Flame distortion and backwards heating behaviors of moving fires: A comparative study.

• Flame length of moving fires is 15.2%-45.7% more than that of stationary fires. • Temperature upstream moving fire sources is significantly elevated. • Entrainment and heat transfer mechanism of moving and stationary fires compared. • Backwards heating behavior of moving fires can bring threatening thermal hazard. Moving fires have been paid great attention by researchers in recent years, while the behavior of this special combustion phenomenon has not been fully investigated. In this paper, a 1:10 scale burning car was innovatively designed based on Froude similarity criterion, and a series of moving model experiments were conducted. The flame morphological characteristics and heating behaviors between the stationary and moving fires were thoroughly compared. The results manifest that the distorted flame of moving fires is 15.2%-45.7% more than that of stationary fires, while this behavior is not accurately predicted by current models for wind-blown and wall-attached flames, which suggests that the wind tunnel test has limitations in studying moving fires. Besides, compared with stationary fires, the temperature upstream of the fire source is considerably elevated, and the heat transfer from the flame to the top surface of the burning car is dramatically enhanced. A physical model is proposed to describe the flame distortion and backwards heating behaviors in moving fires, which reflects the important role of the air entrainment and the cool fuel-rich cone in the combustion process. This paper represents a first step toward understanding the behavior of moving fires, which can provide a framework to deeply investigate the combustion mechanism of moving fires in the future. [ABSTRACT FROM AUTHOR]