Effects of side walls on facade flame entrainment and flame height from opening in compartment fires

¹ State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei, Anhui 230026, China
² FireSERT, School of Built Environment and Built Environment Research Institute, University of Ulster, Newtownabbey BT38 8GQ, Northern Ireland

Abstract

This paper presents an investigation of the side wall effects on facade flames ejected from the opening (such as a window) of an under-ventilated room fire. Experiments are carried out in a reduced-scale experimental setup, consisting of a cubic fire compartment having an opening with a vertical facade wall and two side walls normal to the façade wall. By changing the distance of the two side walls, the facade flame heights for different opening conditions (width, height) are recorded by a CCD camera. It is found that as the distance of the two side walls decreases the behavior the flame height can be distinguished into two regimes characterized by the dimensionless excess heat release rate, $\mathrm{See\; Formula\; in\; PDF}$, outside the opening: (a) for the “wall fire” ($\mathrm{See\; Formula\; in\; PDF}$ ≤ 1.3 ), the flame height is shown to change little with decrease of side wall distance as the dominant entrainment is from the front direction (normal to the facade wall) independent of the side wall distances; (b) for the “axis-symmetrical fire” ( > 1.3), the flame height increases significantly with a decrease in side wall distance as both the entrainment from the two side directions (parallel to the facade wall) and that from the front direction (normal to the facade wall) together apply. A global physically based non-dimensional factor K is then brought forward based on the side wall constraint effect on the facade flame entrainment to characterize the side wall effect on the flame height, by accounting for the dimensionless excess heat release rate, the characteristic length scales of the opening as well as the side wall separation distance. The experimental data for different opening dimensions and side wall distances collapse by using this global non-dimensional factor.