Evaluation on Combustion Characteristics of Finishing Materials for Exterior Walls

Existing fire test methods reply on measurement of the energy released rate to identify the combustion properties of a material. However, they are inadequate when assessing combustion characteristics of a composite material characterized by vertical flame spread and different inside/outside combustion behaviors. In addition, major factors that affect the flame spread outside the building include the combustion characteristics of materials used as well as air flow around a skyscraper. However, since it is highly difficult to analyze and forecast the air flow from a fire engineering viewpoint, an investigation of the flame spread characteristics of exterior walls of a building depends primarily on the combustion characteristics of materials. Hence, this study examined, using ISO 13785-2 testing method, the temperature changes and vertical flame spread behaviors of one of the finishing materials for exterior walls--（generic ＆ fire-resistant） aluminium panels by a real-scale combustion experiment. According to the results of real-scale experiment, the maximum heat temperature of 987.7 ℃ was recorded seven minutes after the fire test was initiated while the fire-resistant aluminium panels showed the maximum heat temperature of 850.2℃ after exposed for approximately 12 min. The vertical flame spread properties put more emphasis on the time required to reach the maximum temperature rather than its magnitude and there was a five minutes difference between the materials.

Numerical Simulation of Microgravity Flame Spread Over Solid Combustibles

A computational model of three-dimensional, time-dependent flame spread in microgravity environment is presented. The solid is assumed to be a thermally-thin, pyrolysing cellulosic sheet. The gas phase model includes the full Navier-Stokes equations with density and pressure variations and six-flus model of radiation heat transfer. The solid phase model consists of continuity and energy eqllations whose solution provides boundary conditions for the gas phase equations. In the numerical procedure, the gas-and solid-phase equations are solved sepaxately and iteratively at each time step. Predictions have been made of flame spread in slow forced flow under gravitational acceleration normal to fuel surface and flame spread in a quiescent environment in an enclosed chamber under gravitational acceleration parallel to fuel surface. Numerical simulations show that, under microgravity, slow-flow conditions, flame spread process is highly unsteady with the upstream flame spreads faster than the downstream flame after a period of ignition. It has also been shown that the level of microgravity has a significant effect on the name spread process.

Flame Spread over Aviation Kerosene with an Obstacle in Liquid Phase

The phenomena of flame spread over aviation kerosene with an obstacle in liquid phase are investigated experimentally through surface temperature measurement by using infrared camera,schlieren images of subsurface flow in front of and behind obstacle and residence time of flame obtained from video recording.Experimental results reveal that obstacle has no effect on gas phase controlled flame spread.But for liquid phase controlled flame spread,flame can be stopped by an obstacle with its top edge flush with oil surface,and the residence time decreases with the increase of initial temperature of fuel.That conduction and radiation only play a subsidiary role in flame spread over liquid fuel was proved by schlieren images and surface temperature profiles.

Gas dynamics and heat transfer inside a solid propellant crack during ignition transient

To study the gas dynamic and heat transfer phenomena inside a single isolated longitudinal solid propellant surface crack,two3-D geometric models with different crack shapes were constructed.Concerning the influence of propagation of jet from the igniter on the flame spreading phenomena in the crack,flow region around the opening of the crack was also included in the above geometric models.A theoretical framework was then adopted to model the conjugate heat transfer in the combustion channel and the crack cavity.Numerical simulation results indicate that the ignition shock wave can spread into the crack cavity.Extremely high overpressure and pressurization rate were observed along the crack front.It is possible that the crack may propagate before the flame front reaches it.An ignited region located at the crack front near to the channel surface in downstream direction was generated long before the flame front reached the crack opening in both models.

Large eddy simulation of room fire spread using a medium scale compartment made of medium density fibreboard (MDF) panels

At present,there is a shortage of experimental and simulation studies on fire spread in medium-and large-scale compartments while the existing models of the fire spread are limited for typical engineering applications.This paper proposes a new model for large-scale fire spread on medium density fibreboard(MDF)panels.Validating the model with single burning item(SBI)experiments,it is found that the numerical simulation closely predicts the experimental heat release rate(HRR)with some error near the peak.The predicted heat flux and distance of lateral flame spread are consistent with the experiments and an existing model.The effects of kinetic properties and heat of combustion are identified through a sensitivity analysis.The decrease of activation energy and increase of pre-exponential factor make the MDF easier to pyrolyze and the increase of heat of combustion enhances the flame temperature and thus provide more heat feedback to the sample surface.The low activation energy(71.9 kJ/mol)and high heat of combustion(46.5 MJ/kg)of the model ensure the occurrence of flame spread.Furthermore,the model was validated using medium-scale compartment fire experiments and the results showed that the model can accurately predict the HRR after flashover(the error is within 7%).While the burner is ignited,the predictions of in-compartment gas temperature and heat flux are more accurate.However,when the burner is extinguished,the modelled in-compartment gas temperature is lower than the experimental values,resulting in a lower heat flux prediction.The model leads to easier flame spread;therefore,the modelled flame spreads faster in the compartment compared to the experiment,and thus the HRR increases more rapidly.