Effect of water mist on temperature and burning velocity of stretched propane-air premixed flames

摘要

Effects of fine water mist on the flame temperature and laminar burning velocity of propane/air premixed flame were investigated by using a single jet-plate configuration. For the case without water mist, the measured laminar burning velocities are in reasonably good agreement with previously reported data and numerical simulation. The dependence of the burning velocity on the stretch rate for the case without water mist is positive for all mixtures tested, resulting in the negative Markstein length, which coincides with previous experimental and theoretical studies. With water mist addition, the laminar burning velocity is lowered significantly and its dependence on the stretch rate is changed to negative. This leads to apparently positive Markstein lengths. Concurrently, the flame temperature decreases linearly with the water mist mass loading. Also, it decreases with the stretch rate, even if the water mist mass loading is kept constant. The positive Markstein length was discussed on the basis of the mist droplets behavior in the stagnation flow field. Even if the mist mass loading is kept constant, the mist droplets do not follow the diverting flow field when the stretch rate is high and the droplets accumulation occurs in the stagnation region where the burning velocities were measured. This fact results in the lower burning velocity and lower flame temperature as compared to those measured for uniformly dispersed water mist.