Inhibition of Propane/Air Premixed Flame by Water Mist

Abstract

The effects of fine water mist on flame temperature and laminar flame speed of propane-air mixtures were investigated both experimentally and numerically. In experiments, flame temperature and laminar flame speeds were measured using a single jet-plate configuration for the cases with and without water mist. The numerical simulation was also performed using the OPPDIF code in CHEMKIN package. To include the phase change with evaporation, the evaporation process was assumed as a chemical reaction of which rate constant follows the Arrhenius law. For the case without water mist, experiments showed that the flame speeds increase with the stretch rate toward the limit of extinguishment. This tendency was fairly reproducible by the numerical simulation with Davis-Law-Wang kinetic mechanism. The flame temperature was measured by a fine wire thermocouple. The flame temperature decreases with the water mist addition toward the limit of extinguishment within the range of φ from 0.8 to 1.2. The reduction of the flame temperature is more enhanced for lean and rich mixtures than the stoichiometric one. On the other hand, in terms of inhibition of the flame speed, the water mist is more effective for lean mixture than rich one. Reduction of flame temperature in rich mixture does not contribute to decrease the flame speed. Additionally, the stretch rate also decreases the flame temperature. Therefore, for lean mixtures, an appropriate combination of water mist and stretch rate can enhance the suppression effectiveness of water mist.