New insights into burning regimes in a closed mechanically ventilated compartment through experimental and theoretical analysis
Résumé
The fire scenario in a closed, mechanically ventilated compartment is increasingly encountered in the industrial and residential sectors. In this work, the scenario is studied experimentally at a reduced scale using a gas burner and analysed with the support of the well-stirred reactor (WSR) model. The variables investigated are: the duration of the combustion phase; the oxygen and carbon monoxide mass fractions; and the gas temperature. The results show two different burning regimes from fuel controlled to ventilation-controlled characterized by the global equivalence ratio (GER). The transition between the two regimes corresponds to the most critical situation in terms of fire risk, with combustion at the extinguishing limit, yielding the highest temperature and carbon monoxide production. The results show the distinction of scenarios with mechanical ventilation, particularly regarding the critical GER value for transition. These scenarios differ from those with natural ventilation due to the way air is supplied to the fire. The WSR model provides a suitable support to interpret the global characteristics of the fire. These new results obtained in a closed, mechanically ventilated compartment can be used to identify the most complex and critical configurations in terms of risk assessment.
