Oscillatory combustion phenomenon in mechanically ventilated enclosure with propane gas fire

Abstract

This study deals with unstable combustion regimes during a fire scenario in a mechanically ventilated enclosure, which are common in industry and particularly in nuclear facilities. These regimes are encountered for fire sources and ventilation configurations leading to oxygen deficient conditions close to the extinction limit and bring into play the mechanisms of local extinction and re ignition. This study is based on the analysis of propane gas fire experiments performed at a reduced scale in a mechanically ventilated compartment with fire heat release rate and ventilation flow rate as parameters. The variables analysed are room pressure, gas temperature and oxygen concentration in the enclosure and videos. Oscillatory combustion regimes appear for conditions of propane and ventilation flow rates in a ratio close to stoichiometry and the frequencies obtained are between 50 and 100 mHz. A comparative analysis with literature shows the influence of a fire with a constant pyrolysis rate compared to pool fires with a variable pyrolysis rate. This study provides new observations and quantitative data on unstable phenomena that can be used to validate numerical simulation attempts of these phenomena.