Search Results (570)

Electrical cable insulation, mainly composed of polymeric materials, progressively deteriorates under thermal, electrical, mechanical, and environmental stress factors. This degradation reduces dielectric strength, thermal stability, and mechanical integrity, thereby increasing susceptibility to failure modes such as partial discharges, arcing, and surface tracking—recognized precursors of fire ignition. This review consolidates current knowledge on the degradation pathways of cable insulation and their direct link to fire hazards. Emphasis is placed on mechanisms including thermal-oxidative aging, electrical treeing, surface tracking, and thermal conductivity decline, as well as the complex interactions introduced by flame-retardant additives. A bibliometric analysis of 217 publications reveals strong clustering around material degradation phenomena, while underlining underexplored areas such as ignition mechanisms, diagnostic monitoring, and system-level fire modeling. Comparative experimental findings further demonstrate how insulation aging modifies ignition thresholds, heat release rates, and smoke toxicity. By integrating perspectives from materials science, electrical engineering, and fire dynamics, this review establishes the nexus between aging mechanisms and fire hazards. Full article

To address the challenges of short dwell time near top dead center (TDC) and uneven heat release, this paper presents a comprehensive analysis of the effects of different ignition schemes on combustion characteristics, flame formation and development, and emissions. A three-dimensional model of coupled reaction’s kinetic mechanism was established using Converge 3.0 and validated by experimental data. The results show that ignition position, whether synchronous or asynchronous changes, significantly influence pressure. The pressure in synchronous cases can reach up to 62.5 bar, representing a 10.8% increase, exhibiting a distinct upward trend with advanced ignition position. In asynchronous cases, the pressure variation shows a distinct nonlinear characteristic due to the negative effects of in-cylinder airflow and flame core collision. When the ignition position is advanced, the ignition delay increases for both synchronous and asynchronous strategies. However, for synchronous cases, the combustion duration is reduced by up to 1.5 ms, whereas for asynchronous cases, the reduction is only 0.135 ms. Regardless of the schemes, the layout and the strong counterclockwise swirl lead to the flame core gradually developing from right to left, ultimately engulfing the left-side flame core. Compared then to that case, the left and right flame kernels may collide prematurely, leading to incomplete local combustion and consequently reducing combustion efficiency. Compared to synchronous changes, the emission differences during asynchronous changes are smaller and maintained at a relatively low level. Full article

Fire spotting (FS), the process by which firebrands are lofted, transported, and ignite new fires ahead of the main flame front, plays a critical role in escalating extreme wildfire events. This systematic literature review (SLR) analyzes peer-reviewed articles and book chapters published in English from 2000 to 2023 to assess the evolution of FS models, identify prevailing methodologies, and highlight existing gaps. Following a PRISMA-guided approach, 102 studies were selected from Scopus, Web of Science, and Google Scholar, with searches conducted up to December 2023. The results indicate a marked increase in scientific interest after 2010. Thematic and bibliometric analyses reveal a dominant research focus on integrating the FS model within existing and new fire spread models, as well as empirical research and individual FS phases, particularly firebrand transport and ignition. However, generation and ignition FS phases, physics-based FS models (encompassing all FS phases), and integrated operational models remain underexplored. Modeling strategies have advanced from empirical and semi-empirical approaches to machine learning and physical-mechanistic simulations. Despite advancements, most models still struggle to replicate the stochastic and nonlinear nature of spotting. Geographically, research is concentrated in the United States, Australia, and parts of Europe, with notable gaps in representation across the Global South. This review underscores the need for interdisciplinary, data-driven, and regionally inclusive approaches to improve the predictive accuracy and operational applicability of FS models under future climate scenarios. Full article

Under electrical overload conditions, the molten dripping of thermoplastic wire insulation materials—particularly crosslinked polyethylene (XLPE)—poses a severe fire hazard and significantly complicates fire prevention and control. This study systematically investigated the formation mechanism, periodic characteristics, and flame interaction behavior of molten dripping in XLPE-insulated wires subjected to varying overload currents (0–80 A). Experiments were conducted using a custom-designed test platform equipped with precise current regulation and high-resolution video imaging systems. Key dripping parameters—including the initial dripping time, dripping frequency, and period—were extracted and analyzed. The results indicate that increased current intensifies Joule heating within the conductor, accelerating the softening and pyrolysis of the insulation, thus resulting in earlier and more frequent dripping. A thermodynamic prediction model was developed to reveal the nonlinear coupling relationships between the dripping frequency, period, and current, which showed strong agreement with the experimental data, especially at high current levels. Further flame morphology analysis showed that molten dripping induced pronounced vertical flame disturbances, while the lateral flame spread remained relatively unchanged. This phenomenon promotes vertical flame propagation and can trigger multiple ignition points, thereby increasing the fire complexity and hazard. The study enhances our understanding of the coupling mechanisms between electrical loading and molten dripping behavior and provides theoretical and experimental foundations for fire-safe wire design and early-stage risk assessment. Full article

Syngas, a renewable fuel primarily composed of hydrogen and carbon monoxide, is emerging as a viable alternative to conventional fossil fuels in internal combustion engines (ICEs). Obtained mainly through the gasification of biomass and organic waste, syngas offers significant environmental benefits but also presents challenges due to its lower heating value and variable composition. This review establishes recent advances in understanding syngas combustion, chemical kinetics, and practical applications in spark-ignition (SI) and compression-ignition (CI) engines. Variability in syngas composition, dependent on feedstock and gasification conditions, strongly influences ignition behavior, flame stability, and emissions, demanding detailed kinetic models and adaptive engine control strategies. In SI engines, syngas can replace up to 100% of conventional fuel, typically at 20–30% reduced power output. CI engines generally require a pilot fuel representing 10–20% of total energy to start combustion, favoring dual-fuel (DF) operation for efficiency and emissions control. This work underlines the need to integrate advanced modelling approaches with experimental insights to optimize performance and meet emission targets. By addressing challenges of fuel variability and engine adaptation, syngas reveals promising potential as a clean fuel for future sustainable power generation and transport applications. Full article

Potential fire behavior varied significantly among tree species, directly influencing forest fire intensity and spread. To quantify these differences and evaluate species-specific fuel traits for fire management applications, this study conducted field surveys and sample collection in the Jin Dian Yuanbaoshan Forest Area, Kunming, Yunnan Province. Using a combustion bed experiment, we simulated the burning behavior of Acacia dealbata, Alnus nepalensis, and Pinus armandii under windless conditions, recording ignition time, extinction time, flame height, spread rate, and calculating fire intensity. Comparative analysis revealed: (1) Fire intensity ranking: P. armandii needles > A. dealbata leaves > P. armandii branches > A. nepalensis leaves > P. armandii bark > A. dealbata branches > A. nepalensis branches > A. dealbata bark > A. nepalensis bark; (2) The biological firebreaks composed of A. nepalensis and A. dealbata in Yuanbaoshan exhibited effective flame-retardant performance; (3) Coarse woody fuels negatively affected prescribed burning intensity and effectiveness. By quantifying fire behavior differences among these species, this study provides scientific support for fuel management and fire-resistant species selection in central Yunnan, while offering practical guidance for prescribed burning strategies in the Jin Dian Yuanbaoshan Forest Area. Full article

Ti150 has potential applications in aeroengine components. However, the lack of research on its flame resistance, combustion behavior, and mechanisms makes it difficult to assess the risk of “titanium fire” and leaves fire protection design without theoretical support. This study aimed to determine the combustion resistance of Ti150 and elucidate its combustion behavior and mechanisms to address these issues. Through comparative Promoted Ignition-Combustion (PIC) tests between Ti150 and TC11 alloys, microstructural characterization, and thermodynamic/kinetic analyses, the following conclusions were drawn. Ti150 alloy exhibited a higher critical oxygen pressure and a higher ignition temperature but a significantly faster burning velocity, compared with TC11 alloy. The relationship between pressure and ignition temperature was in good agreement with the modified Frank-Kamenetskii ignition model. The ignition activation energy of Ti150 alloy was determined to be 118.41 kJ/mol, which was approximately 21% higher than that of TC11 alloy (97.72 kJ/mol). Moreover, post-combustion microstructural observations of Ti150 alloy revealed a higher oxygen content in the melting zone and an enrichment of Zr at the solid–liquid interface, both of which contribute to the higher burning velocity of Ti150 alloy compared with TC11 alloy. Full article

Hydrogen is a promising alternative fuel for internal combustion engines due to its high specific energy, fast flame speed, and carbon-free combustion. In dual-fuel operation, it offers a practical route to reducing greenhouse gas emissions while remaining compatible with existing engine hardware. This work evaluates how the hydrogen energy substitution ratio (HSR = 50, 70, and 90%) influences spray dynamics, combustion characteristics, and emissions in a heavy-duty compression ignition engine. Simulations are validated against experiments and use a URANS RNG k–ε framework with a hybrid combustion model: the Eddy Dissipation Concept (EDC) coupled with detailed kinetics (111 species, 768 reactions) for auto-ignition and diffusion burning of diesel, and a G-equation for propagation of a hydrogen-rich premixed flame. The results reveal clear spray–combustion linkages. At HSR 50, the higher Weber number induces stronger breakup, yielding a smaller Sauter mean diameter and higher number-averaged droplet velocity; at HSR 90, the spray is more stable and less atomized, with larger droplets and a shorter vapor penetration length. Increasing the HSR reduces unburned hydrocarbons (UHCs) by more than 50% from HSR 50 to HSR 90 while modestly altering combustion phasing (a later CA50 and a shorter burn duration due to faster hydrogen flame propagation). The validated model provides a practical tool for optimizing dual-fuel settings and HSR–EGR–SOI trade-offs to balance efficiency and emissions. Full article

This study presents a novel approach to analysing the early stages of the combustion process by measuring the surface temperature of a kerosene droplet from its point of ignition through to its evaporation. An indium arsenide antimonide (InAsSb) photodiode-based infrared radiation thermometer (IRT), operating between 3 μm and 11 μm in wavelength, was designed to enable non-contact, low-temperature sensing with an acquisition time of 500 μs. Integrated with a data acquisition unit (DAQ), the instrument captures the transient combustion stages occurring below the droplet’s boiling point of 300 °C. The instrument was assessed against industry standards and demonstrated a measurement uncertainty of ±2 °C, confirming suitability within the performance bounds of commercial instrumentation. The IRT was deployed to measure the temperature of a kerosene droplet within an enclosed combustion chamber upon ignition, in direct comparison with a contact thermocouple. The instrument demonstrated its capability to measure the droplet’s surface temperature changes throughout its early-stage combustion. Furthermore, the wavelength specificity of the IRT eliminates thermal interference from the subsequent flame, a capability which contact thermocouples lack, thereby enabling measurement of the droplet’s temperature in isolation. This study focuses on single-droplet Jet A kerosene combustion under controlled conditions, using a transferable methodology adaptable to other fuels and environments. It supports the use of IRT for non-contact temperature measurement of fuel droplets and early-stage combustion, aiding fuel characterisation and the development of future fuels such as SAF. Full article

Xylenes are important components of gasoline fuels, and their hydrogen abstraction reactions are crucial in the consumption pathways of combustion processes. In existing models, rate constants for these reactions are commonly derived by estimation, which can introduce large uncertainties into models and lead to prediction deviations. In this study, the hydrogen abstraction reactions of three xylene isomers (p-xylene, m-xylene, and o-xylene) with hydrogen and hydroxyl radicals were investigated using quantum chemical methods. The high-precision CBS-QB3 method was used to perform a series of calculations, including structure optimization, frequency analysis, and energy calculations. Rate constants for all reactions were obtained using transition state theory with tunneling corrections and fitted to the three-parameter Arrhenius expression. The kinetic parameters of these reactions were updated in existing models of xylene. The integration of the updated rate constants into combustion models generally improves predictive accuracy, particularly for ignition delay times, CO₂ formation, and laminar flame speeds, although discrepancies remain for some species such as CO. Full article

The ammonia-n-heptane reaction mechanism is essential for simulation of the in-cylinder process for diesel-ignited ammonia engines. To gain insight into the differences in predictive performance among various ammonia-n-heptane reaction mechanisms, four mechanisms were comprehensively evaluated and analyzed based on the modeling of ignition, oxidation, laminar flame propagation and in-cylinder combustion processes. The result shows that only under high ammonia blending ratios and elevated temperatures are discrepancies in predicted ignition delay times observed among the studied reaction mechanisms. Regarding the oxidation process, on the whole, the concerned mechanisms can reasonably predict concentrations of reactants and complete combustion products. However, significant discrepancies exist among the mechanisms in predicting concentrations of intermediate species and other products. For laminar burning velocity, the modeled values from the studied mechanisms are consistent with experimental results under both fuel-lean and -rich conditions. The Wang mechanism exhibits significant deviations from the other three mechanisms in predicting reaction pathways of ammonia and n-heptane. From the perspective of reaction class, the studied mechanisms are similar to each other, to some extent, in the key reactions governing consumption of ammonia and n-heptane. For the engine simulation, the predicted in-cylinder pressure and temperature profiles show minimal variations across different reaction mechanisms. In conclusion, the Fang mechanism can be selected to understand more accurately ignition, oxidation and flame characteristics of ammonia-n-heptane mixtures, while to reduce the engineering computational cost of the engine simulation, the Wang mechanism tends to be a good choice. Full article

This paper presents a detailed analysis of the thermal and flammability properties of polylactide- (PLA) and poly(ethylene terephthalate)- (PET) based polymer blends with biofillers, such as calcium lignosulfonate (CLS), lignosulfonamide (SA) and lignosulfonate modified with tannic acid (BMT) and gallic acid (BMG). Calorimetric studies revealed the presence of two glass transitions, one cold crystallization temperature, and two melting points, confirming the partial immiscibility of the PLA and PET phases. The additives had different effects on the temperatures and ranges of phase transformations—BMT restricted PLA chain mobility, while CLS acted as a nucleating agent that promoted crystallization. Thermogravimetric analyses (TGA) analyses showed that the additives significantly affected the thermal stability under oxidizing conditions, some (e.g., BMG) lowered the onset degradation temperature, while the others (BMT, SA) increased the residual char content. The additives also altered combustion behavior; particularly BMG that most effectively reduced flammability, promoted char formation, and extended combustion time. CLS reduced PET flammability more effectively than PLA, especially at higher PET content (e.g., 65% reduction in PET for 2:1/CLS). SA inhibited only PLA combustion, with strong effects at higher PLA content (up to 76% reduction for 2:1/SA). BMT mainly reduced PET flammability (48% reduction in 1:1/BMT), while BMG inhibited PET more strongly at lower PET content (76% reduction for 2:1/BMG). The effect of each additive also depended on the PLA:PET ratio in the blend. FTIR analysis of the char residues revealed functional groups associated with decomposition products of carboxylic acids and aromatic esters. Ultimately, only blends containing BMT and BMG met the requirements for flammability class FV-1, while SA met FV-2 classification. BMG was the most effective additive, offering enhanced thermal stability, ignition delay, and durable char formation, making it a promising bio- based flame retardant for sustainable polyester materials. Full article

n-Pentanol, a promising biofuel, can reduce greenhouse gas emissions while remaining compatible with internal combustion engines. We present a reduced kinetic mechanism comprising 66 species and 292 reactions that captures both high- and low-temperature ignition and flame propagation dynamics for this fuel. The mechanism, developed by integrating a detailed n-pentanol sub-mechanism with the San Diego mechanism and applying sensitivity and steady-state approximations criteria as reduction strategies, accurately reproduces key phenomena, including the negative temperature coefficient behavior (NTC). Validation against experimental data for ignition delay times, laminar flame speeds, and speciation measurements in a jet-stirred reactor confirms its predictive capability across a wide range of conditions. Full article

The typical structure of an oblique detonation wave (ODW) consists of a leading shock wave followed by a coupled shock-flame complex. The distance from the leading shock’s originating point to the ignition onset is referred to as the induction length. This work numerically studies the induction length effect using a two-step induction-reaction kinetic model. Results reveal that the induction length governs the transition pattern of ODWs. By testing four distinct induction lengths, four ODW regimes are identified, including a prompt ODW, a delayed smooth ODW, a delayed abrupt ODW, and a delayed abrupt ODW with an upstream triple point in oscillatory motion. The mechanisms behind these regimes are analyzed in detail. Additionally, hysteresis is observed when the induction length decreases from a larger value, demonstrating that this phenomenon can be influenced by the kinetic process. Full article

As internal combustion engines (ICEs) remain dominant in maritime transport, reducing their greenhouse gas (GHG) emissions is critical to meeting IMO’s decarbonization targets. Ammonia (NH₃) has gained attention as a carbon-free fuel due to its zero CO₂ emissions and high hydrogen density. However, its low flame speed and high ignition temperature pose combustion challenges. This study investigates the combustion and emission performance of NH₃-diesel dual-fuel engines, applying Response Surface Methodology (RSM) for multi-objective optimization of key operating parameters: ammonia fraction (AF: 0–30%), engine speed (1200–1600 rpm), and altitude (0–2000 m). Experimental results reveal that increasing AF led to a reduction in Brake Thermal Efficiency (BTE) from 39.2% to 37.4%, while significantly decreasing NO_x emissions by 82%, Total hydrocarbon emissions (THC) by 61%, and CO₂ emissions by 36%. However, the ignition delay increased from 8.2 to 10.8 crank angle degrees (CAD) and unburned NH₃ exceeded 6500 ppm, indicating higher incomplete combustion risks at high AF. Analysis of variance (ANOVA) confirmed AF as the most influential factor, contributing up to 82.3% of the variability in unburned NH₃ and 53.6% in NO_x. The optimal operating point, identified via desirability analysis, was 20% AF at 1200 rpm and sea level altitude, achieving a BTE of 37.4%, NO_x of 457 ppm, and unburned NH₃ of 6386 ppm with a desirability index of 0.614. These findings suggest that controlled NH₃ addition, combined with proper speed tuning, can significantly reduce emissions while maintaining engine efficiency in dual-fuel configurations. Full article