Study on the flame behavior of ethanol spill fire on base plate with different width in longitudinal ventilation environment

Abstract

The intricate flame behavior of spill fire in a ventilated tunnel significantly aggravates the severity of accident consequences. Flame height, flame tilt angle, and combustion area were measured by conducting ethanol spill fire experiments in model tunnel with different wind speeds in base plates of different width. Furthermore, critical transition wind speed, dimensionless analysis of burning rate and heat transfer analysis were performed. The findings reveal that, in windy conditions, wind speed linearly lowers flame height, while baseplate width’s impact is irregular. Longitudinal ventilation notably causes flame inclination, base plate width and wind speed jointly affect inclination at low wind speed, however, in high wind speeds, the inclination is mainly determined by the wind speed. With the increase of wind speed, the burning rate firstly increases and then decreases, resulting in an initial decline followed by an increase in the combustion area. The increase in base plate width not only leads to a continuous increase in the combustion area, but also results in a decrease of the critical transition wind speed at which the burning rate changes. An equation for the dimensionless burning rate in upwind environments has been developed, revealing that burning rate is significantly higher in longitudinal wind conditions compared to still air. Furthermore, the difference becomes more pronounced as the baseplate width decreases. By taking into account the asymmetric air entrainment of the spill fire flame, a revised model for flame height and inclination has been introduced, utilizing a dimensionless array (2n+1/n). This model effectively predicts the morphological changes of spill fire flames under windy conditions, and the dimensionless flame height of spill fires is approximately 0.18 to 0.36 times that of pool fires.