Effects of Atomization Condition on Flame Structure and Emission Characteristics of Burning Rich-Premixed Spray Jets

Flame structure and emission characteristics of burning premixed spray were experimentally studied for different atomization conditions. Two combustion modes with and without an internal flame were observed. As Sauter mean droplet diameter became larger than a specific value, the internal flame appeared inside the external group flame. The existence of the internal flame was affected by the equivalence ratio of premixed spray jet, too. As Sauter mean droplet diameter was increased, the average flame height increased but the average blue-flame height decreased. These tendencies were same for different equivalence ratios of premixed spray jet. As the equivalence ratio of premixed spray jet was increased, the average flame height increased but the average blue-flame height did not vary very much. Exhaust emission characteristics were also affected both by Sauter mean droplet diameter and the equivalence ratio of premixed spray jet. As Sauter mean droplet diameter was increased, the emission index of CO (EICO) increased. EINO took maximum at Sauter mean droplet diameter of about 60 μm ∼ 80 μm. These tendencies in terms of Sauter mean droplet diameter were same for different equivalence ratios of premixed spray jet. EICO concentration showed low values without the internal flame.