Hydrogen Content Research Articles

Nagynyomású hidrogénatmoszférás kemence gyártása szénacélok elridegedésének vizsgálatához

Összefoglalás. A hidrogén tárolása iránti igény egyre növekszik, melynek oka az, hogy a hidrogén mint alternatív energiahordozó jelentős szerepet játszik a szén-dioxidkibocsátás-csökkentési törekvésekben. Azonban, az elridegedési folyamatok körében a hidrogén által előidézett károsodások jelentik a legkomolyabb problémát az acélokra nézve. Kutatómunkánk során egy nagynyomású hidrogénatmoszférás hőkezelésre alkalmas autoklávot terveztünk, majd gyártottunk. Az autoklávban P355 NH minőségű alapanyagból kimunkált szabványos Charpy-féle ütőpróbatesteket hőkezeltünk 150 °C-on, 40 bar túlnyomáson, 200 órán keresztül, tiszta hidrogén atmoszférában. A vizsgálatok eredményei alapján megállapítottuk, hogy a jelentős mértékű elridegedés a hidrogénezési folyamat után sem történt. Summary. The demand for hydrogen storage is growing. The primary reason for this is that hydrogen as an alternative energy carrier is playing a significant role in carbon reduction efforts as a fuel for road and maritime transport. In addition, hydrogen can be seen as a long-term flexible energy storage option. Hydrogen as an energy carrier is expected to play a significant role in residential and industrial use in the future. A first step in this development is the mixing of hydrogen with natural gas in small quantities. Increasing the share of hydrogen would not only reduce CO2 emissions, but would also facilitate the development of different hydrogen production methods and thus reduce production costs. The upper safety limit for hydrogen blending with natural gas is set by the national specification of the natural gas supply, possible material quality restrictions and the tolerance of the most sensitive equipment in the network. For this reason, the maximum allowable hydrogen content in natural gas is generally limited to 2,5%. However, among the embrittlement processes, hydrogen-induced damage is the most serious problem for both non-alloy and low-alloy steels. Atomic hydrogen diffuses in steel at high rates. The diffusion rate is orders of magnitude higher than that of other elements; this is due to the small atomic diameter of hydrogen. To investigate the degradation of different carbon steels in a high-pressure hydrogen atmosphere, a hydrogenation furnace was designed and fabricated at the Department of Materials Science and Engineering at BME. The hydrogenation furnace is the main part of a complex mechanical engineering system, for the operation of which the mechanical, heating, electrical supply, control and gas handling components are indispensable. The entire design process of the furnace was led by József Blücher, Professor Emeritus at BME, with the help of the engineers and technicians working on the project. Standard Charpy impact test specimens were machined from P355 NH grade material to test the embrittlement of carbon steels. The hydrogenation temperature was 150 °C, the internal overpressure in the chamber was 40 bar, the hydrogenation time was 200 hours and the atmosphere was hydrogen gas of purity 5.0. The impact test was carried out at -20, 0 and +20 °C. Based on the results of the tests, it can be concluded that there was no significant degree of degradation both before hydrogenation and after prolonged exposure to hydrogen. It can be concluded that the tube material used as a sample is suitable for operation in a hydrogen medium. Based on the analysis of the burst areas and impact values of the impact test specimens, it was concluded that hydrogen did not cause any observable damage to the test material.

Effect of elevated temperatures (550–860 K) on the laminar flame speeds of methane/hydrogen blends

Experimental determination of laminar flame speeds was performed for methane/hydrogen mixtures in a 79% Ar/21% O2 oxidizer (referred to as “airgon”) at 1 atm. The shock-tube flame speed method enabled the first measurements at temperatures above 650 K and was employed to study binary fuel blends with various hydrogen fuel fractions (xH2 = 0.1–0.4) at equivalence ratios of 0.8, 1.0, and 1.2 in the unburned-gas temperature range of 550–860 K. Results were compared against simulations conducted using the GRI-3.0, FFCM-2 and Stagni et al. models. Good agreement between all three models and measurements was observed at lean and stoichiometric conditions, while the three models and data diverge in the rich case. Equivalent fuel/air flame speeds were computed from fuel/airgon measurements by applying a mixture-dependent scaling ratio. The scaled air equivalent data were compared against literature data and showed good agreement. Through sensitivity analyses, it was found that reactions related to neat methane combustion are highly relevant at all conditions, while H2-specific reactions only become important with high hydrogen content (xH2 ≥ 0.4). Additionally, differences in sensitivity coefficients were identified across the models, providing useful information for potential refinement of reaction rates, and consequently, the development of models which better represent new experimental data.

Study on high-pressure hydrogen leakage characteristics under different shapes of nozzles

In this paper, numerical simulations and experimental methods are utilized to investigate the near-field jet structures and far-field concentration distributions after the release of circular, equilateral triangular, square, and rectangular (AR2, AR4, AR8) nozzles. For all nozzle shapes, the hydrogen concentration along the jet centerline is inversely proportional to the distance from the nozzle. Circular nozzles exhibit the slowest decay of hydrogen concentration along the jet centerline, while rectangular nozzles show the fastest decay. Under the studied pressures, the concentration distributions along the jet centerline after the release of all nozzles are summarized into an equation. For the near-field jet structure, all nozzle except the circular nozzle experience varying degrees of deflection. When the aspect ratio is greater than or equal to 4, the Mach disk cannot be formed. An empirical formula for the position of the shock waves of the rectangular nozzle jet is proposed.

Evaluation of the Technical Condition of Pipes during the Transportation of Hydrogen Mixtures According to the Energy Approach

In this study, a theoretical–experimental methodology for determining the stress–strain state in pipeline systems, taking into account the hydrogen environment, was developed. A complex of theoretical and experimental studies was conducted to determine the specific energy of destruction as an invariant characteristic of the material’s resistance to strain at different hydrogen concentrations. The technique is based on the construction of complete diagrams of the destruction of the material based on the determination of true strains and stresses in the local volume using the method involving the optical–digital correlation of speckle images. A complex of research was carried out, and true diagrams of material destruction were constructed, depending on the previous elastic–plastic strain and the action of the hydrogen environment. The change in the concentration of hydrogen absorbed by the material was estimated, depending on the value of the specific energy of destruction. A study was conducted on tubular samples, and the degree of damage to the material of the inner wall under the action of hydrogen and stress from the internal pressure was evaluated according to the change in specific energy, depending on the value of the true strain established with the help of an optical–digital correlator on the outer surface, and the degree of damage was determined. It has been established that the specific fracture energy of 17G1S steel decreases by 70–90% under the influence of hydrogen. The effect of the change in the amount of strain energy on the thickness of the pipe wall is illustrated.

ZIF‐8 decorated FeMo nanoparticles: H2 Production from the catalytic hydrolysis of ammonia‐borane

AbstractAmmonia‐Borane (AB) is considered a promising solid hydrogen storage material due to its high hydrogen content (19.6 wt%) and its use for safe hydrogen transport. The most effective way to produce H2 from AB is to perform the hydrolysis reaction in the presence of a suitable catalyst. In this study, Fe0.2Mo0.8/ZIF‐8 nanocatalyst was synthesized in two steps: (i) synthesis by following the colloidal synthesis technique by thermal decomposition of Mo(CO)6 and Fe(acac)3 in the presence of OM and ODE at high temperatures, and (ii) the resulting colloidal Fe0.2Mo0.8 NPs were decorated into ZIF‐8. The as‐prepared Fe0.2Mo0.8/ZIF‐8 catalyst was identified using advanced characterization techniques such as ICP‐OES, P‐XRD, SEM, SEM–EDX, TEM, TEM‐EDX, XPS, and BET. The catalytic activities of the Fe0.2Mo0.8/ZIF‐8 catalyst in the hydrolysis of AB were investigated in different parameters (temperature, catalyst [Fe0.2Mo0.8] and substrate [H3NBH3] concentration, and recyclability). The results show that high crystallinity Fe0.2Mo0.8 NPs with a uniform 1.31 ± 0.13 nm distribution were formed on the ZIF‐8 surface. Fe0.2Mo0.8/ZIF‐8 catalyst provides a maximum H2 generation rate of 184.2 mLH2 (g catalyst)−1 (min)−1 at 343 K. This uniquely cost‐effective, active and durable Fe0.2Mo0.8/ZIF‐8 catalyst has strong potential for H2‐based fuel cell (PEM: Proton Exchange Membrane) applications where AB is a suitable H2 carrier.Highlights FeMo NPs were synthesized by a colloidal synthesis method and decorated into ZIF‐8. FeMo/ZIF‐8 catalyst is an active catalyst in the hydrolysis of AB. FeMo/ZIF‐8 catalyst showed an initial TOF value of 449.85 mol(H2)·molFe0.2Mo0.8−1·h−1 in the AB hydrolysis at 338 K.

Production and New Green Activation of Conductive 3D-Printed Cu/PLA Electrode: Its Performance in Hydrogen Evolution Reactions in Alkaline Media

In this study, Cu-polylactic acid (PLA) composite filaments were produced with an extruder and three-dimensional (3D) Cu/PLA electrodes were 3D printed with Fused Deposition Modelling (FDM) method. To improve the electrochemical performance of the 3D-Cu/PLA electrode, a novel electrochemical activation method, which differentiates from complex activation methods in the literature, was applied in 1 M KOH solution without using any solvent. Field emission scanning electron microscopy (FE-SEM), Energy-Dispersive X-ray Spectroscopy (EDX), Fourier Transform Infrared Spectroscopy (FT-IR), and RAMAN techniques were used to characterize the 3D-Cu/PLA electrode before and after activation. The results showed that Cu particles were released after the degradation of PLA after activation. In addition, the thermal stability of the 3D electrode was demonstrated by the TGA technique. The performance of the 3D Cu/PLA electrode before and after activation in the hydrogen evolution reaction (HER) in 1M solution was measured using cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and cathodic polarization curves methods. The EIS results showed that the charge transfers resistance values of the 3D-Cu/PLA electrode in 1 M KOH decreased significantly after activation. Post-activation hydrogen content measurements of the 3D-Cu/PLA electrode after electrolysis at different potentials and energy efficiency tests at different current densities were also carried out. The results indicate that the electrocatalytic properties of 3D-Cu electrodes were improved for HER through the activation process.

Hydrothermal liquefaction of composite household waste to biocrude: the effect of liquefaction solvents on product yield and quality.

The hydrothermal liquefaction (HTL) of composite household waste (CHW) was investigated at different temperatures in the range of 240-360 °C, residence times in the range of 30-90 min, and co-solvent ratios of 2-8 ml/g, by utilising ethanol, glycerol, and produced aqueous phase as liquefaction solvents. Maximum biocrude yield of 46.19% was obtained at 340 °C and 75 min, with aqueous phase recirculation ratio (RR) of 5 ml/g. The chemical solvents such as glycerol and ethanol yielded a biocrude percentage of 45.18% and 42.16% at a ratio of 6 ml/g and 8 ml/g, respectively, for 340 °C and 75 min. The usage of co-solvents as hydrothermal medium increased the biocrude yield by 35.30% and decreased the formation of solid residue and gaseous products by 19.82% and 18.74% respectively. Also, the solid residue and biocrude obtained from co-solvent HTL possessed higher carbon and hydrogen content, thus having a H/C ratio and HHV that is 1.01 and 1.23 times higher than that of water as hydrothermal medium. Among the co-solvents, HTL with aqueous phase recirculation resulted in higher carbon and energy recovery percentages of 9.36% and 9.78% for solid residue and 52.09% and 56.75% for biocrude respectively. Further qualitatively, co-solvent HTL in the presence of obtained aqueous phase yielded 33.43% higher fraction of hydrocarbons than the pure water HTL and 7.70-17.01% higher hydrocarbons when compared with ethanol and glycerol HTL respectively. Nitrogen containing compounds, such as phenols and furfurals, for biocrudes obtained from all HTL processes, were found to be present in the range of 8.30-14.40%.

Modeling hydrogen diffusion in precipitation hardened nickel-based alloy 718 by microstructural modeling

Abstract Environmentally assisted cracking can significantly affect the performance of high strength alloys and limit material selection to minimize the risk of subcritical crack growth in service. UNS N07718 is widely used in marine service applications and under a variety of conditions, such as: alternate immersion, different levels of cathodic protection, and freely corroding galvanic couples, because of its demonstrated corrosion and fracture resistance in these environments. In this work we developed a representative model of the material microstructure including the metal grains, the material texture, and the precipitates along the grain boundaries and within the grains. The microstructural model was subjected to the boundary conditions identified at the notch root of a fracture mechanics sample and the results are used as input for a simulation of hydrogen diffusion from the surface of the notch, assuming the material has been introduced to a hydrogen producing environment. The diffusion of hydrogen was modeled by Fick’s law and included both hydrostatic stress and mobile dislocation velocity as driving forces. The influence of immobile dislocations was also modeled to account for the irreversible trapping. The results show that hydrostatic stress and immobile dislocation trapping can significantly alter the highest concentration of hydrogen and its location within the microstructure towards the fracture process zone. Mobile dislocation velocity has a small influence in determining the hydrogen distribution near the fracture process zone.

Importance of pyrolysis temperature and particle size on physicochemical and adsorptive properties of urban wood-derived biochar

Physicochemical properties of biochars made from urban wood waste at different pyrolysis temperatures (400-700 °C) and particle sizes (1-2 mm and 63-75 μm) were compared to their ability for heavy metals adsorption at various contact times (30-300 min) and adsorbent dosages (0.1-5 g L-1) in real landfill leachate. The yield, volatile matter, hydrogen and oxygen contents, and functional groups of biochars decreased with increasing pyrolysis temperature; while pH, electrical conductivity, ash, fixed carbon, and specific surface area (SSA) increased. FE-SEM images showed that the creation of pores on the surface of biochars increased significantly with increasing pyrolysis temperature. Moreover, particle size exhibited no significant effect on the properties of biochars (p>0.05), except for the SSA. The SSA of biochars with a particle size of 63-75 μm was significantly higher than that measured in 1-2 mm biochars. The adsorption efficiency of heavy metals from landfill leachate increases with increasing pyrolysis temperature, contact time and adsorbent dosage. Conversely, reducing the particle size increases the adsorption efficiency. The highest adsorption efficiency for Pb, Zn, Ni, Cd, and Mn was obtained as a result of using biochar pyrolyzed at 700 °C with a particle size of 63-75 μm (i.e., BC700/63-75) by 60.39%, 75.01, 64.36, 58.87%, and 71.15%, respectively. Pseudo second-order kinetic and the Langmuir isotherm were recognized as the most appropriate models to describe the adsorption process. The chemical adsorption was identified as the main mechanism for the adsorption of metal ions onto BC700/63-75.

Effects of Hydrogen Bonding in Silicon Nitride/Polyimide Passivation Bilayer in SiC Power Devices

Composition and morphology of two types of bilayers of plasma‐enhanced chemical vapor deposition hydrogened silicon nitride (SiNx:H) and polyimide (PI), as effcient barrier against moisture in SiC‐based power devices, are investigated. Two types of silicon nitrides are obtained by changing the flow ratios of the SiH4 and NH3 precursors. Rutherford Backscatterered analyses show that the Si/N ratio varies from 0.6 to 0.8. Elastic recoil detection analyses show that the sample with higher nitrogen content has a higher total bound hydrogen content of 7.8 × 1017 cm−2 with respect to the 7.1 × 1017 cm−2. Fourier‐transform infrared spectroscopy characterizations show Si–H group concentrations of 0.96 × 1017 and 6.86 × 1017 cm−2 and NH groups of 4.82 × 1017 and 2.28 × 1017 cm−2, respectively. Silicon nitride films with higher concentration of N–H groups show higher reactivity and permeability to water, making them less effective as a barrier layer. Atomic force microscopy analyses of a PI layer deposited on the nitride layer, SiNx:H/PI show for both type of samples a similar roughness, indicating planarization that can increase the adhesion of SiNx:H/PI and resistance to moisture. The delamination mechanism of the bilayer under pressure pot test conditions is proposed.

The influence of solid solution hydrogen and precipitated hydride on the creep behavior of Zircaloy-4

The effect of hydrogen on the creep rates of Zircaloy-4 claddings especially in the low hydrogen concentration remains largely unexplored while creep is considered a main mechanism for spent nuclear fuel failure along with hydride-induced mechanisms. Here, we study the influence of hydrogen on the creep behavior of low burnup Zircaloy-4 cladding from a microstructural perspective. The creep tests at 450°C and 120 MPa reveal that specimens with hydrogen contents below the terminal solid solubility for dissolution (TSSD) at the test temperature exhibited decreased creep resistance as hydrogen concentration increased, while those with hydrogen contents above the TSSD demonstrated increased creep resistance with higher hydrogen concentration. The lowest creep resistance occurs at the hydrogen concentration corresponding to the TSSD. Additional microstructural analyses using electron backscattered diffraction (EBSD) show the increasing intra-granular/inter-granular hydride ratio in the post-crept specimens as the hydrogen concentration decreases, suggesting that hydrogen atoms in solid solution aid creep progression. Also, an increased amount of twin boundaries is observed in post-crept specimens with hydrogen concentration above TSSD. These results suggest that creep assessment in spent nuclear fuels may require caution especially in low-burnup regime.

Hydrogen Nanobubbles and Oxidative Windows: Investigating How Varying Hydrogen Concentrations Influence Seed Germination and Stress Defense

The hydrogen molecule can effectively regulate plant growth and development, improving plant resistance to abiotic stresses. However, studies regarding the optimal concentration of hydrogen and the associated mechanisms of action in organisms are lacking. This study showed that the maximum germination rate of radish seeds decreased from 90% to 50% under the stress of cadmium ions (Cd2+), and hydrogen nanobubble (NB) water significantly alleviated the stress effect of Cd2+ on radish seed germination. A hydrogen concentration of 0.8 ppm had the best effect, reducing Cd2+ accumulation in radish seeds by 63.23% and increasing the maximum germination rate from 50% to 65%. At concentrations exceeding 1.2 ppm, the beneficial effect of hydrogen was weakened or even reversed. Consequently, we integrated the concept of the oxidative window into a REDOX balance model and demonstrated that an appropriate hydrogen concentration can effectively maintain the REDOX state within organisms. Transcriptome sequencing analysis revealed that hydrogen NB water modulated Cd2+ absorption and accumulation in seeds by regulating cell wall components, alleviating oxidative stress through oxidoreductase activity, and enhancing nutrient synthesis and metabolism. This collectively alleviated the inhibitory effect of Cd2+ on seed germination. This study is helpful for further understanding the effect of hydrogen concentration on the REDOX balance of seed germination, providing a theoretical basis for selecting hydrogen concentration to improve its effectiveness in agricultural fields.Environmental ImplicationCadmium is one of the most common heavy metal pollutants. It is more easily absorbed by plants and has great biological toxicity. If the cadmium concentration in soil is too high, it will cause significant inhibitory effects or serious damage to plant cell growth and division, photosynthesis, plant enzyme activity and nucleic acid metabolism, thereby inhibiting plant growth and development. Research indicates that hydrogen nanobubble water effectively alleviates the toxic effects of heavy metal stress on plants and aquatic organisms, offering new insights into addressing heavy metal pollution. This discovery holds significant importance for environmental restoration and maintaining ecological balance.

The Effects of Different Concentrations of Hydrogen-Rich Water on the Growth Performance, Digestive Ability, Antioxidant Capacity, Glucose Metabolism Pathway, mTOR Signaling Pathway, and Gut Microbiota of Largemouth Bass (Micropterus salmoides)

Hydrogen-rich water (HRW) is widely recognized for its growth promoting, antioxidant, and anti-inflammatory properties. However, little is known about the role of HRW in aquaculture. This study aims to investigate how different concentrations of HRW affect the growth performance, digestive ability, antioxidant capacity, mTOR signaling pathway, and gut microbiota of juvenile largemouth bass. We randomly assigned 360 fish (13.73 ± 0.1 g) to three treatments. The control group was maintained in regular water, while the treatment groups were treated with different concentrations of H2 dissolved in water, which were H1 (179.65 ± 31.95 ppb) and H2 (280.65 ± 64.43 ppb), respectively. Through an analysis of the three treatments, it was found that H1 significantly increased the final body weight, weight gain rate, specific growth rate, and survival rate, and reduced the feed conversion ratio (p < 0.05). In addition, the trypsin activity was significantly increased in the intestine (p < 0.05), and the expression of genes related to the glucose metabolism (pk and pepck) and mTOR (tor, akt, s6k1, 4ebp1, and ampka) signaling pathways were significantly increased in the liver in H1 (p < 0.05). The relative abundance of Blautia in the gut microbiota (p < 0.05) was significantly increased in H1. Therefore, these results indicated that H1 can significantly improve growth performance, promote intestinal digestion, activate the glucose metabolism pathway and mTOR signaling pathway, and increase the abundance of beneficial bacteria in the gut of largemouth bass. These findings provided valuable support for the application of HRW to support the healthy aquaculture of largemouth bass.

Supercapacitor-isolated water electrolysis for renewable energy storage

This study addresses a significant technological challenge in hydrogen production through electrolysis: the issue of gas crossover across the diaphragm between the cathode and anode, particularly under variable power conditions associated with renewable energy sources. We introduce a novel supercapacitor-isolated alkaline water electrolysis system utilizing a carbon-based supercapacitor sheet approximately 1 mm thick as an alternative to traditional diaphragms, effectively reducing gas crossover. At 25 °C and in 2.0 M KOH, our electrolysis system achieved a high current density of 0.736 A cm−2 for hydrogen evolution at 2.0 V, which was maintained at 0.023 A cm−2 even when the voltage was reduced to 0.9 V. Notably, the concentration of hydrogen to oxygen (HTO) remained low at 0.42 vol% with a current density of 0.01 A cm−2, surpassing the 28.5 vol% observed with a traditional diaphragm under similar conditions. At 70 °C, the electrolysis system exhibited an average hydrogen evolution rate of 0.952 A cm−2, with a specific energy consumption of 4.786 kWh Nm−3 (H₂) and a Faradaic efficiency of 99.5 %. Following a 55-day test under near-industrial conditions, the capacitive electrode demonstrated exceptional durability. These results represent a significant advancement in decoupled water electrolysis, indicating that the direct utilization of renewable energy for hydrogen production is feasible.

Turbulent partially cracked ammonia/air premixed spherical flames

The combustion of ammonia requires, for most energy conversion systems, a combustion promoter such as hydrogen to guarantee the start-up, stability and combustion efficiency. Partially cracked ammonia (PCA) can provide sufficient hydrogen concentrations to enhance the burning velocity in comparison with pure ammonia. However, little work exists on the use of PCA blends operating under relevant turbulent conditions. To that end the outwardly propagating spherical flame configuration was employed to determine the laminar and turbulent flame propagation characteristics of PCA (NH3/(H2+N2)) and corresponding binary (NH3/H2) mixtures across various turbulent combustion regimes. First, PCA and ammonia-hydrogen blends exhibit similar flame propagation rates under various turbulent intensities, even for the laminar case. The highest turbulent burning velocity was observed at leanest conditions, as opposed to laminar flames which exhibited highest flame speed at conditions above stoichiometry. Under rich conditions, no substantial flame enhancement due to turbulence was measured irrespective of the hydrogen content. This lack of flame enhancement under turbulent conditions is attributed to the effect of preferential diffusion with good agreement observed with trends in measured Markstein numbers. The normalized turbulent flame speed is dominated by the enhanced molecular diffusivity afforded by the presence of hydrogen up to 15 % enrichment, prior to decreasing upon further hydrogen addition under lean and stoichiometric conditions. This ‘bending’ phenomenon may be the contribution of several factors including; the transitioning between combustion regimes associated with low Damköhler numbers (Da) and flame thickening; merging of flamelets due to the presence of ammonia enhancing wrinkling; and combined changes in laminar burning velocity and preferential diffusional behavior. Furthermore, good agreement for turbulent flame speed is observed with a correlation that includes the influence of turbulent stretch (Ka) and non-equidiffusion (Le), with the agreement reducing with decreasing chemical to turbulent time scale ratios (Da << 1).

Exploring the application of hydrazine hydrate in protonic ceramic fuel cells: Strategies and performance improvements

Hydrazine hydrate, characterized by its high hydrogen content and eco-friendliness, garners extensive attention in the field of fuels. Its high energy density and rapid decomposition capabilities render it a promising fuel option for Proton-Conductor Solid Oxide Fuel Cells (PCFCs). Given the unique properties of hydrazine hydrate, this study employs a dendritic porous anode structure to facilitate faster fuel transport. Additionally, the influence of operational temperature and concentration of hydrazine hydrate as fuel on cell performance is analyzed. An effective vapor management strategy is implemented to address its decomposition into water vapor, resulting in a significant 23.17 % increase in the maximum power density (MPD) of the cell. To further enhance the performance of hydrazine hydrate fuel in PCFCs, a Pt–Al spherical catalyst is integrated within the anode structure of the cell. This approach notably improves the cell performance, yielding an additional 14.98 % increase in MPD. This design not only augments the electrical output but also effectively mitigates the degradation of the interface between the anode and the electrolyte. These optimization measures significantly improve the lifespan and reliability of the cell. The outcomes of this study demonstrate the practical feasibility of using hydrazine hydrate as a fuel in PCFCs.

Effect of composition gradient on detonation initiation in fuel-rich hydrogen-air mixtures in an obstructed channel

Numerical simulations were performed to study the effect of composition gradient and obstacle arrangement on detonation initiation in fuel-rich hydrogen-air mixtures. A third-order WENO method with adaptive mesh refinement (AMR) was used to solve the unsteady, fully-compressible, reactive Navier-Stokes equations coupled to a calibrated chemical-diffusive model (CDM). An obstructed channel at a blockage ratio of 0.3 filled with non-uniform hydrogen-air mixtures of an average H2 concentration 50 vol% was considered. The results show that unilateral obstacle arrangement is more conducive to flame acceleration (FA) and DDT than bilateral obstacle arrangement for both homogeneous and inhomogeneous mixtures. For inhomogeneous mixtures, the flame accelerates faster, and the detonation onset time is shorter when obstacles are placed on the sidewall with a hydrogen concentration closer to the stoichiometric ratio than the those when obstacles are placed on the other sidewall. However, the placement of unilateral obstacles on either the upper or lower sidewall does not significantly affect the DDT run-up distance. Besides, for fuel-rich inhomogeneous hydrogen-air mixtures, detonation tends to be initiated in the regions of high H2 concentration. Idealized models were introduced to simplify the intricate interactions of the reaction waves and flow fields to better understand the connection between H2 concentration distribution and detonation initiation. The analysis suggests that the minimum shock strength required for detonation initiation decreases with increasing equivalence ratio. This is supported by a kinetics analysis with detailed reaction model, which shows that ignition delay increases with decreasing equivalence ratio when detonation is about to be initiated.

Deep learning-based hydrogen leakage localization prediction considering sensor layout optimization in hydrogen refueling stations

To address the challenge and reliance on subjective experience in monitoring hydrogen leaks at hydrogen refueling stations (HRS), a regression prediction model for leakage localization based on Temporal convolutional network (TCN) and multimodal fusion technology is proposed for the first time. This model can accurately predict the spatial coordinates where the leakage source occurs in HRS. This study constructed a baseline dataset of hydrogen leakage, assisted by CFD simulation. Genetic Algorithm (GA) optimized the sensor layout to lower application costs while increasing monitoring effectiveness. The wind speed, wind direction, and hydrogen concentration data collected are multimodally fused to help the model mine more potential features. We compared the proposed model with current classical algorithms such as LSTM, GRU. The results demonstrate that our model achieves higher accuracy, delivering a localization model with an average error of just 0.54 meters. The proposed method can provide guidance for the layout of monitoring sensors in the large-scale HRS and provide more accurate diagnostic results for hydrogen leakage behaviors to ensure the safe operation of HRS compared to other methods.

A technique for detecting hydrogen and methane using refractive index sensitivity

Hydrogen and methane, as lightweight, high-energy fuels, occupy an important position in energy utilization and industrial production, and have broad application prospects. The safe extraction and production of new energy gases, as well as the safe utilization of hydrogen and methane is increasingly essential. The problem of detecting the type and concentration of hydrogen and methane is very important. This paper proposed a multi-peak high performance metamaterial refractive index sensor to fulfill the research gap for hydrogen or methane detection. We made unique designs on the patterns of the metasurface and made innovative combinations of materials. Through discussing different shapes and geometrical parameters, we get an optimal structure with a perfect absorption state, high sensitivity, and polarization independence. In the near-infrared spectral range spanning from 1700 nm to 2600 nm, resonance peaks were observed in the absorption spectrum at wavelengths of 1738.27 nm, 1843.17 nm, and 2368.13 nm. These peaks exhibited absorption rates respectively are 99.28 %, 89.71 %, and 99.69 %. The high sensitivity of the sensor under different environmental refractive indices was up to 715.43 nm/RIU. This leads to more precise and reliable identification of hydrogen and methane. The polarization dependence of our structure ensures consistent results under light illumination from various angles. This feature enhances the convenience of using it in both production and daily life, with fewer constraints and more accurate outcomes. The possible applications of this study lie in detecting the presence of hydrogen and methane gases, the exploration and extraction of new energy gases, as well as to monitoring and alarm systems for hydrogen and methane leaks. Moreover, it can serve as a validation system for the results of hydrogen and methane production processes. These applications are of significant importance for environmental protection and process safety.

Predicting the effect of cooling rates and initial hydrogen concentrations on porosity formation in Al‐Si castings

Predicting the effect of cooling rates and initial hydrogen concentrations on porosity formation in Al‐Si castings