Axial temperature profile in vertical buoyant turbulent jet fire in a reduced pressure atmosphere

Characteristics of a vertical jet fire in a reduced pressure atmosphere (at high altitude) have not been quantified in the literatures. In the reduced pressure atmosphere, the air/oxygen density is lower, which in turn affects both combustion and entrainment, and hence the axial temperature profile of a diffusive turbulent jet fire. Experiments have been conducted in this work to investigate the axial temperature profiles of propane turbulent buoyant jet fires produced by nozzles with diameters of 4–10 mm in both reduced- (0.64 atm) and normal pressure (1 atm) atmosphere. It is found that the maximum temperature in the flame zone is a bit higher, the temperature decreases faster vertically and is somewhat lower in the buoyant plume zone in the normal pressure than those in the reduced pressure. The virtual origin is then deduced and clarified to be larger in the reduced pressure, however, it can be correlated non-dimensionally with flame Froude number (Frf) in a 2/5 power law function for both these two pressures. Finally, the normalized axial temperature profile against non-dimensional height above the virtual origin can be still well characterized into three regions in the reduced pressure by the same power law functions as those in the normal pressure.