Search Results (2,735)

Lignite-derived activated carbon (L-AC) was fabricated via a microwave-assisted KOH activation process using a low-rank Mae Moh lignite and explored its potential as an adsorbent solid for post-combustion CO₂ capture. Optimization of the KOH ratio, microwave irradiation power, and activation time gave rise to a product with a BET surface area of 1349 m² g⁻¹ and total pore volume of 0.78 cm³ g⁻¹, which represented 165 times and 78 times enhancement compared with that of the initial lignite, respectively. Scanning electron microscope (SEM) images proved the formation of a hierarchical macropore–mesopore–micropore structure, whereas Raman (Iᴰ/Iᴳ = 1.83) and Fourier-transform infrared spectroscopy analyses revealed a graphitic-like structure rich in defects with the existence of C=O and C–O–C functional groups involved in the Lewis acid–base interaction between L-AC and CO₂ molecules. Dynamic fixed-bed breakthrough tests performed at temperatures of 298, 328, and 353 K under post-combustion relevant conditions (CO₂ concentration: 15%, pressure: 1 atm) yielded CO₂ equilibrium uptake capacities of 47.34, 34.37, and 21.34 mg g⁻¹, respectively, with outstanding cyclic stability achieved after six consecutive adsorption–desorption cycles of temperature swing adsorption–desorption at 393 K. Among the seven nonlinear kinetic models, the Avrami, FL-PFO, and general-order models exhibited the highest fitting accuracy (R² = 0.9994–0.9998), suggesting that CO₂ adsorption onto L-AC proceeds through heterogeneous, multi-stage adsorption kinetics. A Weber–Morris intra-particle diffusion analysis identified a three-stage sequential transport mechanism in which mesopore diffusion constitutes the primary rate-limiting step. Thermodynamic parameters confirmed spontaneous (ΔG° = −24.20 to −26.87 kJ mol⁻¹), exothermic (ΔH° = −9.42 kJ mol⁻¹), and entropy-assisted adsorption (ΔS° = +49.93 J mol⁻¹ K⁻¹) consistent with a physisorption mechanism, corroborated by a low activation energy of 9.11 kJ mol⁻¹. These findings demonstrate the viability of low-rank lignite as a low-cost precursor for the scalable synthesis of high-performance carbonaceous CO₂ adsorbents for post-combustion capture applications. Full article

The increasing generation of wood ash (WA) from biomass combustion presents both an environmental challenge and an opportunity for sustainable resource utilization. This review provides a comprehensive assessment of recent advances in the valorization of WA for the development of sustainable engineering materials within a circular economy framework. Unlike previous studies that primarily focus on isolated applications of WA, this work integrates multiple technical dimensions, including material characterization, advanced manufacturing technologies, mechanical performance evaluation, computational modelling, and industrial commercialization pathways. Wood ash typically exhibits alkaline characteristics (pH 9–13.5) and particle sizes ranging from 1 to 1000 µm, enabling its application in a wide range of material systems. In cementitious materials, partial replacement of cement with WA (0.10–20%) generally improves mechanical performance, whereas excessive incorporation may reduce structural integrity. The high silica content (>62%) in certain WA types also enables its utilization in lightweight glass systems and radiation-shielding materials. Furthermore, WA has emerged as a promising functional filler in polymeric and ceramic composites, where additions above 0.5% can enhance dynamic mechanical properties and thermal stability. The review also examines standardized inspection and testing procedures, including quality control (QC) and quality assurance (QA) frameworks based on American Society for Testing and Materials (ASTM), Canadian Standards Association (CSA), and European standards, to ensure the reliability of WA-derived materials. Recent developments in artificial intelligence, machine learning, and computational modelling are highlighted for predicting mechanical behavior, optimizing processing parameters, and enabling digitalized manufacturing systems. In addition, circular manufacturing strategies and economic evaluation models, including break-even analysis, are discussed to assess the industrial feasibility of WA-based products. By integrating circular economy principles with materials engineering, digital technologies, and economic assessment, this review establishes a holistic framework for transforming wood ash from an industrial residue into value-added sustainable materials for construction, energy, and advanced composite applications. Full article

To address the major safety hazard that heat released from mining polyurethane (PU) reinforcement materials may induce spontaneous combustion of residual coal in goaf, this study selected No. 3 coal from Wangzhuang Coal Mine, Shanxi Lu’an, as the research object. A self-developed large-capacity, large-scale experimental system was used to conduct programmed heating experiments on 2.0 kg multi-particle-size coal-PU mixed samples. The effects of PU content on characteristic gas release, crossing point temperature (CPT), residue morphology, and TGA-DSC characteristic temperatures were systematically investigated, and the reaction-kinetic evolution was further analyzed using the distributed activation energy model (DAEM). The results show that coal and PU exhibit a significant synergistic enhancement effect during co-heating. As the PU content increased, the release concentrations of CO, C₂H₄, and C₂H₆ increased markedly, and their initial release temperatures decreased, whereas CH₄ generation was inhibited by hydrogen-radical competition; no C₂H₂ was produced below 400 °C. The CPT decreased linearly with an increasing PU content, with an average decrease of approximately 8.5 °C for every 10% increase in PU content. Residue morphology showed clear critical features: glassy agglomerates appeared when the PU content exceeded 16.67%, and dense bulk coking occurred when the PU/coal mass ratio was greater than 1:10. TGA-DSC analysis showed that when the PU/coal ratio was lower than 1:10, the ignition temperature of the mixed sample was higher than that of pure coal, indicating an inhibitory synergistic effect. When the ratio exceeded 1:10, the ignition temperature decreased significantly, and the synergy shifted to promotion; increasing the heating rate shifted the characteristic temperatures to higher values and increased the reaction intensity. DAEM analysis further confirmed that when the PU ratio exceeded 1:10, the apparent activation energy of the mixed samples was lower than that of pure coal. Coal powder also acted as a physical skeleton that effectively dispersed molten PU, eliminated the activation-energy peaks of pure PU in the conversion ranges of 30–50% and 70–90%, and substantially improved combustion stability. Mechanistically, low-temperature PU melting and coating optimized heat and mass transfer, medium-temperature pyrolysis released active radicals and combustible gases that altered coal pyrolysis pathways and the radical reaction environment, and high-temperature hydrogen-radical competition reshaped the gas-product distribution. Together, these processes form a complete chain of synergistic spontaneous combustion. This study identifies key safety threshold parameters for PU reinforcement materials, recommends a PU content of ≤9.10%, and identifies CO and C₂H₄ as priority early-warning gases, providing direct experimental evidence for characteristic-gas-based early warning and mine fire prevention. Full article

This study presented a comprehensive optimization of a piezoelectric injector specifically designed for pure methanol compression-ignition engines. As a fuel for compression-ignition engines, methanol exhibits broad application prospects. To overcome the challenges posed by methanol’s low cetane number and energy density, a co-optimization strategy was implemented, targeting the actuator, drive waveform, and internal flow geometry. The redesigned injector exhibited superior dynamic performance, featuring significantly faster response times and enhanced operational stability, which were critical for precise fuel delivery control. Furthermore, the optimized internal flow path increased the effective flow rate, ensuring sufficient fuel supply across all engine operating conditions. The upgraded injector was rigorously tested on an engine bench, demonstrating substantial performance gains. Brake thermal efficiency improved from 38.9% to 40.4% at low load and from 43.68% to 46.07% at high load. Emissions of CO, formaldehyde, acetaldehyde, and unburned methanol were consistently reduced, with the maximum reduction reaching 23.1%, confirming markedly enhanced combustion completeness. This improvement was directly attributed to the injector’s refined spray characteristics and precise control, although it led to a slight increase in NOx emissions due to higher peak combustion temperatures. Full article

Construction site fires caused by spatiotemporal overlaps between hot work (ignition sources) and combustible substances remain a critical concern. The traditional method identifies fire hazards based on the intersections among hot works and other works with combustible substances. However, the intersections between hot work and built elements containing combustible materials are ignored, which can also lead to fire accidents. In addition, the detection of such intersections relies on the computationally intensive proximity search from the ignition source to the potential combustible substances, resulting in a long-time calculation in large construction projects with the dynamic construction process. To address this limitation, this study proposes a voxel-based fire hazard identification method applicable to large 4D-BIM models, fast and accurately. By discretizing BIM into reusable LEGO voxels, both the construction activities and the building components can be mapped to the voxels, enabling a simultaneous intersection identification between ignition sources and both activities and BIM elements. In addition, voxel-based proximity searching is efficient, enabling a fast and accurate fire hazard identification. Validation tests demonstrate high accuracy with calculatable spatial error (maximum 0.57 m for 200 mm voxels) and superior efficiency (126–1368% faster than mesh-based methods). By reusing the voxelized BIM data, the speed can be enhanced by between 400% and 1975%. This method offers an efficient and reliable digital solution for proactive construction fire safety management in 4D-contexts. Full article

The global energy demand continues to rise, and increasing harmful emissions from fossil fuel combustion highlight the urgent need for alternative, eco-friendly energy sources. Hydropower stands out as a promising solution, leveraging the fact that 71 % of the Earth’s surface is covered by water, allowing for energy harnessing with minimal environmental impact. Modern hydropower technologies must also be optimized to operate efficiently in low-velocity water, a common condition that typically produces low power output. Savonius turbines have been widely studied, with many efforts focusing on enhancing their performance through design modifications. However, much of this research is limited to numerical simulations only. This study seeks to address this gap by experimentally validating a new optimization process that integrates a deflector into the turbine design, first based on Computational Fluid Dynamics. Both the turbine and deflector were fabricated and tested in our water flume, with a comparative analysis conducted against the standard Savonius turbine. In addition to evaluating key experimental parameters such as torque and rotational speed at various tip speed ratios, Particle Image Velocimetry (PIV) is used to investigate the flow structure around the turbine, proving the validity of our CFD-based optimization under real-world conditions. Full article

Wood- and lignocellulosic-residue-derived constituents have attracted increasing attention in cementitious materials because they may support clinker reduction, waste valorization, moisture regulation, crack control, and longer service life. This review synthesizes evidence on wood ash, wood-derived biochar, and wood or lignocellulosic fibers in low-clinker and low-carbon-oriented cementitious systems, with emphasis on severe cold service involving freeze–thaw cycling, salt freezing, and chloride ingress. This review clarifies the evidence boundaries among direct wood-derived materials and related biomass or lignocellulosic analogues, because wood ash, non-wood biomass ashes, such as bamboo ash and bagasse ash, wood fiber, and non-wood plant fibers cannot be treated as equivalent materials. Wood ash is best regarded as a controlled partial binder replacement or filler whose performance depends on combustion temperature, oxide composition, alkali content, residual carbon, fineness, and water demand. Biochar is more appropriately treated as a low-dosage functional additive, commonly in the range of approximately 1–3 wt.% of binder, where it may assist internal curing, nucleation, moisture redistribution, and pore regulation; excessive dosage can increase porosity and reduce mechanical or transport performance. Wood and lignocellulosic fibers mainly contribute to crack control, toughness, and post-cracking behavior, but their effectiveness is limited by water absorption, swelling, lignin- and extractive-related hydration interference, and long-term interfacial degradation in alkaline matrices. Across these material classes, engineering performance is governed by the interfacial transition zone, pore-size distribution, moisture state, air–void compatibility, and exposure-specific durability response. The main contribution of this review is to propose a boundary-conscious framework for material classification, quantitative comparison, mixture-design screening, and severe-cold durability qualification. Future application requires source-specific characterization, water-demand control, treated fibers, low-dosage biochar optimization, and service-informed testing that couples freeze–thaw cycling, chloride transport, saturation state, and microstructural verification. Full article

The valorization of vegetable-oil biomass into bio-based functional fluids offers a sustainable route for replacing petroleum-derived insulating liquids in power equipment. In this study, soybean and canola oils were used as renewable lipid feedstocks and converted into biomass-derived ester fluids through acid-catalyzed transesterification with methanol, ethanol, 1-propanol, and 1-butanol. The obtained ester-rich products were subjected to a combined physicochemical, dielectric, and thermal screening workflow, including kinematic viscosity at 40 °C (ν₄₀), acid value, breakdown voltage (BDV), differential scanning calorimetry (DSC; 2–8 °C min⁻¹ under N₂), and oxygen bomb calorimetry. Transesterification effectively upgraded the vegetable oils into low-viscosity ester-rich product fluids for most alcohol routes, with soybean methyl ester (SME) reaching 4.41 ± 0.02 mm² s⁻¹ and selected canola-derived esters showing viscosities of 5.81–6.81 mm² s⁻¹. However, the functional performance of the biomass-derived fluids was strongly governed by the alcohol route. SME exhibited the most favorable balance between dielectric and physicochemical properties, delivering the highest BDV of 64.90 ± 9.74 kV, exceeding the IEC 60156 threshold of 30 kV, while maintaining a low acid value of 0.0103 ± 0.0006 mg KOH g⁻¹. In contrast, propyl- and butyl-derived esters showed substantially lower BDV values of ≤14.98 kV, whereas ethanol-derived products retained near-neat-oil viscosities and were unsuitable for BDV testing under the applied conditions. Although propyl- and butyl-derived ester-rich products reduced kinematic viscosity, their markedly lower BDV values were likely associated with route-dependent product heterogeneity, lower alcohol–oil miscibility, possible residual polar impurities, and moisture sensitivity; therefore, they were regarded as non-optimized screening outcomes rather than IEC-compliant transformer-fluid candidates. DSC analysis provided comparative thermal-response descriptors under nitrogen, with methylation producing more coherent endothermic features. The combustion heats of the ester-rich products were concentrated at approximately 39–41 MJ kg⁻¹, lower than that of the mineral-oil reference in this dataset, suggesting combustion heat was used only as a preliminary energy-density descriptor and was not interpreted as direct evidence of improved fire safety. From an engineering-safety perspective, the lower combustion heat of the bio-esters may reduce the potential fire-load contribution during fault-related fire scenarios, although full fire-safety qualification requires additional flash-point, fire-point, and aging evaluations. Overall, this work demonstrates that alcohol route selection is a critical factor in converting vegetable oil biomass into high-value bio-based insulating fluids. Among the tested formulations, soybean methyl ester is the most promising baseline candidate for further development as a biodegradable, sustainable transformer fluid. Full article

This study employed a Gaussian Process Regression model combined with the Combinative Distance-Based Assessment method to analyze and optimize the performance and emission characteristics of a diesel engine operating with different fuel blends under various load conditions. The results indicated that increasing engine load generally improved brake thermal efficiency while reducing fuel consumption. Compared with conventional diesel fuel, palm biodiesel blends exhibited relatively higher fuel consumption and increased exhaust emissions under certain operating conditions. The incorporation of nanoparticle additives enhanced the combustion process, resulting in improved engine performance and reduced emissions. Among the tested fuels, the blend containing magnesium oxide nanoparticles exhibited the best overall performance across the investigated load range and showed greater potential for reducing incomplete-combustion emissions. The developed machine learning model accurately predicted engine performance and emission parameters and demonstrated strong generalization capability. Furthermore, the multi-criteria decision-making analysis enabled the identification of promising fuel–operating condition combinations based on multiple performance and emission indicators. Experimental validation demonstrated good agreement between the predicted and measured results, confirming the reliability of the proposed approach. The findings suggest that integrating machine learning techniques with multi-criteria decision-making methods provides an effective framework for fuel formulation optimization, engine performance enhancement, and emission reduction. Full article

This study investigated the effects of environmental conditions on polycyclic aromatic hydrocarbon (PAH) emissions from scented candles during combustion. An exposure chamber was established and validated to ensure stability and uniformity before the experiments were conducted. One of the most widely used scented candles (paraffin wax + 6% lavender essential oil) was selected in the present study. Testing environmental conditions included three relative humidity (RH) levels (60%, 75%, and 90%) and three air exchange rates (ACHs) (0.5, 1.0, and 2.0 h⁻¹). For each tested environmental condition, three replicate measurements were conducted. Gas-phase and particle-bound polycyclic aromatic hydrocarbons (PAHs) were collected using filter cassettes and XAD-2 sorbent tubes, respectively. Results showed that, under identical RH conditions, both C_total-PAHs and EF_total-PAHs followed the trend of 0.5 ACH > 2.0 ACH > 1.0 ACH, whereas total-Bap_eq and EF_Total-BaPeq values decreased with increasing ACH. While under identical ACH conditions, emissions showed a nonlinear response to RH, following the trend: 75% > 90% > 60%. Most detected PAHs were present in the gaseous phase and were dominated by low-molecular-weight compounds containing two to three aromatic rings. The estimated highest incremental lifetime lung cancer risk reached 1.20 × 10⁻⁶ for aromatherapy workers, assuming an exposure duration of 8 h day⁻¹ over 40 years. These findings highlight the potential health risks associated with the use of scented candles and emphasize the importance of adequate ventilation to reduce long-term indoor exposure. Full article

Currently, high-speed gasoline engines are increasingly focusing on miniaturization and efficiency. Compared with turbocharging, mechanical supercharging is undoubtedly the more suitable technical approach for small, high-speed gasoline engines. To clarify the influence of the proposed supercharging approach on power, thermal efficiency and emissions within a broad range of engine speeds, this study designed two supercharging schemes (with different supercharger/crankshaft transmission ratios), and conducted bench tests comparing with the original engine. The results showed that the boost effect was more pronounced under medium load conditions. At full load, the high-speed supercharging scheme (94.5/86 ratio) on average improved torque by 10.8%, while the low-speed boost mode (86/61 ratio) only took effect after 5500 rpm. But at 60% load, 94.5/86 and 86/61, respectively, improved torque by 24.4% and 11.7%; thermal efficiencies of both supercharging schemes were almost the same and higher than that of the original operation by 0.8%; thus, the specific fuel consumption was reduced, on average, by ~9.5%. After boosting, the ignition phase was delayed due to the knock limit, but the high cylinder temperature promoted the recovery of the combustion rate in the later stage. In terms of emissions, NO_x increased by 28% with the 94.5/86 scheme, while it decreased very slightly with the 86/61 scheme. CO rose by 3.7% under the 94.5/86 scheme, while it almost did not change under the 86/61 scheme operation, and HC increased by 13% and decreased by 21%, respectively, under the high and low boosting schemes. In conclusion, our proposed supercharging approach improved power and thermal efficiency and afforded a compromise emission effect. This study has revealed the performance trade-off rules of different boosting modes, which can provide important theoretical and technical support for the mechanical supercharging modification of high-speed gasoline engines. Full article

This study explored a spatio-temporal deep learning approach for optical soft sensing of combustion emissions in a coal–biomass co-firing scenario. High-speed RGB flame sequences from a 0.5 MW test rig co-firing hard coal with 10% straw were synchronized with extractive measurements of O₂, CO₂, and NO. These sequences were used to train three shallow 3D CNNs and three 3D ResNet-50 architectures with squeeze-and-excitation attention. The proposed 3D CNN/ResNet models performed simultaneous regression of all three gas species from flame image volumes. The best configuration achieves R² values of 0.975, 0.987, and 0.980, accompanied by mean absolute errors of 0.23% by volume, 13.15 mg/m³, and 0.19% by volume for O₂, NO, and CO₂, respectively, at a resolution of 128 × 96 × 96 pixels. Within the scope of the available dataset, comprising a single measurement run and a single fuel mixture, the results indicate that a comprehensive spatio-temporal analysis of flame images can yield accurate estimates of multiple gas concentrations, thereby providing a promising foundation for the future development of soft optical sensors. At the same time, the study is limited to a single combustion experiment, a single biomass fraction, and a single borescope orientation, and the inference delay and hardware requirements were not quantified; therefore, issues regarding the generalizability of the proposed approach to different conditions and its implementation remain open for further work. Full article

Robust flame stabilization in low-Mach, low-enthalpy supersonic combustors is a core bottleneck for turbine-based combined cycle (TBCC) mode transition. Existing studies mainly focus on single-injector configurations, while the injection angle modulation mechanism for multi-injector cavity flameholders remains unclear under TBCC-relevant conditions. This work experimentally investigated the effects of 30°, 45°, and 90° injection angles on cold-flow mixing, reacting flow topology, and flame stabilization in a Mach 1.6, 660 K dual-injector cavity combustor. Results showed that the overall cold-flow jet penetration capacity in the fully developed far field increased with injection angle following the order of 90° > 45° > 30°. Combustion heat release universally enhanced jet penetration, with a maximum 25% augmentation observed at 30° injection, which attenuated with steepening injection angle. Moreover, flame stability exhibited a non-monotonic trend in the tested dual-injector configuration. Full article

Battery electric vehicle (BEV) adoption does not always result in long-term ownership, because some owners may return to internal combustion engine vehicles after purchase. This study examines how internal customer factors influence the formation of product attachment, an emotional bond between owners and their BEVs. This issue is important because such attachment may support long-term commitment, expressed through advocacy and loyalty after adoption. The study focuses on instrumental, affective, and symbolic car use motivation, customer innovativeness, and direct experience. Data were collected through face-to-face surveys with 392 Indonesian BEV owners who had driven their vehicles for more than 5000 km. ANOVA and PLS-SEM were used to examine segment differences and test the structural model. Affective motivation had the largest positive path coefficient for product attachment (β = 0.451), followed by symbolic motivation (β = 0.370), direct experience (β = 0.301), and instrumental motivation (β = 0.229). Customer innovativeness was not significant (β = −0.026, p = 0.324). Product attachment showed strong relationships with customer advocacy (β = 0.649) and loyalty (β = 0.686). This study extends the product attachment literature by explaining how internal customer factors are related to the development of product attachment and the extent to which owners become attached to their BEVs. Full article

Graphite nozzles remain the dominant choice for small hybrid and solid rocket motors operating on laboratory and university budgets, owing to their low cost, ease of machining, and rapid turnaround during iterative design campaigns. These same programs, however, must contend with the fact that graphite erodes through coupled thermochemical and mechanical mechanisms when exposed to the oxidizing species generated by high-energy propellant combustion, and the resulting throat-area growth fundamentally alters the time histories of chamber pressure, thrust, and delivered specific impulse. This paper presents a nozzle-erosion reconstruction model that extracts the time-resolved throat area from coupled thrust and chamber-pressure measurements using the thrust coefficient relationship, scales the reconstructed area history against pre- and post-test throat measurements, identifies the onset and rate of erosion, and accounts for variable sensor lag between the thrust-stand and pressure-transducer signal chains. The model is exercised on two complementary sets of laboratory-scale GOX/ABS hybrid hot-fire data that together span roughly two orders of magnitude in total throat-area change and peak chamber pressures from 0.5 to 3.4 MPa: a controlled three-operating-point campaign conducted in support of the NASA Plume-Surface Interaction (PSI) program, and a set of higher-pressure firings from the laboratory development series in which the technique was matured. Reconstructed erosion-onset times, erosion rates, and total throat-diameter change are reported for each firing, the reconstruction accuracy is characterized as a function of erosion magnitude. A correlation of graphite erosion with chamber pressure is examined across the combined envelope. The results demonstrate the robustness of the reconstruction technique and provide a reusable framework for post-test reconstruction of transient nozzle geometry in rocket-engine ground testing. Full article