Transport in Turbulent Jet Diffusion Flames With Annular Counterflow

Abstract

The present study deals with the augmentation of the turbulent shear effect on transport in turbulent jet diffusion flames due to the presence of air-suction flow and the possibility of extending the flame blow-off limits through augmentation. The experimental apparatus employed here comprises a fuel nozzle placed at the center of a concentric annulus with an outer cylinder encompassing the nozzle. The fuel jet is allowed to eject upwards and turbulent jet diffusion flames are formed by igniting the jet, then by increasing the volume flow rate of the fuel. The annular counterflow technique was employed to augment the turbulent shear effect. It is found that (1) the augmentation of turbulent shear effect exerted on the shear layer formed between the jet flames and the opposed flow of air causes an increase in temperature of the cold fuel gas at the flame center and an extension of flame blowoff limits; (2) flame lift-off heights are suppressed; (3) the lift-off propensity of the diffusion flame is alleviated by such augmentation.