Search Results (168)

Leveraging existing subsea natural gas pipelines for hydrogen blending offers a practical route for offshore low-carbon energy transport. However, traditional T-pipes require long distances to achieve uniform mixing conditions, raising the risks of stratification and hydrogen embrittlement. In this study, the conventional pipe fittings—elbows are innovatively adopted as passive mixing elements for hydrogen-blended natural gas pipes, expecting to use curvature-induced secondary flow and vortex reorganization to accelerate homogenization without extra flow mixers. Numerical simulations were performed to investigate the effects of the distance L₁ between the hydrogen branch and the elbow inlet and the elbow curvature radius R_c. Hydrogen distributions, coefficient of variation, homogeneous mixing path, and flow vorticities were analyzed to make comparisons between the elbow configurations and the conventional T-pipe. The results show that a smaller L₁ shortens the homogeneous mixing path S_h, while a smaller elbow curvature radius R_c generates stronger secondary flows but also intensifies the asymmetric hydrogen enrichment induced by centrifugal force. The mixing effect of the elbow configuration is more significant when HBR ≥ 20%, which gradually weakens as the HBR decreases. In this paper, the shortest mixing path S_h = 11.73 m is obtained in the optimal structure with L₁ = 0 and R_c/D = 4, achieving a reduction of 67.3% relative to the conventional T-pipe. It proves that elbow structures can significantly enhance the mixing efficiency of hydrogen-blended natural gas pipes, providing new solutions for hydrogen blending in offshore pipelines. Full article

Research on atomized drag-reducing agent (DRA) delivery in hydrogen-blended natural gas (HBNG) pipelines is limited, although inlet-section droplet transport and wall interaction are of practical importance. A three-dimensional CFD–DPM model of a $15\mathrm{m}$ straight pipe equipped with a pressure–swirl hollow-cone atomizer was developed to evaluate the effects of atomization pressure drop, injection mass flow rate, spray cone angle, nozzle orifice diameter, hydrogen blending ratio, and operating pressure. Numerical robustness was assessed through mesh and parcel-number independence tests, turbulence-model sensitivity analysis, representative simulations at $\mathrm{MPa}$-level operating pressures, and qualitative comparison with published pressure–swirl spray experiments. Increasing atomization pressure drop from $0.5$ to $5\mathrm{MPa}$ reduced the Sauter mean diameter from $120.07$ to $32.85\mathsf{\mu }\mathrm{m}$ and the numerical wall-trapping ratio from 32.96% to 13.68%, with diminishing changes above approximately $2\mathrm{MPa}$. Higher injection mass flow rates increased droplet size and numerical wall trapping, whereas larger cone angles intensified radial migration and caused severe inlet-localized trapping at ${80}^{\circ }$. Nozzle orifice diameter and hydrogen blending ratio showed weaker effects. Increasing operating pressure from $101,325\mathrm{Pa}$ to $2\mathrm{MPa}$ reduced the SMD from $54.60$ to $9.91\mathsf{\mu }\mathrm{m}$ and the numerical wall-trapping ratio from 15.88% to 5.96%. These model-dependent trends require high-pressure spray, flow-loop, or field validation before engineering application. Full article

Continuous carbon anode roasting in industrial parks requires a stable high-temperature heat supply and remains highly dependent on grid electricity and natural gas. However, existing energy-system studies rarely coordinate hydrogen production and storage, volumetric hydrogen blending, and temperature-graded waste-heat recovery under continuous production constraints. To address this gap, this study proposes an electricity–heat–gas–hydrogen integrated energy system for carbon anode industrial parks and develops a 24 h multi-objective scheduling model. The model coordinates heat demands at different temperature levels with hourly electricity and hydrogen flows, using surplus photovoltaic power to produce hydrogen for later high-load periods. The selected scheme achieves a daily volumetric hydrogen-blending ratio of 10.79%, with an operating cost of 82,985.75 CNY and carbon emissions of 54,371.53 kg. Relative to an otherwise equivalent non-hydrogen configuration, hydrogen coupling provides additional reductions of 7.2% in operating cost and 2.3% in carbon emissions. Compared with a basic conventional configuration, operating cost and carbon emissions decrease by 27.9% and 26.0%, respectively. Cascade recovery also increases the daily waste-heat utilization rate by approximately 30 percentage points. These results show that the proposed scheduling framework can coordinate hydrogen utilization and graded waste-heat recovery while maintaining continuous carbon anode production. Full article

The increasing adoption of hydrogen as an energy carrier requires advanced monitoring solutions for transport infrastructures, where intelligent sensing and data-driven analysis can play a key role in improving safety and operational efficiency. However, anomaly detection in hydrogen transport networks remains challenging due to the limited availability of operational data and the complexity of transient behaviors associated with these systems. This work investigates a weakly-supervised anomaly detection framework for hydrogen transport networks based on high-fidelity simulation and data-driven analysis. The proposed methodology combines temporal deep learning architectures and unsupervised representation learning models with an operational threshold calibration strategy based on the trade-off between false positives and false negatives. The proposed framework is validated using a high-fidelity simulation environment that reproduces normal and anomalous operating conditions, including leaks, compressor malfunctions, and delayed activation events. The framework is evaluated through comparative experiments involving different anomaly detection architectures, robustness analysis under measurement noise, and leave-one-topology-out generalization tests. Results demonstrate that the proposed approach can effectively identify abnormal behaviors while maintaining robustness against degraded signal quality and previously unseen operating configurations. The obtained results highlight the effectiveness of the proposed methodology as a framework for developing and validating intelligent monitoring strategies for hydrogen transport infrastructures. Full article

The decarbonization of industrial steam production, representing up to 57% of energy use in the food industry, is critical for achieving EU climate neutrality goals. This study developed an integrated digital framework for the research project Hy4GreenSteam to optimize green-hydrogen integration through advanced predictive modeling. The employed LightGBM gradient-boosting algorithms were trained on 68,697 PV power measurements and 57,000 meteorological observations from 2020 to 2022. A “Production-Split” methodology was introduced for 24 h ahead forecasting, segmenting training into high (>2 kW) and low (≤2 kW) production regimes to manage solar heteroscedasticity. Results show the 15 min model achieved an R² of 0.868 and the 1 h model an R² of 0.832, while the day-ahead model—trained exclusively on information available at forecast issue time—achieved an R² of 0.701, a 70% relative improvement over same-time-yesterday persistence. A complementary regime analysis shows that the production regime is predictable with 90.7% accuracy and quantifies the accuracy headroom of regime-specialized models (oracle R² 0.794). These methods were integrated into a real-time React-based platform that calculates optimal H₂/CH₄ blending; for the reference pilot configuration, driven by measured on-site PV generation, the computed CO₂ emission reduction reaches 34% relative to natural-gas-only operation during high-solar operating intervals. Predictive modeling combined with a Digital Twin interface provides a TRL 6 decision-support solution, demonstrated in a relevant industrial environment, for managing renewable sources in industrial hydrogen applications. Full article

Natural-gas-fired boilers remain widely used for building and industrial heat, making NOx control relevant even as energy systems decarbonize. This comprehensive review synthesizes the published literature on staged combustion, flue-gas recirculation (FGR), premixed combustion, oxy-fuel combustion, humidified combustion, catalytic combustion, flameless/MILD combustion, and integrated systems. The evidence indicates that staged burners and moderate external FGR are the most mature retrofit options, whereas lean premixed combustion is generally better suited to new or deeply retrofitted small and medium boilers. Humidification coupled with waste-heat recovery can reduce NOx while increasing total heat recovery, but water management, corrosion, fouling, and auxiliary demand must be considered. Oxy-fuel/FGR systems facilitate CO₂ capture but impose substantial oxygen-production, recycle, and CO₂-conditioning requirements. Hydrogen blending widens lean operability while increasing flashback sensitivity and altering thermal-NO and NNH chemistry. Technology selection should therefore balance NOx, CO, efficiency, stability, auxiliary resources, retrofit constraints, and long-term reliability. Full article

Blending hydrogen into existing natural-gas pipeline networks provides a practicable route toward future low-carbon applications. A Venturi-type mixer is a classical high-efficiency static gas-mixing device, and clarifying the effects of its structural parameters is important for efficient transport and downstream combustion stability. In this study, numerical simulations were performed in ANSYS Fluent 2024 R1. The contraction angle, throat length, and diffuser angle were selected as representative structural variables. First, the independent effects of these variables on the mixing process were examined through single-factor simulations. Then, three key levels of the three structural parameters were selected to establish a Box–Behnken experimental matrix for response-surface modeling. Based on the numerical results, entropy weighting and a genetic algorithm were used for multi-objective optimization, and the final solution was verified using the TOPSIS method. The results show that the optimized Venturi-type mixing device with optimized parameters of a contraction angle of 20.7°, a throat length of 60 mm, and a diffuser angle of 5° can reduce flow energy loss while maintaining high mixing uniformity. The diffuser angle is the dominant geometric parameter affecting both energy loss and mixing behavior. Compared with the reference central-point structure design, the overall TOPSIS score of the optimized structure increased from 0.41 to 0.82; the pressure loss decreased from 258.94 Pa to 206 Pa, corresponding to a reduction of approximately 20%; and the final-section mixing uniformity decreased only slightly, from 97.85% to 97.43%. Full article

Pushing ahead in materials chemistry means building tiny substances that work hard and take into account clean power, planet care, life science all at once. From this effort comes a new direction: ZIF-8, a metal-linked cage structure, now fused with active components extracted from the common fungus Aspergillus nidulans. Not just mixed, but grown together with fungal extracts tucked neatly into the skeleton of the material while keeping its orderly shape intact. Three versions appeared—loaded at 2%, 4%, and 6 weight percent—and each one was mapped out using X-ray signals, sharp images from electron scans, and element tracing. A light flickered on and off during tests in which electricity flowed through these new composites set between three points, designed to split water and release hydrogen gas. Surprisingly, the ZIF-8@2% nidulans blend showed strong teamwork between electricity- and light-driven biology, creating a sharp spike in temporary current while cutting down reaction delay to just 310 mV/dec—pushing hydrogen release through a faster molecular handshake. In this mix, natural compounds from fungi act like tiny solar collectors, helping electrons move more freely, which is reflected in impedance scans as lower resistance. On top of that, higher doses of the material effectively blocked harmful microbes, thanks to ZIF-8 breaking cell walls and active fungal ingredients punching holes as well. Instead of relying on harsh chemicals, it uses a nature-inspired design in which molds meet synthetic frameworks, creating a single system with potential for sustainable energy generation and antimicrobial applications. Full article

When methane (natural gas) fuel gas turbines switch to hydrogen–ammonia co-fuel, their thermodynamic performance undergoes significant changes. To expand the operating range of heavy-duty gas turbines when using hydrogen–ammonia co-fuel and to improve their thermodynamic performance, based on the 255.6 MW heavy-duty gas turbine at the Banshan Power Plant in Hangzhou, China, a simulation model was established. A strategy based on changing the angle of the compressor inlet guide vanes (IGVs) was proposed. The thermodynamic performance, turbine stage supercritical flow velocity, and flow matching characteristics of gas turbines were studied under different hydrogen–ammonia mixing ratios. The results indicate that the developed model can accurately predict the performance of the gas turbine under rated operating conditions, yielding a rated output power of 254.59 MW and an efficiency of 36.33%, with relative errors of −0.4% and −1.54% compared with the design values, respectively. When hydrogen–ammonia blended fuel is employed, the outlet Mach numbers of the second- and third-stage turbine stators exceed the safety limit unity. Reducing the IGV angle effectively decreases the turbine stator outlet Mach number and improves operational safety, although a slight reduction in gas turbine efficiency is observed. As the ammonia volumetric fraction in the blended fuel increases, the gas turbine output power increases while the efficiency decreases slightly, accompanied by a reduction in turbine stator outlet pressure and an increase in outlet temperature. Further investigation shows that, after IGV regulation, the combustor outlet pressure, gas turbine power output, and efficiency all increase. Under a fixed IGV opening condition, the gas turbine efficiency gradually decreases with increasing ammonia volumetric fraction. Under off-design fuel flow conditions, increasing the relative fuel flow leads to higher combustor outlet pressure and temperature, whereas increasing the ammonia volumetric fraction causes a slight reduction in these parameters. This research can provide theoretical support for the optimal design and operation of gas turbines using hydrogen–ammonia mixed fuel. Full article

Hydrogen blending into natural gas grids can support early renewable hydrogen deployment, but admissible injection depends on local gas flow, blending limits, and upstream hydrogen concentrations. This paper analyses these effects for a regional high-pressure gas-grid section in Styria, Austria, with two hydrogen injection points. A transient gas-network model derives time- and location-dependent injection limits, which are integrated into an electrolyser dispatch optimisation with fixed trailer demand and annual gas-grid injection demand. Three cases are compared: unrestricted injection, a “CH₄-based” limit without upstream hydrogen, and an “H₂-aware” case representing potential upstream hydrogen injection. For the analysed configuration, blending constraints shift operation away from favourable electricity-price periods, particularly when low prices coincide with reduced gas demand. In the 2025 reference case, the “H₂-aware” constraint increases the electricity-cost contribution from 4.22 to 5.45 EUR/kg_H2. A robustness analysis using electricity-price series for 2020, 2022, and 2025 shows that the “H₂-aware” constraint increases the electricity-cost contribution by 15.8–29.1% relative to unrestricted injection. The results demonstrate that dynamic gas-grid constraints should be considered when assessing blending-based electrolyser projects, while the quantitative findings remain specific to the analysed network and assumptions. Full article

This study investigates hydrogen-assisted fatigue crack growth (FCG) in vintage pipeline steels to quantify grade-dependent degradation under hydrogen–natural gas blending conditions. Fatigue behavior was evaluated using compact-tension specimens extracted from API X52 and X70 pipeline steels and tested in natural gas–hydrogen mixtures at a total pressure of 6.9 MPa and ambient temperature. Hydrogen concentration was systematically varied from 0% to 100% H₂ to assess its influence on crack-length evolution, fatigue crack growth rate, and fracture morphology. Crack propagation was characterized as a function of the stress-intensity-factor range, and scanning electron microscopy was used to examine hydrogen-induced changes in fracture mechanisms. The results demonstrate that FCG accelerates as hydrogen concentration increases, with a strong dependence on steel grade. X70 exhibited substantially greater hydrogen-induced FCG acceleration than X52, despite showing better fatigue resistance under hydrogen-free conditions. Fatigue life reductions approached 60% for X70 at 100% hydrogen, compared with approximately 30% for X52 under the same conditions. Significant early-life sensitivity was observed in X70 even at low hydrogen concentrations, whereas X52 showed more pronounced acceleration during later stages of crack growth. The influence of hydrogen was nonlinear and tended to stabilize at elevated blend fractions, indicating a saturation-type response once hydrogen-assisted crack growth became dominant. Fractographic analyses revealed a transition from ductile tearing in natural gas environments to terrace- and facet-controlled crack propagation in hydrogen-rich environments, accompanied by secondary cracking and river-pattern features. These findings demonstrate that hydrogen–natural gas blending can significantly alter fatigue crack growth behavior and relative material performance in pipeline steels, highlighting the need for grade-specific integrity assessment of existing pipeline infrastructure. Full article

To supply hydrogen to the geographically decoupled demand sites, efficient hydrogen transport is necessary. The existing natural gas pipelines represent a promising transport solution, with the blended hydrogen content expected to steadily increase. An open issue of hydrogen blending is the mixing behavior. Therefore, the effects of different geometric parameters (diameters, angles), operating conditions (velocities, concentrations), and injection layouts (single- and multi-point) on the mixture quality during direct injection of hydrogen into a natural gas pipeline are studied using 3D CFD. The main goal is to find parameters and layouts leading to sufficient mixing quality over a range of operating conditions. The mixing quality is determined based on the coefficient of variation (COV). The results show that the momentum flux ratio is a key parameter governing the mixing behavior. However, a high momentum flux ratio alone does not guarantee sufficient uniformity for all operating conditions. For the investigated range, single-point injection cannot ensure reliable mixing quality, whereas multi-point layouts with higher hydrogen inlet velocities achieve sufficient uniformity. Full article

The decarbonization of energy systems has intensified interest in hydrogen-enriched natural gas (H₂NG) as a transitional fuel for combined heat and power (CHP) units and micro-CHP systems. This review consolidates experimental and numerical studies that explore the energy, environmental, and techno-economic implications of H₂NG blends in CHP applications. Research conducted over the last decade highlights that enriching natural gas with hydrogen extends the flammability limits, enhances combustion stability, and reduces CO₂ and CO emissions, while maintaining or improving electrical efficiency. However, these benefits are accompanied by higher NO_x formation under stoichiometric conditions, which can be mitigated by operating under lean-burn regimes. The review further examines hybrid solutions that integrate electrolyzers, photovoltaic systems, and oxygen-enriched combustion to improve system flexibility and sustainability. The findings consistently show that moderate hydrogen fractions (5–20% vol.) provide optimal trade-offs between efficiency gains and emission control, supporting the role of H₂NG as an intermediate step toward fully hydrogen-powered CHP technologies. Technical challenges related to ignition control, thermal recovery efficiency, and infrastructure adaptation are also discussed, along with emerging strategies for techno-economic optimization. This comprehensive assessment contributes to understanding how hydrogen blending can accelerate the transition to low-carbon, distributed energy systems. Full article

Growing interest in transporting hydrogen via natural gas pipelines highlights the need to understand flame characteristics during accidental leakage. However, limited literature is available on addressing the flame horizontal projection length of hydrogen-blended natural gas jet fires under inclined conditions. Therefore, a series of experiments was conducted to investigate inclined H₂/CH₄ jet fires, with methane used as a surrogate for natural gas. Experiments with hydrogen content ranging from 0% to 20% were performed to examine the effects of inclination angle (0°, 30°, 45°, 60°, and 90°), nozzle diameter (2, 3, and 4 mm), and gas flow rate (4–25 L/min) on the flame morphological characteristics. It was found that the flame color evolves from a transparent blue base to a yellow luminous tip with increasing hydrogen content or fuel exit velocity, accompanied by soot enrichment in the luminous region. The flame horizontal projection length was quantified under different conditions. Results show it is only slightly affected when the hydrogen content is below 20%, whereas it increases with fuel exit velocity and nozzle diameter, and decreases with inclination angle. An explicit model was proposed by introducing the dimensionless heat release rate (${\dot{Q}}^{*}$), which predicts the flame horizontal projection length with good agreement with experimental data. The findings provide a basis for the safety design and risk assessment of hydrogen-blended natural gas pipelines. Full article

Natural gas metering is shifting from volume-based measurement to energy-based assessment as gas sources diversify, pipeline networks become more interconnected, and gas quality varies more strongly across time and space. This review examines the key technologies required for natural gas energy metering and evaluates how they support full-chain traceability from production to end use. The reviewed topics include flow measurement, gas composition analysis, calorific value determination, temperature-pressure compensation, state correction, uncertainty evaluation, intelligent data acquisition, and metrological traceability. The literature shows that individual technologies have advanced substantially. Ultrasonic flowmeters, rapid gas-quality sensing methods, dynamic calorific value allocation models, high-accuracy equations of state, and digital metering platforms have improved the technical basis of energy metering. However, these advances remain more mature at the level of individual links than at the level of the complete metering chain. Under multi-source supply, gas-quality fluctuation, hydrogen blending, and digitalized operation, the main challenge is to maintain consistency, uncertainty control, online verification, data credibility, and auditability across different metering stages. Future development should therefore focus on dynamic calorific value allocation, robust state correction under variable gas quality, full-chain uncertainty propagation, online verification, and secure data management for traceable natural gas energy metering. Full article