Geometrical characteristics of externally venting flames: Assessment of fire engineering design correlations using medium-scale compartment-façade fire tests

Abstract

In a fully developed under-ventilated compartment fire, flames may spill out of external openings (e.g. windows); Externally Venting Flames (EVF) pose a significant risk of fire spreading to adjacent floors or buildings. The main aim of this work is to comparatively assess a range of fire engineering design correlations used to describe the external dimensions of the EVF envelope. The predictive accuracy of each correlation is evaluated through comparison with experimental data obtained in a medium-scale compartment-façade fire facility, using typical fire loads suggested in the Eurocode. A series of fire tests is performed, employing a ¼ scale model of the ISO 9705 room, equipped with an additional extended façade. An "expendable" fuel source (n-hexane) is utilized to effectively simulate realistic building fire conditions. An extensive sensor network is used to monitor the dynamic behaviour of a broad range of important EVF physical parameters and a dedicated image processing tool is developed to allow estimation of the EVF envelope main dimensions (e.g. height, width, projection). Digital camera imaging is used to determine the main geometrical characteristics of the EVF envelope. Comparison of fire engineering design correlation predictions with experimental data reveals that correlations for the estimation of EVF height err on the safe side in under-ventilated fire conditions; decreasing the fire load results in under-prediction of EVF height and projection. It is shown that EVF projection and width strongly depend on both excess heat release rate and height. In addition, the necessity to derive appropriate criteria for the identification of the EVF projection is demonstrated. The obtained extensive set of experimental data, covering three different fire load levels, can be also used to validate numerical simulation tools or evaluate the accuracy of other available fire design correlations.

Effects of static pressure, pressurization, and depressurization on n‐heptane pool fires in an airplane cargo compartment

“…For the ventilation under dynamic pressure, some previous studies have proved that the abundance of ventilation is able to active the combustion and increase the MLR . The general explanation is that the air flow over the fuel surface steepens the concentration and temperature gradient of fuel vapor.…”

Thermal characteristics of externally venting flames and their effect on the exposed façade surface

“…windows) in case the glazing fails. Fire compartment and opening geometry and the prevailing ventilation conditions are the most significant parameters influencing the EVF geometric and thermal characteristics [5,6,13,15,18,19,25]. During the initial stages of the fire, compartment geometry is important since enclosure dimensions are decisive on how close the initial fire is located in relation to other combustible materials, ventilation openings and compartment boundaries.…”

“…In this context, the main aim of this work is to investigate the fundamental thermal phenomena governing EVF development and their impact on façade systems. Motivated by an increasing number of recent reports [4,5,6] suggesting that existing engineering design methodologies cannot describe with sufficient accuracy the thermal characteristics of EVF, this work emphasizes on the assessment of empirical correlations and design methodologies used to describe EVF and their impact on façade systems. Focusing on the thermal characteristics of EVF that affect the fire safety of a façade system, namely the EVF centreline temperature (Tz) and the EVF-induced heat flux to the façade (q"), the predictive accuracy of various design correlations is evaluated by means of comparison with medium-and large-scale fire tests conducted by the authors and found in literature.…”

Experimental study on vertical temperature profile of buoyant window spill plume from intermediate‐scale compartments

“…A mathematical model on lateral temperature profile of buoyant window spill plume from a compartment fire was reported by using a 0.8‐m cubic fire compartment with window opening varied from 0.20 m (H) × 0.30 m (W) to 0.35 m (H) × 0.35 m (W), and heat release rate (HRR) differed from 128.3 to 244.4 kW . The geometrical characteristics of externally venting flames was discussed by using a 0.60 m (L) × 0.90 m (H) × 0.60 m (W) fire compartment with window opening 0.20 m (H) × 0.50 m (W), and HRR varied from 79 kW to 233 kW . Among the researches on wall temperature distribution emerging from the opening of a fire compartment, the typical correlation between dimensionless temperature Θ and vertical position z was first proposed by Yokoi and recently reexamined by Lee and Delichatsios .…”