Impact of external operating parameters on the performance of a cyclonic burner with high level of internal recirculation under MILD combustion conditions

Internal exhaust gases recirculation represents a promising strategy to stabilize the oxidation process for new technologies (such as MILD, LTC) that limit system temperatures to reduce pollutants emissions while ensuring high process efficiency. A cyclonic flow configuration may represent a proper way to enhance the mixing process in very short time while allowing for residence times long enough to achieve complete oxidation of diluted and pre-heated mixtures. To this aim, a cyclonic burner was built and used to assess potentials of this peculiar configuration. Experimental tests have been performed varying independently the external operating parameters, namely the overall dilution level, the mixture composition and the average residence time. Temperature measurements inside the combustor and gas sampling analysis at the stack were carried out to evaluate cyclonic burner performance and pollutant emissions. Distributed combustion regimes have been proved to occur when a sufficient entrainment of hot species in the fresh oxidant and fuel jets is attained. The experimental results obtained for reactive conditions were ascribable to some peculiar characteristics of the cyclonic flow field. They confirmed that the cyclonic configuration is a valuable solution to stabilize the oxidation process while containing the pollutants emission for a wide range of operational parameter