Fire spread and flame shape

In laboratory tests, the size of a flame front can significantly affect the rate of fire spread. The configuration factor of a given flame shape provides a method for relating flame fronts of various widths. The author discusses an analog system for determining the configuration factor of an irregularly shaped flame and the effects of flame width and height on the rate of spread.     

Fire exposure to exterior walls and flame spread on combustible cladding

A segment of the on-going research program on fire spread via exterior walls conducted at the Institute for Research in Construction of the National Research Council of Canada is described. The research includes full-scale experimental studies of fire exposure to exterior walls, fire hazards associated with the use of combustible materials, and the development of new test methods for assessing the flammability of combustible cladding. Correlations between the results of a new full-scale test and standard flame spread tests (Steiner tunnel test, radiant panel test, roof deck test) were investigated. A prototype of a reduced-scale test, the vertical channel test, is described. It was found that, at present, the full-scale test is the most appropriate method to evaluate the fire hazards of combustible wall assemblies.     

Fire resistance of barriers in modelling fire spread

This communication examines the findings from a survey of fire tests carried out in New Zealand. The survey compares the quoted Fire Resistance Ratings with the times at which the structures actually failed for different failure criteria. In particular, the differences between insulation and integrity failure for light timber-framed structures are discussed. The apparent imbalance between possible failure modes has implications for those involved in the analysis of structural fire safety.     

Fire spread experiment across Mediterranean shrub: Influence of wind on flame front properties

A fire spread experiment was conducted in the field under wind-blown conditions. The fuel consists of tall and dense Mediterranean shrub vegetation. The plot area was about 30 m wide and 80 m long. This experiment was conducted not only in order to increase the knowledge and understanding of the fire behaviour in the field but to provide data for the validation of physics based models of fire spread. In particular, the effects of wind on the geometric and thermal properties of the flame front in the field were investigated. The flame temperature along the vertical direction and the radiation emitted ahead of the flame front, were measured. The methodology employed in this experiment and some quantitative measurements of wind velocity and direction, flame geometric properties, are also presented and discussed. The measurements and observations exhibit that the behaviour of the fire and the flame structure character are very different from the one encountered at laboratory scale. These preliminary results show that large scale turbulence influence fire spread and affects the flame shape, temperature and radiation emission.     

On the flame height definition for upward flame spread

Flame height is defined by the experimentalists as the average position of the luminous flame and, consequently is not directly linked with a quantitative value of a physical parameter. To determine flame heights from both numerical and theoretical results, a more quantifiable criterion is needed to define flame heights and must be in agreement with the experiments to allow comparisons. For wall flames, steady wall flame experiments revealed that flame height may be defined by a threshold value on the wall heat flux. From steady wall flame measurements, three definitions of flame height from wall heat flux are retained: the first is based on the continuous flame while the two others are based on threshold values of 4 kW/m² and 10 kW/m². These definitions are applied to determine flame heights from a two-dimensional time-dependent CFD model used to describe flame spread on a vertical slab of PMMA. Results show that the predicted flame heights are consistent with the available data of the literature. Defining flame height by threshold values on the wall heat flux of 4 and 10 kW/m² allows the correlation of the wall heat flux in terms of (x−x_p)/(x_fl−x_p), which is the dimensionless characteristic length scale for upward flame spread. It is also found that the continuous flame is not a characteristic length for the heat transfer to the unburnt fuel and is not really appropriate to define flame height in upward flame spread.     

Width effect on upward flame spread

One previous experimental study has reported a width effect for upward flame spread rate on thermally thin fuels. A similar effect is expected for thermally thick fuels. This study revisited this topic by developing a hypothesis and performing experiments with sidewalls using 18 mm thick, 1000 mm tall PMMA slabs of widths 100, 200, 300, 500 and 700 mm. In the hypothesis, a lateral diffusion throughout the flame width was proposed to cause thicker flame along its centerline for wider flames and enhance combustion efficiency. Higher heat release rate per unit width, larger flame height, higher flame temperature and more heat feedback to the surface were consequently present. The corresponding flame spread rate was also increased and a power value of 0.35 existed between the flame spread rate and width in this study. All the experimental results clearly supported the hypothesis.     

Upward flame spread on composite materials

Three existing models of upward flame spread were tested against intermediate-scale experiments on a vinyl ester/glass composite. Characterization of rate of heat release per unit area, needed as input to the models, was obtained at external radiant fluxes below the minimum for ignition by adaptation of a method due to Kulkarni. There are several limitations on the accuracy of the material characterization when applied to composites. Each of the flame spread models has definite limitations as well. Nevertheless, all three models produced predictions of spread behavior in sufficiently quantitative agreement with the experiments that they should prove useful for engineering analyses of flame spread potential.     

A test to grade horizontal flame spread

A small-scale test has been developed to determine the critical radiant flux to cause a flame to spread from a small ignition source on horizontal specimens.     

A simplified method for determining flame spread

The author discusses a small-scale fire test, which he proposes be used to determine flame-spread ratings for plastics during the development stages. Data on certain cellulosic materials indicate good correlation with the 25-ft tunnel test. Note: Based on a paper delivered by the author at the 22nd Annual Technical Conference of the Society of Plastics Engineers, March 12, 1966. At the time of the paper’s presentation, Mr. Levy was employed by the Pittsburgh Corning Corporation. He is currently with the Pittsburgh Plate Glass Company.     

Fire spread tests—A critique

Propagation is perhaps the most alarming characteristic of a fire. Rate of advance is an extremely important factor in determining the likelihood of escape from a burning building and the ability of fire protection systems to protect property.     

Part I Ignition temperatures and flame spread rates

Part I of this two-part report deals with the effects of oxygen enrichment on ignition temperatures and flame spread rates of materials that might be found in hospital hyperbaric chambers. Part II will be carried in the November issue. Increased use of oxygen-enriched atmospheres in medicine, undersea exploration, and the space program (twice with tragic results) has caused attention to be focused on the effects of oxygen enrichment on the flammability of, materials. Note: This paper is based on research sponsored by the U.S. Public Health Service, Department of Health, Education and Welfare, under Appropriation 7560370. Reference to specific brandse is, made for identification only and does not imply endorsement by the Bureau of Mines.     

某美术馆展厅火灾蔓延分析研究

以北京某美术馆为实例,通过对其工程特点、火灾规模等多方面进行深入的研究和探讨,合理选择出适用于该项目的辐射蔓延的评估方法和理论模型,完成了美术馆展品火灾蔓延的分析研究。     

Fire spread potential of ABS plastic plumbing

ABS pipes and fittings are gaining popularity as components of drain, waste, and vent installations in plumbing systems. In case of fire, will they contribute a significant amount of smoke? Will they be a source of fire spread?     

成束PVC电缆全尺寸火蔓延实验研究

对最常见的PVC电缆进行了全尺寸实验研究.通过测量电缆的炭化长度及电缆表面的温度研究火蔓延的情况,同时将火蔓延与火灾过程中的重要参数(如热释放速率、烟气释放速率)进行了比较,对影响电缆火蔓延的因素进行了分析.研究发现,PVC电缆的火蔓延过程可分为两类:一类可以维持火焰传播,另一类在离开点火源后火焰逐渐熄灭;影响电缆火蔓延的关键因素为电缆的排布方式,当电缆为间隔排列时,火焰可以维持传播,当电缆为紧密排列时,火焰在电缆束中段熄灭;电缆束宽度和点火源功率对电缆火蔓延的影响很小.     

Real-time wildland fire spread modeling using tabulated flame properties

This paper is an extension of previous papers [1], [2] on a raster-based fire spread model which combines a network model to represent vegetation distribution on land and a physical model of the heat transfer from burning to unburnt vegetation items, and takes into account local conditions of wind, topography, and vegetation. The physical model, still based on the unsteady energy conservation in every fuel element and detailed local and non-local heat transfer mechanisms (radiation from the flaming zone and embers, surface convection, and radiative cooling from the heated fuel element to the environment), now includes wind-driven convection through the fuel bed. To address the challenge of real-time fire spread simulations, the model is also extended in two ways. First, the Monte Carlo method is used in conjunction with a genetic algorithm to create a database of radiation view factors from the flame to the fuel surface for a wide variety of flame properties and environment conditions. Second, the front-tracking method, drafted in [2], is extended to polydisperse networks and implemented in the new version of the model, called SWIFFT. Finally, the SWIFFT model is validated against data from different fire scenarios, showing it is capable of capturing the trends observed in experiments in terms of rate of spread, and area and shape of the burn, with reduced computational resources.     

浅谈船用饰面材料的低播焰性能

低播焰性能是船用饰面材料燃烧性能的一项重要指标，所有材料都应满足IMOA．653标准的规定要求。着重从检验角度介绍了船用饰面材料低播焰性能的检测依据、试验装置、试验原理、试验程序，以及对其中存在的一些问题进行了探讨。     

Fire spread and smoke control in high-rise fires

Based on experience gained in the Henry Grady Hotel smoke and fire tests, the authors have formulated some recommendations for the improvement of future full-scale fire experimentation.