This contribution presents a study on pressure instabilities observed during large-scale tests pool fire in a confined and ventilated enclosure. Fire scenarios for which pressure instabilities phenomena have been observed concern liquid pool fires in a confined enclosure equipped with a ventilation network composed by an inlet branch in the lower part of the vessel and an exhaust branch in the upper part. Pressure instabilities consist in pressure oscillations showing different regimes (growths, stabilization, damping) but with a constant frequency of about 0.1 Hz to 0.2 Hz. The amplitude peak to peak can reach 25hPa and the duration of these oscillation periods can vary from few minutes to decades of minutes according to the test. Two major consequences of this phenomenon are flow inversions in ventilation branches and over pressure peaks. The paper presents experimental results observed on five large-scale tests. Detailed spectral analysis of the instabilities is presented. A first attempt of a theoretical analysis based on the spectral analysis of the system is presented.
(1) : IRSN.
(2) : Stagiaire EM2 Marseille.