Experimental measurements of flow and flame spread in the development of a fire testing facility

A fire testing facility named the “MSU Fire Tunnel” has been developed. The intent was to devise a testing apparatus that controlled the flow of oxidizing gas in the tunnel to an extent not heretofore accomplished. A novel approach was developed for mounting the flame-spread samples flush with the surface of an “airfoil”. This method avoids previous complications of determining the exact position of the leading edge of the velocity boundary layer. Data were gathered for the flow field using hot-wire anemometry. These data indicated that a zero-pressure gradient Blasius boundary layer flow was established along the airfoil and fuel sample surfaces. Opposed-flow flame-spread tests were conducted and correlations were produced that support the predictive capacity of this apparatus. It was shown that the opposed flow flame-spread data allowed distinctions to be made between correlations of previous researchers. No such comparisons were formerly possible. A finite-chemistry correlation was shown to be consistent with, and similar to, correlations derived in the previous work.     

Experimental measurements and numerical modeling of marginal burning in live chaparral fuel beds

An extensive experimental and numerical study was completed to analyze the marginal burning behavior of live chaparral shrub fuels that grow in the mountains of southern California. Laboratory fire spread experiments were carried out to determine the effects of wind, slope, moisture content, and fuel characteristics on marginal burning in fuel beds of common chaparral species. Four species (Manzanita sp., Ceanothus sp., Quercus sp., and Arctostaphylos sp.), two wind velocities (0 and 2 m/s), two fuel bed depths (20 and 40 cm), and three slope percents (0%, 40%, or 70%) were used. Oven-dry moisture content M of fine fuels (<6.25 mm diameter) ranged from 29% to 105%. Sixty-five of 115 fires successfully propagated the length (2.0 m) of the elevated fuel bed. A previously derived empirical marginal burning criterion was assessed, and a suitable modification was proposed for live chaparral fuels. Based on the experimental data, a stepwise logistic regression model was developed to predict the probability of successful fire spread. This procedure resulted in the selection of wind speed, slope percent, fuel loading, fuel moisture content, and relative humidity as the primary variables. It correctly classified 96% of 115 fires. Finally, a multidimensional numerical model for vegetation fire spread using a porous media sub-model was developed to simulate the laboratory fires. Results are used to analyze the internal heat transfer and combustion processes that determine fire spread success in shrub fuel bed.     

热红联用技术在森林火灾烟气测试中的应用

探索了一套基于热重分析仪-红外光谱分析仪联用（热红联用）技术的森林火灾烟气测试方法.该方法在对森林可燃物燃烧的热失重过程进行热重分析的同时,同步地对热解气体成分进行傅里叶红外光谱（FTIR）分析,从而实现了对燃烧过程诸因素的跟踪分析.     

A novel evacuation passageway formed by a breathing air supply zone combined with upward ventilation

With the development of transportation, the tunnel has become one of the important facilities of railway, highway and subway transportation. However, fire hazards occurring inside the tunnel may incur huge numbers of casualties and property losses. In this paper, a breathing air supply zone combined with an upward ventilation assisted tunnel evacuation system (BTES) is introduced. It can be used to create a safe, smoke-free evacuation passageway out of the tunnel. The BTES is optimized to achieve high-performance. The impacts of heat release rates, fire source locations and fire detection times are also discussed.     

Synergistic effects between a triazine-based charring agent and aluminum phosphinate on the intumescent flame retardance of thermoplastic polyether ester

The triazine-based charring agent (CFA) with perfect charring ability was synthesized and characterized. The synergistic effects between CFA and aluminum phosphinate (AlPi) on flame retardancy, thermal degradation, and flammability properties of thermoplastic polyester-ether elastomer (TPEE) were investigated by limiting oxygen index (LOI), vertical burning test (UL-94), cone calorimeter test (CCT), thermogravimetric analysis (TGA), laser Raman spectroscopy (LSR) and scanning electron microscopy (SEM). The results from UL-94 test showed that, by compounding 14 wt% AlPi and 4 wt% CFA with TPEE, the LOI value reached 28.5% and the UL-94 rating reached V-0 (1.6 mm). TGA results indicated that there is good synergistic charring ability between CFA and AlPi, especially the increased residues at high temperature (T > 700 °C). The CCT test results showed that CFA could change the combustion behavior of TPEE and effectively accelerate the formation of expanded carbon layers. The residues after combustion were measured by LRS and SEM, demonstrating that CFA can promote the formation of dense and stable carbon layers during the combustion, which could inhibit the melt dropping and improve the fire retardancy of TPEE composites. Thus, CFA was a promising synergistic agent in halogen-free flame retardant TPEE.     

Oriented magnetic material in head and antennae of Solenopsis interrupta ant

Ferromagnetic resonance (FMR) has been used to study the magnetic material in the antennae, head, thorax and abdomen of Solenopsis interrupta ants. The measurements were performed at room temperature (RT). The ferrimagnetic broad lines associated to magnetite/maghemite isolated nanoparticles (high field, HF) and to large nanoparticles or aggregates (low field, LF) in insect spectra are present in the S. interrupta body part spectra, although they slightly differ in resonant fields and lineshapes. The spectral absorption areas show (32±3)%, (24±2)%, (21±2)% and (23±1)% of magnetic material average fractions in antennae, head, abdomen and thorax, respectively. Only the resonance field of the head and antennae showed angular dependence. This work shows that head and antenna of S. interrupta ant present organized magnetic material, indicating a biomineralization process.     

Synergism between flame retardant and modified layered silicate on thermal stability and fire behaviour of polyurethane nanocomposite foams

Synergy in flame retardancy of polyurethane foams between phosphorus-based flame retardant (aluminium phosphinate) and layered silicates has been investigated. We used pristine montmorillonite as well as ammonium modified clay (commercially available) and diphosphonium modified clay, which were synthesised by the intercalation of the quaternary diphosphonium salt according to a procedure reported here. The morphology of the foams was characterised through X-ray diffraction (XRD), while thermal properties were characterised by oxygen index test, cone calorimeter and thermogravimetric analysis (TGA). The morphological characterisation showed that pristine and diphosphonium modified clays are almost slightly intercalated, while ammonium modified one is very well dispersed. The results of thermal characterisation showed that in the presence of phosphinate enhancements of oxygen index, fire behaviour, measured by cone calorimeter, and thermal stability have been achieved. Phosphinate is therefore an efficient flame retardant for polyurethane foams and its flame retardancy action takes place in both condensed and gas phases. Pristine and ammonium modified layered silicate bring some enhancements of thermal stability while having no important effect in decreasing peak heat release rate (PHRR) and total heat evolved (THE) when used in conjunction with phosphinate; their main advantage is related to the enhancement of compactness of the char layer formed. Diphosphonium clay is instead effective in further improving the fire behaviour of the foams because of the flame retardancy action of phosphonium: both PHRR and THE were decreased. The analysis of cone calorimeter data showed that clays act through physical effect constituting a barrier at the surface which is effective in preventing or slowing the diffusion of volatiles and oxygen, while phosphinate and phosphonium are more effective owing to their combined action in both condensed and gas phases.     

Fire retardancy of polymer clay nanocomposites: Is there an influence of the nanomorphology?

The obvious aspect of nanodispersion and its role when investigating fire retardancy is not often clearly commented upon in the literature. Polymer clay nanocomposites can exhibit different morphologies and these might have consequences for their fire behaviour. Using solid state NMR to quantify the nanodispersion of organoclay in polyamide-6 (PA-6), we have prepared by melt blending PA-6/clay nanocomposite exhibiting different nanomorphologies. NMR results are consistent with transmission electron microscopy (TEM) images but the advantage of NMR is that it is representative of the whole sample and provides a precise quantification. PA-6 nanocomposites exhibit significant reduction of PHRR but the nanomorphology (exfoliation, intercalation and presence of tactoids) does not play any significant role. In other words, we have clearly shown that if nanodispersion is achieved, polymer/clay nanocomposite should exhibit fire retardant properties.     

Characterisation of the steady state tube furnace (ISO TS 19700) for fire toxicity assessment

The steady state tube furnace (Purser furnace, ISO TS 19700) has been developed specifically to replicate the generation of toxic products from real fires under different fire conditions on a bench-scale. Steady state burning is achieved by driving the sample into a furnace of increasing heat flux at a fixed rate and recording the product yields over a steady state period in the middle of the run. The furnace, sample, and effluent dilution chamber temperature profiles are presented to characterise the conditions in the apparatus. The distribution of smoke in the mixing chamber has been investigated to demonstrate the efficiency of mixing in the effluent dilution chamber. The heat flux applied to the sample at various points through the furnace has been measured, showing that conditions vary from those typical of pre-flaming to fully developed fires. An initial investigation of the repeatability and interlaboratory reproducibility has been undertaken, showing acceptable low levels of uncertainty in the toxic product yields.     

Effect of stress on the fire reaction properties of polymer composite laminates

A small-scale loading frame was used to apply tensile and compressive stresses to glass vinyl ester and glass polyester laminates in a cone calorimeter under a heat flux of 75 kW m⁻². It was found, for the first time, that stress has a small but significant effect on the fire reaction properties. Increasing tensile stress increased heat release rate and smoke production while shortening the time-to-ignition. Compressive stress had the reverse effect. This was attributed to the fact that tensile stress promotes the formation of matrix microcracks, facilitating the evolution of flammable volatiles. This hypothesis is further supported by the observation that stress has the greatest effect on the early heat and smoke release peaks, with a lower effect on the final ‘run-out’ values.Stress rupture (time-to-failure) curves were produced for tension and compression. In tension, the behaviour was fibre dominated, with times-to-failure being roughly 10 times those in compression. Compressive failure involved resin dominated local fibre kinking, initiated near to the rear face of the specimen. The failure time was determined by a significant proportion of the specimen reaching its glass transition temperature.