Effective heat of combustion for flaming combustion of conifers (original) (raw)
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Six species of wood were studied by combined thermogravimetric and differential thermal analysis (TG/DTA) so as to evaluate their combustion properties in terms of the amount of energy released, the initial temperature of ignition, and the cleanness of burning. Pinus monticola, Acer saccharum, Quercus rubra, Diospyrus spp., Tabebuia spp. and Guaiacum spp. were chosen to provide a wide range of hardness values and densities. Quercus rubra burned to the hottest temperature of the samples, and also left the least amount of ash behind. For Guaiacum spp. its burning temperature is in the middle of the peak temperatures for other woods – while its final amount of ash is considerably larger than in the other samples. There is no connection between the wood density and the parameters characterizing the burning process.
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A series of real scale fire experiments were performed to determine the mass and size distribution of firebrands generated from Korean Pine (pinus koraiensis) trees. The experiments were performed at the Building Research Institute (BRI) in Tsukuba, Japan. The tree height was fixed and tree moisture content was varied to examine the influence that this parameter has on the mass and size distribution of the firebrands that are produced, under ambient wind conditions. The firebrands were collected using an array of water filled pans. This ensured that firebrands would be quenched as soon as they made contact with the pans. The Korean Pine trees were also mounted on load cells during burning to determine the temporally resolved mass loss profiles. The mass loss data were used to calculate the mass loss rate and infer peak heat release rate (HRR). Results of this study are presented and compared to firebrand distribution and HRR of burning Douglas-Fir trees, a conifer tree species indig...
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Journal of Applied Fire Science, 1996
This paper presents the results of an experimental investigation into the flaming combustion characteristics of wood-based materials. The present work was primarily motivated by the fact that combustible solids, particularly cellulosic materials, often constitute the bulk of fuels in many building fires. In order to achieve this task a number of small-scale experiments on samples of different wood species were performed using a cone calorimeter. In all cases the effects of controlling factors, such as the irradiance level, moisture content and the orientation of the sample were carefully examined. It was found that the experimental data are quite sensitive to these factors. In particular, the effect of the moisture content on the heat of combustion and heat release rate was found to be quite significant. The results of the experiments were also used to develop some useful correlations.
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Fire spread across forest fuel is usually characterized by the rate of spread or the fireline intensity. The determination of the fireline intensity represents an essential aspect for understanding the behaviour of the fire and the involved combustion processes. The heat released during fire spread cannot be a-priori estimated from the fundamental properties of the fuel material and experiments need to be carried out to determine it. This paper presents a global characterization of horizontal fire spread in still air across fuel beds in terms of heat release, rate of spread, flame geometry and radiant and convective fractions. The influence of the fuel load on these main fire properties is investigated. A series of experiments was conducted using a Large Scale Heat Release apparatus. The fire tests were carried out on a combustion table located on a load cell. The fuel consisted in a 2 m long and 1 m wide bed of pine needles. The fireline intensity was accurately estimated by means of oxygen consumption calorimetry and some other methods to assess this quantity were also tested. Combustion efficiency and effective heat of combustion were discussed. The heat fluxes emitted during the fire spread were also investigated. In the studied configuration, radiation was the dominant heat transfer mechanism in the preheating zone; whereas some transfers combining
Imprensa da Universidade de Coimbra eBooks, 2022
The frequencies of wildfires in the Mediterranean climate regions (MCRs) have amplified due to the increased temperatures and drought periods resulting from climate change. Vast areas of forests are consumed by wildfires and certain species are threatened by extinction due to their high flammability and weak thermotolerance to climate change whereas, other species with high thermotolerance are exploited as silviculture measures in forest management strategies. Canopy and litter foliage are the first ignitable structures in a forest fire. In this context, the foliar flammability characteristics of two fire resilient Mediterranean forest species are tested and compared on a laboratory scale; Quercus suber L. (Q.s.L.) and Cupressus sempervirens L (C.s.L). Thermo gravimetric/thermo differential analysis (TGA/TDA) and low-to high-temperature analytical pyrolysis tests and gas chromatography-mass spectrometry (GC-MS) were conducted on live and dry foliar samples of Lebanese C.s.L and Algerian Q.s.L. Branch and cork samples of Q.s.L were also pyrolyzed (Py/GC-MS) for their volatile content. The hemicellulose/cellulose degradation temperatures of C.s.L. were in the order of 30 to 50°C more than those of Q.s.L. Lignin degradation started later in the Q.s.L. and took place at temperatures higher than those of C.s.L. (≥30°C), while the heat release rates (HRR) were greater for the latter than the former in both degradation phases. The pyrolysis tests showed higher volatile content of C.s.L compared to Q.s.L. The high thermotolerance characteristic of C.s.L may be referred to its high terpene content which was negligible in Q.s.L given the fact that it is a non-monoterpene emitter oak species with no terpene storage compartments. The use of C.s.L as a fire barrier could be justified given their thermotolerance characteristic. Q.s.L. fire resilience is justified for their bark characteristics however; their foliage fire resilience should be further experimented.
A comparative study of the combustion dynamics and flame properties of dead forest fuels
Imprensa da Universidade de Coimbra eBooks, 2022
The combustion properties of several dead Mediterranean forest fuels were investigated experimentally. Samples of straw, eucalyptus, shrubs, and Pinus Pinaster with the same load were placed in cylindrical containers of the same size and were ignited from the perimeter of the container's bottom. A pitot tube and a thermocouple are placed one meter above the fuel surface to measure the airflow induced by the flame and the flame temperature. The main combustion parameters (mass-loss rate, flame height and temperature, and the induced air velocity) seem to evolve according to the same trend regardless of the fuel type. They increase rapidly in the growth phase of the flame then they decrease over a relatively long period characterizing the decay phase. In the crossover period between these two burning phases, the flame is fully developed with a maximum height and burning rate. The time required for the burning rate to attain its maximum value seems to vary only slightly with the fuel type. The maximum flame height and burning rate are found to be the largest for shrubs and the lowest for straw. The flame temperature and airflow are found to depend on the position in the flame with maximum values near the continuous zone of the flame.