Investigation of the fire mass loss rate in confined and mechanically ventilated enclosures on the basis of a large-scale under-ventilated fire test

Abstract

This study concerns the under-ventilated combustion regimes of a fire scenario in mechanically ventilated enclosures. Using the theoretical approach of the well-stirred reactor model and the data-base of large-scale pool fire tests, the study analyses the mass loss rate as a function of the environmental conditions. The novelties lie in the analysis of a large set of realistic scenarios involving complex geometries (several compartment connected) and new ventilation configurations and the applicability of the well-stirred reactor model to interpret these scenarios. The variables of interest are the combustion regimes (stationary, transient or with rapid quenching), the duration of the combustion phase and the mass loss rate. The results show a satisfactory prediction of the well-stirred reactor model to interpret the experimental results of complex and realistic fire scenario and the robustness of this model to deal with the under-ventilated regimes. The analysis also highlights the interest of two new parameters rarely used in the literature, the ventilation factor and the mass factor, to characterize under-ventilated scenarios. The analysis points out the importance of the relationship expressing the burning rate as a function of environmental conditions (oxygen level and external flux) and extinction conditions.