China, People’s Republic

Hydrogen leakage is a critical safety concern for high-pressure storage systems where orifice geometry significantly influences dispersion and risk. Previous studies on leakage and diffusion have mostly focused on closed or semi-closed environments while thorough exploration has been conducted on open and unshielded environments. This work compares three typical orifice types—circular slit and Y-type—through controlled experiments. Results show that circular orifices generate directional jets with steep gradients but relatively low concentrations with a 1 mm case reaching only 0.725% at the jet core. Slit orifices exhibit more uniform diffusion; at 1 mm concentrations ranged from 2.125% to 2.625%. Y-type orifices presented the highest hazard with 0.5 mm leaks producing 2.9% and 1 mm cases approaching the 4% lower flammability limit within 375 s. Equilibrium times increased with orifice size from 400–800 s for circular and slit leaks to up to 900 s for Y-type leaks some of which failed to stabilize. Response behavior also varied: Y-type leaks achieved rapid multi-point responses (as short as 10 s) while circular and slit leaks responded more slowly away from the jet core. Overall risk ranking was circular < slit < Y-type underscoring the urgent need for geometry-specific monitoring strategies sensor layouts and emergency thresholds to ensure safe hydrogen storage.

With the growing significance of hydrogen in the global energy transition research on its pricing mechanisms has become increasingly crucial. Focusing on hydrogen markets predominantly supplied by electrolytic production this study proposes a nodal marginal hydrogen price decomposition algorithm that explicitly incorporates the time-delay dynamics inherent in hydrogen transmission. A four-dimensional price formation framework is established comprising the energy component network loss component congestion component and time-delay component. To address the nonconvex optimization challenges arising in the market-clearing model an improved second-order cone programming method is introduced. This method effectively reduces computational complexity through the reconstruction of time-coupled constraints and reformulation of the Weymouth equation. On this basis the analytical expression of the nodal marginal hydrogen price is rigorously derived elucidating how transmission dynamics influence each price component. Empirical studies using a modified Belgian 20-node system demonstrate that the proposed pricing mechanism dynamically adapts to load variations with hydrogen prices exhibiting a strong correlation with electricity cost fluctuations. The results validate the efficacy and superiority of the proposed approach in hydrogen energy market applications. This study provides a theoretical foundation for designing efficient and transparent pricing mechanisms in emerging hydrogen markets.

The operational optimization of industrial boilers utilizing hydrogen-enriched natural gas is constrained by two critical gaps: insufficient understanding of the coupled effects of hydrogen blending ratio equivalence ratio and boiler load on combustion performance— compounded by unresolved challenges of combustion instability flashback and elevated NOx emissions—and a lack of systematic investigations combining these parameters in industrial-scale systems (prior studies often focus on single variables like hydrogen fraction). To address this a comprehensive computational fluid dynamics (CFD) analysis was conducted on a 2.1 MW industrial boiler employing the Steady Laminar Flamelet Model (SLFM) with a modified k-ε turbulence model and the GRI-Mech 3.0 mechanism. Simulations covered hydrogen fractions (f(H2) = 0–25%) equivalence ratios (Φ = 0.8–1.2) and load conditions (15–100%). All NOx emissions reported herein are normalized to 3.5% O2 (mg/Nm3 ) for regulatory comparison. Results show that increasing the hydrogen content raises the flame temperature and NOx emissions while reducing CO and unburned hydrocarbons; a higher equivalence ratio elevates temperature and NOx with Φ = 0.8 balancing efficiency and emission control; and reducing load significantly lowers furnace temperature and NO emissions. Notably the boiler’s unique staged-combustion configuration (81% fuel supply to the central rich-combustion nozzle 19% to the concentric lean-combustion nozzle) was found to mitigate NOx formation by 15–20% compared to single-inlet burner designs and its integrated cyclone blades (generating maximum swirling velocity of 14.2 m/s at full load) enhanced fuel–air mixing which became particularly critical for maintaining combustion stability at low loads (≤20%) and high hydrogen blending ratios (≥20%). This study provides quantitative trade-off insights between combustion efficiency and pollutant formation offering actionable guidance for the safe efficient operation of hydrogen-enriched natural gas in industrial boilers.

The rapid adoption of hydrogen fuel cell vehicles (HFCVs) in the Beijing–Tianjin–Hebei (BTH) hub accentuates the mismatch between renewable-based hydrogen supply in Hebei and concentrated demand in Beijing and Tianjin. We develop a mixed-integer linear model that co-configures a hydrogen pipeline network and optimizes hourly flow schedules to minimize annualized cost and CO2 emissions simultaneously. For 15000 HFCVs expected in 2025 (137 t d−1 demand) the Pareto-optimal design consists of 13 production plants 43 pipelines and 38 refueling stations delivering 50767 t yr−1 at 68% pipeline utilization. Hebei provides 88% of the hydrogen 70% of which is consumed in the two megacities. Hourly profiles reveal that 65% of electrolytic output coincides with local wind–solar peaks whereas refueling surges arise during morning and evening rush hours; the proposed schedule offsets the 4–6 h mismatch without additional storage. Transport distances are 40% < 50 km 35% 50–200 km and 25% > 200 km. Raising the green hydrogen share from 10% to 70% increases total system cost from USD 1.56 bn to USD 2.73 bn but cuts annual CO2 emissions from 142 kt to 51 kt demonstrating the trade-off between cost and decarbonization. The model quantifies the value of sub-day pipeline scheduling in resolving spatial–temporal imbalances for large-scale low-carbon hydrogen supply.

The thermal protection of rocket engine combustion chambers presents a critical challenge in supersonic flight applications. This study numerically investigates the enhancement of heat transfer and coolant flow characteristics in regenerative cooling channels through cylindrical rib integration employing ANSYS Fluent with SST k-ω turbulence modeling to evaluate single- and double-row configurations (0.75–1.25 mm diameter) under supercritical hydrogen conditions (3 MPa 300 K inlet). Results demonstrate that rib-induced turbulence disrupts thermal boundary layers with a 1.25 mm single-row design achieving a 13.67 % reduction in peak wall temperature compared to smooth channels while double-row arrangements show diminishing returns due to increased flow resistance. The thermal performance factor (η = (Nu/Nu₀)/(f/f₀) 1/3) reveals Case 3′s superiority (21.88 % improvement over the smooth channel configuration) in balancing heat transfer enhancement against pressure drop penalties (9.23–20.93 % for single-row 8.26–18.7 % for double-row). Notably density-driven flow acceleration near heated walls mitigates pressure losses through localized viscosity reduction. Furthermore cylindrical ribs reduce thermal stratification by up to 30 % in single-row configurations with double-row designs providing additional temperature homogenization at the cost of increased flow resistance. These findings offer critical insights for optimizing rib-enhanced cooling systems in high-performance rocket engines achieving simultaneous thermal efficiency and hydraulic performance improvements.

This work investigates a biomass-driven multi-generation system designed for simultaneous power freshwater and hydrogen production addressing the interlinked energy-waterenvironment nexus. The configuration integrates Brayton supercritical carbon dioxide (SCO2) organic Rankine cycle (ORC) and thermoelectric generator (TEG) subsystems to maximize utilization of biomass-derived syngas. The recovered energy drives a reverse osmosis (RO) desalination unit for freshwater production and an alkaline electrolyzer for hydrogen generation followed by two-stage compression for storage. Under baseline conditions the system generates 1.99 MW of electricity 9.38 kg/h of hydrogen and 88.6 m3 /h of freshwater with an overall exergetic efficiency of 20.25 % emissions intensity of 0.85 kg/kWh and a payback period of 5.87 years. The Brayton cycle accounts for 49.3 % of the total cost rate while the gasifier exhibits the highest exergy destruction at 46 %. Sensitivity analyses show that varying biomass moisture content (10–30 %) and operating temperatures (700–900 ◦C) significantly influence system performance. Using a data-driven optimization framework that combines artificial neural networks (ANN) and a genetic algorithm (GA) the system’s exergetic efficiency improves to 21.76 % freshwater output rises to 90.96 m3 /h and emissions intensity decreases to 0.877 kg/kWh. Additionally optimization reduces the total cost rate by 2.71 % leading to a payback period of 5.4 years and enhances the system’s overall performance by 12.64 %.

As a key zero-carbon energy carrier the accurate measurement of liquid hydrogen flow in its industrial chain is crucial. However the ultra-low temperature ultra-low density and other properties of liquid hydrogen can introduce calibration errors. To enhance the measurement accuracy and reliability of liquid hydrogen flow this study investigates the heat and mass transfer within a 1 m3 non-vented storage tank during the calibration process of a liquid hydrogen flow standard device that integrates combined dynamic and static gravimetric methods. The vertical tank configuration was selected to minimize the vapor–liquid interface area thereby suppressing boil-off gas generation and enhancing pressure stability which is critical for measurement accuracy. Building upon research on cryogenic flow standard devices as well as tank experiments and simulations this study employs computational fluid dynamics (CFD) with Fluent 2024 software to numerically simulate liquid hydrogen flow within a non-vented tank. The thermophysical properties of hydrogen crucial for the accuracy of the phase-change simulation were implemented using high-fidelity real-fluid data from the NIST Standard Reference Database as the ideal gas law is invalid under the cryogenic conditions studied. Specifically the Lee model was enhanced via User-Defined Functions (UDFs) to accurately simulate the key phasechange processes involving coupled flash evaporation and condensation during liquid hydrogen refueling. The simulation results demonstrated good agreement with NASA experimental data. This study systematically examined the effects of key parameters including inlet flow conditions and inlet liquid temperature on the flow characteristics of liquid hydrogen entering the tank and the subsequent heat and mass transfer behavior within the tank. The results indicated that an increase in mass flow rate elevates tank pressure and reduces filling time. Conversely a decrease in the inlet liquid hydrogen temperature significantly intensifies heat and mass transfer during the initial refueling stage. These findings provide important theoretical support for a deeper understanding of the complex physical mechanisms of liquid hydrogen flow calibration in non-vented tanks and for optimizing calibration accuracy.

The transport of natural gas blended with hydrogen is a key strategy for the low-carbon energy transition. However the influence mechanism of its thermo-physical property variations on centrifugal compressor performance remains insufficiently understood. This study systematically investigates the effects of the hydrogen blending ratio (HBR 0–30%) inlet temperature and rotational speed on key compressor parameters (pressure ratio polytropic efficiency and outlet temperature) through numerical simulations. In order to evaluate the influence of hydrogen blending on the performance and stability of centrifugal compressors a three-dimensional model of the compressor was established and the simulation conducted was verified with the experimental data. Results indicate that under constant inlet conditions both the pressure ratio and outlet temperature decrease with increasing HBR while polytropic efficiency remains relatively stable. Hydrogen blending significantly expands the surge margin shifting both surge and choke lines downward and consequently reducing the stable operating range by 27.11% when hydrogen content increases from 0% to 30%. This research provides theoretical foundations and practical guidance for optimizing hydrogen-blended natural gas centrifugal compressor design and operational control.

The accurate analysis of the sealing performance of underground lined cavern hydrogen storage is critical for enhancing the stability and economic viability of storage facilities. This study conducts an innovative investigation into hydrogen leakage behavior by developing a multiphysical coupled model for a composite system of support structures and surrounding rock in the operation process. By integrating Fick’s first law with the steady-state gas permeation equation the gas leakage rates of stainless steel and polymer sealing layers are quantified respectively. The Arrhenius equation is employed to characterize the effects of temperature on hydrogen permeability and the evolution of gas permeability. Thermalmechanical coupled effects across different materials within the storage system are further considered to accurately capture the hydrogen leakage process. The reliability of the established model is validated against analytical solutions and operational data from a real underground compressed air storage facility. The applicability of four materials— stainless steel epoxy resin (EP) ethylene–vinyl alcohol copolymer (EVOH) and polyimide (PI)—as sealing layers in underground hydrogen storage caverns is evaluated and the influences of four operational parameters (initial temperature initial pressure hydrogen injection temperature and injection–production rate) on sealing layer performance are also systematically investigated. The results indicate that all four materials satisfy the required sealing performance standards with stainless steel and EP demonstrating superior sealing performance. The initial temperature of the storage and the injection temperature of hydrogen significantly affect the circumferential stress in the sealing layer—a 10 K increase in initial temperature leads to an 11% rise in circumferential stress while a 10 K increase in injection temperature results in a 10% increase. In addition the initial storage pressure and the hydrogen injection rate exhibit a considerable influence on airtightness—a 1 MPa increase in initial pressure raises the leakage rate by 11% and a 20 kg/s increase in injection rate leads to a 12% increase in leakage. This study provides a theoretical foundation for sealing material selection and parameter optimization in practical engineering applications of underground lined caverns for hydrogen storage.