Hydrogen Flow Research Articles

Hydrogen-modulation method for wafer-scale few-layer single-crystal graphene growth

Single-crystal few-layer graphene films have potential applications in microelectronic and optoelectronic devices. Considerable efforts have been taken to prepare large-area bilayer graphene through chemical vapor deposition, but the growth of uniform graphene films with increased layers remains challenging. Herein, a hydrogen-modulation method for growing wafer-scale few-layer single-crystal graphene through chemical vapor deposition was proposed. By controlling the hydrogen flow rate at different stages, the dissolution amount and segregation process of carbon atoms in a CuNi substrate can be regulated separately. The hydrogen-modulation method fully exploits the effect of the dissolution–segregation mechanism, and the number of graphene layers can be controlled by modulating the hydrogen flow rate. Through the proposed method, the coverages of bilayer and trilayer graphene can reach more than 99% and 95%, respectively. The stacking and uniformity of few-layer graphene were evaluated by Raman and microstructure characterization, and bilayer and trilayer graphene were confirmed as AB and ABA stacks, respectively. Transmission line test structure and field effect transistor were prepared to verify the electrical properties of bilayer graphene. Results show that the square resistance of bilayer graphene is significantly lower than that of single-layer graphene, and it can also achieve high on-state current on field effect transistor.

Cross flow and distribution characteristics in automobile polymer electrolyte membrane fuel cells: A three-dimensional full-scale modeling study

Ultrahigh power density is of primary importance to next-generation polymer electrolyte membrane fuel cell (PEMFC) for commercialization, which demands an in-depth insight into the intricate multi-physics transports, particularly for large-size PEMFCs in automobile application. In this study, a three-dimensional two-phase model is extended to study an automobile fuel cell with the active area of 366.6 cm2, including full morphologies of metallic bipolar plate, flow field, and distribution zones for hydrogen, air and coolant flow. It is found that the cross flow inside membrane electrode assembly under the rib between two adjacent channels promoted by the distribution zone can effectively mitigate local oxygen starvation and water flooding, increasing PEMFC performance at high current density, in comparison with conventional single-channel or no-dot-matrix models. Theoretical analysis indicates that the dot matrix distribution zone induces a larger pressure gradient and hence the cross flow than the commonly-used channel & rib distribution zones. Additionally, the counter-flow configuration has a higher cell performance and more uniform current density than the co-flow one due to internal humidification. When the internal humidification effect is weak, for example, in anode/cathode gas co-flow configuration, coolant flow direction becomes more important for the temperature profile and prevent severe dehydration.

An experimental investigation of hydrogen-enriched and nanoparticle blended waste cooking biodiesel on diesel engine

The hazardous effect of the pollution of fossil fuels has brought the necessity of shifting conventional energy sources to renewable and clean ones. In this study, the effect of hydrogen addition and CeO2 nanoparticle addition in waste cooking palm biodiesel on a CRDI engine is evaluated. The dosage of the nanoparticle is fixed at 75 ppm and a hydrogen flow rate of 10 L/min is selected for the engine operations. The crystalline structure of the nanoparticles is determined by XRD analysis. Results showed that on the addition of both H2 and CeO2 in a B20 biodiesel blend (80% diesel and 20% biodiesel) the performance, emission, and combustion parameters of the diesel engine improved compared to neat diesel. The brake thermal efficiency was improved by 3.53% and brake fuel consumption was reduced by 16.12% in comparison to diesel at 90% loading condition. The addition of both nanoparticles and hydrogen in the biodiesel blend lowered the emissions of CO by 30%, and HC and smoke by 50% and 42% respectively. However, NOx increased by 11% as compared to diesel. A 6% higher HRR values and 8% higher in-cylinder pressure were obtained while using hydrogen and CeO2 nanoparticle blended biodiesel. This blend also shows the lowest ignition delay period at full load condition which results in more engine power and efficiency. This experimental study has helped pave the way for the use of hydrogen-enriched and nanoparticle-blended biodiesel in place of fossil fuel for the applications of diesel engines.

The Direction of the Flow of Interstellar Neutral H Based on Photometric Observations from SOHO/SWAN

Interstellar neutral hydrogen flows into the heliosphere as a mixture of the primary and secondary populations from two somewhat different directions due to splitting occurring in the magnetized outer heliosheath. The direction of the inflow of interstellar neutral H observed in the inner heliosphere, confronted with that of the unperturbed flow of interstellar neutral helium, is important for understanding the geometry of the distortion of the heliosphere from axial symmetry. It is also needed for facilitating remote-sensing studies of the solar wind structure based on observations of the helioglow, such as those presently performed by SOHO/SWAN, and in the near future by IMAP/GLOWS. In the past, the only means to measure the direction of the flow of interstellar hydrogen were spectroscopic observations of the helioglow. Here, we propose a new method to determine this parameter based on a long series of photometric observations of the helioglow. The method is based on purely geometric considerations and does not depend on any model and absolute calibration of the measurements. We apply this method to sky maps of the helioglow available from the SOHO/SWAN experiment and derive the mean longitude of the flow of interstellar hydrogen. We obtain 253.°1 ± 2.°8, which is in perfect agreement with the previously obtained results based on spectroscopic observations.

Experimental evaluation of a 1 kW proton exchange membrane fuel cell with resistive, DC and AC loads

In this communication, an experimental investigation is carried out on a PEM (Proton Exchange Membrane) fuel cell. A small-scale standalone PEM fuel cell system of 1 kW capacity is demonstrated in the present study. The fuel cell is connected to the charge controller, and the charge controller is further connected to the DC and AC loads to study the fuel cell characteristics. A battery bank backup is also provided to account for the stable power output from the fuel cell. The purpose of the study is to determine the fuel cell's performance when operated with resistive, AC, and DC loads (home appliances within the rated power range). The effect of hydrogen flow rates on the power output is also presented in this paper. The DC and AC loads are connected to the fuel cell setup to study the characteristics of the fuel cell. From the study, it can be observed that the performance of the fuel cell is better at higher flow rates of hydrogen. The experimental results showed that the maximum power obtained was 986.8 W at a hydrogen supply rate of 15 LPM. The maximum fuel cell efficiency was found to be 44% at the flow rate of 8 LPM. The charge controller efficiency reported for DC and AC load connections is 94.97% and 96.98%, respectively. The inverter efficiency was observed to increase with the current value, with the maximum value reaching around 98.86%.

The combined effect of EGR and hydrogen addition on a Syzygium cumini (jamun) liquid biofuel engine

Rapid depletion of fossil fuels required the development of alternate and sustainable fuel sources that could replace conventional fuel while having no negative environmental impact. Combining hydrogen induction with biodiesel ensures strict emission standards and lowers energy consumption compared to conventional fuels. In this study, the performance, emissions, and combustion of a CI engine for Syzygiumcumini (B20) were assessed and compared to diesel fuel while using a fixed amount of hydrogen flow rate (6L/m). Throughout the experiment, an exhaust gas recirculation (EGR) technology of 10% and 20% and a constant engine speed of 1500 rpm at varying engine load circumstances were used. When hydrogen is added to B20, it decrease the emissions of carbon monoxide (CO), unburned hydrocarbons (UHC), brake thermal efficiency (BTE), and brake specific energy consumption (BSEC). At maximum load, the use of the EGR system decreased the exhaust gas temperature (EGT) by 13.4% and nitrogen oxide (NOX) emission by 25%, but it had a negative impact on BTE, BSEC, as well as other emission parameters including CO and UHC. Therefore, using hydrogen in dual fuel mode in a CI engine enhances performance and lowers exhaust emissions, while using the EGR approach reduces NOX emissions.

Effect of hydrogen blending on the combustion performance, emission, and cycle-to-cycle variation characteristics of a single-cylinder GDI spark ignition dual-fuel engine

The effect of hydrogen addition on combustion, performance, emission and cyclic variation under different hydrogen flow rates (2, 5, 8, 11, and 14 LPM) were investigated based on a SI engine with hydrogen port induction and gasoline direct injection. The in-cylinder pressure increases by 52.04% with an 8LPM of hydrogen flow rate. The rate of pressure rise and heat release from the hydrogen-gasoline mixture combustion are more concentrated and 95.53% increase in the engine torque. For the specified hydrogen flow rate, brake specific energy consumption was reduced by 92.27% and brake thermal efficiency increased by 25%. Moreover, CO emission was improved after hydrogen addition under all operating conditions. CO2 and NOX emissions were continuously increased with hydrogen addition. The cyclic variation was increased with the increase in the hydrogen flow rate and reduced with the increase in gasoline injection quantity.

Assessing the pressure losses during hydrogen transport in the current natural gas infrastructure using numerical modelling

The UK government aims to transition its modern natural gas infrastructure towards Hydrogen by 2035. Since hydrogen is a much lighter gas than methane, it is important to understand the change in parameters when transporting it. While most modern work in this topic looks at the transport of hydrogen-methane mixtures, this work focuses on pure hydrogen transport. The aim of this paper is to highlight the change in gas distribution parameters when natural gas is replaced by hydrogen in the existing infrastructure. This study uses analytical models and computational models to compare the flow of hydrogen and methane in a pipe based on pressure loss. The Darcy-Weisbach and Colebrook-White equations were used for the analytical models, and the k- ε model was used for the computational approach. The variables considered in the comparison were the pipe material (X52 Steel and MDPE) and pipe diameters (0.01m–1m). It was observed that hydrogen had to be transported 250–270% the velocity of methane to replicate flow for a fixed length of pipe. Furthermore, it was noted that MDPE pipes has 2–31% lower pressure losses compared to X52 steel for all diameters when transporting hydrogen at a high velocity. Lastly, it was noted that the analytical model and computational model were in agreement with 1–5% error in their findings.

Penggunaan bahan bakar terbarukan (biodiesel-hydrogen) pada mesin Diesel Dual Fuel untuk mendukung Energy Transition di Indonesia

Increasing demand for oil as a fuel and declining production in refineries led to a nationwide fuel oil shortage. Hence compelling academics to develop answers, renewable energy is one of the proposed options. Compression ignition machines utilize renewable fuels such as biodiesel, crude palm oil (CPO), and hydrogen gas. Using biodiesel without modifying the engine can result in decreased thermal efficiency and increased smoke emissions. The addition of modest volumes of hydrogen gas can enhance the performance of diesel engines. The purpose of this investigation is to investigate the performance and emissions of diesel dual-fuel engines. In this investigation, a one-cylinder diesel engine with direct injection was operated at a constant 2000rpm with a 50 percent load. Flow variations of 2.5, 5, 7.5, and 10 liters per minute of hydrogen. Compared to biodiesel fuel, the results of this study indicate that a 10LPM hydrogen flow can boost thermal efficiency by 29.85% and a 7.5LPM hydrogen flow can increase power by 0.78 %. Moreover, the use of hydrogen gas reduces exhaust pollutants. Reduced HC, CO, and CO2 emissions by 26ppm, 0.01%, and 2.60%, respectively, for a 10LPM hydrogen flow.

Hydroconversion of methyl palmitate over Ni-phosphide catalysts on SAPO-11 and ZSM-5 composite supports

Zeolite materials (SAPO-11 or ZSM-5) were used to prepare modified Al2O3 supports by mixing with Al oxide hydroxide, peptization with HNO3 and subsequent extrusion. The obtained Al2O3-SAPO-11 and Al2O3-ZSM-5 (with 30 wt% zeolite content) were impregnated by solutions containing Ni and P precursors: phosphate (A), phosphite (I), and hypophosphite (H). Ni-phosphide catalysts were prepared by temperature-programmed reduction in hydrogen flow and characterized by ICP-AES chemical analysis, low-temperature N2 physisorption, H2-TPR, NH3-TPD, XRD, 27Al MAS NMR, XPS. The catalysts were tested in methyl palmitate (MP) hydroconversion (HC, i.e. hydrodeoxygenation (HDO) + hydroisomerization/hydrocracking). 100% MP conversion was achieved over all catalysts (flow reactor at 340 °C, 2.0 MPa, 5.3 h−1). For Ni2P/Al2O3-SAPO-11 catalysts the overall yield of iso-alkanes (iso-C15 and iso-C16) increased in the following order of precursors: A < I < H. The highest yield of iso-alkanes was 21% over Ni2P/Al2O3-SAPO-11 H catalyst. Ni2P/Al2O3-ZSM-5 samples possessed high cracking activity. Alkanes from MP HDO as well as the solvent (n-dodecane) were almost completely transformed to C6–C9 alkanes at 340 °C. Decreasing temperature (290, 270 °C) did not result in significant yield of iso-alkanes over Ni2P/Al2O3-ZSM-5 catalysts.

Nucleation of cubic boron nitride on boron-doped diamond via plasma enhanced chemical vapor deposition

Cubic boron nitride (c-BN), with a small 1.4% lattice mismatch with diamond, presents a heterostructure with multiple opportunities for electronic device applications. However, the formation of c-BN/diamond heterostructures has been limited by the tendency to form hexagonal BN at the interface. In this study, c-BN has been deposited on free standing polycrystalline and single crystal boron-doped diamond substrates via electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-PECVD), employing fluorine chemistry. In situ x-ray photoelectron spectroscopy (XPS) is used to characterize the nucleation and growth of boron nitride (BN) films as a function of hydrogen gas flow rates during deposition. The PECVD growth rate of BN was found to increase with increased hydrogen gas flow. In the absence of hydrogen gas flow, the BN layer was reduced in thickness or etched. The XPS results show that an excess of hydrogen gas significantly increases the percent of sp2 bonding, characteristic of hexagonal BN (h-BN), particularly during initial layer growth. Reducing the hydrogen flow, such that hydrogen gas is the limiting reactant, minimizes the sp2 bonding during the nucleation of BN. TEM results indicate the partial coverage of the diamond with thin epitaxial islands of c-BN. The limited hydrogen reaction is found to be a favorable growth environment for c-BN on boron-doped diamond.

Hydrogen flow rate control in a liquid organic hydrogen carrier batch reactor for hydrogen storage

Liquid Organic Hydrogen Carriers (LOHCs) feature a highly variable rate of hydrogen release if held at constant pressure and temperature, but in real-life applications hydrogen release must be controlled to match end-user demand. The aim of this paper is to provide an overall assessment of LOHC systems’ controllability, within a general framework regardless of the specific application field. Hydrogen discharge can be controlled through the reactor pressure and temperature; thus, a PI controller is introduced acting on three control variables independently: discharge pressure; thermal fluid inlet temperature; thermal fluid mass flow rate. A quantile analysis is performed on the uncontrolled hydrogen release: practical values of the energy-to-power ratios for LOHC systems are 2–6 h. A normalised release time is introduced to assess the efficiency of the control system. Temperature control leads to the best results, with an efficiency higher than 90% for the entire load range, while pressure control leads to satisfactory performance only at low loads. The mass flow rate control is the least effective, with efficiencies always below 80%. Sensitivity analysis highlights the temperature control strategy as the best fit to enhance controllability across the whole power range. Pressure control presents a more variable trend.

Polyoxometalates as highly efficient adsorbents for ciprofloxacin removal: The key role of oxygen vacancies

In this study, various silver phosphomolybdates (x-y-z-AgPMo) with oxygen vacancies were successfully prepared through H2 calcination and subsequent chemical precipitation and used for the adsorption of ciprofloxacin (CIP) in water. The microstructures of x-y-z-AgPMo were analyzed by a series of characterization methods. The effects of calcination time, calcination temperature, hydrogen flow rate, and external adsorption conditions on the adsorption performance were investigated. The results showed that the adsorption performance of 1–0.1–250-AgPMo toward CIP could reach 91% within 20 min with a maximum adsorption capacity of 45.5 mg∙g − 1, which was about 1.7 times as that of silver phosphomolybdate (Y-AgPMo) without H2 calcination. The improved adsorption performance of 1–0.1–250-AgPMo was mainly attributed to the presence of oxygen vacancies, which induced more negative surface charges and larger specific surface area in 1–0.1–250-AgPMo. This work provided an excellent adsorbent for CIP removal and forcefully confirmed the important role of oxygen vacancies in the adsorption process.

The Effect Of Acid Strength Of Bronsted Acid Site On The Ability Of The Catalyst To Break The Carbon Chain Bonds Of 1-Octadekenes Into Alkanes And Short Chain Alkenes As A Substitute For Fossil Fuels

Research has been carried out on the strength of acids on their ability to break carbon chain bonds. The preparation of the zeolite catalyst includes soaking the zeolite in distilled water for 24 hours, followed by calcination and oxidation, then followed by reduction. Further acid treatment with 6 M HCl. Then followed by washing with H2O until neutral pH (pH = 7), then dried in an oven with a temperature of 105 oC, then after becoming a zeolite catalyst used in the cracking reaction of 1-octadekenes into alkanes and short chain alkenes.The results obtained are as follows for the type of zeolite catalyst with code Z having a very low acidity level of 3.15 mmol NH3/mgZeolite, then the zeolite has been modified by a calcination process for 24 hours given the code ZCA which shows a moderate acidity level of 5, 76 mmol NH3/mg Zeolite, then the catalyst with the code ZCAO is zeolite which has been calcified and oxidized and shows a yield of 9.54 mmol NH3/mg Zeolite. Catalytic hydrocracking of 1-octadecene with ZCAO catalyst at a variation of the hydrogen flow rate of 20 mL/minute and a temperature of 450 oC resulted in alkanes and alkenes C12 which was 15.29% maximum, followed by a hydrogen flow rate of 10 mL/minute at temperatures of 500 and 400 oC.

Numerical simulation of heat transfer characteristics of supercritical liquid hydrogen through triangular U-tube in moderator

In this study, the heat transfer characteristics of supercritical hydrogen in triangular U-tubes with different radius were investigated. In order to compare the heat transfer capacity of triangular U-tubes, and to explore the heat transfer characteristics of supercritical liquid hydrogen inside them, a three-dimensional numerical simulation was carried out by Fluent. The unstructured grid and RNG k-ε turbulence model were used to encrypt the grid. Meanwhile, the grid independence and the effectiveness of the turbulence model are verified. The Tw, Tf and Nu along the triangular U-tube at different q and Re were compared. The result shows that Tw, Tf and Nu increase with the increase of q and Re. The change of Re was found to be largest for Nu. The effect of secondary flow on Nu was similar to the entrance effect of upstream straight pipe, and the effect of secondary flow on Nu was slightly larger than the entrance effect. This work provides a useful technical guidance for thermal design and thermal management of neutron source and target station, as well as novel ideas for flow and heat transfer of supercritical liquid hydrogen in U-tube.

Multiple-objective optimization on ammonia decomposition using membrane reactor

Ammonia plays a key role in the renewable hydrogen economy nowadays, thus, the efficiency of ammonia decomposition for hydrogen production becomes an important research topic. In this study, a numerical model was built to study the performance of ammonia decomposition using a membrane reactor and Ru/Al2O3 catalyst under various operating conditions such as feed NH3 temperature and volume flow rate as well as retentate side pressure. The reactor performance was characterized by ammonia conversion, hydrogen recovery, and recovered hydrogen flow rate. Pre-exponential factor and activation energy of ammonia reaction rate were obtained by equilibrium conversion and two-step parametric sweeping. It was found that ammonia conversion can be increased by about 33% compared to a conventional fixed-bed reactor under the same operating conditions. H2 recovery can be enhanced when the reactant inlet temperature and the pressure difference between the retentate and permeate sides increase. The increase in feed NH3 flow rate (gas hourly space velocity, GHSV) decreased the ammonia conversion and H2 recovery. An optimum GHSV that results in a maximum recovered H2 flow rate can be found. Finally, optimum operation conditions for maximizing the hydrogen recovery and recovered hydrogen flow rate were analyzed using the multi-objective Non-dominated sorting genetic algorithm-II (NSGA-II). It was found that maximum H2 recovery with a value of 79.7% can be obtained under the conditions of inlet temperature of 336 °C, GHSV of 900 h−1, and retentate side pressure of 9.9875 bar. The maximum recovered hydrogen flow rate with a value of 9.55×10−14(mol·s−1) can be obtained under the conditions of an inlet temperature of 394 °C, GHSV of 1315 h−1, and retentate side pressure of 9.9879 bar.

Effect of salinity, mineralogy, and organic materials in hydrogen wetting and its implications for underground hydrogen storage (UHS)

Hydrogen is a green energy carrier, which appears to reshape the current energy supply chain. To develop a full-scale hydrogen supply chain, underground hydrogen storage has been proposed as a key method. However, one of the key hurdles in UHS is the fluid-rock interactions or hydrogen wetting. The interfacial reactions govern hydrogen wetting in underground reservoirs and thus determine the hydrogen flow and govern the amount of hydrogen trapping in porous media. Although the hydrogen wetting has been gaining attention, how the hydrogen wetting behaves in complicated underground circumstances remains in the shadow.To understand the nano-scale character of hydrogen wetting, a series of molecular dynamics (MD) simulations were performed to analyse the hydrogen distribution on kaolinite surface in function of salinity, mineralogy, and organic materials. We computed density distribution and the radial distribution function (RDF, g(r)) of each species. The results show that salinity can dramatically affect hydrogen distribution on the siloxane surface while negligible effects can be observed on aluminol (gibbsite) surfaces of kaolinite. Furthermore, the hydrogen distribution can be notably shaped by organic materials. Organic materials with acid functional group (–COOH) can generate a more hydrogen wetting surface than base functional group (–NH). This investigation reveals the governing mechanics of hydrogen-brine-kaolinite reactions at molecular scale, unravels the effects of hydrogen-brine-kaolinite reactions in hydrogen wetting and thus provides a paradigm to screen candidate sites for the UHS.

A Novel Online Diagnosis Method for Tubular Solid Oxide Fuel Cells Using Total Harmonic Distortion Analysis

Fast and accurate online prognostic technology is urgently needed for the long-term and stable operation of solid oxide fuel cell (SOFCs). Total harmonic distortion analysis (THDA) is a potential candidate that obtains the dynamic information of an electrochemical system by analyzing high-order signals and has been successfully utilized in PEMFC fault diagnosis. In this study, the THDA method is utilized in a tubular SOFC under fuel and air starvation conditions at different hydrogen and air flow rates. The total harmonic distortion spectra are obtained in the frequency range of 0.1~100 Hz. The effects of different excitation current amplitudes on the results accuracy are further investigated. As a consequence, the excitation amplitude range, frequencies with high sensitivity and appropriate threshold are chosen to diagnose different faults efficiently.

Influence of Process Parameters on SOEC Performance

Solid oxide electrolysis cells (SOECs) are highlighted as promising power-to-gas (P2G) devices that can provide a reliable supply of hydrogen gas to store renewable energy. Despite the potential of SOECs, there are many challenges facing their commercialization. In this work, the influence of process parameters and fuel electrode optimization on initial SOEC performance (500 hours) is investigated. Electrolysis experiments were performed with both GDC (gadolinia doped ceria)-infiltrated and uninfiltrated Ni-YSZ (yttria stabilized zirconia) fuel electrodes under various hydrogen flow rates with different ratios of H2-H2O and current densities. All cells marginally improve in performance initially, then undergo a brief period of rapid performance degradation followed by stabilization. The observed three stages of cell performance, in terms of length of time and rate of change, are found to be dependent on the type of fuel electrode and experimental process parameters used.

The use of a gravity-assisted-storage-extraction protocol for hydrogen storage in saline aquifers

The hydrogen gas produced through the electrolysis of water using excess energy could serve as a prospective source to meet peak energy demand during certain seasons. Because of the large storage capacity and ease of accessibility, saline aquifers are a highly desirable geological storage option for hydrogen. Common challenges encountered in aquifer-based hydrogen storage systems during production include the notable lateral migration of the hydrogen plume caused by the high mobility of hydrogen, as well as the occurrence of gravity override due to the low density of hydrogen and the subsequent production of significant amounts of water during withdrawal. The proposed approach for mitigating water coning and increasing hydrogen production is a gravity-assisted-storage-extraction (GASE) protocol. This involves injecting the working hydrogen gas from the lower region of the formation and extracting it from the top region using a horizontal well. The proposed process capitalizes on the gravitational effects that facilitate the vertical migration of hydrogen, creating a gas-enriched zone within the aquifer. This results in improved hydrogen production as the lateral flow of water and hydrogen is restricted. The implementation of GASE protocol is demonstrated by numerical simulation experiment based on an actual hydrogen storage site at San Pedro belt. The results of simulations conducted on the numerical model indicate that if the GASE protocol is implemented, it has the potential to recover over 93% of the working gas, which is a 20–30% improvement compared to the data that has been previously published. The major limitation of the GASE protocol is the potential capital cost increments due to the drilling and completion of the horizontal wells, which makes it more suitable for a hydrogen storage project with long-term and sustainable hydrogen supplies.