Search Results (374)

Fossil fuel depletion has increased interest in renewable alternatives such as biodiesel derived from non-edible plant oils. Droplet evaporation is a key process influencing fuel–air mixing and combustion efficiency in diesel engines. In this study, the evaporation characteristics of diesel and two non-edible biofuels, Jatropha and Castor, are investigated using computational fluid dynamics (CFD) under high-temperature and high-pressure conditions representative of engine environments. The numerical model incorporates the conservation equations of mass, momentum, and energy, together with the k–$\epsilon$ turbulence model and a discrete phase model to simulate droplet heating, motion, and mass transfer during evaporation. A comparative CFD analysis is performed to examine how fuel properties, ambient temperature, and droplet size affect the evaporation behaviour of diesel, Jatropha, and Castor droplets under identical engine-like conditions. The evolution of droplet diameter, temperature, velocity, and lifetime is analysed, and the applicability of the classical $D^2$-law is evaluated under different operating conditions. The results indicate that biofuel droplets generally evaporate faster than diesel droplets at lower temperatures, while evaporation trends become similar at higher temperatures. These findings provide insight into the evaporation behaviour of Jatropha and Castor fuels and their potential application in diesel engines. Full article

To overcome the low strength of conventional polytetrafluoroethylene/aluminum (PTFE/Al) reactive materials and the insufficient reaction efficiency of aluminum, this study introduces highly reactive aluminum–cerium alloys (Al-Ce-1#, -2#, and -3#, with Ce contents of 30, 50, and 70%, respectively; the primary phase in Al-Ce-3# is Al₂Ce) with a multiscale structural design (comprising both micron-sized and nano-sized particles) into an ammonium perchlorate (AP) matrix. Al/AP reactive materials and Al-Ce/AP reactive materials with varying Ce contents were prepared. The thermal decomposition characteristics, dynamic mechanical properties, and impact ignition behavior were systematically investigated using differential scanning calorimetry (DSC) and split Hopkinson pressure bar (SHPB) experiments. The results demonstrate that the addition of Al₂Ce significantly alters the thermal decomposition process of AP, substantially lowering its decomposition temperature (by approximately 69 °C) and promoting concentrated exothermic decomposition. SHPB tests reveal that Al₂Ce/AP composites exhibit higher dynamic yield strength and flow stress than the Al/AP, accumulating faster strain energy density under impact loading, which indicates a more violent fragmentation failure mode. This enhanced mechanical failure behavior, which provides highly reactive interfaces and promotes hotspot formation, synergizes with the catalytic effect of Al₂Ce on AP decomposition. Together, these mechanisms jointly improve the impact ignition sensitivity of the material, significantly lowering its ignition threshold and shortening its combustion duration. This study confirms that Al₂Ce/AP is a novel reactive material combining excellent dynamic mechanical properties with outstanding impact reactivity, providing theoretical and technical support for the application of highly reactive rare-earth aluminum alloys in aluminum-based reactive materials. Full article

The environmental impacts from fossil fuel use have accelerated the global transition to sustainable energy sources. Hydrogen has become a promising alternative due to its high energy density and clean combustion. However, hydrogen production streams are frequently contaminated with methane, which needs efficient, durable, and cost-effective purification technologies such as pressure swing adsorption (PSA). The present study provides a comparative evaluation of biomass-derived activated carbons and a commercial activated carbon for hydrogen–methane separation. High-surface-area activated carbons were synthesized from sustainable pine and birch precursors via chemical activation using potassium hydroxide (KOH, impregnation ratio 3:1) at 800 °C. Their dynamic adsorption performance was systematically assessed in a fixed-bed setup under a PSA system operating at pressures of 25, 35, and 50 bar, using a of hydrogen–methane gas mixture, where methane feed concentrations ranging from 10 to 30 vol%. This work focuses on the behavior of the adsorbent material and does not constitute a complete PSA process evaluation. The biomass-derived activated carbons showed well-developed textural characteristics, with specific surface areas up to 1416 m² g⁻¹, which exceeded that of the commercial reference material (1023 m² g⁻¹). This improved pore structure was reflected in their adsorption behavior at an operating pressure of 50 bar; the birch-derived carbon achieved a methane uptake of 10.5 mol kg⁻¹, more than twice the capacity of 5.30 mol kg⁻¹ measured for the commercial adsorbent. Beyond initial adsorption capacity, the study emphasizes operational durability and reusability. Cyclic adsorption–desorption experiments, supported by Raman spectroscopy, revealed pronounced structural changes in the commercial activated carbon under repeated operational stress, as indicated by an increase in the I_D/I_G ratio from 1.08 to 1.24. In contrast, the biomass-derived activated carbons preserved their morphological integrity and adsorption efficiency over successive cycles. These findings demonstrate that pine- and birch-derived activated carbons are not only sustainable alternatives but also operationally stable adsorbents capable for hydrogen purification processes. Full article

Prescribed burning is important for reducing wildfire risk and regulating fuel loads, but its implementation in mountainous forests is strongly influenced by the coupled effects of the wind field and topography, making it difficult to control. This study focuses on Yunnan pine (Pinus yunnanensis) forests in southwestern China. A three-dimensional Fire Dynamics Simulator (FDS) combined with measured fuel characteristics was used to simulate 21 slope (0–35°) and wind speed (0–2 m s⁻¹) combinations to quantitatively analyze the fire spread, flame structure, and gaseous emission characteristics during downslope prescribed burning. The local fire spread rate (ROS), evaluated along three lateral lines (Y = 2.5, 5.0, and 7.5 m), exhibits a non-monotonic dependence on slope over the tested range, with a minimum near 30° and a modest rebound at 35°. A downslope wind of 1 m s⁻¹ promotes near-surface heating and accelerates spread, whereas a stronger wind of 2 m s⁻¹ lifts flames away from the fuel bed and suppresses combustion. Thermal field analysis reveals that peak temperature decreases with increasing slope and that a late-stage secondary heating episode occurs at 35°. CO₂ emissions are significantly positively correlated with fuel consumption, reaching a peak of 717.5 kg under a 35° slope and no-wind conditions. CO emissions, as an indicator of combustion efficiency, reach their highest value of 2.23 kg at a 35° slope and a wind speed of 1 m s⁻¹, indicating that their trend is not entirely consistent with the ROS and temperature and that there is a certain degree of decoupling. The interaction between slope and wind speed transforms fire behavior from a cooperative to a competitive mechanism, and the topography–wind field coupling provides differentiated control over the combustion intensity and completeness. This study provides a scientific basis for the safe implementation of mountain burning programs and for regional carbon emission assessments. Full article

Under severe ice and snow weather, ice-covered pantograph–catenary arcs affect the safe operation of high-speed trains. This study investigates the impact of ice-covered arc electrical characteristics, plasma parameters, and material ablation mechanisms. By constructing a comprehensive pantograph–catenary icing experimental platform, arc voltage, current signals, high-speed dynamic images, and emission spectra were synchronously collected under different icing thicknesses ranging from 0 to 15 mm. Research indicates that ice coverture causes frequent “extinction–reignition” phenomena during the arc initiation stage due to the latent heat absorbed by melting ice, significantly reducing the initial stability of arc combustion. Spectral analysis confirms that the arc excitation temperature and energy density are positively correlated with the concentration of hydrogen ions produced by water vapor ionization, reaching a peak under the 5 mm icing condition. Experimental results show that the average energy density of ice-covered arcs is approximately double that of the non-iced condition, causing the ablation pits on the carbon strip to exhibit characteristics of greater depth and wider copper deposition zones. This study reveals the unique mechanisms and damage characteristics of icing pantograph–catenary arcs, providing an important basis for the safe design and maintenance of pantograph–catenary systems in high-cold railway environments. Full article

To address global carbon reduction demands, oxy-fuel combustion in circulating fluidized beds (oxy-CFB) has emerged as a highly promising carbon capture technology, offering extensive fuel flexibility and facilitating bioenergy with carbon capture and storage (BECCS). However, its commercialization is hindered by significant energy penalties and complex scale-up challenges. This review comprehensively analyzes the fundamental multiphase mechanisms, heat transfer behaviors, and multi-pollutant emission characteristics of oxy-CFB systems, drawing upon multiscale modeling advancements and operational data from pilot to 30 MW_th industrial demonstrations. Replacing air with an O₂/CO₂/H₂O mixture fundamentally alters gas–solid hydrodynamics and char conversion pathways, necessitating active fluidization state re-specification. Despite shifting optimal desulfurization temperatures and introducing recarbonation risks, the technology demonstrates inherent advantages in synergistic pollutant control, including the complete elimination of thermal NO_x. While atmospheric oxy-CFB is technically viable, transitioning to pressurized operation is critical to minimizing system efficiency penalties. Furthermore, integrating oxygen carrier-aided combustion (OCAC) and developing advanced predictive control strategies are essential to managing multi-module thermal inertia and enabling rapid dynamic responsiveness for modern power grids. Full article

Biodiesel composition largely affects its combustion and emission performance in diesel engines, while the pilot–main injection strategy has the potential to simultaneously improve engine efficiency and alleviate the soot–NO_x trade-off. Accordingly, soybean oil (SO), animal fat (AF), and waste cooking oil (WCO) biodiesels were numerically investigated under single injection and pilot–main double injection strategies with pilot energy ratios of 5.6%, 10%, and 15% over a range of main injection timings. The CFD framework was validated against the experimental in-cylinder pressure and AHRR, showing good agreement across the tested operating conditions. The results show that advancing the injection timing increases the AHRR peak and MPRR, whereas the pilot–main injection strategy reduces the AHRR peak and generally advances combustion phasing. A stable CA10 at injection timing ranges of 350–358 °CA persists across biodiesels and injection strategies. Emissions correlate with MICT, where NO_x increases while soot decreases with the rise in MICT, suggesting an intermediate MICT window for a balance between efficiency and emissions. Furthermore, at the respective highest gross ITE of biodiesels, SO provides the most favorable combination of MPRR and efficiency, whereas WCO shows lower NO_x but stronger indicators of incomplete combustion. Full article

The transition toward sustainable aviation fuels requires dedicated experimental platforms capable of evaluating alternative fuels under realistic propulsion conditions. This study presents the development and laboratory experimental validation of a modular testing installation designed for sustainable fuels derived from plastic waste pyrolysis, intended for aerospace engine applications. The proposed system is conceived as an integrated small-scale gas turbine assembly that reproduces the functional characteristics of a jet engine and enables controlled laboratory investigations of dynamic behavior, combustion stability, and performance. The installation comprises a compressor, annular combustion chamber, and turbine mounted on a common shaft, along with a fully autonomous fuel supply system equipped with electronically controlled pumping, safety devices, and thermal conditioning of the fuel mixture via an attached Stirling engine. Combustion processes are continuously evaluated using an exhaust gas analysis system to assess fuel composition and combustion quality, while a high-speed camera operating at 50,000 fps enables detailed visualization of flame stability. Operating parameters, including temperatures, pressures, rotational speed, mass flow rates, and thrust, are monitored and recorded through an integrated control and data acquisition system with real-time analysis capabilities. Experimental results demonstrate stable operation and reliable ignition using alternative fuel mixtures, confirming the suitability of the modular installation as a versatile research platform for the assessment and comparative analysis of sustainable aerospace fuels. Full article

Carbon fiber-reinforced polymer (CFRP) has been widely used in various fields due to its significant advantages. However, research on their pyrolysis and combustion behavior under fire conditions, which directly affects structural integrity and safety, remains insufficient. To challenge this issue, thermogravimetric analysis was employed to investigate the pyrolysis characteristics of the CFRP in both air and nitrogen atmospheres at heating rates of 20–40 °C/min with relevant pyrolysis kinetic parameters calculated using the Kissinger method. Fourier-transform infrared (FTIR) spectrometer was utilized to analyze pyrolytic gas species and concentrations at 40 °C/min in nitrogen atmosphere. Cone calorimeter tests at 50 kW/m² were conducted to obtain combustion characteristic parameters. Based on atomic conservation and oxygen-consumption principles, the equivalent molecular formula (CH_5.787O_0.541) of the epoxy resin pyrolysis gas and its combustion reaction equation were derived through reverse deduction. The heating, pyrolysis, and combustion processes of the CFRP (cone calorimetry specimen) were numerically simulated using Fire Dynamics Simulator (FDS). The predicted heat release rate, mass loss rate, and gas production rate showed good agreement with experimental results. Full article

Accurate temperature control in ceramic roller kilns is critical for ensuring product quality; however, it remains challenging due to nonlinear thermal dynamics and the spatial lag inherent in traditional contact-based sensors. To address the limitations of sparse wall-mounted thermocouples and optical interference in kiln images, this paper presents a multimodal spatiotemporal fusion network (MST-FusionNet) for noncontact temperature detection of ceramic bodies on roller tracks. The proposed network integrates in-furnace combustion image sequences with distributed thermocouple measurements. First, a physics-informed pseudo-heatmap generation strategy based on Gaussian distributions is introduced to align discrete thermocouple readings with visual features, enabling effective early-stage multimodal fusion. Second, a residual compensation mechanism uses thermocouple data as a stable reference to learn local temperature deviations from visual and temporal features. In addition, an attention-enhanced LSTM module is employed to model combustion dynamics and suppress unreliable frames caused by smoke and flame fluctuations. Experimental results on a real industrial dataset show that the proposed method achieves a mean absolute error of 0.9164 °C and a root mean squared error of 1.2422 °C, demonstrating better performance than single-modal methods and simple fusion baselines. The proposed framework exhibits stable spatial characteristics across different roller positions and helps bridge the spatial discrepancy between boundary measurements and the actual thermal state of ceramic products, providing an effective solution for temperature detection in roller kilns. Full article

This study introduces and compares online rule-based and optimization-based energy management strategies for a mild hybrid electric vehicle, with their performance evaluated against an offline Dynamic Programming benchmark. A structured rule-based strategy is proposed to enforce engine operation along its optimal efficiency line, while the remaining power demand is balanced by the electric motor. To achieve charge-sustaining battery operation, a soft state of charge regulation mechanism is incorporated. An Equivalent Consumption Minimization Strategy (ECMS) is also developed using a precise formulation of battery equivalent fuel consumption computed from instantaneous engine and electric path efficiencies, instead of constant efficiencies used in the literature. DP, which provides a globally optimal solution over the entire driving cycle, is employed as a benchmark for assessing the rule-based and ECMS strategies. The control strategies are compared under charge-sustaining conditions, considering engine and motor operation characteristics, overall fuel consumption, and battery usage intensity. Furthermore, the influence of load shifting between the internal combustion engine and the electric motor on overall vehicle performance is analyzed. Fuel consumption decreases by 13.5% relative to the engine-only baseline with the proposed ECMS with precise equivalent fuel consumption, and DP yields an additional 1.6% benefit. Compared with the developed rule-based controller, ECMS nearly halves the battery usage intensity, and DP provides 3.1% further reduction relative to ECMS. Full article

This paper presents an analysis of the dynamic parameters of vehicles powered by an electric drive unit based on a permanent magnet synchronous motor (PMSM) and a conventional drive system based on a spark-ignition combustion engine. The research subjects were a Mercedes-Benz EQA 250+ and an Audi A3 8V 35 TFSI with a turbocharged 1.5 dm³ engine. The paper presents an analysis of changes in power and torque as a function of engine speed (ICE) and driving speed of the electric vehicle (BEV). The study demonstrated fundamental differences, primarily the progression of the external characteristic curves of the engines and changes in vehicle dynamics. The research shows differences in the elasticity depending on the type of the drive motor. The research was conducted using a chassis dynamometer that allowed for a deeper understanding of the operation of the electric vehicle drive system and the identification of significant differences and dependencies in the external characteristics. Full article

Advances in high-performance computing have expanded the use of computational fluid dynamics (CFD) for reacting-flow analysis; however, simulations involving detailed flame kinetics remain computationally intensive for many practical systems. Efficient modeling approaches are therefore essential for predicting flame behavior in swirl-stabilized combustors. This study examines the influence of main-stage swirl intensity on near-lean blow-off characteristics in a multistage swirl combustor using a hybrid RANS–LES framework. The Stress Blended Eddy Simulation (SBES) model, coupled with a Flamelet Generated Manifold (FGM) combustion formulation, is employed to capture key turbulence–chemistry interactions. Results indicate that reducing swirl intensity suppresses the formation of a swirl-stabilized flame, while excessive swirl negatively affects emission performance. For the baseline (S2) and high-swirl (S3) configurations, flame lift-off height increases by 21.0% and 11.96%, respectively, for every 0.1 reduction in equivalence ratio. The S3 case also demonstrates reduced combustion efficiency, with CO emissions rising by 156.4% relative to S2. Local flame extinction is observed in regions of strong droplet–flame interaction, highlighting enhanced quenching susceptibility under near-blow-off conditions. The present study investigates the flame dynamics in a multi-stage swirl combustor using high-fidelity CFD simulations. This study has yet to be validated through experimental analysis and the results presented in this work are entirely computational. Further experimental validation is necessary to verify the results. Full article

The power package of high-speed internal combustion units generates complex excitation forces during operation. These forces cause excessive vibration in the driver’s cab, negatively affecting the driver’s working conditions. Therefore, optimizing the isolation system design is essential. This study established a rigid body dynamic model of a single-layer isolation system to determine initial stiffness parameters. A refined finite element (FE) model of the diesel locomotive body was also developed to analyze vibration characteristics. Using the global response surface method, multi-objective optimization was performed. The three-dimensional stiffness of the isolator served as the design variable, while the maximum force transmissibility at the vehicle reference point was the optimization objective. The optimization accuracy was verified through FE modeling, experiments, and simulations considering coupled wheel–rail excitations. Results showed that the force transmissibility at the cab’s center floor decreased from 44.05% to 32.65%. Furthermore, the comfort index met the requirements under all working conditions. These findings indicate that the proposed design method effectively improves the efficiency of the power pack isolation system and provides a valuable reference for future designs. Full article

With the deployment of Hydrogen-enriched Compressed Natural Gas (HCNG) technology, establishing market mechanisms adapted to its physical characteristics is crucial for renewable energy accommodation. However, existing studies lack HCNG pricing mechanisms that reflect calorific value fluctuations and often overlook the dynamic carbon emission characteristics of Hydrogen Mixed Gas Turbines (HMGTs). To address these gaps, this paper proposes a hierarchical optimization framework for Integrated RES-NG Providers (IRNPs) participating in multi-type markets. In the upper level, a bidding model involving electricity, HCNG, hydrogen, and CEP-GEC joint markets is established. A dynamic HCNG pricing mechanism based on the Wobbe Index is introduced to capture composition variations, and a refined HMGT model based on the modified Arrhenius equation is employed to quantify combustion-emission physicochemical kinetics. The lower level formulates market clearing models for social welfare maximization, which are transformed into a Mathematical Program with Equilibrium Constraints (MPEC) via KKT conditions. Case studies demonstrate that: (1) the refined HMGT model captures the dynamic fluctuation of the carbon emission factor between 0.6074 and 0.6216, correcting the bias of traditional static models; (2) the introduction of the dynamic HCNG pricing mechanism significantly enhances flexibility, increasing the renewable energy accommodation rate from 90.47% to 100%; (3) IRNPs maximize profits through multi-market arbitrage, achieving a daily total revenue of ¥2.231 million, a 30.9% increase compared to participating only in electricity–gas markets; (4) The critical thresholds for cross-market arbitrage are identified, and hydrogen is diverted to the hydrogen market when prices exceed 9.6 ¥/kg and completely prioritized over HCNG blending when prices surpass 15.6 ¥/kg. Full article