N. Smirnov, V. Nikitin, E. Mikhalchenko, L. Stamov
This paper presents the results of numerical simulation of a model combustion chamber of a pulse detonation engine using the authors’ developed software package. The main goal of the present study is to numerically investigate the effects of cyclic operation of pulse detonating chambers, as the former studies have been limited to simulating one cycle. To achieve this goal, a new mathematical model for heavy gas was applied simulating condensed fuel phase, which made it possible to accelerate computations and simulate multi-cycle operation of the device. Distributions of such characteristics as temperature, pressure, velocity, concentrations of reagents, intensity of reactions, and thrust force are obtained. A two-stage kinetic model of propellant combustion is proposed. Attention is paid to the main stages of PDE operation: filling of the chamber with reagents, ignition and transition to detonation, products exhaust, purification, and cooling the chamber with a neutral gas. The simulation of the working cycle with the shortest period for the specified system parameters was carried out, the execution time of each stage was obtained, and an assessment was carried out to minimize the main stages of the work cycle. Numerical results demonstrated that the characteristics of the engine cycle are stabilized already in the second cycle: the thrust in the first cycle differs from the thrust in the second by 5%, in the third from the second by 1%. Moreover, details of thrust dynamics in the second and third cycles were studied.
{"title":"Modeling a Combustion Chamber of a Pulse Detonation Engine","authors":"N. Smirnov, V. Nikitin, E. Mikhalchenko, L. Stamov","doi":"10.3390/fire6090335","DOIUrl":"https://doi.org/10.3390/fire6090335","url":null,"abstract":"This paper presents the results of numerical simulation of a model combustion chamber of a pulse detonation engine using the authors’ developed software package. The main goal of the present study is to numerically investigate the effects of cyclic operation of pulse detonating chambers, as the former studies have been limited to simulating one cycle. To achieve this goal, a new mathematical model for heavy gas was applied simulating condensed fuel phase, which made it possible to accelerate computations and simulate multi-cycle operation of the device. Distributions of such characteristics as temperature, pressure, velocity, concentrations of reagents, intensity of reactions, and thrust force are obtained. A two-stage kinetic model of propellant combustion is proposed. Attention is paid to the main stages of PDE operation: filling of the chamber with reagents, ignition and transition to detonation, products exhaust, purification, and cooling the chamber with a neutral gas. The simulation of the working cycle with the shortest period for the specified system parameters was carried out, the execution time of each stage was obtained, and an assessment was carried out to minimize the main stages of the work cycle. Numerical results demonstrated that the characteristics of the engine cycle are stabilized already in the second cycle: the thrust in the first cycle differs from the thrust in the second by 5%, in the third from the second by 1%. Moreover, details of thrust dynamics in the second and third cycles were studied.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48075802","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 shelf life of energetic materials (EMs) is directly associated with safety and functionality. Therefore, a priori knowledge of this parameter is essential. The standard approach for predicting the shelf life of EMs is tremendously time and money consuming. It involves massive accelerated aging tests at temperatures typically between 40 and 80 °C for relatively long time periods—from months to years—with different aging time intervals, followed by analysis of the aging-induced changes. A subsequent kinetic analysis with Arrhenius evaluation provides the effective activation energy for calculating shelf life at lower storage temperatures. In this work, a much less time- and resource-intensive approach based on the kinetic analysis of decomposition data gathered by using thermal analysis techniques is discussed as a possible alternative for the shelf life prediction of EMs. The discussion is placed in the context of the few but promising works of literature on the subject that provide evidence and examples. On the path towards the practical application of this approach, the definition of procedures that allow for a realistic simulation of storage conditions not only in the accelerated aging tests—still needed but limited to the validation of the decomposition kinetics—but also in the thermal analysis experiments is highlighted as one of the main issues to be addressed.
{"title":"An Alternative Approach for Predicting the Shelf Life of Energetic Materials","authors":"R. Sanchirico, V. Di Sarli","doi":"10.3390/fire6090333","DOIUrl":"https://doi.org/10.3390/fire6090333","url":null,"abstract":"The shelf life of energetic materials (EMs) is directly associated with safety and functionality. Therefore, a priori knowledge of this parameter is essential. The standard approach for predicting the shelf life of EMs is tremendously time and money consuming. It involves massive accelerated aging tests at temperatures typically between 40 and 80 °C for relatively long time periods—from months to years—with different aging time intervals, followed by analysis of the aging-induced changes. A subsequent kinetic analysis with Arrhenius evaluation provides the effective activation energy for calculating shelf life at lower storage temperatures. In this work, a much less time- and resource-intensive approach based on the kinetic analysis of decomposition data gathered by using thermal analysis techniques is discussed as a possible alternative for the shelf life prediction of EMs. The discussion is placed in the context of the few but promising works of literature on the subject that provide evidence and examples. On the path towards the practical application of this approach, the definition of procedures that allow for a realistic simulation of storage conditions not only in the accelerated aging tests—still needed but limited to the validation of the decomposition kinetics—but also in the thermal analysis experiments is highlighted as one of the main issues to be addressed.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-08-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45017565","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}
J. T. Benik, A. Farguell, J. Mirocha, C. Clements, A. Kochanski
Despite recent advances in both coupled fire modeling and measurement techniques to sample the fire environment, the fire–atmosphere coupling mechanisms that lead to fast propagating wildfires remain poorly understood. This knowledge gap adversely affects fire management when wildland fires propagate unexpectedly rapidly and shift direction due to the fire impacts on local wind conditions. In this work, we utilized observational data from the FireFlux2 prescribed burn and numerical simulations performed with a coupled fire–atmosphere model WRF-SFIRE to assess the small-scale impacts of fire on local micrometeorology under moderate wind conditions (10–12 m/s). The FireFlux2 prescribed burn provided a comprehensive observational dataset with in situ meteorological observations as well as IR measurements of fire progression. To directly quantify the effects of fire–atmosphere interactions, two WRF-SFIRE simulations were executed. One simulation was run in a two-way coupled mode in which the heat and moisture fluxes emitted from the fire were injected into the atmosphere, and the other simulation was performed in a one-way coupled mode for which the atmosphere was not affected by the fire. The difference between these two simulations was used to analyze and quantify the fire impacts on the atmospheric circulation at different sections of the fire front. The fire-released heat fluxes resulted in vertical velocities as high as 10.8 m/s at the highest measurement level (20 m above ground level) gradually diminishing with height and dropping to 7.9 m/s at 5.77 m. The fire-induced horizontal winds indicated the strongest fire-induced flow at the lowest measurement levels (as high as 3.3 m/s) gradually decreasing to less than 1 m/s at 20 m above ground level. The analysis of the simulated flow indicates significant differences between the fire-induced circulation at the fire head and on the flanks. The fire-induced circulation was much stronger near the fire head than at the flanks, where the fire did not produce particularly strong cross-fire flow and did not significantly change the lateral fire progression. However, at the head of the fire the fire-induced winds blowing across the front were the strongest and significantly accelerated fire progression. The two-way coupled simulation including the fire-induced winds produced 36.2% faster fire propagation than the one-way coupled run, and more realistically represented the fire progression.
{"title":"Analysis of Fire-Induced Circulations during the FireFlux2 Experiment","authors":"J. T. Benik, A. Farguell, J. Mirocha, C. Clements, A. Kochanski","doi":"10.3390/fire6090332","DOIUrl":"https://doi.org/10.3390/fire6090332","url":null,"abstract":"Despite recent advances in both coupled fire modeling and measurement techniques to sample the fire environment, the fire–atmosphere coupling mechanisms that lead to fast propagating wildfires remain poorly understood. This knowledge gap adversely affects fire management when wildland fires propagate unexpectedly rapidly and shift direction due to the fire impacts on local wind conditions. In this work, we utilized observational data from the FireFlux2 prescribed burn and numerical simulations performed with a coupled fire–atmosphere model WRF-SFIRE to assess the small-scale impacts of fire on local micrometeorology under moderate wind conditions (10–12 m/s). The FireFlux2 prescribed burn provided a comprehensive observational dataset with in situ meteorological observations as well as IR measurements of fire progression. To directly quantify the effects of fire–atmosphere interactions, two WRF-SFIRE simulations were executed. One simulation was run in a two-way coupled mode in which the heat and moisture fluxes emitted from the fire were injected into the atmosphere, and the other simulation was performed in a one-way coupled mode for which the atmosphere was not affected by the fire. The difference between these two simulations was used to analyze and quantify the fire impacts on the atmospheric circulation at different sections of the fire front. The fire-released heat fluxes resulted in vertical velocities as high as 10.8 m/s at the highest measurement level (20 m above ground level) gradually diminishing with height and dropping to 7.9 m/s at 5.77 m. The fire-induced horizontal winds indicated the strongest fire-induced flow at the lowest measurement levels (as high as 3.3 m/s) gradually decreasing to less than 1 m/s at 20 m above ground level. The analysis of the simulated flow indicates significant differences between the fire-induced circulation at the fire head and on the flanks. The fire-induced circulation was much stronger near the fire head than at the flanks, where the fire did not produce particularly strong cross-fire flow and did not significantly change the lateral fire progression. However, at the head of the fire the fire-induced winds blowing across the front were the strongest and significantly accelerated fire progression. The two-way coupled simulation including the fire-induced winds produced 36.2% faster fire propagation than the one-way coupled run, and more realistically represented the fire progression.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42871327","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 steel column performance in realistic structures during a fire has yet to be fully understood because existing research emphasizes single-story performance, thereby disregarding the influence of continuous steel columns in multi-story configurations devoid of fire. This paper presents a numerical study to comprehend the overall structural fire performance of continuous steel columns, considering the effect of loading ratios, restraint ratios, column continuity, and single-sided lateral moments. An advanced numerical model was initially developed using ABAQUS and validated against experimental tests. The validated numerical model was subsequently employed to investigate the effects of several parameters, including axial restraint ratios (α = 0.05–0.35) and axial load ratios (n = 0.3–0.8). The study findings indicated that the restraint ratios within the designed range have a slightly beneficial impact on the fire resistance of continuous steel columns. The column continuity did not exert a significant impact on the performance of steel columns in fire. Additionally, the comparison showed that the current design approach in EN 1993-1-2 was conservative for predicting the limiting temperature of internal and edge columns.
{"title":"Numerical Analysis of Restrained Continuous Steel Columns under Standard Fire","authors":"J. Sun, Fanqin Meng, K. Andisheh, G. Clifton","doi":"10.3390/fire6090330","DOIUrl":"https://doi.org/10.3390/fire6090330","url":null,"abstract":"The steel column performance in realistic structures during a fire has yet to be fully understood because existing research emphasizes single-story performance, thereby disregarding the influence of continuous steel columns in multi-story configurations devoid of fire. This paper presents a numerical study to comprehend the overall structural fire performance of continuous steel columns, considering the effect of loading ratios, restraint ratios, column continuity, and single-sided lateral moments. An advanced numerical model was initially developed using ABAQUS and validated against experimental tests. The validated numerical model was subsequently employed to investigate the effects of several parameters, including axial restraint ratios (α = 0.05–0.35) and axial load ratios (n = 0.3–0.8). The study findings indicated that the restraint ratios within the designed range have a slightly beneficial impact on the fire resistance of continuous steel columns. The column continuity did not exert a significant impact on the performance of steel columns in fire. Additionally, the comparison showed that the current design approach in EN 1993-1-2 was conservative for predicting the limiting temperature of internal and edge columns.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-08-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43074380","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}
An aspect of human responses to fires is perceiving changes in intensity. The nature of fires can make this challenging, as flames and smoke are dynamic and change with time. For developing fires, this is in addition to growth occurring vertically and sometimes horizontally, with the footprint of the fire either remaining the same or increasing in size. The present study investigated how precisely humans could visually detect differences in the intensities and growth rates of simulated fires. Using a similar approach to research with non-symbolic visual quantities, a series of experiments compared the precision of judgments regarding which of two simulated fires was greater in intensity or growing faster in intensity when the footprint was fixed or varied. In addition, participants reported what characteristics they used to make their judgments. Precision was significantly worse when comparing the growth rates versus the intensities of fires, and it was better when the fire footprint varied. This provides initial estimates of the precision of mental representations of fire intensity and growth. In addition, participants reported using multiple characteristics, including the size of flames and smoke produced. The present study indicates that humans can precisely detect differences in the intensities of fires using visual cues, but have difficulty when comparing growth rates. We discuss how this suggests that the growth rate may not be a reliable visual cue used by occupants when responding to fires.
{"title":"Precision of Visual Perception of Developing Fires","authors":"Justin W. Bonny, J. Milke","doi":"10.3390/fire6090328","DOIUrl":"https://doi.org/10.3390/fire6090328","url":null,"abstract":"An aspect of human responses to fires is perceiving changes in intensity. The nature of fires can make this challenging, as flames and smoke are dynamic and change with time. For developing fires, this is in addition to growth occurring vertically and sometimes horizontally, with the footprint of the fire either remaining the same or increasing in size. The present study investigated how precisely humans could visually detect differences in the intensities and growth rates of simulated fires. Using a similar approach to research with non-symbolic visual quantities, a series of experiments compared the precision of judgments regarding which of two simulated fires was greater in intensity or growing faster in intensity when the footprint was fixed or varied. In addition, participants reported what characteristics they used to make their judgments. Precision was significantly worse when comparing the growth rates versus the intensities of fires, and it was better when the fire footprint varied. This provides initial estimates of the precision of mental representations of fire intensity and growth. In addition, participants reported using multiple characteristics, including the size of flames and smoke produced. The present study indicates that humans can precisely detect differences in the intensities of fires using visual cues, but have difficulty when comparing growth rates. We discuss how this suggests that the growth rate may not be a reliable visual cue used by occupants when responding to fires.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42196517","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}
In fire-prone ecosystems, plant resilience to recurrent fires depends on certain fire-adaptive traits. However, how key functional and reproductive traits of graminoids respond to varying burning seasons is poorly understood. This meta-analysis, therefore, unpacks global perspectives on how resprouting, growth, reproductive, and productivity traits of graminoids (grasses and sedges) respond to different burning seasons. We recorded 569 observations from 80 experimental studies comparing graminoid plant trait responses in unburned vs. burned treatments over different seasons of burn. Weighted log response ratios and 95% confidence intervals (95%CI) were analyzed for each plant trait using random effects models and compared across burning seasons. Summer (0.35 (95%CI = 0.25 to 0.46)) and autumn burns (0.24 (95%CI = 0.16 to 0.31)) increased above-ground biomass m−2, while biomass plant−1 was increased only by spring burns (0.27 (95%CI = 0.22 to 0.32)). Bud production plant−1 and tiller−1 were reduced significantly by fire, especially spring, summer, and autumn burns. The shoot height (0.29 (95%CI = 0.17 to 0.41)), leaf length (0.15 (95%CI = 0.11 to 0.20)), and specific leaf area (0.08 (95%CI = 0.06 to 0.09)) increased only under summer burns, while flowering was enhanced by spring (0.19 (95%CI = 0.00 to 0.38)) and autumn burns [0.34 (95%CI = 0.02 to 0.66)]. However, seed production m−2 was reduced by spring and summer burns and the opposite was true for seed production plant−1. Overall, herbaceous plant trait responses to fire varied by the season of burn, disagreeing with the general principle that early spring burning is the best practice. We suggest that a decision on the season of burn should be informed by the objective of burning.
{"title":"A Global Perspective of the Functional Trait Responses of Graminoids to the Seasonality of Fire","authors":"M. Mndela, Humphrey K. Thamaga, B. Gusha","doi":"10.3390/fire6090329","DOIUrl":"https://doi.org/10.3390/fire6090329","url":null,"abstract":"In fire-prone ecosystems, plant resilience to recurrent fires depends on certain fire-adaptive traits. However, how key functional and reproductive traits of graminoids respond to varying burning seasons is poorly understood. This meta-analysis, therefore, unpacks global perspectives on how resprouting, growth, reproductive, and productivity traits of graminoids (grasses and sedges) respond to different burning seasons. We recorded 569 observations from 80 experimental studies comparing graminoid plant trait responses in unburned vs. burned treatments over different seasons of burn. Weighted log response ratios and 95% confidence intervals (95%CI) were analyzed for each plant trait using random effects models and compared across burning seasons. Summer (0.35 (95%CI = 0.25 to 0.46)) and autumn burns (0.24 (95%CI = 0.16 to 0.31)) increased above-ground biomass m−2, while biomass plant−1 was increased only by spring burns (0.27 (95%CI = 0.22 to 0.32)). Bud production plant−1 and tiller−1 were reduced significantly by fire, especially spring, summer, and autumn burns. The shoot height (0.29 (95%CI = 0.17 to 0.41)), leaf length (0.15 (95%CI = 0.11 to 0.20)), and specific leaf area (0.08 (95%CI = 0.06 to 0.09)) increased only under summer burns, while flowering was enhanced by spring (0.19 (95%CI = 0.00 to 0.38)) and autumn burns [0.34 (95%CI = 0.02 to 0.66)]. However, seed production m−2 was reduced by spring and summer burns and the opposite was true for seed production plant−1. Overall, herbaceous plant trait responses to fire varied by the season of burn, disagreeing with the general principle that early spring burning is the best practice. We suggest that a decision on the season of burn should be informed by the objective of burning.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-08-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46387777","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}
Bojan Mihajlovski, P. Fernandes, J. Pereira, J. Guerra-Hernández
Wildfires burn millions of hectares of forest worldwide every year, and this trend is expected to continue growing under current and future climate scenarios. As a result, accurate knowledge of fuel conditions and fuel type mapping are important for assessing fire hazards and predicting fire behavior. In this study, 499 plots in six different areas in Portugal were surveyed by ALS and multisource RS, and the data thus obtained were used to evaluate a nationwide fuel classification. Random Forest (RF) and CART models were used to evaluate fuel models based on ALS (5 and 10 pulse/m2), Sentinel Imagery (Multispectral Sentinel 2 (S2) and SAR (Synthetic Aperture RaDaR) data (C-band (Sentinel 1 (S1)) and Phased Array L-band data (PALSAR-2/ALOS-2 Satellite) metrics. The specific goals of the study were as follows: (1) to develop simple CART and RF models to classify the four main fuel types in Portugal in terms of horizontal and vertical structure based on field-acquired ALS data; (2) to analyze the effect of canopy cover on fuel type classification; (3) to investigate the use of different ALS pulse densities to classify the fuel types; (4) to map a more complex classification of fuel using a multi-sensor approach and the RF method. The results indicate that use of ALS metrics (only) was a powerful way of accurately classifying the main four fuel types, with OA = 0.68. In terms of canopy cover, the best results were estimated in sparse forest, with an OA = 0.84. The effect of ALS pulse density on fuel classification indicates that 10 points m−2 data yielded better results than 5 points m−2 data, with OA = 0.78 and 0.71, respectively. Finally, the multi-sensor approach with RF successfully classified 13 fuel models in Portugal, with moderate OA = 0.44. Fuel mapping studies could be improved by generating more homogenous fuel models (in terms of structure and composition), increasing the number of sample plots and also by increasing the representativeness of each fuel model.
{"title":"Comparing Forest Understory Fuel Classification in Portugal Using Discrete Airborne Laser Scanning Data and Satellite Multi-Source Remote Sensing Data","authors":"Bojan Mihajlovski, P. Fernandes, J. Pereira, J. Guerra-Hernández","doi":"10.3390/fire6090327","DOIUrl":"https://doi.org/10.3390/fire6090327","url":null,"abstract":"Wildfires burn millions of hectares of forest worldwide every year, and this trend is expected to continue growing under current and future climate scenarios. As a result, accurate knowledge of fuel conditions and fuel type mapping are important for assessing fire hazards and predicting fire behavior. In this study, 499 plots in six different areas in Portugal were surveyed by ALS and multisource RS, and the data thus obtained were used to evaluate a nationwide fuel classification. Random Forest (RF) and CART models were used to evaluate fuel models based on ALS (5 and 10 pulse/m2), Sentinel Imagery (Multispectral Sentinel 2 (S2) and SAR (Synthetic Aperture RaDaR) data (C-band (Sentinel 1 (S1)) and Phased Array L-band data (PALSAR-2/ALOS-2 Satellite) metrics. The specific goals of the study were as follows: (1) to develop simple CART and RF models to classify the four main fuel types in Portugal in terms of horizontal and vertical structure based on field-acquired ALS data; (2) to analyze the effect of canopy cover on fuel type classification; (3) to investigate the use of different ALS pulse densities to classify the fuel types; (4) to map a more complex classification of fuel using a multi-sensor approach and the RF method. The results indicate that use of ALS metrics (only) was a powerful way of accurately classifying the main four fuel types, with OA = 0.68. In terms of canopy cover, the best results were estimated in sparse forest, with an OA = 0.84. The effect of ALS pulse density on fuel classification indicates that 10 points m−2 data yielded better results than 5 points m−2 data, with OA = 0.78 and 0.71, respectively. Finally, the multi-sensor approach with RF successfully classified 13 fuel models in Portugal, with moderate OA = 0.44. Fuel mapping studies could be improved by generating more homogenous fuel models (in terms of structure and composition), increasing the number of sample plots and also by increasing the representativeness of each fuel model.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-08-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"48368781","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}
Iacopo Bassi, Claudia Bandinelli, Francesca Delchiaro, Marco Piana, Gianluca Sarti
Regulation (EU) No 305/2011 lays down harmonized conditions for marketing construction products in the European Union. One of its consequences has been the introduction of the product standard EN 50575 and standard EN 130501-6, concerning power, control, and communication cables permanently installed in buildings to prevent the risk of a fire and its consequences. EN 13501-6 provides the reaction to fire classifications for cables, the test methods to be performed, the requirements to meet a specific reaction to fire, and additional classifications for smoke production, flaming droplets, and acidity. It requires EN 60754-2 as the technical standard to assess acidity, and it defines three classes: a1, a2, and a3 (the less performant). Due to the release of hydrogen chloride during the combustion, acidity is the weak point of PVC cables, which are not yet capable of achieving the a1 or a2 classes required for specific locations according to fire risk assessments. EN 13501-6 does not include EN 60754-1, used in harmonized standards outside the scope of Regulation (EU) No 305/2011. EN 60754-1 and EN 60754-2 are common standards for determining halogen gas content, and acidity/conductivity, respectively. While they involve the same type of test apparatus, they differ in heating regimes, final temperatures, and detection methods. In particular, EN 60754-2 requires testing at temperatures between 935–965 °C in the tube furnace, where the sample burns, the smoke is collected in bubblers, and pH and conductivity are measured as an indirect assessment of acidity. On the other hand, the temperature regime of EN 60754-1 is a gradual heating run, followed by isothermal heating at 800 °C. The paper shows that when potent acid scavengers are used in PVC compounds, performing EN 60754-2 with the thermal profile of EN 60754-1 or at 500 °C in isothermal conditions, the evolution of hydrogen chloride changes significantly up to 10 times less than the test performed in isothermal at 950 °C. The reason lies behind the kinetic of hydrogen chloride release during the combustion of PVC compounds: the higher the temperature or faster the heat release, the quicker hydrogen chloride evolution and the lower the probability for the acid scavenger to trap it. Thus, these findings emphasize the “fragility” of EN 60754-2 as a tool for assessing risks associated with the release of hydrogen chloride during fires.
法规(EU) No 305/2011规定了在欧盟销售建筑产品的协调条件。其结果之一是引入了产品标准EN 50575和标准EN 130501-6，涉及永久安装在建筑物中的电源，控制和通信电缆，以防止火灾及其后果的风险。EN 13501-6提供了电缆对火灾的反应分类，要执行的测试方法，满足特定火灾反应的要求，以及烟雾产生，燃烧液滴和酸度的额外分类。它要求EN 60754-2作为评估酸度的技术标准，并定义了三个等级:a1, a2和a3(性能较差)。由于在燃烧过程中会释放出氯化氢，酸性是PVC电缆的弱点，根据火灾风险评估，PVC电缆还不能达到特定场所所需的a1或a2等级。EN 13501-6不包括EN 60754-1，用于法规(EU) No 305/2011范围之外的协调标准。EN 60754-1和EN 60754-2分别是测定卤素气体含量和酸度/电导率的通用标准。虽然它们涉及相同类型的测试设备，但它们在加热制度，最终温度和检测方法上有所不同。特别是，EN 60754-2要求在管式炉中在935-965°C的温度下进行测试，其中样品燃烧，烟雾收集在起泡器中，并测量pH值和电导率作为酸度的间接评估。另一方面，EN 60754-1的温度制度是一个渐进的加热运行，然后是800°C的等温加热。该论文表明，当在PVC化合物中使用强效酸清除剂时，在EN 60754-2和EN 60754-1的热分布或在500°C等温条件下，氯化氢的演变变化明显小于在950°C等温条件下进行的测试的10倍。其原因在于聚氯乙烯化合物燃烧过程中氯化氢释放的动力学:温度越高或释放热量越快，氯化氢的释放速度越快，酸清除剂捕获氯化氢的可能性越低。因此，这些发现强调了EN 60754-2作为评估火灾中氯化氢释放相关风险的工具的“脆弱性”。
{"title":"A New Perspective on Hydrogen Chloride Scavenging at High Temperatures for Reducing the Smoke Acidity of PVC Cables in Fires V: Comparison between EN 60754-1 and EN 60754-2","authors":"Iacopo Bassi, Claudia Bandinelli, Francesca Delchiaro, Marco Piana, Gianluca Sarti","doi":"10.3390/fire6080326","DOIUrl":"https://doi.org/10.3390/fire6080326","url":null,"abstract":"Regulation (EU) No 305/2011 lays down harmonized conditions for marketing construction products in the European Union. One of its consequences has been the introduction of the product standard EN 50575 and standard EN 130501-6, concerning power, control, and communication cables permanently installed in buildings to prevent the risk of a fire and its consequences. EN 13501-6 provides the reaction to fire classifications for cables, the test methods to be performed, the requirements to meet a specific reaction to fire, and additional classifications for smoke production, flaming droplets, and acidity. It requires EN 60754-2 as the technical standard to assess acidity, and it defines three classes: a1, a2, and a3 (the less performant). Due to the release of hydrogen chloride during the combustion, acidity is the weak point of PVC cables, which are not yet capable of achieving the a1 or a2 classes required for specific locations according to fire risk assessments. EN 13501-6 does not include EN 60754-1, used in harmonized standards outside the scope of Regulation (EU) No 305/2011. EN 60754-1 and EN 60754-2 are common standards for determining halogen gas content, and acidity/conductivity, respectively. While they involve the same type of test apparatus, they differ in heating regimes, final temperatures, and detection methods. In particular, EN 60754-2 requires testing at temperatures between 935–965 °C in the tube furnace, where the sample burns, the smoke is collected in bubblers, and pH and conductivity are measured as an indirect assessment of acidity. On the other hand, the temperature regime of EN 60754-1 is a gradual heating run, followed by isothermal heating at 800 °C. The paper shows that when potent acid scavengers are used in PVC compounds, performing EN 60754-2 with the thermal profile of EN 60754-1 or at 500 °C in isothermal conditions, the evolution of hydrogen chloride changes significantly up to 10 times less than the test performed in isothermal at 950 °C. The reason lies behind the kinetic of hydrogen chloride release during the combustion of PVC compounds: the higher the temperature or faster the heat release, the quicker hydrogen chloride evolution and the lower the probability for the acid scavenger to trap it. Thus, these findings emphasize the “fragility” of EN 60754-2 as a tool for assessing risks associated with the release of hydrogen chloride during fires.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42062917","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}
M. Hassan, Nazra Hameed, Md. Delwar Hossain, Md Rayhan Hasnat, Grahame Douglas, S. Pathirana, P. Rahnamayiezekavat, S. Saha
Electric Vehicles (EVs) offer a promising solution to reduce the environmental impact compared to internal combustion engine vehicles. However, EV adoption in Australia has been hindered by concerns over fire safety. This study aims to comprehensively analyse EV fire risks and trends in Australia, including those related to charging stations and lithium-ion batteries. The research utilises secondary data from various reputable sources to develop statistical forecasting models, which estimate that Australia will have approximately 1.73 million EVs by 2030 and 15.8 million by 2050. The study reveals an average EV fire frequency of six fires per million EVs in Australia, aligning with the global average. Consequently, Australia is expected to experience 9 to 10 EV fire incidents annually in 2030, 37 to 42 EV fire incidents annually in 2040, and 84 to 95 EV fire incidents annually in 2050. To address these risks, an EV fire risk control framework is considered to identify and recommend appropriate measures for life safety, lithium-ion batteries, charging, EV handling, and EV locations. This research provides vital evidence for regulators, policymakers, and the fire industry to effectively manage EV fire risks and enhance preparedness for the growing EV market in Australia.
{"title":"Fire Incidents, Trends, and Risk Mitigation Framework of Electrical Vehicle Cars in Australia","authors":"M. Hassan, Nazra Hameed, Md. Delwar Hossain, Md Rayhan Hasnat, Grahame Douglas, S. Pathirana, P. Rahnamayiezekavat, S. Saha","doi":"10.3390/fire6080325","DOIUrl":"https://doi.org/10.3390/fire6080325","url":null,"abstract":"Electric Vehicles (EVs) offer a promising solution to reduce the environmental impact compared to internal combustion engine vehicles. However, EV adoption in Australia has been hindered by concerns over fire safety. This study aims to comprehensively analyse EV fire risks and trends in Australia, including those related to charging stations and lithium-ion batteries. The research utilises secondary data from various reputable sources to develop statistical forecasting models, which estimate that Australia will have approximately 1.73 million EVs by 2030 and 15.8 million by 2050. The study reveals an average EV fire frequency of six fires per million EVs in Australia, aligning with the global average. Consequently, Australia is expected to experience 9 to 10 EV fire incidents annually in 2030, 37 to 42 EV fire incidents annually in 2040, and 84 to 95 EV fire incidents annually in 2050. To address these risks, an EV fire risk control framework is considered to identify and recommend appropriate measures for life safety, lithium-ion batteries, charging, EV handling, and EV locations. This research provides vital evidence for regulators, policymakers, and the fire industry to effectively manage EV fire risks and enhance preparedness for the growing EV market in Australia.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-08-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"45105495","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}
Bolun Li, Wei Zhang, Yucheng Li, Zhitao Zhang, Jinyang Dong, Y. Cui
Semiclosed tunnels are very common in engineering construction. They are not connected, so they easily accumulate heat. Once a fire breaks out in a semiclosed tunnel, the route for rescue workers to enter is limited, so it is tough to get close to the fire source. In this paper, taking a mine excavation roadway with local pressure ventilation as an example, the temperature field distribution and water spray fire prevention characteristics of the excavation roadway face were studied using numerical simulation and theoretical analysis. This paper provides an explanation of a dynamics-based smoke management method for water spraying in a semiclosed tunnel as well as the equilibrium relationship between droplet drag force and smoke buoyancy. A method was first developed to calculate the quantity of smoke blockage based on the thickness of the smoke congestion. The local ventilation and smoke movement created a circulating flow in the excavation face, which was discovered by investigating the velocity and temperature fields of the excavation face. The size of the high-temperature area and the pattern of temperature stratification varied due to this circulating flow. When local ventilation and sprinkler systems were operating simultaneously, when the volume of smoke was small, the smoke avoided the majority of the water spray effect with the circulation flow; however, when the volume of smoke was large, the effect of the circulation flow decreased and the smoke gathered close to the sprinkler head. At this time, the blocking effect of the water spray was significant. The mean square error analysis revealed that activating the sprinkler had the most significant cooling impact on the wall on one side of the air duct.
{"title":"Study on the Temperature and Smoke Movement in the Event of a Fire in a Semiclosed Tunnel under Water Spray","authors":"Bolun Li, Wei Zhang, Yucheng Li, Zhitao Zhang, Jinyang Dong, Y. Cui","doi":"10.3390/fire6080324","DOIUrl":"https://doi.org/10.3390/fire6080324","url":null,"abstract":"Semiclosed tunnels are very common in engineering construction. They are not connected, so they easily accumulate heat. Once a fire breaks out in a semiclosed tunnel, the route for rescue workers to enter is limited, so it is tough to get close to the fire source. In this paper, taking a mine excavation roadway with local pressure ventilation as an example, the temperature field distribution and water spray fire prevention characteristics of the excavation roadway face were studied using numerical simulation and theoretical analysis. This paper provides an explanation of a dynamics-based smoke management method for water spraying in a semiclosed tunnel as well as the equilibrium relationship between droplet drag force and smoke buoyancy. A method was first developed to calculate the quantity of smoke blockage based on the thickness of the smoke congestion. The local ventilation and smoke movement created a circulating flow in the excavation face, which was discovered by investigating the velocity and temperature fields of the excavation face. The size of the high-temperature area and the pattern of temperature stratification varied due to this circulating flow. When local ventilation and sprinkler systems were operating simultaneously, when the volume of smoke was small, the smoke avoided the majority of the water spray effect with the circulation flow; however, when the volume of smoke was large, the effect of the circulation flow decreased and the smoke gathered close to the sprinkler head. At this time, the blocking effect of the water spray was significant. The mean square error analysis revealed that activating the sprinkler had the most significant cooling impact on the wall on one side of the air duct.","PeriodicalId":36395,"journal":{"name":"Fire-Switzerland","volume":" ","pages":""},"PeriodicalIF":3.2,"publicationDate":"2023-08-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43413689","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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