Search Results (277)

Reactivity-controlled compression ignition (RCCI) enhances engine performance while mitigating the diesel soot–NO_x tradeoff. In this work, natural gas (NG) RCCI combustion was investigated on a heavy-duty single-cylinder research engine with three different pilot fuels: diesel, an 80/20 (% v/v) blend of n-butanol and diesel (80B20D), and dipropyl oxymethylene ether (P1P). The experiments were performed at a constant speed of 1339 rev/min, a fixed load (IMEP_g = 5 bar), and 1.5 bar boost pressure. Initially, NG RCCI combustion was studied under identical operating conditions, and subsequently with constant combustion phasing (CA50) for all pilot fuel–NG combinations for a levelized comparison. The results revealed that CA50 profoundly impacted the efficiency and unburned hydrocarbon (HC) emissions for all pilot fuels. Maintaining an optimal CA50 of 363 ± 1 CAD, high fuel conversion efficiencies (~40%) and HC emission reductions (~38–49%) were achieved across pilot fuels. The pilot fuel reactivity significantly affected combustion and emissions. The apparent heat release histories transformed from a two-stage to a single-stage Gaussian profile at a much-retarded start of injection (SOI~30 bTDC) for 80B20D-NG compared to diesel–NG and P1P-NG (40 bTDC), leading to significantly lower NO_x emissions. More advanced SOIs and lower NO_x emissions were possible with diesel–NG and P1P-NG compared to 80B20D-NG. Full article

The production of hot mix asphalt (HMA) is energy-intensive, resulting in carbon dioxide (CO₂) and greenhouse gas (GHG) emissions. The primary energy source (accounting for over 97%) and emissions source is the rotary drum employed for the drying and heating of the aggregates. Quantifying the CO₂ emissions associated with combustion is of crucial importance in order to facilitate a more profound comprehension of the environmental impacts of HMA production. The objectives of this study are to develop a methodological framework for the quantification of combustion-related carbon dioxide emissions in the context of asphalt production. The proposed framework investigates three complementary approaches: (i) an energy-balance-based thermal energy (TE) model, (ii) recordings of fuel consumption and (iii) direct measurement of exhaust-gas composition. By applying these methods in parallel and cross-comparing their results batch by batch, the framework enables reliable verification of actual CO₂ emissions from the module A3—production stage of asphalt manufacturing. In this stage, the predominant source of greenhouse gases is fuel combustion during aggregate drying and heating. A comprehensive set of data was collected from two HMA batch plants, each operating under distinct conditions. The parameters considered included fuel type, asphalt mixture type, asphalt production time, aggregate moisture content, mixing temperature, and production rate. The TE model demonstrated a robust linear correlation with measured energy consumption (R² = 0.97), and fuel-based CO₂ estimates exhibited minimal discrepancy compared to direct exhaust-gas measurements on average (mean difference 1.0%; t-test p = 0.674). However, systematic discrepancies were observed between the two plants (with overestimation of up to 20% at one plant (AP1) and underestimation of up to 12% at the other (AP2)). This demonstrates that energy-based CO₂ estimation methods require plant-specific calibration against direct measurement before they can be reliably applied in life cycle assessment (LCA) and environmental product declaration (EPD) practice. Measured CO₂ emission intensities ranged from 17.39 to 21.76 kg/t at AP1 and from 16.05 to 18.44 kg/t at AP2; the casing-losses factor of the TE model was calibrated to CL = 23% for the studied diesel-fired plants (mean deviation +0.4% from measured energy); and aggregate moisture content explained 74% of the variance in measured energy consumption (R² = 0.743). Full article

Ribbed Smoked Sheet (RSS) rubber production in southern Thailand relies extensively on rubber-wood combustion, potentially generating substantial emissions of fine particulate matter and polycyclic aromatic hydrocarbons (PAHs). Despite the economic importance of this sector, systematic characterization of biomass-derived PAHs under tropical monsoonal and coastal conditions remains limited. This study investigates the particle size distribution, concentration levels, seasonal variability, and atmospheric dynamics of PAHs associated with RSS production in Chumphon Province, Thailand. Size-segregated particulate matter was collected using an eight-stage Andersen cascade impactor at two contrasting sites during a seven-month monitoring period from March to September 2025, covering the transition from the late dry/summer season to the rainy season in southern Thailand. Fifteen priority PAHs were quantified by high-performance liquid chromatography with fluorescence detection. Results indicate that emissions from rubber-wood combustion inside smokehouses exhibit a unimodal distribution dominated by submicron particles (MMAD = 0.85 µm; GSD = 2.71). Ambient aerosols displayed a bimodal structure, with an accumulation-mode peak (~0.6 µm) associated with combustion processes and a coarse-mode peak (~4 µm) linked to mechanical and marine aerosol sources. Particle-bound PAHs were predominantly associated with fine particles (~0.59 µm), although seasonal hygroscopic growth under high humidity shifted modal diameters toward ~1.8 µm during the rainy season. PAH profiles were dominated by 3–4 ring compounds characteristic of biomass combustion. Total PAH concentrations exhibited a strong positive correlation with monthly RSS production, while precipitation demonstrated an exponential scavenging effect. Monsoonal circulation and sea spray aerosol (SSA) interactions were identified as key regulators of gas–particle partitioning, transport pathways, and removal efficiency. The findings reveal that the coastal atmosphere of southern Thailand functions as a dynamic multiphase system in which emission intensity, hygroscopic particle growth, monsoonal transport, and wet deposition collectively govern PAH behavior. This study provides the first integrated assessment linking rubber-sheet production dynamics to size-resolved PAH distributions under tropical coastal conditions and offers a scientific foundation for emission mitigation strategies in biomass-dependent agro-industrial regions. Full article

This work focuses on the combustion characteristics and kinetics of three building timber organic solid wastes (BTOSW)—China fir, Eucalyptus wood, and Pine wood—aiming to provide theoretical and data support for the thermal conversion and energy utilization of construction-derived woody biomass. Thermogravimetric analysis (TGA) reveals that all three materials exhibit two-stage combustion behavior: volatile combustion at low temperatures (<320 °C) and char combustion at high temperatures (320–500 °C). Increasing the heating rate shifts the decomposition peaks to higher temperature zones, reflecting the combined effects of thermal lag and shortened reaction time. Kinetic analysis shows that the correlation coefficients (R²) calculated by different models are all greater than 0.97, with the first-order chemical reaction model (O1) demonstrating the highest goodness-of-fit for Pine wood (R² = 1.000) and Eucalyptus wood (R² = 0.995), indicating that homogeneous chemical reactions dominate the combustion process. The initial combustion temperatures of China fir, Eucalyptus wood, and Pine wood are 256 °C, 262 °C, and 270.9 °C, respectively, with flammability indices of 1.08, 1.46, and 1.15 and comprehensive combustion characteristic indices of 2.71 × 10⁻², 1.26 × 10⁻², and 1.75 × 10⁻² °C⁻²min⁻¹, respectively. This work provides important theoretical support for both the energy utilization of timber-framed buildings waste and the fire protection design and flame retardancy of timber-framed buildings, contributing to the development of scientific fire prevention measures and the preservation of this architectural heritage. Full article

This study investigated the effect of replacing N₂ with CO₂ on the pyrolysis behavior, char structure evolution, and kinetics of Fushun (FS) and Changji (CJ) oil shales. Non-isothermal thermogravimetric experiments were conducted at 5, 10, 20, and 40 °C·min⁻¹ under N₂ and CO₂ atmospheres, and the resulting chars were characterized by FTIR, XPS, BET, and SEM. Kinetic parameters were evaluated using Friedman, FWO, KAS, Starink, and Vyazovkin iso-conversional methods. Both oil shales underwent three stages: moisture release, main organic-matter pyrolysis, and high-temperature mineral decomposition. Increasing the heating rate shifted T_s and T_max to higher temperatures and intensified volatile release. At 40 °C·min⁻¹, replacing N₂ with CO₂ increased T_s from 322.6 to 399.3 °C for FS and from 368.1 to 377.3 °C for CJ, while reducing the maximum mass-loss rates to 6.81 and 8.66%·min⁻¹, respectively. N₂ favored pore development, increasing the specific surface areas of FS and CJ chars to 14.1402 and 6.1464 m²·g⁻¹, whereas CO₂ caused pore blockage in FS char and reduced its surface area to 2.7783 m²·g⁻¹. XPS showed that CO₂ promoted the formation or preservation of oxygen-containing surface carbon, especially C=O and O–C=O groups. The E_α values first decreased and then increased with conversion and were generally lower in CO₂ than in N₂. The average activation-energy differences between the two atmospheres were 23.5 and 43.2 kJ·mol⁻¹ for FS and CJ, respectively. These results provide experimental and kinetic data for modeling primary oil shale pyrolysis and subsequent char combustion and gasification under CO₂-rich conditions. Full article

Agricultural biomass, comprising animal manure, food processing residues, lignocellulosic agricultural by-products, and other agro-industrial wastes, is generated in large quantities worldwide, particularly in developing countries. Although these residues pose significant environmental disposal challenges, they represent abundant renewable carbon resources that can be valorized into biofuels, contributing to sustainable waste management and circular bioeconomy initiatives. Biohythane, a gaseous fuel consisting of hydrogen and methane, is primarily produced through two-stage anaerobic digestion, in which dark fermentation generates hydrogen-rich intermediates that are subsequently converted into methane during methanogenesis. The separation of these stages enables independent optimization of hydrogen and methane production, resulting in improved substrate conversion efficiency and higher energy recovery than conventional single-stage anaerobic digestion. In addition, the presence of hydrogen enhances combustion characteristics while reducing greenhouse gas and nitrogen oxide emissions. This review critically evaluates recent advances in biohythane production from agricultural biomass through a structured assessment of peer-reviewed literature retrieved from major scientific databases. The selected studies were synthesized to examine biomass feedstocks, pretreatment technologies, microbial communities, metabolic pathways, reactor configurations, and process optimization strategies influencing biohythane production. The review further discusses the advantages and limitations of different agricultural residues, identifies current technological and economic challenges, and highlights emerging research opportunities to improve process efficiency and facilitate the sustainable commercialization of biohythane as a low-carbon renewable energy source. Full article

A Realizable k−ε turbulence model and a finite-rate/eddy-dissipation combustion model, together with experimental validation, were used to investigate the flow and combustion characteristics of a novel triple-swirler combustor under multiple operating conditions. The results show that, compared with the conventional baseline configuration, the ring-cooled radial structure induces a third-stage swirl through inclined cooling holes. This swirl regulates the recirculation structure formed by the first two axial swirlers, transforms the core reaction zone from a single large-scale recirculation vortex into multiple vortical structures, forms a low-temperature cooling coverage outside the main reaction zone, and weakens the near-wall entrainment and high-speed sweeping induced by the kidney-shaped vortex pair downstream of the primary holes. The peak temperature of the outer liner is reduced by 14.72%, and the wall-temperature uniformity is improved by 36.02%. The outlet temperature distribution factor (OTDF) decreases by 14.81% and 15.79% under high and medium operating conditions, respectively, indicating an improved outlet temperature field. This study provides engineering guidance for the design of high-performance combustors. Full article

In-wheel motor (IWM) systems enable compact architectures and advanced control strategies, making them increasingly relevant in hybrid and electric vehicle applications. This work presents the design and the integration of a front-axle IWM system for a Formula SAE combustion vehicle, within a parallel hybrid configuration. The study includes vehicle dynamics analysis, battery pack sizing under strict regulatory constraints, and an initial evaluation of motor and transmission requirements. A MATLAB R2023a-based algorithm was developed to design and optimize a compact two-stage planetary gearbox. This structured and scalable approach supports future development phases and offers a valuable methodology for early-stage hybrid powertrain design. 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

To address the high experimental costs and data scarcity inherent in Directed Energy Deposition (DED), this study proposes a data-efficient hybrid optimization framework for the precision manufacturing of Inconel 718 aerospace components. The framework leverages a two-stage strategy to bridge traditional experimental design with advanced machine learning, ensuring robust process optimization even with limited datasets. In the first stage, the Taguchi method (L16 orthogonal array) was employed for coarse-grained screening to identify influential control factors. In the second stage, a Fully Connected Neural Network (FNN) coupled with Bayesian Optimization (BO) was deployed. Crucially, this machine learning component functions as an optimization-oriented trend surrogate rather than a global regressor, successfully guiding the optimization under extreme data scarcity. The optimized process window yielded exceptional structural integrity, achieving a porosity as low as 0.03%. To thoroughly validate its practical efficacy, tensile testing (ASTM E8/E8M) and Rockwell hardness measurements (ASTM E18) were systematically conducted on the optimized specimens. The mechanical characterization demonstrated an average tensile strength of approximately 1358 MPa and a hardness of ~40 HRC. Finally, the framework was successfully validated through the robotic DED fabrication of a complex-geometry aerospace engine combustion chamber casing, bridging laboratory-scale optimization with authentic industrial applications. Full article

Cross-laminated timber (CLT) is increasingly used in multi-story timber construction, but its combustible nature requires reliable fire protection, particularly in layered wall assemblies with concealed cavities. This study compares two medium-scale cross-laminated timber (CLT) sandwich wall assemblies exposed to radiant heat flux of 20 kW/m² for 90 min: an uncoated reference assembly and an assembly with PROMADUR^® intumescent coating applied to the CLT surfaces. Both specimens consisted of a 90 mm three-ply CLT panel encapsulated with 12.5 mm gypsum-fiber boards fixed to a wooden stud frame forming a 40 mm installation cavity. Fire-test observations were supplemented by simultaneous thermal analysis (STA), i.e., thermogravimetry (TG)/differential thermogravimetry (DTG)/differential scanning calorimetry (DSC), of uncoated and coated CLT specimens under oxidative conditions. During the applied medium-scale radiant exposure, the unexposed-face temperatures of both assemblies remained below the insulation temperature-rise limits defined in STN EN 1363-1; however, these limits were used only as a comparative benchmark and the test does not represent a formal fire-resistance classification. The coated assembly showed improved thermal protection during the early and intermediate stages of exposure, delaying a critical thermal event near the wooden stud by approximately 35 min. However, flaming combustion of the stud occurred at about 75 min and led to degradation of the intumescent char within the cavity. In contrast, the uncoated assembly reached higher early CLT surface temperatures but showed no flaming combustion during the test. STA results supported the fire-test interpretation: the coated specimen showed a 37% reduction in peak DTG rate, a higher residual mass at the end of the test, and substantially greater mass loss in the 150–280 °C range, consistent with intumescent activation and volatile release. The results indicate that, under the tested medium-scale exposure, the intumescent coating improved early and intermediate thermal protection of the CLT surface, but did not prevent late-stage cavity flaming involving the wooden stud. Therefore, the behavior of intumescent-coated CLT in partially enclosed cavities with combustible framing should be validated under replicated, standardized and larger-scale fire exposure. Full article

Traditional coal mining methods have led to prominent issues of coal resource waste and large-scale solid waste emissions. The integrated “excavation–backfilling–retention” mining technology for inter-section coal pillars and gate roads is one of the key technologies to solve these problems. However, the excavation and mining process associated with this technology imposes higher requirements on the ventilation system. Aiming at addressing the ventilation challenges existing during the implementation of the “excavation–backfilling–retention” method, research on ventilation safety assurance technology for inter-section coal pillars was carried out. Using COMSOL5.5 software, a full-stage ventilation system design model was constructed, adopting a ventilation mode that combines full-air-pressure ventilation with auxiliary local ventilation. The dynamic variation characteristics of the ventilation system under the “excavation–backfilling–retention” method and its capability to prevent and control the risks of O₂ and CO gas accumulation and coal spontaneous combustion were studied. The results show that during the bypass excavation period, the air supply from the auxiliary fan is sufficient, and during the excavation period for the two gate roads, due to the increased ventilation distance, insufficient airflow occurs near the heading face, accompanied by temperature rise, O₂ concentration decrease, and local CO accumulation, posing risks of coal spontaneous combustion and toxic gas accumulation. During the inter-section coal pillar excavation period and the cyclic operation period, after the full-air-pressure ventilation system is established, the airflow becomes stable, ventilation resistance decreases, and both temperature and gas concentrations are controlled within safe limits. However, in the corner areas, auxiliary local ventilation measures are still required due to insufficient O₂ and CO accumulation. The study verifies the feasibility and safety of the integrated “excavation–backfilling–retention” ventilation system, providing a safe ventilation approach for the integrated mining method and supporting the green mining of coal mines and the synergistic development of coal-based solid waste resource utilization. Full article

The global push for low-carbon electricity generation has made hydrogen-enriched natural gas an attractive near-term decarbonization option. This paper combines experimental and thermodynamic analyses of H₂–CH₄ combustion in gas turbine combustion chambers. Experiments were conducted on a patented two-stage swirl burner across 240 operating conditions. The effects of hydrogen fraction (γ = 0–40%), swirler vane angle (30°, 45°, 60°), equivalence ratio (φ = 0.17–1.00), and fuel injection strategy were measured against NOx and CO emissions and lean blowout stability. Each 10% increase in hydrogen content raised NOx by 23–24% via the Zel’dovich thermal mechanism, while CO fell by up to 28.5% at φ = 0.3 and 60° due to enhanced OH-radical activity. The minimum recorded NOx was 12.08 ppm (Type 2 injection, 30°, γ = 0%, φ = 0.3). Hydrogen addition improved lean blowout stability by 32–46% per 10% H₂. A parallel thermodynamic analysis showed that integrating an organic Rankine cycle (ORC) and supplementary H₂–CH₄ firing in the heat recovery steam generator cuts specific CO₂ emissions by 7.5–10% and raises net efficiency by 0.79–4.0 percentage points. Critical comparison with 28 published studies identified an optimal operating window: γ = 20–30%, φ = 0.5–0.7, 45° vane angle (SW = 0.8). Full article

This study investigated the co-combustion behavior of loblolly pine (LP100), kaolin clay (KC100), and LP-KC blends (LP75KC25, LP50KC50, and LP25KC75) using thermogravimetric analysis under air gas flow at heating rates of 5, 10, and 20 °C min⁻¹. The objective was to evaluate how biomass–mineral blending affects thermal degradation, reaction-stage development, kinetic behavior, and thermodynamic properties. The TGA-DTG results were interpreted using Coats–Redfern model-fitting kinetics, Flynn–Wall–Ozawa (FWO) model-free kinetics, and thermodynamic analysis. LP100 and LP-KC blends exhibited two main stages: Phase II oxidative devolatilization and Phase III char oxidation with overlapping kaolinite dehydroxylation, while KC100 showed one dominant high-temperature mineral transformation. In Phase III, the blends’ DTG peak temperatures ranged from 401.7 to 474.3 °C at 5 °C min⁻¹, 427.0 to 500.3 °C at 10 °C min⁻¹, and 478.3 to 509.0 °C at 20 °C min⁻¹. Coats–Redfern Ea values were 58.16–70.50 kJ mol⁻¹ for LP100 in Phase III, and 178.85–181.59 kJ mol⁻¹ for KC100 in Phase III, while the blends’ Ea values ranged from 24.07 to 81.31 kJ mol⁻¹ in Phase II and 30.00 to 59.59 kJ mol⁻¹ in Phase III. FWO analysis confirmed conversion-dependent Ea behavior, with KC100 showing the highest energy barrier. Thermodynamic analysis showed positive ∆G values of 170.59–188.34 kJ mol⁻¹ in Phase II and 197.38–240.84 kJ mol⁻¹ in Phase III. ∆H ranged from 19.67 to 76.55 kJ mol⁻¹ in Phase II and reached 172.53–175.43 kJ mol⁻¹ for KC100 in Phase III, while negative ∆S values of −0.07 to −0.28 kJ mol⁻¹ K⁻¹ indicated ordered activated complexes. In conclusion, LP lowered the apparent kinetic and thermodynamic barriers of KC transformation during co-combustion. Full article

Energy efficiency is a critical avenue for reducing carbonaceous emissions across fossil fuel value chains. Specifically, utilization of liquefied natural gas (LNG) exergy for power generation upon regasification in an import terminal offers the opportunity to partially retrieve the energy invested during liquefaction. Power generation arises as a promising avenue to accomplish this by using ambient air or seawater to supply heat to a working fluid, while the regasified LNG stream behaves as the heat sink of the thermal machine. However, a trade-off between cycle complexity (capital investment) and process efficiency exists. To identify it, in this work, three Rankine cycle configurations, which operate through indirect heat exchange without the need of fuel combustion, are analyzed with a consistent methodology from an exergo-economic perspective. Using a 2.13 mtpa LNG regasification terminal without LNG exergy utilization as the baseline for the techno-economic assessment, the simplest configuration consisting of a two-pressure level propane cycle (C₃) achieved an exergy efficiency of 34.0% and a levelized cost of electricity (LCOE) of 89.4 €/MWh. A cycle carrying out an expansion of a portion of the regasified LNG and employing a CO₂ loop for the high temperature range (C₁CO₂) achieved an exergy efficiency of 42.5% but with a higher LCOE of 99.7 €/MWh. Finally, the most capital-intensive design, comprising two stages with a hydrocarbon mixed refrigerant and propane as working fluids (MRC₃), reached an efficiency of 55.2% and a cost of electricity of 118.5 €/MWh. The exergy analysis revealed that minimizing the MITA of cryogenic exchangers should be prioritized to improve cycle performance. However, even when large LNG regasification capacities (>6 mtpa) are considered, the most cost-effective solution (C₃) generates profits during less than 45% of the time in the electricity market from 2024 of an LNG importing region such as Spain, indicating a relatively low economic potential for power generation without complementary heat sources. Full article