Search Results (2,728)

To investigate the early-stage flame propagation and pressure response of premixed H₂-O₂ combustion under ultra-high-pressure constant-volume conditions, a transient CFD model was developed for a large-volume confined chamber. The numerical framework combines a density-based solver, the Peng–Robinson real equation of state, large eddy simulation, and a reduced H₂-O₂ chemical kinetic mechanism. Simulations were conducted at initial pressures of 30 and 40 MPa, H₂/O₂ molar ratios of 8:1 and 12:1, and three-, four-, and five-point ignition configurations. The results show that increasing the initial pressure from 30 MPa to 40 MPa advances the pressure rise onset from approximately 1.65 ms to 1.28 ms and increases the maximum pressure rise rate from 18.6 MPa·ms⁻¹ to 27.4 MPa·ms⁻¹ under the H₂/O₂ = 8:1 and three-point ignition condition. Under the investigated fuel-rich conditions, increasing the H₂/O₂ molar ratio from 8:1 to 12:1 delays the pressure rise onset from approximately 1.28 ms to 1.46 ms and reduces the maximum pressure rise rate from 27.4 MPa·ms⁻¹ to 21.1 MPa·ms⁻¹. For the 30 MPa and H₂/O₂ = 8:1 cases, the four-point ignition case produces the largest pressure rise rate of approximately 23.5 MPa·ms⁻¹, whereas the five-point ignition case shows a lower pressure fluctuation amplitude of approximately 3.6 MPa. The present conclusions are based on CFD quantitative engineering predictions and should be further validated using quantitative experimental measurements. Full article

The influence of standardized driving-cycle characteristics on the dynamic and energy performance of a parallel hybrid electric vehicle controlled by a fixed-gain PID speed controller was investigated. A control-oriented MATLAB/Simulink model was developed, including an electric traction subsystem, an electric battery pack, a simplified internal combustion engine subsystem, a supervisory torque-split controller and longitudinal vehicle dynamics. The same controller configuration was evaluated under the FTP75, HWFET and US06 cycles, with the shorter cycles repeated to obtain comparable durations. Control quality was assessed using RMSE, MAE, IAE and ITAE, whereas energy performance was quantified using battery state-of-charge variation, fuel consumption, engine utilization and traction motor current loading. FTP75 yielded favorable performance, with RMSE = 0.265 m/s, fuel consumption of 4.824 L/100 km and an SoC decrease of 19.698%, whereas US06 proved severe, with RMSE = 4.567 m/s, fuel consumption of 10.328 L/100 km, an SoC decrease of 41.630% and a peak motor current of 580.9 A. Sensitivity analysis showed that ±20% PID-gain variations do not materially alter the principal conclusion, while supervisory energy-management parameters exert a stronger influence on the trade-off between tracking quality, fuel expenditure and charge maintenance. The results confirm that fixed-gain PID control is cycle-dependent and becomes inadequate under aggressive driving conditions. Full article

The transition toward carbon-neutral energy systems has accelerated interest in hydrogen-fueled combustion technologies, where efficient fuel–air mixing is essential for stable and clean combustion. In the present study, the mixing characteristics of under-expanded supersonic jets injected into a pressurized environment are numerically investigated using validated computational fluid dynamics simulations. Two nozzle configurations are examined: a straight nozzle and sudden-expansion nozzles with different expansion ratios and expansion locations. The governing compressible flow equations are solved using the rhoCentralFoam solver with the SST k–ω turbulence model. The numerical framework is validated against Sod’s shock tube solution and experimental data for under-expanded supersonic free jets. The results show that sudden-expansion nozzles significantly modify the shock-wave structure, jet penetration, and lateral spreading compared with the straight nozzle. Among the investigated configurations, nozzles with intermediate expansion-section lengths exhibited pronounced Mach-disk oscillations with a dominant frequency of approximately 10 kHz. The normalized supersonic core length decreased from 17.79 for the straight nozzle to 5.50 for the best-performing sudden-expansion configuration, while the normalized jet half-width increased from 0.82 to 1.70, indicating substantially enhanced mixing performance. The findings demonstrate that nozzle geometry strongly governs the trade-off between flow stability and mixing enhancement in high-pressure supersonic jets. Full article

Polycyclic aromatic hydrocarbons (PAHs) in farmland soils pose potential ecological and human health risks, yet their contamination characteristics and source-related risks in farmland soils across different river basins in China remain insufficiently understood. This present study analyzed 84 farmland soil samples from northeast (primarily the middle and lower reaches of the Songhua River and Liao River basin), central (primarily the middle reaches of the Yellow River basin and Dongting Lake system), northwest (primarily the middle and upper reaches of the Yellow River and Yarlung Zangbo River basin), and southern (primarily the upper reaches of the Pearl River and Yangtze River basin) China in order to assess the contamination characteristics, sources, ecological risks, and human health risks associated with 16 US EPA priority PAHs in the samples. The findings suggest that the 16 aggregate PAHs’ concentrations in Chinese farmland soils varied from 63.9 to 9637.7 μg/kg, with an average of 1919.3 μg/kg. A gradual decline was observed from north to south, with dibenz[a,h]anthracene (DahA) accounting for the highest proportion at 14.3%. Correlation analysis, principal component analysis, and positive matrix factorization jointly indicated that fossil fuel combustion, high-temperature combustion, and traffic-related emissions were the main PAH inputs to farmland soils. The results of the ecological risk assessment indicated that the northeastern region exhibited the highest PAH ecological risk, with 41.2% of sample plots demonstrating severe PAH contamination. Conversely, the southern region exhibited the lowest PAH ecological risk, with 73.9% of the sample plots demonstrating no ecological risk. The human health risk assessment found that non-carcinogenic risks for both children and adults were within safe limits, while carcinogenic risks for both groups were relatively high. DahA was identified as the primary carcinogen, accounting for 45.9% and 70.3% of the total carcinogenic risk for children and adults, respectively. Oral ingestion was the primary route of exposure. This study provides an integrated basin-scale assessment of PAH contamination and source-related risks in Chinese farmland soils, supporting targeted management of PAH inputs in agricultural environments. Full article

Coal chemical looping combustion (CLC) enables high-concentration CO₂ capture with low NOx emissions. However, coal-derived sulphur species in the fuel reactor (FR) present severe challenges, including oxygen carrier (OC) poisoning and CO₂ stream contamination. This study identifies coal-derived sulphur within the FR as the primary emission source and systematically characterises its release patterns during pyrolysis and gasification, comparing in-situ gasification CLC (IG-CLC) and chemical looping with oxygen uncoupling (CLOU). Coal sulphur distribution pathways and their governing factors are systematically investigated, followed by a comprehensive characterization of sulphur release behaviour during pyrolysis and gasification. We propose a novel perspective advocating a paradigm shift from passive sulphur tolerance to active in-situ sulphur capture through the rational design of Multifunctional Oxygen Carriers (MOCs). This review provides a comprehensive theoretical framework and practical guidelines for designing sulphur-resistant systems, thereby accelerating the industrial deployment of clean coal chemical looping technologies. Full article

Nickel ferrite (NiFe₂O₄) is one of the most studied inverse-spinel ferrites because it combines moderate saturation magnetization, comparatively high electrical resistivity, chemical stability, and broad synthesis flexibility. Yet the literature shows that the measured structure and magnetism of NiFe₂O₄ are not intrinsic constants; they evolve strongly with dimensionality, size, thickness, strain state, cation distribution, surface spin disorder, and synthesis pathway. This review develops a unified theoretical and literature-based interpretation of how dimensionality reshapes the structural and magnetic behavior of NiFe₂O₄ across bulk ceramics, nanoparticles, one-dimensional nanostructures, polycrystalline thin films, and ultrathin epitaxial films. The review is anchored in the two uploaded nickel ferrite attachments and expanded using internet-sourced journal literature on spinel inversion, surface effects, mechanochemical synthesis, sputtered and pulsed laser deposited thin films, and epitaxial ultrathin-film anomalies. The central novelty of this article is the formulation of a dimensionality-dependent framework in which the observed magnetic response is governed by a competition among three coupled factors: (i) the cation-distribution function, which controls the A–B superexchange balance and therefore the net ferrimagnetic moment; (ii) the microstructural coherence function, which measures how crystallinity, strain, defects, and anti-phase boundaries preserve or degrade exchange continuity; and (iii) the surface/interface spin-order parameter, which quantifies the loss or reconfiguration of magnetic order at free surfaces and buried interfaces. Within this framework, bulk NiFe₂O₄ behaves as a near-equilibrium inverse spinel with relatively stable magnetization, whereas nanoscale NiFe₂O₄ experiences strong spin canting and finite-size suppression due to the growing fraction of disordered surface spins. Thin films introduce a distinct regime in which strain, texture, anti-phase boundaries, substrate mismatch, and growth kinetics determine both anisotropy and magnetization. In ultrathin epitaxial films, off-equilibrium cation redistribution and interface-controlled electronic reconstruction may even generate magnetization values far above bulk expectations. The review also compares major synthesis routes—solid-state reaction, sol–gel, co-precipitation, hydrothermal growth, reactive milling, combustion, pulsed laser deposition, and radio-frequency sputtering—and explains why each route biases the final dimensionality-dependent properties differently. A set of word-style equations is provided to formalize spinel inversion, finite-size suppression, anisotropy scaling, coercivity trends, and superparamagnetic crossover. Beyond summarizing the field, the review proposes a regime map linking dimensionality to characteristic structural defects and magnetic signatures, and it identifies unresolved questions concerning the true origin of enhanced magnetization in ultrathin NiFe₂O₄, the interplay between anti-phase boundaries and strain, and the distinction between intrinsic inversion changes and extrinsic substrate artifacts. The resulting article offers a submission-ready, originality-focused review that positions dimensionality as the master variable governing structure–magnetism correlations in nickel ferrite. Full article

The second-hand Battery Electric Vehicle (BEV) market in Italy is affected by substantial information asymmetry, particularly with regard to battery State of Health (SOH), residual value, and expected maintenance costs. This lack of transparency limits consumer confidence and reduces the potential of used BEVs to support a broader and more inclusive electric mobility transition. In this study, a data-driven decision-support framework is developed to improve the evaluation of second-hand BEVs in the Italian market. The proposed approach combines market data collected from major online platforms with historical price reconstruction and an assessment of the information asymmetries that limit user confidence in the second-hand BEV market. It also incorporates a semi-empirical SOH estimation model based on observable vehicle characteristics. The results reveal a consistent depreciation gap between BEVs and comparable internal combustion engine vehicles across different market segments and indicate that battery-related uncertainty appears to be one of the factors associated with consumer hesitation. The framework shows that combining non-invasive battery-health estimation with maintenance-related information can support a more objective assessment of used electric vehicles. Overall, the study demonstrates the potential of integrated digital and engineering-based tools to reduce uncertainty and enhance transparency in the second-hand BEV market. Full article

This study investigates the effects of Cobalt Oxide (Co₃O₄) nanoparticles on engine performance as well as emission characteristics under various engine load situations in test fuel (MB10). Response Surface Methodology (RSM) was used to examine the experimental results to assess the impact of nanoparticle concentration (0–150 ppm) on combustion behavior. Brake thermal efficiency (BTE) and brake specific fuel consumption (BSFC) were performance metrics, and CO, HC, CO₂, and NO_x were emission characteristics. The findings demonstrated that the inclusion of nanoparticles and biodiesel had a major impact on emission behavior and performance. Because biodiesel contains more oxygen than diesel fuel, it reduces CO emissions while increasing CO₂ and NO_x emissions. By boosting heat transmission, the use of nanoparticles increased combustion efficiency; however, fuel atomization was adversely affected by high concentrations. With error rates under 10% for every response, RSM models showed excellent prediction accuracy. To achieve 21% BTE, 458.21 g/kWh BSFC, and minimum emission levels of 0.048% CO, 9.478 ppm HC, 5.415% CO₂, and 601.09 ppm NO_x, the optimization study identified the optimal operating condition with a 1.31 kW engine load and 80.36 ppm Co₃O₄ addition. The results verify that the proper dosage of nanoparticles can enhance the combustion performance of biodiesel while preserving acceptable emission levels. Full article

Meso-scale combustors experience major challenges associated with flame instability, excessive wall heat losses, and limited reactant residence time due to their high surface-to-volume ratios. This study numerically investigates the thermo-fluid behaviour of hydrogen-fuelled vortex flames in a frustum meso-scale combustor under stoichiometric conditions (φ = 1.0). Three outlet-diameter configurations of 6 mm, 8 mm, and 10 mm were analysed under stoichiometric hydrogen–air conditions at air mass flow rates of 40, 80, and 120 mg/s, corresponding to Reynolds numbers of approximately 624–1780, with Computational Fluid Dynamics (CFD) used to evaluate the influence of combustor geometry on thermal confinement, wall temperature distribution, and flame stabilisation characteristics. The numerical simulations were performed in ANSYS Fluent 14.0 using the RNG k–ε turbulence model coupled with the Eddy Dissipation combustion model. The results indicate that reducing outlet diameter significantly enhances thermal confinement and recirculation behaviour within the combustor core. The temperature contours showed a maximum flame temperature of approximately 2.23 × 10³ K, while the 6 mm outlet configuration produced a more compact and axially elongated high-temperature core compared with the 10 mm configuration. The 6 mm outlet enhanced thermal localisation by approximately 10.4% and increased residence time by 66.8% relative to the 10 mm outlet. The peak inner wall temperature ranged from approximately 752 K to 1085 K depending on outlet diameter and mass flow rate. The 6 mm outlet exhibited the highest average wall temperature of approximately 909 K, followed by the 8 mm outlet (879 K) and the 10 mm outlet (838 K). Compared with the 10 mm outlet, the 6 mm configuration increased the average wall temperature by approximately 8.5%, indicating improved thermal confinement and heat retention within the combustor. These results indicate that outlet diameter strongly influences the balance between thermal confinement, flame stabilisation, and flow resistance. Full article

The mitigation of anthropogenic climate change caused by fossil fuel combustion is a critical global challenge that necessitates a transition to renewable energy systems. Bioethanol represents a major renewable fuel, but first-generation production relies on edible feedstocks, which raises concerns regarding food security. Consequently, research is shifting toward second-generation bioethanol produced from abundant non-edible lignocellulosic biomass sources. This review comprehensively examines the potential of Candida krusei (synonyms: Pichia kudriavzevii, Issatchenkia orientalis) to serve as an alternative biocatalyst for second-generation bioethanol production. Compared with the first-generation bioethanol-producing yeast Saccharomyces cerevisiae, C. krusei exhibits superior physiological traits, such as thermo, acid, and inhibitor tolerances, enabling the utilization of several lignocellulosic feedstocks. This review summarizes the taxonomic and physiological characteristics of C. krusei, describes case studies on bioethanol production, and discusses strategies for reducing production costs. Furthermore, the technical and biosafety challenges associated with the industrial deployment of C. krusei are critically examined, including xylose metabolism limitations, scale-up constraints, and the management of its opportunistic pathogenic nature. A life cycle assessment perspective suggests that the unique physiological properties of C. krusei contribute to reducing greenhouse gas emissions and energy consumption throughout the entire production process, from pretreatment to downstream ethanol recovery. Full article

Coal combustion in large-scale power plants is a major source of atmospheric pollution, including SO₂, NO_x, particulate matter, and the halogen acids HCl and HF. Predicting HCl and HF emissions is challenging due to interactions among fuel composition, fly ash chemistry, combustion conditions, and flue gas dynamics. In this study, artificial neural network (ANN) models are developed from field experiments at the lignite-fired TPP “Kostolac B”. The models incorporate operational parameters (flue gas temperature and flow rate) and fuel/ash characteristics (moisture and total sulphur in coal and CaO content in ash) to estimate HCl and HF emissions. SHAP analysis identified key variables affecting halogen acid release. The developed ANN models achieved satisfactory predictive accuracy, with the test-set performances of RMSE = 2.05 mg/Nm³, R² = 0.80, and MAPE = 18.7% for HCl prediction, and RMSE = 3.23 mg/Nm³, R² = 0.83, and MAPE = 18.7% for HF prediction. SHAP analysis indicated that CaO content in fly ash and coal moisture are the primary drivers of HCl and HF emissions, while operating conditions and coal sulphur content influence emissions through non-linear interaction effects. The proposed ANN-SHAP framework provides a data-driven approach for emission prediction and interpretation, supporting decision-making in emission management. Full article

To address the urgent demand for eco-friendly and low-cost catalysts to replace toxic heavy-metal additives in energetic materials, this work focuses on developing biomass-derived copper-doped porous carbon (CuPC) as a high-efficiency catalyst for the thermal decomposition and combustion of molecular perovskite energetic material (H₂dabco)NH₄(ClO₄)₃(DAP-4). Biomass carbonaceous material has garnered extensive attention in many fields, owing to the low cost, high utilization efficiency, and environment protection. Herein, the CuPC catalysts were rationally designed and fabricated via the high-temperature carbonization treatment of biomass carbonaceous material precursor. The catalytic effects of CuPC on the thermal decomposition and combustion characteristics of DAP-4 were systematically investigated. The results revealed that CuPC possessed inherent catalysis property on the decomposition and combustion reaction of DAP-4. Cu_xO_y nanoparticles were uniformly distributed on the surface of carbonized biomass substrates, endowing the catalysts with superior dispersibility. Thermal analysis results indicated that the addition of 5 wt% CuPC-3 reduced the thermal decomposition peak temperature from 378 °C of raw DAP-4 to 350 °C of DAP-4/CuPC-3. Moreover, the apparent activation energy of DAP-4 was notably decreased with the incorporation of CuPC catalysts. The combustion characterization results demonstrated that DAP-4 exhibited a more intense combustion process with the addition of CuPC, accompanied by elevated maximum combustion temperature and enhanced combustion heat. The catalytic mechanism of CuPC on the thermal decomposition and combustion of DAP-4 was further proposed. This work provides a targeted strategy for designing sustainable biomass-based catalysts to optimize the energy release performance of advanced molecular perovskite energetic materials. Full article

During the industrial restructuring in China, numerous outdated coking enterprises were phased out. Despite the cessation of production for several years, the soil in the production area of the retired coking plant remains heavily contaminated with polycyclic aromatic hydrocarbons (PAHs), which continue to adversely affect soil health. However, research on the pollution characteristics of soil PAHs under prolonged PAH exposure and the associated changes in functional genes related to soil carbon cycling is still inadequate. This study aims to identify the pollution characteristics and ecological risks of PAHs in the coking plant and to investigate the effects of long-term PAH contamination from abandoned coking plants on the functional genes involved in soil carbon cycling. It was found that PAHs in the soil were predominantly composed of high-molecular-weight PAHs (HMW-PAHs), which constituted 65.7% to 83.4% of the total PAH content. The total concentration of PAHs in the surface soil ranged from 3.79 to 554 mg·kg⁻¹, with an average concentration of 147.6 mg·kg⁻¹. Source analysis based on isomer ratios indicated that PAHs primarily originated from the combustion of coal and biomass. Utilizing the toxicity equivalent factor (TEF) method, we found that the PAH levels in the CA group exceeded the Serious Risk Concentration, indicating that PAH pollution poses a potential threat to the ecological environment. Metagenomic analysis revealed that the gene abundance of alpha-amylase in the CA group was significantly higher than that in the OLA group (p < 0.05), suggesting that prolonged exposure to PAHs has enhanced the starch hydrolysis capabilities of soil microorganisms. The findings of this study refine methods for assessing the risks associated with soil PAH contamination and provide a theoretical foundation for the risk management and reuse of retired coking plant sites. Full article

This study presents experimental investigations of a hydrogen power unit operating on hydrogen–oxygen gas mixtures produced by water electrolysis (HHO gas). The system was operated with additional molecular hydrogen enrichment in order to investigate the influence of hydrogen concentration on combustion characteristics and system performance. The flame temperature of the HHO + H₂ mixture was measured as a function of hydrogen concentration. The results show that the flame temperature increases nonlinearly with hydrogen content, approaching ~2800 °C under the investigated conditions at about 30 vol.% hydrogen in the enriched mixture. Despite the increase in flame temperature, the effective calorific value of the HHO + H₂ mixture remains significantly lower than that of pure hydrogen because the electrolysis-derived gas contains oxygen and excess water vapor. The presence of water vapor acts as a thermal diluent, influencing combustion behavior and suppressing autoignition under the investigated operating conditions. Optimal operating parameters for the hydrogen power unit were determined from experimental measurements. The results indicate that hydrogen-enriched HHO mixtures can be operated safely under controlled conditions and may represent a potential working medium for hydrogen-based energy conversion systems. Full article

Urban air quality management has been playing a significant role due to its effects on public health and pollution characteristics of countries with constantly changing policies. Traditional approaches capture how much pollution is present but are unable to detect changes in the chemical character of the atmosphere, the relationships between co-emitted species, the balance of photochemical processing, and the combustion fingerprint of emission sources. This study introduces a framework that identifies and diagnoses such evolutions within the pollutants of the atmosphere. A chemistry-aware Variational Autoencoder is trained on 19 multivariate pollution features (7 raw concentrations, 5 chemical ratios, 7 temporal gradients) at London Marylebone Road (urban roadside) and North Kensington (urban background) from 2015 to 2019, and tested on 2022–2025. A four-method ensemble framework (VAE reconstruction error, reconstruction probability, Isolation Forest, and statistical Z-score) requires ≥3 agreement to identify high-confidence departed pollution states. Per-feature decomposition of the reconstruction probability diagnoses the chemical character of each departure. At the roadside site, 14.5% of post-COVID hours fall within departed states, dominated by the CO/NO_x combustion ratio (513.2) and the photostationary state proxy (391.4), chemical relationships rather than individual concentrations. This indicates that at the point of emission, London’s fleet modernisation and Ultra Low Emission Zone (ULEZ) have changed the combustion fingerprint and photochemical equilibrium. The same structural indicators are carried over during the COVID-19 lockdown; however, O₃ rises 3.2× during the pandemic period, reflecting suppressed NO titration. Conversely, at the urban background site, where the departures are driven by concentrations and boundary-layer trapping ($r=-0.659$), the combustion fingerprint of the atmosphere is invisible to detect (CO/NO_x$=-45.0$). These findings indicate that London’s emission landscape has undergone fundamental transformations over the past decade, and the consequences of ULEZ and similar interventions or greater impacts of pandemic-related events are non-homogeneously distributed across the relevant region. Full article