Flame extinction experiments were conducted using propane (with and without additives) and Jet A (in partially premixed and diffusion flame modes). A single-flame counter-flow burner configuration was used to measure the extinction limits. The set-up consisted of two contoured nozzles (exit diameter of 6.4 mm), designed to produce top-hat velocity profiles at the exit with a separation distance of 12.7 mm between them. A cooling system, which consisted of a submersible water pump, water reservoir and a split aluminum cooling jacket, was used to cool the top burner and avoid heating of the top burner by the hot buoyant flame products. A nitrogen shield was used to protect the flame from air entrainment and perturbations from the surroundings. A heating system was used to vaporize the liquid Jet A fuel in air or nitrogen maintained at a temperature up to 325 °C. For premixed propane flames, as the stretch rate increased from 364 s−1 to 462 s−1, the volumetric percentage of propane varied from 2.23% to 2.83% at lean extinction. These results, when modified suitably to take into account that only air was fed from the top burner, agreed well with previous results obtained from twin-flame configurations. For a given stretch rate, the propane flame extinguished at a richer condition when nitrogen or carbon dioxide was added to the air stream. Also, carbon dioxide was more effective in extinguishing the flat flame than nitrogen. The flame extinction limits were measured for Jet A for stretch rates varying between 218.7 s−1 and 412.9 s−1. It was found that the Jet A flames in diffusion mode were more resistant to extinction than those in the premixed mode.
A Study on Retardation of Laminar Flame Extinction due to Locally Controlled Stretch Rate
