No abstract

A computer simulation for upward fire spread has been developed. The simulation of the fire growth and spread consists of four major components (modules): 1) preheating of the unburned fuel, 2) upward fire spread, i , e. determination of the location of the pyrolysis front, 3) pyrolysis of the material, and 4) combustion of the pyrolyz ing gases.For the heat-up and pyrolysis modules of the code, integral models have been used which accurately predict (within 1% to 2%) transient heat-up and transient pyrolysis when compared with exact analytical~olutions.The pyrolysis front location, 2 , is calculated to order (62) by taking an intercept of a straight line, cgnnecting the temperatures (real and/or virtual) of the nodes containing 2 p' with the pyrolysis temperature T p' The combustion module of the code calcUlates the heat flux distribution on the wall from the combustion of the py ro Iyz Lng gases by prov id ing expressions .for the flame he ight, 2 f' the convective, q~, and radiat i ve heat fluxes, q~, based on experimental data from the literature. The components as well as the whole algorithm of the Upward Fire Spread and Growth (UFSG) code have been compared against exact analytical solutions including transient heat-up, transient pyrolysis and flame spread.As an example, it is demonstrated that transient pyrolysis even for non-charring materials significantly affects upward fire spread rates. This result explains recent experimental data on laminar upward flame spread.In addition, a comparison of numerical predictions with turbulent upward flame spread data is made, and the results are very satisfactory.

A new, consistent and objective methodology, using a CCD camra to map flame luminosity, was applied for measuring wall b e heights. Experiments in six distinct wall configurations were conducted by simulating a wall fire via gaseous burners. The wall width was fixed at 0.4m and the burner height was set at 0. 2 5~ at 0. 5~ or at lm In a first time, the wall, 2m high, was confined by water cooled (65" C) sidewalls a) over its total height so that the flames were entraining air &om the fiond only or b) over its lower part beyond which f h~s were uncon6ned and could also entrain air sidewise. Then, the wall was unconfined over its total helght (2.5m high) and the air was entrained &om the front and at the side. Three hels were tested : methane, propane and acetylene. The present consistent and objective wall flame height measurements were essential for the development of new wall h e height correlations that include effects of burner (pyrolysis) height, wall width and confinement by sidewalls.

No abstract

We demonstrate how flame spread and fire growth can be predicted in a systematic way using a fire spread and growth (FSG) model developed at FMRC and small scale flammability measurements for PE/PVC cables in trays; this material pyrolyses in a more complicated way than a non-charring (e.g., PMMA) or a simple chamng material (e.g., particle board). Similar methodology has been applied and validated for PMMA and various types of particle board. For PE/PVC cable trays, this procedure consists of the following parts: a) standard small scale flammability measurements (i.e., time to ignition, heat of combustion, product yields) and measurements of surface temperature histories and pyrolysis rates in a nitrogen atmosphere; b) a method to deduce from these small scale measurements "equivalent" material pyrolysis properties which can be inserted in a pyrolysis model to predict pyrolysis rates in fires; and c) the FSG fire spread model which uses the properties obtained in parts (a) and (b) for predicting fire growth and critical conditions for flame spread. The present work focuses on upward f i e spread predictions and measurements for a specific 3 ft high PE/PVC cable tray.