Search Results (625)

Coal fires are a significant source of greenhouse gas emissions and ecological pollutants, yet their emission characteristics and carbon accounting remain poorly constrained. To reveal the pollutant generation characteristics and carbon emission levels of the typical underground coal fire area in Sulabulak, Xinjiang, this study integrated laboratory simulation, multi-source remote sensing inversion, and in situ field monitoring. Thermogravimetric analysis, a high-temperature tube furnace, HSC thermodynamic simulation, and multi-source remote sensing data from Landsat-8/9 and Sentinel-1A were employed to investigate the gaseous products and heavy metal migration mechanisms at different combustion stages, and to delineate the spatial extent of different combustion states in the fire area. A coal loss model was then constructed by coupling experimentally determined carbon emission factors with remote sensing-derived areas and was compared with an emission flux model based on field measurements. The results show that the coal oxidation process proceeds through three distinct stages, with indicator gas ratios (CO₂/CO and C₂H₄/C₂H₆) serving as effective indicators for combustion state identification. Heavy metal partitioning is governed by elemental volatility and redox conditions: As and Se partition predominantly into the gas phase, while Zn becomes enriched in fly ash. Remote sensing time series analysis documents continuous fire expansion accompanied by progressive surface subsidence. By cross-validating the indirect coal loss model (constrained by remote sensing area) against the direct emission flux model (constrained by field measurements), we estimate the current annual GHG emission of the Sulabulak fire area at approximately 0.65 × 10⁴ t CO₂ equivalent. This study proposes a coupled “micro-experiment–macro-remote sensing–field measurement” approach for carbon emission accounting, providing reliable data support for environmental pollution control and the development of carbon inventories for coal fires in arid regions. Full article

High-solar-reflectivity cladding materials are widely promoted to reduce cooling demand and mitigate urban heat island effects. However, in cold and mixed climates, their overall energy and carbon performance remains uncertain due to potential winter heating penalties and embodied carbon trade-offs. This study presents a comparative evaluation of energy use, annual operational carbon emissions, and material-level embodied carbon for high-reflectivity cladding applied to commercial buildings across representative Canadian climate zones. Dynamic simulations were conducted in EnergyPlus using a standardized warehouse archetype in Montreal, Toronto, and Vancouver, representing cold continental, mixed continental, and marine climates. Roof and wall solar reflectivity (albedo) was varied from 0.2 (baseline) to 0.8 (high reflectivity), while other envelope properties remained constant. Increasing reflectivity reduced annual cooling demand by approximately 15% in Montreal and Toronto and 20% in Vancouver, with the largest reductions during peak summer periods. However, reduced winter solar heat gains produced heating penalties, increasing total annual energy use by 1% in Montreal, 0.5% in Toronto, and less than 0.5% in Vancouver. Operational greenhouse gas emissions were calculated by converting simulated annual electricity and natural gas use into CO₂-equivalent emissions using provincial grid emission factors and combustion factors consistent with Environment and Climate Change Canada reporting. The results demonstrate the strong influence of regional energy supply on operational carbon outcomes. A cradle-to-gate (A1–A3) life cycle assessment quantified embodied carbon of representative cladding materials using Environmental Product Declarations and North American databases. Embodied carbon varied considerably: product-specific steel cladding manufactured in low-carbon electricity regions showed global warming potential as low as 1.76 kg CO₂e/kg, compared with industry averages exceeding 2.4 kg CO₂e/kg. Rather than performing a complete whole-life carbon assessment, this study comparatively evaluates annual operational carbon emissions and material-level embodied carbon to improve understanding of the energy and carbon implications of high-solar-reflectivity cladding materials in representative Canadian climates. The results demonstrate that climate conditions, envelope thermal performance, regional energy supply, and manufacturing pathways influence the environmental performance of cool envelope strategies. Full article

Active flow control actuators are critical for improving aerodynamic performance in applications such as aircraft lift enhancement, drag reduction, and maneuverability improvement. However, the plasma synthesis jet actuator (PSJA) is limited by the constraints of electric energy deposition, making it difficult to further improve the jet velocity and mass flow rate. Meanwhile, the jet velocity driven by combustion needs to be further increased. This study preliminarily investigated the characteristics of a combustion-driven SparkJet actuator through experiments; a combustion-driven SparkJet actuator integrates the advantages of plasma actuators and combustion-driven actuators. The actuator employs a continuous methane–air mixture supply ignited by spark discharge. High-speed shadowgraph imaging is used to characterize the jet flow field evolution. The effects of the cavity volume, normalized outlet diameter (d* = d/h), and equivalence ratio on jet performance are systematically examined. As the normalized outlet diameter increases from 0.666 to 1, the jet penetration distance and jet width increase with an increasing normalized outlet diameter, owing to the reduced boundary layer blockage effect at the orifice. However, when the normalized outlet diameter equals 1, both the jet penetration distance and jet width first increase and then decrease with increasing cavity volume; hence, the outlet diameter and cavity have an optimal size. At an equivalence ratio of mixture ≤1, increasing the methane flow rate enhances the volumetric chemical heat release rate, thereby monotonically improving the jet width and penetration distance. The combustion-driven actuator demonstrates a significantly higher jet velocity compared to a conventional plasma actuator under identical geometric parameters; the combustion reaction can effectively amplify the jet energy and velocity of the actuator. Moreover, the combustion-driven SparkJet actuator also has the same working frequency when the actuator volume is the same, indicating that the combustion process does not significantly extend the cycle time. The maximum jet velocity first increases and then decreases with increasing cavity volume; the reason that the maximum jet velocity first increases is that a larger volume results in a greater mixture mass and more released heat; it then decreases due to incomplete combustion occurring in large chambers. These results show that the design standards for the combustion-driven actuator are fundamentally different from those for the plasma actuator, and their optimal performance is related to not only electrical energy density but also combustion performance. The design parameters of the combustion-driven actuator can be optimized to maximize the jet front velocity. The experimental data in this article provides a reference for optimizing the performance of combustion-driven actuators. Full article

This study presents a gate-to-gate life cycle assessment (LCA) comparing the environmental impact of three torrefied municipal solid waste (MSW) energy sources (S1) solar photovoltaic (PV), (S2) grid electricity from India and (S3) biomass combustion. Experiments performed in a laboratory setting produced a yield of transitory MSW torrefaction of 28–32% at an input fuel energy of 2 kWh/kg at 200–300 °C for 30–60 min. The ReCiPe 2016 midpoints [Global Warming Potential (GWP); Human Toxicity Potential (HTP); Acidification Potential (AP); Particulate Matter Formation Potential (PMFP)] showed PV produced the least number of emissions (GWP = 0.0426 kg CO₂ equivalent; HTP = 0.00988 kg 1,4-DB equivalent), while grid power produced the greatest number of emissions (GWP = 2.2 kg CO₂ equivalent). Biomass produced intermediate results (GWP = 1.546 kg CO₂ equivalent). All sources had an average positive net energy ratio of approximately 2.78. The results indicate that integrating renewable energy sources significantly increases the environmental and social benefits of the torrefaction process. Additionally, the study provides a MS Excel-Based LCA framework to use when data are limited. Full article

Emission inventories for high-altitude Andean cities rely on sea-level certification cycles that misrepresent real-world combustion conditions. This study derives altitude-resolved emission factors (EFs) for light-duty gasoline vehicles across 0–4000 m a.s.l. in Ecuador using the purpose-built Andean Ecuador Driving Cycle (aedc), validated against naturalistic data via the Percentile Speed Vector metric (PSV_m10; IGS $=1.89$ vs. IGS $=2.30$ for the WLTC). Ten vehicles (Euro III–V) were instrumented with OBD-II and portable analysers recording $\mathrm{CO}$, $\mathrm{NO}$, $\mathrm{HC}$, and ${\mathrm{CO}}_2$ at 1 Hz over a four-year campaign (2021–2025; ≈2000 h). K-Means clustering on PSV_m10 identified five operating regimes (silhouette ≈0.384). Under dynamically equivalent aedc conditions, $\mathrm{NO}$, $\mathrm{CO}$, and $\mathrm{HC}$ all peaked in the 1000–2000 m band ($\mathrm{NO}$: $0.188\mathrm{g}{\mathrm{km}}^{-1}$, $6.7\times$ the sea-level value; $\mathrm{CO}$: $4.47\mathrm{g}{\mathrm{km}}^{-1}$, $+50\%$; $\mathrm{HC}$: $0.047\mathrm{g}{\mathrm{km}}^{-1}$, $+292\%$), fell in the 2000–3000 m band, and partially rebounded above 3000 m ($\mathrm{NO}$: $0.186\mathrm{g}{\mathrm{km}}^{-1}$); ${\mathrm{CO}}_2$ instead declined monotonically with altitude (182 to $119\mathrm{g}{\mathrm{km}}^{-1}$, $-35\%$), tracking a near-stable-to-slightly-declining fuel consumption (8.56 to $8.11\mathrm{L}/100\mathrm{km}$) consistent with reduced aerodynamic drag at altitude partially offsetting the density penalty. These results show that altitude affects pollutants through distinct, non-monotonic mechanisms rather than a uniform trend, so that single-coefficient altitude corrections introduce systematic bias in Andean emission inventories. Full article

Equivalent black carbon (eBC) is a key component of fine particulate matter PM_2.5, originating from incomplete combustion processes and exerting significant impacts on air quality, human health, and climate. This study investigates the temporal variability and interannual changes in eBC in Kraków, Poland, in the context of Europe’s recent energy policy changes and ongoing energy transition. A one-year dataset (October 2023 to September 2024) based on multi-wavelength optical measurements was analysed to quantify total eBC and its fossil-fuel (eBC) and biomass-burning (eBC_bb) components and compared with 2020–2021 observations. Results show strong seasonal variability, with winter eBC concentrations averaging 4.0 µg m⁻³ and peaking at 5.5 µg m⁻³ in February, while summer minima reached 1.2–1.5 µg m⁻³. Biomass-burning contributions remained low throughout the year, ranging from 0.1–0.2 µg m⁻³ in summer to 0.4–0.5 µg m⁻³ in winter. PM_2.5 concentrations followed similar trends, with winter values of 24–31 µg m⁻³ and summer levels of 8–12 µg m⁻³. Extreme pollution episodes were observed during winter, with PM_2.5 exceeding 120 µg m⁻³ and eBC reaching 13 µg m⁻³. Despite the 2019 ban on coal and wood combustion, elevated wintertime eBC indicates a strong influence of regional emissions transported from surrounding areas. A clear weekly pattern was identified, with eBC concentrations approximately 40% higher on weekdays (3.1 µg m⁻³) compared to weekends (2.2 µg m⁻³), while eBC_bb showed minimal variation. The winter-to-summer eBC ratio (2.2) highlights the combined effects of heating demand and meteorological conditions. The findings demonstrate that the energy policy changes intensified winter pollution variability and weather events rather than increasing annual averages. The observed differences indicate that pronounced wintertime variability and episodic pollution remained important during 2023–2024 despite lower annual mean concentrations than in 2020–2021. While local policies effectively limit direct emissions within Kraków, regional contributions remain significant, emphasizing the need for coordinated emission reduction strategies and the inclusion of episodic extremes in air quality and health impact assessments. Full article

To address the discrepancy between the constant-power fire sources currently used in cable fire-related research and cable fire protection product testing and actual cable fires, this paper proposes a cable equivalent combustion simulation method based on electrical fault fires. The cable tunnel experiment platform was built and, based on energy equivalence, used an igniter to simulate a fault arc’s thermal effect and ignite the cable, obtaining the temperature rise characteristics at multiple points in the fire source area. Based on the experimental data, a simulation model for the mixed combustion of multiple cable materials was established and revised, and the heat release rate (HRR) under different fire scenarios was calculated. Then, an equivalent fire source device capable of simulating the aforementioned HRR curve was designed. The results indicate that under ignition conditions with an igniter power of 400 kW and duration of 90 s, the cable fire development exhibits nonlinear dynamic evolution, with a flame height of 0.63 m. The peak temperature rise rate and peak temperature at the measurement point reach 3.27 °C/s and 926 °C, respectively. When 39.4% of the insulation layer material of the cable participates in combustion, and the fuel molecular formula is C_2.28H_5.70O_1.42N_0.08Si_0.65, the relative error between simulated and experimental temperatures during stable combustion is 3.0%. Heat release rates for mild, moderate, and severe fires stabilize near 350 kW, 420 kW, and 530 kW under this calibrated cable model. The relative error between the temperature curve from the fire source device during the stable combustion stage and that from the actual combustion experiment is 3.4%, indicating favorable equivalence. Full article

Military activities remain insufficiently represented in greenhouse gas (GHG) accounting and debates on climate security. This article develops a system-based model for assessing direct operational GHG emissions from artillery training. The model adapts established inventory logic to the structure of an artillery battery and separates emissions from mobility, stationary operation, support and logistics, and a supplementary firing-process module. It is demonstrated using a single hypothetical standardized training scenario for a battery of self-propelled howitzers, based on assumed and estimated parameters rather than field measurements. Under the stated assumptions, the training day generated an estimated 4353.74 kg carbon dioxide equivalent (CO₂e). Operational fuel combustion accounted for 93.94% of the total, and the supplementary firing-process proxy accounted for 6.06%; stationary engine operation of the howitzers in firing positions was the dominant source (73.87%). Within the defined gate-to-activity boundary, the scenario’s direct operational carbon footprint was therefore driven primarily by energy demand rather than projectile discharge. The article’s contribution is an artillery-specific, transparent decomposition of established GHG accounting principles, not a new emission-factor method. The model provides a transferable structure for tactical-level assessment, while the numerical results are scenario-specific and require validation against measured data and additional operational scenarios. Full article

The increasing interest in carbon-free fuels has positioned ammonia as a promising energy carrier for Internal Combustion Engines (ICEs), particularly in hard-to-abate sectors such as Heavy-Duty (HD) transport and maritime applications. However, its low reactivity, narrow flammability limits, and intrinsic nitrogen content pose significant challenges for stable combustion and emissions control. This work presents a predictive Quasi-Dimensional (QD) combustion model applied to simulate ammonia-fueled engines operating under both Spark Ignition (SI) and Reactivity Controlled Compression Ignition (RCCI) modes. The proposed framework couples a turbulent premixed combustion sub-model with a diffusive combustion sub-model, including a dedicated fuel-NO_x mechanism to capture nitrogen oxide formation pathways associated with fuel-bound nitrogen. The model accounts for key physical and chemical processes governing combustion, such as ignition delay, mixture stratification, and heat release dynamics, while maintaining computational efficiency suitable for parametric studies. The model is validated against experimental data from a Single-Cylinder Engine (SCE) over a wide range of operating conditions, including variations in equivalence ratio, spark timing, Ammonia Energy Fraction (AEF), and injection strategy. Results demonstrate good agreement in terms of in-cylinder pressure evolution, Apparent Heat Release Rate (AHRR), and NO_x emissions, with peak-pressure errors below 4 bar and peak-pressure locations predicted within 2 crank angle degrees. Notably, the dedicated fuel-NO_x sub-model substantially improves emission predictions, revealing that fuel-bound nitrogen is the dominant source of NO_x in ammonia combustion. Overall, the proposed QD model represents a robust and efficient tool for the analysis and optimization of ammonia-fueled engines, supporting the development of low-carbon combustion strategies for future energy systems. Full article

This paper evaluates whether hydrogen-based marine fuels were financially feasible in the European maritime sector in mid-2026 without subsidies, grants, contracts for difference, preferential carbon-price treatment, or other public subventions. A techno-economic model compares pure hydrogen fuel cells, hydrogen internal combustion, ammonia combustion and fossil marine fuels for general cargo ships, container ships and passenger liners. The model combines 2026 bunker quotations, fuel-energy properties, EU ETS exposure, FuelEU Maritime requirements, ammonia cost evidence and scenario assumptions for delivered renewable hydrogen. Results show that fossil-fuel-equivalent useful propulsion costs remain substantially lower than hydrogen and ammonia alternatives under a no-support baseline. Current EU policy narrows the gap but does not close it. The hypothesis is confirmed: in mid-2026, hydrogen-based propulsion is not commercially feasible without public support, except for exceptional pilots and premium fixed-route niches. Under the paper’s central scenarios, unsubsidised parity is unlikely before 2032–2035 for short routes and 2035–2040 for larger vessels. Green methanol is treated as a complementary hydrogen-derived pathway whose easier storage and handling may favour selected services, although its lifecycle benefit depends on renewable hydrogen and a sustainable carbon source. Full article

Maintenance management of stationary combustion engines in the agricultural sector remains largely manual, increasing the risk of unplanned downtime. This study developed a machine learning-based predictive model to anticipate failures within a 60-day horizon, enabling the transition from reactive to proactive maintenance. Following the CRISP-DM (Cross-Industry Standard Process for Data Mining) framework, a sliding-window feature engineering pipeline was built from 2250 historical records spanning 59 engines. Four ensemble learners (Random Forest, LightGBM, XGBoost, and CatBoost) were then compared under two complementary protocols: a strict 60/40 chronological split simulating deployment, and a stratified leave-engine-group-out cross-validation withholding entire engines from training. Nonparametric testing (DeLong test and engine-level cluster bootstrap) showed that the four learners are statistically equivalent, whereas the feature engineering layer contributes a large, significant discrimination gain (ΔAUC $\approx +0.06$, $p\approx {10}^{-27}$) on engines unseen during training. Random Forest, selected as the final model, achieved an AUC of 0.90 with 84.2% recall under the deployment protocol and 0.96 with 90.7% recall under engine-grouped validation. Temporal extrapolation, rather than cross-engine generalization, appeared to be the primary challenge, indicating that rigorously engineered degradation features, more than the choice of ensemble algorithm, drive predictive performance in agricultural maintenance planning. Full article

To address the insufficient prediction accuracy of traditional Arrhenius-type empirical correlations for hydrogen–oxygen combustion ignition delay time (IDT) over wide operating conditions, this paper proposes a data-driven prediction method based on Gaussian Process Regression (GPR). Based on 413 sets of shock tube and rapid compression machine experimental data, with temperature, pressure, and equivalence ratio as input features, an IDT prediction model was constructed. The GPR model adopts the Matérn 3/2 kernel function combined with the Automatic Relevance Determination (ARD) strategy for hyperparameter optimization. As a benchmark comparison, LASSO regression was employed for feature selection and parameter estimation of the Arrhenius empirical correlation. On a stratified sampling test set, the GPR model achieved a coefficient of determination R² of 0.8587 ($R_{ln}^2$ = 0.9271 on logarithmic scale), significantly outperforming the Arrhenius model’s R² of 0.5422 ($R_{ln}^2$ = 0.7027). In 50 random-split stability tests, GPR yielded a mean R² of 0.9180 with a standard deviation of only 0.0333, demonstrating excellent robustness. This study provides a valuable reference for ignition performance prediction of hydrogen–oxygen combustion systems. Full article

A full-cylinder CFD model was developed to investigate methyl decanoate (MD)/diethyl ether (DEE) blends in a MAN B&W 7S80ME-C9 two-stroke diesel engine at 75% load. The model retained the multi-injector configuration, asymmetric spray development, scavenging and exhaust processes, and in-cylinder combustion of the 800 mm-bore engine. Four equal-energy cases, MD100, MD95, MD90, and MD85, were considered, with DEE energy fractions of 0%, 5%, 10%, and 15%. DEE blending regulated spray evaporation, mixture formation, heat-release phasing, and expansion work conversion. Increasing the DEE fraction enhanced evaporation and gas-phase mixing, but stronger mixing did not necessarily improve thermal performance. The peak-pressure trend differed from the net indicated work trend, indicating that work output was governed more by pressure evolution during expansion than by peak pressure alone. MD90 maintained stronger post-injection heat release and a more favorable equivalence-ratio distribution, thereby achieving the highest net indicated work, 6.70% higher than MD100. Although MD90 showed a high mean temperature, it produced the lowest NO and NO₂ emissions because NO_X formation depended on the local coupling of temperature, oxygen availability, equivalence ratio, and residence time. The CO₂ level was lowest for MD100 among the four fuel cases. At 75% load, MD90 provided a favorable balance among heat-release phasing, net indicated work, and emission control across the four investigated fuel cases. Full article

End-of-life thermoset composite coatings removed from fuel storage infrastructure represent a difficult waste stream because they combine a cross-linked polymer matrix, glass fibre reinforcement, functional layers and possible contamination from long-term contact with petroleum products. This study presents a preliminary assessment of an epoxy-glass laminate removed from the internal surface of a large vertical diesel fuel storage tank. The work combined a simplified numerical analysis of the technical role of the coating with thermogravimetric analysis and microscopic examination of solid residues after thermal conversion. The numerical results confirmed that the coating had a real reinforcing function, reducing the maximum equivalent stress in the corroded steel shell from 228.80 MPa to 191.85 MPa. TG/DTG analysis showed that the main mass loss of the laminate occurred below 500–600 °C, while the residual mass depended strongly on the process atmosphere. The highest residue was obtained after pyrolysis (28.75%), followed by CO₂-assisted conversion (26.17%) and combustion (20.87%). Microscopic observations showed that pyrolysis favoured morphological preservation of the fibrous/mineral fraction, but the glass fibres remained partly associated with carbonised epoxy resin and graphite-containing particles. Combustion removed the organic fraction more completely, but the remaining fibres showed signs of degradation. The results indicate that pyrolysis should be treated as a promising preliminary pretreatment route when morphological preservation of the fibrous/mineral fraction is prioritised, although the retained mechanical performance and phase composition of the fibres were not assessed. The study should be regarded as a thermogravimetric and microscopic screening of a real post-service epoxy-glass coating, supporting preliminary selection of end-of-life management pathways rather than a complete recycling or environmental assessment. By linking the thermal behaviour of a real post-service composite coating with feasible end-of-life pathways, the study contributes to sustainable waste management by supporting more informed decisions on material preservation, energy recovery, industrial co-processing and avoidance of landfilling for difficult thermoset composite wastes. Full article

This study numerically investigates the combustion characteristics of four catalytic micro-burners with different channel geometries: a straight-channel burner (Burner 1), a symmetric U-bend burner (Burner 2), and two asymmetric U-bend burners with either a wider inlet channel (Burner 3) or a wider recirculating channel (Burner 4). A steady-state, two-dimensional mathematical model accounting for gas-phase and catalytic reactions of propane on Pt/Al₂O₃ is employed. The results show that U-bend configurations significantly reduce the ignition equivalence ratio compared to the straight-channel design, with Burner 4 exhibiting the lowest value of 0.45. At an equivalence ratio of 0.85, Burner 4 achieves the highest maximum temperature and the most upstream flame location, attributed to enhanced heat recirculation and prolonged residence time in the wider recirculating channel. Temperature and propane mass fraction distributions reveal strong thermal coupling between the inlet and recirculating channels in asymmetric designs. The contribution of catalytic reactions to total heat release remains within a narrow range across the examined equivalence ratios for all U-bend burners, whereas Burner 1 shows a much higher catalytic contribution (~87%) due to suppressed gas-phase reactions. The U-bend geometries also exhibit lower heat loss ratios than the straight channel. The maximum wall temperature gradient increases with equivalence ratio, and the ranking among the three U-bend burners varies with operating conditions, indicating that geometry-specific thermal stress should be considered in practical design. Full article