Experimental investigation on the ignition dynamics of an annular combustor with multiple centrally staged swirling burners

The ignition behaviors of an annular combustor consisting of 16 centrally staged swirling burners are experimentally investigated in this work. This research is mainly focused on the light-round mechanism of burner-burner flame propagation. The swirling flow structure of the staged burner and the flow interaction between multiple burners in the annular combustor are well measured via the particle image velocimetry method. Two high speed cameras are applied to analyze the light-round process from the side view and the top view. The light-round time, ignition and extinction limits, flame propagating pattern, and dynamics of flame leading point are analyzed. Increasing the equivalence ratio, the light-round time decreases gradually. A more complicated “sawtooth” pattern of flame propagation is discovered during the burner to burner flame propagation, compared to that with non-staged burners. The trajectories of the flame leading points are moving in a “zigzag” pattern during the light-round process. The trajectories of the anti-clockwise leading point are near the inside wall, while the trajectories of the clockwise one are closer to the outside wall. For various equivalence ratios and airflow rates, the circumferential flame speeds of the clockwise flame front are constantly faster than the anti-clockwise one. In addition, the two flame speeds and their differences increase with larger equivalence ratio. These characteristics are very different from those in an annular combustor with non-staged burners.