Experimental study of impinging flame structures and thermal characteristics in ceiling flow generated by fuel jet diffusion combustion with air entrainment constraint in a corner

Abstract

This paper presents an experimental investigation and analysis of impinging flame structures as well as thermal characteristics in ceiling flow generated by fuel jet diffusion combustion with air entrainment constraint in a corner of various angles, which had not been quantified in the literature. The impinging flame length, as well as the temperature and heat flux profile along the ceiling centerline were measured for various corner angles (from 30° to 150°), heat release rates (HRRs) and source-ceiling heights, with a total of 183 experimental conditions considered comprehensively. Experimental results show that the impinging flame behaviors have a complex variation nature with the change of corner angles. The impinging flame under the ceiling presented a particular V-shape structure. The measured impinging flame length decreases monotonously with the increasing corner angles. Then, a new global formula was proposed to predict the impinging flame length by considering the effect of corner angles and source-ceiling height on air entrainment and fuel combustion, including both before- and after- impingement stages. The temperature rise and total heat flux at a given position also decreased with the increasing of corner angles. Previous correlations based on a characteristic plume radius are not in agreement with the data for different corner angles. Then, the normalized formulas for the temperature and total heat flux decay profiles along the centerline were proposed using the total flame length as the characteristic length scale and the experimental data were better represented. The present work provides, for the first time, a general model for describing the impingement flame behavior and thermal characteristics in the ceiling flow produced by a jet diffusion combustion with air entrainment constraint in a corner of various angles.