Experimental Research On Effects Of Slope And Fuel Load On Point-source Fire Spread

Surface fire spread is the most important form in forest fire.This work main focus on the effects of slope angle and fuel load on the upslope fire behaviors by point ignition.The excelsior was used as fuels.In tests,7 slope angles and 3 kinds of fuel loads were used.We discussed the flame geometry(fire line angle,flame tilt angle,flame length),fire line contour,global ROS(rate of spread),local ROS and residence time under different slope conditions..The fire line angle and flame tilt angle decreased with increasing slope,while the flame length increased.For zero-slope condition,the fire line contour was in regular circle,and the residence time was higher than that of upslope conditions.For slope conditions,the fire line contour was in tear shape.When slope angle less than 20°,ROS increased slightly with slope.When slope angle more than 20°,ROS increased quickly with slope.ROS was in global stable and local fluctuation.From the ignition position,the downward,left and right ROS fluctuated with slope.The upslope flame length increased with fuel load.The increment in fuel load will enhance the ROS in any direction.Under 0～200,this promotion was more insignificant compared to that of higher slope.The residence time of any directions of fire spread increased with fuel load except for zero-slope.During upslope fire spread,flame length increased and flame tilt angle decreased with increasing slope,which induced an enhanced flame radiation to unburnt fuel bed and caused an increment of ROS.