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 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.     

聚合物材料燃烧性和阻燃性的实验方法

综述了近年来国内外聚合物材料燃烧和阻燃性能实验方法的最新进展。介绍了极限氧指数法、水平和垂直燃烧法、烟密度法、热重分析法、锥形量热仪法、辐射气化法、高温处理法等,分析了各种实验方法的特点,展望了聚合物材料燃烧和阻燃性能实验方法的发展趋势。     

An experimental technique employing a high-temperature gas-tight alumina seal for the assessment of the electrical properties of solid electrolytes

A technique is déscribed that permits the high-temperature gas-tight extension of short solid electrolyte tubes, discs or rods. It is demonstrated that this technique can be successfully used in the assessment, by coulometric titration, of mixed ionic and electronic conduction in the short solid electrolyte tubes that are commonly used in practical oxygen sensors.     

A simplified theory for generalizing results from a radiant panel rate of flame spread apparatus

Experimental results on the rate of lateral flame spread and time for piloted ignition under an externally imposed radiant flux were analyzed with a simple theroretical model. The data were developed from a radiant panel apparatus that considers a wall mounted sample with a flux distribution \documentclass{article}\pagestyle{empty}\begin{document}$ (\dot q_{\rm e} ^{\prime \prime } ) $\end{document} of 5 W cm^?2 at the ignited end to 0.2 W cm^?2 at the other end. It is shown that after an appropriate preheating time (flux exposure time before sample is ignited) the rate of flame spread (V_f) results can be correlated by \documentclass{article}\pagestyle{empty}\begin{document}$ V_{\rm f} - {\textstyle{1 \over 2}} = C\left( {\dot q''_{{\rm o,ig}} - \dot q_{\rm e} ^{\prime \prime } } \right) $\end{document} where C is a material ‘constant’ and \documentclass{article}\pagestyle{empty}\begin{document}$ \dot q''{\rm }_{{\rm o,ig}} $\end{document} is minimum flux for piloted ignition—also a material (and configuration) constant. An extension of this model demonstrates that V_f can also be expressed in terms of an ‘ignition temperature’ and the surface temperature of the material. Both correlations are derivable from a single flame spread experiment. Results are presented for a number of typical wood and plastic materials.     

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.     

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.     

Rapid x-ray diffraction technique for determination of crystallinity of cellulosic materials

Predominant orientation or texture of cellulosic materials leads to the overestimation of the contribution from crystalline fractions when x-ray diffraction techniques are used for determination of crystallinity of these materials. Therefore it was attempted to determine the fraction of noncrystalline cellulose on the diffractomer by using a recalculating instrument to measure the scattering power at an angle 2θ = 32° from cellulose tablets, and by comparing these result with a reference sample. The method is convenient for process control procedures.     

Continuous prediction technique for fast determination of cyclic steady state in simulated moving bed process

In the simulation of cyclic processes, such as simulated moving bed (SMB), the system should be equilibrated to reach a cyclic steady state (CSS) before evaluating the process performance. However, the conventional method of successive substitution is quite time-consuming. In this work, a continuous predicting method (CPM) is developed for fast determination of CSS in SMB. In CPM, the direct prediction of state variable at CSS and solving model equation are conducted alternately until CSS is reached. In order to give a guideline for the selection of the acceleration factor, CPM is applied on SMB process for enantioseparation of 1,1′-bi-2-naphtol racemate and with the optimized acceleration factor, 59% of computation time saved compared with successive substitution. In addition, this method is further successfully used in a sugar separation process. Given its efficiency and simplicity, this method could provide a useful tool for SMB simulations.     

混料实验方法在阻燃PE配方中的应用

利用混料实验设计方法对膨胀型阻燃剂（IFR）－聚磷酸铵、季戊四醇和成炭促进剂体系的配方进行了优化设计,通过建立膨胀阻燃聚乙烯（IFR－PE）材料的氧指数（OI）回归方程,得到了IFR组分的优化配方。结果表明,按优化配方制备的IFR－PE材料的OI可达29．3,优于用单因素轮换实验方法所得材料的阻燃性能。     

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.     

An experimental study on the flame stability of LFG and LFG-mixed fuels

Landfill gas (LFG), having sufficient chemical energy to sustain the operations of commercial combustors, has become a subject of special interest recently. In this study, the flame stabilities of LFG, LFG-mixed fuel I and II were investigated for their applications to domestic appliances using premixed combustion and swirl combustors using non-premixed combustion. LFG-mixed fuel I and II are made by mixing LFG with liquefied propane gas (LPG). LFG-mixed fuel I has higher-heating value (HHV) equivalent to that of liquefied natural gas (LNG), and LFG-mixed fuel II has Wobbe index (WI) equivalent to that of LNG. Thermodynamic calculations and experimental results on burning velocity and flame stability confirmed that LFG-mixed fuel I and II may be used as interchangeable gas of LNG without any modifications of domestic combustion appliance. For the non-premixed type combustor, the flame stability of LFG-mixed fuels is lower than that of LNG in the weak swirl condition. But in the strong swirl condition, the LFG-mixed fuels show similar stable flame zone to that of LNG and thus, can be used as an interchangeable gas of LNG. In addition, LFG itself can also be used as an alternative fuel of LNG, except that the turndown ratio goes down by half.     

Self-ignition ahead of the flame front in piston spark-ignition engines

The hypothesis that engine knock is a result of competition of two types of chemical reaction—frontal frontal and volumetric—is put forward. A mathematical model for mixture self-ignition ahead of the flame front in an internal-combustion spark-ignition engine is constructed. The operation process was calculated numerically with variation of the ignition angle, the degree of compression, and the rotation frequency of the crankshaft. A critical condition for the occurrence of engine knock is obtained by approximate analytical solution of the problem. Comparison of theoretical results for ten engine parameters and operation with experimental data of different authors confirms the validity of the proposed hypothesis on the occurrence of engine knock. Translated from Fizika Goreniya i Vzryva, Vol. 33, No. 6, pp. 3–13, November–December, 1997.