Fire Safety Science Digital Archive

Experiments have been made for investigation of a flame accelerating during its propagation in gaseous mixtures of propane - butane- air in the large-scale semi-open horizontal tube (diameter 1 .45m, length 100m ) with combustion initiated near the closed end of the tube. We found, that in most experiments the flame velocity, S, increases linearly with a distance, L , from the end of the tube. At a distance 15 -20 m from the closed end of the tube the change of the regim of flame propagation may take place with the appropriate change of the proportionality coefficient between S and L. The experiments showed that combustion process duration, in a fixed tube cross - section, which is detected by photodiodes and electric potential transducers, decreases exponentially with the distance from the closed end of the tube. The exponent index does not depend on a combustible mixture composition. The linear relationship between the flame velocity and the distance from the closed end of the tube was qualitatively explained based on the concept on a flame accelerating due to formation of an elongated flame front.