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Title: BRE Centre for Fire Safety Engineering / BRE
Language: English
Description: The BRE Centre for Fire Safety Engineering is part of the Institute for Infrastructure and Environment, School of Engineering at the University of Edinburgh. The research fire centre exists to: support today's fire safety with multidisciplinary research; provide education in Fire Safety Engineering and Structural Fire Engineering; deliver fire safety consultancy services to industry and other consultancies; disseminate information about advances and research in fire safety engineering through courses, symposia and publications. A variety of research projects from detailed studies of fundamental combustion processes through to the application of fire safety engineering in practice is performed. Numerical modelling work as well as experimental research is carried out.
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Title: D2.2-1 3D-Modelling of fire behaviour and effects /
Language: English
Description: This work is carried out within the context of the European integrated project “FIRE PARADOX”, the aim of this particular work package is to obtain a full-physical three-dimensional model of forest fire behaviour. The proposed approach accounts for the main physical phenomena involved in a forest fire by solving the conservation equations of physics applied to a medium composed of solid phases (vegetation) and gas mixture (combustion gases and the ambient air). The model consists in coupling the main mechanisms of thermal degradation (drying, pyrolysis and combustion) and of transfer (convection, diffusion, radiation, turbulence, etc.) taking place during forest fire propagation [1]. This multiphase complete physical approach already exists in 2D approximation [2] and consists in solving the described model in a vertical plane defined by the direction of fire propagation. The 3D extension of the existing model will enable to render the 3D effects observed in real fires and to represent the real heterogeneous structure of the vegetation. The parallelized CFD code under development is currently at the stage of predicting turbulent gas flows (within and above a forest canopy) and has been validated on several benchmarks of natural, forced and mixed convection.
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Title: D2.2-2 How to account for the heterogeneity of vegetation on fire behaviour and effects modelling /
Language: English
Description: The main objective of the present study was to evaluate the magnitude of vegetation heterogeneity effects on radiative transfer in forest fires. Especially we wanted to determine which heterogeneity sizes were important to consider either fuel description or fire modelling. We first considered these effects at shoot level (variations within several tens of centimetres) to identify which parameters describing needles distribution in pine shoots cause a significant departure from the usual extinction coefficient ( ). A study based on a shoot modelling approach (Stenberg 1996; Stenberg et al. 2001; Smolander & Stenberg 2001; Cescatti & Zorer 2003; Smolander & Stenberg 2003) was used for a computation of the STAR parameter based on architecture measurements for Pinus halepensis. Then we considered the effects of heterogeneity in patchy Mediterranean shrub land or tree canopies (Pinus halepensis, Pinus pinaster) at the scale of a clump of plants (variations within several meters), using field measurements and detailed tree architecture models (Caraglio et al. 1996; Barczi et al. 1997; Caraglio et al. 2006). For this purpose, the methodology used for solar radiation was adapted to fire radiation. In particular we investigated the effects of heterogeneity size and cover fraction for different bulk densities, on the heating of vegetation by radiation from a flaming zone of assumed dimensions. The results were analysed in terms of appropriate scale for fuel description and physical modelling, and specific method for physical modelling.
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Title: D2.2-2 How to account for the heterogeneity of vegetation on fire behaviour and effects modelling /
Language: English
Description: Wildland fires spread through vegetation which is a medium that can be very heterogeneous at several scales (Campbell & Norman 1997). The smallest scale is at shoot level, when needles or leaves are clumped around the shoot. The second scale is at branch level, when shoots are aggregated around a branch. The third one is at tree or shrub level. It defines the contour of vegetation. The last scale is the one of the stand. Energy budget dynamics under forest canopies are strongly influenced by the effects of spatial variability within the canopy on radiative and turbulent transfers (Hardy et al. 2004). In the wildland fire context, we assume that both radiative and convective transfer, as well as the combustion process, may be affected by fuel heterogeneity. Physically-based models for fire propagation are able to use vegetation spatial patterns described at a fine level in the mesh of solid phase (Dupuy & Morvan 2005; Linn et al. 2002) and to study how spatial patterns affect propagation (Linn et al. 2005). However, mesh size in calculation does not always entail to consider all kinds of heterogeneity, especially in shoot aggregation and understorey description. Moreover, mesh refinement is maybe not an appropriate objective because of plant fractal geometry (De Reffye et al. 1991; Knyazikhin et al. 1998). In addition, describing vegetation at these levels can be very time consuming (Cohen et al. 2004). Hence we could wonder whether or not details in vegetation patterns affect significantly fire behaviour, at least through radiation transfer. Indeed, radiation transfer in fires is a quite short distance heating, directly affected by the transmission by vegetation itself. For this reason, it is likely to be affected on average by small scale heterogeneity. Like in solar radiation transfer, the computation of radiation transfer in theoretical fire models is based on turbid media approximation (Albini 1985; Grishin 1997; Linn 1997; Morvan & Dupuy 2001; Cruz et al. 2006; see also Reviews by Pastor et al. 2003 and Sullivan et al. 2003), that is valid for a distribution of small planar elements, with negligible area and thickness. We will consider the effects of heterogeneity at both a shoot level and a plant clump level on radiation transfer in section 2. The convective transfer is the transfer of heat between the vegetation and the gaseous phase that results from the flow of air or hot gases over solid elements of vegetation, when the two media (fluid or vegetation) have different temperatures. The basic process of heat exchange is conduction (i.e. a very small scale process), but it is usually modelled at a macroscopic scale through a convection heat transfer coefficient, which depends on the flow properties and on geometrical properties of vegetation elements (Reynolds number). Any spatial variation in vegetation properties may cause variations of the fluid flow and in turn on the convective heat transfer, because it may affect the flow directly (through drag forces) or the heat transfer coefficient (through Reynolds number). Studies of wind flow over plant canopies in the atmospheric boundary layer have already shown that the smallest details of vegetation distribution (i.e. shoot level for pine tree) are not relevant to explain observed wind and turbulent variables profiles (Shaw & Patton, 2003). Indeed computations of wind flow based on the solution of Navier-Stokes equations can render observed profiles using a cell mesh an order of magnitude greater than these details. Typically, for tree canopies of at least 10 m height, using cells of 2 m side is enough. We also verified this assertion using the HIGRAD/FIRETEC model for fire behaviour that can be used to compute wind flows (see Appendix) We did not investigate the effects of small scale heterogeneity on the convective heat transfer coefficient, although for example strong clumping of needles in pine shoot may change significantly the local heat transfer coefficient as compared to a random distribution of ‘isolated’ needles. Indeed Michaletz and Johnson (2006a) showed that the tree foliage of conifers changes the heat transfer coefficient with respect to the one of ‘isolated’ elements But only the finest elements of vegetation participate in the propagation of fire and are characterized by a short response time (order of 1s or less) to a change in the fluid temperature. We expect that the response time be at most one order of magnitude higher with clumped needles (lower heat transfer coefficient). This should not affect significantly the temperature evolution of the finest elements of vegetation. Michaletz and Johnson (2006b) reached a similar conclusion, investigating crown sorch of several conifers, for foliage. They showed in addition that the conclusion is no longer valid for vegetative buds. Hence the details of vegetation elements should be considered for the purpose of predicting fire effects on trees. Due to small scale vegetation heterogeneity (tens of centimetres) is unlikely to produce significant effects on the structure of the flow we rather focused on the effects of larger scales like the one of tree crowns (a few meters). Moreover we only considered the effects of large scale heterogeneity on the overall fire behaviour as predicted by the HIGRAD/FIRETEC fire model (section 3) (i.e. including radiative and convective heat transfer, as well as combustion processes). Testing of the separate effect on convective transfer is an ongoing work. But due to we assume that radiation is much more a short distance process in fires (confirmed in section 2), we expect that the observed effects were mainly related to the effects on the flow. We derived recommendations for both fire behaviour modelling and vegetation description, which are proposed in section 4.
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Title: D2.4-1 Simulations of wildfire behaviour: 2D results /
Language: English
Description: This work is carried out within the context of the European integrated project “FIRE PARADOX”, aiming to obtain a fully physical three-dimensional model of forest fire behaviour. The development of this 3D code constitutes an extension of the 2D fire behaviour model FIRESTAR developed during a previous European project (EVG1-CT-2001). In this preliminary task, some physical sub-models have been modified, such as the turbulence and the combustion modelling, to improve the capability of this tool to reproduce the main characteristics observed during the propagation of a surface fire through a solid fuel layer. After a short introduction and a brief presentation of the set of equations constituting the physical model, some numerical results obtained in 2D for a surface fire propagating through an homogeneous (grassland) and an heterogeneous (shrubland) fuel layer, are analysed and compared with experimental and empirical data from the literature.
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Title: Deliverable D2.3-6-45 Fire impact on trees and shrubs: final achievements /
Language: English
Description: A series of fire experiments were conducted in the laboratory in the frame of Activity WP2.3.3 of FIRE PARADOX, Fire impacts on trees, to better understand the physical mechanisms of fire effects on tree boles and to produce data for testing of fire behaviour models. This Deliverable presents a description of the different experimental methods and the results of the experiments conducted in this Activity. The document is divided in two main sections, taking into account the scale of the experimental setups: (i) Indoor laboratory fires carried out in a low speed wind tunnel, on the mutual influence between a surface fire and a tree trunk. Variations of rate of spread, flame height and flame angle in a fuel bed without a trunk and in a fuel bed with a trunk were analysed (Fig. I). Profiles of temperatures with time and qualitative results were also obtained. (ii) Outdoor laboratory fires conducted in a wind tunnel. In these experiments, the influence of the scale of the device was tested, temperature data obtained using different instruments were compared and the interaction between a fire front and a pine trunk (Fig.II) was analysed. The thermal conditions at the boundary of the tree trunk were characterized by means of thermocouples and infrared cameras (Fig. III). Besides, an approximation to estimate Heat Release Rate of a fuel bed in outdoor laboratory conditions, using custom-made thermopiles previously calibrated in a Mass Loss Calorimeter has been carried out (Fig. IV).
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Title: D2.4-2 Simulations of fire impact on tree foliage: 2D results /
Language: English
Description: The aim of the WP2.4 workpackage (activity 3) is to study numerically crown scorch and crown fire ignition as the effects of a fire line spreading through surface fuel under a tree canopy. Here we report a preliminary study performed with the FIRESTAR 2D model. The objective was to assess the usual assumptions made when one uses the Van Wagner criteria, based on plume theory, to estimate crown scorch or crown ignition. The Van Wagner criteria indeed are simple predictive models for crown scorch height or crown fire initiation occurrence. For this purpose we simulated the fire line by heat source put on the ground and mainly investigated the temperature field. As a first step we tested the sensitivity of the predictions to the mode of heat input and to the selected parameters of the k- turbulence model used in FIRESTAR. As a second step we ran computations of thermal plumes with no-wind and with no canopy, for first comparison to plume theory. The influence of crown existence to the temperature field above the heat source and, so way, to the crown scorch and fire ignition conditions, was then investigated. In the last part we show and discuss some results obtained in the presence of a wind.
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Title: D2.5-1 Definition of cases to be assessed. Schedule and format of data exchange between partners /
Language: English
Description: This document is the Deliverable D2.5-1 of the research project “FIRE PARADOX”, which is co-funded by the European Commission within the 6th Framework Program (2002–2006). The document is mainly related to Work Package 2.5 “Fire effects on buildings and people”. The contents of this document mainly concern the first 18 months of the project. This is the period for which detailed planning had been carried out when the project started. It is anticipated that new ideas and needs will arise during the implementation of the project; these will be incorporated into WP2.5 as the detailed planning of the project is refined according to the administration procedure of the project.
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Title: Deliverable D2.5-2 The effect of three-dimensionality on the building response to a forest fire /
Language: English
Description: In the practical applications of computational fluid dynamics in the prediction of the effects of forest fire on structures and people, the computational cost associated with the three dimensional simulations may sometimes restrain the usability of the simulations. Making the simulation two-dimensional reduces the computational cost by one or two orders of magnitude but may introduce additional errors to the results. In this work, the effects of the 2D assumption are studied by performing a series of simulations in both 3D and 2D, monitoring both convective and radioactive heat fluxes on the surfaces of the building surface, and reporting the difference between the 2D and 3D predictions of these heat fluxes. When doing the comparison between three- and two-dimensional simulations, special care must be taken to ensure that the two simulations actually represent the same fire scenario, which is the infinitely wide fire front. The performance of three-dimensional model at different boundary conditions and numerical parameters was first studied. The mirror boundaries on the sides of the fire front were found practical and valid for the reduction of computational cost. The grid sensitivity study performed in 2D showed that the independence of the grid resolution can be reached at 0.25 m. Due to the limited computational resources, only part of the final simulations were actually performed at this grid resolution. For the simulations of the crown fires, a coarser grid had to be used. From the viewpoint of radiation predictions, the 2D simulations were found to be better suited for the purpose than 3D simulations because in 2D, the smoothness of the radiation fields is much easier to achieve. At least 1000 angular directions were found necessary in 3D simulations. The validity of 2D simulations was studied by running a series of simulations in both 2D and 3D at different boundary conditions. The differences between the 2D and 3D simulations were studied by computing differences in convective and radioactive heat fluxes and by averaging them over the heat release rate ranges covered in the simulations. The conclusion was drawn based the cases where significant heat fluxes were found. The conclusion is that 2D simulations can be used for order-of-magnitude type of analysis, for which purpose they are well suited due to the small computing times. However, the differences seem to be too large for accurate predictions of the building and human response. Therefore, the critical simulations of the future analysis should be made in three dimensions.
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Title: D2.5-4-36 Fire safety analysis around targets using FDS: Final achievements - Transport of firebrands and attack on buildings /
Language: English
Description: Spotting is an important mechanism of wild land fire spread. Burning particles such as twigs and leaves lofted by the buoyant plume from forest fires can be carried by ambient winds anywhere from few meters up to even a kilometre from their source. Firebrands can then start new fires far from the original fire front. This makes it difficult to predict fire-fronts movements and can cause surprising and life threatening situations for fire fighters. Firebrands also pose a significant fire hazard at Wildland-Urban Interfaces (WUI). It is possible that firebrands are even the main fire hazard at WUI locations. This study addresses the effect of firebrand attack from a forest fire on an isolated building. The effect of the firebrand attack on a house is studied at Wildland Urban Interface (WUI) conditions. Penetrations of firebrands into the house under firebrand attack as well as firebrands landing distances are studied. Fire Dynamics Simulator (FDS) [19] is used to simulate WUI fire scenarios. The results show that firebrands of all studied sizes can reach the house even across distances as large as 50 meters. The overwhelming majority of the particles reaching the house land on the roof. Few firebrands can be observed hitting the facade of the building on the side facing the fire front. Only relatively small particles were found to penetrate into the house through small openings and vents. This is attributable to the fact that smaller particles tend to follow the surrounding gas flow whereas larger particles tend to fly in parabolic trajectories and thus most probably landing on the roof or in front of the house. Compared to earlier studies on firebrand propagation, somewhat shorter propagation distances were observed. Most of the earlier studies have used some form of simple plume model or otherwise simulated a steady state flow. Results in this study suggest that the turbulence of the plume has a significant effect on the motion of firebrands. The results also suggest that for larger firebrands the propagation occurs in two distinct phases: A firebrand is lifted to high altitude by a strong updraft and is then carried further by ambient winds. A firebrand model was added to the Fire Dynamics Simulator and was used to simulate a WUI fire. While considerable uncertainties remain in modelling the fire front and the firebrand material properties, it was shown that the model can be used to investigate firebrand attacks in WUI locations.
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Title: Deliverable 2.5-5-36 Criteria for building material ignition and for burn injuries in wildland fires: final achievements /
Language: English
Description: In fire modelling, an accurate prediction of the ignition of solid fuels requires the solution of solid- and gas-phase processes. Methods that decouple the solid from the gas phase would result in significant savings in computational cost. The work described herein presents a novel methodology for this decoupling. It is based on the observation that the time to ignition can be scaled with the square of the time integral of the incident heat flux. This relationship can be readily demonstrated for the classical solutions for time to ignition which consider constant incident heat fluxes. However, some fire applications, in particular situations of wild fires approaching the wildland-urban interface, present time-varying incident heat fluxes which render the classical solutions inaccurate. A new analytical solution for obtaining the time to ignition for ramping incident heat fluxes is presented. The proposed methodology completely decouples the solid and gas phases and is accurate in the prediction of ignition times. The methodology can be applied to both the new and classical analytical solutions. It was validated with tests carried out on PMMA and PA6. The results presented here will be useful for other teams developing forest fire models, especially the team at VTT which is working on the problem of the wildland-urban interface. The second part of the report is concerned with the development of a numerical model for the assessment of the influence of moisture migration in the severity of burn injuries affecting fire fighters. It was proven that this is an important factor affecting the severity of burn injuries. This information will constitute the basis for a research on the physiology of thermal skin burns, and will also help in the development of protective clothing for fire fighters.
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Title: D2.1-1 Methods for the experimental study and recommendations for the modelling of pyrolysis and combustion of forest fuels /
Language: English
Description: The understanding of fuel dependent behaviour and other parameters affecting the combustion of forest fuels is of great importance. Heat Release Rate (HRR) of a fuel is among the most important parameters for understanding combustion process, fire characteristics and propagation rates. It serves to define parameters such as flame geometry and temperature fields. Calorimetry tests on pine needles were conducted with sample holders designed to allow the porous nature of the fuel to be studied during the tests. The goal of this test series was to help characterize the pine needle beds with some detail. The use of sample holders that allow internal fuel bed flow seems to increase reliability of the test data. CO concentration profiles proved to be a good indicator of the dynamics of the combustion process. The ability for combustion air to flow into the porous bed allowed the measured CO concentrations to provide good data on internal fuel bed dynamics. The pine needle species studied behaved differently due to different packed densities and different surface-to-volume ratios. The results indicate that the transport processes inside the bed have a significant impact on the combustion process within the porous fuel bed. Further tests are necessary with smaller opening baskets and denser fuel beds to confirm the flow effects and the fuel bed effects, respectively. An important new step to study the role of kinetics will be the use of air with different oxygen concentrations. The HRR results calculated by means of oxygen consumption calorimetry were reinforced by the use of mass loss rate calorimetry. CO concentrations in the exhaust gases proved to be a good indicator of the dynamics of the combustion process. The transition between flaming combustion and smouldering embers was reflected in the measured CO responses. Again, the ability for combustion air to flow into the porous bed allowed the measured CO concentrations to provide good data on internal fuel bed dynamics. HRR, time to ignition and time to reach peak HRR indicated a strong dependence on flow conditions within the fuel bed. The pine needle species studied behaved differently due to different packed densities and different surface-to-volume ratios. Gas concentrations were also measured by means of Fourier Transform Infrared (FTIR) spectrometry. An open path FTIR technique was also developed and applied. The results are in agreement with other published results.
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Title: Deliverable 2.3-1 Fire behaviour in several fuel types: Methods and First results /
Language: English
Description: A series of fire experiments are being conducted in Activity WP2.3.1 of FIRE PARADOX, Wildfire behaviour, both in laboratory and in the field, to better understand the mechanisms of fire propagation and to produce data for testing of fire behaviour models. This Deliverable presents a description of the different experimental methods, as well as the first results of the experiments conducted in this Activity. The document is divided in three main sections, taking into account the scale of the devices: (i) Indoor laboratory fires carried out in a low speed wind tunnel, in beds of Pinus pinaster, P. halepensis and P. pinea needles. Variations of rate of spread, flame height and flame angle with wind velocity (Fig. I), as well as profiles of temperatures with time were analysed in these tests. (ii) Outdoor laboratory fires conducted in a wind tunnel in shrubland fuels, to study vertical propagation of fire. In these experiments, effects of fuel vertical discontinuity, absence or presence of litter layer, wind velocity and type of ignition source were tested (Fig. II). IR imaging analysis of fire transition was also accomplished (Fig. III). (iii) Field experimental fires conducted in kermes oak garrigue in South of France (Fig. IV), and in shrubland fuels in the Chaco Region, Argentina (Fig. V). In these burns, a fuel description was carried out. During the burns, meteorological conditions were monitored, and fire behaviour descriptors were obtained.
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Title: Deliverable 2.3-4 Fire behaviour in several fuel types: final achievements /
Language: English
Description: Fire experiments have been conducted in different surface fuels, both in laboratory and in the field. These experiments aim at understanding fire behaviour and producing data for testing of fire behaviour models. Indoor laboratory fires were carried out in three different pine needle fuel beds (Pinus pinaster, P. halepensis and P. pinea) in a low speed wind tunnel. Variations of rate of spread, flame height and flame angle with wind velocity, as well as profiles of temperatures with time, are analysed in these tests. Correlations between these variables are found to be close to earlier published correlations and the observed behaviour is interpreted as a result of a balance between wind forces and buoyant forces. Outdoor laboratory fires were carried out in a wind tunnel in a shrubland fuel, to study the vertical propagation of fire. Indeed it is important to determine which variables condition capability of a shrubland to sustain a high fire intensity burning the whole surface fuel layer. Fires were conducted with and with no pine dead needle fuel bed underneath the shrub layer and with and with no discontinuity between the needle layer and the shrub layer above. Under the wind conditions of these experiments (no wind and weak wind) fire does not propagate if there is no needle layer below the shrub layer. When there is a needle layer, the success of vertical propagation to the shrub layer was found to correlate with the maximum temperature measured in the lower part of the shrub layer. It is unclear however whether the temperature level determines the vertical propagation or is a consequence of this vertical propagation. Other variables, namely fuel discontinuity, wind or fuel moisture content, are not found to be explanatory of the vertical propagation in the statistical analysis. Four field experimental fires were conducted in 16 m diameter hexagonal plots selected in a uniform shrubland fuel type (Quercus coccifera garrigue) under 4-6 m/s wind speeds, in the South of France. In addition to rate of spread and fuel consumption, temperatures were measured within the plots at the top of the vegetation layer and radiant heat fluxes were measured outside the plots. Analysis of these data suggests that convective heating plays a dominant role in the propagation of these fires. Although two fires were conducted under low shrub moisture content and two under high shrub moisture content, the effect of fuel moisture on the rate of spread is found to be small with respect to the effect of fuel moisture on the heat of fuel ignition. Two hypothesis are proposed to explain this result. Two sets of six fires each in 30 x 30 m plots were conducted in two grassland fuel types in the Chaco region in Argentina. Fire spread about 30 % faster in the first grassland type, while wind speed was two times lower and fuel bulk density was two times higher. This effect is attributed to the fine fuel load, which was more than two times higher in the first grassland type. This result is an addition to the contradictory results on fuel load effect existing in the literature. It is also suggested that differences in plant architecture could explain the rate of spread variation.
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Title: Deliverable D2.3-6-45 Fire impact on trees and shrubs: final achievements /
Language: English
Description: A series of fire experiments were conducted in the laboratory in the frame of Activity WP2.3.3 of FIRE PARADOX, Fire impacts on trees, to better understand the physical mechanisms of fire effects on tree boles and to produce data for testing of fire behaviour models. This Deliverable presents a description of the different experimental methods and the results of the experiments conducted in this Activity.
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Title: D2.1-4 Measurements of thermal degradation, ignition and combustion on representative Boreal and Mediterranean fuels /
Language: English
Description: The work presented in this report is a part of the research effort done to improve the knowledge on the thermal degradation of forest fuels. The understanding of these processses is of vital importance for the development of physical fire behaviour models . Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) are thermal analysis techniques that provide information on the thermal behaviour of different fuel samples and these data may facilitate the better understanding of the mechanisms of ignitability and combustibility of forest fuels with different chemical composition. The thermal degradation of 10 forest species common in the Mediterranean region has been compared using TGA and DSC techniques. Almost all the tested species demonstrated similar pyrolitic behaviour, except Eucalyptus camaldulensis. Heat Release Rate (HRR) of a fuel is among the most important parameters for understanding combustion process, fire characteristics and propagation rates. It serves to define parameters such as flame geometry and temperature fields. In a previous work, different partners with different bench-scale equipments to measure HRR curves as well as concentrations of the different gaseous by-products of the fuel combustion put in common their expertise testing common samples. This common work and conclusions about experimental conditions to test forest fuel in bench-scale calorimeters was presented in a previous document (deliverable "D2.1-1 Methods for the experimental study combustion adapted to forest fuels and recommendations for modelling"). In this report some result obtained by a Mass Loss Calorimeter with an open-path FTIR spectroscopic system in Pinus pinea and Cistus laurifolius are presented to study the influence on the HRR, carbon monoxide and carbon dioxide curves of parameters like the fuel moisture content or the bulk density of the tested sample. Besides, a Flame Propagation Apparatus has been used to apply oxygen consumption calorimetry for HRR and a FTIR has been used to measure gas concentrations of combustion products in smoke. Results on several pine needles (analyzing flow and species influences) and boreal moss are presented. A Flame Propagation Apparatus (FPA) joined to a FTIR gas analyzer is used to continue previous studioes on pine needles in order to better understand the different regimes for the combustion dynamics of forest fuels. Also Boreal moss has been tested as a new fuel common in Northern Europe. The aim was to investigate the possible differences in behaviour between this fuel and pine needles.
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Title: Comportamiento del fuego en un pastizal del sitio ecológico ‘media loma’, región chaqueña occidental (Argentina) / Fire behaviour in grassland ecological site 'media loma', western Chaco region (Argentina)
Language: Spanish
Description: Fire behavior, considered a part of fire ecology, is together with fire prevention one of the two components of the ´fire triangle´ currently used as a basis for fire management and control. We assessed the fire behavior in a grassland located in the midland range ecological site in the Chaco region, northwestern Argentina. The site of the experiments was the ´La María´Experimental ranch, INTA Santiago del Estero Research Station, (28º 03’ S 64º 15’ E). Fire was applied in two study sites in 6 plots each. Fine fuel load, botanical composition, and fine fuel bulk density were estimated by sampling. Fire behavior was assessed by estimating forward rate of spread and flame length. These data were analysed using ANOVA with study site as independent variable. Correlation among variables was assessed using the Kendall’s ô correlation coefficient. Study sites presented a different botanical composition: plots were either dominated by Trichloris pluriflora (E.) Fournier, or by Pappophorum pappipherum (Lam.) Kuntze. Plant of these species possess different proportion of stems and leaves. These facts significantly affected fine fuel load, bulk density (p > F = 0,0001 in both cases) and the forward rate of spread (p > F = 0.0001). The latter was 27,62 m*min-1 in study site 1, where the first species dominated; and 21 m*.min-1 in study site 2, where the second dominated, respectively. Average flame length was 3,5 m, but reached 6 m when volatile shrubs ignited and participated in the propagation of fire. Correlations among forward rate of spread and fuel load with bulk density was positive and significant (p < 0,0001), but was not significant in the case of flame length. Fires were of high intensity and move fast and need blacklines or other indirect measures for control.
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