•Fire experiments and simulations carried out in a full-scale tunnel.•Maximum smoke temperature data beneath ceiling obtained with constraint effect.•Transverse distance factor is included into the current equations.•Modified correlation agrees with the previous data.A sequence of tests and simulations with varying transverse fire locations were conducted in a full-scale tunnel to investigate the constraint effect of sidewall on the maximum smoke temperature distribution under a tunnel ceiling. Then, the simulated results were comprehensively compared with both those of the full-scale tests and the model-scale experiments from previous studies. The results of the full-scale experiment show that the longitudinal maximum smoke temperature rise distribution decreases can be approximated by a power function. However, the numerical simulation results indicate that an exponential distribution may be plausible. The normalized ceiling jet temperature rise at the impingement point displays an exponential variation with the distance between the fire source and the sidewall. Meanwhile, regression models taking the constraint effect of sidewall into account was developed to predict the ceiling jet impingement temperature in tunnel fires.

•Hollow mesoporous silica with uniform size were prepared by a low-cost method.•TG-IR results was used to reveal thermal degradation of SiO2/PS nanocomposites.•Hollow mesoporous silica exhibited excellent removal of aromatic volatiles.In the paper, hollow mesoporous silica (HMS) spheres were prepared by an environment-friendly and low-cost method using cheap sodium silicate as silica precursor and inexpensive cationic polystyrene spheres as interior templates. Hollow structure with uniform size were characterized by TEM and SEM images. Nitrogen adsorption-desorption isotherm was used to confirm mesoporous structure with BET surface area of 424 m2/g and narrow pore size distribution. TG-IR was utilized to investigate the influence of HMS spheres on the removal of aromatic volatiles. The as-prepared HMS spheres exhibited high removal ability of aromatic volatiles, mainly attributed to interior hollow for facilitating aggregation of aromatic volatiles to smoke particles and external mesoporous for strongly adsorbing aromatic volatiles.

A series of shredded paper fire experiments were conducted by means of a calorimeter. The mass loss rate and heat release rate were measured. The flame spread process was recorded, which shows that the flame spread process can be divided into four typical stages, and the mean spread rates along different directions were obtained from the observed combustion process. Based on the mean flame spread rate, a mathematical model for predicting the burning surface as a function of time during the four stages is established. Combining this model with the effective heat of combustion calculated from measured mass loss rate and heat release rate, an improved model to predict the heat release rate as a function of time was developed. In this model, the linear relationship between heat release rate and burning surface is found, and the predicted result agrees well with the measured heat release rate.

•Pioneering study of lithium-ion battery fire at sub-standard atmospheric pressure.•Comparisons with the fire hazards at the standard atmospheric conditions.•Ignition, mass loss and HRR are related to the SOC and pressure.•Empirical correlations are established to link the hazard parameters with pressure.•The uncertainty in the heat release rate measurement is highlighted.The fire behavior of lithium-ion battery is affected by the environment conditions. In this paper, an experimental study is performed to assess the fire hazards of lithium-ion batteries at different atmospheric pressures by means of the in-situ calorimeters built in a sea-level city Hefei (100.8 kPa, 24 m) and a high altitude city Lhasa (64.3 kPa, 3650 m), respectively. The fire hazards of lithium-ion batteries were characterized by measuring the ignition time, mass loss, heat release rate (HRR), and total heat release (THR). From the results, the ignition time of single battery decreases with the ascending of the state of charge (SOC), whiles the mass loss, and ejection energy increase with that at two pressures. The increment of altitude causes the battery to ignite faster, while the mass loss, heat release rate and total heat release both for single battery and bundle batteries decrease at low pressure. The total heat release in the bundle increases with the battery numbers in a power function. The coefficient of the proportionality is pressure dependent.Download high-res image (169KB)Download full-size image

The use of lithium batteries requires understanding their fire and explosion hazards. In this paper, a report is given on an experimental study of the combustion characteristics of primary lithium batteries. Burning tests of single and bundles of primary lithium batteries were conducted in a calorimeter to measure their heat release rates when exposed to an irradiance of 20 kW m−2. Several variables including time to ignition, mass loss, heat release rate and plume temperature were measured to evaluate the ignition and combustion characteristics. The burning batteries were observed to have flame temperatures in excess of 1,200°C and to release corrosive compounds. The experimental results show that the combustion efficiency, carbon dioxide yield and mass loss are proportional to the number of batteries in the bundle. The total heat released by battery bundles was deduced empirically to be proportional to the number of batteries with a power of 1.26. The results provide experimental basis for the development of fire protection measures during the use, storage and distribution of primary lithium batteries.

Polymer/graphene-analogous nanosheet composites have great potential for improving their physical and mechanical properties during the past few years. Herein, ultrathin molybdenum disulfide (MoS2) nanosheets were simultaneously exfoliated and non-covalently modified by ultrasonication in an aqueous solution of chitosan. The chitosan-modified MoS2 (CS-MoS2) nanosheets were then transferred from the aqueous solution to tetrahydrofuran by a simple solvent-exchange method for the fabrication of epoxy (EP) nanocomposites. Transmission electron microscopy and scanning electron microscopy were performed to display the homogeneous dispersion of CS-MoS2 in an EP matrix. On incorporating 2 wt% CS-MoS2 into an EP matrix, EP nanocomposites exhibited reductions of up to 43.3% and 14.6% in peak heat-release rate and total heat release derived from cone calorimeters compared to those of neat EP, respectively. Moreover, toxic volatiles, such as hydrocarbons, aromatic compounds and CO, that escaped from the flaming EP nanocomposites were decreased compared to that of neat EP, demonstrating the higher smoke safety. Combined with the analyses of char residues and thermal stability of EP nanocomposites, the reduced fire hazards of EP nanocomposites could be attributed to the nano-barrier effects of MoS2, which could effectively inhibit the release of combustible gas to support burning and restrain the effusion of volatile toxic substances that cause the majority of deaths in fires.

The boiling point, flashpoint, and flammability limit are key parameters to evaluate the combustion behavior of flammable liquids. In this study, the boiling point (TB), the flashpoint (TF), and the lower flammable limit (LFL) of two multiple-component fuels (diesel and Jet A) and two single-component fuels (n-hexanol and n-decane) were measured at low pressures ranging from 35 to 101 kPa. The dependences of TB, TF, and LFL on pressure have been theoretically derived to explain the experimental measurements. In addition to the observation that both boiling point and flashpoint decrease with decreasing pressure, the measurements also revealed that the open-cup and closed-cup flashpoints decrease at different rates. The lower flammability limit, on the other hand, was shown to increase with the decreasing of pressure. The measurements of the lower flammability limit versus pressure were well correlated with different theoretical formulas proposed in the literature and the current study. The relationships among TB, TF, and LFL at low pressure are also discussed and verified against the measurements.

We have measured the shape of the luminous zone in a laminar jet diffusion flame burning methane, ethylene, and propane in quiescent air in the pressure range 0.02-0.1 MPa. Soot emission by the flame was not permitted. The flame became more slender and luminous as the pressure increased. At relatively high fuel flow rates, the ethylene and propane flame heights increased with pressure. At low fuel flow rate, the flame height decreased as pressure increased for all three fuels. At high fuel flow rate, the methane flame height first decreased and then increased with pressure, due to the low tendency of methane to form soot. Finally, we observed a tendency toward decreasing – increasing – decreasing flame height at certain fuel flow rates and in certain pressure ranges.

In this work, GO was functionalized by a hyper-branched flame retardant, which was synthesized by the reaction of N-aminoethyl piperazine and di(acryloyloxyethyl)methylphosphonate. Subsequently, the resultant functionalized GO (FGO) was incorporated into the cross-linked polyethylene (XLPE) to enhance the flame retardancy of the matrix. Transmission electron spectroscopy images indicated that FGO exhibited uniform dispersion in XLPE matrix and strong adhesion with the matrix by cross-linking, which improved barrier effect due to reduced heat release and the free radical transfer between the matrix and graphene nanosheets. The incorporation of FGO into XLPE matrix endowed polymer composites with flame retardancy and thermal stability. In addition, the homogeneous dispersion of functionalized GO with a hyper-branched flame retardant in the polymer matrix improved the antioxidation and mechanical properties of XLPE–FGO nanocomposites compared to the XLPE–GO samples, as demonstrated through the oxidative induction temperature and time test, oven aging test and mechanical test.

A flame detection synthesis algorithm is presented in this paper. The temporal and spatial of flames, such as flame movement, color clues and flame area variation are incorporated into the scheme to detect fires in video frames. Firstly, Choquet fuzzy integral was adopted to integrate color features and texture feature for extracting dynamic regions from video frames. Secondly, mean filtering was used to smooth RGB value of the video frame pixels and detected dynamic regions were filtered by a flame color filtering algorithm to extract candidate flame regions. Finally, a flame area variation identification algorithm was used to distinguish true flames from candidate flame regions. Experiments show that the proposed method is effective, robust and remains with strong anti-jamming performance against brightness variation. The processing rate of the flame detection method achieves 24 frames per second with image size of 320 × 240 pixels.

Ethyl cellulose, a widely used bio-degradable shell material, microencapsulated ammonium polyphosphate (MAPP) was added to the bio-degradable poly(butylene succinate) (PBS) to improve its flame retardancy, compatibility, and thermal stability. The MAPP was well characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy (SEM), water contact angle, and thermogravimetric (TG) analysis. The SEM results indicate the improved dispersion of MAPP into PBS matrix and the formation of the strong interfacial adhesion between MAPP and PBS than APP. With the incorporation of MAPP and char-forming agent into PBS, the limiting oxygen index of the composite was increased to 35.5 %, and the sample can pass the UL-94 V-0 rating, while the un-microencapsulated counterpart cannot reach the rating. The cone calorimeter test showed that the peak heat release rate was decreased by 46.7 % and the burning time was also prolonged compared to the pure PBS. The increased melt flow index and rheology test indicated the increase of viscosity and the improvement of anti-dripping properties. Moreover, the mechanical properties and thermal stability of MAPP composite were also obviously enhanced after the microencapsulation by mechanical, dynamical mechanical thermal analysis, and TG analysis.

To improve the video fire detection rate, a robust fire detection algorithm based on the color, motion and pattern characteristics of fire targets was proposed, which proved a satisfactory fire detection rate for different fire scenes. In this fire detection algorithm: (a) a rule-based generic color model was developed based on analysis on a large quantity of flame pixels; (b) from the traditional GICA (Geometrical Independent Component Analysis) model, a Cumulative Geometrical Independent Component Analysis (C-GICA) model was developed for motion detection without static background and (c) a BP neural network fire recognition model based on multi-features of the fire pattern was developed. Fire detection tests on benchmark fire video clips of different scenes have shown the robustness, accuracy and fast-response of the algorithm.Highlights► Proposed a robust fire detection algorithm based on the color, motion and pattern characteristics of fire targets. ► Developed a rule-based generic color model. ► Developed a Cumulative Geometrical Independent Component Analysis (C-GICA) model for motion detection. ► Developed a BP neural network fire recognition model based on the multi-features of the fire pattern.

This paper presents a new type of flame-retardant ultraviolet (UV)-cured epoxy acrylate (EA) that contains microencapsulated phase-change materials (Micro-PCM); the Micro-PCM, which is based on a paraffin core and a melamine−formaldehyde (MF) shell, was synthesized via an in situ polymerization method. To improve the thermal stability of the UV-cured EA/Micro-PCM composite, dimethyl methyl phosphonate (DMMP), with or without octavinyl polyhedral oligomeric silsesquioxane (OVPOSS), was introduced into it. The Micro-PCM properties were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA); the results showed that the MF was successfully fabricated on the surface of the core material, and the Micro-PCM contained ∼70 wt % core material. The thermal stabilities of the UV-cured EA/Micro-PCM composites and the flame-retardant UV-cured EA/Micro-PCM composites were evaluated by microscale combustion calorimetry (MCC) and TGA, and the results indicated that, when the content of Micro-PCM is <30 wt % in the UV-cured EA, the UV-cured EA could protect paraffin from evaporation obviously; in addition, the DMMP and OVPOS showed a great synergistic effect to improve the thermal stability of the UV-cured EA/Micro-PCM composite.

The influences of metal (iron, magnesium, aluminum, and zinc) on thermal properties for paraffin/intumescent flame retardants (IFR) as a phase change material were studied in this paper. Thermogravimetric analysis (TGA), thermogravimetric analysis−Fourier transform infrared spectrometry (TGA-FTIR), microscale combustion calorimetry (MCC), cone calorimetry (CONE), and differential scanning calorimetry (DSC) were used to characterize the thermal properties of the sample. The results revealed that metal could affect the thermal degradation and increase the char yield for a paraffin/IFR system. The volatilized products for the combustible gases were decreased, and carbon dioxide was increased for paraffin/IFR with metal compared to that without metal. Also, the flame retardant efficiency of IFR in paraffin could be improved by adding metal. However, the changes of the thermal properties for the metal−PCM were not in accord with increasing metal in the paraffin/IFR system. Also, the flame retardant mechanism for paraffin/IFR with metal was proposed.

A sequence of experiments involving a fan with varying inclined angles and distances from a fire source were conducted in a full-scale tunnel to investigate the characteristics of smoke movement with forced ventilation by a movable fan. The phenomenon of smoke movement was described by a laser visualization technique, and the backlayering in the presence of ventilation is discussed in this paper. The results of the experiment demonstrate that the distance between the movable fan and the fire source has a critical range, where the effects of smoke exhaust on reducing the maximum temperature under the ceiling and preventing the backlayering are more significant when the fan was placed in this distance range. However, the disadvantage of faster smoke moving downstream is that it might be adverse to a safe evacuation during tunnel fires. In addition, it was determined that the performance of smoke exhaust in a horizontal path was better than that of an inclined angle within a limited distance, but there was no obvious difference when the distances were large.

•A newly constructed SPI-TOFMS was used to investigate the pyrolysis of PE for the first time.•HZSM-5, HUSY and MCM-41 show the selectivity of generating light alkenes such as butylenes (m/z 56) and pentene (m/z 70).•Both polymer catalytic and non-catalytic decomposition can achieve concurrently.•The content of zeolites and pyrolysis temperatures play crucial roles in products distribution of PE/catalyst.•The addition of MCM-41 will only increase the fire risk slightly.The effects of temperatures, catalysts, and catalyst contents on polyethylene (PE) pyrolysis were investigated by using single-photon ionization time-of-flight mass spectrometry (SPI-TOFMS). The mass spectra of pyrolyzed PE and PE/catalysts from 300 °C to 800 °C illustrate that the pyrolysis reactions were apparently promoted and varied by introducing HZSM-5, HUSY, and MCM-41. As microporous catalysts, HZSM-5 and HUSY were found to accelerate the BTX formation at 400 °C, which could not be observed for pure PE until 800 °C. With the existence of MCM-41, only alkenes were produced below 600 °C. The pyrolysis processes could to be accelerated by adding catalysts. Principal components analysis (PCA) was finally employed to identify the main factors with influence on the products distribution. Analytical results showed that the yield of the majority of products could be affected by different experimental conditions, that the type of catalysts makes the most significant influence. The impact of different types of catalysts on fire hazard of PE was studied by using the cone calorimeter. The results indicated that the time to ignition (TTI) and the peak heat release rate (pHRR) were changed remarkably. It is worth noting that with the addition of MCM-41, the pHRR is the minimum.Download high-res image (192KB)Download full-size image

To study the difference of solid fuel fire characteristics at different altitudes, two series of fire experiments of cardboard boxes filled with shredded office paper were conducted separately in Lhasa (altitude: 3650 m; air pressure: 65 kPa) and Hefei (altitude: 24 m, air pressure: 100.8 kPa), using a specially designed igniter. The measured parameters in the experiments include mass loss and flame axis temperature. Fuel load quantity and configuration were varied in the experiments. The results of the study indicate a likelihood that an ignition will result in smoldering fire at the high altitude. There is also likelihood that incipient phase may occur before the onset of full flaming combustion regardless of the altitude. The fuel mass loss fraction of flaming fires was found to follow a simple form of correlation with time when normalized over the half fuel consumption time, which was found to be inversely proportional to four-third power of the ambient pressure.

Polymer/graphene-analogous nanosheet composites have great potential for improving their physical and mechanical properties during the past few years. Herein, ultrathin molybdenum disulfide (MoS2) nanosheets were simultaneously exfoliated and non-covalently modified by ultrasonication in an aqueous solution of chitosan. The chitosan-modified MoS2 (CS-MoS2) nanosheets were then transferred from the aqueous solution to tetrahydrofuran by a simple solvent-exchange method for the fabrication of epoxy (EP) nanocomposites. Transmission electron microscopy and scanning electron microscopy were performed to display the homogeneous dispersion of CS-MoS2 in an EP matrix. On incorporating 2 wt% CS-MoS2 into an EP matrix, EP nanocomposites exhibited reductions of up to 43.3% and 14.6% in peak heat-release rate and total heat release derived from cone calorimeters compared to those of neat EP, respectively. Moreover, toxic volatiles, such as hydrocarbons, aromatic compounds and CO, that escaped from the flaming EP nanocomposites were decreased compared to that of neat EP, demonstrating the higher smoke safety. Combined with the analyses of char residues and thermal stability of EP nanocomposites, the reduced fire hazards of EP nanocomposites could be attributed to the nano-barrier effects of MoS2, which could effectively inhibit the release of combustible gas to support burning and restrain the effusion of volatile toxic substances that cause the majority of deaths in fires.