Simulative Studies On Water Mist Fire Suppression Under Longitudinal Ventilation In Long And Narrow Spaces

With the increasing development of construct of long and narrow spaces, which are brought into play important roles in many fields, fire risk also improves rapidly. In recent years, tunnel fire disasters have happened with high frequency, and methods to suppress and extinguish fire bring up the higher request, so traditional measures of smoke control by forced ventilation have not already satisfied these requests. As the leading Halon alternatives, water mist technology shows broad applications with its advantages: clean, high efficiency, low cost and little damage to protected objects. Especially, the technology is increasing recognized and extended during the applications in long and narrow spaces such as traffic tunnels, subways, cable tunnels and so on in recent years. In the interest of enhancing fire suppression effectiveness in this kind of spaces, longitudinal ventilation was selected as the representative characteristic, and the mechanisms and rules of water mist fire suppression were studied with simulative calculations and experiments in more details.Firstly, the characteristics of combustion and smoke movement were analyzed under the condition of longitudinal ventilation. Compared with experiments results in open spaces by summing up former results in tunnels, variability of heat release rate under longitudinal ventilation was discussed. Simulative experiments were performed using wood cribs in order to study the effect of combustible configuration on combustion process, to analyze the influence on temperature and CO concentration and to demonstrate the importance of density of accumulation under forced ventilation.In this thesis, the LDV/APV system and wind tunnel with low speed were both utilized. Through the experiments of measuring the distribution of drop velocity and diameter with different wind speeds and the analysis of calculating water mist fluxes, the relationship between wind speeds and movement distances were received.Based on the effects of longitudinal ventilation on fire behavior and droplet movement respectively, simulative studies on water mist fire suppression were performed. Scaling relationship group for water mist fire suppression has been extended to include forced longitudinal ventilation, for the guidance to determine the...