Increasing the operating temperature of proton exchange membrane fuel cells is an effective approach to enhance power density and simplify water and thermal management. However, conventional carbon paper gas diffusion layers are prone to water and thermal management failure under high temperature, low humidity, and dynamic loading conditions, which limits performance improvement. In this study, a titanium-based metal membrane gas diffusion layer denoted as Ti-GDL was systematically compared with a commercial Toray TGP-H-060 GDL. The electrochemical and mass transport characteristics were investigated through single cell polarization tests, electrochemical impedance spectroscopy, and 2D model simulations under conditions of 80–95 °C, 40 %–100 % RH, and dynamic loading. The results show that Ti-GDL maintains a stable polarization curve slope and a maximum current density retention exceeding 95 % in the temperature range of 80–95 °C, whereas TGP-H-060 GDL exhibits a degradation rate of 25.1 % at 95 °C. Electrochemical impedance spectroscopy demonstrates a 40 % rise in mass transport resistance for the Ti-GDL, only one-fifth the 200 % resistance increment observed with the TGP-H-060 GDL. Under dynamic loading, Ti-GDL experiences only brief voltage fluctuations of less than 5 s, while TGP-H-060 GDL suffers from multiple voltage undershoots and even cell voltage reverse. Simulations further demonstrate that the maximum liquid water saturation of Ti-GDL is 0.64, which is much lower than the nearly saturated state of TGP-H-060 GDL. Owing to the synergistic effects of its superhydrophobic surface, high thermal conductivity, and rigid porous structure, Ti-GDL exhibits excellent water and thermal management capabilities under extreme operating conditions.

[Objective]Hydrogen exhibits high flammability and low ignition energy,necessitating rigorous safety assessments for hydrogen-powered trains,particularly in platform environments where partial confinement and complex airflow conditions may promote hydrogen accumulation.However,experimental data characterizing hydrogen leakage and diffusion under realistic platform conditions remain extremely limited.This study experimentally investigates the leakage,dispersion,and accumulation behavior of hydrogen in a semiconfined train platform environment,with an emphasis on identifying potential safety risks associated with localized hydrogen enrichment.The results are intended to support platform design optimization,sensor deployment strategies,and quantitative risk assessment for hydrogen-powered rail systems.[Methods]A 1:5 scale experimental platform was constructed to replicate a typical railway platform and hydrogen-powered train configuration,incorporating a domed roof structure and partially open boundaries to simulate a semiconfined ventilation environment.High-purity hydrogen(99.999%)was released at controlled leakage rates of 2,5,and 45 SLPM,representing a range of credible failure scenarios,including minor seal degradation,valve malfunction,and severe pipeline rupture.Hydrogen concentration sensors were strategically installed at the pantograph-contact wire interface,along the platform ceiling,and within the hydrogen storage compartment to capture spatial and temporal variations in hydrogen concentration.Data were acquired in real time using a LabVIEW-based monitoring system.The experimental setup consisted of a steel support framework,a scaled train model designed to preserve hydrodynamic similarity,and a high-precision leakage control system integrating high-pressure gas cylinders,valves,and mass flow controllers.Potential leakage locations were identified through a combination of finite-element stress analysis and fault-tree analysis to ensure realistic failure representation.[Results]The experimental results demonstrate that,under most tested conditions,hydrogen concentrations at the platform ceiling and the pantograph-contact wire interface remain well below the lower flammability limit.Peak concentrations are limited to 0.22%at 2 SLPM,0.17%at 5 SLPM,and 2.8%at 45 SLPM,indicating strong dilution capability and a substantial safety margin in the open platform region.In contrast,significant hydrogen accumulation is observed within the hydrogen storage compartment under the high leakage rate of 45 SLPM.In this confined space,the average hydrogen concentration reaches 6.96%,with a peak of approximately 11%at the sensor directly above the leakage point.This maximum value exceeds the flammability threshold,posing a potential ignition hazard.The results reveal strong coupling among structural confinement,natural ventilation,leakage rate,and leakage location.Turbulent mixing and ambient airflow play a dominant role in redistributing hydrogen clouds,often preventing stable accumulation directly above leakage points in open regions.However,restricted ventilation within the storage compartment substantially aggravates hydrogen retention,particularly under high-flow leakage conditions.[Conclusions]This study establishes a realistic experimental framework for investigating hydrogen leakage and diffusion behavior in a semiconfined train platform environment and provides valuable experimental data for hydrogen safety evaluation.The findings indicate that hydrogen-powered trains generally maintain a high safety margin in typical platform areas.However,localized high-concentration zones may develop within poorly ventilated storage compartments during severe leakage events,necessitating targeted mitigation measures.These results highlight the critical importance of ventilation design,optimized sensor placement,and rapid emergency response strategies in reducing hydrogen-related risks.Future work will integrate computational fluid dynamics simulations to extend the parametric space and conduct full-scale train experiments to further validate the observed phenomena.Overall,this study offers practical guidance for developing safety standards and engineering controls for hydrogen-powered rail systems,supporting the safe deployment of hydrogen energy in rail transportation and contributing to global decarbonization efforts.

Proton exchange membrane fuel cells (PEMFCs) are regarded as a key technology for sustainable energy conversion due to their high efficiency and low emissions. The gas diffusion layer (GDL), serving as a multifunctional component responsible for reactant transport, water management, electrical conduction, and mechanical support, plays a critical role in determining PEMFC performance and durability. Despite extensive studies on electrochemical degradation, the mechanical durability of GDLs under cyclic assembly stresses remains insufficiently understood, particularly regarding their microstructural evolution and multi-physical property coupling. In this study, a controlled multi-cycle stress loading protocol was proposed to systematically investigate the elastic-plastic deformation behavior, microstructural evolution, and electrochemical performance degradation of GDLs under different assembly torques (8-20 Nm). A solid mechanics simulation model was established based on Young's modulus derived from piecewise fitting of experimental stress-strain curves. The model quantified strain-induced variations in porosity, permeability, diffusivity, and electrical conductivity. Five stress cycles were conducted, and PEMFC performance was evaluated using polarization curves and electrochemical impedance spectroscopy (EIS), complemented by optical microscopy observations before and after cycling. Results indicate that compressive strain reduces GDL porosity, permeability, and diffusivity, while slightly enhancing electrical conductivity. The first stress cycle exhibited the highest performance, followed by gradual degradation. Lower torque (8 Nm) resulted in greater performance dispersion, whereas higher torque (20 Nm) provided better structural stability but increased mass transport resistance, which dominated overall performance decay. After 3 cycles, the GDL structure tended toward stabilization, slowing further degradation. Multi-scale structural damage, including carbon fiber deformation and pore connectivity loss, was identified as a key factor in performance deterioration. This work provides mechanistic insight into the durability of GDLs under cyclic mechanical stress and offers theoretical and experimental guidance for optimizing assembly strategies to enhance the long-term reliability of PEMFC systems.

Hydrogen fuel-cell trains offer a low-carbon alternative for rail but pose safety risks from leaks in enclosed stations. Leaked hydrogen, being lighter than air, accumulates near ceilings, creating combustible clouds. This study uses a Computational Fluid Dynamics (CFD) model to analyze hydrogen dispersion within a platform. By varying parameters such as leakage rate, ceiling dimensions, and platform length, the research quantitatively investigates hydrogen concentration and accumulation behaviors to assess safety hazards in railway infrastructure. Results indicate that higher leakage rates and lower ceilings exacerbate hydrogen accumulation, whereas increasing ceiling height and optimizing roof dimensions (shorter length, wider width) mitigate risks. Notably, implementing a roof ventilation opening proved the most effective strategy, outperforming geometric adjustments by reducing peak concentration by 38.7% and flammable cloud width by 40.8%. These findings emphasize the importance of structural parameters, providing a quantitative basis for optimizing design and safety measures in hydrogen-powered railway infrastructure.

Reliable auxiliary heating-free self-startup under low-temperature conditions is crucial for enhancing the environmental adaptability, reducing costs, and expanding the commercial application prospects of fuel cells. However, current research primarily focuses on single-cell levels, while studies on commercial high-power stacks, particularly regarding the influence of startup current loading strategies on the failure mechanisms of end-plate cells, remain insufficient. To address this, this study conducted multiple cold-start experiments under various ambient temperatures and combined them with one-dimensional model simulations to systematically analyze the effects of loading strategies on coolant temperature, stack voltage uniformity, and the performance of end-plate cells. Experimental and simulation results reveal that cold-start failure is primarily caused by the sudden voltage drop of end-plate cells due to the "end-plate effect" and ice blockage in the later stage. The study demonstrates that, compared to the step loading strategy, the linear loading strategy better balances the competition between heat generation and ice formation during startup, allowing system heat generation to gradually dominate. This assists end-plate cells in achieving temperature breakthrough and completing the startup process. Experimental results show that the linear loading strategy significantly improves startup performance, reducing startup time by 7 s and 2 s at -15 degrees C and - 20 degrees C, respectively, and successfully extending the auxiliary heating-free startup limit to -30 degrees C. Furthermore, this strategy effectively enhances stack voltage uniformity, with the voltage non-uniformity coefficient reduced by up to approximately 80.67%. This study provides an effective control method to enhance the all-climate operational capability of PEMFCs.

This study investigated variations in hydrogen concentration, high-frequency impedance, stack voltage, and typical monolithic voltage under different operating conditions based on the ultrasonic online monitoring device. The effects of hydrogen concentration and inlet stoichiometric ratio on performance heterogeneity were quantitatively analyzed. Additionally, the stack performance under different anode circulation modes was examined. The results indicated that elevated temperature promoted membrane dehydration and shrinkage, reducing the water phase volume and narrowing the transport channels, leading to a decrease in nitrogen crossover. Under dry membrane conditions, the stack becomes more sensitive to hydrogen concentration fluctuations, resulting in reduced output voltage stability. The monolithic voltage was attenuated slowly when hydrogen concentration fell below 60 %, with a significant sawtooth-type decay when concentration dropped below 45 %. The lowest monolithic voltage consistently occurred in cells near the inlet, where higher gas flow rates resulted in less diffusion of hydrogen. In the current density range of 0.1-0.3 A cm-2, the ejector experienced secondary flow back, while optimal performance was achieved at 0.9 A cm-2, with circulation rate of 52.3 %. System efficiency in parallel mode consistently exceeded that of single blower mode, with a maximum efficiency improvement of 1.02 % at a current density of 1.4 A cm-2.

The water redistribution state after shutdown in proton exchange membrane fuel cells is crucial to subsequent cold starts, operational performance, and long-term durability. However, the redistribution mechanism of ionomer-dissolved water content remains lacking systematic experimental and theoretical validation. This study investigates post-shutdown water redistribution through an integrated approach of experiments and numerical simulations. The experimental work involves shutdown tests coupled with high-frequency resistance (HFR) measurements to dynamically track changes in water content, while the simulations employ a two-dimensional multiphase transport model that incorporates liquid water, water vapor, and ionomer-dissolved water transport processes. Experimental results demonstrate a four-stage evolution pattern of HFR after shutdown, along with a notable reduction in HFR after water redistribution. Simulation results reveal that the underlying mechanism lies in the dynamic evolution between the actual ionomer-dissolved water content and its equilibrium value induced by temperature variations: specifically, temperature decrease intensifies water redistribution, while extended standstill time facilitates the achievement of water equilibrium. This study clarifies the core mechanism of post-shutdown water redistribution in PEMFCs, thereby providing reliable theoretical and technical support for optimizing shutdown strategies and enhancing fuel cell durability.

Light-duty vehicles (LDV) are scaling up electrification technologies from battery to dedicated hybrid engines (DHEs). The success from electrification of LDVs can be a starting point to look into a similar trending development of commercial vehicles (CV), which are bigger and heavier with more demanding work cycles. "Greenhouse Gas Emissions Standards for Heavy-Duty Vehicles (HDV)- Phase 3" establishes new CO2 emission standards for MY 2032 (Model Year) and later HD vehicles with more stringent CO2 standards phasing in as early as MY 2027 for certain vehicle categories. In this article, the focus is about improving the operational efficiency of MDHD (medium-duty and heavy-duty) vehicles through a selected electrification technology in this study rather than pure BET (battery electric truck). Extended-range electric vehicle (EREVs) systems are studied here to address sustainability regarding charging infrastructure and by using the renewable fuels (hydrogen, ammonia, methanol, and ethanol). Range-extender systems with using renewable fuels are investigated to electrify CV for cost-effectiveness and carbon reduction as well as tailpipe emissions in the USA. The numeric analysis expanded from the experimental BET study shows the promising potential of EREVs for electrifying HDVs through applying renewable fuels.

Proton exchange membrane fuel cells (PEMFCs) are pivotal for the efficient utilization of renewable hydrogen to decarbonize the transportation sector, yet durability under dynamic conditions remains a primary barrier. To address the lack of quantitative distinction between degradation modes under coupled stresses, this work establishes a temperature-dependent framework to separate reversible voltage losses from irreversible performance decay during Fuel Cell Dynamic Load Cycles (FC-DLC). Accelerated durability tests were conducted at 71 degrees C and 85 degrees C. Results demonstrate that elevated temperatures significantly exacerbate irreversible degradation. After 300 F C-DLCs, the voltage degradation rate relative to the initial voltage at 100% load (approximate to 1.28 A/cm(2)) reached 4.72% at 85 degrees C, compared to 2.78% at 71 degrees C. The electrochemical active surface area retention drops to 48.40% at 85 degrees C, compared to 71.21% at 71 degrees C.While operation at 85 degrees C initially enhances reversible voltage recovery (approximate to 0.015 V) due to improved water redistribution, this benefit diminishes as irreversible damage accumulates, with the relative recovery degree dropping below 20% after 300 cycles. Crucially, a novel mechanistic link is established between temperature-enhanced dynamic voltage undershoot and accelerated lifetime degradation, highlighting a strong correlation between transient voltage undershoot and cumulative irreversible damage. Based on these findings, specific actionable strategies are proposed for durability enhancement. Operating temperatures under dynamic loads should be strictly limited to mitigate accelerated ECSA loss; shutdown recovery procedures involving condensation should be scheduled frequently, specifically before 150 cycles, to maximize recovery efficiency before cumulative irreversible degradation becomes dominant. The findings provide specific strategies to enhance the reliability of renewable energy propulsion systems.

Overheating hazard of nonuniformly degraded battery systems limits battery All-lifespan safe applications. However, the evolution principle and corresponding strategies are still unlocked. Therefore, this study proposes a dynamic immersion cooling strategy to address the All-lifespan 4C fast charging issue of nonuniformly degraded modules. Firstly, heat generation of degraded batteries are experimentally measured to be more significant due to severe side reactions under fast charging, inducing nonuniform heat accumulation-degradation in systems. Moreover, maximum temperature (Tmax: 437.5 K) and temperature standard deviation (TSD: 5.5 K) are detected in the harshest nonuniformly degraded module after 4C fast charging for 15 min, which can be controlled within an acceptable level (Tmax: 316.85 K, TSD: 2.3 K) under the coolant flow rate threshold 0.005 kg/s with the cooling scheme. Furthermore, dynamic coolant flow rate threshold is investigated for different nonuniformly degraded modules, cooling strategies are evaluated form the temperature control (decrement and uniformity) and energy cost, coolant threshold q1 is selected with higher thermal and economically efficiency. This study provides guidance for All-lifespan thermal management in the next-generation energy storage devices, considering the nonuniformly degradation effect.

This study evaluates sealing materials for PEMFCs, focusing on silicone rubber (VQM), fluororubber (FKM), and ethylene propylene diene monomer (EPDM). Optimized through filler addition and plasticization, modified EPDM offers balanced hardness, with deformation resistance between VQM and FKM. Modifications enhance its deformation resistance while maintaining good tensile strength and superior fixed extension stress. The modified EPDM excels in both low (-40 degrees C) and high-temperature (100 degrees C) tests, as well as acid resistance trials, highlighting its promising application in fuel cell bipolar plate sealing.

The gas diffusion layer (GDL) is a critical component determining the performance and durability of Proton Exchange Membrane Fuel Cells (PEMFCs). This study systematically investigates the compatibility between a sintered titanium-based GDL and traditional bipolar plates, integrating experimental characterization, sensitivity analysis, and performance evaluation. Titanium-based GDLs were fabricated via powder metallurgy using -325 + 500 mesh titanium powder, followed by hydrophobic treatment and microporous layer modification. Comprehensive characterization reveals that the titanium-based GDL exhibits a low interfacial contact resistance of 2.0065 m Omega cm(2) and superior hydrophobicity. Crucially, stress cycling tests demonstrate its exceptional mechanical stability, maintaining consistent electrochemical performance over 20 stress cycles, whereas the commercial TGP-H-060 carbon-based GDL exhibited significant degradation after only 5 cycles. Polarization curve analysis indicates that while the titanium-based GDL shows slightly higher mass transport losses at low flow rates, it demonstrates superior voltage stability under high-temperature (80 degrees C) and high-humidity (100% RH) conditions, effectively mitigating water flooding and membrane dehydration. Multi-factor orthogonal tests (L-49(7(8))) identify the stoichiometric ratio as the dominant factor affecting performance (80.01% contribution), with temperature and humidity having minimal impact, further confirming the material's environmental robustness. Finally, a Bayesian optimized Gaussian Process Regression model (RMSE = 1.5762 A) was established to predict performance across 206,336 operating conditions, revealing that a stoichiometric ratio >2.0 and inlet pressure >1.8 bar are critical for optimal operation. This study provides theoretical and experimental support for the engineering application of titanium-based GDLs as a durable alternative for PEMFCs.

To improve waste heat utilization and clarify the electricity–thermal–hydrogen coupling mechanism in integrated backup power systems, a 60 kW proton exchange membrane fuel cell (PEMFC)–solid-state hydrogen storage system (SSHSS) is developed. An electricity–thermal–hydrogen coordinated operation architecture and a coordinated energy management strategy are proposed and experimentally validated under startup, rated-load, peak-load, and reduced-pressure conditions. Furthermore, a comprehensive electricity–thermal–hydrogen evaluation framework is established to characterize multi-energy-flow coordination. The results demonstrate that the proposed strategy enables stable coordinated operation of the PEMFC, SSHSS, energy storage system, and thermal management system under all operating conditions. The system operates continuously for 120 min at 60 kW and 10 min at 90 kW, while maintaining stable operation under reduced-pressure conditions. The overall energy utilization ratio (EUR) remains above 50%, the hydrogen supply pressure stability index (HSPS) fluctuates by less than 10%, and the theoretical waste heat recovery ratio ( ) increases from approximately 20% during startup to 30% under steady operation. The results reveal that the integrated system exhibits demand-driven, waste heat-mediated, and multi-dimensional synergistic characteristics, with stable operation governed by the dynamic coordination of electrical, thermal, and hydrogen energy flows. The proposed framework provides a unified basis for the evaluation, operation, and design of PEMFC–SSHSS integrated backup power systems.

Helium surrogate testing reduces the risks associated with hydrogen leak-dispersion experiments. A single fixed conversion coefficient, however, preserves only one physical quantity and cannot simultaneously represent open jets, jets with different orientations, and confined releases. We compared open-space horizontal jets, vertically upward jets, and a semi-confined enclosure. Eight conditions spanned nozzle diameters of 1–3 mm and flow rates of 20–100 SLPM. Four conversion criteria were evaluated using the similarity ratio R, local concentration deviation, and the overall deviation index D total . Greater exit momentum delayed far-field similarity loss in horizontal jets; upward orientation reduced buoyancy-driven transverse separation; confinement stabilized the hydrogen-to-helium concentration relation; and a larger nozzle increased sensitivity to the conversion criterion. These differences reflect scenario-dependent competition between inertia and buoyancy. For horizontal jets, D total was 0.185–0.190 at 1 mm–20 SLPM and decreased to 0.156–0.160 at 50 SLPM. At 20 SLPM, a 2 mm nozzle widened this range to 0.150–0.209. In the enclosure, the concentration ratio was approximately 1.45, less than 3% from the standard conversion relation. A scenario-dependent framework based on exit momentum flux and Froude number supports the selection and assessment of helium test conditions.

In high-power proton exchange membrane fuel cell (PEMFC) systems, insufficient hydrogen supply at the anode can induce hydrogen starvation, resulting in voltage non-uniformity, accelerated degradation, and reduced durability. However, the coupled effects of hydrogen concentration variation, nitrogen permeation, and hydrogen recirculation remain insufficiently understood at the stack level. This study experimentally investigates the output characteristics and voltage consistency of a high-power multi-cell PEMFC stack under varying hydrogen concentrations, current densities, and recirculation flow rates. By integrating electrochemical kinetics with thermodynamic analysis, the voltage decay mechanism induced by hydrogen dilution is quantitatively clarified. Results show that nitrogen permeation significantly reduces the anode hydrogen partial pressure and increases high-frequency resistance (HFR). As hydrogen concentration decreases, voltage consistency exhibits a two-stage deterioration behavior, with rapid degradation occurring below a critical concentration threshold that depends on recirculation intensity. Increasing the recirculation speed from 2500 rpm to 4500 rpm shifts the local starvation threshold from ~45% to ~17%. At 1.0 A cm−2, the hydrogen concentration difference between the anode inlet and outlet increases from 8.6% to 47%, indicating severe axial non-uniformity. Voltage loss analysis shows that reducing hydrogen concentration from 90% to 40% results in a total loss of ~46 mV, dominated by anode activation loss (54%) and thermodynamic loss (27%), while ohmic loss contributes 13%. These findings provide quantitative guidance for optimizing hydrogen supply strategies in high-power PEMFC systems.

At present, main fuel cell systems use anode hydrogen recirculation to improve hydrogen utilization. This process inevitably emits a portion of unreacted hydrogen, which can accumulate locally in confined space and exceeds the flammability limit, resulting in safety hazards. However, the influence of hydrogen release parameters and environmental conditions on the hydrogen diffusion pattern has not been fully elucidated and requires further investigation. Thus, in this work, a steady-state hydrogen release and diffusion model is established to investigating the safety boundary of hydrogen purging of the PEMFC system on vehicles in confined space. Then, the diffusion path and concentration distribution of hydrogen under different release and environmental conditions are studied, and the experimental validation is also carried out. The results show that the initial mass flow rate and concentration of the release gas have a great influence on the diffusion pattern and concentration distribution of hydrogen, and the external temperature has little influence on it, while the ventilation device and the size of the confined space have a great influence on the average hydrogen concentration in the whole area. Moreover, the results of this work can provide technical support for the control of hydrogen system of fuel cell system, which is of great significance for improving the safety of fuel cell vehicles.

Cold start remains a critical bottleneck for the commercialization of proton exchange membrane fuel cells (PEMFCs), primarily due to voltage inconsistency and ice blockage exacerbated by the endplate effect. This study proposes a voltage consistency-guided optimization methodology for cold start loading strategies. A one-dimensional multi-phase model that incorporates endplate thermal effects and cell-to-cell parameter variations is validated against a 5 kW stack experiment. The model identifies minimum startup current density thresholds at various subzero temperatures and reveals a four-stage evolution of the voltage coefficient of variation (Cv): slow rise, accelerated rise, sharp rise, and drop/shutdown. Quantitative Cv benchmarks are established: a maximum Cv ≤ 0.3 reflects near-ideal voltage uniformity, whereas a maximum Cv > 5 signals severe ice blockage and imminent voltage collapse in endplate cells. Guided by Cv suppression, linear, stepwise, and exponential loading strategies are compared. The 15 s linear loading strategy proves optimal, consistently maintaining the maximum Cv within the favorable range and achieving an effective balance between temperature rise rate and voltage consistency; strategies that push the maximum Cv above 5 (e.g., 35 s linear loading) invariably cause endplate cell failure. Experimental verification at −5 °C, −10 °C, and −15 °C demonstrates successful cold starts within 19.1 s, 36.6 s, and 53.4 s, respectively, with strong voltage uniformity and high temperature rise efficiency. This work establishes the core principle of balancing startup rate and consistency, providing a simulation–experiment route and engineering guidance for reliable PEMFC cold start across a wide low-temperature range.

Proton exchange membrane fuel cells are a promising sustainable energy technology, and the gas diffusion layer is a key component affecting the performance. This study focused on the preparation and performance optimization of titanium-based metal gas diffusion layers for proton exchange membrane fuel cells. Four titanium powder sizes were screened, with the − 325 + 500 mesh powder selected due to its balanced apparent density of 1.58 g cm−3 and flowability of 45 s. The most favorable sintering condition identified in this study for this powder was determined as 1050 °C for 1.5 h, yielding a titanium-based metal gas diffusion layer with a tensile strength of 7.67 MPa, average pore size of 35.06 μm, and permeability of 2.94 × 10–12 m2, comparable to commercial TGP-H-060 carbon paper but with better structural stability. A 0.15 mm titanium-based gas diffusion layer exhibited superior gas permeability, with a Gurley time of 0.65 s and 74.6

Public concerns regarding potential hydrogen leakage from hydrogen-powered trains, particularly during emergency cylinder releases inside tunnels, constitute a major impediment to their deployment. This study proposes an experimental method for reproducing hydrogen release in railway tunnels, which includes the low-cost construction of a full-scale tunnel and the design of a hydrogen system that replicates the discharge characteristics of a TPRD. Experimental measurements revealed that the sensor directly above the discharge outlet registered a peak volume fraction of 10.9%, which subsequently dissipated below 4% across all sensors within 273 s. A numerical model, validated by the experimental data, was established to elucidate the evolution of hydrogen clouds and perform safety assessments. The asymmetric structure of hydrogen clouds under the influence of ambient wind was identified. This study quantitatively analyzed the volume of hydrogen clouds and the area of hazardous zones at the tunnel ceiling under key concentration ranges. Notably, the hazardous cloud volume diminishes via the coupling effect of continuous fresh air entrainment and the exponential decay of the source release rate. Furthermore, the dilution effect of ambient wind on hydrogen dispersion and the ventilation strategies were also discussed. The integration of full-scale testing and validated numerical modeling yields a robust framework for assessing the risk of hydrogen release in underground transportation infrastructures.

In emergency scenarios such as onboard fires, hydrogen fuel cell (HFC) trains may rapidly vent large quantities of hydrogen from high-pressure storage tanks, posing potential risks to passengers and surrounding infrastructure. However, existing studies mainly address secondary accidents after jet ignition, while hydrogen diffusion and transient venting flow behavior, particularly in rail-specific environments, remain insufficiently understood. This study conducted full-scale 35 MPa and 70 MPa venting experiments on HFC train storage systems to investigate gas dispersion, thermal responses, and flow dynamics. Results show pronounced anisotropic dispersion; vertical jet inertia drives peak hydrogen concentrations to 13%-23% at the simulated overhead contact line. Concurrently, adiabatic expansion causes rapid, sustained subzero cooling in key components, intensifying at higher pressures. Schlieren imaging captures the jet's transition from an under-expanded supersonic state to a turbulent plume. These mechanistic findings yield targeted safety measures, providing actionable guidelines for safety zoning, vent design, and model validation.