Combustion performance of triple flames issuing from elliptical Swirlers

摘要

An experimental work has carried out to characterize the combustion performance in terms of flame length, temperatures and emissions for a triple flame structure of concentric fuel rich mixture surrounded by fuel lean mixture premixed flame combined with the cross flow stream. A set of elliptical double swirlers of different angles and aspect ratios were compared to a circular double Swirler was used to investigate the effect of swirling direction modes (co-versus counter swirl), the effects of swirl angles, and ellipticity. It was found, for counter and co-swirl, that counter swirler leads to higher enhancement of combustion process than co-swirler, due to higher levels of premixing, slight differences in the flame length were found. The counter swirl induces higher levels of turbulence than co-swirl with the consequent enhancement in the mixing of the mixtures and reducing the flame peak temperatures thus decreasing NO_x, by 36%, and CO, by 29%, emissions comparison to that of the co-swirl. In addition, increasing the inner swirling angle shortens the flame length. Increasing the inner swirl favorably produces flames of higher average temperatures and lower emissions of CO and NO_x emissions. In this scene, it was found that the elliptic swirl of (45°i, 30°o) produces higher flame temperatures and lower emissions concentrations of NO_x, by 38%, and CO, by 10%, than that for the elliptic swirl of (30°i, 45°o). Furthermore, it was found that the elliptic swirl shows shorter flame length than circular swirler, while the elliptic swirl of AR=1.25 produces the shortest flame length relative to other Swirlers of different aspect ratios. The effect of the ellipticity was noticeable, since it was found that the elliptic swirl of AR=1.25 produces flame of higher temperatures and lower NO_x emission than any other Swirlers of different aspect ratios. Increasing the aspect ratio leads to decrease the concentrations of CO emission. Finally, it was concluded that double circular swirl produces higher CO and NO_x than double elliptic swirl.