Effects of elliptic co-flow on the structure of a turbulent diffusion flame

Abstract

The effects of elliptic co-flow on the structure of a turbulent propane diffusion flame have been presented. The interaction of the fuel jet and coflow shear layer enhances the mixing behavior of the flow-field, which tends to improve the combustion characteristics of diffusion flames. Non-axisymmetric exit jet geometries are characterized by better mixing and increased fluid entrainment. Better mixing results in higher fluid entrainment in the jet core, which is desirable for the low pollution from a diffusionally controlled combustion environment. In the present study, the interaction of an elliptic jet co-flow with a propane jet flame issued from a circular tube burner has been studied. Pollutant emission, flame radiation, flame structure, and soot concentration have been measured. The exit Reynolds number of the fuel jet is 5670 and the exit Reynolds number for the coflow is 2700 based on the minor diameter. The results are compared with the measurements from the experiments in a circular co-flow which is the base line condition for the present study. The pollution characteristics and the flame structure of the flame in the elliptic co-flow are significantly different from those in the circular coflow. The NO emission is higher and the CO emission is lower in the elliptic co-flow. Elliptic co-flow flame produces less soot than circular co-flow flame. The elliptic co-flow jet grows quicker than that of circular co-flow and the center line velocity decay is more rapid in elliptic co-flow flame C dcfc E El r Ucf Uj w X NOMENCLATURE Circular co-flow Circular co-flow jet diameter Elliptic co-flow Emission Index (g/kg of fuel) Radial distance Co-flow jet exit velocity Fuel jet exit velocity Soot concentration (g/cc) Axial distance