Firing Time Research Articles

Investigation on Effects and Properties of Concrete Structure after Exposed to Fire

Abstract: The integrity and strength of the materials used in reinforced concrete structures are highly influenced by their exposure environment. Exposing the building materials to high temperature changes their performance. The change in the performance is a result of the change in the material properties. When subjecting a building material to fire, the occurring damage depends on the severity of the fire in terms ofthe fire temperature and time of exposure. This study investigates the effects of fireexposure on the set of RC beams. Through controlled experiments, varyingtemperatures from 3000C to 7000C areapplied to RC beams, analyzing changes in compressive strength, spalling, andmicrostructure by using rebound hammer,UPV meter and applying two-point loading in UTM. Results indicate a significantreduction in compressive strength with increasing fire temperature, attributed to thermal degradation of cement paste and aggregate. Additionally, changes inmicrostructure, such as pore structure alterations and formation of cracks, are observed. Also, few of RC beams were strengthened using GFRP sheets as a U- shaped wrapping to entire beam and U- shaped wrapping at certain intervals. The strengthened specimens are again tested in UTM for two-point loading, the results of the tests showed the feasibility of rehabilitating RC beams exposed to fire using GFRP plates.U-shaped wrapping to entire beam showed the good performance

Containment and suppression of compartment fires using specialized liquid compositions

Experimental research findings are reported on the characteristics of physicochemical processes at different stages of fire development and suppression. Fires involving solid materials like wood, cardboard and linoleum were investigated. The minimum necessary and sufficient volumes of firefighting liquid (water with different additives, e.g., a foaming agent, bentonite, bischofite, etc.) and their spraying times were identified. Differences in spraying characteristics (droplet velocities, sizes and concentration) were recorded. A relationship between the spraying characteristics of fire extinguishing agents and efficiency of fire suppression was established. Correlations were identified between the operational characteristics of fire detectors during fire suppression involving several fire extinguishing agents. The most efficient compositions in terms of fire suppression time and extinguishing agent consumption were found for typical indoor combustible materials. Mathematical equations were derived to predict the key characteristics of fire suppression.

Bioinspired on-off switchable multi-level responsiveness for ultralong fire-warning, super-sensitive solvent/humidity and light-driven behaviors

The prospects of endowing the omnipresent hazardous substances with sensitive, safe, and stable life-like behaviors poses significant for the development of on–off switchable smart materials. Herewith, based on material-structural synergistic design, a multi-level responsiveness smart structures (VBGO) inspired by phospholipid biomolecules is self-assembled through asymmetric swelling and smart supramolecular nano-structures. Due to the outstanding sensitive of fire-warning nano-hybrid of functionalized cyclodextrin-graphene and highly stable substrate of vermiculite, the designed VBGO exhibits the high-sensitively fire alarm time (only 0.17 s) and super-along sustained fire alarm time (up to 249 s). Moreover, the VBGO displays significant increment in thermal stability and film-forming properties. Besides, given the asymmetrical and self-assembled smart structures, the VBGO exhibits the unique fast responses in their surrounding environments like fire, heat, light, humidity, and solvent vapor. Additionally, the on–off switchable mechanisms of fire-warning responsiveness, solvent-/humidity-/light-driven, shape memory and environmental awareness are presented systematically. This work introduces a sensitive, safe, and stable approach to designing multi-level responsive smart materials by modifying fire-warning bioinspired structures.

Влияние режима пожара на огнестойкость несущих строительных конструкций машинных залов ГРЭС

Machine rooms of a state district power plant (GRES) are sizeable. Heat impact on the structures of the building in the case of a real fire can significantly differ from the impact in the case of a standard fire. Therefore, the calculation of fire resistance of building structures should be conducted not only in conditions of a standard fire but of a real fire as well. The objective of the study is the theoretical evaluation of the actual limits of fire resistance of load-bearing building structures of the machine room of the main building of the Nizhneturinskaya GRES in conditions of standard and real fire regimes. Numerical experiments to calculate the heating of load-bearing building structures in the case of a standard fire and the case of the most hazardous scenario of the real fire development have been conducted in the framework of the study. A field 3-dimensional model to calculate fire hazardous factors and a non-stationary thermal conductivity equation have been applied. The obtained results have been analyzed. The field model adapted to the space-planning solutions of the machine room has been described. The most hazardous scenario of the development of real fire in case of combustion of the turbine oil spill in the sector of the machine room with the lowest height of ceiling has been chosen. The temperature fields in the gaseous environment of the machine room at different moments are presented. It has been detected that the heating of reinforced concrete structures of the machine room ceiling is significantly uneven due to the 3-dimensional gas dynamic pattern of fire. Dependencies of temperatures of the frame of reinforced concrete load-bearing structures of the ceiling on the time of standard and real fires in the most heated section of the ceiling have been obtained. It has been determined that the maximum temperature of the frame in the case of the standard fire is lower than in the case of real fire. Due to the features of the 3-dimensional thermal gas dynamic pattern of fire in machine rooms of the GRES, the fire resistance of load-bearing building structures in these premises must be determined in both conditions of standard fire and real fire, considering the most hazardous scenario of its development.

Design of fluorine-free foam extinguishing agent with high surface activity, foam stability and pool fire suppression by optimization of surfactant composition and foam system

To meet the environmental requirement of foam extinguishing agent, a novel fluorine-free surfactant named amino-terminated polyether modified silicone (ATPMS) was successfully synthesized, and then in combination with hydrocarbon surfactant prepared fluorine-free foam extinguishing agent. The study carefully investigated surface tension, foamability, foam stability and fire extinguishing performance of fluorine-free foam extinguishing agent. The results indicate that ATPMS has a low surface tension of 21.17 mN/m, which combined with hydrocarbon surfactant at the mass concentration ratio of 1:1 imparts high surface activity. The sodium lauryl ether sulfate (AES)/ATPMS system owes the optimal comprehensive performance with an initial foam height value of 85.8 mm, a surface tension value of 24.76 mN/m and a foam stability value (the ratio of foam height between initial foam and five-minute foam) of 64.0 % at critical micelle concentration (CMC), respectively. Fire suppression test shows that the obtained fluorine-free foam extinguishing agent is effective in fighting diesel pool fires. The firefighting efficiency of foam agent links to the mixing chamber structure of compressed air foam fire extinguishing system (CAFS). When the mixing chamber of CAFS has a recurrent segment length of 50 mm and the filled particle size of 10 mm, the firefighting efficiency of fluorine-free foam extinguishing agent is optimal with a fire extinguishing time of 33 s and a temperature drop rate of 6.49 °C/s.

Phosphorus-nitrogen synergistic transparent UV-curable coatings to enhance the flame retardancy of polycarbonate

There is an urgent demand for flame retardant treatment of polycarbonate (PC) with as little adverse impact on the inherent advantages of PC as possible, especially the high transparency. Herein, a flame-retardant coating with high transparency was successfully prepared on PC via a two-step ultraviolet-curing (UV-curing) process with tri(acryloyloxyethyl) phosphate and melamine acrylate resin. All the coated PC composites showed high transparency and excellent pencil hardness levels (6H). The coupling effect of the combustion behaviours of the UV-cured coatings and the PC substrates was particularly investigated to give insight into a holistic picture of the combustion of the coated composite systems. Specifically, all the composite UV-cured coating samples (T2M1, T1M1 and T1M2) formed highly expanded char with honeycomb-like inner structure due to the phosphorus-nitrogen synergistic effects, which could efficiently suppress mass and heat transfer, thereby protecting the PC substrates from the harsh conditions of high temperature and realizing significantly enhanced flame retardancy of the PC samples. Improving the thermal and mechanical stabilities of the intumescent carbon layers may be a practical strategy to achieve further improved flame retardant capabilities of the PC samples. Additionally, the PC-T2M1 composite exhibited the optimal flame retardant effect, realizing significantly suppressed heat release in the cone calorimeter tests, reaching UL94 V-0 rating and showing long fire resistance time thanks to the intumescent char. The UV-cured coating method introduced in this work had great potential in spawning new strategies for designing advanced flame retardant coatings for polymer substrates.

Identification of primary input parameters affecting evacuation in ventilated main control room through CFAST simulations and application of a machine learning algorithm to replace CFAST model

Accurately predicting evacuation time in a ventilated main control room (MCR) during fire emergencies is crucial for ensuring the safety of personnel at nuclear power plants. This study proposes to use neural networks alongside consolidated fire and smoke transport (CFAST) simulations to serve as a surrogate model for physics-based simulation tools. Our neural networks can promptly predict the evacuation time in MCRs, proving to be a valuable asset in fire emergencies and eliminating the need for time-consuming rollouts of the CFAST simulations. The CFAST model simulates fire and evacuation scenarios in a ventilated MCR with variations in input parameters such as door conditions, ventilation flow rate, leakage area, and fire propagation time. Target output parameters, such as hot gas layer temperature (HGLT), heat flux (HF), and optical density (OD), are used alongside standardized evacuation variables to train a machine learning model for predicting evacuation time. The findings suggest that high ventilation flow rates help to dilute smoke and discharge hot gas, leading to lower target output parameters and quicker evacuation. Standardized evacuation variables exceed the required abandonment criteria for all door conditions, indicating the importance of proper evacuation procedures. The results show that neural networks can generate evacuation times close to those obtained from CFAST simulations.

Experimental investigation on the post-fire mechanical properties and charring rate of inorganic-bonded bamboo composite exposed to fire

The fire resistance remains a challenging topic for engineered wood and bamboo structures due to the combustibility of wood and bamboo and the usage of organic adhesives, which are temperature-sensitive substance in fire. As an alternative solution, this paper investigated a novel bamboo-based composite prepared with magnesium oxysulfide inorganic adhesive (inorganic-bonded bamboo composite, InorgBam), and the fire tests were carried out to investigate the post-fire mechanical properties and charring behavior of InorgBam. The reduction effect of fire exposure on compressive or tensile strength parallel-to-grain was experimentally studied. The effects of fire exposure surface numbers, grain direction, geometric dimension and exposure time on charring rate were discussed. Results showed that the InorgBam can be maintained the post-fire strength under compressive or tensile loads parallel to grain without significant degradation when the exposure temperature below 250 °C. The temperature of the char front was determined to be approximate 350°C by using an interpolation method. The charring rate was mainly dominated by the exposure time and decreases nonlinearly with the increase of exposure time, and the charring rate with multi-sided fire exposure was approximately 1.1 times of that exposed to one-sided fire. Finally, a nonlinear model was proposed to predict the charring rate of InorgBam material, which provides a basic reference for understanding the fire resistance of InorgBam material exposed to fire.

Enhancing the vaporization and secondary atomization of two-liquid droplets for fire suppression

Large-scale fires of various origins are most often contained and suppressed using fine water spray systems with a droplet size of 50–300 μm. Enhancing the extinguishing performance of these systems is an urgent task as this will reduce the amount of irreversible damage fires cause to forests, buildings, and compartments. Finer droplet size of the extinguishing liquid sprayed directly in the combustion zone prevents droplet entrainment, thus increasing the firefighting efficiency and reducing the extinguishing liquid consumption. However, too little is still known about alternative ways to intensify the vaporization and secondary atomization of fine water sprays in order to disrupt the chemical reactions responsible for combustion. Experimental findings on enhancing the secondary atomization and phase change of sprayed water with added vegetable oils for fire suppression are presented. Experiments on water droplets with sunflower, rapeseed, and tall oils were performed in the ethanol burner flame zone. The radii of two-liquid droplets were 0.85 ± 0.05 mm. The concentration of explosion-triggering additives to water was constant at 10 ± 2 vol.% in all the experiments. The addition of 10 vol.% rapeseed oil to water allows one to reduce the local gas temperature around the droplet up to 250 K in case of micro-explosion of an isolated droplet and up to 450 K in case of micro-explosion of a group of droplets. The experimental findings were processed to obtain approximations of the relationships established in the experiments: micro-explosion delay times, droplet lifetimes, and normalized evaporation surface area after breakup. A physical model is presented describing the processes involved in the experiments. An additional series of experiments involved suppressing a laboratory-scale wood crib fire using water and water/rapeseed oil emulsion to compare the fire suppression times and the extinguishing liquid consumption in both cases. The suppression times and the extinguishing liquid consumption were on average 15% lower when using a water/rapeseed oil emulsion compared with pure water. Practical recommendations are given on how to provide the intense disruption of extinguishing liquids with added vegetable oils to accelerate fire suppression. Two-liquid droplets exploding in the flame zone are established as a possible alternative to water capsules, extinguishing missiles, and cryogenic technologies for suppressing large-scale fires.

Bark thickness and related parameters of tree species along an elevation transect leading to treeline in Central Himalaya.

Since treelines are generally fire-free, the trees growing there are expected to have thin bark, unless adaptation to other factors than fire results in the selection of a thick bark. Related to this is also higher proportional investment in inner bark in such an environment of infrequent fire. This study has considered stem bark thickness both in absolute and relative terms and also in the frame of the composition of outer and inner bark components of 20 tree species along an elevation transect (2100-3300m) in high ranges of the Central Himalaya leading to treelines. The study species varied from 2.1 to 16.2mm for total bark thickness and from 1.2 to 18.85% for relative bark thickness. The average absolute total bark thickness across the tree species decreased with elevation from forest to treeline, both when trees of all diameters (10.2 ± 0.84mm for forest and 6.9 ± 1.79mm for treeline) and those of the same stem diameter range (18-20m) were compared (9.10 ± 1.30mm for forest species and 6.38 ± 1.31mm for treeline species). Nevertheless, the treeline bark thickness was similar to those of several forest communities considered to have comparatively thick bark. Like many other biological structures, bark carries out multiple functions; therefore, its thickness could be affected by more than one environmental factor. We suggest that the requirement of mechanical resistance to the snowfall, rainstorms, wind and adaptation to a high sunlight and UV radiations or storage of water, and non-structural carbohydrates could affect total, outer and inner bark thickness. Studies on these aspects in similar ecosystems may help understand the multi-functional attributes of the bark. For trees of comparable sizes (trees with 18-20cm diameter at breast height) treeline species also had lower relative bark thickness (< 6%) than trees of forest below it (> 7%). The median proportion of inner bark of the total bark (70.5%) for our 20 species was more than that for savannas (~ 50%), exposed to frequent fire regime and similar to those of in cool sclerophyllous forests and temperate rain forests where fire return time is > 100years. However, it was lower than the inner bark proportion reported for tropical rain forests. To conclude, in spite of a fire-free environment, the Himalayan treeline and adjoining forest species show mixed bark characters.

Spike sorting with Kilosort4.

Spike sorting is the computational process of extracting the firing times of single neurons from recordings of local electrical fields. This is an important but hard problem in neuroscience, made complicated by the nonstationarity of the recordings and the dense overlap in electrical fields between nearby neurons. To address the spike-sorting problem, we have been openly developing the Kilosort framework. Here we describe the various algorithmic steps introduced in different versions of Kilosort. We also report the development of Kilosort4, a version with substantially improved performance due to clustering algorithms inspired by graph-based approaches. To test the performance of Kilosort, we developed a realistic simulation framework that uses densely sampled electrical fields from real experiments to generate nonstationary spike waveforms and realistic noise. We found that nearly all versions of Kilosort outperformed other algorithms on a variety of simulated conditions and that Kilosort4 performed best in all cases, correctly identifying even neurons with low amplitudes and small spatial extents in high drift conditions.

Simulation of the Jet Fire Using Atmospheric Dispersion Modeling (ALOHA): A Case Study of Natural Gas Pipeline in Istanbul, Türkiye

Natural gas is known as a widely used energy source in residential, business and industrial areas. During the transportation of natural gas by pipelines, accidents occur due to various reasons, which can also lead to gas output. These accidents are events that have the potential to pose important risks in terms of life and property safety, particularly in urban areas and surrounding of pipeline routings. In this study, accident scenarios were generated based on a natural gas distribution pipeline fire that occurred in Istanbul (NW Türkiye) on 28 April 2020 and the impact areas of the jet fire were calculated using the ALOHA program. The effects of source release factors (i.e., pipe length and diameter) and atmospheric conditions (i.e., wind speed, cloud cover, air temperature and relative humidity) on the thermal radiation threat distances associated with jet fire were calculated for the current and worst scenarios. As a result, it was found that pipe length and diameter have a significant effect on threat distances. In addition to the role of the synoptic circulation mechanism on the jet fire for the selected episodic event (position of low/high pressure centers), local atmospheric conditions also have an effect on the threat distance. From the modeling analysis, significant impact of wind speed, air temperature and relative humidity values on the threat distances were found. In the worst scenario, if there were strong northeasterly winds reaching 30.9 m per hour at the time of the jet fire, the threat distances would have been 21 m (red), 28 m (orange) and 42 m (yellow). This case shows that if a natural gas jet fire occurs under the influence of strong northeasterly winds (passing over the Black Sea without encountering any topographic obstacles), poisonous gas will be transported to long distances in a short time and will negatively affect social life and economy.

ASSESSMENT OF THE EFFICIENCY OF FIRE EXTINGUISHING SYSTEMS

As previously shown, many indicators characterise the quality of fire extinguishing systems. The most common quality indicator is fire extinguishing time. For fire extinguishing systems focused on extinguishing Class B fires using sprayed water, the authors have constructed a transcendental equation, the root of which is the fire extinguishing time. We derived the equation provided that the intensity of the sprayed water supply to the combustion centre to be described by the Heaviside function. The dynamic properties of fire are defined using the integral Laplace transform. We obtained the functional dependence of class B fire extinguishing time on fire parameters and showed that this time does not exceed a tenth of the constant fire time. In the first approximation, the inertial properties of the fire extinguishing system can be taken into account by the transfer function of an aperiodic link with a generalised time constant. For this case, we constructed a transcendental equation that determines the fire extinguishing time by the inertial fire extinguishing system. We note that, according to inertial properties, fire extinguishing systems fall into three classes. For each of the three classes, estimates of the extinguishing time of a class B fire were obtained, depending on the dynamic properties of this fire. The results show that this time can change several times. The authors have introduced the criterion for the efficiency of fire extinguishing systems, which characterises the degree of approximation of the speed of the fire extinguishing system to the maximum possible value. This criterion also indicates how much it is necessary to increase the extinguishing agent mass supplied per unit area of the fire relative to the extinguishing agent mass supplied in leaps per unit area of the fire, provided that the extinguishing times are the same. We obtained estimates of the effectiveness of fire extinguishing systems using this criterion. Furthermore, we provided recommendations on the use of the efficiency criterion. Keywords: fire extinguishing system, extinguishing time, efficiency criterion.

Temporal–Spatial Characteristics and Influencing Factors of Forest Fires in the Tropic of Cancer (Yunnan Section)

Forest fires often cause many casualties and property losses, and it is important to explore the time and space laws of forest fires and the influencing factors. The present study used the cities (prefectures) crossed by the Tropic of Cancer (Yunnan section) as the study area. Based on burned land data, a combination of natural factors, such as climate, topography, vegetation, and human activities, such as distance from settlements and population density, a binary logistic regression model, and a boosted regression tree model, were used to analyze the temporal–spatial characteristics and influencing factors of forest fires in 2000 to 2020. The following results were obtained: (1) During 2000–2020, the overall forest fire area in the study area showed a trend of fluctuating decline. The high incidence period of forest fires occurred in 2010. After 2010, the forest fire area in the study area was greatly reduced. (2) The forest fire area in the study area was greater in the east and less in the west. The forest fire areas in Wenshan Prefecture and Honghe Prefecture in the east were larger, accounting for 68%, and the forest fire areas in Pu’er City, Lincang City, and Yuxi City in the west were smaller, accounting for only 32%. (3) The contribution rate of the average precipitation and average temperature factors ranked in the top two in the two driving force analysis models, which indicated that precipitation and temperature had a significant effect on the incidence of forest fires in the study area.

Experimental Investigation of the Post-Fire Impact Resistance and Energy-Absorbing Characteristics of Polyethylene Cored Lightweight Metal Sandwich Panels

ABSTRACT To investigate the effect of different fire loading time and stitching methods on the post-fire impact resistance of the polyethylene cored sandwich panels, quasi-static perforation, and low-velocity impact tests were conducted after real fire tests. The temperature distribution, deformation, failure behavior, load-carrying capacity, and energy absorption capacity of the panels were explored and compared. The effects of key parameters such as the stitching method, fire time, and impact energy on the load versus displacement curves and energy absorption were discussed in detail. In addition, a theoretical model was developed to predict the plastic strain of sandwich panels under the low-velocity impact, and the results showed that when the height of the falling hammer is constant, the depression value of the upper surface center point ( δ 1 ) and the depression value of the lower surface center point ( δ 2 ) are both linearly related to 1 ( T m − T r ) n − T − T r n .

Experimental study and theoretical analysis of fire resistance properties of prestressed glued laminated timber beams

The addition of prestressing not only improves the force resistance of glulam beams, but also provides a potential solution to improve their fire resistance. An in-depth study of the fire behavior of prestressed glulam beams (PGBs) under fire and the force behavior after fire is essential for their fire resistance design and evaluation. In this paper, fire tests and post-fire four-point bending experiments were conducted on the PGBs aiming to investigate the thermal response of the PGBs as well as their force resistance after fire. The results showed that fire significantly affected the mechanical properties of the PGBs, not only reducing the prestressing force during the fire, but also decreasing the residual load carrying capacity after the fire. After 60 min of standard fire exposure, the prestress and load capacity of the PGBs decreased by 10 % and 33.33 %, respectively. Increasing either prestress or reinforcement ratio can effectively improve the resistance performance of the PGBs after fire. In the same fire action time, if the prestress was increased by 59.46 % or the reinforcement ratio was increased by 0.53 %, the residual ultimate load capacity of the PGBs was increased by 17.14 % and 22.19 %, respectively. The study also indicates that fully utilizing the synergistic effect of prestressing and reinforcement ratio enhancement can significantly improve the overall performance of the PGBs. In addition, a theoretical calculation model is proposed to accurately predict the residual flexural capacity of the PGBs after fire, which provides a theoretical support for the fire-resistant design of the PGBs before fire and the assessment of residual load capacity after fire.

Sensitivity of Simulated Fire‐Generated Circulations to Fuel Characteristics During Large Wildfires

AbstractCoupled fire‐atmosphere models often struggle to simulate important fire processes like fire generated flows, deep flaming fronts, extreme updrafts, and stratospheric smoke injection during large wildfires. This study uses the coupled fire‐atmosphere model, WRF‐Fire, to examine the sensitivities of some of these phenomena to the modeled total fuel load and its consumption. Specifically, the 2020 Bear Fire and 2021 Caldor Fire in California's Sierra Nevada are simulated using three fuel loading scenarios (1X, 4X, and 8X LANDFIRE derived surface fuel), while controlling the fire rate of spread using observations. This approach helps isolate the fuel loading and consumption needed to produce fire‐generated winds and plume rise comparable to radar observations of these events. Increasing fuel loads and corresponding fire residence time in WRF‐Fire leads to deep plumes in excess of 10 km, strong vertical velocities of 40–45 m s−1, and combustion fronts several kilometers in width (in the along wind direction). These results indicate that LANDFIRE‐based surface fuel loads in WRF‐Fire likely under‐represent fuel loading, having significant implications for simulating landscape‐scale wildfire processes, associated impacts on spread, and fire‐atmosphere feedbacks.

Synthesis of magnesium hydroxide powder and dry powders for application in extinguishing petroleum fires

AbstractFire extinguishing agents are an important factor in the fight against fires. In this study, a new composite powder (CSPMS) was synthesized and used to extinguish fires caused by petroleum products. SiO2 nanoparticles, Mg(OH)2 nanoparticles, and nanocomposites of NH4H2PO4/chitosan (CSP) were combined to generate CSPMS powder. The structure and morphology of the material were characterized using methods such as XRD, SEM, FTIR, etc. The results showed that the synthesized Mg(OH)2 nanoparticle size ranged from 20 to 30 nm, and the NH4H2PO4 nanoparticle size ranged from 800 to 900 nm on the chitosan surface. The CSPMS material had particle sizes ranging from 2 to 3 µm, with a uniform distribution of SiO2 nanoparticles (50–100 nm) and Mg(OH)2 nanoparticles on the surface. The powdered materials were applied to extinguish gasoline and oil fires. CSPMS sample demonstrated the best fire extinguishing time and powder consumption (5.8 s and 12.2 g, respectively) and CO emission below the threshold of 400 ppm. Small‐scale fire extinguishing tests showed that CSPMS powder had better fire extinguishing capability, cooling time, and CO gas adsorption ability compared to commercial fire extinguishing powder.

Changes in bryophyte functional composition during post-fire succession

Climate and land-use changes are altering fire regimes in many regions around the world. To date, most studies have focused on the effects of altered fire regimes on woody and herbaceous communities, while the mechanisms driving post-fire bryophyte succession remain poorly understood, particularly in Mediterranean-type ecosystems. Here, we examined changes in bryophyte functional composition along a post-fire chronosequence (ranging from 1 to 20+ years) in Pyrenean oak woodlands (northeastern Portugal). To do so, we defined bryophyte functional groups based on seven morphological, reproductive, and life history traits. Then, we fitted linear and structural equation models to disentangle the direct and indirect effects of fire (time since fire and fire intensity), vegetation structure, climate, topography, and edaphic conditions on the abundance of each group. We identified two main functional groups: early colonizers (species with traits associated with strong colonization ability and desiccation tolerance) and perennial stayers (species with high competitive ability, i.e., large perennial mosses). Overall, the abundance of early colonizer species decreased with time since fire and increased with fire intensity, while the opposite was observed for perennial stayers. Thus, successional dynamics reflected a trade-off between species' competitive and colonization abilities, highlighting the role of biotic interactions later in succession. Patterns of functional composition were also consistent with changes in environmental conditions during succession, suggesting that species may experience stressful conditions (i.e., high radiation and low water availability) in early stages of post-fire succession. Our results also indicate that increased fire intensity may alter successional trajectories, leading to long-term changes in bryophyte communities. By understanding the response of bryophyte communities to fire, we were able to identify species with potential use as soil restoration materials.

Experimental and Numerical Studies on the Efficacy of Water Mist to Suppress Hydrocarbon Fires in Enclosures

Fire is one of the most undesirable events onboard a ship. The engine room is one of the most critical spaces in the ship in terms of fire protection, as it includes machinery, hydrocarbon fuel systems, and different electrical equipment. With the phasing out of Halon 1301 as a fire suppressant over recent decades, there has been an intensive effort to explore the efficacy of water-mist spray in mitigating fires within machinery spaces. This exploration entails a comprehensive investigation through experimental and simulation studies aimed at identifying suppression mechanisms and evaluating their effectiveness. While experimental setups typically encompass measurements of gas temperature, thermal radiation heat flux, oxygen concentration, and fire extinction time, limited attention has been paid to quantifying the heat release rate (HRR), a crucial indicator of fire magnitude. Furthermore, research into shielded fire scenarios remains sparse, despite their significance in maritime fire dynamics. Addressing shielded fires with water mist proves particularly challenging due to the potential obstruction impeding the direct interaction between the fire source and the water droplets. In the existing literature, most of the computational fluid dynamics (CFD) modelling of fires and suppression was performed using a Fire Dynamics Simulator (FDS). Alternate studies were performed using FireFOAM. and very few employed FLUENT and other analogous software codes. In the majority of reported computational studies, the determination of HRR was typically relied upon for its calculation derived from the measured data of fuel mass loss rate. Moreover, certain studies were undertaken for numerical simulations without conducting thorough model validation, either by omitting validation altogether or solely validating against dry fire experiments (i.e., without water-mist suppression). This critical review of the literature has identified several notable research gaps in the context of extinguishing hydrocarbon fires utilising water-mist spray, warranting further investigations. Additionally, this review paper highlights recent advancements in both experimental and numerical investigations pertaining to the efficacy of water-mist fire-suppression systems in enclosed spaces regarding hydrocarbon fires.