Hydrogen Mixed Gas Research Articles

Research on aerodynamic performance of centrifugal compressors for hydrogen-mixed natural gas.

Natural gas-doped hydrogen transportation has been widely used in industrial engineering. The change of the physical parameters of the conveying medium affects the working performance of the centrifugal compressor. This study aims to explore the aerodynamic performance of centrifugal compressors for hydrogen mixed natural gas, including the effects of hydrogen blending ratio (HBR) and inlet temperature on the pressure ratio and isentropic efficiency of compressors. The numerical simulation method is used and the results are compared with the experimental results to determine the reliability of the numerical simulation method. The results show that the pressure ratio decreases with the increase of HBR where the inlet temperature and rotation speed are constant. The pressure ratio and efficiency of the compressor are the highest when the conveying medium is pure natural gas (HBR = 0). The maximum pressure ratio reduction is 4.8% when the HBR is 5% and the inlet temperature is increased by 20 K. In summary, when the conveying medium of the compressor changes from pure natural gas to hydrogen-mixed natural gas, the working range and efficiency of the compressor will be reduced. Therefore, it is necessary to increase the rotation speed of the compressor or redesign the centrifugal compressor for hydrogen-mixed natural gas in order to achieve a constant flow rate at the outlet of the compressor.

Low-carbon energy scheduling for integrated energy systems considering offshore wind power hydrogen production and dynamic hydrogen doping strategy

This paper proposes a low-carbon energy scheduling model for integrated energy systems (IES) considering offshore wind power hydrogen production and dynamic hydrogen doping strategy. The offshore wind electrolysis system, hydrogen mixed gas turbine (HMGT), carbon capture, utilization and storage, and laddered carbon trading are introduced to reflect the values of hydrogen blending in carbon emission reduction for IES. A carbon emission and combustion model for HMGT based on the system thermodynamics and chemical reaction kinetics is presented. The dynamic hydrogen doping strategy is leveraged to consider the impact of gas composition variations on HMGT operating and gas system. Then, an energy balance-based quasi-steady-state model is proposed to deal with the different calorific value of the gas mixture. In order to effectively solve the resulting highly nonlinear and nonconvex problem arising from the varying hydrogen blending ratio, the nonlinear hydrogen production efficiency, and the convex–concave energy balance-based quasi-steady-state model, a tractable solution formulation is proposed. Numerical results illustrate the effectiveness of the proposed model.

Low-carbon operation of integrated electricity–gas system with hydrogen injection considering hydrogen mixed gas turbine and laddered carbon trading

Green hydrogen produced by the power-to-gas facilities can be blended into the natural gas system, which is a promising way toward a low-carbon energy system. This paper proposes a laddered carbon trading-based operation model for integrated electricity–gas system with hydrogen injection considering the complex combustion properties of hydrogen mixed gas turbine (HMGT). The power-to-hydrogen, hydrogen methanation, and carbon emission processes are combined with the methane reactor and the flexible carbon capture, utilization and storage facility. Then, a HMGT combustion model based on the system thermodynamics and chemical reaction kinetics is introduced. The piecewise linearization technique is adopted to describe the varying hydrogen production efficiency of electrolysis system. Moreover, an energy balance based quasi-steady-state model to deal with the calorific value problem of the gas mixture is proposed and solved by an advanced sequential cone programming algorithm. Case studies are carried on a 30-bus-20-node system and a 197-bus-171-node practical system in Northwest China to illustrate the effectiveness of the proposed model.

Jump and hysteresis of plasma density in the spatial afterglow of inductively coupled plasmas

In this work, jump and hysteresis of plasma density between low-density (LD) and high-density (HD) in the spatial afterglow of inductively coupled plasmas are experimentally studied for different gas discharges. A quartz plate with a micropore is used to independently control the pressures in the active plasma and spatial afterglow. The plasma density jump from LD to HD vs the pressure in the spatial afterglow only exists in a larger micropore diameter. By adjusting the pressure back and forth, a hysteresis loop in plasma density is formed. The light intensity and excitation rate vs the pressure corresponds well to the jump and hysteresis of plasma density. Therefore, the abrupt changes in ionization rate are responsible for the jump and hysteresis of plasma density. Compared with argon discharges, the critical pressure for the jump from LD to HD is higher in nitrogen discharges, forming a larger hysteresis loop. For hydrogen discharges, the jump from LD to HD is less significant and the hysteresis loop almost disappears. In argon–hydrogen mixed gas discharges, there is no hysteresis loop in plasma density. Experimental results obtained using Langmuir double probes and spectrometer achieve qualitative agreement in gas discharges mentioned above.

Investigations of the growth and physical characteristics of ZNF2-DOPED GA2O3 thin films

This study began by preparing gallium oxide (Ga2O3) doped with zinc fluoride (ZnF2) and manufacturing a target material. Subsequently, electron beam (e-beam) deposition was employed to coat silicon substrates with the prepared material. Different heat treatment conditions were applied to the deposited films, followed by material and electrical property analyses. The investigation explored the impact of pre-sintering Ga2O3 at 950°C to transform it into a more stable [Formula: see text]-phase. For comparative purposes, some samples underwent annealing at 600°C in a nitrogen–hydrogen (95% N[Formula: see text] H2, abbreviated as N[Formula: see text]) mixed gas, which was used as a reduction atmosphere, to increase oxygen vacancies in the ZnF2-doped Ga2O3 thin films and consequently enhance their conductivity. The deposited ZnF2-doped Ga2O3 thin films initially exhibited an amorphous phase, with diffraction peaks appearing only after a 600°C annealing process. Pre-sintering Ga2O3 powder at 950°C promoted the emergence of the [Formula: see text]-phase, and the bandgap value increased after annealing. Measurements using B1500A revealed that sintering and annealing ZnF2-doped Ga2O3 thin films were essential steps to enhance their conductivity. X-ray photoelectron spectroscopy (XPS) further confirmed a significant correlation between the conductivity variation and the concentration of oxygen vacancies. Additionally, it was observed that the use of an N[Formula: see text] mixed gas further increased the presence of oxygen vacancies in the films. The results of this study provide an important method to make Ga2O3 thin films with conductivity, which can be utilized in the fabrication of Ga2O3 thin-film-based semiconductor devices in the future.

Morphological Characteristics of Propane–Hydrogen Diffusion Flame: Experiments and Correlations

ABSTRACT This study investigated the flame height and liftoff height of turbulent diffusion jet flames of the Propane–Hydrogen mixed gas. A series of experiments have been conducted to examine their flame height and liftoff height with different concentrations of propane and hydrogen. The experimental results show that the flame height decreases with the increase in hydrogen concentration. The accuracy of the Froude number for the prediction of flame height has been verified. The liftoff height is proportional to the propane flow rate, while it was inversely proportional to the hydrogen concentration due to the increased laminar flame speed. A theoretical model incorporating laminar flame speed, heat release rate, and fuel exit velocity has been obtained. These investigations are crucial for enhancing safety in hydrogen-enriched pipeline systems, which is helpful for the use of hydrogen in energy systems and global sustainability efforts.

Optimal Scheduling of Integrated Energy System Considering Hydrogen Blending Gas and Demand Response

In the context of carbon neutrality and carbon peaking, in order to achieve low carbon emissions and promote the efficient utilization of wind energy, hydrogen energy as an important energy carrier is proposed to mix hydrogen and natural gas to form hydrogen-enriched compressed natural gas (HCNG). It is also injected into the natural gas pipeline network to achieve the transmission and utilization of hydrogen energy. At the same time, the participation of demand response is considered, the load’s peak and trough periods are adjusted, and the large-scale consumption of renewable energy and the reduction in carbon emissions are achieved. First of all, a fine model of hydrogen production and hydrogen use equipment is established to analyze the impact of adding hydrogen mixing on the economy and the low-carbon property of the system. With green certificates and demand response, the utilization rate of hydrogen energy is improved to further explore the energy utilization rate and emission reduction capacity of the system. Secondly, on the basis of modeling, the optimal scheduling strategy is proposed with the sum of energy purchase cost, equipment operation cost, carbon emission cost, wind curtailment cost, and green certificate income as the lowest objective function. Considering the constraints such as hydrogen blending ratio and flexible load ratio of the pipeline network, a low-carbon economic scheduling model of hydrogen mixed natural gas was established. The model was linearized and solved by using MATLAB 2021a and CPLEX solver. By comparing different scenarios, the superiority of the model and the effectiveness of the strategy are verified.

Exploring the coupling mechanism between piston structure and turbulent jet ignition mode in hydrogen mixed natural gas rotary engines

The rapid development of electric vehicles has drawn extensive attention to using rotary engines as small-scale power generation devices. However, their wide application has been limited by drawbacks such as low combustion efficiency and high emissions. Therefore, to obtain rotary engines with high combustion efficiency and low emissions, this study explored the strengthening effect of natural gas/hydrogen hybrid fuel (NHHF) and Triangular Rotor Piston (TRP) structure on the combustion in the turbulent jet ignition rotary engine (TJI-RE) at different ignition advance angles (IAAs). Additionally, an experimental platform and a three-dimensional computational model for TJI-RE fueled by natural gas/hydrogen hybrid fuel (NHHF) were established in this study. The research results indicated that the TRP structure altered the combustion process by affecting the ignition area in the ignition stage and the turbulence kinetic energy during the combustion stroke. Furthermore, the SC-shaped cylinder exhibited the highest peak pressure for any fixed IAA. When the IAA was fixed at 30°CA (BTDC), the TJI-RE with the SC-shaped cylinder experienced a 12.12% increase in peak pressure and a 4.1% increase in indicated work compared to the FP-shaped cylinder. Additionally, the CO emission was reduced by 13.79%, while the NO emission showed a significant increase.

Development of deoxidation process for off-grade titanium sponge using magnesium metal with wire mesh strainer type of crucible

In this study, the deoxidation process for off-grade titanium (Ti) sponge using magnesium (Mg) metal with a wire mesh strainer type of crucible was developed. Ti hydride (TiH2) feedstock, which was prepared by hydrogenating off-grade Ti sponge, was deoxidized using Mg in a molten magnesium chloride–potassium chloride salt at 933 K under an argon and 20% hydrogen (H2) mixed gas atmosphere. After deoxidation, the residual Mg-containing salt was separated in situ from the crucible to investigate the feasibility of minimizing salt loss during the leaching and production of pure TiH2. The results showed that the presence of residual Mg-containing salt inside the crucible strongly influenced whether a mixture of Ti and TiH2 or pure TiH2 was produced. When the salt was not sufficiently separated, a mixture of Ti and TiH2 was obtained and its oxygen (O) concentration was 0.121 mass% under certain conditions. Meanwhile, pure TiH2 was obtained by increasing the H2 gas flow rate during deoxidation. Therefore, these results demonstrate that the decrease of O concentration to below 0.180 mass% and the minimal loss of the salt are feasible.

Techno assessment on hydrogen injected gas transportation based on integrated system simulation

The key to realizing the remote utilization of hydrogen through hydrogen mixed natural gas transportation lies in the establishment of a complete set of processes from hydrogen blending to pipeline transportation to hydrogen separation. However, the assessment and study of entire process of hydrogen blended gas transportation has rarely been considered. The present study comprehensively investigates the feasibility of natural gas-hydrogen mixture transportation in a high-pressure natural gas transmission system. Specifically, this work proposes a complete set of processes for the pipeline transportation of hydrogen-doped natural gas, including the hydrogen blending process, and the hydrogen separation process. The present study investigates the impacts of various adjustable parameters based on the created simulation object on hydrogen recovery, energy consumption, and turnover rate. The results show a maximum recovery of around 94% for the whole process and a minimum SEC of 1.1 kW h/Nm3 at conventional throughput.

Effect of porous materials on explosion characteristics of low ratio hydrogen/methane mixture in barrier tube

The effect of porous materials on the explosion characteristics of low ratio hydrogen/methane mixture in barrier tube was studied. The hydrogen ratio in the mixture is 0%–20%. The porosity of porous material is 20 PPI, 40 PPI and 60 PPI. The flame front structure, flame front velocity and overpressure data of the mixture were obtained by using high-speed camera and pressure sensor. The experimental results show that porous materials with the same porosity have similar quenching effects on pure methane explosion and low ratio hydrogen/methane premixed explosion. The greater the porosity, the better the quenching and decompression effect. The porous material with porosity of 60 PPI can meet its ability to attenuate flame front velocity and pressure wave even when adding low ratio hydrogen. The incremental effects of flame velocity and overpressure caused by the explosion of mixed gas with low ratio hydrogen under porous materials in the barrier tube are kept in a safe and controllable range. The research results provide a reference for the subsequent hydrogen mixed natural gas pipeline project.

Interchangeability of Hydrogen Injection in Zhejiang Natural Gas Pipelines as a Means to Achieve Carbon Neutrality

The blending of hydrogen gas into natural gas pipelines is an effective way of achieving the goal of carbon neutrality. Due to the large differences in the calorific values of natural gas from different sources, the calorific value of natural gas after mixing with hydrogen may not meet the quality requirements of natural gas, and the quality of natural gas entering long-distance natural gas and urban gas pipelines also has different requirements. Therefore, it is necessary to study the effect of multiple gas sources and different pipe network types on the differences in the calorific values of natural gas following hydrogen admixing. In this regard, this study aimed to determine the quality requirements and proportions of hydrogen-mixed gas in natural gas pipelines at home and abroad, and systematically determined the quality requirements for natural gas entering both long-distance natural gas and urban gas pipelines in combination with national standards. Taking the real calorific values of the gas supply cycle of seven atmospheric sources as an example, the calorific and Wobbe Index values for different hydrogen admixture ratios in a one-year cycle were calculated. The results showed that under the requirement of natural gas interchangeability, there were great differences in the proportions of natural gas mixed with hydrogen from different gas sources. When determining the proportion of hydrogen mixed with natural gas, both the factors of different gas sources and the factors of the gas supply cycle should be considered.

Correlated Electrical Conductivities to Chemical Configurations of Nitrogenated Nanocrystalline Diamond Films.

Diamond is one of the fascinating films appropriate for optoelectronic applications due to its wide bandgap (5.45 eV), high thermal conductivity (3320 W m−1·K−1), and strong chemical stability. In this report, we synthesized a type of diamond film called nanocrystalline diamond (NCD) by employing a physical vapor deposition method. The synthesis process was performed in different ratios of nitrogen and hydrogen mixed gas atmospheres to form nitrogen-doped (n-type) NCD films. A high-resolution scanning electron microscope confirmed the nature of the deposited films to contain diamond nanograins embedded into the amorphous carbon matrix. Sensitive spectroscopic investigations, including X-ray photoemission (XPS) and near-edge X-ray absorption fine structure (NEXAFS), were performed using a synchrotron beam. XPS spectra indicated that the nitrogen content in the film increased with the inflow ratio of nitrogen and hydrogen gas (IN/H). NEXAFS spectra revealed that the σ*C–C peak weakened, accompanied by a π*C=N peak strengthened with nitrogen doping. This structural modification after nitrogen doping was found to generate unpaired electrons with the formation of C–N and C=N bonding in grain boundaries (GBs). The measured electrical conductivity increased with nitrogen content, which confirms the suggestion of structural investigations that nitrogen-doping generated free electrons at the GBs of the NCD films.

Deoxidation of Off-Grade Titanium Sponge Using Magnesium Metal in Argon and Hydrogen Mixed Gas Atmosphere

Deoxidation of Off-Grade Titanium Sponge Using Magnesium Metal in Argon and Hydrogen Mixed Gas Atmosphere

Numerical Simulation of Combustion of Natural Gas Mixed with Hydrogen in Gas Boilers

Hydrogen mixed natural gas for combustion can improve combustion characteristics and reduce carbon emission, which has important engineering application value. A casing swirl burner model is adopted to numerically simulate and research the natural gas hydrogen mixing technology for combustion in gas boilers in this paper. Under the condition of conventional air atmosphere and constant air excess coefficient, the six working conditions for hydrogen mixing proportion into natural gas are designed to explore the combustion characteristics and the laws of pollution emissions. The temperature distributions, composition, and emission of combustion flue gas under various working conditions are analyzed and compared. Further investigation is also conducted for the variation laws of NOx and soot generation. The results show that when the boiler heating power is constant, hydrogen mixing will increase the combustion temperature, accelerate the combustion rate, reduce flue gas and CO2 emission, increase the generation of water vapor, and inhibit the generation of NOx and soot. Under the premise of meeting the fuel interchangeability, it is concluded that the optimal hydrogen mixing volume fraction of gas boilers is 24.7%.

Microbubble generation with rapid dissolution of ammonia (NH3)-hydrogen (H2) mixed gas fed from a nozzle into water

Because of their useful characteristics, microbubbles attracted much interest in industry and medicine. In this study, we developed a novel method of generating microbubbles through the chemical absorption of ammonia (NH3). By using an ultrahigh-speed camera, consecutive images of bubble formation were captured, and the microbubble generation mechanism was investigated. The effects of the gas flow rate and ammonia concentration in the liquid phase on the size of the microbubbles were examined. The hydrogen (H2) gas flow rate was found not to demonstrate a significant effect on the bubble diameter. The diameter of the microbubbles increased as the superficial velocity of the gas mixture (NH3 – H2) decreased.

Impedance spectroscopy analysis of n-type (nitrogen-doped) ultrananocrystalline diamond/p-type Si heterojunction diodes

Heterojunction diodes are constructed by growing n-type (nitrogen-doped) ultrananocrystalline diamond (UNCD)/hydrogenated amorphous carbon (a-C:H) composite films onto p-type Si substrates in nitrogen and hydrogen mixed-gases by coaxial arc plasma deposition. The fabricated heterojunctions are analyzed regarding their film morphology and electrical properties. The complex structure of UNCD/a-C:H films, which consists of nano-sized-sp3 diamond grains and sp2-grain boundaries (GBs), makes it difficult to separate their contribution to electrical conductivity of the films using conventional characterization methods. In this paper we characterize the n-type UNCD/p-type Si heterojunction diode by employing impedance spectroscopy method, which can isolate the differing components that contribute to the overall conductivity of the film. The impedance spectroscopy is measured in the frequency range of 100 Hz to 2 MHz, with AC small signal superimpose on DC bias voltage in the range of 0–1 V. The influence of the bias on UNCD grains and GBs contribution to resistance and capacitance of UNCD/a-C:H film and n-UNCD/p-Si heterojunction is investigated by equivalent circuit model using fitting of the impedance data. The results revealed that the electrical conductivity is mainly controlled by the GBs rather than the UNCD grains. Furthermore, the extracted value of dielectric constant of N-doped UNCD/a-C:H film is found to be comparable with that of microcrystalline diamond, which indicates the capacitance contribution in the device is mainly originated from the UNCD grains. This study demonstrates capability of impedance spectroscopy to provide an obvious separated contribution of sp3 and sp2 bonded carbons to the electrical conductivity in their coexistence materials.

High Machinability of Plasma-Nitrided HPM80 Dies at 673K by PCD-Tools for Hot Mold-Stamping

HPM80 had been utilized as one of the martensitic stainless steel mold and die substrates for stamping. In particular, HPM80 mold was often used as hot-stamping molds for oxide glasses and optical polymers to fabricate the optical elements and DOE (Diffractive Optical Elements) with the aid of NiP (Nickel Phosphate) and NiWP (Nickel-Tungsten Phosphate) coatings. These machinable amorphous coatings were indispensable to cut and finish the tailored micro textures for DOE since HPM80 was difficult or nearly impossible to be finished by using the PCD (Poly-Crystal Diamond)-chipped tools. However, those coatings were fragile above 473 K; the original HPM80 must be modified to be fine machinable even by the diamond-chipped and coated tools for fine finishing to mirror-polished die surfaces with far less damage to cutting tools. These HPM80 substrates were plasma nitrided at 673 K under the nitrogen and hydrogen mixed gas flow to form the high content nitrogen super-saturated layer. Precise machinability experiment was performed with the use of the PCD coated WC (Co) tools to investigate the machinability of these nitrogen supersaturated HPM80 substrates. Two-phase fine-grained layer with higher nitrogen solute content than 2 mass% was machined in the ductile mode with adaptively high quality to shaping and finishing the mold die surface for stamping. Through the hardness testing, this nitrogen super-saturated die surface had higher hardness than 1400 HV; it had sufficient durability for long-term stamping operations. Finally, the turning test was employed to demonstrate that this nitrogen supersaturated HPM80 layer with the thickness of 40μm was machined with high quality to form the mirror-polished surface.

고분자전해질연료전지 연료극의 이오노머 함량에 따른 CO 내피독 특성 연구

This paper reports the effects of the ionomer content on CO tolerance in a PtRu/C-based anode catalyst layer to understand the role of ionomer binders for CO poisoning of the electrocatalyst and to design a durable catalyst layer of MEA. Four different MEAs were prepared with ionomer contents of 20, 30, 40, and 50 wt. % for the anode and a fixed ionomer content of 30 wt. % for the cathode. The MEA performance was then tested under hydrogen and CO mixed gas feeding in a single cell to observe the CO tolerance of the prepared MEAs. The MEA performance was largely dependent on the anode ionomer content under both hydrogen and CO mixed gas conditions, revealing the best cell performance at a 40 wt. % ionomer content. The MEA also showed the lowest cell potential decay under CO mixed gas compared to hydrogen at a 40 wt. % ionomer content. The present study provides insights into the design of an anode catalyst layer structure, including optimization of the ionomer content, which can be critical to the design of a high performance MEA for reformed gas applications.

Surface oxidation effect on deuterium permeation in reduced activation ferritic/martensitic steel F82H for DEMO application

Fuel loss and environmental contamination by tritium permeation through structural materials are critical issues for the establishment of a fusion DEMO reactor. In this study, the effectivity of a chromium oxide layer formed on reduced activation ferritic/martensitic steel F82H as a tritium permeation barrier and its stability under simulated solid/liquid breeder blanket conditions have been investigated. A uniform 100-nm-thick chromium oxide layer was formed by heat treatment at 710 °C for 5 min in 50% argon-50% hydrogen mixed gas with the flow rate of 200 standard cubic centimeter per minute. After exposure to simulated solid breeder blanket conditions, an iron oxide layer and a spinel-type iron-chromium oxide layer formed. In the case of a liquid breeder blanket condition, the chromium oxide layer partly lost at 500 °C for 100 h. The chromium oxide-formed sample decreased deuterium permeation flux by a factor of up to 150. The permeation reduction efficiency deteriorated after exposure to a solid breeder blanket condition due to a change of the chromium oxide layer. However, the chromium oxide formation would play a role to reduce hydrogen isotope permeation even after reduction of the oxide layers.