Laminar flame propagation in droplet suspension of liquid fuel

Abstract

As a first step in the clarification of the mechanism of flame propagation in the spray of a liquid fuel, a study was conducted into the case of laminar flame propagating through the droplet suspensions of a liquid fuel, having uniform diameters. Initially, in order to examine the nature of flame propagation, tetralin droplet suspensions having approximately uniform diameters were prepared, and their concentration at the lower limit of flammability was examined, and, at the same time, the appearance of the flame and the process of its propagation were observed. On the basis of this observation, a model of flame propagation was proposed, in view of the phenomenon that the droplets burning at the flame front heat the unburned mixture, then the unburned droplets are ignited after the lapse of a certain ignition lag. Using this model, a theoretical analysis was carried out, and the velocity of flame propagation and the concentration at the lower limit were calculated. The predicted values showed satisfactory agreement with experimental results, at least qualitatively. From this analysis, it was found that sedimentation of droplets exerts great influence on the process of flame propagation, and that, in case the mixture containing droplets is diluted by nitrogen, its effect on the lower limit depends greatly upon the droplet diameter, as had already been found experimentally.