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Through a series of full-scale fire tests conducted in three different tunnels, the common characteristics of combustion and smoke temperature of double pool fires in actual operation tunnel environments are investigated. The evolution process of the coupling effects of shielding entrainment and thermal feedback enhancement is revealed. It is found that the ventilation state and the fire source spacing can alter the dominant relationship between the shielding entrainment effect and the thermal feedback enhancement effect, resulting in different evolution patterns of combustion characteristics and smoke flow patterns of double pool fires in tunnels. The heat release rate increases by 4 times when the double pool fire flames merge under the longitudinal ventilation compared with the double pool fire flames without fusion under the natural ventilation. The flame tilt angles of double pool fires were determined through the image processing method, and the prediction model of the flame inclination angle of downstream fire sources was established, considering fire source spacing. At the same time, the characteristic of temperature measured by Fiber Bragg Grating in double-source fire scenarios was investigated, developing a model to predict the longitudinal temperature rise distribution. It is found that the maximum temperature rise prediction model based on steady-state fire has poor applicability in the weak-plume fire scenario of full-scale tunnels. The analysis of the smoke flow patterns shows that the two-stage ventilation is more suitable for smoke control compared to full longitudinal ventilation in tunnel double-source fire accidents, especially for ensuring the safety of individuals trapped in the area between the two fire sources. • Full-scale double-source fire tests were carried out in three different tunnels. • The coupling effects of shielding entrainment and thermal feedback enhancement in tunnels are revealed. • A prediction model for flame tilt angle of downstream fire source is proposed. • The characteristic of FBG temperature of double-source fire is analyzed. • The two-stage ventilation is more suitable for smoke control in tunnel double-source fire accidents. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate experimentally the influence of fuel moisture content on the fire behaviour of Cistus monspeliensis , when exposed to a fire front spreading across a fuel bed. Shrubs of Cistus monspeliensis with leaf moisture contents ranging between 10 and 100 % were placed under a Large Scale Heat Release Calorimeter and a bed of wood wool was used before and under the branches to mimic an ignition from an underneath burning herbaceous layer. Mass loss, heat release rate (HRR) and total heat release (THR) were measured. The peak of HRR, the THR and the effective heat of combustion decreased linearly with the leaf moisture content. Two thresholds, characteristics of the fire behaviour of Cistus monspeliensis, were obtained. The ignition threshold, equals to 85 %, is the maximum leaf moisture content at which the cistus will ignite. The spreading threshold, equals to 55 %, is the maximum leaf moisture content at which the flame front will spread through the branches. • Shrubs can only be ignited by a surface fire for leaf moisture contents below 85 %. • If the leaf moisture content is below 55 %, the fire will spread throughout the crown. • Energy release during shrub burning decreases as leaf moisture increases. [ABSTRACT FROM AUTHOR]

A meta-analysis was conducted on 100 structural mass timber compartment fire experiments. The analysis investigated temperature, heat release rate, auto-extinction and delamination. Dissimilarities in the compartment geometry, ventilation, and exposed timber surfaces of these experiments could be accounted for using two parameters, α and %A O (applicable to near cubic, ventilation-controlled compartments) defined as the shape-modified ventilation factor and opening ratio. The correlation coefficient for the total heat release rate (HRR) with the area of timber for the large and medium scale data was 0.97 and 0.74, respectively. Similarly, the correlation of medium scale data for the contribution of timber to the heat release rate was 0.90. A statistical analysis revealed a higher probability for auto-extinction to occur for exposure levels below 20%. Above 20% exposure, the risk for sustained flaming and delamination increase substantially. Auto-extinction was shown to depend strongly on delamination, with a 93% probability of occurrence given no delamination. The use of PUR HBS adhesive was shown to cause delamination in 73% of the cases, with PUR HBX delaminating in 33% of cases. • Dissimilar test data can be correlated using compartment and ventilation factors. • Likelihood of sustained flaming substantially increases beyond 20 % exposed timber. • Sustained flaming is strongly influenced by the occurrence of delamination. [ABSTRACT FROM AUTHOR]

A reduced scale 1:8 double-deck tunnel model was built to study smoke control performance of a semi-transverse ventilation system using a branch pipe to connect the lower deck tunnel to the upper smoke duct. 41 experiments were conducted to analyze the effects of different activation modes of smoke vents, heat release rate (HRR), and exhaust smoke rates on smoke spread distance. An optimum smoke control mode was found by activating two vents near the fire source when the heat release rate was 44.19 kW (8 MW at full scale) and the fan's extraction rate was 0.66 m3/s (120 m3/s at full scale) using a branch pipe. Results showed that as HRRs rise, the smoke spread distance first increases and then remains constant. The ratio of the smoke spreading distance on the upstream side of the fire to the total smoke spreading distance was 0.4 in this experimental setup. Furthermore, fire smoke spread characteristics were quantified for a typical ventilation design. • The best smoke control is achieved by opening only two vents near the fire source. • The smoke spread distance increases with HRRs below 44.19 kW and then remains constant. • Decreasing the distance between exhaust vents can limit smoke spread distance. [ABSTRACT FROM AUTHOR]

This study experimentally investigates fire behaviors of double fires with asymmetric heat release rates in a naturally ventilated tunnel including flame merging and longitudinal ceiling gas temperature distribution. The comparison between double fires with symmetric and asymmetric heat release rates was also made. The results show that the flame merging possibility increases as the heat release rate on one side increases. The ratio of heat release rates between double fire sources still influences the flame merging possibility under a given total heat release rate. The ceiling gas temperature distribution is related to the flame merging state. As the fire separation distance increases from zero, the position of peak temperature is closer to the fire source with a larger heat release rate due to a smaller flame tilt angle. For scenarios with mean flame merged, the ceiling gas temperature distribution on both sides is equal. For scenarios with mean flame not merged, the ceiling gas temperature on the side with a larger heat release rate is much higher. Finally, different empirical models are established to predict the excess ceiling gas temperature attenuation, considering different flame merging states and smoke spread regions. • The flame merging behaviors of double fire with unequal heat release rates were studied. • The effect of flame merging on smoke temperature below the ceiling was revealed. • Models for estimating the smoke temperature at different flame merging stages were proposed. [ABSTRACT FROM AUTHOR]

Full-scale fire testing of battery electric (BEVs) and internal combustion engine (ICEVs) passenger vehicles has historically shown peak heat release rates (HRRs) ranging from 5–10 MW. However, the vehicles tested in these studies are smaller with less energy capacity than vehicles currently on the market. This paper presents a model to extrapolate data from full-scale vehicle fire tests to evaluate the fire hazard associated with larger passenger vehicles. The model is validated on 20 full-scale vehicle experiments in the public literature and is then used to develop conservatively bounding fire scenarios for vehicles representative of the current market environment. No significant difference was observed in the HRRs between the similarly sized ICEVs and BEVs in this work; however, the predicted HRRs for both vehicle types significantly exceeded existing design guidance. While the model may be shown to be overly conservative in future testing, it is validated using the data that currently exists, and points to an alarming trend in the fire protection industry, where the hazard posed by single passenger vehicles may exceed existing design guidance. • Developed an empirical model to create design fires for battery electric vehicles. • Validated model with existing full-scale datasets. • Evaluated the fire hazard posed by larger battery electric and internal combustion engine vehicles on the market. [ABSTRACT FROM AUTHOR]

Low pressure, medium pressure and high pressure water-based fire suppression systems were tested in a medium scale tunnel (scale 1:3). The primary objective was to investigate which of these systems are most effective in the suppression or control of different types of tunnel fires. The default low, medium and high pressure systems refer to full scale water flow rates of 10 mm/min, 6.8 mm/min and 3.7 mm/min, respectively. Some other water densities were also tested to investigate the effects, as well as different ventilation velocities and activation criteria. Several series of fire tests were conducted for different fire scenarios. The fire scenarios considered included idle wood pallet fires, loosely packed wood crib fires, loosely packed wood and plastic crib fires, and pool fires, with or without a top cover on the fuel load. Comparisons of the three default systems based on the three parameters: heat release rate, energy released and possibility of fire spread, show that the performance of the default low pressure system is usually the most effective based on the parameters studied. The default high pressure system usually yields results less effective in comparison to the default low pressure system. The performance of the default medium pressure system usually lies in between them. The high pressure system behaves very differently in comparison to the others, in terms of tunnel ventilation velocity, water density, operating pressure, and the presence of the top cover. [ABSTRACT FROM AUTHOR]

Accidental leakage of flammable gas with momentum emanating from pipeline cracks when met with an ignition can bring about turbulent diffusion flames known as jet fires. The jet fire geometry is a vital parameter in fire safety calculations and in the design of safe process facilities. The previous research confirms that the jet geometry is influenced by the shape of such cracks (shape of the source). This paper deals with the experimental evaluation of the geometry of a horizontally oriented, turbulent jet flame with 13 source shapes ranging from the conventional ones to the complex ones, such as a branched crack. The phenomenological constant in the implicit correlation suggested by Quintiere and Grove is correlated to the normalized form of hydraulic diameter. Based on this, a modified explicit correlation is proposed. The sensitivity of flame height and the transition behaviour of flame heights are represented with the modified heat release rate in terms of perimeter (Q p , *) and critical values of Q p *. The present study makes observations and offers conclusions in terms of hydraulic diameter and perimeter, which circumvent the dependency of the jet flame geometrical characteristics on source shape. [ABSTRACT FROM AUTHOR]

The purpose of the study was to investigate the effect of oxygen concentration on pool fire combustion in specific locations where oxygen concentrations exceed 21% due to oxygen leaks, such as rocket launch sites, aircraft, submarines, etc. The combustion characteristics of small-scale pool fires under high oxygen concentrations should be conducted by experimental and theoretical analysis. This study discussed the effects of high oxygen concentrations on heat release rate, burning rate, and combustion efficiency under Fire Propagation Apparatus (FPA) test conditions and measured the flame height and boiling mechanisms in a Semi-open Oxygen-adjustable Experimental Platform (SOEP). The results show that boiling combustion of small-scale pool fires is more intense, the burning rate and heat release rate in the boiling stage are significantly enhanced under high oxygen concentrations. Empirical models of flame height and heat feedback have been established. In conclusion, the hazards of oxygen-enriched fires were evaluated. This study provides foundational data and predictive models to mitigate the threats posed by oxygen-enriched pool fires in the process industry. • The combustion characteristics of liquid fuels were measured in increased oxygen concentration. • Theoretical models of mean burning rate and flame height were established. • The variation of heat feedback with oxygen concentration was summarized in small-scale pool fires. • The effect of oxygen concentration on fire hazards was measured and evaluated. • Obtained data and models can be applied in risk assessment of liquid fuel/O 2 coexisting scenarios. [ABSTRACT FROM AUTHOR]

This work presents a comprehensive study on the flammability of typical tropical broad-leaf forest litter using bench-scale cone calorimetry. For comparison, similar tests are conducted on native pine forest litter. The tests are carried out for the litter bed densities ranging from 25 to 75 kg/m3 in standard and perforated walled sample holders. Tests are also carried out on forest litter treated with fire retardant, Ammonium Poly Phosphate(APP). The broad-leaf tropical litter ignites earlier and burns longer than pine litter but with lower heat release rates. Smouldering combustion, which ensues after flaming combustion, is also longer for the tropical litter. The heat release rate decreases with increase in bed density; however, it increases especially at low litter bed densities, when sample holder walls are made porous. These effects are less drastic for the tropical litter. The heat release rate for tropical litter exhibits sporadic peaks not observed in pine litter. In contrast, forest litter treated with fire retardant has reduced flame duration in porous holders compared to tests in standard holders, and the heat release rate may be lower for high bed densities. Critical heat flux is higher for the untreated tropical litter, but with APP treatment, it is higher pine litter. [ABSTRACT FROM AUTHOR]

The flame-to-flame interaction in a dual-pool fire scenario is a crucial issue. However, current research on multiple fires in tunnels primarily focuses on scenarios where the fire sources are situated along the central axis of the tunnel. However, in real tunnel fires, the lateral positions of the fire sources are variable and unpredictable. Therefore, studying the flame behavior of two fire sources at different lateral positions within the tunnel is of significant importance in elucidating the interaction mechanisms between two fire sources inside the tunnel. In this investigation, a synergistic approach involving experimental inquiry and theoretical derivation was employed to systematically examine the phenomena of flame merging and tilting induced by two pool fires at diverse lateral positions within a naturally ventilated tunnel. The results indicate that flame entrainment is more likely to occur due to sidewall restrictions in tunnels, thereby increasing the probability of flame merging. A piecewise expression for determining the probability of flame merging from dual fire sources within tunnels was established. Furthermore, considering how sidewalls influence flame tilting angles, an air entrainment model for dual fire sources within tunnels was developed to derive flame tilting angles at different lateral positions and fire source spacing within tunnels. [Display omitted] • Studied flame traits of 2 heptane fires in a naturally ventilated tunnel. • Flame merging probability and tilt angle with different lateral fire positions. The maximum flame tilt angle is 24.20°. • Established dual-fire air entrainment model for predicting flame tilt angle. • Modified the velocity of flame entrains air from the region between fire sources. • Establishing the tilt angle of the flame by analyzing its geometric characteristics. [ABSTRACT FROM AUTHOR]

Reactive large-eddy simulations (LES) of the stage of peak heat release rate of open atmosphere glove box fires are carried out. To the best of the authors' knowledge, this is the first time that the LES of such a geometry is reported in the literature. A multi-fuel extension of the eddy-dissipation model (EDM) is used to simulate the combustion of the two distinct solid fuels, PMMA and Polycarbonate, relevant to this configuration. Three increasingly refined grids are considered. All of them lead to temperature values that are in good agreement with experimental data, and similar levels of heat release are obtained inside the glove box. From a more quantitative point of view, only the most refined grid leads to satisfactory values of LES quality criteria. The intermediate grid allows resolving a fraction of the inertial range dynamics, while the solution obtained on the coarsest grid exhibits very large turbulent structures with characteristic sizes of the order of the integral length scale. The analysis confirms that the choice of the grid cell size has a significant influence on the description of the local flow hydrodynamics, the location and thickness of the reactive zones. • Reactive LES of glove box fire are carried out with prescribed boundary conditions. • A generalized (i.e., multi-fuel) eddy-dissipation model is used to describe combustion. • Solutions obtained with increased levels of resolution display similar levels of heat release. • Increased levels of refinement improve the description of the reactive flow. • The internal flow topology and dynamics of a glove box fire are revealed by these LES. [ABSTRACT FROM AUTHOR]

Densified wood (DW) is a promising structural material in high-rise timber buildings. However, fire safety issues restrict its applications. The key is to understand the influence of component fractions and dense structure on DW combustion. Here, the combustion behavior of DW is experimentally and numerically investigated. Thermogravimetric analysis (TGA) results showed that DW has 29 K earlier and 1.01 × 10−4 s−1 lower peak mass loss rate, 5 % higher residue mass than natural wood (NW) due to the component weight fraction changes by delignification. ThermaKin was applied, combined with TGA, differential scanning calorimetry and microscale combustion calorimetry, to obtain pyrolysis kinetics and thermodynamics of wood. Cone calorimeter tests showed DW has delayed ignition time because its high density enhances heat conduction and decelerates wood surface temperature increase. DW has delayed but higher value of second heat release rate peak and lower heat of combustion due to its dense structure leading to a thermally insulating and condensed char layer. Radial thermal conductivity of wood linearly increases with density. Temperature poses greater impact on thermal conductivity than density. An optimized thermal conductivity equation is proposed and applied to predict the cone calorimeter tests, yielding good agreement. • DW has earlier/lower pyrolysis peak, higher residue mass due to delignification. • ThermaKin and STA/MCC are combined to get kinetics and thermodynamics of pyrolysis. • DW has delayed t ig and 2nd HRR peak , higher (lower) value of 2nd HRR peak, (Δ H c , mean ). • Both T and ρ enhance wood thermal conductivity, T has higher impact. • Predictions with optimized thermal conductivity well match experiment results. [ABSTRACT FROM AUTHOR]

Fire whirls cause strong wind damage in large outdoor fires such as wildland fires and urban fires. A model to predict the maximum tangential wind velocity in laboratory-scale fire whirls without flames in a crosswind is developed based on a generation mechanism and the properties of the fire whirls. The model also predicts the radii of the fire whirls and the crosswind speed when they occur. The fire whirls modeled are those with large circulation and large radii, that is, large intense fire whirls. These fire whirls occur and remain downwind of a fire line placed perpendicular to the crosswind under a low crosswind speed and a high heat release rate (HRR). The model agrees well with the experimental results. • A prediction model of laboratory-scale fire whirls without flames is proposed. • Fire whirls with large circulation and large radii are modeled. • The model is based on a generation mechanism and properties of fire whirls. • The model predicts the maximum tangential velocity, radius and crosswind speed. [ABSTRACT FROM AUTHOR]

Accurate measurement of the heat release from a battery fire is vital for risk management, product development and construction of accurate models. Oxygen consumption calorimetry is the most common method for heat release measurements in experimental fire tests. The strength of the method is that it can be applied to unknown compositions of fuel with sufficient accuracy. Despite that this method is used to estimate heat release from battery fires, the method is subject to discussion. In this work, the method is studied in-depth, and potential errors are structured and quantified. Uncertainties associated with self-generated oxygen and internal heat generation, total gas release from the battery and impact on the heat release calculations, as well as the assumed E -factor (i.e., heat release per unit mass of oxygen consumed), are thoroughly discussed. For a Li-ion battery fire, it is concluded that oxygen consumption calorimetry will exclude internal heat generation and underestimate the total heat released from the external flaming fire by up to 10 %. In addition, high rate of combustion reactions can result in that the measured peak heat release rate is underestimated much more, up to 100 %. [Display omitted] • OCC will underestimate the THR from the external flaming battery fire by up to 10 %. • On cell level, peak HRR was underestimated by up to 100 %. • Self-generated oxygen has limited impact on the OCC measurements. • CO correction is not recommended when using OCC for battery fires. • For battery fires, OCC and CDG measurements are expected to diverge. [ABSTRACT FROM AUTHOR]

In case of tunnel fire, vehicles can be blocked both upstream and downstream of the fire source. This paper presents a numerical study on influences of longitudinal ventilation and two same of obstacles placed upstream and downstream of the fire source on gas temperature distribution in a tunnel. The heat release rate, ventilation velocity and blockage ratio are varied. Results show that for a given ventilation velocity, as the blockage ratio increases, the inclination of fire plume gradually changes from the downstream to the upstream and the downstream smoke spread distance below the ceiling decreases. The Coanda effect (which refers to the adhesion of fluid on a convex surface) and the velocity vector field are introduced to explain the attachment of fire plume to the upstream obstacle. As the blockage ratio increases, the gas temperatures in the upstream of the fire source increase, while the gas temperatures in the downstream of the fire source decrease. The maximum temperature tends to decrease with increasing ventilation velocity. The effect of blockage ratio on maximum temperature is obvious for small ventilation velocities, while it becomes insignificant for large velocities. Then the maximum temperature model concerning the block effect and ventilation velocity are proposed. [ABSTRACT FROM AUTHOR]

Fire hazard of liquid fuel exposed in oxygen-rich environment is significantly greater than that in air, which should be considered in the safety risk assessment of scenarios where oxygen and fuel coexist. To reveal the effect of oxygen concentration on fuel properties and combustion characteristics of liquid fuel, a series of experiments were conducted to measure the liquid-phase component, flash point, lower flammability limit, heat release rate and flame height of rocket kerosene at different oxygen concentrations. The results show that the flash point of rocket kerosene (with an average chemical formula of C 11.98 H 22.64) decreases nonlinearly with the increased oxygen concentrations, while the oxygen concentration has a great enhancement effect on the heat release rate and visible flame height of rocket kerosene pool fire. Prediction models of the flash point and lower flammability limit based on the Clausius-Clapeyron equation, Le Chatelier rule and decreasing temperature assumption, as well as empirical equations of the heat release rate and visible flame height, were derived for different oxygen concentrations in this work, providing a new comprehensive understanding of the effect of oxygen concentration on the rocket kerosene, and could be further applied to fire risk assessment in liquid fuel and oxygen coexisting scenarios. • The average chemical formula of rocket kerosene can be expressed as C 11.98 H 22.64. • Flash point of liquid fuels decreases with the increased oxygen concentrations. • Prediction model of flash point at different oxygen concentrations is derived. • Oxygen concentration has a great enhancement effect on the HRR and flame height. • Obtained equations can be used in risk analysis of fuel/O 2 coexisting scenarios. [ABSTRACT FROM AUTHOR]

A series of full-scale compartment fire experiments was carried out to understand the fire behavior in compartment containing wooden constructions. The opening size and the surface area of combustible materials were adjusted to investigate the differences between ventilation-controlled and fuel-controlled fires. The results show that there was a time lag between when heat release rate (HRR) began to decrease and the time when the temperature in the compartment began to decrease in the case of with a wooden wall and ventilation-controlled fire; the HRR at the time when the temperature began to decrease was about the peak HRR of the case without a wooden wall. Although the HRR in case with a wooden wall was much higher than those without it, the temperature in the compartment with a wooden wall was slightly lower under ventilation-controlled conditions. These suggest that the amount of inflow air was limited by the increase in pressure in compartment due to pyrolysis gas. Furthermore, a model of compartment fires that takes this increase in pressure into account was developed, and it is able to more accurately reproduce the temperature characteristics than models that do not. • A series of full-scale compartment fire experiments involving wooden members was carried out. • Higher heat release rate but lower temperature caused by pyrolysis gas of wooden wall in under-ventilated fire. • Delamination and self-combustion enhance charring rate. • A compartment fire model that considers pressure increase owing to pyrolysis gas was developed. • HOC of flaming wood ranges 12–13 kJ/g, that of char oxidation ranges to 30–35 kJ/g. [ABSTRACT FROM AUTHOR]

This work is aimed examine the effect of ullage height (tank roof to fuel surface) on the flame behavior of turbulent diffusion flames. A series of experiments with eight ullage heights (h = 0–28 cm) were conducted. Propane was issued from a gas burner (D = 20 cm) with different fuel supply rates. Experimental results showed that the total flame consists of an upper flame (L upper , outside the tray) and a down-reaching flame (L down , inside the tray). It was found that L down decreases with fuel supply flow rate and there is a critical fuel supply flow rate (Q ˙ s,c), independent of the ullage height, above which there is no down-reaching flame. Depending on the ullage height and fuel supply rate, the flame behaviors can be divided into three regimes: (Ⅰ) restricted down-reaching, (Ⅱ) free down-reaching and (Ⅲ) no down-reaching. Based on the dimensionless analysis, correlations were developed to predict the down-reaching, upper, and total flame lengths, respectively. These correlations were validated against the experimental data in the paper and the previous literature. The present results are of importance to understand the flame behaviors for the burning of fires with large ullage heights and provide guidance in risk assessment of tank fires. • Experiments for gaseous fuel flame with different ullage heights are conducted. • Flame behaviors are divided into three regimes based on the flame base position. • Critical down-reaching flame length independent of the ullage height is revealed. • Correlations for the flame lengths with various ullage heights are developed. [ABSTRACT FROM AUTHOR]

This paper presents the experimental results of intermediate-scale tests related to the fire behaviour of high-pressure laminate (HPL). The experiments correspond to a cladding submitted to an exterior fire, to study its thermal decomposition and burning behaviour when exposed to two heat fluxes: 30 kW m−2 and 60 kW m−2. Measurements of mass loss, mass loss rate (MLR), gaseous emissions, heat release rate (HRR), temperatures and position of the thermal decomposition front have been performed for two sample sizes of 50 × 50 cm2 and 100 × 100 cm2. Considering the mass loss, the MLR, the HRR and the temperatures, 3 stages have been identified during the fire development of the samples. The first one corresponds to the heating phase of the sample, the mass loss and gaseous emissions are almost null. However, the measurements of the thermal decomposition fronts highlight that this first stage of fire development can be divided into two phases: an initial phase where the front is spreading and a secondary phase where it remains constant. The second step corresponds to the inflammation of the sample. During this stage, temperatures reached 1000 °C in the air cavity and the heat fluxes on the upper part of the sample reached between 50 and 70 kW m−2. The last one corresponds to the extinction. • Intermediate scale results concerning a High-Pressure Laminate. • Measurements of mass loss, gaseous emissions, thermal parameters. • Three main stages of fire development. [ABSTRACT FROM AUTHOR]

Fire smoke is one of the most important factors causing casualties, but also has the potential to bring some harm to the surrounding environment. In this work, the longitudinal temperature profile and the pollutant toxicity of a ceiling jet induced by a wall-attached fire with different tunnel slopes, were numerically and experimentally investigated by using a 1:8 reduced-scale inclined tunnel. The results show that for a given heat release rate (HRR), the flame extension is longer and the temperature decay is slower in ceiling jets induced by a wall-attached fire than for similar free-burning fires, because the air entrainment is restricted by the tunnel side walls. Further, the uphill pollutant toxicity was found to be higher with greater HRR and lower tunnel slope. Finally, a correlation between the non-dimensional longitudinal smoke temperature and CO concentration could be established for the inclined tunnel fire. • Longer flames and higher temperatures are induced by a wall-attached fire compared to a free-burning fire. • The pollutant toxicity is analyzed and discussed as a function of the tunnel slope. • A correlation between temperature and CO concentration in an inclined tunnel is proposed. [ABSTRACT FROM AUTHOR]

A parametric experimental study was performed to characterise the fire spread dynamics in a simplified ventilated façade using a medium-scale testing rig comprised of a non-combustible and a combustible cladding wall (1800 × 600 mm). Three different cavity widths and four different cladding materials were tested. Measurements of the flame height, the incident heat flux on the non-combustible cavity wall and oxygen consumption calorimetry were performed. A strong relationship between flame height and heat release rate was found for the growth phase of the fire. It has been shown that the time for encapsulation failure and subsequent cladding material core ignition decreased as the cavity width was reduced since the heat transfer to the walls was enhanced. The increase in the heat transfer to the opposite wall with all the materials could lead to external heat fluxes above the critical heat flux for ignition of a number of combustible cladding materials. This highlights the importance of considering the interaction of the products used in the façade and its geometry for the design of façade assemblies when accounting for the fire performance of the system. The results also show the need to understand the impact of the interaction between the design variables and the system performance, since the material performance observed at bench-scale may fail to capture the performance in heat transfer and flame spread scenarios observed at a system scale. • Flame height and spread rate can be related to the heat released by the material. • A higher incident peak heat flux can be observed for fires generated by the combustion of insulation foams compared to ACPs. • A narrower separation between parallel plates might outweigh the benefits of adding a fire retardant to polymeric ACP cores. [ABSTRACT FROM AUTHOR]

This study clarified the effect of water spray on fire control and extinguishment in a tunnel fire. A series of fire experiments were conducted using a 1:10 scale model tunnel to investigate the performance of water spray for suppressing the fire and blocking the smoke produced by the fire. The water spray trapped the smoke in the fire zone and prevented the inflow of fresh air from the tunnel portal. That is, the water spray sealed off the smoke and compartmentalized it in the tunnel. A calorimetry method was developed to estimate the chemical heat release rate (HRR) in the tunnel with the sealed-off descended smoke. Within the test conditions considered in this study, the following results were obtained. First, self-extinguishment occurred in 86% of the cases tested in the fire zone sealed off by the water spray. Second, the maximum HRR of the vitiated fire induced by the water spray was reduced to one-fifth compared to that during free burning. Finally, a ghosting flame and self-extinguishment by suffocation occurred when the smoke blocking rate exceeded about 60% and 80%, respectively. • Smoke is forced down by water spray and backflow of vitiated air occurs in a tunnel. • Ghosting flame and self-extinguishment of a vitiated fire is attributed to water spray. • The heat release rate during a vitiated fire in a tunnel with a water spray system is estimated. • A calorimetry method is developed for estimating the heat release rate in a vitiated fire. [ABSTRACT FROM AUTHOR]

Large-scale experiments were performed to investigate the influence of the melting flow of thermoplastic materials on discrete downward flame spread in façade fires. Expanded polystyrene, one of the flammable insulation materials broadly used in buildings, was selected as the study object. The fuel coverage (f = h fuel /(h fuel + h b)) was adjusted via barrier heights (h b = 30, 50, 70, and 90 cm) to explore its impact on flame propagation and heat release rate. The discrete flame spread process with burning flows was clarified into five stages, and the critical fuel coverage for preventing flame spread was found to be 0.40–0.46. The heat release rate of the entire burning process was measured, revealing that fuel coverage significantly impacted the HRR curve shape and peak value by influencing the formation time of pool fires above and below the barrier. Additionally, the properties of burning flows were characterised by area and HRR. A proportional relationship was established between the pool fire height and spill fire area. This research provides a novel observation of melting flows developed from burning thermoplastic material and uncovers the influence of melting flows on flame propagation in façade fires. • Discrete flame spread by burning flows was explored via large-scale experiments. • The critical fuel coverage for preventing flame spread was found to be 0.40–0.46. • The fuel coverage influences the HRR curve by peak value and peak amount. • Spill fire HRR was quantified from the total HRR and linearly distributed with area. [ABSTRACT FROM AUTHOR]

This study investigates the behaviour of a fire propagating over a long length of electrical cables, in order to assess the maximum burning length and the associated heat release rate of the travelling fire. It is part of the research work conducted in the framework of the OECD/NEA PRISME 3 project for a better assessment of fire propagation over cable trays in nuclear installations. The fire scenario consists of a set of 3 horizontal cable trays 6 m long, positioned in the corridor of a mechanically ventilated large-scale compartment. The parameters of the study are the nature of the cables (thermoset or thermoplastic types) and the distance of the cable trays from the ceiling. The determination of the fire heat release rate (HRR), the total burning length, the velocity of the flame front, the heat release rate per unit area (HHRPUA) and the effective heat of combustion (EHC) of the cable fires are given. For the configuration studied (3 cable trays and a given load), fire HRRs of 160 kW and 520 kW corresponding to burning lengths of 2 m and 3 m and corresponding to velocities of 0.4 mm/s and 0.9 mm/s are obtained for thermoset cables. For thermoplastic type cables (made of polyvinyl chloride), a power of 730 kW corresponding to a burning length of 3.5 m and corresponding to a velocity of 1.9 mm/s is reported. The order of magnitude for HRRPUA and EHC were respectively ranged between 50 kW/m2 and 150 kW/m2 and 20 MJ/kg and 25 MJ/kg for the two cable types. • Large scale fire tests of long cable trays. • Flame spread velocity of travelling fire over long cable length. • Effect of distance from the ceiling and cable type. [ABSTRACT FROM AUTHOR]

Continuous fuel spill fires are a common accident scenario which needs to be considered for the safe operation of tunnels, given the potential threat posed to trapped persons. In this paper, a series of continuous spill fire experiments on a concrete surface were studied using a 1/8 reduced-scale tunnel model. Gasoline was used as the discharge fuel and the discharge rate varied from 1.5 to 5.2 ml/s. The burning area, steady regression rate, smoke front arrival time, and ceiling temperature were analyzed. The results show that the burning area spreads slowly following an initial rapid spill stage, with the spread process following a pattern of exponential decay. The steady regression rate is found to be approximately 63% of that of pool fires for the same burning area. At the same heat release rate, the smoke front moves faster for spill fires than pool fires because of the larger burning area, and a correlation is built to predict the smoke front arrival time. Finally, a ceiling temperature rise prediction model is developed which considers the spread and burning processes of the fire. The results are of practical importance in the quantitative risk assessment of liquid fuel fire accidents in tunnels, and their implications for personnel evacuation. • The spread processes of the liquid layer and smoke front of a continuous spill fire are studied in a model-scale tunnel. • The arrival time of the smoke front is smaller for spill fires than for pool fires due to a larger burning area operating. • The regression rate of spill fires is higher in a tunnel than in open space, and is lower on concrete than fireproof glass. • A ceiling temperature rise prediction model is developed and validated by experimental data from the tunnel spill fires. [ABSTRACT FROM AUTHOR]

The paper presents a numerical study on an 18 cm-diameter liquid pool fire in a reduced-scale and mechanically-ventilated enclosure. The enclosure walls are made of a calcium silicate layer and a steel layer on five sides, the remaining sidewall is made of heat-tempered glass. The ventilation system is extracted mechanically with free air inlet. Three air renewal rates (ARR) and open atmosphere conditions are considered in the numerical study. Computational Fluid Dynamics (CFD) simulations are carried out with Fire Dynamics Simulator (FDS 6.7.5). The default evaporation model in FDS (i.e., forced convection approach) is compared to a natural convection approach implemented in the source code. The results show that the oscillatory combustion, occurring at ARR = 15 h−1, is best captured by the natural convection approach. It is also found that prescribing the fuel Auto-Ignition Temperature (AIT) is important to capture the fire oscillations and (local) flame quenching. At ARR = 8 h−1, extinction occurs. It is found that prescribing the fuel AIT allows to prevent spurious oscillatory combustion. At ARR = 22.5 h−1, there is a stable steady-state burning regime for which (as well as for open atmosphere conditions) prescribing the fuel AIT is not crucial. • Fire burning regimes are well predicted in a wide range of ventilation conditions. • Oscillatory combustion is captured by natural convection for evaporation modeling. • Prescribing Auto-Ignition Temperature is important in capturing fire oscillations. • Prescribing AIT prevents spurious fuel re-ignition in under-ventilated conditions. [ABSTRACT FROM AUTHOR]

A numerical study was conducted to quantify the effects of water vapor addition to oxidizer on soot formation in ethylene/hydrogen flames in a benchmark coflow configuration. The objective was to quantify the dilution, thermal and chemical effects in terms of their contributions to the change in sooting properties and flame radiation. The conditions are selected to keep constant the heat release rate of the flame while adding hydrogen and to maintain the mass flow of air of the oxidizer while adding water vapor. On the one hand, a consistent decrease of flame height, soot volume fraction, carbon-to-soot conversion efficiency and total radiation emitted by the flame was observed when increasing the mole fraction of hydrogen on the fuel side. On the other hand, water vapor addition to the coflow slightly increases the flame height, and reduces soot volume fraction and temperature. A consistent decrease is observed on the local radiative power per unit volume by soot, CO and CO 2. However, the total radiative losses are enhanced by the water vapor presence at high temperatures. In general, the dilution effects are dominant for the change of soot loading and radiation, whereas the thermal effects are dominant for carbon-to-soot conversion efficiency. Finally, a chemical pathway analysis was conducted to quantify the changes in the main reactions for soot precursor formation affected by addition of hydrogen and water vapor. These results provide fundamental insights to researchers and practitioners dealing with fires caused by hydrogen-enriched mixtures, which are attempted to be extinguished by traditional means by adding water. • Hydrogen reduces soot loading, flame radiation, and carbon-to-soot conversion. • Water vapor suppresses soot formation and lowers flame temperature. • Water vapor raises total radiation due to high-temperature water content. • Dilution effects dominate for soot loading and radiation. • Thermal effects dominate for carbon-to-soot conversion efficiency. [ABSTRACT FROM AUTHOR]

Cross-laminated timber (CLT) is becoming increasingly popular due to its many advantages. However, it has been shown that exposed CLT can have a significant effect on fire dynamics and spread rates. Further studies are therefore needed to better understand the impact of CLT to fire safety. Two large-scale CLT compartment fire experiments (95 m2) representing a modern office building have been performed, #FRIC-01 and #FRIC-02. This paper presents the second experiment, #FRIC-02, with exposed CLT on the back wall and the ceiling. The fire developed fast and spread across the room in less than 3.5 min from ignition of the wood crib on the floor and in 1.5 min after the ignition of the ceiling. Large external flames were observed, despite the compartment being well-ventilated. The 5-layer CLT, which comprised a 40 mm thick exposed outer layer and was face-bonded using a common European polyurethane adhesive, exhibited glue-line integrity failure and led to a second flashover after a significant period of decay. Subsequent layers of 20 mm also delaminated before the fire was manually extinguished after 3 h. Compared to #FRIC-01, the fire spread rate was faster, and temperatures, charring rates, heat release rates and external flames were higher. [Display omitted] • Flashover after 3 min and 13 s. • Large and asymmetrical external flaming despite compartment being well-ventilated. • Self-extinguishment of flames at CLT while the wood crib was burning. • 2nd flashover after a long decay phase, followed by continuous fluctuations of fire intensity. • Strongly non-uniform charring and delamination. [ABSTRACT FROM AUTHOR]

In this paper, experimental and theoretical studies of the flame shape and burning rate of pool fire inside a semi-confined compartment (with one sidewall and ceiling open) under the cross wind were investigated. The effects of fuel pool size and cross wind velocity on the flame morphological parameters and burning rate were obtained. Three typical bending behavior of the tilted flame was observed during the experiments. The dimensionless burning rate m ˙ ″ * decreased slightly when F r w < 1 , and increased linearly with F r w when F r w ≥ 1. An air gap (δ a i r ) between the flame and sidewall was observed because of the restriction of the sidewall and blow-off by strong airflow recirculation. Theoretical analysis of wind-blown pool fire inside the semi-confined compartment was conducted based on the asymmetrical air entrainment and the buoyancy length scale. A dimensionless parameter ( s m ˙ f ρ ∞ u w l b 2 ) considering the burning rate and cross wind velocity was proposed to predict the flame height, flame tilted angle and air gap thickness. The flame morphological characteristic parameters and the thickness of the air gap were correlated linearly well with the dimensionless parameter in exponent expression. • Three typical bending behavior of the tilted flame was observed inside semi-confined compartment. • Air gap between the flame and sidewall was generated under the influence of cross wind. • A nondimensional analysis of burning rate and cross wind explains flame height, tilted angle and air gap thickness. [ABSTRACT FROM AUTHOR]

Accurately representing the time dependent heat release rate of fuels is critical to performance-based design in fire safety applications. Existing simplified models either use average pyrolysis rates at different heat fluxes or do not account for the change in burning behavior at higher heat transfer rates. This paper presents the theoretical basis of a scaling-based pyrolysis model, S-Pyro. The model is based on the concept of maintaining the shape of a reference heat release rate per unit area curve but scaling the magnitude and time based on a dynamic thermal exposure. The model has been implemented in the computational fluid dynamics software Fire Dynamics Simulator (FDS). The model is validated with solid-phase only and multi-phase simulations of cone calorimeter experiments. The solid-phase simulations evaluated the capability of the model to predict the heat release rate per unit area of 149 materials tested at heat fluxes other than the reference flux. Multi-phase simulations of bench-scale fire experiments with a single material, Canada Pine and Spruce plywood, were used to evaluate the performance of the pyrolysis model in FDS. The model uncertainty was lower for high heat release rate materials, with the model uncertainty approaching the experimental uncertainty at higher burning rates. • Developed a scaling-based model to dynamically scale cone calorimeter data. • Validated the model using experimental measurements from 149 different materials. • Implemented pyrolysis model as an option in Fire Dynamics Simulator (FDS). • Evaluated the impact of the model on burning behavior in FDS simulations. [ABSTRACT FROM AUTHOR]

The convective heat transfer coefficient h c characterizes the heat transfer capacity between the fluid-solid interface in a thermal convection phenomenon. At present, values adopted from specifications are mostly used to define the h c coefficients in localized fire researches. In this paper, the specific scenario of the steel column surrounded by fire plume is selected as a typical case to explore the surface h c change rules of the steel column under the action of the fire source at the bottom. Different from the application of the concept of adiabatic surface temperature (AST) to achieve fluid-solid thermal coupling, this paper takes the scenario with the fire source heat release rate (HRR) being 81 kW as an example and conducts a two-way coupling simulation analysis of the fire and the thermal models by means of CFD codes. First, the validity of this simulation methodology is verified by comparing the results of the numerical model and the experiment. Following this, the distribution laws of the spatial velocity and temperature fields are analyzed, and the h c coefficient of the steel column surface is explored in detail using theoretical formula and traditional empirical formula respectively. It is noted that the h c results obtained based on theoretical formula can comprehensively consider the velocity boundary layer and temperature boundary layer situations above the column surface, which is a direct result of the definition of the convective heat transfer coefficient. It is found that the h c ‾ is lower at the bottom of the column and increases with height, with relative maximum value in the lower and middle parts of the column, reaching around 40 W/m2 K. The h c ‾ results decrease along the axial direction, with the value of upper part of the column being about 20 W/m2 K. In contrast, the h c ‾ distributions along the height obtained by the empirical formulas are similar to the distribution of fire plume velocity along the height. In other words, it considers only the effect of the velocity boundary layer, while the effect of significant changes in fluid temperature on convective heat transfer behavior is less considered. Compared to the results based on the theoretical definition, the h c ‾ results obtained by empirical formulas are significantly smaller in the lower and middle parts of the column, and higher at the top of the column. Finally, a new h c ‾ practical formula for the column surfaces surrounded by fire plume is proposed, which agrees well with the results based on the theoretical definition in several cases. • h c based on theoretical definition comprehensively considers velocity and temperature boundary layers, and shows large differences from that based on empirical formulas. • A new practical formula for the column surface h c coefficient surrounded by fire source is proposed. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study and analysis of the ejected fire plume from an opening at the top floor of the compartment under facing wind condition. The experiments are conducted by a reduced-scale cubic compartment. An opening facing the wind tunnel exit is set at the center of the compartment side wall. The temperature at the opening and inside the compartment, critical heat release rate for flame ejection, ejected flame morphologic characteristic parameters are measured and quantified by thermocouples and a digital video camera. It's found that the temperature and critical heat release rate for flame ejection first increase then decrease with increasing of facing wind speed. The flame height, flame depth and flame horizontal length increase with heat release rate. The flame depth decreases, flame horizontal length increases as the facing wind speed, while flame height shows a complex evolution with facing wind. A physical model is developed considering mechanisms of flame ejection initial horizontal momentum, flame buoyancy, wind momentum and non-dimensional mass fuel supply rate. The proposed model correlates the experimental data of flame morphologic parameters well. This work considering the practical fire scenario provides an important knowledge supplement on the classical building fire dynamics. • Studying the ejected fire plume from an opening under facing wind passing through the roof. • Revealing the evolution of the temperature inside the compartment and opening. • Quantifying the flame morphologic parameters evolution with facing wind speed. • Proposing a physical model of the flame morphologic parameter. [ABSTRACT FROM AUTHOR]

The current research study discusses and characterises the fire decay and cooling phase of post-flashover compartment fires, as they are often mixed up despite their important heat transfer differences. The two phases are defined according to the fire heat release rate time-history. The fire decay represents the phase in which the fire heat release rate decreases from the ventilation- or fuel-limited steady-state value of the fully-developed phase to fire extinguishment. This phase is highly influenced by the fuel characteristics, ranging from fast decays for hydrocarbon and liquid fuels to slow decays for charring cellulosic fuels (wood). Once the fuel is consumed, the compartment volume enters the cooling phase, where the cooling in the gas-phase and solid-phase happens with significantly different modes and characteristic times. The thermal boundary conditions at the structural elements are then defined according to physical characteristics and dynamics within the compartment. The research study also underlines how the existing performance-based methodologies lack explicit definitions of the decay and cooling phases and the corresponding thermal boundary conditions for the design of fire-safe structural elements under realistic fire conditions. • Characterisation of decay phase and cooling phase of post-flashover compartment fires. • Fire decay and cooling phases associated with fire heat release rate. • Fire decay phase largely fuel-dependent. • Fast decay for hydrocarbon and liquid fuels, slow decay for charring cellulosic fuels. • Relevance of defining the various phases and appropriate thermal boundary conditions. [ABSTRACT FROM AUTHOR]

This study analyses the performance of non-intrusive PIV (Particle Image Velocimetry) for the study of flows induced during a fire scenario in a mechanically-ventilated enclosure. PIV can be used to obtain detailed measurements for velocity fields in the enclosure and thus offer new experimental data for the understanding of the physical phenomena involved as well as to validate CFD simulation tools. The study is carried out on a reduced scale on an ethanol pool fire positioned in a ventilated enclosure. Several areas of interest are studied such as interaction between the fire plume and the ceiling, the flow under the ceiling and parietal flows. These zones can be analysed to obtain a picture of the global mean flow and associated velocity fields rarely reported in the literature. The influence of the fire heat release rate on the velocity fields is studied and highlights the design parameters. • The feasibility of using PIV for compartment fires. • Global 2D flow fields in a mechanically-ventilated enclosure. • The effects of fire HRR on the flow field. [ABSTRACT FROM AUTHOR]

Elevated pool fires are potentially exposed to the feedback of radiative heat fluxes from the ceiling that can modify the mass loss rate. In this regard, an experimental study was carried-out in a reduced-scale enclosure with a pool fire brought increasingly closer to the ceiling of the compartment. The objective is to study the effect on the mass loss rate of the increase in radiative heat fluxes without any air vitiation effect. The device is equipped with a mechanical ventilation system to allow the flame to develop in a well-oxygenated environment. The fire sources used are circular pans with diameters between 0.09 and 0.175 m, filled with dodecane. Results show that, as long as the flame does not impinge on the ceiling, the mass loss rate remains quasi-constant. On the other hand, when the flame impinges on the ceiling, the mass loss rate increases drastically and can be multiplied by a factor 2–3 compared to the reference value when the pool fire is located on the ground. Scaling parameters, showing the generic aspect of the results, are finally proposed considering a dimensionless elevation h*. It allows to gather all experimental data on the same curve for all the fire sources tested. • Two combustion regimes stand out depending on the fire source elevation. • Mass loss rate multiplied by 2.5 when the fire source approaches the ceiling. • A change in the combustion regime related to the flame impingement over the ceiling. • New scaling parameters showing generic trends. [ABSTRACT FROM AUTHOR]

The risk of fire in residential buildings is relatively high, with a significant number of incidents and loss of life reported. This study aimed to examine fire scenarios in bedroom by conducting real scale experiments with different set-up of vents and using realistic fuel loads. Five full-scale compartment fire tests were conducted, and a sprinkler system was installed in one of the rooms. The experimental setup, fuel arrangement, and instrumentation are described, and the fire characteristics was analyzed based on visual observations and temperature data processing. The performance of the fire detectors and sprinklers in the tests are discussed. The influence of opening size on the peak temperature, heat release rate, and the constant coefficient of Kawagoe law are estimated and analyzed. Furthermore, a non-dimensional neutral plane height was found to have strong relationship with the constant coefficient of Kawagoe law. • Five real scale tests simulating bedroom fires were conducted. • The influence of vents and sprinklers on fire development were investigated. • The relationship between mass flow rate and ventilation factor under different vent conditions are estimated. [ABSTRACT FROM AUTHOR]

Decarbonization has driven the construction industry to rediscover biobased, but inherently combustible, materials like timber. To avoid compromising fire safety, reaction to fire of timber can be effectively reduced by fire retardant surface coatings or impregnation treatments. Using a combination of simultaneous thermal analysis, microscale combustion calorimetry and cone calorimetry, vacuum-pressure impregnated (boron free, phosphorus-based) plywood was tested against plywood coated with a thin layer of water-based fire retardant intumescent coating (melamine free, phosphorus-based). Comparing the peak heat release rate (pHRR) and total heat release (THR) of the three plywood samples, the impregnated was lowest, and the coated was lower (pHRR −34% and −20%, THR -45% and −21% respectively) relative to the untreated plywood. In contrast, the coating layer postponed sustained flaming for longer than impregnated wood and delayed burnthrough, effects critical to the growth rate of a developing fire. Better understanding of the assessment of flammability of fire protected timber has been obtained using cone calorimeter data supported by microscale analyses. The results challenge the simple flammability ranking based on total heat release, and highlight the need for further development of a methodology for comparing different fire protection strategies for timber. • Fire protection either by coating or impregnation reduces flammability of timber. • The mechanisms of both treatments are investigated in detail. • The impregnation treatment acts in both gas and condensed phases. • The intumescent coating acts as barrier, limits fuel gas release and delays burnthrough. [ABSTRACT FROM AUTHOR]

When designing scenarios for fire safety in residential buildings, one should consider the natural variability of heat release rate of a single item that can possibly influence fire spread between multiple items. This study intends to represent experimentally measured design fire for single residential items using a combination of t-squared growth method and Ingason exponential decay method. The characterizations required three representative data from experiments including maximum heat release rate, time to reach the maximum heat release rate and total heat released. The methods have established good representations of the experimental design fires with more than 86% similarity. Distribution statistics are considered to characterize the design fires in a probabilistic manner which develop possible design fires from an average curve as well as within a minimum/maximum limit and a 5th/95th percentile limit. Comparisons denote that the probabilistic design fires are reliable to represent the possible heat release rate for single residential items. • Experimental heat release rates are used for statistical and distribution analyses. • Peak heat release rate, time to peak heat release rate and total heat released are examined. • T-squared growth method and Ingason exponential decay method are combined. • Probabilistic functions are employed for design fires characterization. • Representations of possible heat release rates are established for single residential items classifications. [ABSTRACT FROM AUTHOR]

To better understand fire dynamics of buoyant turbulent diffusion flames under different oxygen concentrations (OCs, volumetric basis), we have recently conducted measurements on the flame temperature, radiation, and soot temperature and volume fraction under normal and reduced OCs. In the present study, particle image velocimetry (PIV) technique was employed to investigate the effect of OC (20.9%, 16.8%, and 15.2%) on the velocity field of the same flames with a theoretical heat release rate (HRR) of 15 kW. The statistics of the velocity field, such as mean and standard deviation of velocity, turbulent kinetic energy, Reynolds stress, and turbulent viscosity, were investigated and compared among different OCs. Results show that OC has minimal effect on the velocity distribution at heights close to the flame length. However, at lower heights above burner (HABs), turbulent mixing is reduced under reduced OCs, and the velocity shows an increased value at the flame centerline but with a narrower profile along the radial direction. Finally, a comparison with previous data was conducted and analyzed to further explore the fire dynamics. This study improves the physical understanding of related fire dynamics under reduced OCs and provides a comprehensive dataset for turbulent fire modeling validation. • A dataset of velocity field in buoyant turbulent diffusion flames is reported. • Turbulence statistics is analyzed and provided for modeling validations. • Turbulent mixing is reduced at lower locations under reduced oxygen concentrations. • Velocity near flame height is not affected under the studied oxygen concentrations. [ABSTRACT FROM AUTHOR]

Automatic real-time fire characterization is a crucial requirement of future smart firefighting. This work proposes a novel computer vision method to automatically measure the fire heat release rate, even when the camera is moving in real-time. Firstly, a portable binocular stereo camera is used to capture the real-time fire video stream that is fed into a pre-trained computer-vision model frame-by-frame to detect the fire region. By identifying the fire location inside the image, the real-time distance between the camera and the fire source is determined. This fire distance helps re-scale the images to match the input scale of the AI-image Fire Calorimetry. Then, the deep learning model can automatically output the transient fire power in real time. Results show that the stereo vision system is capable of accurately measuring the distance between the camera and the fire source, flame height, and power, with a relative error of less than 20%. This work provides an automatic and flexible way to measure the distance, power and hazard of fire in real-time, and such a method has broad applications in firefighting operations and decision-making. • Propose a smart fire calorimetry method based on computer vision and AI-driven fire identification. • Use binocular camera to measure the real-time fire distance and determine the fire dimension. • Combine fire image from a moving camera and deep learning to quantify fire heat release rate. • Provide a framework of AI-Fire calorimetry for a fast fire hazard assessment in smart firefighting. [ABSTRACT FROM AUTHOR]

Kitchen is the most common origin of residential fires, and usually the fire starts from a cooktop. To increase the understanding of such fires, we measured the electric power and surface temperatures of three different cooktops and four frying pans, and measured the ignition times and heat release rates (HRR) from cooking oils, butter and four different solid items (pizza box, pot holder, paper towel roll, LDPE bags). The estimated ignition probability of oils and butter was 0.44 ± 0.13, with an ignition time of 309 ± 81 s and peak HRR of 300–600 kW/m2. Solid items ignited with 0.80 ± 0.10 likelihood in 378 ± 228 s, reaching higher temperatures at ignition compared to oils. LDPE bags posed the highest risk due to their propensity to ignite, melt, and burn with peak HRR exceeding 2000 kW/m2. The ignition times were mainly controlled by the cooktop heating, while the material processes delayed the ignitions by 23%. Stove guards (EN 50615 cat. B) activated before ignition in all tests, except for the pizza box and pot holder. Ignition prevention was not tested, though. Further development of the stove guard standard is therefore necessary to effectively prevent fires originating from auxiliary materials. • Induction cooktop showed shorter ignition times than electric coil and ceramic glass cooktops with similar electric power. • EN 50615 cat. B stove guards activated before the oil ignitions but too late for overheating solid items, like pizza boxes. • Cooking oils (50 mL) ignited in 44 ± 13% of the tests with ignition time 325 ± 100 s and peak HRR between 300 and 600 kW/m2. • Thermoplastics left on a hot stove ignite with high likelihood, melt and burn with a peak HRR greater than 2000 kW/m2. [ABSTRACT FROM AUTHOR]

This study investigates the burning history of medium-density fibre (MDF) cribs in an underventilated enclosure with two vertical openings in the front wall. Such compartment fires have been explored before by other researchers and demonstrated the conditions that would lead to smoke explosions (Sutherland, 1999; Chen, 2012) [1,2]. A total of 19 experiments were completed, 5 of which led to smoke explosions. A gas conditioning system is utilised for the experiments which included a hydrocarbon analyser and an enhanced Phi-meter. Heat release rate, mass loss rate, temperatures, pressures, and O 2 , CO 2 and CO gas concentrations within the compartment are measured for each experiment. Compartment fires with MDF crib fuel in underventilated conditions can lead to smoke explosions for both porosity-controlled and surface-controlled cribs. The smoke explosion is found to be occurring when the changes of pyrolysate gases and oxygen concentrations in the compartment form a flammable mixture. The equivalence ratio of the compartment was found between 1.5 and 2.0 before the occurrence of smoke explosions. Transformation of flaming combustion to smouldering was generally observed as a precursor for the accumulation of unburned fuel and the occurrence of smoke explosion. • Difference between smoke explosion and backdraft is reviewed. • The occurrence of smoke explosions is explained by experimental work. • Transition to smouldering was generally observed as a precursor of smoke explosion. [ABSTRACT FROM AUTHOR]

The maximum ceiling height of the FM Global laboratory is 18.3 m. Therefore, fire protection solutions for warehouses with taller ceilings cannot be directly validated through full-scale testing. This work develops a methodology to obtain the key processes of fire growth, spray-plume interaction, and fire suppression response for an 18.9 m high roll-paper storage under a 24.4 m tall ceiling. The proposed methodology uses a heptane burner assembly at the base of the commodity array to match the fire heat release and growth rate to that of a taller storage exceeding lab capability. The burner assembly included six heptane burners and two air ducts. A series of experiments was conducted to characterize the burner design, model the fire growth in the free-burn stage, and validate controlled and uncontrolled fires in terms of the number of activated sprinklers. A final large-scale fire test used a 12.8 m high storage of Kraft paper with the burner assembly under an 18.3 m tall ceiling to validate protection recommendations for Kraft paper stored 18.9 m high under a 24.4 m tall ceiling. The test demonstrated full suppression using K360 (K-factor, lpm/bar1/2), fast response, pendent sprinklers with a temperature rating of 74 °C, supplied with a water pressure of 8.3 bar. • Developed a testing methodology for ceilings exceeding laboratory limits. • Designed a burner assembly as a fire source to lower virtual fire origin. • Verified the methodology by running a series of large-scale experiments. • Obtained data to verify protection of 18.9 m high storage under 24.4 m tall ceiling. [ABSTRACT FROM AUTHOR]

A simple two-zone subgrid temperature distribution is developed to model turbulence-radiation interaction in the Fire Dynamics Simulator. The new approach enforces consistency between the subgrid flame distribution and the heat release rate from the eddy dissipation model. To investigate the performance of the new model, we simulate the University of Maryland turbulent line burner and compare global radiative fraction as a function of coflow oxygen dilution. The results suggest that the model can improve grid resolution dependence in prediction of radiative emissions. Sensitivity of the model predictions to the assumed fuel carbon to CO fraction (a parameter of the two-step fast chemistry scheme) was found to be significant, which is not surprising since this parameter essentially controls the in-flame soot concentration and generally has a first-order effect on resolved emission. Four different model variations were tested, corresponding to varying degrees of complexity in modeling the subgrid correlations for the absorption coefficient. Differences in results between model implementations were on par with the variation in results obtained with different path lengths applied to the gray gas model for the absorption coefficient. • We introduce a simple subgrid model for temperature and absorption coefficient distribution which is consistent with the heat release rate from EDC. • Model predictions for the radiative fraction of the UMD line burner experiments demonstrate improved accuracy and reduced grid dependency. • Two-step fast chemistry model is used for predicting the in-flame soot concentrations. • Model sensitivities to the assumed fuel carbon to CO fraction and the radiation model's path length are reported. [ABSTRACT FROM AUTHOR]

Wildfires currently represent an imminent danger to communities around the world due to their increasing severity and frequency. It is critical to expand current knowledge on wildfire behaviour to improve risk management practices, firefighting operation and engineering design in the Wildland Urban Interface (WUI). This paper reports 2D high resolution measurements of Byram's fireline intensity generated during a 150 × 200 m2 gorse shrub burn generated from visual and infrared video footage of the prescribed fire, and Light-Detection-and-Ranging (LiDAR) data of the vegetation canopy, both acquired using Unmanned Aerial Vehicles (UAV) technology. The results show that the fireline intensity was highly variable across the plot, reaching localized peak values over 40,000 kW/m and an averaged intensity of 14,300 kW/m approximately. An empirical correlation for estimating the average flame height was derived from the fireline intensity maps and from experimental measurements carried out during the prescribed burn. The correlation was used to produce a 2D detailed map of the average flame height of the prescribed fire, achieving a 11% of error compared to in-fire measurements. The findings from this research suggests that non-linear variabilities of fireline intensity should be carefully considered to adequately describe wildifire behavior of shrubland fires. • UAV-based observations were used to map and characterize the fireline intensity of a 150 × 200 m2 gorse prescribed burn. • Fireline intensity varied greatly within the plot, presenting intermixed areas of very low and higher intensity of roughly an order of magnitude difference within a few meters and seconds. • An empirical correlation for estimating the average flame height was derived and mapped achieving 11% of error compared to in-fire measurements. [ABSTRACT FROM AUTHOR]

Experiments have been conducted to evaluate the containment of smoke and heat using water mist curtains in a model setup of a ro-ro ship's cargo deck with a scale of 1:13, providing practical insights into the application of such fire protection systems in the cargo deck as well as valuable data for future numerical simulations. In this regard, the requirements of the international convention of Safety of Life at Sea (SOLAS) are studied for the side openings of so-called 'open decks' in comparison with 'closed decks', especially to examine the feasibility of using water mist curtains for creating isolated subdivisions in the ro-ro space as a fire management strategy. The water mist curtains are created with one or two rows of water mist nozzles at pressures ranging from 3 to 8 bar, while the source of smoke and heat is a liquid pool fire, and inert cargo items are used in some experiments. Correspondingly, the interaction between the water mist curtain(s) and the fire is evaluated in terms of its heat release rate, and the containment effect is quantified via measurements of smoke flow through the deck and through the windows, concentrations of gaseous species, as well as gas temperatures at various key locations. The study shows that water mist curtains have a strong effect on fire dynamics and smoke propagation, but containment is dependent on the configuration of side openings and the location of fire, among other important factors. [ABSTRACT FROM AUTHOR]

The fire behaviour of radiata pine timber, treated with intumescent coatings and exposed to heat flux conditions equivalent to a high-risk bushfire attack level (BAL) is investigated. The experiment is designed for coated timber exposed to bushfire attack levels greater than 19 kW/m2 and up to 29 kW/m2 (BAL-29) in accordance with AS 3959. The timber was coated with a DFT of 400 μm of the developed intumescent formulations based on expandable graphite (EG), ammonium polyphosphate (APP) and a waterborne acrylic resin with high adhesion strength. The coated timbers were tested according to AS3959, for a BAL-29 rating, using a cone calorimeter at 25 kW/m2 for 10 min. Most of the coated samples reported a substantial reduction in the peak heat release rate (p-HRR) and average HRR with values not greater than 100 kW/m2 and 60 kW/m2, respectively. These results satisfy the requirements for bushfire-resistant timber at BAL-29 rating. Formulation 4 (F4), with EG:APP ratio of 3:1 and resin content of 45 wt% was identified as the most cost-effective formulation. Coatings with high loading of EG and APP provided the best fire protection to the timber substrate, however, a larger char with a less compact structure is formed. • High adhesion strength was reported by the waterborne acrylic resin. • A cost-effective coating with 3:1 EG:APP ratio and 45 wt% resin was identified. • A substantial reduction in p-HRR was reported by the coated timber. • Key factors affecting the performance of the intumescent coating were identified. [ABSTRACT FROM AUTHOR]

In order to study flow stratification behavior in lateral smoke exhaust mode, experiments were carried out in reduced-scale model and numerical simulations model. The characteristics of smoke layer interface, smoke layer thickness, vertical temperature and normalized shear velocity in tunnel with different heat release rates were analyzed. The flow pattern was visualized by a semiconductor laser. The stratification pattern was found to fall into three regimes. Buoyancy, inertia force and suction force, as three factors affecting the flow stratification of smoke, are related by a new dimensionless number. At region I (F rs <2.4), the buoyancy stratification was stable, and there is an obvious interface between the upper smoke layer and the lower cold air layer. At region II (2.4< F rs <4.8), the buoyant flow stratification was stable, but the stratification interface between smoke and cold air was unstable. At region III (F rs >4.8), the stratification becomes unstable, the mixing between smoke and cold air was intense, and there is no obvious stratification interface. [ABSTRACT FROM AUTHOR]

The paper presented the main results of large-scale fire tests with different types of fixed firefighting systems (FFFS) conducted in the Runehamar tunnel in June 2016. The background to the tests, the performance of the different systems, and conclusions regarding the efficiency of the systems were presented. The fire load consisted of 420 standardised wooden pallets and a target of 21 wooden pallets. Five of the tests were carried out with a 30 m long deluge zone delivering varying water densities using three different types of side-wall nozzles with an interval distance of 5 m. One test with 93 °C glass-bulb automatic sprinklers in the same zone was also conducted. In the five deluge tests, the detection system was simulated using thermocouples in the tunnel ceiling. The alarm was registered when the ceiling gas temperature reached 141 °C, and the system was activated manually after a delay of 4 min. The protection goal of the system was to prevent fire spread to a target positioned 5 m from the rear of the main fuel area, and to ensure that the fire did not exceed 30 MW in size. The system setups tested were found to meet these goals. • Larger droplets better penetrate fuel, facilitate surface cooling and supress further flame spread. • The heat release rates were maintained mostly below 20 MW in tests with FFFS. • Maximum temperatures beneath the ceiling never exceed 800 °C in tests with FFFS. • Fire spread to a target at 5 m behind the main fuel load is completely prevented by FFFS. • Feasibility of using automatic sprinklers in tunnels is partly verified. [ABSTRACT FROM AUTHOR]