Lateral Flame Spread Research Articles

Characterization of Flame Spread Over PMMA Using a Temperature Reconstruction Method

ABSTRACT The contribution of heat transfer mechanisms for different configurations of opposed flow flame spread on cast PMMA is presented. Three opposed flow flame spread scenarios are considered, each in a quiescent atmosphere: downward spread on a vertical surface, buoyant horizontal spread (i.e. a pool fire-type spread), and lateral spread along a vertical surface. Video analysis and temperature measurements were used to determine flame spread rates; average flame spread rates were found to be 2.67, 2.54, and 3.54 mm/min for downward, horizontal, and lateral spread, respectively. These differences result from the varying magnitudes of the heat transfer mechanisms (e.g. gas-phase heat transfer and conduction through the solid) due to the changes in the flame characteristics. Past studies have investigated these regimes of flame spread, but have not directly compared experiments from the configurations used here to identify the relative importance of each heat transfer mechanism. Using temperature measurements, the thermal gradient, and hence conductive heat fluxes through the solid, were quantified. This allowed the different rates of heat transfer to be compared across each configuration. Downward and horizontal flame spread displayed similar flame spread rates and similar heat transfer contributions for both the gas phase and solid phase. However, lateral flame spread displayed characteristically higher rates of gas-phase heat transfer compared to downward and horizontal.

Fire Protection of Wood and Structures with Mineral Paints

The paper presents the results of fire tests of mineral paint for wood and structures based on it. Mineral paint tests were carried out in accordance with the EN 13823: 2010 + A1: 2014 (SBI method) procedure, namely: the rate of heat release, smoke generation, total heat release, total smoke generation, indices of ignition rate and smoke content were determined. It has been established that mineral paint is characterized by non-combustibility, absence of flaming particles and droplets, burning droplets; lateral flame spread to the edge of the substrate. Mineral paint, during the fire test, has low heat generation, smoke generation and combustion rate. The indicated indicators are achieved due to the compositional composition of the mineral paint and primer, as well as the mechanism of their action.

CFD Simulations of Fire Propagation in Horizontal Cable Trays Using a Pyrolysis Model with Stochastically Determined Geometry

In this paper, a pyrolysis model for a PVC cable is constructed using results from thermogravimetric analysis, microscale combustion calorimeter and cone calorimeter experiments. The pyrolysis model is used to simulate fire propagation in horizontal cable trays. The simulated arrangement corresponds to a cable tray fire experiment from OECD PRISME 2 project. As laying the cables loosely along the horizontal trays is a random process, a novel stochastic method is developed for making the simplified cable tray geometries for the computational fluid dynamics model. In addition, as the simplified cable tray geometry has significantly smaller surface area than a real tray full of cables, the surface area was parametrically adjusted. In contrast to most of the earlier published numerical approaches for simulating cable tray fires, the presented approach does not use empirical correlations for predicting fire propagation and does not require any results from full-scale experiments for calibrating the model. The simulation results are compared to experimental results in terms of heat release rate, mass loss, tray ignition times and lateral flame spread rates. The maximum heat release rate was overpredicted by 8% on average.

Durable flame-retardant behavior of cotton textile with a water-based ammonium vinyl phosphonate

A novel coating system for fabricating durable flame-retardant cotton textiles was invented based on halogen-free water-based ammonium vinyl phosphonate (AMVP) via a dip-dry-cure process. The flame retardant was not only reacted with cellulose through P-O-C covalent bond but also prevented the acid brittleness of cotton fibers. The prepared fabrics have shown excellent flame retardance, good hand feel, and durability. The limiting oxygen index (LOI) value of the AMVP treated cotton fabric with the weight gain value of 13.6% was 36.7% while the LOI value of the fabric still has remained 27.3% after 50 washing cycles. It can still be self-extinguished without any lateral flame spread. The cone calorimetry results showed that the peak heat release rate (PHRR) and the total heat release (THR) of AMVP treated cotton were 87.36% and 48.94%, respectively, lower than that of control cotton. All results of thermal degradation behavior, pyrolysis products, the morphology, and chemical components of the charred residue revealed that AMVP coating altered the thermal decomposition pathway of the treated cotton. It induced the formation of a stable char layer rather than flammable gases, which results in the excellent physical barrier retarding the heat flux and flame. Furthermore, the whiteness and softness of the AMVP treated cotton were sustained well, although the tensile strength and breaking elongation of cotton fabrics had a slight decrease.

Reconstruction of the Grenfell Tower fire – Part 4: Contribution to the understanding of fire propagation and behaviour during horizontal fire spread

SummaryThe tragic events at Grenfell Tower in 2017, involving a combustible façade system, have raised concerns regarding the fire risk that these systems pose. In this series of articles, so far published, fire development inside the initial apartment has been investigated using an appropriate computational fluid dynamics (CFD) model. Several scenarios including different fire sources and ventilation conditions were addressed. Fire propagation through the window to the external façade and to higher apartments was modelled. This model was validated by comparing the numerical results with the visual observations reported in the Grenfell Inquiry. A CFD model of the complete east face of the Grenfell Tower was then created. This paper details CFD modelling of the complete Grenfell Tower façade during the late horizontal phase of fire spread. As the physics of lateral flame spread is different from that for upward flame spread, it is important to assess the validity of the model, thus far developed, for this configuration. Fire propagation over the whole façade is modelled and compared with observations from the real disaster. This provides a better understanding of its fire behaviour and of the contribution of architectural details and their impact on fire spread.

Influence of Wind Direction on Fire Spread on the Exposed XPS insulation Wall

Medium-sized wall fire experiments were carried out using extruded polystyrene (XPS) panels to build an insulation layer to simulate the flame spread over the exterior thermal insulation system during the exposed stage. During the experiments, the influences of the wind direction on the lateral and vertical flame spread speed without fire barrier designs under the wind speed of 2.5m/s were studied quantitatively and qualitatively. According to the experimental results, it is found out the averaged peak lateral flame spread rate increases and the averaged peak vertical flame spread rate decreases when the angle between the wind direction and the wall increases from 0° to 60°. It can be seen from the analysis that the largest average lateral flame spread rate and the largest average vertical flame spread rate also show regular changes at same wind direction. This study results can provide valuable references for optimizing the fire safety design of exterior insulation system.

Lateral Flame Spread over PMMA Under Forced Air Flow

In wildland and other flame spread scenarios a spreading fire front often forms an elliptical shape, incorporating both forward and lateral spread. While lateral flame spread is much slower than forward rates of spread, it still contributes to the growth of the overall fire front. In this work, a small-scale experiment is performed to investigate the mechanisms causing this lateral spread in a simple, small-scale configuration. PMMA strips with thicknesses ranging from 1 mm to 3.1 mm and widths of 5 cm and 10 cm were ignited under forced flow in a laminar wind tunnel. Unlike traditional concurrent or opposed flame spread experiments, flames were allowed to progress from one side of the sample to the other, perpendicular to the wind direction. An infrared camera was used to track the progression of the pyrolysis front by estimating the surface temperature of the PMMA. The flame spread rate, depth of the burning region, thermal diffusion length, and radiant heat flux were determined and analyzed. Based on a theory of heat and mass transfer for a laminar diffusion flame, a thermal heat transfer model was developed for the preheating region to predict the lateral flame spread rate. Results show that the thermal diffusion length decreases with wind velocity, ranging from 4.5 mm to 3 mm. Convection dominates the flame-spread rate, accounting for more than 80% of the total heat flux. The theoretical flame spread rate agrees well with experimental data from all but the thinnest samples tested, overpredicting the lateral flame spread rate for 1 mm thick samples. The resulting model for lateral flame spread under concurrent flow works for forced-flow dominated flame spread over thermally-thin fuels and helps provide physical insight into the problem, aiding in future development of two-dimensional, elliptical fire spread models.

Effects of ceiling inclination on lateral flame spread over vertical Poly(methyl methacrylate) surface

A series of experiments was designed to investigate the effects of ceiling inclination on lateral flame spread over vertical poly(methyl methacrylate) (PMMA) surface. PMMA slabs with width ranged from 3 cm to 9 cm were tested at the ceiling inclination from 30° to 90°. Burning rate, flame spread rate, and flame appearance were investigated experimentally. The results suggest that in the cases of narrow PMMA slabs, the flame spread rate presents a “U” variation with the increasing ceiling inclination. But flame spread rate of wider slabs decreases with ceiling inclination. Burning rate follows a power-law change with the sample width, which is m˙/W∝W0.136−0.421sin(α). And the exponential relationship between pyrolysis length, sample width and ceiling inclination can be given as xp∝W0.455−0.16sin(α).

Application of Narrow-Spectrum Illumination and Image Processing to Measure Charring in Lateral Ignition and Flame Spread Tests

Application of Narrow-Spectrum Illumination and Image Processing to Measure Charring in Lateral Ignition and Flame Spread Tests

Study of the importance of non-uniform mass density in numerical simulations of fire spread over MDF panels in a corner configuration

The distribution of mass density through the thickness of Medium Density Fiberboard (MDF) panels is known to be non-uniform. A few studies have previously investigated the influence of this non-uniform through-thickness density distribution on the thermal behavior of MDF panels in small-scale tests. This study assesses the significance of this material property on flame spread simulations in a medium-scale set-up, namely that of Single Burning Item (SBI) corner fire tests. Simulations are performed using FireFOAM 2.2.x, considering both uniform and non-uniform MDF material density profiles, using model-effective material properties determined from bench-scale pyrolysis tests conducted in a Fire Propagation Apparatus (FPA). The heat transfer from the gas phase is modeled by means of empirical expressions with adjusted parameters. The simulations are assessed against the results of several SBI experiments with MDF panels and a test with Calcium Silicate (CS) panels. When the non-uniform nature of the through-thickness density is taken into account, the fire growth prediction in terms of the total Heat Release Rate (HRR) is considerably different (20% higher peak HRR), mainly due to the characteristic high peak mass loss rate at the initiation of pyrolysis of MDF material, resulting from the higher mass density near the surface of the panels. Furthermore, total heat fluxes on the panels, lateral flame spread, surface pyrolysis and through-thickness char formation visibly depend on the non-uniform distribution of mass density, particularly in regions further away from the corner where the influence of thermal attack from the burner is less dominant. A new diagnostic is proposed for determining the pyrolysis front location and spread on the surface of the charring panels.

The Impact of Mounting Method on the Flammability Testing of Chlorinated Poly Vinyl Chloride (CPVC) Pipe Type Certification for Maritime Applications

A series of tests was performed to elucidate the impact of the mounting methods on the performance of chlorinated poly vinyl chloride (CPVC) pipe in accordance with International Maritime Organization Fire Test Procedures Annex 1 Part 5. Also assessed, was the determination whether the current practice in type approval for the certification of all CPVC pipe sizes between smallest diameters, thinnest pipe tested and largest diameters, thickest pipe tested is a valid practice. Whole diameter pipe and pipe cut in half longitudinally were tested in the Lateral Ignition and Flame-Spread Test apparatus to determine if the different configurations of the pipe induced variability. A total of 42 tests were performed to look at sizes 12.7-mm copper tube size (CTS) through 38.1-mm Schedule 80 CPVC pipes. The following factors produced statistically different data at the 99% confidence limit: longitudinally half cut, versus whole, of the same pipe size and type, and thickness of the pipe for both total heat release and peak heat release rate (PHRR). Thickness is important with thicker pipe performing better in the testing. Whole pipe of the thinner material, CTS, versus the same pipe produced from longitudinally cut pipe, increased the heat produced significantly by holding the pipe in the combustion zone longer. Thin cut pipe appeared to melt and char, and fall out of the sample holder and the combustion zone, effectively reducing the mass consumed and energy produced. For Schedule 40 pipe of whole smaller pipe diameters, 12.7 mm, performed significantly better for both PHRR and total heat release than the longitudinally cut pipe. For diameters of 19.1 and 38.1-mm Schedule 40, the same trend was noted with the whole pipe performing significantly better. Thicker materials, such as Schedule 80, develop a thick char layer that stayed in place reducing combustion of CPVC.

Development and Evaluation of a Water-Based Flame Retardant Spray Coating for Cotton Fabrics.

In this Research Article, we report on the development of water-based flame retardant coating based on phospho-nitrogen combination for cotton fabrics. A one-step spray-on process was employed to coat the fabrics by taking advantage of the spontaneous reaction between para-phenylenediamine (PDA) and tetrakis(hydroxymethyl)phosphonium chloride (THPC) resulting in an instantaneous precipitation of poly[1,4-diaminophenylene-tris(dimethyl hydroxymethyl)phosphine] (PApP) on the fabric surface. The effectiveness of PApP in improving the flame retardant properties like ignition resistance and lateral flame spread were evaluated in accordance with ASTM D6413 and BS EN ISO 15025 flammability tests. Despite the early (thermal) decomposition onset for coated fabrics under both oxidative and pyrolytic conditions, remarkably, self-extinguishing behavior (<3 s) without any lateral flame spread was observed. Possible reaction scheme was also proposed to correlate flame retardant mechanism of the coated fabrics with the observations. Additional analysis via pyrolysis combustion flow calorimetry and vertical flame testing before and after washing showed that flame retardant efficiency did decrease with washing, but the overall performance was still promising.

Effectiveness of vertical barriers in preventing lateral flame spread over exposed EPS insulation wall

Insulation panels made of organic, combustible materials are frequently used in the exterior thermal insulation systems (ETIS) for buildings. Such combustible insulation panels have been involved in several catastrophic building fires in recent years in China. One potential strategy to mitigate this fire hazard is to limit fire spread over the ETIS. The present work evaluates the effectiveness of vertical fire barriers in inhibiting fire spread over exposed insulation walls made of expanded polystyrene (EPS) panels. Reduced-scale experiments were carried out indoors using EPS panels with or without two vertical barriers made of non-combustible mineral wool, the fire started at the bottom center of the middle panel. The interval and width of the barriers were varied systematically, while the temperature distribution on the wall, the radiation heat flux from the fire, and the infra-red (IR) images were recorded. To demonstrate the validity of the concept, an outdoor, full-scale experiment was carried out using a 7-floor building. Our reduced-scale experiments showed that the installation of two vertical fire barriers successfully stopped the lateral flame spread, decreasing the peak temperatures of the two side panels by about 300°C for all barrier configurations tested. When barrier width was fixed at 5cm, an increase of the barrier interval from 30 to 90cm led to increases in the peak temperatures, radiation heat flux, and the maximum rate of upward flame spread. By contrast, when barrier interval was fixed at 90cm, an increase of the barrier width from 2 to 5cm had little influence on the combustion dynamics of the middle panel but the peak temperature on the side panels dropped, consistent with the smaller heat transferred with wider fire barriers. In the regions of the side panels next to the barriers, pyrolysis and deformation could be observed with barrier widths of 2 and 3cm, but not 5cm. Finally, our outdoor, full-scale experiment demonstrated that a 30cm wide vertical barrier made of air-filled cement successfully stopped the lateral flame spread over exposed EPS wall. The study highlights the effectiveness of vertical fire barriers in preventing the lateral flame spread over the exposed EPS insulation wall and provides another option for enhancing the fire safety of the combustible insulation systems.

Large-scale fire suppression modeling of corrugated cardboard boxes on wood pallets in rack-storage configurations

In this study, the fire growth and suppression models in FireFOAM were validated for rack-storage commodities consisting of two solid fuels, namely corrugated cardboard boxes and hardwood pallets, which are referred to as Class 2 commodity. Validation experiments included two fire-growth and two fire-suppression configurations with different rack-storage array heights (3 and 5 tiers). In the suppression study, standard-response upright ceiling sprinklers (K-factor of 160lpm/bar1/2) were used. The time-resolved chemical heat release rates obtained from the experiments were used to validate the fire growth model. The observed sprinkler activations and fire-spread patterns were used to validate the suppression model. This study identified that lateral flame spread is primarily enabled by flames impinging on the commodity's bottom surfaces. This study also showed that obstructions, such as wood pallets, can significantly impede convective and radiative heat transfer to the underside of the commodity, reducing the lateral flame spread rate. Fire-suppression modeling revealed that both surface water transport and lateral flame spread rates are important when predicting fire-suppression behavior. Therefore, as the rack-storage array height increases, so does the water transport time, which results in the fire becoming more difficult to control. Likewise, as the lateral spread rate increases, e.g., as occurs in the absence of wood pallets, fire-suppression also becomes more difficult.

Experimental and theoretical analysis on lateral flame spread over inclined PMMA surface

The work in this paper aims to clarify the effect of angle on the lateral flame spread over inclined surfaces. PMMA slabs with width ranged from 2.5cm to 12cm were tested at the angles from 0° to 75°. Burning rate, flame spread rate, flame appearance and radiant heat flux were investigated experimentally and theoretically. The results suggest that in the cases of narrow PMMA slabs (less than 8cm), the flame spread rate is in proportion to the square root of angle sine as Vf∝sin1/1θ. For wider slabs, the spread rate is higher than the theoretical result owing to enhanced radiant heat feedback. Pyrolysis length follows a power-law increase with the sample width, and the exponent approximates 0.48. Flame length is independent of the inclination angle, but also a power function of sample width.

Experimental study on flame spread behavior along poly(methyl methacrylate) corner walls at different altitudes

The effects of altitude and intersection angle on the flame spread behavior and pyrolysis front characteristics along corner walls were experimentally studied. The experiments were conducted using mock corners made of poly(methyl methacrylate) slabs with intersection angles varying from 60° to 120° at two altitudes of 29.8 and 3658.0 m. Measurements were taken for the upward and lateral flame spread rates, the flame heights, the flame heat flux to the fuel surface, and the mass loss rates of the tested slabs. An “M”-shaped pyrolysis front was observed for all the intersection angles examined at both altitudes. The upward flame spread rate increases with decreasing intersection angles while no obvious trend was found for lateral spread rate when the intersection angle is varied. The high altitude leads to a spread rate about half of that at the lower altitude both for upward and lateral spread irrespective of the intersection angle. The measured mass loss rates are significantly higher than twice of that over a flat vertical slab.

Correlations between pyrolysis combustion flow calorimetry and conventional flammability tests with halogen‐free flame retardant polyolefin compounds

AbstractSeven halogen‐free flame retardant (FR) compounds were evaluated using pyrolysis combustion flow calorimetry (PCFC) and cone calorimetry. Performance of wires coated with the compounds was evaluated using industry standard flame tests. The results suggest that time to peak heat release rate (PHRR) and total heat released (THR) in cone calorimetry (and THR and temperature at PHRR in PCFC) be given more attention in FR compound evaluation. Results were analyzed using flame spread theory. As predicted, the lateral flame spread velocity was independent of PHRR and heat release capacity. However, no angular dependence of flame spread velocity was observed. Thus, the thermal theory of ignition and flame spread, which assumes that ignition at the flame front occurs at a particular flame and ignition temperature, provides little insight into the performance of the compounds. However, results are consistent with a heat release rate greater than about 66kW/m2 during flame propagation for sustained ignition of insulated wires containing mineral fillers, in agreement with a critical heat release rate criterion for burning. Mineral fillers can reduce heat release rate below the threshold value by lowering the flaming combustion efficiency and fuel content. A rapid screening procedure using PCFC is suggested by logistic regression of the binary (burn/no‐burn) results. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Investigations into the fire hazard of a composite made from aerated concrete and crushed expanded polystyrene waste

The study deals with experimental investigations into the fire hazard of a composite of density 150–350 kg/m3 made of aerated concrete and crushed expanded polystyrene waste. The results of fire tests showed that a single-flame source of low heat output (0.07 kW) did not influence the origination and spread of flame on the surface of test specimens, regardless their density. Upon exposing the specimens to a single burning item of moderate heat output (30.0 kW), during the first 600 s of exposure, neither flaming particles nor droplets originated, nor a lateral flame spread on the long specimen wing was observed. In the case of high heat output (112 kW), the specimens of densities 150 and 250 kg/m3 started to burn, but those of density 150 kg/m3, in addition, lost their integrity.

In-Rack Fire Plumes

A theoretical and experimental study of in-rack fire plumes in a combustible rack storage is presented. The commodity used in the experiments consisted of multiple-wall corrugated paper cartons equally separated in a steel rack, two cartons wide, two cartons deep and four cartons high. Free-bum tests were carried out mostly in reduced scale with verification in full scale. The centreline in-rack gas temperatures and velocities were measured at four elevations inside the rack storage and the heat release rate was measured above the rack storage with a hood system. In-rack temperatures and velocities are plotted using theoretically obtained quasi-steady correlations assuming a point source of buoyancy at floor level and entrainment only in the vertical flues. The theoretical correlations include convective heat release rate, vertical flue width and height above the floor. Temperatures for both reduced scale and full scale correlate reasonably well with the theoretically obtained relationships which have the same functional form as convective plume flow above a linear fire source (line plume). In order to obtain similar correspondance for the velocity in the two scales it was necessary to use Froude number scaling with storage height as length scale. The storage arrangement is found to be important for the initial flame spread and fire growth rate. The reduced scale study shows that the initial fire growth rate decreases with increasing vertical gaps (flues) and that the vertical and lateral flame spread rate increase when the lateral flue height increases. For the initial in-rack fire growth rate, the convective heat release rate was found to be better described by an exponential function rather than a power-law dependence on time to the third power.

Ignitability Analysis of Siding Materials Using Modified Protocol for Lift Apparatus

This paper reports on the ignitability of common siding materials that could be exposed to wildland fires. When exposed to brands or fires, structures will experience piloted ignition, which is requisite for sustained ignition involving burn-through and surface flame spread in various directions. In this study, the Lateral Ignition and Flame Spread Test (LIFT) apparatus (ASTM E1321 and E1317) was used to test various siding materials (plywoods, softwoods, and vinyl), some of wbich were painted, humidified, or sawed. A recently developed protocol provided useful, accurate values of the following thermophysical properties : surface emissivity, surface ignition temperature, tbermal conductivity, and thermal diffusivity. Full consistency was achieved with independent literature values of these properties and can be used directly in the database of fire growth models.