V. Papadogianni, A. Romeos, A. Giannadakis, K. Perrakis, T. Panidis
This research investigated potential fire hazards originating in hidden areas of pressurized sections of aircrafts. The objective was to establish a laboratory-scale flammability test method to predict the behavior of fire propagation under real fire conditions. A confined fire apparatus (CFA) was designed and constructed, and several tests were conducted to better understand the involved mechanisms and their consequences and to estimate flame spreading in hidden-zone fires. The experimental facility and flame-spreading results obtained for a typical material involved in hidden fires, specifically a ceiling panel, were presented and discussed. The experimental facility consisted of a narrow passage where a fire was initiated using a burner on a specimen exposed to a controlled heat flux. Experiments were conducted in the absence of forced airflow. Flame spreading was estimated through visual monitoring of fire development or temperature measurements at specific locations in the specimen. Both methods yielded similar results. The flame spread velocity in relation to the imposed heat flux allowed for the estimation of the critical heat flux for spreading q˙sp,cr″ and for ignition q˙ig,cr″; the corresponding temperatures, Ts,min and Tig; and the flame spread parameter Φ.
{"title":"Fire Ignition and Propagation in Hidden Zones of Aircrafts: A Novel Confined Fire Apparatus (CFA) for Flame Spreading Investigation","authors":"V. Papadogianni, A. Romeos, A. Giannadakis, K. Perrakis, T. Panidis","doi":"10.3390/fire6080292","DOIUrl":"https://doi.org/10.3390/fire6080292","url":null,"abstract":"This research investigated potential fire hazards originating in hidden areas of pressurized sections of aircrafts. The objective was to establish a laboratory-scale flammability test method to predict the behavior of fire propagation under real fire conditions. A confined fire apparatus (CFA) was designed and constructed, and several tests were conducted to better understand the involved mechanisms and their consequences and to estimate flame spreading in hidden-zone fires. The experimental facility and flame-spreading results obtained for a typical material involved in hidden fires, specifically a ceiling panel, were presented and discussed. The experimental facility consisted of a narrow passage where a fire was initiated using a burner on a specimen exposed to a controlled heat flux. Experiments were conducted in the absence of forced airflow. Flame spreading was estimated through visual monitoring of fire development or temperature measurements at specific locations in the specimen. Both methods yielded similar results. The flame spread velocity in relation to the imposed heat flux allowed for the estimation of the critical heat flux for spreading q˙sp,cr″ and for ignition q˙ig,cr″; the corresponding temperatures, Ts,min and Tig; and the flame spread parameter Φ.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42409684","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The recent expansion of logistics capacities entails the installation of chemical warehouses, which operations increase the occurrence of compartment fires involving flammable dangerous substances. The aim of this research was to compare and analyze the fire behavior of beams made of different structural materials but with the same load capacity. It is assumed that wooden beams, which are less commonly used in industrial facilities, may have a similar or even better load-bearing capacity in case of a fire than the generally used steel beams. The authors—based on the relevant EU standards—performed load capacity calculations of three beams prepared from different materials under the influence of fire and analyzed the changes in the material properties. Then, they examined the possibility of reinforcing the beams with carbon fiber lamellae and proposed additional fire protection requirements. The test results not only proved the different degrees of fire resistance of various building materials in the event of a fire and after their reinforcement but also suggested the application of special technical, prevention and response measures for the safe storage of dangerous substances. The study outputs enable warehouse designers, operators and safety experts to ensure a higher fire safety level for chemical warehouses.
{"title":"Examination of the Fire Resistance of Construction Materials from Beams in Chemical Warehouses Dealing with Flammable Dangerous Substances","authors":"L. Kátai-Urbán, Zsolt Cimer, É. Lublóy","doi":"10.3390/fire6080293","DOIUrl":"https://doi.org/10.3390/fire6080293","url":null,"abstract":"The recent expansion of logistics capacities entails the installation of chemical warehouses, which operations increase the occurrence of compartment fires involving flammable dangerous substances. The aim of this research was to compare and analyze the fire behavior of beams made of different structural materials but with the same load capacity. It is assumed that wooden beams, which are less commonly used in industrial facilities, may have a similar or even better load-bearing capacity in case of a fire than the generally used steel beams. The authors—based on the relevant EU standards—performed load capacity calculations of three beams prepared from different materials under the influence of fire and analyzed the changes in the material properties. Then, they examined the possibility of reinforcing the beams with carbon fiber lamellae and proposed additional fire protection requirements. The test results not only proved the different degrees of fire resistance of various building materials in the event of a fire and after their reinforcement but also suggested the application of special technical, prevention and response measures for the safe storage of dangerous substances. The study outputs enable warehouse designers, operators and safety experts to ensure a higher fire safety level for chemical warehouses.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-07-31","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"44076896","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Y. Zou, M. Sadeghi, Yaling Liu, Alexandra Puchko, Son Le, Yang Chen, N. Andela, P. Gentine
Modeling the spread of wildland fires is essential for assessing and managing fire risks. However, this task remains challenging due to the partially stochastic nature of fire behavior and the limited availability of observational data with high spatial and temporal resolutions. Herein, we propose an attention-based deep learning modeling approach that can be used to learn the complex behaviors of wildfires across different fire-prone regions. We integrate optimized spatial and channel attention modules with a convolutional neural network (CNN) modeling architecture and train the attention-based fire spread models using a recently derived fire-tracking satellite observational dataset in conjunction with corresponding fuel, terrain, and weather conditions. The evaluation results and their comparison with benchmark models, such as a deeper and more complex autoencoder model and the semi-empirical FARSITE fire behavior model, demonstrate the effectiveness of the attention-based models. These new data-driven fire spread models exhibit promising modeling performances in both the next-step prediction (i.e., predicting fire progression from one timestep earlier) and recursive prediction (i.e., recursively predicting final fire perimeters from initial ignition points) of observed large wildfires in California, and they provide a foundation for further practical applications including short-term active fire spread prediction and long-term fire risk assessment.
{"title":"Attention-Based Wildland Fire Spread Modeling Using Fire-Tracking Satellite Observations","authors":"Y. Zou, M. Sadeghi, Yaling Liu, Alexandra Puchko, Son Le, Yang Chen, N. Andela, P. Gentine","doi":"10.3390/fire6080289","DOIUrl":"https://doi.org/10.3390/fire6080289","url":null,"abstract":"Modeling the spread of wildland fires is essential for assessing and managing fire risks. However, this task remains challenging due to the partially stochastic nature of fire behavior and the limited availability of observational data with high spatial and temporal resolutions. Herein, we propose an attention-based deep learning modeling approach that can be used to learn the complex behaviors of wildfires across different fire-prone regions. We integrate optimized spatial and channel attention modules with a convolutional neural network (CNN) modeling architecture and train the attention-based fire spread models using a recently derived fire-tracking satellite observational dataset in conjunction with corresponding fuel, terrain, and weather conditions. The evaluation results and their comparison with benchmark models, such as a deeper and more complex autoencoder model and the semi-empirical FARSITE fire behavior model, demonstrate the effectiveness of the attention-based models. These new data-driven fire spread models exhibit promising modeling performances in both the next-step prediction (i.e., predicting fire progression from one timestep earlier) and recursive prediction (i.e., recursively predicting final fire perimeters from initial ignition points) of observed large wildfires in California, and they provide a foundation for further practical applications including short-term active fire spread prediction and long-term fire risk assessment.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42980620","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Although wildfires are a common disturbance factor to the environment, some of them can cause significant environmental and socioeconomic losses, affecting ecosystems and people worldwide. The wildfire identification and assessment of their effects on damaged forest areas is of great importance for provision of effective actions on their management and preservation. Forest regrowth after a fire is a continuously evolving and dynamic process, and the accuracy assessment of different remote sensing indices for its evaluation is a complicated task. The implementation of this task cannot rely on the standard procedures. Therefore, we suggested a method involving delineation of dynamic boundaries between conditional categories within burnt forest areas by application of spectral reflectance characteristics (SRC). This study compared the performance of firmly established for fire monitoring differenced vegetation indices—Normalized Difference Vegetation Index (dNDVI) and Normalized Burn Ratio (dNBR) and tested the capabilities of tasseled cap-derived differenced Disturbance Index (dDI) for post-fire monitoring purposes in different forest environments (Boreal Mountain Forest (BMF), Mediterranean Mountain Forest (MMF), Mediterranean Hill Forest (MHF)). The accuracy assessment of the tree indices was performed using Very High Resolution (VHR) aerial and satellite data. The results show that dDI has an optimal performance in monitoring post-fire disturbances in more difficult-to-be-differentiated classes, whereas, for post-fire regrowth, the more appropriate is dNDVI. In the first case, dDI has an overall accuracy of 50%, whereas the accuracy of dNBR and dNDVI is barely 35% and 36%. Moreover, dDI shows better performance in 16 accuracy metrics (from 17). In the second case, dNDVI has an overall accuracy of 59%, whereas those of dNBR and dDI are 55% and 52%, and the accuracy metrics in which dNDVI shows better performance than the other two indices are 11 (from 13). Generally, the studied indices showed higher accuracy in assessment of post-fire disturbance rather than of the post-fire forest regrowth, implicitly at test areas—BMF and MMF, and contrary opposite result in the accuracy at MHF. This indicates the relation of the indices’ accuracy to the heterogeneity of the environment.
{"title":"Assessment of Spectral Vegetation Indices Performance for Post-Fire Monitoring of Different Forest Environments","authors":"Daniela Avetisyan, N. Stankova, Zlatomir Dimitrov","doi":"10.3390/fire6080290","DOIUrl":"https://doi.org/10.3390/fire6080290","url":null,"abstract":"Although wildfires are a common disturbance factor to the environment, some of them can cause significant environmental and socioeconomic losses, affecting ecosystems and people worldwide. The wildfire identification and assessment of their effects on damaged forest areas is of great importance for provision of effective actions on their management and preservation. Forest regrowth after a fire is a continuously evolving and dynamic process, and the accuracy assessment of different remote sensing indices for its evaluation is a complicated task. The implementation of this task cannot rely on the standard procedures. Therefore, we suggested a method involving delineation of dynamic boundaries between conditional categories within burnt forest areas by application of spectral reflectance characteristics (SRC). This study compared the performance of firmly established for fire monitoring differenced vegetation indices—Normalized Difference Vegetation Index (dNDVI) and Normalized Burn Ratio (dNBR) and tested the capabilities of tasseled cap-derived differenced Disturbance Index (dDI) for post-fire monitoring purposes in different forest environments (Boreal Mountain Forest (BMF), Mediterranean Mountain Forest (MMF), Mediterranean Hill Forest (MHF)). The accuracy assessment of the tree indices was performed using Very High Resolution (VHR) aerial and satellite data. The results show that dDI has an optimal performance in monitoring post-fire disturbances in more difficult-to-be-differentiated classes, whereas, for post-fire regrowth, the more appropriate is dNDVI. In the first case, dDI has an overall accuracy of 50%, whereas the accuracy of dNBR and dNDVI is barely 35% and 36%. Moreover, dDI shows better performance in 16 accuracy metrics (from 17). In the second case, dNDVI has an overall accuracy of 59%, whereas those of dNBR and dDI are 55% and 52%, and the accuracy metrics in which dNDVI shows better performance than the other two indices are 11 (from 13). Generally, the studied indices showed higher accuracy in assessment of post-fire disturbance rather than of the post-fire forest regrowth, implicitly at test areas—BMF and MMF, and contrary opposite result in the accuracy at MHF. This indicates the relation of the indices’ accuracy to the heterogeneity of the environment.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47169948","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
A. Palma, F. Gallucci, S. Papandrea, M. Carnevale, E. Paris, B. Vincenti, M. Salerno, Valerio Di Stefano, A. Proto
Agro-industrial activities generate a great amount of bioproducts as biomass residues containing energy and with potentially useful applications in the thermochemical conversion process. The management of this feedstock as uncontrolled combustion (“open burning”) can often be a problem within the supply chain for disposal practices, both in environmental and economic aspects. The residual matrices from agroforestry biomass processing can be treated to increase their energy levels and economic value. A widespread practice for sustainable disposal is the production of pellets from residual biomass, such as pruning. The aim of this study is to explore the combustion of pellets obtained from olive and citrus pruning, and their emissions into the atmosphere. This study confirms the possibility of using waste biomass to obtain a high-energy biofuel that is usable in a controlled combustion system and to monitor the process and its related emissions (CO, CO2, NOx, SO2, PM). Three different pellets (olive pellet, citrus pellet and a pellet obtained from a mix of olive and citrus) were characterized to determine their physicochemical properties and burned in an 80 kWth boiler equipped with multicyclone filter bags as an abatement system to evaluate relative emission. The characterization results show that citrus pellet has a higher ash content, moisture content and lower energy value than mixtures of olive pellet. The emission results suggest that, during combustion, higher emissions of CO and SO2 were monitored from mixtures of citrus pellet compared to burning only olive pellet.
{"title":"Experimental Study of the Combustion of and Emissions from Olive and Citrus Pellets in a Small Boiler","authors":"A. Palma, F. Gallucci, S. Papandrea, M. Carnevale, E. Paris, B. Vincenti, M. Salerno, Valerio Di Stefano, A. Proto","doi":"10.3390/fire6080288","DOIUrl":"https://doi.org/10.3390/fire6080288","url":null,"abstract":"Agro-industrial activities generate a great amount of bioproducts as biomass residues containing energy and with potentially useful applications in the thermochemical conversion process. The management of this feedstock as uncontrolled combustion (“open burning”) can often be a problem within the supply chain for disposal practices, both in environmental and economic aspects. The residual matrices from agroforestry biomass processing can be treated to increase their energy levels and economic value. A widespread practice for sustainable disposal is the production of pellets from residual biomass, such as pruning. The aim of this study is to explore the combustion of pellets obtained from olive and citrus pruning, and their emissions into the atmosphere. This study confirms the possibility of using waste biomass to obtain a high-energy biofuel that is usable in a controlled combustion system and to monitor the process and its related emissions (CO, CO2, NOx, SO2, PM). Three different pellets (olive pellet, citrus pellet and a pellet obtained from a mix of olive and citrus) were characterized to determine their physicochemical properties and burned in an 80 kWth boiler equipped with multicyclone filter bags as an abatement system to evaluate relative emission. The characterization results show that citrus pellet has a higher ash content, moisture content and lower energy value than mixtures of olive pellet. The emission results suggest that, during combustion, higher emissions of CO and SO2 were monitored from mixtures of citrus pellet compared to burning only olive pellet.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-07-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48925341","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Ye Chen, Chenxi Zhao, Qiurui Huang, Songyang Li, Jiahui Huang, Xiaomin Ni, Jian Wang
In aviation fire extinguishing systems, the extinguishing agent is stored in a bottle, which is pressurized by nitrogen. When fire occurs, the agent is discharged via pipe and nozzle to the target compartment. The geometry of the pipe has a significant impact on the discharge process, and merits study. In this study of the discharge process of halon1301 using pipes of different diameters, the pressure distribution was significantly influenced by varying pipe diameter. Contributions to pressure drops through the valve/pipe/nozzle were approximately 2%, 8%, and 90%, respectively, when the pipe diameter was larger than the nozzle diameter. The contribution through the pipe increased, and the contribution through the nozzle decreased, as the pipe diameter became smaller. When the pipe diameter was decreased to the nozzle diameter, pressure drops through the valve/pipe/nozzle were 10%, 45%, and 45%, respectively; there was an increased pressure drop through the pipe. Distinctions in pressure distribution led to temperature differences; when there were more pressure drops through the nozzle, the temperature in the pipe was lower.
{"title":"Impact of Pipe Diameter on the Discharge Process of Halon1301 in a Fire Extinguishing System with Horizontal Straight Pipe","authors":"Ye Chen, Chenxi Zhao, Qiurui Huang, Songyang Li, Jiahui Huang, Xiaomin Ni, Jian Wang","doi":"10.3390/fire6080287","DOIUrl":"https://doi.org/10.3390/fire6080287","url":null,"abstract":"In aviation fire extinguishing systems, the extinguishing agent is stored in a bottle, which is pressurized by nitrogen. When fire occurs, the agent is discharged via pipe and nozzle to the target compartment. The geometry of the pipe has a significant impact on the discharge process, and merits study. In this study of the discharge process of halon1301 using pipes of different diameters, the pressure distribution was significantly influenced by varying pipe diameter. Contributions to pressure drops through the valve/pipe/nozzle were approximately 2%, 8%, and 90%, respectively, when the pipe diameter was larger than the nozzle diameter. The contribution through the pipe increased, and the contribution through the nozzle decreased, as the pipe diameter became smaller. When the pipe diameter was decreased to the nozzle diameter, pressure drops through the valve/pipe/nozzle were 10%, 45%, and 45%, respectively; there was an increased pressure drop through the pipe. Distinctions in pressure distribution led to temperature differences; when there were more pressure drops through the nozzle, the temperature in the pipe was lower.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43053737","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Understanding how fire severity affects resprouting plants during post-fire regeneration is key to anticipating Mediterranean vegetation vulnerability in a context of increasingly large fires with high intensity and severity due to climate change. Here, we monitored the water status, leaf gas exchange, and plant growth in holm oaks (Quercus ilex) of central Spain burned with different fire severity throughout the first post-fire year. The Q. ilex burned with high severity (HB+) showed higher water potential and shoot growth than those burned with low severity (LB+) or unburned (B−), especially during spring and summer. In summer, resprouting HB+ and LB+ plants exhibited higher carbon assimilation than unburned ones. Moreover, we also found that plants with higher water availability and growth, i.e., HB+ individuals, had higher specific leaf area and lower water use efficiency. Overall, our study shows that holm oak forests exhibit high plasticity to fire and that Q. ilex burned with high severity have a faster short-term regeneration than those burned with low severity. However, this rapid regeneration is based on a less conservative water-use strategy, which could jeopardize their populations in case of extreme drought events increasingly common in the current context of climate change.
{"title":"Burn Severity Effect on the Short-Term Functional Response of Quercus ilex after Fire","authors":"A. Parra, M. B. Hinojosa","doi":"10.3390/fire6080286","DOIUrl":"https://doi.org/10.3390/fire6080286","url":null,"abstract":"Understanding how fire severity affects resprouting plants during post-fire regeneration is key to anticipating Mediterranean vegetation vulnerability in a context of increasingly large fires with high intensity and severity due to climate change. Here, we monitored the water status, leaf gas exchange, and plant growth in holm oaks (Quercus ilex) of central Spain burned with different fire severity throughout the first post-fire year. The Q. ilex burned with high severity (HB+) showed higher water potential and shoot growth than those burned with low severity (LB+) or unburned (B−), especially during spring and summer. In summer, resprouting HB+ and LB+ plants exhibited higher carbon assimilation than unburned ones. Moreover, we also found that plants with higher water availability and growth, i.e., HB+ individuals, had higher specific leaf area and lower water use efficiency. Overall, our study shows that holm oak forests exhibit high plasticity to fire and that Q. ilex burned with high severity have a faster short-term regeneration than those burned with low severity. However, this rapid regeneration is based on a less conservative water-use strategy, which could jeopardize their populations in case of extreme drought events increasingly common in the current context of climate change.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-07-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49540813","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The joint American–Russian Space Experiment Flame Design (Adamant) was implemented on the International Space Station (ISS) in the period from 2019 to 2022. The objectives of the experiment were to study the radiative extinction of spherical diffusion flames (SDF) around a porous burner (PB) under microgravity conditions, as well as the mechanisms of control of soot formation in the SDF. The objects of the study were the normal and inverse SDFs of gaseous ethylene in an oxygen atmosphere with nitrogen dilution at room temperature and pressures ranging from 0.5 to 2 atm. The paper presents the results of transient 1D and 2D calculations of 24 normal and 13 inverse SDFs with and without radiative extinction. The 1D calculations revealed some generalities in the evolution of SDFs with different values of the stoichiometric mixture fraction. The unambiguous dependences of the ratio of flame radius to fluid mass flow rate through the PB on the stoichiometric mixture fraction were shown to exist for normal and inverse SDFs. These dependences allowed important conclusions to be made on the comparative flame growth rates, flame lifetime, and flame radius at extinction for normal and inverse SDFs. The 2D calculations were performed for a better understanding of the various observed non-1D effects like flame asymmetry with respect to the center of the PB, flame quenching near the gas supply tube, asymmetrical flame luminosity, etc. The local mass flow rate of fluid through the PB was shown to be nonuniform with the maximum flow rate attained in the PB hemisphere with the attached fluid supply tube, which could be a reason for the flame asymmetry observed in the space experiment. The evolution of 2D ethylene SDFs at zero gravity was shown to be oscillatory with slow alterations in flame shape and temperature caused by the incepience of torroidal vortices in the surrounding gas. Introduction of the directional microgravity, on the level of 0.01g , led to the complete suppression of flame oscillations.
{"title":"Spherical Diffusion Flames of Ethylene in Microgravity: Multidimensional Effects","authors":"S. Frolov, V. Ivanov, F. Frolov, I. Semenov","doi":"10.3390/fire6080285","DOIUrl":"https://doi.org/10.3390/fire6080285","url":null,"abstract":"The joint American–Russian Space Experiment Flame Design (Adamant) was implemented on the International Space Station (ISS) in the period from 2019 to 2022. The objectives of the experiment were to study the radiative extinction of spherical diffusion flames (SDF) around a porous burner (PB) under microgravity conditions, as well as the mechanisms of control of soot formation in the SDF. The objects of the study were the normal and inverse SDFs of gaseous ethylene in an oxygen atmosphere with nitrogen dilution at room temperature and pressures ranging from 0.5 to 2 atm. The paper presents the results of transient 1D and 2D calculations of 24 normal and 13 inverse SDFs with and without radiative extinction. The 1D calculations revealed some generalities in the evolution of SDFs with different values of the stoichiometric mixture fraction. The unambiguous dependences of the ratio of flame radius to fluid mass flow rate through the PB on the stoichiometric mixture fraction were shown to exist for normal and inverse SDFs. These dependences allowed important conclusions to be made on the comparative flame growth rates, flame lifetime, and flame radius at extinction for normal and inverse SDFs. The 2D calculations were performed for a better understanding of the various observed non-1D effects like flame asymmetry with respect to the center of the PB, flame quenching near the gas supply tube, asymmetrical flame luminosity, etc. The local mass flow rate of fluid through the PB was shown to be nonuniform with the maximum flow rate attained in the PB hemisphere with the attached fluid supply tube, which could be a reason for the flame asymmetry observed in the space experiment. The evolution of 2D ethylene SDFs at zero gravity was shown to be oscillatory with slow alterations in flame shape and temperature caused by the incepience of torroidal vortices in the surrounding gas. Introduction of the directional microgravity, on the level of 0.01g , led to the complete suppression of flame oscillations.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42534434","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Á. Fajardo-Cantos, D. Moya, M. Lucas‐Borja, P. Plaza‐Álvarez, E. Peña‐Molina, J. González‐Romero, Jorge de las Heras-Ibañez
Worsening climate change and increasing temperatures generate more sever and extended wildfires, raising concerns about ecosystem services. Prescribed burns (PB) are used to reduce forest fuel loads. Improving knowledge regarding the vegetation response after PB is essential for generating common points for monitoring ecological burning effects and generating a protocol or practice guide. We compared the PB seasonality of low-intensity (spring, summer, and autumn) and unburned areas in a total of 12 plots in Pinus nigra Arnold ssp. salzmannii Mediterranean forest. Our vegetation analysis was short term (one year after each PB). We analyzed vegetation coverage, α-diversity (Pielou, Simpson, and Shannon’s index), life forms, and fire-adapted traits using the Canfield transect method, followed by statistical analyses such as non-metric multidimensional scaling (NMDS) and two-way ANOVA. α-diversity was significantly decreased (>55% of dissimilarity) in the burned plots during each season, with the lowest values after summer PB (69% of dissimilarity) when comparing the burned and unburned plots. There was a significant increase in hemicryptophytes (15−20%) and geophyte coverage (from 6% to 14%, or from 4% to 8% in certain cases) in the burned plots after PB seasonality; however, the phanerophytes were reduced (from 13% to 5%). Resprouters were more dominant after PB (an increase of 15–20%), which indicates that resprouters have a faster recovery and generate a fuel load quickly for highly flammable species such as Bromus after low-intensity burning. This suggests that low-intensity prescribed burning may not be the best methodology for these resprouting species. This study helps to understand how burning in the early season can affect inflammable vegetation and the change in fuel that is available in semi-arid landscapes. This is key to achieving the basis for the development of a standardized system that allows for the efficient management of forest services in order to reduce wildfire risks. One objective of this line of research is to observe the effects of recurrent burning in different seasons on vegetation, as well as plant−soil interaction using the microbial and enzyme soil activity.
{"title":"Short-Term Effects of Prescribed Burn Seasonality on the Understory in a Pinus nigra Arnold subsp. salzmannii (Dunal) Franco Mediterranean Forest","authors":"Á. Fajardo-Cantos, D. Moya, M. Lucas‐Borja, P. Plaza‐Álvarez, E. Peña‐Molina, J. González‐Romero, Jorge de las Heras-Ibañez","doi":"10.3390/fire6080283","DOIUrl":"https://doi.org/10.3390/fire6080283","url":null,"abstract":"Worsening climate change and increasing temperatures generate more sever and extended wildfires, raising concerns about ecosystem services. Prescribed burns (PB) are used to reduce forest fuel loads. Improving knowledge regarding the vegetation response after PB is essential for generating common points for monitoring ecological burning effects and generating a protocol or practice guide. We compared the PB seasonality of low-intensity (spring, summer, and autumn) and unburned areas in a total of 12 plots in Pinus nigra Arnold ssp. salzmannii Mediterranean forest. Our vegetation analysis was short term (one year after each PB). We analyzed vegetation coverage, α-diversity (Pielou, Simpson, and Shannon’s index), life forms, and fire-adapted traits using the Canfield transect method, followed by statistical analyses such as non-metric multidimensional scaling (NMDS) and two-way ANOVA. α-diversity was significantly decreased (>55% of dissimilarity) in the burned plots during each season, with the lowest values after summer PB (69% of dissimilarity) when comparing the burned and unburned plots. There was a significant increase in hemicryptophytes (15−20%) and geophyte coverage (from 6% to 14%, or from 4% to 8% in certain cases) in the burned plots after PB seasonality; however, the phanerophytes were reduced (from 13% to 5%). Resprouters were more dominant after PB (an increase of 15–20%), which indicates that resprouters have a faster recovery and generate a fuel load quickly for highly flammable species such as Bromus after low-intensity burning. This suggests that low-intensity prescribed burning may not be the best methodology for these resprouting species. This study helps to understand how burning in the early season can affect inflammable vegetation and the change in fuel that is available in semi-arid landscapes. This is key to achieving the basis for the development of a standardized system that allows for the efficient management of forest services in order to reduce wildfire risks. One objective of this line of research is to observe the effects of recurrent burning in different seasons on vegetation, as well as plant−soil interaction using the microbial and enzyme soil activity.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48023335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
C. Ding, Shuangyang Ma, Zijian Yan, Lingfeng He, Yuyao Li, Tingyong Fang, Yan Jiao
The spill fires caused by liquid fuel leaks greatly threaten the safety of fuel transportation and storage. In this work, the effect of fuel temperature on the spread characteristics of flowing flames was investigated through n-butanol spilling fire experiments. The spill fire spread can be divided into three stages at different temperatures and leakage rates (I) full spread, (II) gradually extinguished spread, and (III) unable to spread. The oscillation of the flame is related to the fuel thickness and the discharge rate. As the discharge rate or temperature increases, the spread mode changes from pulsation to uniform. With an increase in temperature, the surface flow of the flame is reduced, leading to a decrease in both the preheating time and pulsation amplitude. However, the rate of liquid surface detachment from the flame increases with increasing temperature. The view factor of flame spread can be calculated by the solid flame model, and the flame influences the heat radiation spread state with stable phases or peaks. The research findings presented in this paper hold significant implications for the development of fire safety regulations pertaining to fuel leakage fires.
{"title":"Experimental Study on the Effect of Sub-Flash Point Fuel Temperature on the Spread Characteristics of Spill Fire","authors":"C. Ding, Shuangyang Ma, Zijian Yan, Lingfeng He, Yuyao Li, Tingyong Fang, Yan Jiao","doi":"10.3390/fire6080284","DOIUrl":"https://doi.org/10.3390/fire6080284","url":null,"abstract":"The spill fires caused by liquid fuel leaks greatly threaten the safety of fuel transportation and storage. In this work, the effect of fuel temperature on the spread characteristics of flowing flames was investigated through n-butanol spilling fire experiments. The spill fire spread can be divided into three stages at different temperatures and leakage rates (I) full spread, (II) gradually extinguished spread, and (III) unable to spread. The oscillation of the flame is related to the fuel thickness and the discharge rate. As the discharge rate or temperature increases, the spread mode changes from pulsation to uniform. With an increase in temperature, the surface flow of the flame is reduced, leading to a decrease in both the preheating time and pulsation amplitude. However, the rate of liquid surface detachment from the flame increases with increasing temperature. The view factor of flame spread can be calculated by the solid flame model, and the flame influences the heat radiation spread state with stable phases or peaks. The research findings presented in this paper hold significant implications for the development of fire safety regulations pertaining to fuel leakage fires.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-07-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42491895","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"农林科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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