Experimental study on the flame extension and risk analysis of a diffusion impinging flame in confined compartment

摘要

In this work, an experimental investigation on a diffusion impinging flame in a confined compartment was performed. The objective was to study the influence of confinement on the behavior of a flame impinging the ceiling and to deduce the auto-ignition risk of the smoke produced in the confined compartment. For this, configurations with five confinement levels were constructed by the condition of windows and/or door in the compartment and the variation of the heat release rates was made between 0.5 and 18.6 kW. To evaluate the flame morphology and flame extension length, an image processing method based on the direct linear transformation algorithm and the fire segmentation algorithm was adopted. From the experimental data, it was shown that the heat release rate of 4.6 kW presents a critical value for the flame extension in confined configurations, which corresponds to the equivalence ratio of the enclosure greater than 1, highlighting an under-ventilated environment. In addition, an auto-ignition risk analysis of smoke with unburnt gas in the compartment was carried out. The concentration and temperature of these gases were compared to the lower flammability limits and the auto-ignition temperature. It was observed that there was auto-ignition risk of the smoke under the ceiling, especially in the confined compartment of equivalence ratio greater than 1. Under these conditions, it is possible to have a fire spread to another compartment.