Investigation on the Effect of the Burner Outlet Configuration on the Combustion Characteristics of a Swirl-premixed Burner

This study investigated the effect of the outer recirculation zone(ORZ) on the combustion characteristics and NOX emissions. Numerical simulation and experimental test were conducted for the combustors with two types of the burner outlet. The ORZ is formed conspicuously for a flat type with sudden expansion outlet while it is formed in a negligible size for a curved type with gradual expansion outlet. In a higher adiabatic flame temperature(AFT) condition of 2020 K, the NOX emission of the flat type is increased by 19% compared with the curved type as the ORZ has long residence time and high temperature enough to produce the thermal NOX. On the other hand, the NOX emission of the flat type is decreased slightly in a lower AFT of 1850 K as the temperature of the ORZ is not high enough to significantly produce the thermal NOX. The tendency of the calculated NOX emission is consistent with the experiment results.