Mixture Of Hydrogen Research Articles

Numerical Estimation of the Structural Integrity in an Existing Pipeline Network for the Transportation of Hydrogen Mixture in the Future

Hydrogen is gaining attention due to its potential to address key challenges in the sectors of energy, transportation and industry, since it is a much cleaner energy source when compared to fossil fuels. The transportation of hydrogen from the point of its production to the point of use can be performed by road, rail, sea, pipeline networks or a combination of the abovementioned. Being in the preliminary stage of hydrogen use, the utilization of the already existing natural gas pipeline networks for hydrogen mixtures transportation has been suggested as an efficient means of expanding hydrogen infrastructure. Yet, exploring this alternative, major challenges such as the pre-existence of cracks in the pipelines and the effect of hydrogen embrittlement on the material of the pipelines exist. In this paper, the macroscopic numerical modeling of pipeline segments with the use of the finite element method is performed. In more details, the structural integrity of intact and damaged pipeline segments, of different geometry and mechanical properties, was estimated. The effect of the pipeline geometry and material has been investigated in terms of stress contours with and without the influence of hydrogen. The results suggest that the structural integrity of the pipeline segments is more compromised by pre-existing longitudinal cracks, which might lead to an increase in the maximum value of equivalent Von Mises stress by up to four times, depending on their length-to-thickness ratio. This effect becomes more pronounced with the existence of hydrogen in the pipeline network.

Features of Hydrogen-Enriched Methane–Air Flames Propagating in Hele-Shaw Channels

Mixtures of hydrogen with common hydrocarbon fuels are considered viable for reducing carbon footprint in modern industry, power production, and transportation. The addition of hydrogen alters the kinetics and thermophysical properties of the mixtures, as well as the composition and properties of combustion products, requiring detailed research into the features of flame propagation in hydrogen-enriched hydrocarbon–air mixtures. Of particular interest are also the safety aspects of such fuels. In this paper, experimental results are presented on the premixed laminar flame propagation in channels formed by two closely spaced plates (Hele-Shaw cell), with the internal straight walls forming a diverging (diffuser) channel with the opening angles between 5 and 25 degrees. Methane–hydrogen–air mixtures with the hydrogen relative contents of 0%, 25%, and 50% and global equivalence ratio of unity were ignited by a spark near the closed narrow end of the channel. Experiments were performed with the gap width of 3.5 mm; video recordings were processed in order to determine the quantitative features of the flame front propagation (leading and trailing point coordinate, coordinates of the cusps, cell sizes and shapes). The main features of flame propagation (fast initial expansion, development of cellular flame, self-induced longitudinal oscillations) are obtained and compared to clarify the effect of hydrogen contents in the fuel and channel geometry (gap width, opening angle).

Study of metrological characteristics of household gas meters when measuring the volume flow rate of gas-hydrogen mixtures

The paper presents the results of studies of the influence of pure gaseous hydrogen and gas-hydrogen mixtures and the performance and metrological characteristics of membrane-type gas meters used in the household sector. For the study, membrane-type meters of leading domestic and European manufacturers were pre-selected. A series of static and dynamic tests were conducted for the meters. The static tests involved checking the air-tightness of the meters under the influence of gaseous mixtures. The dynamic tests involved measurements on a simulated test site with a work medium of pure hydrogen as well as hydrogen-methane mixtures. The proportions of the mixtures used were: 80% of methane and 20% of hydrogen, and 90% of methane and 10% of hydrogen respectively. A structural diagram of the measuring system was developed. The measurements were performed by comparing the volume of the gas that passed through the experimental meter with the volume measured by the reference meter. The measuring system was equipped with a means for measuring the pressure and temperature of the measuring medium to bring the results of the experiments to standard conditions. As a reference means in the assembled measuring system, a drum-type gas meter with a calibration characteristic pre-determined under laboratory conditions with a work air medium was used. After the experimental studies with the work hydrogen medium and hydrogen gas mixtures under the conditions of the test site, the metrological characteristics were re-determined under laboratory conditions for the reference meter. To conduct the experiments with the maximum possible accuracy and to exclude the influence of additional errors on the measurement result, a specialized software was developed to automate the measurements of the volume of the gas passing through the reference meter, measuring the pressure and temperature of the work medium and fixing the required value of the gas volume flow rate. The results of the experiments for several meters are presented in the form of tabular values and graphs. General conclusions were made regarding the influence of hydrogen and gas-hydrogen mixtures on the change in metrological characteristics of household gas meters.

Highly Efficient Analysis on Biomass Carbohydrate Mixtures by DREAMTIME NMR Spectroscopy.

Proton (1H) NMR spectroscopy presents a powerful tool for biomass mixture studies by revealing the involved chemical compounds with identified ingredients and molecular structures. However, conventional 1H NMR generally suffers from spectral congestion when measuring biomass mixtures, particularly biomass carbohydrate samples, that contain various physically and chemically similar compounds. In this study, a targeted detection NMR approach, DREAMTIME, is exploited for studying biomass carbohydrate mixtures by spectroscopically targeting the desired compounds in separate 1D NMR spectra. From three model mixtures, namely, the C6 sugar isomerization mixture, C5 sugar catalytic hydrogenation mixture, and d-glucose and d-xylose fermentation mixture, to a real reaction mixture of sucrose hydrolysis, DREAMTIME achieves satisfactory performance in compound identification and mixture analysis even when mixture signals are crowded and overlapped in conventional 1H NMR. Additionally, DREAMTIME is performed in a rapid 1D acquisition manner, making it available for highly efficient analysis on various biomass reactions. Our results suggest that DREAMTIME provides an effective method for wide applications to complex biomass mixture analysis with explicit compound identification, targeted component monitoring, and conversion reaction detection.

Investigation of Combine Cycle Power Plants with Low-Grade Heat Utilization Working Methane-Hydrogen Mixtures

The Russian energy sector remains heavily reliant on thermal power plants, with gas generation accounting for approximately 66% of the installed capacity. However, the industry faces challenges such as depletion of reserves, rising prices for hydrocarbons, and increasing concentrations of carbon dioxide in the atmosphere. This study focuses on developing new scientific and technical solutions to increase the efficiency and environmental safety of combined cycle power units. The research involves structural and parametric optimization of trinary cycle power plants operating on a methane-hydrogen mixture, as well as the development and optimization of turbine and heat exchange equipment for low-temperature power plants. The results show that the transition to trinary CCGT (Combine Cycle Gas Turbine) units with deep utilization and the use of hydrogen fuel can significantly reduce specific CO2 emissions and increase energy efficiency up to 0.21% with also increases in capacity of turbine of approximately 17 MW. The aim of this research is to calculate the efficiency, cost effectiveness and environmental-friendly solution for power generation using mixture of hydrogen- methane as fuel in combine cycle power plant that includes ORC. Additionally, the efficiency of the organic Rankine Cycle (ORC) benefits from the increased moisture, with capacity improvements of 1-2 MW observed when the hydrogen proportion rises from 25% to 50%. Moreover, the potential for zero emissions, coupled with significant increases in power output and efficiency, underscores hydrogen's role as a pivotal component in the future of energy production.

Coherence Properties of a Supercontinuum Generated by Cascade Raman Processes in a Hollow-Core Fiber Filled with a Mixture of Deuterium and Hydrogen

Here, we report a numerical study of supercontinuum generation in an antiresonant optical fiber with a hollow core filled with a mixture of deuterium (D2) and hydrogen (H2). For 1 ps pulses at a wavelength of 1.03 μm with different chirp values, we demonstrate a possibility of obtaining a mid-IR coherent supercontinuum with a spectral width of 2300 nm, initiated by cascade processes at resonance frequencies of vibrational and rotational levels of D2 and H2. We show that an increase in the chirped pulse duration to 25 ps while maintaining the energy and spectral width allows increasing the quantum conversion efficiency in the mid-IR from 10 to 50% and expanding the range of optimal fiber lengths at which a high degree of supercontinuum coherence is achieved.

Evaluation of the Effect of Natural Gas Enrichment with Hydrogen on Gas Turbine Emissions: Numerical Study Based on Chemical Equilibrium

Decarbonization involves the intensive use of renewable energy to obtain a sustainable energy matrix. Brazil has an electrical matrix strongly anchored in renewable sources, historically in hydraulic energy, and more recently, in solar, photovoltaic, and wind sources. The latter are stochastic and, therefore, have strong restrictions on their insertion into the matrix in a broad and dominant manner. Due to these limitations, excess supply can be used to produce green hydrogen and even methane in a process called methanation (chemical reaction between CO2 and H2). The use of electrical energy from renewable sources for the production of fuels is known in literature as power-to-gas. These fuel vectors (H2 and CH4) can be used directly to generate energy or can be mixed with natural gas to enrich it in terms of energy and potentially reduce emissions. This study evaluates the effect of enriching mixtures of natural gas and hydrogen on CO, CO2, and NOx emissions, considering combustion applications in Gas Turbines. The analyses were numerical and involved the use of a thermodynamic combustion model with chemical equilibrium. The chemical equilibrium model is based on chemical equilibrium constants and assumes that the reactants and products are ideal gases. The volumetric fractions of H2 in the mixture from 0 to 30% and the effect of the combustion pressure were investigated. The pressure was varied according to the application chosen. Gas turbines are part of the combined power cycles, and plants can operate with gas turbines of different pressure ratios according to the model, power, and manufacturer of the Gas Turbine. The analyses focused on medium and large gas turbines, and the chosen pressure range was 12:1 to 24:1.

Ultrasonic gas flow and concentration measurement in hydrogen and nitrogen gas mixtures

Ultrasonic gas flow and concentration measurement in hydrogen and nitrogen gas mixtures

Study of the Combustion Characteristics of a Compression Ignition Engine Fueled with a Biogas–Hydrogen Mixture and Biodiesel

Increasing the use of renewable energy sources is essential to reduce the use of fossil fuels in internal combustion engines and to reduce greenhouse gas emissions. An experimental and numerical simulation study of the combustion process of a compression ignition engine was carried out by replacing fossil diesel with a dual fuel produced from renewable energy sources. In conventional dual-fuel applications, fossil diesel is used to initiate the combustion of natural gas or petroleum gas. In the present study, fossil diesel was replaced with advanced biodiesel – hydrotreated vegetable oil, and natural gas was replaced with biogas. In the experimental study, a gas mixture of 60% natural gas (by volume) and 40% carbon dioxide (by volume) was used to replicate the biogas while maintaining a 40%, 60%, and 80% gas energy share in the fuel. It was observed that using fossil diesel and biogas in the dual-fuel engine significantly slowed down the combustion process, which normally resulted in poorer energy performance. One way to compensate for the lack of energy (due to the presence of carbon dioxide) in the cylinder is to use a gas such as hydrogen, which has a high energy content. To analyze the effect of hydrogen on the dual-fuel combustion process, hydrogen gas was added to the replicated biogas at 10%, 20%, and 30% of the natural gas volume, maintaining the biogas at a (natural gas + hydrogen)-to-carbon dioxide volume ratio of 60%/40% and the expected gas energy share. The combustion process analysis, which was conducted using the AVL BOOST software (Austria), determined the heat release rate, temperature, and cylinder pressure rise in the dual-fuel operation with different renewable fuels and compared the results with those of fossil diesel. It was found that when the engine was operated at medium load and with the flammability of the biogas approaching the limit, the addition of hydrogen significantly improved the combustion characteristics of the dual-fuel engine.

Spectrometers of Neutrons and Fast Atoms of Tokamak Thermonuclear Plasma Based on CVD Synthesized Diamond Single-Crystal Films

High radiation resistance, chemical inertness, the ability to operate at elevated temperatures, high mobility and efficiency of charge-carrier collection are important properties of diamond for designing detectors and spectrometers of ionizing radiation. Currently, diagnostics of neutrons and neutral particle fluxes based on diamond detectors for the ITER thermonuclear reactor are justified and developed. This work presents the results of a Raman spectroscopy and photoluminescence spectroscopy study of the electronic quality of synthesized epitaxial diamond films obtained by vapor deposition in a hydrogen and methane mixture in the ARDIS reactor on boron-doped single-crystal diamond substrates. To confirm their electronic quality, detectors have been made from films selected by spectrometric methods and the charge collection efficiency and energy resolution have been measured when irradiated with alpha particles from a 241Am source and 14.7 MeV fast neutrons from the ING-07T2 neutron generator.

Locational marginal pricing of energy in pipeline transport of natural gas and hydrogen with carbon offset incentives

We propose an optimization formulation for locational pricing of energy transported through a pipeline network that carries mixtures of natural gas and hydrogen from distributed sources to consumers. The objective includes the economic value provided by the pipeline to consumers of energy and suppliers of natural gas and green hydrogen, as well as incentives to lower carbon emissions by consuming the latter instead of the former. The optimization is subject to the physics of gas flow and mixing in the pipeline network as well as engineering limits. In addition to formulating this mathematical program, we synthesize the Lagrangian and derive analytical expressions for the dual variables. We propose that the dual solution can be used to derive locational marginal prices of natural gas, hydrogen, and energy, as well as the decarbonization premium paid by consumers that receive hydrogen. We derive several properties of solutions obtained using the proposed market mechanism, and demonstrate them using case studies for standard 8-node and 40-node pipeline test networks. Finally, we show that optimization-based analysis of the type proposed here is critical for making sound decisions about economic policy and infrastructure expansion for blending green hydrogen into existing natural gas pipelines.

Photothermal Dry Reforming of Methane on Yolk‐Shell Co–Ni Alloy@SiO2 Catalyst

AbstractPhotothermal dry reforming of methane (PT‐DRM) is an appealing pathway to convert carbon dioxide and methane into synthesis gas, a mixture of carbon monoxide and hydrogen, via photothermal heating induced by concentrated sunlight. However, coke formation and sintering of active metal nanoparticles are key issues for catalyst stability. In the present study, we demonstrated Co–Ni alloy nanoparticles encapsulated with a porous SiO2 shell exhibited improved catalytic activity and stability for PT‐DRM using visible/near‐IR light irradiation without any other external heating. The addition of a tiny amount of Co (1–5 mol% relative to total metal) and SiO2 encapsulation enhanced the stability by simultaneously suppressing coke formation and sintering of the metal nanoparticles. Furthermore, we revealed that the position of the light irradiation spot has a crucial role in the conversions of methane and carbon dioxide and product selectivity, presumably due to the large temperature gradient under the light irradiation. These findings would contribute to designing effective PT‐DRM catalysts with improved activity and enhanced resistance for both coke formation and sintering and emphasize the significant contribution of the temperature gradients to the performance of PT‐DRM.

Growth of Diamond on Si, SiC, Mo and Diamond Substrates for Heat Spreader, Optical Window, and Surface Graphitized Devices

Introduction Diamond, owing to its exceptional impact resistance, high thermal conductivity, broad-spectrum optical transparency, elevated breakdown field strength, and superior carrier mobility, finds widespread application in diverse fields such as high-power laser windows, efficient heat spreader, and high-performance semiconductor devices. Experimental 1. Heteroepitaxial Growth of Polycrystalline Diamond on Si, SiC, and Mo Substrates:In this part, substrates employed include double-side polished 4H-polytype SiC, (100) single-side polished single-crystal Si wafers, and Mo substrates. Ultrasonic grinding of substrates using diamond powder ethanol suspension to promote the dispersion of nucleation seeds, followed by sequential ultrasonic cleaning in acetone, ethanol, and deionized water.Subsequently, MPCVD was used for diamond growth, using hydrogen, methane, oxygen, and a mixture of hydrogen and nitrogen as reaction gases. Using different processes to produce efficient heat sinks and high-power laser windows. 2. Homoepitaxial Growth of Single-Crystal Diamond on Diamond Substrates:In the homoepitaxial growth process, (100) double-side polished single-crystal diamond substrates are utilized. No need for ultrasonic grinding steps, cleaning steps are the same as above. Then use MPCVD for homogeneous epitaxial growth of single-crystal diamond. 3. Investigation of Graphitized Surface Devices on Diamond:This study also investigated the graphitization devices on diamond surfaces. A high-temperature metal-catalyzed method is employed to promote surface graphitization of diamond. Firstly, polish and clean the diamond. Subsequently, a 300 nm thick nickel layer is deposited on the diamond surface. Rapid thermal annealing is then performed at 1300°C to form a highly conductive graphite layer. This process successfully prepares capacitor samples with a graphite-diamond-graphite three-layer structure. Results and Discussion 1. High-Power Laser Window Plates:The fabricated laser window plates utilize Si, SiC and Mo substrates, employing an ultra-low nitrogen growth process with a growth rate of approximately 3.7 µm/h. After double-sided polishing, the thickness reaches 1 mm. At room temperature, the transmittance at 10.6 µm wavelength approaches the theoretical maximum, reaching 67.9%. The overall thermal conductivity exceeds 1950 W/mK, approximating that of single-crystal diamond.Raman spectroscopy and XRD results indicate that the primary component is polycrystalline diamond with a (110) crystallographic orientation. Laser testing results demonstrate that these window plates possess a high laser-induced damage threshold with a peak energy of 60 J/cm2 and a peak power of 12 MW/mm2, capable of withstanding high-power CO2 laser output. 2. Heat Spreader:This study involves depositing diamond on Si and SiC substrates, forming diamond-based composite materials. This significantly improves the heat dissipation efficiency of the devices, bringing their performance closer to theoretical limits. The deposition process employs a low-nitrogen technique to balance growth rate and defect density, achieving a growth rate of approximately 5 µm/h.Raman spectroscopy and XRD results indicate that the primary component is polycrystalline diamond with a (110) crystallographic orientation. Although the increased nitrogen content results in lower optical transmittance compared to optical window plates, the grain size can be increased from 124 nm to 22 μm through production process adjustments, thereby enhancing thermal conductivity.Test results demonstrate that the thermal conductivity of the Si-diamond composite material reaches 450 W/mK,3 times that of single-crystal Si. The SiC-diamond composite material achieves a thermal conductivity of 500 W/mK,3.5 times that of SiC. 3. Single-Crystal Diamond:The transmittance and thermal conductivity of single-crystal diamond grown by homoepitaxial growth are superior to those of polycrystalline diamond. However, limitations in size and growth conditions restrict its large-scale application in heat spreaders and optical windows. Single-crystal diamond is more suitable for manufacturing semiconductor devices such as diamond capacitors, Schottky diodes, and hydrogen-terminated MOSFETs.The author has conducted research on doping of single-crystal diamond. Characterization through Raman spectroscopy, XRD, and TEM confirms that the primary component is single-crystal diamond with a (100) crystallographic orientation. The dislocation density is below 103/cm2, meeting the stringent requirements for semiconductor devices. 4. Graphite-Diamond-Graphite Capacitors:Utilizing prepared diamond, graphite-diamond-graphite capacitors were fabricated. Measurements using a semiconductor parameter analyzer revealed a high capacitance value of 4 nF. TCAD simulation indicated a breakdown voltage as high as 1100 V. This research explores a novel method for diamond capacitor fabrication. Conclusions Diamond heteroepitaxial grown on Si, SiC, and Mo substrates has prepared high-power laser windows with 67.9% optical transmittance at 10.6 μm wavelength, and composite materials with thermal conductivity enhanced to 3-3.5 times that of the original materials. Homoepitaxially grown diamond on single-crystal diamond substrates exhibits a dislocation density below 10³/cm², meeting the requirements for semiconductor device substrates. Furthermore, this research has developed a novel diamond capacitor fabrication technique, yielding capacitors with a capacitance of 4 nF and a breakdown voltage of 1100 V.

Palladium Nanoparticles-Modified AB5-Type Alloy in Ionic Liquid-Based Electrolytes for Novel Hydrogen Storage Systems

Constantly growing demand for electricity storage devices has inclined scientists to develop new systems for accumulating energy and to improve those currently used. Portable devices and fully electric or hybrid vehicles require efficient and reliable rechargeable batteries. Among most common battery technologies Ni-MH batteries deserve special attention as they are considered well suited for these applications because of their high energy density, good cyclability, safety and wide operating temperature range [1]. Additionally, due to the absence of toxic metals and volatile solvents, they are one of the most environmentally friendly battery systems.As a negative electrode material various hydrogen-absorbing metals and alloys differing in hydrogen storage capacity, hydrogen sorption kinetics and hydride stability are applied. AB5-type alloys, where A is a mixture of rare earth elements while transition metals such as Ni, Al, Co and Mn constitute component B, can be designed or modified to provide optimum performance of the Ni-MH system [2]. The electrochemical properties of the alloy depend on the microstructure, the nature and amount of each element in the intermetallic compound, and the electrochemical processes taking place. Palladium, which is capable of hydrogen absorption on its own, is particularly interesting in terms of application to the modification of electrode material, especially in the form of nanoparticles (NPs). Decorating AB5-type alloy with Pd-NPs led to the improvement of discharge capacity and high rate dischargeability [3]. Moreover, Pd shows a catalytic effect on the kinetics of the charge transfer process at the electrode surface, increasing the activation rate of the metal alloy [4].Concentrated alkaline aqueous electrolytes used in Ni-MH batteries cause significant corrosion of the negative electrode material. This problem can be overcome by applying ionic liquid-based electrolytes, as ionic liquids (ILs) exhibit good conducting properties and a wide electrochemical stability window. In order to provide hydrogen source both protic ILs and mixtures of organic acids with ILs can be used.The focus of presented study was to evaluate the electrochemical performance of hydrogen absorbing Pd-NPs-modified AB5-type alloy in binary mixtures of 1-ethyl-3-methylimidazolium methanesulfonate ([EMIM][MS]) with carboxylic acids: acetic and trifluoroacetic acid. These mixtures were chosen as their electrochemical and physicochemical properties were extensively studied in our previous works with the use of palladium limited volume indicative electrode (Pd-LVE) which revealed that they are promising electrolytes for hydrogen sorption measurements. The palladium content in the prepared electrode material is ca. 3.5 wt %, which is enough to improve the properties of the used alloy. In order to overcome the problems with rather high viscosity, low conductivity and high cost of ILs, we also preliminarily tested the prospect of using chosen ILs as additives to conventional aqueous KOH solutions.Developed systems were studied using electrochemical methods: cyclic voltammetry (CV), chronoamperometry (CA) and chronopotentiometry (CP), which was used to determine the hydrogen absorption capacity of the electrode material. The measured capacity of AB5-Pd-NPs LVE in 2 M HAC/[EMIM][MS] binary mixture corresponds to 85.4% of the electrochemically determined capacity of pristine AB5 alloy in standard KOH aqueous solution, while in 1 M FAC/[EMIM][MS] significantly lower. The type of acid present in the acid/IL mixture does not influence the discharge potential main plateau, which is ca. 0.2 V, while a clear difference in charging potential can be observed (Figure 1 A). In addition to electrochemical analysis, SEM imaging was performed, which revealed noticeable changes in the electrode surface before and after electrochemical treatment in IL/acid mixtures, depending on the acid used (Figure 1 B-D). Acknowledgements This work was funded by National Science Centre (NCN, Poland), grant number 2021/41/B/ST5/04047.

Electrochemical Performance of Fuel Electrodes in Solid Oxide Co-Electrolysis Cells Operated Under Various Conditions

Introduction Solid oxide co-electrolysis cells are electrochemical devices which can electrolyze steam and carbon dioxide at the same time into hydrogen and carbon monoxide which are components of synthesis gas. Waste heat can be recycled effectively by creating a combined system of carbon hydrate synthesizer and the cells, and along with high temperature operation, carbon dioxide can be also recycled to carbon hydrates with high efficiency. To design a co-electrolysis system, and calculate efficiency numerically, characteristics of the solid oxide co-electrolysis cells must be clarified. In this study, we aim to obtain and quantify electrochemical characteristics of fuel electrodes in solid oxide co-electrolysis cells by measuring I-V curve and calculating exchange current density in various operating conditions, to be applied in solid oxide co-electrolysis system planned as future work. Experimental The tested electrolyte-supported solid oxide cell consists of Ni-YSZ (8 mol%Y2O3 – 92 mol%ZrO2) cermet, a composite of Ni and YSZ, as fuel electrode, YSZ plate as electrolyte, and LSCF ((La0.6Sr0.4)(Co0.2Fe0.8)O3) as air electrode. Gas mixture of hydrogen, vapor, carbon-dioxide, and nitrogen were supplied to the fuel electrode with the total flow rate of 100 ml min-1. Some conditions to evaluate the effect of gas composition on the fuel electrode performance are shown in Figure 1 (a). On the other hand, dry air was supplied to the air electrode with the total flow rate of 150 ml min-1. I-V curve and electrochemical impedance were obtained using a Solartron electrochemical measurement system. A phenomenological exchange current density equation of the fuel electrode was obtained by regression analysis based on the experimental results [1-3]. Results and Discussion Figure 1 (b) shows the fitted exchange current density obtained by considering hydrogen-water vapor reaction as well as carbon monoxide-carbon dioxide reaction. From the peak in the graph, the obtained exchange current density depended on the partial pressures of hydrogen and water vapor. Therefore, in the cases shown in Figure 1 (a), compared with CO2 electrolysis reaction, steam electrolysis reaction seems to be the dominant reaction at fuel electrodes in solid oxide co-electrolysis cells [4,5]. In the presentation, dependencies of operating temperature, and partial pressure of each gas component will be discussed. Reference [1] T. Fukumoto, N. Endo, K. Natsukoshi, Y. Tachikawa, G.F. Harrington, S.M. Lyth, J. Matsuda, and K. Sasaki, Int. J. Hydrogen Energy, 47 (37), 16626-16639 (2022).[2] K. Takino, Y. Tachikawa, K. Mori, S.M. Lyth, Y. Shiratori, S. Taniguchi, and K. Sasaki, Int. J. Hydrogen Energy, 45 (11), 6912-6925 (2020).[3] W. Dreyer, C. Guhtke, and R. Müller, Phys. Chem. Chem. Phys., 18, 24966-24983 (2016).[4] S.D. Ebbesen, R. Knibbe, and M. Mogensen, J. Electrochem. Soc., 159 (8), F482-F489 (2012).[5] S-H. Lee, J-W. Lee, S-B. Lee, S-J Park, R-H. Song, U-J. Yun, T-H. Lim, Int. J. Hydrogen Energy, 41 (18), 7530-7537 (2016). Figure 1

Detonation effect of hydrogen-oxygen mixtures at various initial pressures and hydrogen concentrations in obstructed channels

Numerical investigations have been conducted for the effects of initial ambient pressure, hydrogen concentration, and obstacle distribution on the chemical kinetic characteristics of stable detonation propagation, as well as the changes in the shape and size of detonation cells. The configuration studied is a rectangular channel with regularly spaced obstacles containing the mixture of hydrogen and oxygen. The results indicate that under the same blockage ratio conditions, the position where detonation is generated in the channel with obstacles distributed on one side is farther than in the channel with obstacles distributed on both sides. However, there is no significant change in flame speed or detonation cell size after reaching stable detonation in both cases. The study reveals that under fuel-rich conditions, an increase in hydrogen concentration leads to an increasing duration for the flame to propagate to the end of the channel, accompanied by the distance from the ignition point to the occurrence of detonation also increases. Additionally, under fuel-lean conditions, as the hydrogen concentration decreases, the distance from the ignition point to the occurrence of detonation also increases. The study identifies the limiting concentration for hydrogen detonation is in the range of 18.3 %–60 %. As the initial pressure within the channel decreases, the location of detonation occurrence is farther away from the ignition point. And higher initial ambient pressures make detonation more likely to occur within the channel and the size of stable detonation cells decreases as the initial ambient pressure increases.

Gas jet structure effects on fuel concentrations and flames in a hydrogen low-pressure direct-injection spark-ignition engine

This study aims to find the impact of the nozzle shape of a side-mounted, 3.5-MPa pintle injector on hydrogen concentration and flame development in a low-pressure direct-injection spark ignition (H2LPDI) engine. To this end, endoscopic high-speed imaging of gas jet laser shadowgraph and flames as well as spark-induced breakdown-spectroscopy (SIBS) method are applied to one of the inline four cylinders of H2LPDI engine. Two engines with endoscopic access are used: one motored engine for high-speed laser shadowgraph imaging of gas jet development and the other combustion engine for SIBS-based spark gap [Formula: see text] measurements and high-speed hydrogen flame imaging. The gas jet visualisation showed that a nozzle with a narrower jet spreading angle leads to more turbulent jet boundaries and the jet axis being directed more towards the piston. Due to higher axial momentum, the narrower spreading angle nozzle also caused enhanced jet penetration across the in-cylinder tumble flow. This jet development pattern resulted in locally leaner hydrogen mixtures near the centrally mounted spark plug at the time of ignition, evidenced by a higher difference between spark gap λ and global λ. As a result, the flame size was measured smaller at any fixed combustion stage. For both nozzle types, the injection timing was also varied between 150 and 120 °CA bTDC but there was no significant difference measured in spark gap [Formula: see text] and flame size compared to that associated with the nozzle type.

Hydrogen–steam separation using mechanical vapor recompression cycle

Solar thermochemical hydrogen production is a promising pathway for producing sustainable fuels and chemicals. One of the main challenges in the development of these processes is their low steam conversion extent, dictated by its restrictive thermodynamics requiring extremely high temperatures over 1500°C and low oxygen partial pressure to obtain a steam conversion over 10%. While condensing the unreacted steam is technically simple, the latent heat is thus rendered useless for the process. In many cases, this lost heat can be larger than the higher heating value of the produced hydrogen. We propose a new separation method based on a mechanical vapor recompression cycle, enabling the recovery of the latent heat by compressing the steam–hydrogen mixture prior to the condensation process, thus creating a temperature difference between the hot exhaust and cold inlet streams. We show that this separation method can recover the latent heat and keep its quality in relevant operating conditions while requiring less than 14% of the recovered heat for compression work, resulting in a coefficient of performance over 7. This method increases the viability of solar thermochemical hydrogen production cycles, especially under limited steam conversion conditions.

Investigation of the explosive atmospheres extent of hydrogen and methane gas mixtures by calculation and FLACS-CFD simulation

Explosive atmosphere is defined as a mixture of dangerous substances with air, under atmospheric conditions, in the form of gases, vapours, mist or dust in which, after ignition has occurred, combustion spreads to the entire unburned mixture. Methane-hydrogen mixtures will become more and more important for energy use in the near future. It has many positive economic and environmental benefits, while the risk of explosion is partly forgotten. It is necessary to identify hazardous areas in the interpretation of technological equipment. The applicable standard, EN IEC 60079-10-1:2020, defines the extent of the explosive atmosphere and zones for a given material, but does not cover mixtures. The objective of the study is to determine the explosive hazard areas of different mixtures of hydrogen and natural gas (methane), by adding additional possible relationships to the initial equations of the standard, and to compare them with the results of the models built in the FLACS-CFD simulation.

Flame Speed Measurements of Ammonia–Hydrogen Mixtures for Gas-Turbines

Abstract Recent findings from the U.S. Energy Information Administration project an increase in domestic fossil fuel consumption (e.g., petroleum and natural gas) and global greenhouse gas emissions through 2050 (Nalley, S., 2021, “International Energy Outlook 2021 (IEO2021),” IEO2021 Release, CSIS, Center for Strategic and International Studies, Washington, DC, Technical Presentation, pp. 2–12). Consequently, advanced combustion research aims to identify fuels to mitigate fossil fuel consumption while minimizing exhaust emissions. Ammonia (NH3) is one of these candidates, as it has historically been shown to provide high energy potential and zero-carbon emission (CO and CO2) (Hayakawa, A., Goto, T., Mimoto, R., Arakawa, Y., Kudo, T., and Kobayashi, H., 2015, “Laminar Burning Velocity and Markstein Length of Ammonia/Air Premixed Flames at Various Pressures,” Fuel, 159, pp. 98–106). As a hydrogen (H2) carrier, NH3 serves as a possible solution to the U.S. Department of Energy's Hydrogen Program Plan by providing efficient H2 storage and conservation capabilities (U.S. Department of Energy, 2020, “Department of Energy Hydrogen Program Plan,” U.S. Department of Energy, Washington, DC, Report No. DOE/EE-2128). As a result, applied turbine-combustion research of NH3 and H2 fuel has been conducted to identify combustion performance parameters that aid in the design of sustainable turbomachinery (Chiong, M.-C., Chong, C., Ng, J., Mashruk, S., Chong, W., Samiran, N., Mong, G., and Medina, A., 2021, “Advancements of Combustion Technologies in the Ammonia-Fuelled Engines,” Energy Convers. Manage., 244, p. 114460). One of these key combustion parameters is the laminar burning speed (LBS). While abundant literature exists on the combustion of NH3 and H2 fuels, there is not sufficient evidence in high-pressure environments to provide a comprehensive understanding of NH3 and H2 combustion phenomena in turbine-combustor settings. To advance the state of the knowledge, NH3 and H2 mixtures were ignited in a spherical chamber across a range of equivalence ratios at 296 K and 5 atm to understand their flame characteristics and LBS which was determined using a multizone constant volume method. The experimental conditions were selected according to primary turbine-combustor conditions, as much research is needed to support NH3–H2 applicability in turbomachinery for power generation. The effect of H2 addition to NH3 fuel was observed by comparing the LBS for various NH3–H2 mixture compositions. Experimental results revealed increased LBS values for H2 enriched NH3, with the maximum LBS occurring at stoichiometry. The experimental data were accurately predicted by the University of Central Florida (UCF) NH3–H2 mechanism developed for this investigation, while NUI 1.1 simulations overestimated recorded LBS data by a significant margin. This study demonstrates and quantifies the enhancing effect of H2 addition to NH3 fuels via LBS and strengthens the literature surrounding NH3–H2 combustion reactions for future work.