Smoke Coagulation in Compartment Fire Modelling

Abstract

The effect of coagulation on the total smoke particles concentration and mean particles volume fields is studied under the conditions of a compartment fire. An approximate analytical consideration of aerosol temporal behaviour accounting for the simultaneous action of aerosol generation, coagulation, and dilution is given, and two regimes of fast and slow coagulation are considered. A CFD model of compartment fire, including smoke aerosol generation and coagulation, is presented. The results of CFD simulation for a hydrocarbon burner sooting fire with smoke movement and coagulation in a two room compartment are analysed, where the regimes of coagulation and their key features predicted by means of analytical consideration are illustrated by numerical simulations. For a given geometry of the compartment, fuel type, and volumetric smoke generation rate, the coagulation rate was shown to be determined by the mean volume of the particles generated in the flame zone. In the limit of small particles generated (fast coagulation regime), the aerosol parameters far away the flame zone were found to be weakly dependent on those inside the flame zone due to a strong coagulation effect. In the opposite limit of large particles generated (slow coagulation regime), coagulation has no effect on the aerosol parameters. The approximate boundary between the two regimes has been defined.