Experimental Analysis of a Double Swirl Burner

The increasingly stringent regulations push towards the developments of industrial combustion systems (boilers, furnaces, and gas turbine) having single digit NOx emission. A well-known methodology to achieve high combustion efficiency and low pollutants emission in combustion system is the use of both swirling flows and staged combustion. This work reports preliminary experimental results obtained on a research burner exploiting both swirl and radially staged combustion air. The burner has been developed at Politecnico di Milano, it is composed by two coaxial co-rotating swirling jet; an inner premixed jet and an outer swirling air flow. The swirl level of the outer jet can be regulated independently form that of the inner one. Experimental results evidence the swirl level of the premixing jet strongly affects the isothermal flow field structure, the pollutant emissions and flame stability. The burner operates with low NOx emissions, anyhow a non-monotonic trend is evidenced by both CO and NOx emissions when varying the equivalence ratio (i.e. the swirl level) of the premixed jet. Further experimental analysis is required to improve the burner design and to define the best operating conditions