Experimental analysis of low air pressure influences on fire plumes

To examine the pressure effect on burning rate, flame height and axial temperature distribution of diffusion fires, experimental measurement and theoretical analysis on circular n-Heptane fires with serial sizes were conducted at two altitudes, i.e. 100.8 kPa (in a sea-level city Hefei) and 64.3 kPa (in a Tibetan city Lhasa). From the results, the mean burning rate at quasi-steady stage and boiling stage consistently implied that the exponent α (ṁ″∼DPα) varies for different heat transfer domination stages, i.e. α ⩽ 0 for conductive stage and α = 2/3 for convective stage. Analysis shows that the flame height, the axial flame and plume temperatures are all well correlated with the dimensionless heat release rate Q⁎∼Q/(PD5/2), with the correlation coefficients derived from the current low-pressure measurements. Analysis shows that the flame height and the plume temperature increase with the pressure rise as a power function of pressure for the same pool size.