Home About us Contact
|
Home About us Contact | ||
|
|
||
Ignition
Terms modified by Ignition Selected AbstractsFull-scale study on combustion characteristics of an upholstered chair under different boundary conditions,Part 1: Ignition at the seat centerFIRE AND MATERIALS, Issue 6 2009Q. Y. Xie Abstract The objective of this work is to investigate the effects of boundary conditions on the combustion characteristic of combustible items in a room. A series of full-scale experiments were carried out in the ISO 9705 fire test room with an upholstered chair at four typical locations, i.e. at the middle of side wall, at the center of the room with the seat toward the door, at the center of the room with the seat toward inside of the room, at the room corner, respectively. Ignition was achieved through a BS No.7 wooden crib at the geometric center of the seat surface for each test. Besides the heat release rate (HRR), four thermocouple trees were placed around the chair to monitor detailed temperature distributions during the combustion process of an upholstered chair. The results indicated that the boundary conditions had some effects on the combustion behavior of a chair in a room. It was shown that there were clearly two main peak HRRs for the cases of a chair being clung to the side wall or at the corner. However, there was only one main peak HRR when the chair was placed at the center of the room, either outwards or inwards. In addition, the results of the two cases of chairs being at the center indicate that the maximum HRR (about 829,kW) for the chair seat toward the door was relatively larger than the maximum HRR (about 641,kW) for the chair seat toward inside of the room. It was suggested that the special complex structure of a chair was also a considerable factor for the effect of boundary conditions on the combustion behavior of a chair in an enclosure. Furthermore, the measured temperature distributions around the chair also illustrated the effects of boundary condition on the combustion behavior of a chair in a room. It was suggested that although HRR was one of the most important fire parameters, HRR mainly represented the comprehensive fire behavior of a combustible item. In order to develop more suitable room fire dynamic models, more detailed information such as the surrounding temperature distributions measured by the thermocouple trees are useful. Copyright © 2009 John Wiley & Sons, Ltd. [source] Ignition studies of cerium nitrate treated towelsFIRE AND MATERIALS, Issue 3 2006C. L. Beyler Abstract This study evaluated the ignitability of cotton towel material saturated with an oxidizer solution of 0.5 N cerium nitrate in 2 N nitric acid. Four types of ignition testing were performed in this work: self-heating oven tests, hot object ignition tests, radiative smoldering ignition tests, and piloted flaming ignition/burning rate tests. Results indicate that cerium nitrate significantly enhances the ignitability of the towels. Self-heating properties of cerium nitrate treated towels were measured using the standard constant temperature oven method described by Bowes. Based upon these self-heating properties, self-heating is not a hazard for storage scenarios other than bulk storage (depths of several meters) of cerium nitrate treated towels at room temperature. Surface ignition of hot objects was observed for object temperatures as low as 250°C placed upon room temperature cerium nitrate treated towels. Ignition for hot objects buried within a pile of towels occurred for object temperatures as low as 230°C. Radiant heating tests of cerium nitrate treated towels showed initiation of smolder at heat fluxes as low as 3 kW/m2 at surface temperatures as low as 175°C. This compares with ordinary cellulosic materials that require 7,8 kW/m2 heat fluxes and temperatures of 250°C. All four scenarios demonstrate enhanced ignitability and burning rates of cerium nitrate treated towels. Copyright © 2005 John Wiley & Sons, Ltd. [source] Ignition and oxidation of 1-hexene/toluene mixtures in a shock tube and a jet-stirred reactor: Experimental and kinetic modeling studyINTERNATIONAL JOURNAL OF CHEMICAL KINETICS, Issue 9 2007M. Yahyaoui The oxidation of several binary mixtures 1-hexene/toluene has been investigated both in a shock tube and in a jet-stirred reactor (JSR). The self-ignition behavior of binary mixtures was compared to that of neat hydrocarbons studied under the same conditions. Furthermore, molecular species concentration profiles were measured by probe-sampling and GC/MS, FID, TCD analyses for the oxidation of the mixtures in a JSR. Experiments were carried out over the temperature range 750,1860 K. Mixtures were examined under two pressures 0.2 and 1 MPa, with 0.1% initial concentration of fuel. The equivalence ratio was varied from 0.5 to 1.5. The experiments were modeled using a detailed chemical kinetic reaction mechanism. The modeling study showed that interactions between hydrocarbons submechanisms were not limited to small reactive radicals. Other types of interactions involving hydrocarbon fragments derived from the oxidation of the fuel components must be considered. These interactions mainly consist of hydrogen abstraction reactions. For example, benzyl radical that is the major radical produced from the oxidation of toluene at high temperature can abstract hydrogen from 1-hexene and their products such as hexenyl radicals. Similarly, propyl, allyl, and hexenyl radicals that are the major radicals produced during 1-hexene oxidation at high temperature can abstract hydrogen from toluene. Improved modeling was achieved when such interaction reactions were included in the model. Good agreement between experimental and calculated data was obtained using the proposed detailed chemical kinetic scheme. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 518,538, 2007 [source] Combustion Measurements of Fuel-Rich Aluminum and Molybdenum Oxide Nano-Composite MixturesPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 2 2010Tim Bazyn Abstract Fuel rich nano-composite powders of aluminum and molybdenum oxide were tested for ignition and combustion behind the incident and reflected shock waves in a shock tube. The powders consisted of approximately 10,,m particles, each of which contained Al and MoO3 mixed by mechanical alloying on the nano-scale. These powders were aluminum rich with composition ratios of 4,:,1, 8,:,1, and 16,:,1 Al,:,MoO3 by mass. Ignition tests were performed behind incident shocks for temperatures in the range of 900 to 1500,K. From these tests, ignition delay times were obtained, and some information on combustion duration was also derived. Samples were tested in air at 0.2,MPa, and compared against nano-Al, 2.7,,m Al, and 10,,m Al baselines. Ignition results for the baseline Al cases were as expected: 10,,m Al not igniting until 2000,K, 2,,m Al igniting down to ,1400,K, and n-Al igniting as low as 1150,K. The thermite samples showed considerable improvement in ignition characteristics. At the lowest temperature tested (900,K), both the 8,:,1 and 4,:,1 samples ignited within 250,,s. The 16,:,1 sample (94% Al) ignited down to 1050,K , which represents an improvement of roughly 1000,K over baseline Al with only a small energetic penalty. In all cases, the ignition delay increased as the amount of MoO3 in the composite was reduced. The 4,:,1 nano-composite material ignited as fast or faster than the n-Al samples. Ignition delay increased with decreasing temperature, as expected. Emission spectra and temperature data were also taken for all samples using high-speed pyrometry and time-integrated spectroscopy. In these cases, measurements were made behind the reflected shock using end-wall loading, though the conditions (temperature, pressure, and gas composition) were identical to the incident shock tests. Spectroscopy showed strong AlO features in all the samples, and the spectra fit well to an equilibrium temperature. Broadband, low resolution spectra were also fit to continuum, gray body temperatures. In general, the observed temperatures were reasonably close to 3500,K, which is similar to the combustion temperatures of pure aluminum under these conditions. [source] Evidence for the Hypothesis of Ignition of Propellants by Metallic Vapour DepositionPROPELLANTS, EXPLOSIVES, PYROTECHNICS, Issue 6 2002Michael This paper examines the experimental evidence to support the hypothesis of ignition of energetic material by the process of metallic vapour deposition. The hypothesis has been presented previously, and this is the continuation of the work. The hypothesis has been developed at QinetiQ to explain certain measurements of incident radiative flux during electrothermal-chemical (ETC) experimentation, which show no correlation with the ignition event. Indeed, measured levels of radiation have been so low that radiative energy transfer for ETC plasma ignition could be said to be negligible. Measurement of the thickness of a metal layer resulting from dropwise vapour condensation gives good correlation to the flux requirements for ignition. [source] Ca for Er substitution in tetragonal ErPO4 · H2O crystallised from phosphoric acid solutionCRYSTAL RESEARCH AND TECHNOLOGY, Issue 2 2004R. Kijkowska Abstract Erbium phosphate monohydrate with limited Ca for Er substitution, obtained through crystallisation from boiling phosphoric acid solution has been characterised by X-ray diffraction, Ir-spectroscopy and thermal analysis (TGA-DTA) methods. The difference in the electric charge between di-valent calcium and tri-valent erbium in the solid crystallised was compensated by simultaneous substitution of HPO42- for PO43- . Ca incorporation in erbium phosphate made expansion of tetragonal ErPO4 · H2O unit cell. After ignition at 900 °C the tetragonal crystal modification was maintained but the unit cell parameters of all the investigated phosphates, whether Ca-substituted or Ca-free, contracted to the same level. The unique contraction of the unit cell was resulted from recrystallisation of Ca-substituted into Ca-free erbium phosphate, while Ca was transferred into Ca(PO3)2 formed as a separate phase. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Estimation of the phosphorus sorption capacity of acidic soils in IrelandEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2001R. O. Maguire Summary The test for the degree of phosphorus (P) saturation (DPS) of soils is used in northwest Europe to estimate the potential of P loss from soil to water. It expresses the historic sorption of P by soil as a percentage of the soil's P sorption capacity (PSC), which is taken to be , (Alox + Feox), where Alox and Feox are the amounts of aluminium and iron extracted by a single extraction of oxalate. All quantities are measured as mmol kg soil,1, and a value of 0.5 is commonly used for the scaling factor , in this equation. Historic or previously sorbed P is taken to be the quantity of P extracted by oxalate (Pox) so that DPS = Pox/PSC. The relation between PSC and Alox, Feox and Pox was determined for 37 soil samples from Northern Ireland with relatively large clay and organic matter contents. Sorption of P, measured over 252 days, was strongly correlated with the amounts of Alox and Feox extracted, but there was also a negative correlation with Pox. When PSC was calculated as the sum of the measured sorption after 252 days and Pox, the multiple regression of PSC on Alox and Feox gave the equation PSC = 36.6 + 0.61 Alox+,0.31 Feox with a coefficient of determination (R2) of 0.92. The regression intercept of 36.6 was significantly greater than zero. The 95% confidence limits for the regression coefficients of Alox and Feox did not overlap, indicating a significantly larger regression coefficient of P sorption on Alox than on Feox. When loss on ignition was employed as an additional variable in the multiple regression of PSC on Alox and Feox, it was positively correlated with PSC. Although the regression coefficient for loss on ignition was statistically significant (P <,0.001), the impact of this variable was small as its inclusion in the multiple regression increased R2 by only 0.028. Values of P sorption measured over 252 days were on average 2.75 (range 2.0,3.8) times greater than an overnight index of P sorption. Measures of DPS were less well correlated with water-soluble P than either the Olsen or Morgan tests for P in soil. [source] Combustion Characteristics of Mechanically Alloyed Ultrafine-Grained Al-Mg PowdersADVANCED ENGINEERING MATERIALS, Issue 6 2006R.-H. Chen The combustion characteristics of ultrafine Al-Mg alloy powder particles, produced by mechanical alloying methods, and sieved to well-defined size ranges (35 to 100 ,m) were investigated. The ignition and burning times and their size-dependence were determined using time-resolved images of particles burned in the post-flame zone. It was observed that both the ignition and burning times increased with increasing particle size. [source] Inherent flammability parameters,Room corner test applicationFIRE AND MATERIALS, Issue 8 2009J. G. Quintiere Abstract It has been hypothesized that four parameters are solely responsible for a material's performance in a flammability scenario. This excludes effects of material physical integrity, i.e. melting, delamination, etc. They are (1) the critical heat flux below which piloted ignition cannot occur (CHF), (2) the ratio of heat of combustion to heat of gasification (HRP), (3) the thermal response parameter related to the thermal inertia and the ignition temperature (TRP), and (4) the available energy per unit area (AEP). The fire scenario controls the process by its initial heat flux and region of ignition. The hypothesis is applied to 54 tests of the ISO Room Corner Test to assess its validity. It is shown that these four parameters give good correlations in predicting the time to flashover and whether it occurs. In principle, different correlations could be developed for other scenarios of tests and fire configurations. Copyright © 2009 John Wiley & Sons, Ltd. [source] Forensic evaluation of clothing flammabilityFIRE AND MATERIALS, Issue 7 2009M. M. Hirschler Abstract A set of 17 commercial garments were purchased, categorized based on their fabric composition and fire tested. Three fire exposures were used: (a) a simile of the United States regulatory test for apparel fabrics (16CFR1610), (b) a small vertical candle on a small swatch of fabric and (c) a candle applied to a full garment, placed on a mannequin. Comparisons were made between the results of the various tests and of the various fabrics tested. A general correlation was observed whereby increased fabric areal density [weight/unit fabric area] resulted in improved fire performance. Where outliers to this generalization were observed the improved fire performance was due to the superior inherent fire performance of specific fabric types such as silk. Overall, the quantitative behavior with regard to flame spread rate observed after ignition of cellulosic, thermoplastic and blended fabrics was more heavily dependent on fabric areal density than on their chemical composition. Two key conclusions are that very lightweight fabrics constitute a potential danger and that the United States regulatory value, set at 88.3g/m2 (2.6oz/yd2), represents an essentially arbitrary cut-off in this regard. Copyright © 2009 John Wiley & Sons, Ltd. [source] Experimental study on water spray suppression on burning upholstered chair in an enclosure with different application timesFIRE AND MATERIALS, Issue 5 2009Q. Y. Xie Abstract The objective of this work is to investigate the effects of the application time of water spray on the burning upholstered chair in an enclosure. A series of experiments are conducted with the same water flow rate in an ISO 9705 fire test room in which a water spray system is installed. Several identical upholstered chairs are used in the experiments with the application times 20, 25, 30, 40 and 45,s after the ignition of upholstered chair, respectively. The results show that there is nearly an exponential relationship between the peak heat release rates and the relative application times of water spray. It is also shown that there is a polynomial relationship between the relative time for the peak heat release rate and the relative application time of water spray. However, there is an exponential relationship between the whole relative extinguishing time and the relative application time of water spray. A sudden increase is detected before the decreasing of CO generation rates after the water spray is applied on the burning upholstered chair. The average temperatures of the upper hot smoke layer under the ceiling will generally be lower with the earlier application of water spray. Copyright © 2009 John Wiley & Sons, Ltd. [source] Safety evaluation of sewage-sludge-derived fuels by comparison with other fuelsFIRE AND MATERIALS, Issue 4 2009Xin-Rui Li Abstract The utility of sewage sludge as a biomass fuel is taken as a new approach to recycle unwanted wastes as renewable energy and deal with global warming. However, safety caring of this new type of fuel is a premise before it is practically used in boilers. Thermal behaviors of four sludge-derived fuels which are under development were examined by several calorimeters (such as thermogravimetry/differential thermal analysis, C80 and thermal activity monitor) at temperature ramp and isothermal conditions. Heat generation at relatively low temperatures was observed. The corresponding spontaneous ignition was detected in an adiabatic spontaneous ignition tester at 80,C in some sludge species. Moreover, a certain amount of gaseous evolution was accompanied when the sludge fuels were stored at room temperature and at 60,C. Oxidation is mainly responsible for the heat and gas release from the sludge fuels. The hazards of the sewage sludge fuels were also compared with a bituminous coal and a refuse-derived fuel, which have the main feature of spontaneous ignition. Copyright © 2009 John Wiley & Sons, Ltd. [source] Correlations between pyrolysis combustion flow calorimetry and conventional flammability tests with halogen-free flame retardant polyolefin compoundsFIRE AND MATERIALS, Issue 1 2009Jeffrey M. Cogen Abstract Seven 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 & Sons, Ltd. [source] The piloted transition to flaming in smoldering fire retarded and non-fire retarded polyurethane foamFIRE AND MATERIALS, Issue 8 2008Olivier M. Putzeys Abstract The piloted transition from smoldering to flaming, though a significant fire safety concern, has not been previously extensively studied. Experimental results are presented on the piloted transition from smoldering to flaming in non-fire retarded (NFR) polyurethane foam and the fire retarded polyurethane foam Pyrell®. The samples are small blocks, vertically placed in the wall of an upward wind tunnel. The free surface is exposed to an oxidizer flow and a radiant heat flux. The smolder product gases pass upwards through a pilot. The experiments on NFR foam show that the smolder velocity and peak smolder temperature, which increase with the oxygen concentration and heat flux, are strongly correlated to the transition to flaming event, in that there are minimum values of these parameters for transition to occur. The existence of a minimum smolder velocity for ignition supports the concept of a gaseous mixture reaching a lean flammability limit as the criterion for the transition to flaming. To compensate for the solid- and gas-phase effects of the fire retardants on the piloted transition in Pyrell, it was necessary to increase the oxygen concentration and the power supplied to the smolder igniter and the pilot. The piloted transition is observed in oxygen concentrations above 17% in NFR foam and above 23% in Pyrell. The results show that although Pyrell is less flammable than NFR foam, it is still susceptible to smoldering and the piloted transition to flaming in oxygen-enriched environments, which is of interest for special applications such as future space missions. Copyright © 2008 John Wiley & Sons, Ltd. [source] Fire performance of wood (Pinus radiata) treated with fire retardants and a wood preservativeFIRE AND MATERIALS, Issue 6 2008D. C. O. Marney Abstract In this work, we co-formulated an oil-borne copper naphthenate/permethrin wood preservative system with synthetic polymer-based fire-retardant additives prior to the impregnation of Pinus radiata sapwood. We evaluated what effect, if any, the preservative had upon the fire performance properties of the fire retardants and whether the fire retardants impacted on the fungicidal and termiticidal efficacy of the preservative. The fire retardants included halogenated and phosphorus-based systems. A mass loss calorimeter, in conjunction with a thermopile, was used to measure the time to ignition and the peak heat release rate (PHRR) from which the fire performance index (FPI) was determined. The preservative properties were evaluated using termite and soil-block decay bioassays. In summary, we found that the rate of fire growth was reduced when the fire retardants were used in combination with the wood preservative. We also found that the PHRR was a better determinant of fire performance than the FPI. The performance of the wood preservative was enhanced against fungal decay and termite attack when used in combination with the fire retardants. The fire retardants also demonstrated some wood preservative properties of their own. Copyright © 2008 John Wiley & Sons, Ltd. [source] Human survivability in motor vehicle firesFIRE AND MATERIALS, Issue 4 2008K. H. Digges Abstract Automobile fires are consistently among the largest causes of fire death in the United States (about 500 annually) and the U.S. motor vehicle industry and others have spent a significant amount of money in recent years studying this problem. The authors of this review have analyzed the auto industry reports, the scientific literature, and statistical data, and conclude that measures should be taken to improve survivability in automobile fires. The U.S. Federal Motor Vehicle Safety Standard 302 (FMVSS 302) was introduced almost 40 years ago to measure the flammability of interior materials, but improvements in the crashworthiness of automobiles and their fuel tanks and the increased use of combustible materials have changed the motor vehicle fire scenario significantly. In particular, the primary threat has changed from ignition of a small quantity of combustible interior materials by a lit cigarette, in 1960, to ignition of a large quantity of combustible interior and exterior materials by an impact-induced fire, at present. The authors therefore suggest that FMVSS 302 is no longer relevant to automobile fire safety and recommend improved standards based on objective criteria for fire safety performance (fireworthiness) at the system/vehicle level as is routinely done for crashworthiness. Copyright © 2008 John Wiley & Sons, Ltd. [source] Development of fire-retarded materials,Interpretation of cone calorimeter dataFIRE AND MATERIALS, Issue 5 2007B. Schartel Abstract There is little consensus within the fire science community on interpretation of cone calorimeter data, but there is a significant need to screen new flammability modified materials using the cone calorimeter. This article is the result of several discussions aiming to provide guidance in the use and interpretation of cone calorimetry for those directly involved with such measurements. This guidance is essentially empirical, and is not intended to replace the comprehensive scientific studies that already exist. The guidance discusses the fire scenario with respect to applied heat flux, length scale, temperature, ventilation, anaerobic pyrolysis and set-up represented by the cone calorimeter. The fire properties measured in the cone calorimeter are discussed, including heat release rate and its peak, the mass loss and char yield, effective heat of combustion and combustion efficiency, time to ignition and CO and smoke production together with deduced quantities such as FIGRA and MARHE. Special comments are made on the use of the cone calorimeter relating to sample thickness, textiles, foams and intumescent materials, and the distance of the cone heater from the sample surface. Finally, the relationship between cone calorimetry data and other tests is discussed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Cone calorimeter analysis of UL-94 V-rated plastics,FIRE AND MATERIALS, Issue 4 2007Alexander B. Morgan Abstract Cone calorimeter analysis was conducted on 18 thermoplastics with different UL-94 vertical burn test (V) ratings. Ratings varied from V-0 to no rating (NR), and the types of thermoplastics included were polycarbonate (PC), acrylonitrile,butadiene,styrene (ABS), PC/ABS blends, high-impact polystyrene (HIPS), polypropylene (PP), and poly(vinyl chloride) (PVC). Our analysis of the cone calorimeter data found that there were correlations between UL-94 V rating and some cone calorimeter measurements (peak heat release rate (HRR) average and HRR at 60 s) and no relationship for other measurements (time to ignition and total heat release). However, no precise correlation was found due to significant differences in flame retardant mechanism and polymer fuel energy values. In this paper, we seek to explain further why a broad quantitative relationship between UL-94 V and cone calorimeter remains elusive, and also to show how the cone calorimeter can be used to understand why a material passes or fails a particular UL-94 V rating. Copyright © 2006 John Wiley & Sons, Ltd. [source] Prudent practices for the design and installation of heat-producing devices near wood materialsFIRE AND MATERIALS, Issue 2 2007Vytenis Babrauskas Abstract The conditions required to cause ignition of solid wood materials under short-term heating are examined, and it is found that the appropriate ignition temperature applicable under these conditions is 250°C. It is then shown that ignition requirements are different if long-term heating is involved and that ignition can occur at exposure temperatures much lower than the ignition temperature pertinent to short-term heating. It is shown that hot surfaces of 77 °C or higher, if located for a long duration next to a wood member are liable to lead to its ignition in a self-heating mode. Recommendation is made that prudent practices for design or installation must also involve a suitable safety factor. Copyright © 2006 John Wiley & Sons, Ltd. [source] A further study of factors affecting pneumatic-impact ignition of polymersFIRE AND MATERIALS, Issue 6 2006Fu-Yu Hshieh Abstract One likely cause of polymer ignition in high-pressure oxygen systems is the adiabatic-compression heating of polymers caused by pneumatic impact. The previous study showed that pneumatic-impact ignition of polymers could be initiated by a local heterogeneous reaction between the hot oxygen and the oxidation sites of the polymer. This study further investigates other factors that cause pneumatic-impact ignition of polymers in high-pressure oxygen. Because the oxygen concentration has a significant effect on pneumatic-impact ignition, threshold oxygen concentrations for pneumatic-impact ignition of six selected polymers were determined at 20.7 MPa (3000 psia), an expected service pressure in high-pressure oxygen systems. The six polymers investigated were: Teflon PTFE (polytetrafluoroethylene), Neoflon CTFE (polychlorotrifluoroethylene), PEEK (polyetheretherketone), Zytel 42 (nylon 6/6), Buna N (acrylonitrile butadiene rubber), and Viton A (copolymer of vinylidene fluoride and hexafluoropropylene). The results show that PEEK exhibited the highest threshold oxygen concentration (65%) and Zytel 42 exhibited the lowest threshold oxygen concentration (<21%). Copyright © 2006 John Wiley & Sons, Ltd. [source] Ignition studies of cerium nitrate treated towelsFIRE AND MATERIALS, Issue 3 2006C. L. Beyler Abstract This study evaluated the ignitability of cotton towel material saturated with an oxidizer solution of 0.5 N cerium nitrate in 2 N nitric acid. Four types of ignition testing were performed in this work: self-heating oven tests, hot object ignition tests, radiative smoldering ignition tests, and piloted flaming ignition/burning rate tests. Results indicate that cerium nitrate significantly enhances the ignitability of the towels. Self-heating properties of cerium nitrate treated towels were measured using the standard constant temperature oven method described by Bowes. Based upon these self-heating properties, self-heating is not a hazard for storage scenarios other than bulk storage (depths of several meters) of cerium nitrate treated towels at room temperature. Surface ignition of hot objects was observed for object temperatures as low as 250°C placed upon room temperature cerium nitrate treated towels. Ignition for hot objects buried within a pile of towels occurred for object temperatures as low as 230°C. Radiant heating tests of cerium nitrate treated towels showed initiation of smolder at heat fluxes as low as 3 kW/m2 at surface temperatures as low as 175°C. This compares with ordinary cellulosic materials that require 7,8 kW/m2 heat fluxes and temperatures of 250°C. All four scenarios demonstrate enhanced ignitability and burning rates of cerium nitrate treated towels. Copyright © 2005 John Wiley & Sons, Ltd. [source] Mechanisms and modes for ignition of low-voltage, PVC-insulated electrotechnical productsFIRE AND MATERIALS, Issue 2 2006Vytenis BabrauskasArticle first published online: 1 AUG 200 Abstract PVC is the most common insulation material used for wiring in low-voltage (LV) service. ,Low-voltage', in the context of this paper, is taken to be 120,240 VAC. The electrotechnical products considered include insulated wires, cables and cords, and also appurtenant termination devices, e.g. male plugs or female taps. Well-known factors leading to the ignition of PVC-insulated wiring and related products include: (a) manufacturing defects; (b) grossly excessive current; (c) over-insulation, sometimes augmented by overcurrent; (d) localized heating due to strand breakage; (e) localized heating due to mechanical strand severing by staples or nails; and (f) localized heating due to failed terminations. Other failure modes are known but have received only limited study. These include (i) excessive force and creep; (ii) chemical interaction effects; and (iii) breakdown under voltage surge conditions. Additional research is needed in these areas. The proximate cause of ignition involved with many of the above mechanisms is arc tracking (arcing across a carbonized path). In turn, it is shown that PVC is especially susceptible to becoming charred, it requiring only approximately 160°C for the material to become semiconducting during short-term exposure (around 10 h), while longer-term exposure (around 1 month) may cause failures at temperatures as low as 110°C. Some limited data exist which suggest that standard UL and IEC temperature classifications are unduly optimistic, as applied to PVC. Fire can originate if wiring or equipment cannot withstand a powerline surge. Mains-connected electrical appliances need to be designed to resist 6000 V surge voltages, even though this is not mandated in most of the current UL and IEC standards. Data are presented showing that the IEC 60112 wet-tracking test gives especially misleading results for PVC and should be improved or abrogated. Copyright © 2005 John Wiley & Sons, Ltd. [source] Screening of plenum cables using a small-scale fire test protocolFIRE AND MATERIALS, Issue 1 2006Mohammed M. Khan Abstract The extent of flame propagation of electric cables in the FM Global intermediate-scale parallel panel test (PPT) using a 60 kW sand burner has been correlated with a dimensional fire propagation index (FPI,)[(m/s1/2)/(kW/m)2/3] derived from ignition and vertical propagation tests in small-scale ASTM E-2058 Fire Propagation Apparatus (FPA). Two distinct types of fire behavior were observed in the PPT. The cables that did not propagate beyond the vicinity of the ignition burner flames have a FPI equal to or less than 7 [(m/s1/2)/(kW/m)2/3], whereas cables that propagated to the top of the 4.9 m parallel panels had a FPI equal to or greater than 14 [(m/s1/2)/(kW/m)2/3]. All the plenum rated (Ul-910 or NFPA 262 tested) cables tested in this study did not exhibit flame propagation in the PPT, had FPI values of 7 [(m/s1/2)/(kW/m)2/3] or less and generated considerably lower smoke than those cables that propagated in the PPT. Based on this study, it is suggested that FPI measured in ASTM E-2058 FPA may be used for screening cables for UL-910 or NFPA262 tests, thus requiring substantially less cable to be supplied for testing. Copyright © 2005 John Wiley & Sons, Ltd. [source] On the ignition of fuel beds by firebrands,,FIRE AND MATERIALS, Issue 1 2006Samuel L. Manzello Abstract An experimental apparatus has been built to investigate the ignition of fuel beds as a result of impact with burning firebrands. The apparatus allowed the ignition and deposition of both single and multiple firebrands onto the target fuel bed. The moisture content of the fuel beds used was varied, and the fuels considered were pine needle beds, shredded paper beds and crevices constructed of cedar shingles. Firebrands were simulated by machining wood (Pinus ponderosa) into small disks of uniform geometry and the size of the disks was varied. Firebrand simulation was necessary because it is difficult to capture and characterize firebrands from an actual burning object. The firebrand ignition apparatus was installed into the fire emulator/detector evaluator to investigate the influence of an air flow on the ignition propensity of fuel beds. The results of this study are presented and compared with relevant studies in the literature. Published in 2005 by John Wiley & Sons, Ltd. [source] A flammability performance comparison between synthetic and natural clays in polystyrene nanocompositesFIRE AND MATERIALS, Issue 4 2005Alexander B. Morgan Abstract Polymer-clay nanocomposites are a newer class of flame retardant materials of interest due to their balance of mechanical, thermal and flammability properties. Much more work has been done with natural clays than with synthetic clays for nanocomposite flammability applications. There are advantages and disadvantages to both natural and synthetic clay use in a nanocomposite, and some of these, both fundamental and practical, will be discussed in this paper. To compare natural and synthetic clays in regards to polymer flammability, two clays were used. The natural clay was a US mined and refined montmorillonite, while the synthetic clay was a fluorinated synthetic mica. These two clays were used as inorganic clays for control experiments in polystyrene, and then converted into an organoclay by ion exchange with an alkyl ammonium salt. The organoclays were used to synthesize polystyrene nanocomposites by melt compounding. Each of the formulations was analysed by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM). Flammability performance was measured by cone calorimeter. The data from the experiments show that the synthetic clay does slightly better at reducing the heat release rate (HRR) than the natural clay. However, all the samples, including the inorganic clay polystyrene microcomposites, showed a decreased time to ignition, with the actual nanocomposites showing the most marked decrease. The reason for this is postulated to be related to the thermal instability of the organoclay (via the quaternary alkyl ammonium). An additional experiment using a more thermally stable organoclay showed a time to ignition identical to that of the base polymer. Finally, it was shown that while polymer-clay nanocomposites (either synthetic or natural clay based) greatly reduce the HRR of a material, making it more fire safe, they do not provide ignition resistance by themselves, at least, at practical loadings. Specifically, the cone calorimeter HRR curve data appear to support that these nanocomposites continue to burn once ignited, rather than self-extinguish. Copyright © 2004 John Wiley & Sons, Ltd. [source] Surface temperature measurements on burning materials using an infrared pyrometer: accounting for emissivity and reflection of external radiationFIRE AND MATERIALS, Issue 1 2004Joe Urbas Abstract This paper demonstrates the successful use of an infrared pyrometer, operating in the 8,10 µm wavelength band, to measure the surface temperature of combustible specimens in a heat release calorimeter. The temperature histories of ten different materials were measured in the ICAL (intermediate scale calorimeter). The set of materials comprised four wood products, gypsum board, polyisocyanurate foam, PVC floor tile, PMMA and two non-combustible boards. A small-diameter bare thermocouple was installed on each specimen in order to determine an accurate temperature for comparison. The spectral emissivity and the spectral flux reflected from the surface were measured simultaneously and used to correct the apparent temperature measured by the pyrometer. The spectral emissivity and reflected spectral flux were both constant prior to ignition for all the combustible materials. During the burning phase all the combustible materials had a spectral emissivity very close to unity. The agreement between the temperatures measured with the pyrometer and thermocouple was not affected by the flame. The wood products, the polyisocyanurate foam and the calcium silicate board required no correction for reflected spectral flux over the whole temperature range. Copyright © 2004 John Wiley & Sons, Ltd. [source] Time to ignition, heat release rate and fire endurance time of wood in cone calorimeter testFIRE AND MATERIALS, Issue 4 2001Toshiro HaradaArticle first published online: 15 MAR 200 The combustibility of wood specimens was tested by cone calorimeter. A total of nine wood species (four softwood and five hardwood) were used. The thicknesses of the specimens were 10, 20 and 40 mm. The heated surfaces were radial, tangential, and cross-sections of wood. The irradiance levels were 20, 25, 30, 40 and 50 kWm,2. The effects of wood species, density, specimen thickness, heated surface (radial, tangential or cross-section), and irradiance level on time to ignition, mass loss rate, heat release rate and fire endurance time were studied. Simple formulae were proposed to forecast those indices and their validity was examined. Copyright © 2002 John Wiley & Sons, Ltd. [source] Hydrogen Production via Autothermal Reforming of Diesel FuelFUEL CELLS, Issue 3 2004J. Pasel Abstract Hydrogen, for the operation of a polymer electrolyte fuel cell, can be produced by means of autothermal reforming of liquid hydrocarbons. Experiments, especially with ATR 4, which produces a molar hydrogen stream equivalent to an electrical power in the fuel cell of 3,kW, showed that the process should be preferably run in the temperature range between 700,° and 850,°. This ensures complete hydrocarbon conversion and avoids the formation of considerable amounts of methane and organic compounds in the product water. Experiments with commercial diesel showed promising results but insufficient long-term stability. Experiments concerning the ignition of the catalytic reaction inside the reformer proved that within 60,s after the addition of water and hydrocarbons the reformer reached 95% of its maximum molar hydrogen flow. Measurements, with respect to reformer start-up, showed that it takes approximately 7,min. to heat up the monolith to a temperature of 340,° using an external heating device. Modelling is performed, aimed at the modification of the mixing chamber of ATR Type 5, which will help to amend the homogeneous blending of diesel fuel with air and water in the mixing chamber. [source] Early pyrotechnology in the Near East: Experimental lime-plaster production at the Pre-Pottery Neolithic B site of Kfar HaHoresh, IsraelGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 6 2008Y. Goren A characteristic hallmark of the Pre-Pottery Neolithic B (PPNB) in the southern Levant was the extensive use of lime plaster for architectural and other purposes. Yet no obvious kilns have been identified in archaeological contexts. Here we present details of an experimental pit-kiln modeling lime-plaster production based on observed burnt stone accumulations in pits at the PPNB site of Kfar HaHoresh in the lower Galilee. The experimental kiln was loaded in layers with ,500 kg of limestone (pebbles and stones) and ,1000 kg of fuel (branches and dung). Fired for 24 hours, and reaching a maximum 870°C, the kiln yielded almost 250 kg of quicklime (calcium oxide, CaO). Micromorphological samples, general observations, and scaled plan view drawings made immediately following and nine years after ignition demonstrate that the original shape of the kiln and residual quicklime within and around it rapidly dissipated through bioturbation, trampling by animals, erosion, rain, and exposure to the elements. This could account for the seeming absence of kilns within sites, although they were probably located close to where lime-plaster was applied, given the unstable nature and toxic effects of handling quicklime. Calculations of the manpower and fuel involved indicate that PPNB lime-plaster production may have been less labor intensive and less detrimental to the environment than previously portrayed. © 2008 Wiley Periodicals, Inc. [source] Combustion behavior of a falling sodium droplet: Burning rate-constant and drag coefficientHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 7 2005Atsushi Makino Abstract The combustion behavior of a single sodium droplet has been studied experimentally, by use of a falling droplet. It was found that D2 -law can hold for the sodium droplet combustion after the ignition, which can be observed to occur through an increase in the droplet temperature under a condition without a gaseous flame, suggesting that a surface reaction plays an important role in the ignition of sodium. It was also found that the burning rate-constant without forced convection has nearly the same value as those for conventional hydrocarbon droplets, although it is considered that the sodium combustion proceeds in an oxidizer-rich environment even in the air. This can be judged by comparing a temporal variation of the flame/droplet diameter ratio for the sodium droplet with that for the hydrocarbon droplet. A micro-explosion of the burning droplet is also observed when oxygen concentration in the ambience exceeds 0.33 in mass fraction. As for the falling velocity and/or distance of the burning droplet, it turned out that the use of the drag coefficient for solid sphere under isothermal condition is inappropriate in obtaining accurate values. It was also found in another experiment that when Re > 500, the drag coefficient of the falling droplet undergoing combustion is as high as 2 depending on combustion situation and/or droplet temperature, while that of the solid sphere under an isothermal condition is 0.44. © 2005 Wiley Periodicals, Inc. Heat Trans Asian Res, 34(7): 481,495, 2005; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20084 [source] | ||||||||||||||||||||||||||||