Flame Duration Research Articles

A Study of Cotton Dust Mixed with Wood Dust for Bio-Briquette Fuel

Various textile-industrial wastes such as cotton wastes, polyester fibres, lumps and old rags can be a source of energy. Cotton dust seems to be one of the most interesting bio-waste energy sources because its shares of the high heat energy and organic material. This paper presents physical and mechanical properties of briquette mixed with cotton dust (CD) and wood dust (WD). The various ratios of CD:WD (0:100, 20:80, 40:60, 60:40, 80:20 and 100:0 % by weight) were investigated. The dimensional of hexagon briquette specimen was 5 cm (outer diameter) and 2.5 cm (hollow inner diameter) with the height of 10 cm was subjected to physical and mechanical tests. Results of physical performance test showed that the briquette specimens with ratio of CD:WD (1:0) gave the lowest ignition temperature, smoke temperature and duration of flame out time of 280°C, 275°C and 6.30 min/2gm respectively. While, the briquette specimens made with ratio of 0.2:0.8 gave the highest heat energy of 3,960 cal/g. However, the result of mechanical properties showed that and briquette specimens made with the ratio of 0.2:0.8 was the highest compressive strength of 9.80 N/mm2. This study indicated that CD can be used as a substitute material for bio-briquette fuels.

Burn or rot: leaf traits explain why flammability and decomposability are decoupled across species

SummaryIn fireprone ecosystems, two important alternative fates for leaves are burning in a wildfire (when alive or as litter) or they get consumed (as litter) by decomposers. The influence of leaf traits on litter decomposition rate is reasonably well understood. In contrast, less is known about the influence of leaf traits on leaf and litter flammability. The aim of this study was twofold: (i) to determine which morphological and chemical leaf traits drive flammability and (ii) to determine whether different (combinations of) morphological and chemical leaf traits drive interspecific variation in decomposition and litter flammability and, in turn, help us understand the relationship between decomposability and flammability.To explore the relationships between leaf traits and flammability of individual leaves, we used 32 evergreen perennial plant species from eastern Australia in standardized experimental burns on three types of leaf material (i.e. fresh, dried and senesced). Next, we compared these trait–flammability relationships to trait–decomposability relationships as obtained from a previous decomposition experiment (focusing on senesced leaves only).Within the three parameters of leaf flammability that we measured, interspecific variation in time to ignition was mainly explained by specific leaf area and moisture content. Flame duration and smoulder duration were mostly explained by leaf dry mass and to a lesser degree by leaf chemistry, namely, nitrogen, phosphorus and tannin concentrations.The variation in the decomposition constant across species was unrelated to our measures of flammability. Moreover, different combinations of morphological and chemical leaf properties underpinned the interspecific variation in decomposability and flammability. In contrast to litter flammability, decomposability was driven by lignin and phosphorus concentrations.The decoupling of flammability and decomposability leads to three possible scenarios for species’ influence on litter fates: (i) fast‐decomposing species for which flammability is irrelevant because there will not be enough litter to support a fire; (ii) species with slow‐decomposing leaves and a high flammability; and (iii) species with slow‐decomposing leaves and a low flammability. We see potential for making use of the decoupled trait–decomposition–flammability relationships when modelling carbon and nutrient fluxes. Including information on leaf traits in models can improve the prediction of fire behaviour. We note that herbivory is another key fate for leaves, but this study was focused on fire and decomposition.

Comparison of explosion characteristics between hydrogen/air and methane/air at the stoichiometric concentrations

Hydrogen and methane that are largely different in gas activity are two common explosion hazards. Understanding their explosion characteristics is the foundation for acknowledging explosion hazard effects of hydrogen and methane. In this study, the explosion experiments of hydrogen/air and methane/air for different gas volumes have been carried out in a closed tube. The objectives of this study are to examine the explosion characteristics of hydrogen and methane at the stoichiometric concentrations and to acknowledge explosion hazard effects based on the experimental data in the tube. According to the experimental results, the flame propagation speed of hydrogen/air explosion is higher than that of methane/air, while the flame duration of methane/air is longer than that of hydrogen/air. It is indicated that the higher reactive hydrogen can cause massive burst damage, while the lower reactive methane can lead to a lasting harm. In the experimental tube, peak overpressures and maximum rates of pressure rise (dp/dt)max of hydrogen/air explosion for different gas volumes change greatly along the axial direction of the tube and reach the maximums at the end of the obstacles region. The pressure maximums are up to more than 1.5 MPa. While peak overpressures and (dp/dt)max of methane/air explosion change relatively slowly along the axial direction of the tube and their maximums appear beyond the original premixed gas zone. The pressure maximums just reach about 0.38 MPa. For all premixed zones, peak overpressures, maximum rates of pressure rise (dp/dt)max of hydrogen/air explosion and speeds of shock wave are significantly larger than those of methane/air, except for 1.5 m premixed zone for which peak overpressures, (dp/dt)max and speeds of shock wave of hydrogen/air and methane/air are very close relatively beyond the premixed gas zone due to too little combustible gas volume. As the combustible gas volume increases, maximum pressures and maximum rates of pressure rise of hydrogen/air explosion rise more significantly than those of methane/air because of different gas activity and flame acceleration characteristic.

Spray and combustion of waste cooking oil biodiesel in a compression-ignition engine

An experimental study was carried out to compare the spray and combustion characteristics of waste cooking oil biodiesel with those of conventional diesel in a common-rail direct-injection compression-ignition engine. The indicated mean effective pressure of approximately 0.7 MPa was tested under an engine speed of 800 r/min. The fuels were injected at an injection timing of −5 crank angle degree after top dead center with injection pressures of 80 and 160 MPa. The experiments were performed to investigate the combustion and emission characteristics in a metal engine, while spray and combustion flame characteristics in an optical engine. The morphological and compositional features of particulate matter were also analyzed by using transmission electron microscopy and thermogravimetric analysis. The direct imaging of the spray indicated a longer injection delay for waste cooking oil biodiesel. However, it exhibited longer liquid penetration length and narrower spray angle than diesel as the spray developed. Waste cooking oil biodiesel combustion showed a longer ignition delay with a slightly lower peak of in-cylinder pressure and heat release rate than diesel due to the deteriorated atomization and evaporation of fuel spray. In terms of emission, waste cooking oil biodiesel showed benefits in reduction of carbon monoxide, unburned hydrocarbon and particulate matter emissions. The particulate matter from waste cooking oil biodiesel was composed of smaller primary particles and more volatile organic fraction than diesel soot. The combustion flame imaging verified the retarded combustion phase of waste cooking oil biodiesel. Waste cooking oil biodiesel combustion showed lower flame luminosity accompanied by shorter visible flame duration, at both injection pressures. The flame spatial fluctuation and flame nonhomogeneity were also lower for waste cooking oil biodiesel.

The role of leaf traits in determining litter flammability of south-eastern Amazon tree species

Leaf traits can limit or promote flammability, but how these traits vary and influence forest flammability in humid tropical forests is unknown. Species within the south-eastern transitional forests of the Brazilian Amazon are experiencing fire, particularly surface fires, with greater frequency and severity than historically recorded. In this study, the leaf traits and consequent burning characteristics of the 17 most abundant species in a transitional forest in Mato Grosso, Brazil were analysed through controlled combustion experiments and leaf trait measurements. Mean maximum flame height (range 52–108 cm), flaming duration (range 21–71 s) and mass loss (range 82–97%), which relate to a fuel’s combustibility and consumability, varied substantially across species. Measured leaf traits, mainly surface area and volume, accounted for 78% of this variability. The most flammable species were those with thin, lightweight and loosely packed leaves, which produced rapid, intense fires that consumed larger fuel amounts. The least flammable species had thick, large and densely packed leaves. In diverse tropical forests, analysing the relationship between species-specific leaf traits and flammability will yield insights into fire behaviour and future forest composition in a frontier zone where exposure to anthropogenic fire is high.

Fuel Element Combustion Properties for Live Wildland Utah Shrubs

Current field models for wildfire prediction are mostly based on dry or low-moisture fuel combustion research. To better study the live fuel combustion behavior, a laminar flow flat-flame burner was used to provide a convection heating source to ignite an individual live fuel sample. In this research project, four Utah species were studied: Gambel oak (Quercus gambelii), canyon maple (Acer grandidentatum), big sagebrush (Artemisia tridentata), and Utah juniper (Juniperus osteosperma). Leaf geometrical parameters measured included individual leaf total mass, thickness, leaf width, leaf length, and moisture content. Time-stamped images of combustion behavior along with time-dependent mass data were recorded via a LabVIEW system. Combustion characteristics were determined by an automated MATLAB routine modified for analyzing Utah species images of burning fuel samples, including time to ignition, time of flame duration, time to maximum flame height, time to burnout, and maximum flame height. Qualitative results included various combustion phenomena like bursting, brand formation, and bending. Sparks accompanied with leaf material bursting out were observed for Utah juniper sample combustion mostly before ignition, especially for segments cut from the top of the branch. Quantitative results included exploration of the best prediction equations for leaf geometrical properties and combustion characteristics. A beta distribution was used to predict the distribution of dry mass. Multiple linear regressions were performed on other leaf geometrical properties and combustion characteristics. Minimized Bayesian information criterion (BIC) value models were achieved by stepwise regression analysis and compared to the previous empirical prediction models.

Devolatilization of a single fuel particle in a fluidized bed under oxy-combustion conditions. Part A: Experimental results

Devolatilization of a single fuel particle and the related flame combustion were studied in a two-dimensional fluidized bed with a quartz wall, allowing visual observation of the conversion process. The aim was to evaluate the devolatilization behavior (ignition, flame temperature, flame life-time, devolatilization time) of different fuels (4 ranks of coal from lignite to anthracite and wood) when replacing O2/N2 by O2/CO2 in O2 volume concentrations from 0% to 40%, at a fixed bed temperature of 1088K using 6mm spherical fuel particles. The volatiles’ flame was recorded by a color video camera to analyze ignition and extinction. The flame temperature was estimated by two-color pyrometry. Two thermocouples were inserted in the fuel particle to measure the temperature at the center and near the surface. Homogeneous and heterogeneous ignition modes, times of devolatilization, and flame duration (flame-life) under different gas atmospheres were analyzed. Results indicate that the mode of ignition of bituminous coal, lignite coal and wood changes when N2 is replaced by CO2. The ignition-delay time is much longer, and the flame temperature is lower in the O2/CO2 atmosphere than in an O2/N2 atmosphere for all the tested fuels. The devolatilization time of the anthracite particle is almost unaffected by the surrounding atmosphere, while for the other fuels this time is generally longer in O2/CO2 than in O2/N2 at the same O2 concentration. The presence of a flame during the volatiles combustion did not accelerate the particle heating, not even at the highest O2 concentration tested (40vol%), however, after the extinction of the flame, the rate of particle heating is significantly affected by the oxygen concentration.

Altered community flammability in Florida's Apalachicola ravines and implications for the persistence of the endangered conifer Torreya taxifolia.

Plant species and communities often reflect historic fire regimes via ecological and evolutionary responses to recurrent fires. Plant communities of the southeastern USA experience a wide array of fire regimes, perhaps nowhere more marked than the juxtaposition of fire-prone uplands and adjacent mesic ravines along Florida’s Apalachicola River. The ravines contain many endemic and disjunct species, most notably the endangered endemic conifer Torreya taxifolia. A rapid decline in T. taxifolia over the past 60 years has been associated with widespread replacement by other tree species. To understand the changes accompanying the shift in ravine composition, we compared leaf litter flammability of nine historic and contemporary species. We measured maximum flame height, flame duration, smoldering duration, mass loss, absorptive capacity, and drying rate. Ordination and perMANOVA suggest the nine species segregated into three distinct groups: the fire-impeding T. taxifolia and Taxus floridana; an intermediate group of three deciduous angiosperms; and a mixed cluster of four flammable species. Results suggest T. taxifolia and T. floridana were fire-impeding species in these communities, while contemporary dominants burn similarly to the upslope pyric species. The increasing presence of fire-facilitating species may portend a shifting fire regime that further imperils T. taxifolia and other rare species in the formerly fire-safe ravines.

수송기관용 오일의 화재위험성에 관한 연구

The purpose of this study is to conduct the study of the combustion and thermal characteristics through transportation oil for the analysis of fire hazard. Transportation oil breaks down into fuels such as diesel for civilian demands, gasoline, DF1(diesel for military), high sulfur diesel(for marine), kerosene and JP1(for aviation), and lubricants like brake fluid, power steering oil, engine oil, and automatic and manual transmission oil. The experiments of flash point, ignition point, flame duration time, heat release rate were carried out using TAG closed cup flash point tester(AFP761), Cleveland open cup auto flash point analyzer(AFP762), KRS-RG-9000 and Dual cone calorimeter. As a result, the fuel's ignition points were lower than lubricants, especially that of gasoline was not conducted as it has below zero one. Gasoline has the highest ignition point of about 600℃, while the other fuels showed 400~465℃. For flame duration time, lubricants had over 300 seconds, but fuels had less than 300 seconds except high sulfur diesel(350 seconds). Total heat release rate ranged 287~462 ㎾/㎡ for lubricants and gasoline showed the highest total heat release rate, 652 ㎾/㎡.

High methane natural gas/air explosion characteristics in confined vessel

The explosion characteristics of high methane fraction natural gas were investigated in a constant volume combustion vessel at different initial conditions. Results show that with the increase of initial pressure, the peak explosion pressure, the maximum rate of pressure rise increase due to a higher amount (mass) of flammable mixture, which delivers an increased amount of heat. The increased total flame duration and flame development time result as a consequence of the higher amount of flammable mixture. With the increase of the initial temperature, the peak explosion pressures decrease, but the pressure increase during combustion is accelerated, which indicates a faster flame speed and heat release rate. The maximum value of the explosion pressure, the maximum rate of pressure rise, the minimum total combustion duration and the minimum flame development time is observed when the equivalence ratio of the mixture is 1.1. Additionally, for higher methane fraction natural gas, the explosion pressure and the maximum rate of pressure rise are slightly decreased, while the combustion duration is postponed. The combustion phasing is empirically correlated with the experimental parameters with good fitting performance. Furthermore, the addition of dilute gas significantly reduces the explosion pressure, the maximum rate of pressure rise and postpones the flame development and this flame retarding effect of carbon dioxide is stronger than that of nitrogen.

Effect of Density on Flame Characteristics of Some Tropical Timbers

Timber has always played an influencing role in the lives of humans. At high temperature and in the presence of air, it burns or decomposes exothermically. The flame characteristics studied were the ignition time, flame duration, flame propagation rate and after- glow time. Wet and oven-dry densities, moisture content and porosity index of these timbers were also measured. The oven-dry density range was 0.256 0.008 g/cm 3 to 1.111 0.039 g/cm 3 in which most of the timbers were of medium density (0.400 - 0.750 g/cm 3 ). Most of the timbers can be described as being fire-tolerant since they have flame propagation rate values below 0.28cm/s. There was somewhat direct relationship between oven-dry density and ignition time, flame duration and afterglow time of these timbers, while an inverse trend exists with flame propagation rate. The use of alternative hardwoods with high density is recommended with its attendant flame characteristics.Tropical timbers, ignition time, flame duration, flame propagation rate, after-glow time.

Flammability of Some Ornamental Species in Wildland–Urban Interfaces in Southeastern France: Laboratory Assessment at Particle Level

Assessment of the flammability of ornamental vegetation (particularly hedges) planted around houses is necessary in light of the increasing urbanization of the wildland-urban interfaces (WUIs) and the high fire occurrence in such areas. The structure and flammability of seven of the species most frequently planted as hedges in Provence (southeastern France) were studied at particle level. Spatial repartition of the different types of fuel particles within plants was assessed by means of the cube method. The leaf flammability was assessed using an epiradiator as a burning device, and measurements of foliar physical characteristics and gross heat of combustion (GHC) helped to explain the results of burning experiments. Co-inertia analysis revealed that species with thin leaves were quick to ignite (Pyracantha coccinea, Phyllostachys sp.) and species with high leaf GHC burned the longest (Pittosporum tobira, Nerium oleander). Species presenting high ignitability (Photinia fraseri, Phyllostachys sp. and Pyracantha coccinea) were characterized by high foliar surface area-to-volume ratio, and species presenting lower ignitability were characterized by high GHC (Pittosporum tobira, Nerium oleander, Cupressus sempervirens). Hierarchical cluster analysis of the flammability variables (ignition frequency, time-to-ignition and flaming duration) categorized the relative flammability of the seven species (including dead Cupressus sempervirens) in five clusters of species from poorly flammable (Pittosporum tobira) to extremely flammable (dead Cupressus sempervirens).This study provides useful information for reducing fire risk in WUIs in the study area.

Pine cones facilitate ignition of forest floor duff

The ignition and combustion of forest floor duff are poorly understood yet have been linked to soil heating and overstory tree mortality in many temperate coniferous forests. Research to date has focused on the characteristics of duff that facilitate ignition and spread, including fuel moisture, mineral content, and depth. Field observations suggest that the presence of pine cones on and within the forest floor might facilitate ignition of intermixed forest floor fuels. We investigated the effect of cone fuel additions on the ignition of underlying forest floor from fuels collected in long-unburned longleaf pine (Pinus palustris Mill.) forests in northern Florida, USA. Fuels were wetted to threshold gravimetric moisture contents to evaluate the relative effect on ignition. In stark contrast to fuel beds without cones, in which duff ignition only occurred in 17% of samples, those with cones added ignited the underlying duff 94% of the time. Flame heights were 40% taller and flaming duration was 47% longer in fuel beds with cones. Where present, pine cones act as vectors of ignition for forest floor fuels, and their role in fires deserves more attention to enhance our understanding of forest floor combustion.

Assessing the flammability of surface fuels beneath ornamental vegetation in wildland–urban interfaces in Provence (south-eastern France)

The objectives of this paper are to assess in laboratory conditions the flammability of undisturbed litter sampled beneath plants of seven species that are among those most frequently planted in hedges in Provence (south-eastern France). The variability in litter flammability recorded during burning experiments was partly explained by the proportions of the different litter components of each species. Phyllostachys sp. and Nerium oleander litters were the quickest to ignite whereas Prunus laurocerasus litter had the lowest bulk density and long time-to-ignition, but high flame-propagation. Photinia fraseri litter ignited frequently and had a high flame spread whereas Pittosporum tobira litter ignited the least frequently and for the shortest duration. Cupressus sempervirens litter had the highest bulk density and the longest flaming duration but the lowest flame propagation. Pyracantha coccinea litter was the slowest to ignite and flame propagation was low but lasted a long time. Co-inertia analysis identified species with the same flammability characteristics according to the composition of their litter. Hierarchical cluster analysis ranked the seven species in four distinct clusters from the most flammable (Photinia fraseri and Prunus laurocerasus) to the least flammable (Pittosporum tobira), the other species displaying two groups of intermediate flammability. These latter species should not be used in hedges planted in wildland–urban interfaces in south-eastern France.

Comparative Effects of the Fire Behaviours of Potassium Aluminium Sulphate and Potassium Sesquicarbonate on Flexible Polyether Foam

The effects of potassium aluminium sulphate (K2SO4·Al2SO4)3·24H2O) and potassium sesquicarbonate (K2CO3·2KHCO3·3/2 H2O) as flame retardants on fire properties of flexible polyether foam was studied. Potassium sesquicarbonate performed better at increasing the ignition time and the amount of char formed and both factors improved with flame retardant concentration. However, the afterglow time, flame duration, burn length and flame propagation rate decreased with increase in concentration. The flame propagation rates of foam samples with alum were higher than the corresponding rates with potassium sesquicarbonate. This could be attributed to the nature of their decomposition products at pyrolysing/flaming temperature. Thermogravimetric analyses showed that the flame retardants delayed the onset of degradation. The delay effect was higher with potassium sesquicarbonate (akanwu) than with potassium aluminium sulphate (alum). Again, the delay effect was affected by the flame retardant concentration.

Species composition and fire: non-additive mixture effects on ground fuel flammability

Diversity effects on many aspects of ecosystem function have been well documented. However, fire is an exception: fire experiments have mainly included single species, bulk litter, or vegetation, and, as such, the role of diversity as a determinant of flammability, a crucial aspect of ecosystem function, is poorly understood. This study is the first to experimentally test whether flammability characteristics of two-species mixtures are non-additive, i.e., differ from expected flammability based on the component species in monospecific fuel. In standardized fire experiments on ground fuels, including monospecific fuels and mixtures of five contrasting subarctic plant fuel types in a controlled laboratory environment, we measured flame speed, flame duration, and maximum temperature. Broadly half of the mixture combinations showed non-additive effects for these flammability indicators; these were mainly enhanced dominance effects for temporal dynamics – fire speed and duration. Fuel types with the more flammable value for a characteristic determined the rate of fire speed and duration of the whole mixture; in contrast, maximum temperature of the fire was determined by the biomass-weighted mean of the mixture. These results suggest that ecological invasions by highly flammable species may have effects on ground-fire dynamics well out of proportion to their biomass.

G060014 高硬度バイオマス燃料の燃焼挙動の観察

Recently, biomass attract much attention as renewable energy resource. Bio-coke, hereinafter called BIC, is one of the solid biomass fuel which is made from woody or herbaceous biomass through heating and compressing. BIC is expected to be an alternative of coal coke and high energy density solid fuel because it has high hardness and high density. In the present study, the effect of the molding condition of BIC, whose materials are green tea and cypress, on the combustion property is examined. The experimental results show that the fundamental combustion property is similar to result of TG/DTA curves of each material and, however, temperature, pressure and water content at the production of BIC affect the ignition delay, flaming duration and char combustion period. As the molding temperature increases, ignition delay increases and flaming duration decreases, and as the water content of material increases, the ignition delay increases. It is supposed that the effects are related to the density and porosity of BICs.

Fires enhance flammability inUlex parviflorus

Fires enhance flammability in<i>Ulex parviflorus</i>

Research on the Combustion and Emission Characteristics of Lean Burn CNG Engine

The study on combustion characteristics of different excess air ratios (λ) and ignition timings was conducted on a lean-burn spark-ignition CNG engine, and the corresponding emission characteristics was also analyzed. The results show that the curve of cylinder pressure moves towards TDC, and the CoVimep decreases with the advance of ignition timing. With the excess air ratio increasing, the CoVimep increases while the cylinder pressure decreases firstly, and then increases. The flame development duration increases with the ignition timing advanced, but the rapid flame duration decreases, the total combustion duration basically keep constant, and all of them increase with the increasement of excess air ratio. Best fuel economy was gotten at λ=1.2. With the excess air ratio increasing, the CO and NMHC emissions decrease, the NOx emission firstly reaches to a peak value, which is about 3000ppm at λ=1.2, and then decreases. Both of the THC and CH4 emissions have opposite trends to NOx emission. All the emissions mentioned above increases with the advance of ignition timing.

Laboratory characterization of firebrands involved in spot fires

Wildfires are considered the most important disturbance in the Mediterranean Basin, and some are propagated over long distances due to lift-off and ignition of firebrands. To improve our knowledge of firebrands involved in spotting fires, flammability characteristics of eight types of firebrands commonly generated by wildfires in Southern Europe were determined under laboratory conditions. All the firebrands tested showed 100% ignition frequency but with a wide range of time to ignition and flaming duration. Weight loss during combustion was exponentially related to time, and there was a decrease in the ratio of the weight at temperature T to the initial weight with increasing temperatures. In our experimental conditions, there was a significant effect of fuel moisture content on time to ignition, flaming duration, combustion and thermal decomposition. On the basis of the characteristics analysed, three firebrand groups have been identified in relation to spotting: heavy firebrands with ability to sustain flames, efficient for long-distance spotting (pine cones); light firebrands with high surface-to-volume ratio, efficient for short-distance spotting (leaves and thin barks); and light firebrands with low surface-to-volume ratio, efficient for short and, occasionally, long-distance spotting (all the other types of firebands).