Experimental investigation on ceiling temperature characteristics induced by weak and strong fire plumes in tunnel fires equipped with two-point extraction ventilation using smoke extraction channel

Abstract

In this paper, maximum excess temperature and longitudinal temperature decay induced by weak and strong fire plumes were discussed in tunnel fires with two-point extraction ventilation using the smoke extraction channel. First, a model for maximum excess temperature was developed based on theoretical analysis and experimental phenomenon. Subsequently, the characteristics of maximum excess temperature and longitudinal temperature decay were analyzed. Experimental results showed that the maximum excess temperature for the weak plume is higher than that predicted by the previous model due to the existence of the smoke extraction channel. The maximum excess temperature for the strong plume is much higher. Moreover, the function of maximum excess temperature for the weak plume was similar to the previous model, while that for the strong plume was different from the previous model when the fire was located at the tunnel center. Besides, exhaust rate and longitudinal fire location far from the vent did not have a considerable impact on the maximum excess temperature and longitudinal temperature decay in the fire section induced by weak plume or strong plume. Finally, new prediction models for maximum excess temperature induced by the weak and strong fire plume were validated according to experimental data. Moreover, a fast calculation model driven by experimental data was established to predict longitudinal temperature decay.