Experimental Investigation of Flame Appearance and Temperature Distribution of a Double Elliptical Inverse Diffusion Jet Flame

Abstract

Abstract The use of elliptical jets for combustion control is an attractive passive technique due to their ability to induce flow perturbation, fluid entrainment, and jet shearing. This study presents an experimental investigation of inverse diffusion jet flames emanating from a double elliptic burner with a central circular air stream. The inner and outer streams are fed with air, while the middle one is fed with liquefied petroleum gas (LPG) as fuel. The impact of the inner-to-outer air ratio and outer elliptical tube angle on flame appearance and mean in-flame temperature was examined at a constant total air flow rate and fixed thermal input. Flame visual and thermal structures are analyzed through shadowgraph and temperature measurements in both major and minor planes of the inner elliptic fuel tube. The results reveal a dual-flame structure for all flames, with longer flames resembling normal diffusion flames as the outer air percentage increases. The outer elliptic tube angle has a minor effect on the flame length and centerline temperature, while increasing the angle enhances air/fuel mixing, as indicated by the decrease in luminosity due to the two elliptical jets' interaction.