A numerical model for flame spread along combustible flat solid with charring material with experimental validation of ceiling flame spread and upward flame spread

This paper gives a numerical model for flame spread along combustible flat solid with charring materials. The presented model consists of a one‐dimensional flame spread model coupled with a one‐dimensional pyrolysis model. The existing experimental data (the ceiling flame spread beneath medium density fibreboard) are used for comparison to validate the model. In addition, the model can also be used to predict upward flame spread; only some expressions are changed. A comparison with full‐scale experimental data on the upward flame spread over plywoods from the literature is performed. The results obtained from numerical simulations using the model are consistent with these two kinds of experimental tests. Thus, the presented model is appropriate for modelling not only the ceiling flame spread, but also the upward flame spread. Copyright © 2007 John Wiley & Sons, Ltd.     

An experimental facility for determination of steady flame spread rate of materials employing the Quasi-stationary flame front technique

An experimental facility based on the Quasi-stationary Flame Front Technique for determination of steady flame spread rate of materials at discrete levels of external radiant heat flux was developed. The method employs an external radiant heat source in front of which an element of a specimen of the material is positioned at a location corresponding to the desired level of external radiant heat flux. A specimen movement assembly, which can be operated manually, was designed for moving the specimen towards the stationary external radiant heat source such that the flame front could be maintained quasi-stationary. The experimental technique employed is simple in operation yet is capable of yielding reliable flame fornt displacement–time data. In the paper the design considerations of the experimental facility, details of its components, calibration and typical experimental results obtained are presented.     

A theory for flame extinction based on flame temperature

The extinction and suppression of diffusion flames is examined theoretically. The effects of oxygen reduction and external heat flux are examined compared to data in the literature. An application of extinction in compartment fires is also examined. The theory developed is based on a critical flame temperature, and that theory includes transient effects and the addition of water as well. Copyright © 2004 John Wiley & Sons, Ltd.     

Experimental evaluation of flame and flamelet spread over cellulosic materials using the narrow channel apparatus

Originally conceived as an apparatus to study near‐limit flames and their breakup into flamelets and later modified to function as a microgravity simulation apparatus, the narrow channel apparatus serves also as a facility for examining long time flame spread and material flammability in on‐earth (terrestrial) applications. These applications include flame spread in narrow gaps, persistence of flame in heat‐loss environments, and flame‐to‐flamelet front transition. The narrow channel apparatus tests described here measure behavior of the spreading flame and features of the flame‐to‐flamelet transition. Measured quantities include flow, flame and flamelet velocities in normal and inverted tests, flow deceleration and acceleration rates with associated flame or flamelet response, flame‐to‐flamelet transition times, and influences of fuel thickness. The principal goal of this research was to ascertain the capacity of the narrow channel apparatus to produce data for phenomena observed in both (1) simulated microgravity flame spread and (2) terrestrial flame spread in narrow gaps and channels. Copyright © 2012 John Wiley & Sons, Ltd.     

Effect of modulations of opposed gas flow velocity on flame spread rate over a liquid surface

The effect of modulations of the velocity of the gas flow incident on the flame on the average flame velocity over a shallow liquid is studied. It is shown that the average flame velocity depends on the modulation frequency. If the modulation frequency is higher than the flame oscillation eigenfrequency, then, upon the imposition of the modulation, the flame velocity first increases and then gradually returns to the initial value. At frequencies close to the flame oscillation eigenfrequency, the average flame velocity is constant but is higher than the initial value. __________ Translated from Fizika Goreniya i Vzryva, Vol. 45, No. 1, pp. 11–17, January–February, 2009.     

Survey of small‐scale flame spread test results of modern fabrics

The flammability of apparel worn on a person has one of the highest ratios of fire fatalities per fire, and there are few statutory requirements. A series of evaluations was conducted on the flammability of 50 fabrics (both cellulosic and thermoplastic) using the (now withdrawn) NFPA 701 small‐scale test. The fabrics covered a broad range of areal densities (weights) and many were not intended for apparel. A series of conclusions were reached. In particular, it is apparent that the following primary correlation exists between fabric weight and flammability: the heavier the fabric the better it behaves in a fire. Secondarily, however, the type of fabric also strongly affects this conclusion. This paper presents the results of the testing and offers an analysis. Copyright © 2006 John Wiley & Sons, Ltd.     

Estimation of heat release rate based on analysis of flame spread behavior in mattresses

To investigate the fire danger of mattresses, combustion experiments were conducted with a mattress installed at different heights above the floor to better understand their combustion behavior. The installation height was varied because the height of a mattress varies depending on the bed frame, and the combustion behavior is expected to change with the installation height. Experiments with a mattress installed at 0–515 mm above the floor revealed that the fire growth was faster, and the maximum heat release rate (HRR) increased with installation height. In contrast, in a series of experiments where a mattress was installed above a water pool, the flame spread rates and HRR histories were comparable for all installation heights. This demonstrate that the combustion behavior of the mattress was affected by the combustion of the molten mattress material that dropped to the floor, and this effect was influenced by the mattress installation height. Furthermore, we analyzed the HRR per unit area of mattress construction material using cone calorimeter tests to mimic the combustion taking place on the floor. Combining these results with the relation between the length of the burning part of a mattress at the front of flame spread and the HRR, we proposed a model for predicting the HRR history of mattress for a flame ignition at the center of its longitudinal side. The derived predictive model for the HRR history of mattress combustion emphasize that it is necessary to understand factors such as the intense radiant heat from the pool fire.     

Influence of radiant heat transfer on the reaction-zone temperature of a diffusional flame

An expression is obtained for the error in calculating the reaction-zone temperature of an optically thin diffusional flame due to neglecting the radiant heat transfer. It is shown that this error is greatest in pyrotechnical and hydrocarbon flames with a high soot concentration, and may amount to several hundred degrees.Kazan'. Translated from Fizika Goreniya i Vzryva, Vol. 29, No. 4, pp. 13–16, July–August, 1993.     

A simplified apparatus for the preparation of block copolymers with low polydispersity ratios

A simplified apparatus for the preparation of block copolymers by anionic polymerization is described. Low polydispersity can be obtained without the need for a high degree of manipulative skill.     

A radiant heat flux apparatus for measuring the thermal response of polymeric materials to high temperatures

An efficient and economical experimental apparatus has been designed and built which delivers a known radiant heat flux and simultaneously measures the in-depth temperature profiles in polymeric materials. Test samples are maintained in a controlled environment and are heated radiantly by a silicon carbide heating element capable of producing heat fluxes up to 7.0 cal/cm²-sec. The experimental data produced by this device are extremely accurate and therefore are suitable for use in verification of numerical models. The utility of the apparatus was demonstrated by measuring temperature profiles to approximately 1000°C in a glass-filled phenol-formaldehyde resin.     

Free-convective regime of flame spread over a fuel film on a substrate

Flame spread over a liquid fuel film on a thin metallic substrate under free convection was studied experimentally. Instantaneous flame velocities correlate with the flame length. The average flame velocity increases from 2 to 30–40 cm/sec with the slope angle of the substrate to the horizon varying in the range of 0–90°. For a substrate of specified width, the flame velocity is inversely proportional to the heat capacity of the unit area of the substrate-fuel system and to the differences between the temperature corresponding to the formation of a stoichiometric mixture of the saturated fuel vapor and air and the ambient temperature. __________ Translated from Fizika Goreniya i Vzryva, Vol. 43, No. 5, pp. 21–30, September–October, 2007.     

低温胶粘剂漏率检测系统的研制

低温胶粘剂在航空航天、低温超导以及民用工业等领域有着广泛的应用。低温条件下,由于胶粘剂冷收缩产生应力以及胶粘剂与被粘材料之间的线胀系数存在差异等因素,胶粘区域可能出现微裂纹等破坏现象。为了检测胶粘剂在深低温下的密封性能,研制了一个低温漏率检测系统。低温冷源采用小型制冷机,最低制冷温度10 K。漏率检测采用氦质谱检漏仪,极限检测漏率为5.0×10~(-11) Pa·m~3/s。     

Dynamics of concurrent flame spread over a thin charring solid in microgravity

The dynamics of microgravity concurrent flame spread over thin cellulosic sheets are theoretically investigated. The mathematical model is based on the laminar, reactive Navier–Stokes equations coupled to solid-phase enthalpy and mass conservation equations. Simulations have been made for forced flow velocities in the range 0.25–15 cm/s, by decreasing the oxygen mass fraction of the concurrent flow below the ambient value and by increasing the solid charring rate (fire-retarded cellulose). For air, non-retarded cellulose and flow velocites larger than 5 cm/s, the dynamics of concurrent flame spread are qualitatively similar to those of normal gravity. As the concurrent flow is decreased below 5 cm/s, after short transients, a transition from fast flame spread to slow solid burning and then to flame quenching is predicted. Flame quenching is also observed, for relatively high flow velocities, in vitiated air or for fire-retarded cellulose. Finally, blow-off at the highest velocity considered (15 cm/s) is predicted only for sufficiently low oxygen concentrations. © 1998 John Wiley & Sons, Ltd.     

Application of a one‐dimensional thermal flame spread model on predicting the rate of heat release in the SBI test

A one‐dimensional thermal flame spread model was applied to predict the rate of heat release in the single burning item (SBI) test on the basis of the cone calorimeter data. The input parameters were selected according to the features of the SBI test and using particle board as a model tuning material. The features of the measured and calculated rate of heat release curves were compared for a series of 33 building products. The fire growth rate (FIGRA) indices were calculated to predict the classification in the forthcoming Euroclass system. The model gave correct classification for 90% of the products studied. An essential feature of the model is that only one cone calorimeter test at the exposure level of 50 kW m^?2 is needed. The model, therefore, provides a practical tool for product development and quality control. Copyright © 2001 John Wiley & Sons, Ltd.     

A procedure for assessing the change in flame spread characteristics of paints when subjected to washing

A Collaborative Programme of work was carried out by two laboratories to asscess a procedure for identifying paint systems which possess poor ‘in service’ lives by virtue of being repeatedly washed. The small scale surface spread of flame apparatus as described in BS 476 part 7 was used to measure any change in the surface spread of flame characteristic of eight coating system, applied to two substrates, as a result of washing the coated surfaces. The results indicate that both laboratories ranked the paints in the same order and the reproducibility of the proposed washing procedure was good. The most consistent results were obtained when the coating systems were applied to standard hardboard. It is suggested that flame retardant coating system having poor resistance to washing would be identified if a limit of changes of average spread of flame were set at 75 mm. This investigation was carried out in support of the activities of BSI committee PVC/12, Fire Retardant Paints.     

An appraisal of standard methods for determination of flame spread behaviour of materials

Salient features of the standard apparatuses and the methodology adopted by various countries for determination of flame spread behaviour of materials are analysed and discussed with a view to obtain a perspective of the performance of these apparatuses. This study was undertaken to investigate the possible reasons for anamolies in the results obtained using these apparatuses. A need is established for development of a new technique for direct determination of flame spread rate of materials under steady-state conditions which has the potential of overcoming the inherent limitations of the existing apparatuses.     

A simplified model for heat transfer from a cylinder immersed within a packed bed

A model is presented for heat transfer from an immersed cylinder within a packed bed of particles to gas flowing through the bed parallel to the cylinder's axis.Simplifications in the model permit a closed form solution which agrees closely with the results of a previous numerical solution [1] when similar correlations for the physical mechanisms are employed. The results are shown to be sensitive to the values of the heat transfer coefficient at the cylinder wall and the gas velocity close to the wall.     

A simple calculation model for radiant heat transfer in a paper dryer

A simple and practical method for calculating radiant heat transfer in a directly heated industrial paper dryer is presented. The paper dryer is modelled as an enclosure of three isothermal surfaces. A short overview of the theory of radiant heat transfer between N surfaces is given. The calculations show good agreement with experimental results. A numerical example of the calculation procedure and a FORTRAN-V program are included.