Bluff-Body Mild Combustion of a Premixed CH4/Air Jet in Hot Coflow

Industrial boilers and gas turbines traditionally use one bluff-body (BB) or more to create the recirculation zone for a stabilized flame. By comparison, the BB or flame-holder is often avoided for establishing MILD (moderate and intense low-oxygen dilution) combustion that requires high reactant momentum. This study carried out numerical simulations of a premixed CH4/air flame in coflow of hot exhaust gas from a BB burner with spark ignition (BB-S) and without spark ignition (BB-NS), as well as non-BB burner with no spark ignition (NBB-NS), under varying coflow temperature. The results show that MILD combustion can be achieved from a BB burner in the BB-NS case. Moreover, the MILD combustion in both BB-NS and NBB-NS cases produce maximum temperature and mass fraction of CO that are much lower than those from the BB-S case. As a result, the volume of reaction is much larger in the former cases than the BB-S case. As for emissions, both CO and NO emissions decrease with lower coflow temperatures across all cases. Notably, the MILD combustion produced by the BB burner in the BB-NS case exhibits lower NO emissions compared to the traditional BB-S flame, and even lower than the conventional non-BB MILD combustion in the NBB-NS case.