Diffusion Flames of Gas Jets Issued From Circular and Elliptic Nozzles

Abstract

An experimental study of the characteristics of the burning and nonburning gas jets issued from elliptic and circular nozzles in a low velocity concentric air stream is presented. Propane mixed with nitrogen was used as the jet fluid. The diameter of the circular nozzle was 9.5 mm and the elliptic nozzle had the same exit area as that of the circular nozzle and an aspect ratio (major axis/minor axis) of 3:1. The liftoff and reattachment behavior, temperature profiles, concentration profiles of fuel, oxygen, carbon dioxide, carbon monoxide, nitric oxide, and soot, flame radiation, opacity of the flame samples, the profiles of the streamwise component of the mean velocity, and r.m.s. value of the velocity fluctuation in the streamwise direction were measured. The elliptic nozzle flames were found to have lower flame stability, higher temperatures, lower soot concentration, and lower flame radiation than those of the circular nozzle flames. The nitric oxide concentration in the mid-flame region was higher in the elliptic nozzle flame. However, the nitric oxide concentration in the far-nozzle region was not significantly different in the flames of the circular and elliptic nozzles. Flow visualization pictures of the flames in the vicinity of the circular and elliptic nozzles are also presented.