Fire Rate Research Articles

Fire Rate of Spread and Growth Rate in a Set of 30 Global Wildfires: New Evidence of Extreme Fire Behavior

Wildfire science needs new methods to evaluate and predict wildfire behavior and impacts. In this study, we present a new algorithm that calculates the maximum fire rate of spread resulting from a fire progression map made of isochrones, according to 1) the shape of the isochrones, and/or 2) prevailing atmospheric wind direction. We have applied the algorithm to a set of 30 fires, differentiated according to the way the isochrone map was surveyed: by firefighters’ GPS positioning (in Europe, ~ 1-hour frequency), or by satellite data (North and South America, and Australia, ~ 12-hour frequency). The rate of spread was also related to the growth rate in hectares, and with the morphology of the fire scar. Our results reveal maximum speeds of 8.62 and 6.79 km/h for the GPS and satellite datasets respectively. In general, the GPS dataset shows faster runs that burn smaller extensions than the satellite dataset. Runs following wind direction are more elongated than the ones driven by other factors, which show more expansive runs. The algorithm presented here can be useful for the study of the factors influencing fire propagation.

Effect of Spruce Wood Density on Selected Fire-Technical Parameters during Thermal Loading

The paper evaluates the effect of spruce wood density on the parameters of mass loss and mass loss rate during exposure to thermal load. The intention was to determine whether the effect of density is still evident after the application of flame retardants to the test samples. Groups of samples with different densities under the same retardant treatment were compared. The differences in densities of the compared groups of samples were different for each flame retardant. Water-soluble flame retardants based on inorganic salts were used. For testing, a simple test method was used in which the samples were exposed to direct flame from a Bunsen burner. The results of the study are the findings of how wood density affects the burning process of the samples treated with flame retardants. Statistical evaluation of the experimental results shows a significant effect of wood density on the monitored parameters even when flame retardants are used. For a difference in sample densities of 244 kg·m−3, there was a density dependence of the mass loss rate, with the lower density samples having a higher mass loss rate (0.158%·s−1) over the whole experimental period compared to the higher density samples (0.077%·s−1). The ANOVA test also demonstrated the influence of density on the mass loss of the samples at the above density difference. At lower density differences (51 kg·m−3 and below), the effect of sample density on the observed parameters was no longer evident. The fire spread rate parameter was also investigated. Here, a linear correlation between the difference in sample densities and the difference in the values of the above parameter at high and low densities is observed with a reliability coefficient R2 = 0.99.

Thermal hazard analysis and fire risk assessment of rocket kerosene in oxygen-enriched environment

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 C11.98H22.64) 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.

Study of relationship between motion of mechanisms in gas operated weapon and its shock absorber

The article deals with the motion of the breech block carrier and the weapon casing of an automatic weapon mounted on a flexible carriage and the base of the weapon. Earlier works, which did not consider the dynamic properties of the base of the weapon, did not allow to reconcile the calculated and experimental results of the weapon casing displacement when shooting from firing rests. For the analysis of the motion of individual parts, the methods of mathematical modelling and firing experiments using a high-speed camera were chosen. Calculations show the best accord with experiment when modelling the system with 4 degrees of freedom. The oscillation of the system regarding the movement of the breech block carrier and the weapon casing was investigated under changed conditions of rate of fire, the use of a muzzle brake and different types of shock absorbers. The velocities and displacements of the weapon casing and the breech block carrier at different values of the impulse of the gases to the breech block carrier were determined.

Application of artificial intelligence methods to model the effect of grass curing level on spread rate of fires

Artificial intelligence (AI) enables new approaches to fire behaviour models of operational relevance, including prescribed burns. This is particularly important in modelling of processes that are poorly understood, such as live fuel's effect on fire propagation. The objective of this study was to apply AI algorithms to quantify the effect of the proportion of dead fuels in a senescing grassland, the curing level, on reducing the rate of fire spread relative to the fully cured condition. We applied three different machine learning (ML) models, regression trees, support vector regression (SVR) and Gene expression programming (GEP), two ensemble ML methods, Random Forest and GEP Forest, and non-linear regression analysis to an experimental fire dataset. Results show SVR and GEP as the best ML methods to model the curing level impact on fire spread. No differences in model fit were observed between the best ML methods and non-linear regression analysis.

An Experimental Study of Pool Fire Characteristics under the Effects of Cross Winds and Baffles

The pool fires that occur behind obstructions in a ventilated environment are very different from other wind-blown pool fires. The pool fire formed by fuel leakage in an engine nacelle is a typical example of a pool fire influenced by cross winds and baffles. Mastering the combustion characteristics of this type of fire is of great significance for fire prevention and control. In this study, the burning rate, flame length, and flame tilt angle of heptane pool fires behind a baffle under different cross wind velocities (ranging from 0 to 5 m/s) were experimentally investigated. Square pool fires with dimension of 8 cm and 12 cm with baffle height from 4 to 12 cm and different distances between fire and baffle (0, 20, 30 cm) were tested in a wind tunnel. The experimental results show that the burning rate increases with the increase in cross wind velocity for each baffle height. As wind velocity exceeds 2 m/s, the burning rate first decreases and then increases with the increase in baffle height. The flame length initially increases and then decreases with increasing wind velocity. The upper flame tilt angle is mainly affected by the cross wind, while the bottom flame tilt angle is influenced by the combined effects of cross wind velocity, baffle height, and distance between baffle and flame. The empirical correlations under different distances between baffle and flame, with wind velocity and baffle height accounted for, are then proposed for the dimensionless heat release rate and the flame length of heptane pool fires.

OPTIMIZATION OF THE USAGE OF 35 MM ANTI-AIRCRAFT GUN BARRELS IN TERMS OF RELIABILITY AND ECONOMIC EFFICIENCY

The scientific basis for optimizing the use of work resources of 35 mm anti-aircraft gun barrels, enabling their durability to be increased by 25÷100% while improving operational efficiency indicators are presented in this paper. The development of a new approach to assessing the durability and effectiveness of these barrels results from current solutions and capabilities of navigation and targeting systems, new generation projectiles (programmable ammunition with sub-projectiles) and real-time muzzle velocity measurement applications (while main-taining or even increasing the current muzzle velocity and rate of fire). This increases the probability of hitting floating, coastal and flying targets (especially UAVs and RAM). It has been shown that the durability and operational assessment of this class of guns (including economic efficiency) is not determined only by indicators based on the rate of fire, muzzle velocity or second burst of fire. What is now more important is the ability to reduce the rate of barrel destructive processes, resulting from the possibility of shortening the length of firing series. It has been shown that with short series, the barrels wear and the intensity of damage to the reload mechanisms are significantly reduced. The phenomenon of barrel overheating is also limited, and thus operational indicators are improved (average time to failure, continuous operation time, ammunition usage), which significantly reduces the cost of operating the guns.

Study on flame height and temperature distribution of double-deck bridge fire based on large-scale fire experiments

Vehicle fire is one of the important causes of bridge fires. This study conducted large-scale actual fire experiments by simulating heat release rates (HRR) of oil tank truck fires with 50 MW, 100 MW, and 200 MW in rectangular oil pans of varying sizes. The flame shape and spatial temperature distribution at different HRRs were studied bycontrollingvariables such as wind speed,firesource location, andlayer spacing. The results indicated that the actual HRR of the large-scale fire exceeded the anticipated value. In large-scale fire experiments, flame splitting into two main peaks was observed along the long side of the rectangular oil pan due to the coupling effect of ambient wind, long side, and sidewall effect of the diagonal web member. The average flame height was determined through image processing, and subsequently, a formula for predicting flame height during bridge fires under varying heat release rates was developed through the use of dimensionless analysis and feature length analysis. The spatial temperature distribution in the vertical direction of the axis of the center of the fire source, the temperature distribution of the diagonal web member and the bottom of the dense crossbeams, which are critical components of the bridge, were also analyzed. Furthermore, the conclusion that the flame in the lower bridge space which split into two main peaks is validated by the results. The results of this study can provide important theoretical support for investigating bridge fire resistance strategies.

Varying Heat Release Rates per Unit Area – The Impact in Underground Mines

Abstract The fire behaviour and smoke behaviour of a fire in an underground mine will be largely dictated by the heat release rate of the fire. The heat release rate per unit area is generally the output from small-scale fire experiments and can be applied for larger objects with varying surface area. This paper studies the impact of varying heat release rate per unit area for fires in materials and substances typically found underground. Data from earlier fire experiments were analysed and discussed, and several different heat release rate curves and flame spread velocities for various fuel components were developed and discussed. It was found that the hydraulic hose presented the highest peak heat release rate per unit area of the solid fuel items, followed by the low-voltage cable, cab interior, and tyre in descending order. The increase in the peak heat release rate was highest for the highest incident heat flux levels, representative for scenarios underneath a mining vehicle. The heat release rate per unit area of pool fires underneath a vehicle is significantly higher than a corresponding free burning case - attributed to the higher incident heat flux – but a gravel surface underneath a pool fire will reduce the heat release rate considerably. Line fires in larger bundles of electrical cables were modelled and found to attain the peak flame spread velocity more rapidly compared with a fire in hydraulic hoses. This was caused by the higher heat release rate of the initial fire and ignited segments in the electrical cable case.

Experimental study of ullage height on the burning rate and heat transfer of medium-scale heptane pool fires

Ullage height (the distance between the fuel surface and the pool upper rim) is one of the most important and widely recognized factors that affect the burning rate and heat transfer of pool fires. This study investigated the effects of ullage height on the burning rate, heat feedback, and radiation fraction of medium-scale pool fires. Heptane pool fires were tested with a diameter (D) of 30 cm and the non-dimensional ullage height (h/D, h is the ullage height) being varied from 0 to 1.48. Results show that the non-dimensional burning rate tends to decrease exponentially with h/D. It has been proved that the current models used to predict the burning rate of pool fires are not applicable to those medium-scale pool fires that are affected by the ullage height. The radiative, conductive, and convective heat feedback rate overall decrease with the ullage height. The conductive heat feedback fraction weakly depends on h/D. The radiative heat feedback fraction firstly decreases then stabilizes with h/D, while the convective heat feedback fraction shows an opposite trend. The radiative fractions firstly increase then decrease with h/D. This paper presents a new correlation with considering the ullage height and the mean beam length within the pool ullage. The universality and accuracy of the proposed model were verified by comparing it with extensive experimental data, where D varied from 10 cm to 35 cm, and h/D varied from 0 to 2.0.

A model of the axial plume temperature profile of rectangular pool fires dominated by convection under different atmospheric pressures and aspect ratios

This paper experimentally studied the axial plume temperature profile of heptane pool fires dominated by convection under different atmospheric pressures and aspect ratios. Results indicate that McCaffrey's axial temperature model in the plume region is not applicable at low-pressure conditions. The Gaussian plume model proposed by Tang et al. was verified based on the experiments of 36 cm2 pool fires, which are dominated by conduction, for different atmospheric pressures and aspect ratios. By mathematical derivation of the plume mass flow rate of pool fires, the relationship between the air entrainment coefficient and atmospheric pressure was obtained, and the experimental results of the air entrainment coefficient with different pressures can be well correlated with the analytical model. Finally, by introducing the air entrainment coefficient and temperature decay factor, a new axial plume temperature model for pool fires dominated by convection was developed, considering different atmospheric pressures and pool aspect ratios, which shows a good agreement with experimental results. This work can provide some good references for the fire safety of pool fires related to liquid fuel leakage.

P/N/S flame retardant based on DOPS-triazine groups for improving the flame retardancy, char formation properties and mechanical properties of epoxy resin

As epoxy resins (EPs) are widely used in adhesives, electronic packaging materials and aerospace, it is essential to construct new and efficient flame-retardant EP systems to reduce the risk of fire caused by their flammability. In this study, the condensation reaction of melamine (MEL) and 4-hydroxybenzaldehyde (PHBA) produced the intermediate melamine Schiff base (MSB), which was then successfully synthesized with 9,10-dihydro-9-oxa-10-phospha- phenanthrene-10-sulfide (DOPS) by addition reaction to produce a DOPS-triazine intumescent flame retardant MPD containing a novel structure of P/N/S, and applied to fabricate high-performance EP/MPD. As expected, the MPD has good flame-retardant properties due to the synergistic effect of DOPS groups and triazine groups. The thermoset resin EP/MPD passes the UL-94 V-0 test with the addition of only 7.5 % MPD and has a high LOI value of 32.7 %, which is 47.3 % higher than that of pure EP. In addition, the peak heat release rate (PHRR), total heat release (THR) and fire growth rate (FIGRA) of EP/MPD-12.5 % decreased by 33.9 %, 67.7 %, and 65.8 %, respectively, compared with that of pure EP. From the viewpoint of the char formation performance, the expansion height of the char residue of EP/MPD after combustion increased significantly up to 5.6 cm, which was over three times greater than the pure EP value. Moreover, the appropriate amount of MPD can effectively improve the flexural and impact strengths of EP thermosets. This study provides a new idea for the preparation of high-performance flame retardant MPD without affecting the mechanical properties of EP.

Characterizing burning behaviour of convection-controlled pool fires at sub-atmospheric pressure by stagnation theory

Pool fires play a critical role in examining the burning behaviour of diffusion flames and are sensitive to changes in scale and environmental conditions. Understanding the evolution of pool fires under low-pressure conditions, common in plateau or flight scenarios, is essential for both fire safety and energy utilization. This study investigates the effects of pressure on pool fires through a series of small-scale experiments carried out in a pressure chamber that provides stable conditions ranging from 95 kPa to 40 kPa. Pool scales between 7 cm and 16 cm were examined, a range dominated by convective heat transfer. Methanol and heptane were chosen to discern fuel-specific variations in burning behaviour under decreased pressure. The findings demonstrate an increase in the axial flame temperature with reducing pressure, while radiative output exhibits an inverse relationship with pressure. Additionally, convective heat transfer toward surroundings appears to rise with decreasing pressure. A modified stagnation theory solution is proposed to model the mass burning rate of convection-controlled pool fires under low pressure, which shows satisfactory agreement with the experimental data. This research could potentially contribute to the comprehension of pool fires and the safety of energy in sub-atmospheric pressure conditions in the future.

ANALYSIS OF THE APPLICATION OF AIRCRAFT INSTALLATIONS AND THE PROSPECTS OF THEIR MODERNIZATION

On the battlefield, the Ukrainian military uses towed anti-aircraft guns such as the S-60, which are still effective when used against ground targets. 57-mm anti-aircraft artillery systems are currently ineffective against modern air targets such as combat aircraft, drones and attack helicopters. But taking into account the caliber of the anti-aircraft installation, it can be used not only for its intended purpose, but also for firing at manpower and lightly armored vehicles with direct fire, and not only that. S-60 ammunition is powerful due to its caliber and sufficient rate of fire. When installing these guns on the chassis of trucks, it turns them into mobile self-propelled artillery installations and quite versatile and easy-to-use weapons. Anti-aircraft guns began to enter the ranks of the Armed Forces of Ukraine from storage bases not only of their own stocks, but also from partner countries. Ukrainian soldiers continue to use such weapons on the battlefield, their use is effective and convenient. Keywords: towed anti-aircraft installation, automatic cannon, barrel, bolt, projectile.

Fatal structure fire classification from building fire data using machine learning

PurposeThis study aims to develop a machine learning model to detect structure fire fatalities using a dataset comprising 11,341 cases from 2011 to 2019.Design/methodology/approachExploratory data analysis (EDA) was conducted prior to modelling, in which ten machine learning models were experimented with.FindingsThe main fatal structure fire risk factors were fires originating from bedrooms, living areas and the cooking/dining areas. The highest fatality rate (20.69%) was reported for fires ignited due to bedding (23.43%), despite a low fire incident rate (3.50%). Using 21 structure fire features, Random Forest (RF) yielded the best detection performance with 86% accuracy, followed by Decision Tree (DT) with bagging (accuracy = 84.7%).Research limitations/practical implicationsLimitations of the study are pertaining to data quality and grouping of categories in the data pre-processing stage, which could affect the performance of the models.Originality/valueThe study is the first of its kind to manipulate risk factors to detect fatal structure classification, particularly focussing on structure fire fatalities. Most of the previous studies examined the importance of fire risk factors and their relationship to the fire risk level.

Study of temperature distribution and smoke movement by mobile ventilation during emergency rescue in tunnel fires

Mobile ventilation unit (MVU), as a convenient and maneuverable ventilation method, can provide forced airflow for emergency ventilation to reduce tunnel fire risk. Compared with the conventional natural ventilation and mechanical ventilation, this mobile ventilation method plays a crucial role in the current tunnel fire emergency rescue. To explore the effects of MVU on the temperature or smoke spread in tunnel fires, Computational Fluid Dynamics simulation, validated by the previous experimental data, is applied in the current study. A series of tests are conducted with fire heat release rate of 1–30 MW and MVU fan flow being up to 3 × 105 m3/h. The results show the maximum tunnel ceiling temperature presents exponential attenuation with increasing fan flow and its relational expression with fan flow and fire size is proposed. Furthermore, the temperature decay distribution between upstream and downstream area is obviously different and a new coefficient γ is imported to represent the difference by connecting the fan flow and fire size. Moreover, the smoke backflow length theoretical equation in the upstream area is obtained, which can provide effective guidance to tunnel fire emergency rescue with MVU.

Benign design of intumescent fire protection coatings for steel structures containing biomass humic acid as carbon source

The application of biomass materials in engineering has received a great deal of attention. In this work, a new eco-friendly biomass-based intumescent coating, composed of natural and sustainable biomass humic acid (HA), ammonium polyphosphate (APP), melamine (MEL), and zinc borate (ZB), was developed to endow steel structures with excellent fire resistance and fire retardancy. When exposed to a butane torch, the intumescent coating (1.5 mm thickness) reduced the maximum temperature observed on the backside of a 3 mm thick steel plate by over 350 °C. Moreover, the cone calorimeter results showed that thanks to the formation of an extremely intumescent and dense char layer, the peak heat release rate (pHRR) and total heat release (THR) of intumescent coatings (S5) were reduced by 86 % and 61 %, respectively, as compared to that of the control epoxy coating, meanwhile, significant reductions in fire growth rate (FIGRA, −89 %) and maximum average rate of heat emission (MARHE, −86 %) were also observed, suggesting that 2 wt% ZB loading is required to achieve optimal level of fire resistance and fire retardancy. Furthermore, the mechanism of action was elucidated by SEM-EDX, FTIR, Raman, and XRD analyses. Results revealed that the combination of APP, MEL, HA, and ZB promoted the formation of a continuous and cohesive graphitized intumescent char layer on the surface of the steel plate, reinforced by borophosphate and zinc-containing species, which effectively prevents the transfer of heat and fuel, thereby enhancing the fire resistance and fire retardancy of the intumescent coating. This eco-friendly intumescent coating provides a strategy for developing new green fire protection systems using widely available, low-cost biomass materials without using hazardous ingredients.

Study on the double effect of the tunnel slope on the fire induced smoke back-layering distance in naturally ventilated inclined tunnels

This study focuses on the smoke back-layering distance (BLD), a crucial feature during a tunnel fire, in naturally ventilated inclined tunnels. It is explained, using a theoretical analysis as well as CFD simulations, that the tunnel slope has a double impact on the smoke BLD, through the fire-induced buoyancy: it naturally induces inlet airflow, but it also induces natural resistance against smoke downward flow. It is illustrated that, for a fire in a tunnel with inclination, this ‘buoyancy resistance’ results in a smoke BLD that is largely independent of the fire heat release rate. In horizontal or downward inclined tunnels, the natural buoyancy does not result in a limited smoke BLD. The effect of the inlet airflow can be characterized by a Froude number and the buoyancy resistance effect results in a newly defined dimensionless smoke BLD, based on the tunnel height, length and slope. A novel expression is proposed for the smoke BLD in inclined naturally ventilated tunnels, based on the CFD simulation results. It is validated by comparison to experimental data.

Numerical study on upstream smoke propagation and induced airflow velocity in a tilted channel under natural ventilation

A series of fire simulations were executed to explore the upstream smoke propagation characteristics and induced airflow velocity in tilted channels under natural ventilation. The channel slope ranging from horizontal to 58% (30°) and five heat release rates were used. Simulative results indicate that the airflow introduced by stack effect can enable the upstream smoke spread to reach sub-critical, critical and super-critical states without forced longitudinal ventilation. Meanwhile, taking the effect of fire heat release rate and height difference between the fire source and the upper portal into account, a piecewise function is developed to estimate the induced airflow velocity. It is found that when Ld∗·Q∗0.2 is less than or equal to 1.05, the airflow velocity increases exponentially with the variety of dimensionless elevation difference, but slowly rises logarithmically when Ld∗·Q∗0.2 is greater than 1.05. Besides, for scenarios in the sub-critical state, the relationship between the induced airflow velocity and the upstream smoke backflow length is revealed, which demonstrates that the dimensionless reverse flow length is in inverse proportion to the 1.5 power of dimensionless airflow velocity. For scenarios in the critical and super-critical states, there is still smoke backflow upstream of the fire source at the early period of a fire. And the disappearing time of smoke backflow reduces exponentially with the increase of heat release rate and elevation difference. Based on dimensional analysis and simulative data, a novel predictive model for the backflow disappearing time is proposed.

Electric vehicle fire risk assessment framework using Fault Tree Analysis.

In the near future, the rapid adoption of electric vehicles is inevitable, driven by environmental concerns and climate change awareness. However, this progressive trend also brings forth safety concerns and hazards, notably regarding the risk of EV fires, which have garnered significant media attention. This necessitates the need to study for comprehensive fire risk assessment strategies aimed at preventing and mitigating such incidents. This study presents a framework for assessing fire risks in EVs using Fault Tree Analysis (FTA). By integrating disparate data sources into a unified dataset, the proposed methodology offers a holistic approach to understanding potential hazards. The study embarked on a comprehensive exploration of EV fire causes through qualitative FTA. Through this approach, the work discerned five major causes: human factors, vehicle factors, management factors, external factors, and unknown factors. Using a meticulous weighted average approach, the annual EV fire frequency for each country was deduced, revealing an average annual EV fire rate of 2.44 × 10 -4 fires per registered EV. This metric provides a significant benchmark, reflecting both the probability and inherent risk of such incidents. However, uncertainties in data quality and reporting discrepancies highlight the imperative of continued research. As EV adoption surges, this study underscores the importance of comprehensive, data-driven insights for proactive risk management, emphasizing the necessity for vigilant and adaptive strategies. The findings emphasize the pivotal role of this assessment in shaping response strategies, particularly for first responders dealing with EV fires. In essence, this research not only elevates the understanding of EV fire risks but also offer a foundation for future safety measures and policies in the domain.