Progress on light-round ignition dynamics in annular combustor

Annular combustors are generally applied in aero-engines. Study on light-round ignition dynamics of annular combustors is important for ignition reliability. Laboratory-scale mo-dels have become a feasible way to investigate the ignition mechanism of annular combustors due to its low economic cost and high precision. Several typical laboratory-scale annular combustors and related experiments are reviewed, including the annular combustor MICCA from EM2C in France, the premixed or non-premixed annular combustor made by Cambridge University, the annular combustor model referred from an industrial gas turbine in Technical University Munich, and the annular combustor TurboCombo with the coupling of the combustor and the turbine interaction made by Zhejiang University. The ignition process can be generally divided into three phases:(1) the formation of a flame kernel in a flammable mixture around the igniter; (2) the kernel expands and grows to be a swirling flame, which is stabilized and anchored upon the adjacent burner; (3) the propagation of the flame (light-round), which successively igniting all the burners and then reaching to steady state. The factors influencing the light-round process are quite complicated. Previous experimental and numerical investigations focus on the equivalence ratio, ignition mode, thermal power, bulk velocity, spacing between burners and so on, which influence the characteristics of the ignition, flameout, flame propagation mode and light-round time in the annular combustor. Recently, the spray combustion is also studied in the similar models. Meanwhile, the application of advanced laser diagnostics with high resolution would promote the understanding of the light-round mechanism.