Experimental study of back-draft in a compartment with openings of different geometries

This paper presents the results of reduced-scale experimental tests to study back-draft in a reduced-scale compartment (1.2 m × 0.6 m × 0.6 m), fitted with six different geometries for the opening on one end-wall and with two geometries for the opening in the ceiling. The experimental variables included the flow rate, the time during which the fuel was burned, and the geometries of the inlet. The quantities recorded before the back-draft included temperature and the concentrations of oxygen, carbon dioxide, and carbon monoxide. To quantify the effect of back-draft, the gas velocities in the inlet and also the pressures in the compartment were measured. The effects of different inlet geometries on the occurrence of back-draft are discussed. This study shows that the mass fraction of total hydrocarbons (i.e, the un-burned methane in this study), whose critical value varies with the geometry of the inlet, is a key parameter determining the occurrence of back-draft.