Macroscopic Flame Structure in a Premixed-Spray Burner : Formation and Disappearance Processes of Droplet Clusters and Two-Stage Flame Structure

In an attempt to elucidate formation and disappearance processes of droplet clusters in spray flames, simultaneous measurements consisting of laser tomography and flame chemiluminescence detection are applied to a premixed-spay burner. The smart combination of measurements provides time-series data-set serving for better understanding of spray flames, which essentially contains inhomogeneity in space and time. It is revealed that preferential flame propagation through a premixed-spray stream plays a significant role in creating droplet clusters and that droplet clusters formed in this manner evanesces from their outer boundaries. Those observation confirms that the premixed-spray flame comprises both premixed-mode flame in upstream region and diffusion-mode flame in downstream region, respectively, i.e., two-stage flame structure previously reported for spray flames stabilized in either counter or stagnation flows.