Experimental study on ignition and combustion characteristics of typical oils

The impact of radiant heat flux on ignition and combustion behavior of typical oils (diesel, lubricating oil, and aviation kerosene) was conducted in a cone calorimeter. A circular steel pan with a diameter of 10 cm was used to contain diesel, lubricating oil, and aviation kerosene without water sublayer. Using the standard oxygen consumption method, we obtained ignition time, heat release rate, mass loss rate, extinction coefficient, CO, and CO₂ yield, and average specific extinction area was calculated from the extinction coefficient. Janssens' method was adopted in this study to deal with ignition time and radiant heat flux under a 0.55 power rule. Results show that the fitting through Janssens' method is good for ignition time of diesel, lubricating oil, and aviation kerosene and radiant heat flux. Moreover, heat release rate, mass loss rate, and CO/CO₂ ratio appear to positively correlate with radiant heat flux, whereas average specific extinction area varies in a certain range. Copyright © 2013 John Wiley & Sons, Ltd.     

Flammability hazards of typical fuels used in wind turbine nacelle

This study aims to develop a complete methodology for assessing flammability hazards of typical fuels (ie, transformer oil, hydraulic oil, gear oil, and lubricating grease) used in a wind turbine nacelle by combining different experimental techniques such as thermogravimetric analysis and cone calorimetry. Pyrolysis properties (onset temperature, temperature of maximum mass loss rate, and mass residue) and reaction‐to‐fire properties (ignition time, heat release rate, mass loss rate, and smoke release rate) were determined and used for a preliminary assessment of thermal stability and flammability hazards. Additional indices, for ignition and thermal behavior (effective heat of combustion, average smoke yield, and smoke point height, heat release capacity, fire hazard parameter, and smoke parameter, were calculated to provide a more advanced assessment of the hazards in a wind turbine. Results show that pyrolysis of transformer oil, lubricating grease, hydraulic oil, and gear oil occur in the range of 150°C to 550°C. Lubricating grease and transformer oil show the higher and lower thermal stabilities with maximum pyrolysis rate temperatures of 471°C and 282°C, respectively. The measured relation between ignition time and radiant heat flux agrees well with Janssens method (a power of 0.55). The aforementioned indices appear to provide a reasonable prediction of performance under real fire conditions according to a full‐scale fire test documented by Declercq and Van Schevensteen. The results of the study indicate that transformer oil is the easiest to ignite while lubricating grease is the most difficult to ignite but also has the highest smoke production rate; that transformer oil has the highest heat release rate while gear oil has the lowest; and that the fire hazard parameter is the highest for transformer oil and the smoke parameter is the highest for lubricating grease. The potential of this type of work to design safer wind turbines under performance‐based approaches is clearly clarified.     

Investigation of a combustible material in the fire of Hengyang merchant's building

Agaric, a kind of important combustible material in the fire of Hengyang merchant's building, was investigated using different experiment equipments. Its degradation and pyrolysis behavior were studied by means of thermogravimetric and kinetic analysis and pyrolysis gas chromatography–mass spectroscopy analysis. External radiation heat and internal heat were used to ignite the agaric. For external radiation ignition, a series of bench‐scale fire tests were done in cone calorimeter in accordance with ISO 5660. As for the internal heat ignition, a fire test was carried out in a full‐scale room in accordance with ISO 9705. Multi‐parameter measurement, including heat release rate (HRR), mass loss rate (MLR), temperature field and species concentration, has been accomplished. Meanwhile, the process of a full‐scale fire test was numerically simulated. The computational results were consistent with experiment data, which will lay down a good foundation for further study in fire reconstruction of the whole fire. Copyright © 2008 John Wiley & Sons, Ltd.     

Flammability characteristics at applied heat flux levels up to 200 kW/m2

This paper documents the first of the two interrelated studies that were conducted to more fundamentally understand the scalability of flame heat flux, the motivation being that it has been reported that flame heat flux back to the burning surface in bench‐scale experiments is not the same as for large‐scale fires. The key aspect was the use of real scale applied heat flux up to 200kW/m² which is well beyond that typically considered in contemporary testing. The main conclusions are that decomposition kinetics needs to be included in the study of ignition and the energy balance for steady burning is too simplistic to represent the physics occurring. An unexpected non‐linear trend is observed in the typical plotting methods currently used in fire protection engineering for ignition and mass loss flux data for several materials tested and this non‐linearity is a true material response. Using measured temperature profiles in the condensed phase shows that viewing ignition as an inert material process is inaccurate at predicting the surface temperature at higher heat fluxes. The steady burning temperature profiles appear to be invariant with applied heat flux. This possible inaccuracy was investigated by obtaining the heat of gasification via the ‘typical technique’ using the mass loss flux data and comparing it to the commonly considered ‘fundamental’ value obtained from differential scanning calorimetry measurements. This comparison suggests that the ‘typical technique’ energy balance is too simplified to represent the physics occurring for any range of applied heat flux. Observed bubbling and melting phenomena provide a possible direction of study. Copyright © 2007 John Wiley & Sons, Ltd.     

Combustion behaviour of polyurethane flexible foams under Cone Calorimetry test conditions

The first part of this study focuses on the effect of cone calorimeter test variables on polyurethane flexible foam properties such as ignitability, heat release rate, effective heat of combustion and mass loss. Three of the main commercial foam types were used, i.e. conventional slabstock foams, high-resilience slabstock foams and all-MDI (methylene diphenyldiisocyanate) moulded foams. A decrease in heat flux (down to 40%) with increasing distance from the conical heater was measured. As a consequence, results were found to depend to a large extent on the thickness and the melting behaviour of the foam samples. To achieve a sufficiently constant and uniform heat flux exposure, sample thickness had to be limited to 25 mm. In addition, repeatability was found to be good under various conditions, with percentage standard deviations for effective heat of combustion, peak rate of heat release and mass loss below 10%. Levels of radiant flux above 25 kW m^?2 were found to be very severe to test flexible polyurethane foams. Under such conditions, foams that show large differences in combustion performance in small-scale flammability tests performed almost identically in the cone calorimeter. In the second part of this study the effects of foam variables, such as foam type, density and melamine content, are defined. These effects were clearly pronounced at radiant flux levels of 15–25 kWm^?2. Density was found to be the key variable in controlling ignition resistance. In addition, high-resilience slabstock foams and all-MDI moulded foams performed better than conventional slabstock foams of the same density. Melamine addition resulted in a delay of ignition for all three foam types and an incomplete combustion, decreased heat release and effective heat of combustion in HR-slabstock and all MDI moulded foams. However, melamine is not effective as a heat sink in conventional slabstock foams. The different performance of the foam types under study can be explained by a different melting behaviour.     

A theoretical basis for flammability properties

Theoretical formulations are presented for the fire growth processes under external radiant heating. They included ignition, burning and energy release rate, and flame spread. The behaviour of these processes with external heating is described along with the critical conditions that limit them. These include the critical heat fluxes for ignition, flame spread and burning rate. It is shown how these processes and their critical conditions depend on a limited number of properties measurable by a number of standard test methods. The properties include heat of combustion, the heat of gasification, ignition temperature and the thermal properties of the material. Alternatively, the properties could be related to parameters easily found from data; namely: (1) the critical heat flux (CHF) for ignition; (2) the slope of the energy release rate with externally imposed flux, defined as heat release parameter (HRP); and (3) the ignition parameter, defined as thermal response parameter (TRP). It is further shown that the flame heat flux differences between small laminar flame ignition sources and larger turbulent flames can affect flame spread due to heat flux and ignition length factors. Finally, it is found that the critical energy release rates theoretically needed for ignition, sustained burning, and turbulent upward flame spread are roughly 13, 52, and 100 kW/m², respectively, and independent of material properties. Copyright © 2005 John Wiley & Sons, Ltd.     

Combustion properties of Brazilian natural wood species

This paper investigates the combustion characteristics of 12 wood species natural to Brazil. A mass loss cone calorimeter was used to obtain the properties associated with (i) heat release rate (HRR), peak HRR, and total heat released; (ii) total mass loss and mass loss rate; (iii) average effective heat of combustion; and (iv) time to ignition, time of pyrolysis and temperature of ignition. The samples used in this work were as follows: (i) prepared in accordance to ISO 5660‐1:2002; (ii) oven dried; (iii) irradiated with a constant heat flux of 50 kW/m²; and (iv) exhibit wood fiber orientation in a plane orthogonal to the flux incidence. Finally, the paper explores the possibility of linking the obtained combustion properties with the density and classes of selected wood species. Copyright © 2014 John Wiley & Sons, Ltd.     

Burning rate of solid wood measured in a heat release rate calorimeter

Burning rate is a key factor in modeling fire growth and fire endurance of wood structures. This study investigated the burning rate of selected wood materials as determined by heat release, mass, loss and charring rates. Thick samples of redwood, southern pine, red oak and basswood were tested in a heat release rate calorimeter. Results on ignitability and average heat release, mass loss and charring rates are reported for a heat flux range between 15 and 55 kw m^?2. In this range, burning rate increased linearly with heat flux. Burning rate was very species dependent. Heat release rate was related to mass loss by effective heat of combustion, which also increased with heat flux. Charring rate was related to mass loss rate and original wood density. Important char property data such as yield, density and contraction are reported. A simplified calculation method is proposed for calculating mass loss rate and charring rate based on heat release rate.     

Flame‐retardant mechanism of silica: Effects of resin molecular weight

The effects of resin molecular weight on the flame‐retardant mechanism of silica were studied with two different molecular weights of poly(methyl methacrylate) (PMMA), 122,000 and 996,000 g/mol, and two silicas, fused silica with a small surface area and silica gel with a large surface area. A total of six different samples were studied, with a mass fraction of 10% silica. The mass loss rate of the six samples in nitrogen and the heat release rate from burning in air were measured at an external radiant flux of 40 kW/m². The addition of silica gel to the low‐molecular‐weight PMMA significantly reduced the mass loss rate and heat release rate; addition to the high‐molecular‐weight PMMA provided the largest reductions of these quantities in this study. For fused silica, some reduction in mass loss rate and heat release rate was observed when it was added to the high‐molecular‐weight PMMA; addition to the low‐molecular‐weight PMMA did not reduce either loss rate. Chemical analysis of the collected residues and observation of the sample surface during gasification reveal the accumulation of silica near the surface; the larger its coverage over the sample surface was, less the mass loss rate and heat release rate were. Both the level of accumulation and its surface coverage depended strongly not only on the silica characteristics but also on the melt viscosity of the PMMA. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 87: 1541–1553, 2003     

Thermal and chemical analysis of flammability and combustibility of fir wood in cone calorimeter coupled to FTIR apparatus

This paper deals with the thermal degradation of fir wood in a cone calorimeter under well‐ventilated atmosphere used with a piloted ignition. The thermal and chemical sample decompositions were studied with heat fluxes varying from 15 to 60 kW m^?2. With the cone calorimeter results and equations found in literature, the significant parameters of fir wood sample flammability and combustibility were deduced from ignition time (t_ig), mass loss and gas analysis. These parameters are thermal response parameter, critical heat flux, ignition surface temperature, thermal thickness, mass loss rate, thermal inertia, effective heat of combustion, heat release rate, heat of gasification and others. Moreover, during each experiment, the main gaseous species emissions were continuously and simultaneously monitored. Furthermore, the solid degradation and combustion process for fir wood were described in details. Experimental results from cone calorimeter were compared with data found in literature, and generally, a quite good accordance was found between the both sets of results. Copyright © 2013 John Wiley & Sons, Ltd.     

Enhancement of fire retardancy properties of glass fibre–reinforced polyesters composites

This paper presents the results of an experimental investigation on the fire retardancy properties of glass fibre–reinforced polyester (GFRP) composites with bisphenol‐A vinylester and isophthalic polyester as matrices and low electrical conductivity E‐glass fibres as reinforcement. The fire protection systems tested were alumina trihydrate (ATH), decabromodiphenyl ether (DBDE), and antimony trioxide (Sb₂O₃). A mass loss cone calorimeter was used to obtain the properties of heat release rate (HRR), peak HRR, total heat released, total mass loss, time to ignition, and time of combustion. Moreover, limiting oxygen index (LOI), UL‐94, and glow‐wire tests were also performed. The fire tests were carried out in order to investigate if the combination of ATH and DBDE could have “additive,” “antagonistic,” or “synergistic” effects on the flame retardant properties of the GFRP studied in this work. In addition, the influence of the ATH content variation on flame retardant properties was also evaluated. The results indicate that the sole addition of ATH at 47.7 phr could lead to the complete inhibition of the composites ignition, while the materials containing DBDE exhibit ignition and flame propagation in the cone calorimeter test.     

An investigation into the effects of gravity level on rate of heat release and time to ignition

Two experiments were performed on board an aircraft flying repeated parabolic trajectories to generate free-fal conditions. The first experiment investigates the way in which rate of heat release (RHR) varies with gravity for a candle flame under an imposed low-speed flow. In line with previous studies of flame spread rate it has been shown that rate of heat release drops significantly in imcrogravity. The heat loss due to radiation decreases by a larger proportion than that due to non-radiative processes indicating a lower flame temperature. The RHR from a microgravity flame is flow rate dependent, increasing for increased flow rate at air speeds under 0.03 ms^?1. For the geometry used in this experiment hypergravity caused only a small increase in RHR. The second experiment studied the ignitability of thermoplastics under an imposed radiant heat flux. The ignition test apparatus consists of a conical spiral heating element positioned horizontally above the sample, a continuous spark ignition source and a removable heat shield. Experiments were conducted in a sealed pressure chamber on samples of either PMMA or POM, 1.5 mm thick, with a ceramic backing. There is some indication that gravity influences the time to ignition for some materials.     

无卤阻燃HIPS的研究

采用熔融法制备包括可膨胀石墨(EG)、红磷(RP)、氢氧化铝(ATH)体系的阻燃高抗冲聚苯乙烯(HIPS)复合材料;采用锥形量热仪、氧指数、垂直燃烧法研究其对HIPS的阻燃性能的影响。结果表明:HIPS/EG/RP-ATH复合材料的热释放速率及其峰值。质量损失速率等燃烧性能参数继续降低,且火灾性能指数和氧指数大幅提高,UL 94垂直燃烧可以达到FV-0级;结合复合材料燃烧残余物形态,发现EG和RP之间具有明显的协同阻燃效应。     

Modelling of heat release rate in upholstered furniture fire

Many fatal residential fires started from burning upholstered furniture, and so upholstered furniture fire has been studied rather extensively in developed countries. As many upholstered furniture were made in China, the hidden fire risk should be studied more. In this paper, full‐scale experiments on the burning of upholstered furniture manufactured in China were conducted and analyzed. The oxygen consumption method was used to measure the heat release rate in a room calorimeter. An ignition source of a 20‐kW gasoline pool fire of 0.2‐m diameter was used to test square foam cushions and 4‐seater sofas. A model of heat release rate predicting upholstered furniture fire in a room was developed on the basis of earlier Swedish works. Results were then used to justify the application of the Combustion Behaviour of Upholstered Furniture model to predict the heat release rate of furniture manufactured in China. The numerical values of key parameters in the model were determined. It is proposed to build up a database that can be used to model heat release rates upon burning furniture. Detailed procedures are illustrated in this paper.     

Rate of heat release by oxygen consumption in an open test arrangement

Equipment has been developed for measuring the rate of heat release from building materials in an open test arrangement. The method is based on an oxygen consumption technique. A vertical sample is placed under an open hood in which the combustion gases and a certain amount of air are collected. The decrease in oxygen concentration and the mass flow of the gases are measured in the exhaust duct. The rate of heat release is then calculated. The equipment has been calibrated with good agreement between input and measured effects. The total response time for the system is 10s. The method has been used for testing building materials at radiation intensities up to 5W Cm^?2. It is able to distinguish between different board materials, and the repeatability is good, The paper describes the equipment, including the weighing of a burning sample and the selection of test condition. Smoke and gas analysis can be added when desirable. Some test results with building materials are also presented.     

Fire retardant properties of intumescent polypropylene composites filled with calcium carbonate

This study was aimed to investigate the influence of calcium carbonate (CaCO₃), a widely used filler, on the fire retardancy of intumescent polypropylene composites. Two intumescent systems based on (1) mixture of ammonium polyphosphate (APP) and pentaerythritol and (2) surface‐modified APP (m‐APP) were examined. In terms of steady heat release rate, total heat evolved, and fire growth index determined by mass loss calorimetry, m‐APP performed markedly superior to APP‐pentaerythritol. The presence of CaCO₃ in both intumescent formulations caused significant losses in fire retardant performance assessed by mass loss calorimetry, limiting oxygen index and UL‐94 tests. Peak rates of heat release and mass loss during combustion, and total heat evolved on combustion were increased, whereas time to ignition was decreased. Characterization of fire residues ascribed the mechanism of deterioration in fire retardancy to the formation of porous and nonexpanded crystalline calcium phosphate/CaCO₃ residues during combustion rather than the amorphous protective intumescent chars formed in the absence of CaCO₃. POLYM. ENG. SCI., 2011. © 2011 Society of Plastics Engineers     

Comparison of cone and OSU calorimetric techniques to assess the flammability behaviour of fabrics used for aircraft interiors

Two test methods for measuring the heat release rate, HRR have been compared on fabric composites used for aircraft interior materials as side‐wall panels. These methods are based on the principles of direct measurement of the convective and radiant heat by thermopiles using an Ohio State University (OSU) calorimeter, and oxygen consumption using a cone calorimeter. It has been observed when tested by standard procedures, cone results at 35 kW/m² incident heat flux do not correlate with OSU results at the same heat flux. This is because in the cone calorimeter, the sample is mounted horizontally whereas the OSU calorimetric method requires vertical sampling with exposure to a vertical radiant panel. A further difference between the two techniques is the ignition source—in the cone it is spark ignition, whereas in the OSU it is flame ignition; hence, samples in the OSU calorimeter ignite more easily compared to those in the cone under the same incident heat fluxes. However, in this paper we demonstrate that cone calorimetric exposure at 50 kW/m² heat flux gives similar peak heat release results as the 35 kW/m² heat flux of OSU calorimeter, but significantly different average and total heat release values over a 2 min period. The performance differences associated with these two techniques are also discussed. Moreover, the effects of structure, i.e. type of fibres used in warp/weft direction and design of fabric are also analysed with respect to heat release behaviour and their correlation discussed. Copyright © 2005 John Wiley & Sons, Ltd.     

Experimental investigation and numerical modelling of the fire performance for epoxy resin carbon fibre composites of variable thicknesses

This paper applies a unique integrated approach to determine the flammability properties of a composite material (epoxy with carbon fibre) and compares its fire behaviour at two different thicknesses (2.1 and 4.2 mm) by performing small scale (thermo‐gravimetric analysis (TGA)/Fourier transform infrared radiation) and meso‐scale tests (cone calorimeter). For small‐scale tests, experiments were conducted in nitrogen using TGA coupled to gas analysis by Fourier transform infrared radiation. These results allow the determination of thermal stability, main degradation temperature and main gaseous emissions released during the thermal degradation. For meso‐scale tests, experiments were carried out using a cone calorimeter with sample dimensions of 100 × 100 mm at five heat fluxes (30, 40, 50, 60 and 70 kW/m²). The results show that the ignition time increases with an increase in the thickness of the material. Relative hazard classification of the fire performance of the current composites has also been compared with other materials using parameters obtained elsewhere. In addition, the effective ignition, thermal and pyrolysis properties obtained from the ignition and mass loss rate experiments for the 4.2‐mm thick samples were used in a numerical model for pyrolysis to predict well ignition times, back‐surface temperatures and mass pyrolysis rates for all heat fluxes as well as for the 2.1‐mm thick samples. Note that the ignition temperature obtained in the cone agrees with the main degradation temperature in the TGA. The flammability properties deduced here can be used to predict the heat release rate for real fire situations using CFD modelling. Copyright © 2016 John Wiley & Sons, Ltd.     

Thermal degradation of epoxy resin/carbon fiber composites: Influence of carbon fiber fraction on the fire reaction properties and on the gaseous species release

The thermal degradation of epoxy resin/carbon fiber composites has been performed in ISO 5660 standard cone calorimeter using a piloted ignition. Two kinds of composites that differ by their volume fractions in carbon fiber (56 and 59 vol.%) were tested in this study. The cone calorimeter irradiance level was increased up to 75 kW m^?2 to characterize the carbon fiber volume fraction influence on the composite thermal degradation. Thus, main flammability and combustibility parameters were determined and calculated such as mass loss, mass loss rate, ignition time, thermal response parameter, ignition temperature, thermal inertia, and heat of gasification. As a result, all the characteristic parameters for the thermal resistance of composites were decreased when the carbon fiber volume fraction increased. Moreover, the main gaseous products (such as NO, CO, CO₂, HCN, H₂O, and lightweight hydrocarbons) emitted as well as the oxygen consumption during the composite thermal decomposition were also quantified simultaneously with a portable gas analyzer and a Fourier transform infrared spectrometer. The main species emission yields calculated from the gas analysis results increased slightly when the carbon fiber volume fraction was increased in the initial sample. The epoxy composite was represented as a sooty material with a significant production of soot particles during the combustion process. Furthermore, heat release rate, total heat release, and effective heat of combustion were calculated by using the oxygen consumption calorimetry technique. The results obtained showed that a small increasing of composite carbon fiber amount induced a sharp decrease of heat release rate and total heat release. Copyright © 2014 John Wiley & Sons, Ltd.     

Effects of variations in incident heat flux when using cone calorimeter test data for prediction of full‐scale heat release rates of polyurethane foam

The development of methods to predict full‐scale fire behaviour using small‐scale test data is of great interest to the fire community. This study evaluated the ability of one model, originally developed during the European Combustion Behaviour of Upholstered Furniture (CBUF) project, to predict heat release rates. Polyurethane foam specimens were tested in the furniture calorimeter using both centre and edge ignition locations. Input data were obtained using cone calorimeter tests and infrared video‐based flame area measurements. Two particular issues were investigated: how variations in incident heat flux in cone calorimeter tests impact heat release rate predictions, and the ability of the model to predict results for different foam thicknesses. Heat release rate predictions showed good agreement with experimental results, particularly during the growth phase of the fire. The model was more successful in predicting results for edge ignition tests than for centre ignition tests and in predicting results for thinner foams. Results indicated that because of sensitivity of the burning behaviour to foam specimen geometry and ignition location, a single incident heat flux could not be specified for generating input for the CBUF model. Potential methods to determine appropriate cone calorimeter input for various geometries and ignition locations are discussed. Copyright © 2014 John Wiley & Sons, Ltd.