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Typically, polymeric materials experience material degradation and damage over time in harsh environments. Improved understanding of the physical and chemical processes associated with possible dam...

The most influential factor for self-ignition of high-pressure hydrogen is known to be the strength of the shock. Thus, the self-ignition can be suppressed by weakening the shock strength, which is possible by reducing the area where the hydrogen is ejected in this study. To confirm the possibility of this method, experiments were done by controlling the burst pressure of up to 302 bar and the ratio of the opening area. The experimental results showed that the minimum burst pressure of self-ignition is increased exponentially as the opening area is reduced. This confirmed that reducing the opening area under the same burst pressure conditions has an effect on the suppression of self-ignition. However, it was also found that the minimum shock speed that causes self-ignition gradually decreases as the opening area becomes smaller, which results from an increasing in mixing. The CFD simulation results showed that the volume of the flammable region in the tube was increased and the hydrogen-air mixing efficiency also increased when the opening area became smaller. The results suggest that reduction of the opening area can suppress a self-ignition by weakening the shock strength, but it should be noted that an increase in mixing effect also occurs.

Both H2S and CO2 are removed from raw natural gas sources for product quality and safety reasons. If a cryogenic method is used for separation, the acid gas components (H2S + CO2) may be recovered ...

Hydrogen storage in activated carbons (ACs) has proven to be a realistic alternative to compression and liquefaction. Adsorption capacities up to 5.8 wt% have indeed been obtained. The amount of adsorbed hydrogen depends on the textural properties of ACs, such as specific surface area and total pore volume. The modified Dubinin-Astakhov (MDA) equation proved to be a good analytical tool for describing hydrogen adsorption in a wide range of pressures and temperatures and for several adsorbents. The parameters of this model have been found to be somehow related to the textural properties of the adsorbent. Thus, we applied this model to understand better hydrogen adsorption on ACs over a wide range of pressures in relation to the textural properties of the ACs. We applied the MDA equation to evaluate also the isosteric heat of hydrogen adsorption, which was found to be in the range of 5–9 kJ mol−1. We compared the results obtained by applying the MDA equation with those obtained by both the sorption isosteric method and the Sips equation. This allowed finding the temperature dependence of the isosteric heat of adsorption, as well as its variation with respect to the textural properties of the ACs.

Hydrogen is efficient and environmentally friendly, but the danger of self-ignition resulted from the leakage of high-pressure hydrogen cannot be ignored. In this work, the self-ignition of high-pressure hydrogen released through different conditions was studied. 700-mm-length tubes with different diameters were adopted in our experiments. It summarized the characteristics of shock waves' attenuation and evolution process of hydrogen jets in tubes. In addition, effects of the boundary layer on the leading shock waves, the contact surface, and expansion waves were discussed. Results indicate that minimum pressure when self-ignition occurs for 15-mm-diameter tube is similar to 10-mm-diameter. And they have closely velocity of shock waves. Simulations show that the greater the release pressure, the more ignition products of hydrogen. Higher release pressure and smaller diameter can create a thicker boundary layer in micro shock tubes, and the boundary layer can lead to a change in the velocity of shock waves’ structures.

A series of experiments were conducted to study the pressure and combustion characteristics of the high-pressure hydrogen during the occurrence of spontaneous ignition and the conversion from spontaneous ignition to a jet fire and explosion. Different initial conditions including release pressure (4–10 MPa), tube diameter (10/15 mm), and tube length (0.3/0.7/1.2/1.7/2.2/3 m) were tested. The variation of the pressure and flame signal inside and outside of the tube and the development of the jet flame were recorded. The experimental results revealed that the minimum ignition pressure required for self-ignition of hydrogen at different tube diameters decreased first and then increased with the extension of tubes. The minimum ignition pressure for tubes diameters of 10 mm and 15 mm is no more than 4 MPa and the length of the tubes is L = 1.7 m. The minimum release pressure required for spontaneous ignition of a tube D = 15 mm is always lower than that of a tube D = 10 mm at the same tube length. When the spontaneous ignition occurred, it did not absolutely trigger the jet fire. The transition from spontaneous ignition to a jet fire must go through the specific stages.

The limited quantities of oil reserves and the exhaust emissions from IC engines have become a threat to the existence of IC engines. One of the best solutions to the problem is the use of alternative fuels. Hydrogen is an alternative fuel that is called a fuel of the future. A disadvantage of hydrogen is its high combustion speed. Experimental results were used for the determination of inputs for numerical analysis. The numerical analysis is performed for a 3D model of the engine in order to determine the working parameters of the engine (pressure and temperature). The main goal of this study is to investigate a possibility of modifying the diesel engine so that it can run on hydrogen. It was found that in such an engine the greatest loads occur in the combustion chamber; thus, the vital parts of the engine are protected. Therefore, a mechanical analysis of the combustion chamber was performed (calculation of stresses and deformations). The obtained results are encouraging because they indicate that by applying the presented solution a much cheaper technology than the modern diesel engine systems is made possible.

A series of Cp*Ir (Cp* = pentamethylcyclopentadienyl anion) complexes with amino-functionalized ligands were developed for the production of high-pressure H2 via catalytic dehydrogenation of formic...

Steel layered high-pressure hydrogen vessel is one of different kinds of high-pressure vessel, which is invented in China and is widely equipped in hydrogen refueling stations for its good safety and storage functions. Many of these vessels are put into application these years, and it is nearly the time for these vessels to go through periodic inspection. However, there is no such a method for the periodic inspection especially on the butt weld connecting the double-layer head and the interface forging. To conquer the difficulties about the periodic inspection, a set of periodic inspection methods was first proposed in a lasted released Chinese group standard, in which the inner ultrasonic phased array is considered to be the most complicated detecting approach. To establish effective inspection parameters, simulations and experiments were conducted on the factors, including coupling, elements and aperture, focal law, scanning approaches and ultrasound field. Standard test block and contrast test block were designed and machined and tested, then a series of feasible parameters were determined. Thus, specific probe, wedge and instrument were manufactured, and the inspection on the actual vessel product was carried out. The results showed that the proposed ultrasonic method and its inspection parameters could meet the periodic inspection well. Finally, the periodic inspection methods were established and issued as a standard.

The hydrogen fuel cell vehicle industry has formed two major international standardization organizations, ISO, and International Electrotechnical Commission. ISO has formed a relatively mature evaluation system for electric vehicle performance indicators and test methods. However, in China, there are still deficiencies in the safety requirements and test evaluation methods in the field of hydrogen fuel vehicle components. The vehicle-mounted high-pressure hydrogen storage cylinder is a special equipment in Chinese current special equipment supervision and regulation system An important energy storage component of hydrogen fuel cells, it has a development history of more than 50 years in the world. However, Chinese national standard committee has not yet established a standard for type IV hydrogen storage cylinders, which had been used in Japan, U.S, and E.U. In this paper, the United Nations’ automotive high-pressure hydrogen storage cylinder standard ISO 19881:2018 and my Chinese standard GB/T 35544-2017, had been compared and analyzed, especially the specific differences in the manufacturing and inspection. China has been preparing to manufacture the type IV hydrogen cylinder standard nowadays. So it is very important to learn from foreign advanced experience, The purpose of this article is provide relevant instructs for manufacture, inspection and test, to formulate China’s vehicle-mounted hydrogen storage cylinders, and improves the conversion and application of standards.

As important equipment in the entire hydrogen industry chain, composite hydrogen storage cylinders for transportation have developed rapidly in recent years. The fire test is used to verify the explosion resistance of gas cylinders under specified fire conditions. Compared to steel gas cylinder, composite gas cylinder is more dangerous in the fire condition. The wound layer, as the main pressure-bearing structure of the composite hydrogen storage cylinder, is inflammable. In the case of fire, the mechanical properties of the cylinder will degrade quickly due to the high temperature. If the gas inside the cylinder cannot be discharged in time, the cylinder explosion will occur. Currently, some relevant standards or standard drafts have been drawn up by the international organizations, which are useful for formulating Chinese standard for hydrogen storage cylinders for transportation. The applicable scope of the standards was discussed in this paper, such as composite cylinder type, working pressure, nominal volume and design life, etc. The fire test methods of composite gas cylinders in various standards were compared and analyzed, such as experiment method, cylinder placement method, cylinder filling requirements, fuel selection, fire source setting, temperature measurement requirements, and qualified indicators, etc. Finally, the challenges for development of composite hydrogen storage cylinders and compressed hydrogen storage systems in China were proposed.

High pressure Type 2 hoop-wrapped, thick-walled vessels are commonly used at hydrogen refueling stations. Vessels installed at stations circa 2010 are now reaching their design cycle limit and are being retired, which is the motivation for exploring life extension opportunities. The number of design cycles is based on a fatigue life calculation using a fracture mechanics assessment according to ASME Section VIII, Division 3, which assumes each cycle is the full pressure range identified in the User’s Design Specification for a given pressure vessel design; however, assessment of service data reveals that the actual pressure cycles are more conservative than the design specification. A case study was performed in which in-service pressure cycles were used to re-calculate the design cycles. It was found that less than 1% of the allowable crack extension was consumed when crack growth was assessed using in-service design pressures compared to the original design fatigue life from 2010. Additionally, design cycles were assessed on the 2010 era vessels based on design curves from the recently approved ASME Code Case 2938, which were based on fatigue crack growth rate relationships over a broader range of ΔK. Using the Code Case 2938 design curves yielded nearly 2.7 times greater design cycles compared to the 2010 vessel original design basis. The benefits of using in-service pressure cycles to assess the design life and the implications of using the design curves in Code Case 2938 are discussed in detail in this paper.

A simple screening technique of hydrogen embrittlement (HE) of steels for hydrogen energy facilities using an in-situ small-punch (SP) test method under external hydrogen condition has been established. Using this method, we investigated the HE behaviors of API X70 steel welds under test conditions mimicking pipeline operating environments. The HE sensitivity at each region of the base metal, heat-affected zone, and weld metal of the steel weld was examined qualitatively and quantitatively and compared to one another. Under 8 MPa H2 gas, the welds showed pronounced HE: the HE behaviors induced were similar across all tested regions. This shows that the in-situ SP test is effective for screening HE susceptibility of pipeline steel welds in high-pressure hydrogen environments.

In this short comment we present a reproducibility study for our recent manuscript “A simple constrained machine learning model for predicting high-pressure-hydrogen-compressor materials” by Hattrick-Simpers, et al., Mol. Syst. Des. Eng., 2018, 3, 509” using a suite of open source materials data science tools. The principal goal of this study is to provide the interested reader the ability to reproduce our previous machine learning model with minimal effort and then perform predictions upon the holdout set used in that manuscript. In transcribing our model from the Java-based Magpie/Weka framework to the Python-based Matminer/scikit-learn framework we noticed an unexpected discrepancy in the predictions between the two platforms. To compare the performance of nominally equivalent random forest regression models across these two platforms, we trained and evaluated 50 replicate models for each platform using random 90% subsets of the full hydride training set for each replicate. The Magpie/Weka models showed somewhat higher predicted mean absolute error (5.6 ± 0.4) than the Matminer/scikit-learn models (4.2 ± 0.4) on the holdout set, although the validation statistics were within error of one another. It is beyond the scope of this comment to fully analyze the ultimate source of the variance in these predictions, but we speculate that some contribution results from differences in how Magpie treats duplicate compositions in the training set and/or differences in RF implementation between Weka and scikit-learn.

A novel process involving roasting with additives, water leaching, and vanadium precipitation by high-pressure hydrogen reduction is proposed to selectively extract vanadium from vanadium-bearing ferro-phosphorus. The optimum conditions of roasting and leaching are obtained as follows: roasting temperature of 850 °C, Na2CO3 dosage of 30 wt%, CaCO3 dosage of 30 wt%, roasting time of 1 h, leaching time of 2 h and a leaching liquid–solid ratio of 1 mL/g. A V2O3 product having a purity of 99.92% is precipitated from the leaching solution by a high-pressure hydrogen reduction. The total recovered vanadium is up to 92.3%. X-ray diffraction (XRD) analysis of the raw ore, roasted ore, and leaching residue shows that the additive of Na2CO3 during roasting can react with the vanadium-bearing compounds and transform it into water-soluble NaVO3, while the additive of CaCO3 can solidify phosphorus-bearing and chromium-bearing compounds into non-water-soluble phosphates of Ca3(PO4)2 and Cr3(PO4)2. Moreover, the iron-bearing compounds are converted into non-water-soluble Fe2O3 and Na3Fe2(PO4)3. Thus, vanadium can be selectively extracted through the subsequent water leaching and high pressure hydrogen reduction process. Compared with the traditional process, this process is more efficient and environmentally friendly owing to the high recovery of vanadium, the non-used roasting additive of sodium chloride and the adopted eco-friendly vanadium precipitation method.

We investigate the effects of high-pressure hydrogen annealing (HPHA) on W/ferroelectric Al:HfO2/interface layer (IL)/Si stacks. With HPHA, degradation in remnant polarization is observed in the pristine state due to ferroelectric domain pinning. However, after wake-up, a comparable remnant polarization is observed by domain de-pinning. In addition, HPHA improves the quality current and low interface trap density are maintained up to 107 cycles. As a result, the endurance improves up to 109 cycles and a stable retention is achieved up to 104 s at 85 °C. These results show that the HPHA can be a crucial process for ferroelectric HfO2-based transistor applications.

The aim of this paper is to study the effect of the displacement rate on the fracture toughness under internal hydrogen of two different structural steels grades used in energy applications. To this end, steel specimens were pre-charged with gaseous hydrogen at 19.5 MPa and 450 °C for 21 h and then fracture toughness tests were carried out in air at room temperature. Permeation experiments were also conducted to obtain the hydrogen diffusion coefficients of the steels. It was observed that the lower the displacement rate and the higher the steel yield strength, the stronger the reduction in fracture toughness due to the presence of internal hydrogen. A change in the fracture micromechanism was also detected. All these findings were justified in terms of hydrogen diffusion and accumulation in the crack front region in the different steel specimens.

This paper introduces a new hydrogen refueling system with a micro-scale hydrogen turbo-expander that enables us to replace a conventional low temperature refrigerator. From the process simulation of hydrogen refueling to the tank of a typical Fuel Cell Vehicle (FCV), the system is thermodynamically verified to be capable of refueling 5 kg-H2 within 3 minutes by the direct expansion in the micro-scale hydrogen turbo-expander. For the realization of this new concept, a process design approach of a high pressure hydrogen refueling system with the micro-scale hydrogen turbo-expander is described. In this process design, a turbine-compressor type is adopted to the micro-scale hydrogen turbo-expander unit, and an extracted power from the turbine side is consumed as a compressor power which is equipped on the opposite side of the turbine rotor. As a consequence of the thermodynamic analysis and simulation for the proposed system including the turbo-expander with adiabatic efficiency around65 %, it reveals that the new system provides some significant advantages compared with the conventional process. From a feasible investigation of this system, several advantageous features such as 1) high energy conservation, 2) compactness, 3) initial cost and operation cost, and, 4) system expandability (modification for shorter time refueling) are also described when it is compared with the existing system.

In the study presented here, an apparatus that correctly measured pressure–composition isotherms (PCi) at high pressures (up to 100 MPa) and temperatures (up to 200 °C) was developed. The PCi characteristics of a vanadium–titanium–chromium alloy at high pressure and temperature were examined with the apparatus to develop a metal hydride (MH) compressor. It was revealed that it is possible to use a 40 V 20Ti 40Cr (at%) alloy with a heat source below 200 °C for hydrogen compression in the approximate range of 2.1–30.0 MPa. The compressed content reached approximately 1.8 wt%, which is almost the same as the reversible hydrogen capacity at 20 °C.

This paper is devoted to investigating the effects of obstacles inside the tube on the shock wave propagation and spontaneous ignition during high-pressure hydrogen release. The length of the obstacles area is 38 mm, which includes seven metal ring obstacles and six metal spacers. The hydrogen burst pressure varies from 2 to 8 MPa. The results show that the existence of obstacles in the tube has no significant influence on minimum burst pressure required for spontaneous ignition in our experiments, even though a reflected shock wave is formed from obstacle. When initial ignition has been induced in the tube before the obstacles, however, the appearance of the reflected shock wave can promote combustion and enhances the flame intensity. Combustion pressure wave originated from self-ignition is observed in the tube, which also increases flame intensity. Three possible spontaneous ignition mechanisms for the tube with obstacles are discussed. And it is found that although the strength of the leading shock wave decreases after passing through obstacles, the flame velocity relatives to the tube wall inside the tube increases significantly. This may be because large amount of hydrogen/air mixture, which produced by the turbulent mixing due to the presence of the obstacles, accelerates combustion in the tube. Nevertheless, the obstacles could not change the flame propagation characteristics outside the tube, such as flame morphologies and flame propagation velocity.

Hydrogen is regarded as an alternative energy carrier in the next decades and high-pressure hydrogen storage is treated as the best option. However, unexpected spontaneous ignition would occur during high-pressure hydrogen sudden release, which induces a severe safety issue. For improving the safety application of hydrogen, an experimental investigation has been conducted. Different diameter ring gaskets are employed to change the opening ratio χ. Pressure transducers and light sensors are used to record the pressure variation and possible light signals inside the tube, respectively. It is found that the burst disk is unable to fully open during high-pressure hydrogen release when χ

This paper investigates the effects of hydrogen additions on spontaneous ignition of high-pressure hydrogen released into hydrogen-air mixture. Hydrogen and air are premixed with different volume concentrations (0%, 5%, 10%, 15% and 20% H2) in the tube before high-pressure hydrogen is suddenly released. Pressure transducers are employed to detect the shock waves, estimate the mean shock wave speed and record the shock wave overpressure. Light sensors are used to determine the occurrence of high-pressure hydrogen spontaneous ignition in the tube. A high-speed camera is used to capture the flame propagation behavior outside the tube. It is found that only 5% hydrogen addition could decrease the minimum storage pressure required for spontaneous ignition from 4.37 MPa to 2.78 MPa significantly. When 10% or 15% hydrogen is added to the air, the minimum storage pressure decreases to 2.81 MPa and 1.85 MPa, respectively. When hydrogen addition increases to 20%, the spontaneous ignition even takes place at burst pressure as low as 1.79 MPa inside the straight tube.