Experimental investigation on dynamics of spray atomization, ignition, and flame propagation in an annular combustor

The combustor employed in small and medium-sized turboshaft engines is characterized by a small flame tube height and a large distance between adjacent burners, rendering it challenging to ignition. Moreover, the process of spray ignition exhibits complexity and needs further investigation. This study will delve into the performances of spray atomization and spark ignition within an annular combustor. Our objective is to thoroughly elucidate the interplay among atomization characteristics and flame propagation, seeking to shed some light on the fundamental mechanisms underlying flame dynamics from the perspective of timescales during the light-round processes. Planar Mie scattering and high-speed imaging technologies are employed to capture droplet distribution and time-resolved flame images, respectively. We have developed an algorithm capable of precisely tracking the flame front, enabling us to map out the trajectories of flame propagation. An analysis of transient flames reveals that the movement of leading points can be elucidated by the characteristics of the flow field and the distribution of the spray. It is demonstrated that the velocity of the flame front is affected by factors such as the pressure drop, equivalence ratio, and the distance between adjacent burners. Through an analysis of numerous spark events, this work identifies three distinctive flame propagation patterns: swirling-entrainment, archlike-entrainment, and another archlike-entrainment pattern. It is noted that these patterns exhibit variations by alterations in pressure drop and equivalence ratio.