Search Results (1,169)

Building materials’ fire properties directly affect the fire risk of buildings. Ignition, the initiating event of any building fire, occurs when a heat source ignites surrounding combustible materials. Although several parameters—such as the Thermal Response Parameter (TRP), thermal inertia, ignition temperature, ignition time, critical heat flux (CHF), and heat of combustion—have been used to characterize ignition behavior, a unified metric capable of representing overall ignitability under diverse and often unknown and unintended heat source (UHS) patterns is generally lacking. To address this gap, we propose a new method to evaluate material ignitability by generalizing UHS patterns and linking them to known or readily obtainable material properties, including ignition temperature and thermal inertia. The UHS patterns are represented using lognormal distributions for both exposure duration and incident heat flux (IHF), reflecting conditions that may occur in real buildings. Monte Carlo simulations are employed to generate a large number of heat exposure events from these UHS patterns, enabling statistical determination of material ignitability. The method applies to both thermally thick and thermally thin materials, with a simple expression provided to determine the critical thickness separating these behaviors. Sensitivity analysis demonstrates that the ignitability metric is robust with respect to variations in the lognormal distribution parameters. The proposed ignitability metric provides a general measure of a material’s susceptibility to ignition under typical building fire scenarios and enables relative comparison of fire risk for buildings differing only in the materials adopted. Full article

The transition toward sustainable aviation fuels requires dedicated experimental platforms capable of evaluating alternative fuels under realistic propulsion conditions. This study presents the development and laboratory experimental validation of a modular testing installation designed for sustainable fuels derived from plastic waste pyrolysis, intended for aerospace engine applications. The proposed system is conceived as an integrated small-scale gas turbine assembly that reproduces the functional characteristics of a jet engine and enables controlled laboratory investigations of dynamic behavior, combustion stability, and performance. The installation comprises a compressor, annular combustion chamber, and turbine mounted on a common shaft, along with a fully autonomous fuel supply system equipped with electronically controlled pumping, safety devices, and thermal conditioning of the fuel mixture via an attached Stirling engine. Combustion processes are continuously evaluated using an exhaust gas analysis system to assess fuel composition and combustion quality, while a high-speed camera operating at 50,000 fps enables detailed visualization of flame stability. Operating parameters, including temperatures, pressures, rotational speed, mass flow rates, and thrust, are monitored and recorded through an integrated control and data acquisition system with real-time analysis capabilities. Experimental results demonstrate stable operation and reliable ignition using alternative fuel mixtures, confirming the suitability of the modular installation as a versatile research platform for the assessment and comparative analysis of sustainable aerospace fuels. Full article

Methane oxy-combustion is a promising carbon capture pathway due to the high CO₂ concentration in the exhaust; however, combustion in pure oxygen produces excessively high flame temperatures that impair ignition and operational stability. To mitigate these effects, steam dilution is commonly applied, but it significantly prolongs ignition delay time (IDT). To address these limitations, hydrogen enrichment is proposed as a reactivity-enhancement strategy. The objective of this study is to quantify the combined effects of steam dilution and hydrogen enrichment on ignition behaviour, carbon species formation, and flame temperature in methane oxy-combustion, considering both ignition onset and equilibrium combustion states. A detailed numerical investigation is conducted using zero-dimensional constant-pressure simulations with detailed chemical kinetics implemented in Cantera, formulated in mixture-fraction space. IDT, CO/CO₂ formation, and adiabatic flame temperature are analysed over steam dilution levels of 0–40%, hydrogen enrichment up to 5% by mass, and initial temperatures between 1050 and 1200 K. The model is validated against experimental data for adiabatic flame temperature and key radical species. Results demonstrate that steam dilution effectively reduces the peak adiabatic flame temperature (by more than 300 K at 40% steam) and enhances the CO₂ mass fraction in the equilibrium state near the stoichiometric mixture fraction, but increases IDT by approximately 100–200% across the mixture-fraction range. Hydrogen enrichment strongly counteracts this inhibition, reducing IDT by up to one order of magnitude under high steam dilution (30–40%) while simultaneously suppressing CO. At the stoichiometric mixture fraction, H₂ addition decreases equilibrium CO₂ formation, indicating a trade-off between enhanced ignition reactivity and ultimate carbon conversion under equilibrium conditions. The use of steam dilution as a temperature-control strategy and hydrogen enrichment as a reactivity enhancer identifies a favourable mixture-fraction window. Full article

This study explores the viability of condensate petroleum, an ultra-light hydrocarbon derived from natural gas production, as an alternative diesel engine fuel. The researchers tested six different fuel blends, increasing the condensate volume by 10% increments, in a compression ignition engine under three distinct load conditions (25%, 50%, and 75%) to evaluate both combustion characteristics and emission performance. The results demonstrate that condensate blends significantly enhance key combustion parameters. The heat release rate, in-cylinder pressure, and in-cylinder temperature all increased, with the highest heat release rate improvement of 35.6% observed at a 75% load using a 60% condensate petroleum blend. However, increasing the condensate ratio also extended ignition delay times and raised the ringing intensity, which peaked with a 34.7% increase at a 25% load. Brake thermal efficiency improved at lower and medium loads—achieving a maximum 11.2% increase with the 50% condensate petroleum blend at 50% load—but decreased when the engine reached 75% load. In terms of environmental impact, the condensate blends proved largely beneficial. Carbon monoxide emissions dropped by 57.9% (at 75% load, 60% condensate petroleum), smoke opacity decreased by 72.6% (at 25% load, 40% condensate petroleum), and hydrocarbons fell by 34.4% (at 50% load, 60% condensate petroleum). The primary drawback was that nitrogen oxide emissions worsened, increasing by 20.4% at 75% load with the 50% condensate petroleum blend. Overall, the study concludes that the effects of condensate petroleum are highly acceptable, making it a promising alternative fuel and additive for diesel engines. Full article

To address the limitations of existing NH₃/H₂ combustion mechanisms, laminar flame speeds of NH₃/H₂/air mixtures were measured using the heat flux method over a range of equivalence ratios from 0.7 to 1.6 at different blending ratios. The results indicate that current mechanisms exhibit large prediction errors under fuel-rich conditions. Subsequently, based on the original mechanism, the pre-exponential factors of 13 key reactions were optimized using a particle swarm optimization algorithm, leading to the development of a new NH₃/H₂ chemical kinetic mechanism. The optimized mechanism not only improves the prediction of laminar flame speeds for NH₃/H₂/air mixtures but also significantly enhances accuracy in the fuel-rich region. In addition, it accurately predicts the ignition delay times of NH₃/H₂ and reliably reproduces the concentrations of H₂O, NH₃, NO, and N₂O under low-equivalence-ratio conditions. Although the optimized mechanism was not specifically developed for pure NH₃ or pure H₂ fuels, it still performs well in describing their combustion characteristics. Overall, the optimized mechanism provides reliable predictions for both the laminar flame speeds and ignition delay times of NH₃/H₂ mixtures. Full article

Hydrogen combustion is known to be fast compared to traditional hydrocarbon fuels. The fast combustion leads to a higher thermal efficiency. In this research a 600 cc single cylinder hydrogen engine was tested at 1250 rpm, lambda = 2 and 3, and three load levels (load was represented by Manifold Absolute Pressure (MAP); MAPs tested were 75, 95 and 120 kPa) and compared to operation with gasoline and propane. The fast burn duration (Mass Fraction Burnt MFB10% to MFB90%) and the MFB 50% were determined and analyzed. The hydrogen MFB50% location for Minimum Timing for Best Torque (MBT) was found to occur at around the typical 8 Crank Angle Degrees (CADs) After Top Dead Center (ATDC). Measurements of ignition delay based on the fast data direct measurement of spark ignition coil current drop to the change in polarity of net heat release are presented. With shifts towards direct injection and higher injection pressures, consideration was given to the hydrogen pressurization penalty, where it was calculated that pressurizing hydrogen to 100 bar at the flow required for lambda = 2 operation is 2.3 bar, i.e., higher than the Friction Mean Effective Pressure (FMEP)! Furthermore, hydrogen is widely cited to have a higher heat loss than typical hydrocarbon fuels. In this paper, detailed analyses at lambda 2 and lambda 3 showed that hydrogen in fact has lower heat losses. Full article

To quantitatively elucidate the effects of overload current on the ignition and burning hazards of polyethylene-insulated wires, 2.5 mm² polyethylene-insulated copper wires used commercially were tested in an electrical fire fault simulation system. Experiments were conducted to study the evolution of overloads, ignition, and burning. The entire process, from insulation smoking and ignition to sustained burning and final extinction driven by wire fusing, was recorded using synchronized digital and high-speed imaging. Video-based measurements were used to extract the following: smoking emission duration, ignition time, burning duration, maximum flame height, and segmented flame width. The results show that stable ignition and sustained burning occur when the overload current is greater than or equal to 180 A. As the current increases, ignition occurs earlier, while the smoking stage becomes shorter but exhibits nonmonotonic fluctuations. The burning duration shows a staged response. It first increases, then decreases toward a relatively stable level. This reflects the competition between enhanced Joule heating and accelerated wire melting and fusing. Maximum flame height and segmented flame width vary nonmonotonically with current, and the segmented flame width peaks at 200 A. A multi-indicator fire hazard evaluation framework was established and an entropy-weight TOPSIS method was applied to integrate the quantification and ranking. The overall fire hazard is greatest at 200 A. These findings provide experimental insight into overload-induced ignition and combustion behavior and contribute to a quantitative understanding of fire hazard evolution in overloaded electrical wires. Full article

This study experimentally investigated the ignition and combustion characteristics of marine gas oil as a pilot fuel in dual-fuel marine engines using a constant-volume combustion chamber. In-cylinder temperature, pressure, and injection duration were the primary experimental variables. Results showed that temperature is the dominant factor governing ignition delay: increasing temperature from 520 °C to 580 °C reduced ID by 46.7% and its standard deviation by 62.8%. Increasing pressure shortened ID by 24.5% and reduced variability by 28.8%. In contrast, injection duration minimally affected ignition timing but increased accumulated heat release and maximum heat release rate by 37% and 20%, respectively. The time interval between ID and main combustion delay remained constant at approximately 0.30 ms across all conditions, indicating simultaneous advancement of ignition and combustion development. These findings demonstrate that ignition timing control (via temperature management) and combustion intensity control (via injection quantity) can be independently optimized, providing fundamental experimental data for the development of robust combustion-control strategies in dual-fuel marine engines. Full article

This study investigates the influence of highly thermally conductive coatings on the combustion thresholds of a TC4 titanium alloy, aiming to address the flame-retardant protection requirements for titanium alloys. The findings reveal that, in terms of combustion thermodynamics, as the thickness of the copper coating increases from 100 μm to 300 μm, the critical ignition power rises by 125–170 W compared to the substrate (235 W). Additionally, the critical oxygen pressure increases by 0.21–0.51 MPa relative to the substrate (0.03 MPa), and the ignition temperature is elevated by 119–184 K above that of the substrate (848.80 K). This phenomenon is primarily due to the high thermal diffusivity of copper. Increased coating thickness further enhances heat dissipation, significantly suppressing the local heat accumulation rate and thereby improving the coating’s combustion resistance. In terms of combustion kinetics, under fixed experimental conditions, the copper coating extends the ignition delay time by 0.670 s and reduces the combustion propagation rate by approximately 21% compared to the substrate (26.772 mm/s). The post-combustion microstructural analysis indicates that during the reaction process, the copper coating forms a TiCu₂Al-type intermetallic compound (Ti_0.5Al_0.5)Cu. This structure exerts an “anchoring” effect on the substrate material, decreases the Ti/O reaction efficiency, and consequently achieves effective flame retardancy. These findings inform the subsequent design and optimization of copper-based abradable coatings with enhanced combustion resistance. Full article

In the European context of a planned transition to a zero-carbon future, the initial question at the origin of this study was to assess the energy and environmental performance of a retrofitted diesel engine converted to stoichiometric spark ignition (SI) operation using two gaseous and sustainable fuels: natural gas (NG) and liquefied petroleum gas (LPG). Further to a parametric study regarding the spark advance and injection timing, this paper delivers experimental results obtained at the engine test bed for different operating points, which are compared with the results of a baseline commercial gasoline engine. The results showed a clear improvement in terms of CO₂ for the NG (especially) and LPG with a knock-free operation with respect to gasoline. Cyclic variability also improved. As for the engine-out pollutants, in the case of carbon monoxide (CO) and particle number (PN), the results are in favor of gaseous fuels. Concerning the nitrogen oxides (NOx), as expected, a higher emission was obtained with the retrofitted engine due to its higher compression ratio. Full article

Underground coal fires (UCFs) pose a persistent environmental and economic threat to both the built and natural worlds. In Colorado, 38 known coal fires are currently monitored by the Colorado Division of Reclamation, Mining, and Safety, many of which are in the immediate vicinity of communities and transportation infrastructure. The Axial underground coal mine fire in northwestern Colorado has been active for over 70 years and has a documented history of surface impacts, including wildfire ignition and UCF-induced slope instability near a major highway corridor. Subsurface investigations indicate active combustion in multiple coal seams, contributing to complex and evolving surface deformation. Unmanned Aerial System (UAS)-based optical surveys acquired between 2018 and 2025 were used to assess terrain changes and slope instability at the Axial site. Structure-from-motion photogrammetry was used to generate three-dimensional point clouds and orthomosaics, and surface deformation was quantified using the Multiscale Model-to-Model Cloud Comparison (M3C2) algorithm. Orthomosaic products were additionally evaluated to characterize the development of geomorphic features and cross-validate the interpretation of M3C2-derived deformation patterns. Repeat UAS surveys effectively identified changes in unstable and hazardous terrain caused by UCFs. Results reveal progressive subsidence, fracture development, and localized slope instability associated with ongoing subsurface combustion. The findings provide critical information for risk mitigation and illustrate both the capabilities and challenges of using UAS photogrammetry for long-term monitoring of geohazards associated with legacy coal mine fires. The study further emphasizes the importance of georeferencing strategies, including ground control points and real-time kinematic positioning, to ensure consistent and reliable multi-temporal change detection. Full article

Combustion duration is a fire behaviour feature relevant for both the effects and management of fire. We burned small-scale laboratory fuel beds (n = 135) of eight fuel types and developed empirical models to describe variation in flame residence and burn-out times, and fuel mass fraction loss rates during flaming and non-flaming combustion; each fuel sample was ignited at once and burned as a pile. Surface area-to-mass ratio of the fuel particles, by itself, allowed accurate prediction of all combustion properties with better performance than surface area-to-volume ratio. Fuel bed structure was also shown to have an influence, fuel load being the variable that further improved all predictions. This work provides evidence that surface area-to-mass ratio is an adequate descriptor of the combustion characteristics of forest fuel beds. Our expectation is that this approach will assist future modelling efforts to obtain simple empirical models to predict the combustion features of free-spreading fires in a wide range of vegetation types. Full article

Early wildfire smoke detection is critical for preventing small ignitions from escalating into large-scale fires, yet early-stage smoke plumes are often faint, low-contrast, and spatially small. When full-resolution frames are resized to satisfy fixed-input detector architectures and enable efficient batched GPU inference, these subtle cues are further diminished, leading to missed detections and unreliable scores near deployment thresholds. Existing remedies such as multi-scale inference, slicing/tiling, or super-resolution could improve sensitivity, but typically incur substantial overhead from multiple forward passes or added network components, limiting real-time use on resource-constrained platforms. To mitigate these challenges, we propose a composite multi-resolution detection framework that improves sensitivity to small smoke regions while maintaining single-pass inference. Motivated by the fact that most operational wildfire monitoring systems rely on Unmanned Aerial Vehicle (UAV) platforms and mountain-top Closed-Circuit Television (CCTV) systems surveillance, their wide-field imagery typically contains a large sky region above the horizon where early smoke is most likely to first become visible. Accordingly, crop placement is guided by a skyline prior that prioritizes this high-probability sky band while retaining the remaining scene for global context. A dynamic compositing stage stacks a global view with a high-resolution, sky-aligned band into a standard square detector input, preserving context with minimal added cost. Detections from the two views are reconciled via coordinate restoration and non-maximum suppression. For deployment, a lightweight second-stage classifier selectively re-evaluates low-confidence detections to stabilize decisions near a fixed operating threshold without retraining the detector. Compared to the baseline detector, our approach improves detection performance on the Early Smoke dataset, achieving gains of +4.6 percentage points in AP @0.5:0.95, +3.4 percentage points in AP @0.5, +2.9 percentage points in precision, +5.3 percentage points in recall, and +4.3 percentage points in F1-score. Full article

Climate change has intensified wildfire risk, creating an urgent need for integrated, data-driven tools that connect forest operations with fuel-reduction strategies. This paper introduces a real-time IoT-enabled Decision Support System (DSS) that unifies wood traceability with optimization–simulation planning for biomass collection and processing. The system captures detailed operational data from harvesting, transportation, and processing through IoT devices and industry formats, enabling the continuous monitoring of wood flows and precise estimation of biomass residues that directly contribute to wildfire fuel loads. The DSS transforms these real-time streams into actionable planning outputs through an optimization–simulation module that generates efficient biomass harvesting and processing schedules while evaluating their robustness under wildfire-related constraints. By linking wood traceability with biomass logistics, the system provides the missing operational bridge between forest management decisions and wildfire-risk mitigation. Results show that the DSS not only improves operational efficiency but also enhances resilience by supporting risk-aware planning, prioritizing high-exposure areas, and reducing the accumulation of hazardous biomass. These insights demonstrate how digital traceability and robust planning can work together to lower ignition potential while maintaining service levels and operational continuity. Overall, this work presents a practical and scalable solution that strengthens forest supply chain resilience and provides a new pathway for integrating wildfire-risk mitigation into everyday operational planning. Full article

The paper presents computational fluid dynamics (CFD) simulations of a propane-fueled and under-ventilated fire in a reduced-scale corridor-like enclosure. The fire source is positioned at the closed end of the corridor. Due to the restricted inflow of oxygen, the flame lifts off from the gaseous burner and travels—along with unburned fuel—all the way to the open doorway at the opposite end of the corridor. Oxygen calorimetry shows that a quasi-steady state plateau is established, during which the heat release rate (HRR) within the enclosure is equal to the theoretical value ${\dot{Q}}_{in}=1500 A_o\sqrt{H_o}$ where $A_o\sqrt{H_o}$ is the ventilation factor. Then, external flaming occurs. CFD simulations with the Fire Dynamics Simulator (FDS) captured well the overall flame dynamics. More specifically, the HRR plateau is well predicted, provided that the actual autoignition temperature of propane, AIT = 450 °C, is prescribed instead of the default AIT = −273 °C. However, the occurrence time of external flaming remains significantly underestimated and is better predicted by setting AIT = 600 °C. This aspect of the modelling, linked to extinction and (re-)ignition, remains to be further investigated in the future. Full article