spread over sand-bed wetted with liquid fuel to provide theoretical basis and some guideline for fire suppression.The0.6×0.04x0.02m self-designed channel, colorized schlieren system, CMOS cameras and K-thermocouples were used to study the characteristics of flame spreading over sand-bed wetted with1-butanol in the paper. Measurements included schlieren images, visual observation, flame spread rate and temperature distribution. The influencing mechanism on flame spread of the different particle size, the fuel-sand ratio and variation of surface inclination angles were analyzed. The aspects of flame spread, flame spread rate and the temperature distribution over sand-bed, which was wetted with1-butanol, were revealed in this paper. The main research results as follow:1. Aspects of flame spreadThe spreading flame consists of the blue leading flame edge and the yellow luminous zone. As particle size increased, the length of the yellow luminous zone and the flame height decreased. Otherwise, the flame height and the yellow luminous zone all increased as the fuel-sand ratio and the surface angle increased.2. Flame spread rateIn the case of sand beds wetted with1-butanol, the flame affected by the surface inclination angle, the fuel-sand ratio and the capillary rise acts spread at a constant speed. The capillary rise effect plays an important role to transfer liquid and vapour from the sand bed to the surface at which combustion process takes place. The thinner sands have larger capillary rise, resulting to the availability of more1-butanol at the surface, thus, flame spread rate increases as particle size decrease. Meanwhile, flame spread rate increases as the fuel-sand ratio and the surface inclination angle increase. 3. Temperature distributions on sand-bed layersNo matter flame spread on the horizontal surface or the inclination surface, a preheated zone exists in front of spreading flame. The results indicated that the distance between the steam face and the flame leading edge increased as the fuel-sand ratio and the surface inclination angle increased. The internal thermal boundary layer magnified as the fuel-sand ratio increased and the surface inclination angle decreased which existed in the sand layer.