Fire Characteristics Research Articles

Characteristics Based Fire Detection System Under the Effect of Electric Fields With Improved Yolo-v4 and ViBe

To address slow image-based detection of fires under the effect of electric fields and its limitation to static fire characteristics, this paper proffersa video-based fire detection system with improved you only look once version 4 (Yolo-v4) and visual background extractor (ViBe) algorithms. The proposed system uses a simplified weighted bi-directional feature pyramid network (Bi-FPN) in place of the path aggregation network (PANet) as a feature fusion network in Yolo-v4. Using multiple dynamic fire characteristics, it can eliminate falsely detected frames. The ViBe algorithm is improved to consider the sudden change of light triggered by fire flickering. Compared with other fire detection algorithms, the proposed system achieves 98.9% fire detection accuracy with a false detection rate of 2.2%. It can extract target fires by adjusting to sudden changes of light using no more than 16 frames. Moreover, the system achieves fire detection with more dynamic fire characteristics compared with the image-based fire detection under the effect of electric fields.

Testing of Large Scale Pool Fire of Technical Ethanol

Aim: The aim of this article is to determine the characteristics of a pool fire, including the temperatures and thermal radiation densities caused by it. Mappings of pool fires occurring in actual emergency events were conducted by performing large-scale polygon tests. Project and methods: Experimental study of pool fire of technical ethanol was carried out on a specially built test stand in the training area of the Training Centre in Pionki of the Regional Headquarters of the State Fire Service in Warsaw. The pool fire test stand consisted of a test tray, with a test chamber with the diameter of 300 cm, founded on a reinforced concrete slab. Using a developed measurement system with data acquisition that included measurement sensors mounted at defined locations relative to the fire, temperatures and thermal radiation densities were measured at various distances/locations relative to the fire. Metrological data such as air temperature, atmospheric pressure, humidity, wind direction and speed were monitored and recorded using the weather station. The height of the fire flame was measured by comparing it to racks set up nearby with marked scales of specific lengths. Results: A polygon stand that was built to study pool fires, equipped with a temperature and thermal radiation density measuring system with measuring sensors distributed in defined locations, is discussed. A study of a pool fire resulting from the combustion of dehydrated, fully contaminated ethanol was conducted. The study measured temperatures, thermal radiation densities, and flame heights. The average and maximum values of temperatures and thermal radiation densities during the steady-state combustion stage (i.e., phase II of the fire) were determined. Conclusions: Based on the presented results of temperature and thermal radiation density measurements at various distances/locations relative to the pool fire site, there was a significant effect of wind direction and speed on these values. Higher temperature and heat radiation density were recorded at the sensors on the leeward side than on the windward side. As the wind speed decreased, there was an increase in the temperature values recorded on the thermocouples located above the centre of the bottom of the tray test chamber due to the flame, which, when not blown away, was allowed to rise vertically upward and fully sweep the temperature sensors. Keywords: pool fire, field tests, technical ethanol, temperature, thermal radiation Type of article: original scientific article

Fire Risk Assessment and Experimental Study of Transformer Insulating Oil

Most previous works concentrated on burning characteristics of pool fire using common fuels such as heptane, propane, biodiesel, and diesel, whereas burning characteristics for transformer oil are barely involved, although transformer oil is arguable of more practical importance in power system. This study performed a series of pool fire experiments using transformer oil to study the burning characteristics in open and confined spaces. Three fuel thicknesses and five initial temperatures are changed in open space. The essential parameters of mass loss rate, flame height, and fire plume temperature are obtained and analyzed. Moreover, three oil pool diameters are varied in a chamber. The main conclusions are summarized as follows: the variations of mass loss rate, flame height, and fire plume temperature not only obviously increase as the fuel thickness increases from 0.5 cm to 1.0 cm, but also insignificantly increase as the fuel thickness changes from 1.0 cm to 2.0 cm. The mass loss rate is less sensitive to the initial temperature of transformer oil, but the flame height and fire plume temperature significantly rise with the initial temperature. Moreover, the modified models to predict the flame height and fire plume temperature for 25°C initial temperature conditions are proposed, but the fitting coefficients are obviously different from that for common liquid fuels. The flame height in confined space is higher and will rapidly increase to the maximum, then decreases, and tends to be stable, which is obviously different from the oil pool fire burning in open space. In addition, the phenomenon of burning blast and the ignition of the adjacent oil pool will be observed with a high‐temperature ignition source and a certain high temperature in a chamber under 30 cm oil pool diameter, which will not be recorded in 15 cm and 20 cm.

Research on online monitoring and cause identification system of building electrical fire

Frequent building electrical fire accidents have brought great harm to life and property. In order to prevent the occurrence of accidents and reduce the losses to the greatest extent, it is necessary to take effective measures for building electrical fires. Based on the Internet of things (IoT) technology, a system for online monitoring and cause identification of building electrical fire is proposed in this paper. For both hardware and software, this paper introduces the overall structure, component units and system functions in detail. According to the characteristics of arc fault and fire, the complete scheme of online monitoring is given, and the system workflow is also described to realize the cause identification. Finally, the effectiveness of this system is verified by practical testing. The results show that the proposed system is helpful to solve the problems in monitoring and cause identification of building electrical fire, which can not only provide decision-making basis for firefighting, but also provide strong technical support for improving the safety of low-voltage power grid.

Review Of Fire And Smoke Control With Ventilation Systems In Tunnels

Underground spaces were paid more attention in the 21st century. As a special underground space, the development of tunnels was even faster. The damage in tunnel, caused by fire and other hazards, is worse than that in spaces above ground due to construction characteristics of underground spaces. Hot smoke cannot be exhausted in time when a fire occurs in tunnel. Therefore, space temperature rises quickly and flashover occurs. Meanwhile, smoke will be accumulated because of poor ventilation. Incomplete combustion, and production of harmful gases such as CO were caused. This review regarding modelling and design methods, based on the characteristics of tunnel fires, summarizes earlier findings and proposes further study plans.

Effects of Spacing Distance and Fuel Mass Thickness on Combustion and Flame Merging Characteristics of Two-Line Pool Fires

Effects of Spacing Distance and Fuel Mass Thickness on Combustion and Flame Merging Characteristics of Two-Line Pool Fires

Fire scar characteristics in two tropical montane conifer species from central Mexico

Fire scar analysis is a fundamental tool for reconstructing fire regimes in conifer forests. However, little is known about fire scar properties in tropical montane conifers, where some assumptions limit dendroecological research. These include that fir species do not exhibit external fire scars and that pines without external fire scars have not experienced past fires. This study describes fire scar patterns in two conifer species growing in Mexican temperate forests: sacred fir (Abies religiosa) and smooth-bark Mexican pine (Pinus pseudostrobus). We extracted cross-sections from 110 trees and measured tree age, basal diameter, bark thickness, fire scar size and seasonality, the number of scars per tree, years and basal diameter from pith to the first scar, and the proportion of external and buried fire scars. Most trees had three fire scars, which appeared during the dry season after the first 15 years measured from the pith. Old and large-diameter trees did not have more fire scars, but the time between fire scars influenced fire scar closure in sacred firs. Bark thickness and the proportion of visible and buried fire scars were similar in both species. Our results suggest that the absence of visible fire scars in smooth-bark Mexican pines does not imply the absence of fire, and sacred firs can exhibit external fire scars like pines.

The characteristics of ventilated pool fires of Daegok-Sosa subway lines using Model-Scale tunnels and stations

The characteristics of ventilated pool fires for Daegok-Sosa subway lines with a length of 15.12 km in Seoul, South Korea were studied. The model-scale tunnels and stations were built in scale 1:50 and temperature distribution, smoke (Carbon Monoxide (CO)) spreading, back-layering phenomenon and longitudinal ventilated flow velocity were systematically investigated. Present subscale model was based on the Froude number similitude and a heptane pool fire was used as the heat source. Heat release rate of pool fire in model-scale tunnel was 1.13 kW corresponding to an equivalent 20 MW in full scale. The occurrence of smoke back-layering phenomenon could be observed by whether the upstream temperature rose at a certain position during the whole process of the fire test. In the single line parallel tunnel, the smoke was restricted to downstream of fire source, however, in the double track tunnel the smoke back layering slightly occurred in upstream region of fire source and then it soon disappeared. The smoke propagated far downstream side and the tunnel safety measures should be taken for passenger’s safe evacuation from the CO toxic gas. The longitudinal air velocities in upstream side near the fire source were accelerated and were about 11% higher than the downstream velocities in single line parallel tunnel and more than 20% higher in double track tunnel caused by the blocking effect of fire source. A generalized quasi one-dimensional flow network solver was employed to calculate the longitudinal air velocity in tunnels using the finite volume Ghost Junction Method (GJM) which were compared with the present experimental data. The required minimum longitudinal air velocities (2.0 m/sec for single line parallel tunnel and 2.5 m/sec for double track tunnel) specified in the Korean railway facility technical standards were well satisfied in this experiment.

Improved seismic response of light-frame-timber panels with cement-particle-board sheathing of various thicknesses and different configurations of fasteners

Due to their comparable fire characteristics and surface preparation, light-frame timber panels using cement-particle boards (CPB) as a sheathing material present a potential alternative to gypsum-fibre boards. An experimental campaign was conducted to evaluate the behaviour of CPB light-frame-timber panels under in-plane lateral loading. Monotonic and cyclic in-plane shear tests were conducted on full-size panels, following preceding tests on the stapled sheathing-to-timber connections used in the panels. The influence of the boards’ thickness and staple geometry on the response of connections and panels was studied, also on panels with an asymmetrical CPB layout, which proved not to have a negative influence on the panels’ lateral load-bearing capacity. Furthermore, in order to improve the seismic response, panels, which had almost twice the number of staples compared to the basic panel, were tested; one variation with two rows of staples, and the other with the staples spaced closer together, such that the spacing distance was halved. The tests revealed a significant, though not proportional, increase in lateral resistance in the strengthened panels. Fastening the CPB with two rows of staples proved the better option, since subsequent failure of the CPB along the connections, as opposed to ductile failure of the staples in the basic panels, proved not to reduce the panels’ deformation capacity. The paper also compares the test results of the connections and panels to analytical results according to Eurocode 5 (EC5), the European code provision for the design of timber structures.

Detection of forest fire burn-area using landsat-8 and sentinel-2: a case study of Nivale (Kolhapur) beat of Chandoli National Park, Maharashtra, India

Forests play an important role in maintaining environmental equilibrium in the ecosystem. Forest fires, which can occur for a variety of reasons, are the greatest threat to forests. In order to control forest fires, it is critical to assess the formation and behavioral characteristics of forest fires. Detecting fire areas and the severity is much easier with satellite images obtained with advancing technologies. The main objective of this study is to extract burn area from Landsat-8 and Sentinel-2 satellite images of 2017 using six vegetation indices. Remote sensing data was used to study a forest fire in the Nivale (Kolhapur) beat of Chandoli National Park of Maharashtra. The Department of Divisional Forest Officer (Wildlife)- Chandoli National Park at Karad (DDFO-CNP) provided reference data indicating that the fire had damaged 194 hectares of Scrub forest. In addition, forest fire areas were determined using an objectbased image classification technique. When the findings of the study are compared to the values obtained by DDFO- CNP, it is found that Sentinel-2's object-based analysis provided the highest accuracy with an overall accuracy of 84 % and 0.795 Kappa statistics. Landsat-8 image has 82 % overall accuracy and 0.765 Kappa value. The findings of Sentinel-2 and Landsat-8 spectral indices showed the Sentinel-2 had better results in all indices. Differenced Normalized Difference Vegetation Index (dNDVI) and Relative Difference Normalized Burn Ratio (RdNBR) performed better than other indexes with a difference of only 18.27 and 30.88 hectares respectively. According to the fire severity analysis, a burn area with high intensity in Sentinel-2 was identified as moderate-high in Landsat-8. As per the research findings, sentinel-2 had a high severity area of 28.72 ha and a low severity area of 37.04 ha. It shows that satellite images of Sentinel-2 are highly suitable than Landsat-8 for estimating scrub forest fire areas. Finally, the findings of this study could be useful to forest managers to monitor burn regions quickly after the fire and in reducing severity and frequency of forest fires.

Analysis of Fire Hazards Associated with the Operation of Electric Vehicles in Enclosed Structures

The article discusses the analysis of the possible development of hazards associated with the operation of vehicles equipped with an electric drive using the example of passenger cars. The authors review the problem of the safety of people and property resulting from the occurrence of a fire in an electric passenger car, in the context of fires that have occurred in recent years. Particular attention was paid to the analysis of the state of knowledge concerning the characteristics of the fire progression in an electric car, its heat release rate curve [HRR], total heat release [THR], heat of combustion and factors affecting the fire progression. In this paper, an attempt was made to compare the fire characteristics of an electric car and a passenger car equipped with an internal combustion engine together with an estimation, using CFD simulations, of the impact on the safety of people and property in closed structures such as underground garages or road tunnels. The need for further development of research on electric cars equipped with large lithium-ion batteries in the context of their fire safety is indicated. The authors pay attention to the insufficient amount of data available to understand the fire characteristics of modern electric cars, which would enable the appropriate design of fire safety systems in building structures.

Changes in fire behavior caused by fire exclusion and fuel build-up vary with topography in California montane forests, USA

Wildfire sizes and proportions burned with high severity effects are increasing in seasonally dry forests, especially in the western USA. A critical need in efforts to restore or maintain these forest ecosystems is to determine where fuel build-up caused by fire exclusion reaches thresholds that compromise resilience to fire. Empirical studies identifying drivers of fire severity patterns in actual wildfires can be confounded by co-variation of vegetation and topography and the stochastic effects of weather and rarely consider long-term changes in fuel caused by fire exclusion.To overcome these limitations, we used a spatially explicit fire model (FlamMap) to compare potential fire behavior by topographic position in Lassen Volcanic National Park (LAVO), California, a large (43,000 ha), mountainous, unlogged landscape with extensive historical and contemporary fuels data. Fuel loads were uniformly distributed and incrementally increased across the landscape, meaning variation in fire behavior within each simulation was due to topography and among simulations, to fuels. We analyzed changes in fire line intensity (FLI) and crown fire potential as surface and canopy fuels increased from historical to contemporary levels and with percentile and actual wildfire weather conditions.Sensitivity to the influence of fuel build-up on fire behavior varied by topographic position. Steep slopes and ridges were most sensitive. At lower surface fuel loads, under pre-exclusion and contemporary canopy conditions, fire behavior was comparable and remained surface-type. As fuels increased, FLI and passive crown fire increased on steep slopes and ridgetops but remained largely unchanged on gentle slopes. Topographic variability in fire behavior was greatest with intermediate fuels. At higher surface fuel loads, under contemporary canopy fuels, passive crown fire dominated all topographic positions. With LAVO's current surface fuels, the area with potential for passive crown fire during actual fire weather increased from 6% pre-exclusion to 34% due to canopy fuel build-up. For topographically diverse landscapes, the results highlight where contemporary fire characteristics are most likely to deviate from historical patterns and may help managers prioritize locations for prescribed burning and managed wildfire to increase fire resilience in fuel rich landscapes.

Experimental and Theoretical Research on the Radiative Heat Transfer Characteristics of Transformer Oil Jet Flame

ABSTRACT In this paper, a series of transformer oil jet fire experiments with different tanks of inner diameters (0.05 m/0.08 m/0.1 m), different filling rate (80%/100%) and different pool diameters (0.3 m/0.4 m) were carried out to study the radiation characteristics of transformer oil jet fire. The flame combustion characteristics such as the fire plume temperature, mass loss and radiant heat flux were measured and analyzed. The experimental results showed that: The shape of the transformer oil jet fire was approximately cylindrical. The radiant heat flux increased exponentially with the increased of flame height. And radiant heat flux decreased exponentially as the horizontal distance increased. The multi-point source model and the line source model performed well in the prediction of the fire radiant heat flux of the transformer oil jet. As the Froude number increased, the radiation fraction change could be divided into two stages. In the first stage, the radiation fraction maintained almost constant. In the second stage, the radiation fraction dropped significantly. The research results provided valuable data support for the fire protection design of substation equipment. In addition, it could effectively improve the fire prevention and control ability of substation personnel.

The Influence of Nanoparticles on Fire Retardancy of Pedunculate Oak Wood.

Traditional flame retardants often contain halogens and produce toxic gases when burned. Hence, in this study, low-cost, environmentally friendly compounds that act as fire retardants are investigated. These materials often contain nanoparticles, from which TiO2 and SiO2 are the most promising. In this work, pedunculate oak wood specimens were modified with sodium silicate (Na2SiO3, i.e., water glass) and TiO2, SiO2, and ZnO nanoparticles using the vacuum-pressure technique. Changes in the samples and fire characteristics of modified wood were studied via thermal analysis (TA), infrared spectroscopy (FTIR), and scanning electron microscopy, coupled with energy-dispersive X-ray spectroscopy (SEM-EDX). The results of TA showed the most significant wood decomposition at a temperature of 350 °C, with a non-significant influence of the nanoparticles. A dominant effect of sodium silicate was observed in the main weight-loss step, resulting in a drop in decomposition temperature within the temperature range of 36–44 °C. More intensive decomposition of wood treated with water glass and nanoparticles led to a faster release of non-combustible gases, which slowed down the combustion process. The results demonstrated that wood modifications using sodium silicate and nanoparticle systems have potentially enhanced flame retardant properties.

Investigation of Forest Fire Activity Changes Over the Central India Domain Using Satellite Observations During 2001-2020.

Recurrent and large forest fires negatively impact ecosystem, air quality, and human health. Moderate Resolution Imaging Spectroradiometer fire product is used to identify forest fires over central India domain, an extremely fire prone region. The study finds that from 2001 to 2020, ∼70% of yearly forest fires over the region occurred during March (1,857.5 counts/month) and April (922.8 counts/month). Some years such as 2009, 2012, and 2017 show anomalously high forest fires. The role of persistent warmer temperatures and multiple climate extremes in increasing forest fire activity over central India is comprehensively investigated. Warmer period from 2006 to 2020 showed doubling and tripling of forest fire activity during forest fire (February–June; FMAMJ) and non‐fire (July–January; JASONDJ) seasons, respectively. From 2015 JASONDJ to 2018 FMAMJ, central India experienced a severe heatwave, a rare drought and an extremely strong El Niño, the combined effect of which is linked to increased forest fires. Further, the study assesses quinquennial spatiotemporal changes in forest fire characteristics such as fire count density and average fire intensity. Deciduous forests of Jagdalpur‐Gadchiroli Range and Indravati National Park in Chhattisgarh state are particularly fire prone (>61 fire counts/grid) during FMAMJ and many forest fires are of high intensity (>45 MW). Statistical associations link high near surface air temperature and low precipitation during FMAMJ to significantly high soil temperature, low soil moisture content, low evapotranspiration and low normalized difference vegetation index. This creates a significantly drier environment, conducive for high forest fire activity in the region.

Understanding fire regimes in Europe

Wildland fire effects are strongly associated with fire regime characteristics. Here, we developed the first European pyrogeography based on different fire regime components to better understand fire regimes across the continent. We identified four large-scale pyroregions: a non-fire-prone (NFP) pyroregion featuring nominal fire activity across central and northern Europe; a cool-season fire (CSF) pyroregion scattered throughout Europe; a fire-prone (FP) pyroregion extending mostly across southern Europe; and a highly fire-prone (HFP) pyroregion spanning across northern Portugal, Sicily, and western Balkans. Land cover analysis indicates that pyroregions were first shaped by vegetation and then by anthropogenic factors. On interannual timescales the spatial extent of pyroregions was found to vary, with NFP showing more stability. Interannual correlations between climate and burned area, fire frequency, and the length of fire period exhibited distinct patterns, strengthening in fire-prone pyroregions (FP and HFP) and weakening in NFP and CSF. Proportion of cool-season fires and large fires were related to fuel accumulation in fire-prone pyroregions. Overall, our findings indicate that such a pyrogeography should allow a more accurate estimate of the effects of climate on fire regimes while providing an appropriate framework to better understand fire in Europe.

Numerical Analysis of Smoke Behavior and Detection of Solid Combustible Fire Developed in Manned Exploration Module Based on Exploration Gravity

A fire during manned space exploration can cause serious casualties and disrupt the mission if the initial response is delayed. Therefore, measurement technology that can detect fire in the early stage of ignition is important. There have been a number of works that investigate the smoke behaviors in microgravity as the foundation for a reliable method for sensing a fire during spaceflight. For space missions to the outer planets, however, a strategy of detecting smoke as an indicator of fire should be adjusted to cover the fire scenario that can be greatly affected by changes in gravity (microgravity, lunar, Mars, and Earth gravity). Therefore, as a preliminary study on fire detectors of the manned pressurized module, the present study examined the smoke particle behavior and detection characteristics with respect to changes in gravity using numerical analysis. In particular, the effects of the combination of buoyancy and ventilation flow on the smoke particle movement pattern was investigated to further improve the understanding of the fire detection characteristics of the smoke detector, assuming that a fire occurred in different gravity environments inside the pressurized module. To this end, we modeled the internal shape of Destiny and performed a series of numerical analysis using the Fire Dynamics Simulator (FDS). The findings of this study can provide basic data for the design of a fire detection system for manned space exploration modules.

Experimental Research on the Combustion Characteristics of Transformer Oil Jet Fires in Oil-Filled Equipment under Heat.

Under the action of heat, the jet fire of oil-filled equipment in substations produces intense heat radiation and flame impact, causing serious harm to the personnel and equipment. Therefore, this paper has carried out a series of oil-filled equipment transformer oil jet fire experiments with different nozzle diameters to study the characteristics of transformer oil jet flame combustion. The experiment measured the mass loss rate, axial centerline temperature of the fire plume, and radiant heat flux and processed the flame visualization image. The results show that the combustion process of the transformer oil jet fire can be divided into three stages. The functional relationship between the flame height and mass flow and the functional relationship between the flame temperature and axial height are derived. A prediction model of the radiant heat flux of the transformer oil jet fire for the oil-filled equipment of the substation was established. The research results are of great significance for improving the fire protection design of substations and improving fire management and control capabilities.

Influence of the train running on the fire smoke spread characteristics in the rescue station

Rescue station is an important part of the extra-long railway tunnel, which can provide smoke-free refuge for evacuated passengers. For the fire research of the rescue station, the influence of the burning train running on the smoke spread characteristics has not been considered in the previous studies. In this work, the influence of the train running on the fire smoke spread characteristics in the rescue station was investigated using the numerical method, and the accuracy of the numerical methodology was confirmed by the 1:20 scale model experiment. Then, the influence of the burning train running on the temperature and visibility distribution in the rescue station was analysed by dynamic and static simulation. The results demonstrate that the temperature and soot density of the smoke are low when the burning train was running in the tunnel, which makes fire detection very difficult. For the smoke spread characteristics of the rescue station, the main impact of the burning train running is visibility, and the influence time is 30 s when the heat release rate of the fire source was 15 MW. For dynamic simulation, when the burning train stops at the rescue station, the maximum heat transfer power between the smoke at the top of the tunnel and the concrete lining is 1.51 MW, accounting for 10.1% of the heat release rate of the fire source.

Pressure stress modeling on expanded polystyrene materials using genetic programming

In the production of expanded polystyrene, the standards are very high in terms of thermal, fire, dimensional, and mechanical characteristics, because each of the characteristics is a condition for achieving quality that allows competitiveness in the market. To ensure high-quality products, it is necessary to achieve optimal performance and product quality through carefully adjusted input parameters of production. Since the production of expanded polystyrene is specific in several ways, an experimental study was conducted in which the basic parameters affecting product quality were detected and through which a series of experiments were performed to prove product quality. Experimental research for this work was conducted on three types of expanded polystyrene samples whose purpose is to insulate floors exposed to pressure. The samples were made of the same material of different densities and aging times for which the pressure stress at a deformation of 10% was tested. After the experimental phase, the modeling of the output parameters was performed. Modeling involved the development of a model that describes a given problem and the obtained modeled values were analyzed and compared with the experimental one. The modeling method used genetic programming using the GPdotNET software package. The goal of modeling with the GpdotNET tool is to obtain a realistic model that would give the value of the compression stress at a deformation of 10% as an output variable in materials made of expanded polystyrene.