Abstract:
Bluff-body burners are widely used in combustion chambers of industrial equipment such as jet engines, gas-turbines and boilers. Safe operation and low pollutant emission in these equipment directly demands understanding and controlling of ignition process in bluff-body burners. In this paper, a large-eddy simulation based on steady flamelet/progress variable approach was applied in a turbulent non-premixed bluff-body flame and its ignition process. Simulating two cases including non-reacting bluff-body flow (NRBB) and Sydney methane/hydrogen flame (HM1E), we comprehensively compared statistical results with experimental measures and previous numerical investigation. Then, we presented an instantaneous ignition process and flame development in Sydney bluff-body burner. Finally, the ignition process was analysed and characterized in detail, and a four-step process of flame ignition was proposed:decaying of ignition source, ignition initiation, generating of ignition kernel, and ignition success, which was identified by variation of peak values of temperature, OH and CH
2O mass fraction. In addition, the ignition kernel stayed at the stern of the outer vortex in the recirculation zone of the cold flow of the bluff-body burner.