Experimental investigation on ignition and cross-flame performance of dual-annular combustor

Abstract

The ignition and co-flame process of the dual annular combustor(DAC) was studied using high speed camera in order to investigate the mechanism of flame stabilization and propagation in the combustor. Particle Laser Velocimetry (PIV) combined with high speed camera were used to measure the key properties of ignition kernels, including orientation, growth direction, movement velocity, flame propagation speed. Results showed the flow field structure obtained by PIV includes the primary air jet, the dilution air jet, the inner/outer recirculation zones, the central body jet, and the middle area of the central body. The ignition process could be categorized into the four stages: kernel generation at the end of the igniter, kernel movement at the recirculation zone, kernel growth at the head, and burner-scale flame establishment at the combustor, the flame had significantly different performance in each stage. The time of each stage decreases with the increase in the inlet Reynolds number, which significantly reduced the ignition delay time. Additionally, as the excess air coefficient increased, the ignition of pilot stage become more complex and the ignition delay and the cross-flame time increased. The relative location of the flame center and the centroid confidence interval of the flame path was used to judge ignition success. The flame path analysis showed that the transverse propagation mode of flame in the head is the determining stage of ignition. The splitting direction and the flame statement were related to the flame's position and shape in the flow field, the transverse flame splitting played a vital role in the ignition process. Two typical co-flame mechanisms existed in the cross-flame process of the DAC as follows: the flame tongue co-flame mechanism under small working conditions and the heat reflux combined small flame co-flame mechanism under large working conditions.