Combined Effect Of Hydrogen Research Articles

The combined effect of hydrogen and aging conditions on the cyclic behavior of a precipitation-hardened nickel-base superalloy

The combined effect of hydrogen and aging conditions on the cyclic behavior of a precipitation-hardened nickel-base superalloy

Mechanism of influence of water mist in a closed vessel on the explosion overpressure and flame propagation characteristics of magnesium dust

The primary purpose of this paper is to deeply investigate the impact of water mist on the explosive characteristics of magnesium dust and to broaden the inerting and suppression strategies for magnesium dust explosions. The explosion characteristics and flame propagation behaviors of magnesium dust/water mist mixtures were examined in a 16.2-L visualized closed vessel. The explosion products were further analyzed using SEM and XRD. The results indicate that with the addition of water mist, the explosivity of low-concentration magnesium dust (≤600 g/m3) increases. The explosive strength of three higher concentrations of magnesium dust (800 g/m3, 1200 g/m3, 1600 g/m3) notably decreases, with the Pmax dropping by 69.86%, 54.08%, and 46.22% respectively compared to pure magnesium dust. The leading edge of the preheat zone exhibits red radiation, the fluctuation range of the instantaneous flame propagation speed decreases, and cubic particles appear in the explosion products. These changes are mainly attributed to the hydrogen produced in the explosion of the magnesium dust/water mist mixture. Under the combined effects of hydrogen and steam, the preheat zone significantly expands. Moreover, as the concentration of hydrogen increases, its presence weakens the suppressing effect of the water mist, manifested by the evident slowing of the average flame speed, the maximum flame speed, and the rate of decrease in explosive strength. The suppression of magnesium dust explosions by water mist mainly relies on physical actions such as heat absorption, blocking thermal radiation, and diluting oxidizer concentration.

H2/NH3 Addition Effects on Flame Characteristics and Soot Formation in Ethylene Inverse Diffusion Flame

Zero-carbon alternative fuels such as hydrogen and ammonia are gaining popularity. Blending these fuels with hydrocarbons is an intermediate approach to mitigate soot and carbon dioxide production. Recent studies have concentrated their attention to the effects of ammonia and hydrogen on the soot production of hydrocarbon fuels. It is still necessary to completely comprehend how this influence is dependent on the type of fuel and flame configuration. In this work, the effect of hydrogen and ammonia addition on soot production in ethylene laminar inverse diffusion flames (IDF) was numerically examined for the first time. The thermal, chemical, and combined effects of hydrogen and ammonia were assessed by fictitious species. The experimental results from the literature were used to validate the temperature and soot volume fraction profiles. Results indicated that the flame temperature and the production of radicals are promoted chemically by hydrogen addition but inhibited under the thermal effect of ammonia. The principal source of the reduction in OH-represented flame height, soot volume fraction, average diameter, and primary particle number density in the IDF is the thermal effect of additives, and hydrogen addition performs better than ammonia. The major and intermediate species, the aromatic hydrocarbons, and the soot formation or oxidation reaction rates are decreased mainly by the hydrogen and ammonia thermal effect while increased moderately by the chemical effect. Therein, the reduction in soot generation is mainly due to the polycyclic aromatic hydrocarbon condensation rate being slowed down by additives. The inhibition is attributed to the thermal effect of additions, and hydrogen behaves better than ammonia.

Combined effect of hydrogen and with Julifora biodiesel blend (JFB20) on the combustion, performance and emission characteristics of a direct-injection diesel engine

The effect of hydrogen (H2) gas share to the Julifora biodiesel blended fuel (JFB20) on the performance, combustion, and emission parameters of a CI engine was performed in this paper. Julifora biodiesel was prepared using 2-stage transesterification process and their properties were evaluated according to ASTM methods. Engine tests were carried out on a single cylinder diesel engine using hydrogen (4 lpm and 8 lpm) and JFB20 fuel samples and their results were compared with diesel. The hydrogen (H2) gas was introduced into the inlet manifold of a diesel engine at a volume flow rates of 4 lpm and 8 lpm, respectively. From the experimental results, BTE for the H2 (hydrogen) mixed with JFB20 fuel was improved by 18.4%, and BSFC was reduced by 13.6%. The induction of H2 gas along with JFB20 fuel increased the heat release rate (HRR) and cylinder pressure (CP) compared to the JFB20 fuel. The Properties of MFB, Exhaust gas temperature and ignition delay for all fuel samples were also determined. Although the NOx emissions were significantly improved, the tailpipe emissions such as HC, CO and smoke opacity were decreased. It is concluded that hydrogen gas along with biodiesel are viable alternative fuels for diesel engines. A qualitative study was performed to establish the Engine performance, combustion and emission magnitude fuelled with combination of Hydrogen and with Julifora biodiesel blend (JFB20).

Combined effects of hydrogen and TiO2 nanoparticle additive on terebinth oil biodiesel operated diesel engine

Efforts to reduce the dependency on fossil-based fuels have intensely been researched by scientists recently. Therefore, in internal combustion engines, the usability of various alternative fuels is still being evaluated. The present study experimentally focused on the illumination of the combined impacts of nanoparticle additives and hydrogen fuel on the performance and emission characteristics of a compression ignition engine. For this purpose, diesel fuel and combinations of diesel fuel, terebinth oil biodiesel, titanium dioxides nanoparticle, and hydrogen were utilized. Reduced engine performance caused by biodiesel was compensated with the use of nanoparticles. Further improvement was also observed with hydrogen addition. Emission results showed that carbon monoxide (CO) emission values can be reduced with biodiesel, nanoparticle additive, and hydrogen since they all have positive effects to enhance combustion quality and avoid incomplete combustion. On the other hand, oxides of nitrogen (NOx) emission was increased due to a rise in cylinder temperature with the use of biodiesel, nanoparticle, and hydrogen.

A coupled CFD model for an accurate and fast prediction of the unsteady operation process of a proton exchange membrane fuel cell

A proton exchange membrane (PEM) fuel cell is one of the highly efficient hydrogen utilization devices. However, due to the complex physical and chemical processes in fuel cells, developing a mathematical model of the PEM fuel cell is challenging. In this study, a new coupled model based on the computational fluid dynamics method and a 1D model is proposed for the accurate and fast prediction of PEM fuel cell performance. First of all, the proposed model is validated using the literature data. It is then applied to simulate the distribution and evolution of the current density, hydrogen and oxygen mass fraction, and membrane water content in catalyst layer (CL). Results show that the increase in the current density is attributed to the increase in the consumption rate of hydrogen and oxygen and the increase in the membrane water content. In addition, the stabilized supply of the oxygen in cathode and the membrane water content in the anode CL are critical for the improvement of the fuel cell performance. For the cases studied in this research, when the output voltage decreases from 0.6 V to 0.3 V, the current density increases from 5738.1 A/m2 to 15171.2 A/m2. The average oxygen mass fraction in the cathode CL and the average membrane water content in the anode CL decreased by 42.3 % and 9.6 %, respectively. In addition, when the fuel cell starts up at 0.6 V, the concentration of hydrogen and oxygen drops gradually decreases along the flow direction of the CL, while the membrane water content rapidly increases initially, and then increases slowly, with the turning point around at approximately 2.2 × 10-3 m. Under the combined effect of hydrogen and oxygen concentration, as well as the membrane water content, the current density first increases and then decreases, with the maximum value exceeding 6500 A/m2.

Emissions Reduction in an Automotive Compression Ignition Engine using Hydrogen and Exhaust Gas Recirculation

ABSTRACT This paper deals with the experimental investigation of an automotive compression ignition (CI) engine under dual fuel mode (hydrogen-diesel) with exhaust gas recirculation (EGR). The engine was operated under different speeds at 16 Nm (maximum torque). Smoke, CO, and HC emissions decreased drastically with hydrogen. However, maximum hydrogen energy share (HES) is limited to 56% at 2000 rpm and 63% at 2400 rpm due to combustion with knock and NOx emission raised drastically. EGR technique was used to enhance the knock limited HES and reduce NOx emission. The maximum HES without knock is extended to 68% with 20% EGR (2000 rpm). NOx emission decreased to near-zero level. Brake thermal efficiency increased. CO and HC emissions decreased significantly. However, smoke increased but still lower than base diesel. The combined effect of hydrogen and EGR could reduce the emissions, energy efficiency improvement, and extend the maximum HES limit.

Combined effects of temperature and of high hydrogen and oxygen contents on the mechanical behavior of a zirconium alloy upon cooling from the βZr phase temperature range

• Mechanical behavior of (prior-)β Zr upon cooling. • Hydrogen and oxygen contents up to 3000 wppm and 0.9 wt% respectively. • Tests at temperatures between 700 °C and 30 °C during cooling from 1000 °C to 1200 °C. • Strong synergic effects of hydrogen and oxygen contents and loading temperature. • Relationships proposed to describe the material mechanical behavior. During hypothetical loss-of-coolant accidents (LOCA), zirconium-based nuclear fuel claddings can be exposed to high temperatures in the β Zr phase domain and absorb substantial amounts of hydrogen (up to about 3000 weight ppm) and oxygen (up to about 1 weight %). This paper provides novel data about the combined effects of high hydrogen and oxygen contents on the mechanical behavior of the (prior-)β Zr phase, as a function of temperature, upon cooling from the β Zr phase temperature range. A protocol was developed to homogeneously charge Zircaloy-4 cladding tubes at different hydrogen contents, up to 3200 weight ppm, and oxygen contents, between 0.13 and 0.9 wt%. Tensile tests were then performed at various temperatures between 700 °C and 30 °C upon cooling from the β Zr domain. The results show that the mechanical behavior strongly depends on the testing temperature and the hydrogen and oxygen contents. Relationships are proposed to describe the macroscopic ductile-to-brittle transition and the mechanical behavior of the material as a function of temperature, hydrogen and oxygen contents. The predictions based on these relationships are compared to selected data from the literature obtained on claddings oxidized at high temperature, including results from semi-integral LOCA tests. Also, it is shown that considering the combined effects of hydrogen and oxygen is necessary to interpret the material's mechanical behavior, particularly the embrittlement of claddings subjected to LOCA-relevant secondary hydriding.

Crack propagation rate of hydrogen-induced cracking in high sulfur-containing pipelines

Hydrogen-Induced Cracking (HIC) is one of the main failure models of pipeline steels that are utilized to gather pipeline networks and long-distance pipeline networks within high sulfur-containing gas fields. This phenomenon is mainly caused by the combined effects of hydrogen and stress after the hydrogen atoms or ions in the transmission medium entering into the steel. This can produce a stress corrosion effect on the materials and thus lead to a decrease of fracture ductile or degradation of other properties. In this paper, a micro-fracture shear band fractal model of HIC has been proposed and the mechanism of HIC has been studied. Both the shape of the fracture process zone and the step length of hydrogen-induced crack propagation were integrated, thus building expressions that describe the fractal rate of each step of HIC. Based on this, the fractal crack propagation rates of HIC in pipelines 16 Mn and 20 steel were calculated under certain working conditions and H2S concentrations. Our study adds valuable insight into the life prediction of pipeline failure under the HIC environment.

Effect of applied potential on stress corrosion cracking behavior of X80 steel in alkaline soil simulated solution with sulfate-reducing bacteria

In this study, the effect of applied potential on stress corrosion behavior of X80 pipeline steel in Dagang soil containing sulfate-reducing bacteria was comprehensively analyzed by means of the AC impedance technique and slow strain-rate tensile tests and scanning electron microscope observation of fracture morphology. The results indicate that, with decreasing electrode potential, the corrosion degree of the sample first decreases and then increases, and the stress corrosion cracking sensitivity exhibits a certain rule. Under the Ecorr and a potential of −725 mV(vs.CSE), the stress corrosion cracking mechanism of metal is anodic dissolution. The synergistic effect of sulfate-reducing bacteria and stress results in the initiation and propagation of cracks on the surface of the metal electrode. At −1275 mV(vs.CSE), the mechanism of stress corrosion cracking is hydrogen-induced cracking. The sulfate-reducing bacteria exacerbates the cathodic hydrogen evolution at this potential. Under the combined effects of hydrogen and stress, stress corrosion cracking behavior occurs in metals.

The combined effects of hydrogen and aging condition on the deformation and fracture behavior of a precipitation-hardened nickel-base superalloy

The effect of hydrogen (H) on the deformation behavior of Monel K-500 in various isothermal heat treatment conditions (non-aged, under-aged, peak-aged, and over-aged) was assessed via uniaxial mechanical testing. H-charged and non-charged specimens were strained to failure to facilitate a comparison of ductility, fracture surface morphology, strength, and work hardening behavior. For all examined heat treatment conditions, H charging leads to a significant reduction in ductility, which is accompanied by a consistent change in fracture surface morphology from ductile microvoid coalescence to brittle intergranular fracture. While H charging led to a systematic enhancement in the yield strength of all heat treatments, the three age-hardened conditions exhibited a more than 2-fold increase relative to the non-aged heat treatment. This suggests that H modifies the dislocation–precipitate interactions, which also manifest themselves through changes in work hardening metrics related to the dislocation storage and recovery rates. In particular, the H-charged peak-aged specimen exhibited a significant increase in initial hardening (dislocation storage) rate relative to the H-charged under-aged specimen. Transmission electron microscopy of these samples revealed the onset of widespread dislocation looping in the H-charged peak-aged sample, in addition to the planar slip bands characteristic of the non-charged condition. This result suggests that hydrogen induces the particle shearing-to-looping transition at smaller particle sizes. Possible mechanistic explanations for this observed behavior are presented.

Separate and combined effects of hydrogen and nitrogen additions on diesel engine combustion

Shortage of non-renewable energies, increase in fossil fuel prices and stricter emissions regulations due to high NOx and soot emissions emitted from combustion of heavy diesel fuels by compression ignition engines, has led consumers to use renewable, cleaner and cheap fuels. An investigation has been computationally carried out to explore the influences of hydrogen and nitrogen addition on engine performance such as indicated power and indicated specific energy consumption and amounts of pollutant emissions like NOx, soot, and CO in an HSDI (High-Speed Direct Injection) diesel engine. Optimized sub-models, such as turbulence model, spray model, combustion model and emissions models have selected for the main CFD code. Meanwhile, HF (Homogeneity Factor) has been employed for analysing in-cylinder air-fuel mixing quality under various addition conditions. After validations with experimental data of diesel combustion with a single addition of 4% hydrogen and combined addition of 6% hydrogen + 6% nitrogen, investigations have conducted for modeling mixing and combustion processes with additions of hydrogen and nitrogen by ranges of 2–8% (v/v). Results showed that a single addition of H2 increased NOx and decreased CO and soot and improved ISEC and IP. In the case of nitrogen addition, NOx decreased, both CO and soot emission increased and ISEC and IP considerably ruined compared with NDC operation. Based on the results obtained for simultaneous addition of N2 (8% of v/v) and H2 (8% of v/v), NOx and soot emissions decreased by 11.5% and 42.5% respectively, and ISEC and IP improved 25.7% and 13%, respectively. But amount of CO emissions had an increase of 52% should be paid necessary attention as a main disadvantage.

Atomistic studies of hydrogen effects on grain boundary structure and deformation response in FCC Ni

The effect of hydrogen in the grain boundary on the mechanical response of random microstructures was studied by using atomistic simulation techniques and model interatomic potentials. The model interatomic potentials mimic properties of interstitial H in fcc materials within the limitations of empirical force laws. We report fully three-dimensional atomistic molecular dynamics studies of the mechanical response of identical samples with and without H in the grain boundaries. H content changes the structure of the grain boundaries and plays a critical role in the emission of dislocations from the grain boundaries under an applied stress. For lower deformation levels, the presence of H increased the yield strength of the samples, whereas for higher deformation levels, it increased dislocation emission from grain boundary sources, resulting in an increase in the number of dislocations in pile-ups at the grain boundaries. Increasing the H content resulted in increasingly larger cracks being formed on the grain boundaries, consistent with decreased grain boundary cohesion. Our results support a picture of hydrogen embrittlement resulting from the combined effects of hydrogen on plasticity as well as grain boundary decohesion.

Qualitative and Quantitative Analysis of Lipid Classes in Fish Oils by Thin‐Layer Chromatography with an Iatroscan Flame Ionization Detector (TLC‐FID) and Liquid Chromatography with an Evaporative Light Scattering Detector (LC‐ELSD)

Combined effects of hydrogen and air flow rates on the peak response of selected neutral lipid classes (triacylglycerol, diacylglycerol, monoacylglycerol, free fatty acids, and ethyl esters) were studied to optimize and calibrate the Iatroscan Mk‐6s Chromarod system for the qualitative and quantitative analysis of lipid classes by thin‐layer chromatography (TLC) with flame ionization detection in fish oil during the transesterification process. Air flow rate of 2 L/min, hydrogen flow rate of 150–160 mL/min, and scan rate of 30 s/rod were found to be the optimum conditions. All samples were also analyzed by high performance liquid chromatography (HPLC) with evaporative light scattering detection. Quantitative results obtained by TLC with the flame ionization detection method were comparable to those obtained from HPLC with evaporative light scattering detection.

Effect of hydrogen on ductility of stable austenitic steel

Abstract Straining in hydrogen at a pressure of2 bar, or in air after thermal charging in high pressure hydrogen, produces only minimal loss in ductility at particular strain rates for as received or solution treated samples of a stable austenitic stainless steel. However, cathodically charging at 80°C introduces a significant embrittlement that is associated with theformation during straining of brittle surface cracks whose depth increases with charging time. The latter effect is related to the depth of penetration of hydrogen and the transformation to martensite that is induced by the combined effect of hydrogen and stress. Removal of the hydrogen and the associated α martensite by subsequent vacuum annealing produces recovery of ductility. The application of a sensitising treatment before charging or testing in hydrogen gives results that are not significantly different.

Combined effects of hydrogen and magnetization on the tensile properties in 2.25Cr1Mo steel

Since the 1950's, there has been much effort to examine the influence of magnetic field on mechanical properties of ferromagnetic metals and alloys. It has been well-documented that lattice defects can influence the magnetic behavior, for example, the change of magnetic susceptibility of steels during plastic deformation or fatigue loading, or the Barkhausen effect, which is caused by the interaction of moving domain walls with lattice imperfection. The present paper is one part of the work to investigate the influences of magnetic field and hydrogen charging on mechanical properties of iron and its alloys. The 2.25Cr-1Mo (ASTM A387) steel was chosen because hydrogen embrittlement of this steel had been widely investigated and the response to hydrogen charging was well-known. So the possible influence of magnetic field could be separated.

Studies on the fractal dimension of a fracture surface formed by slow stable crack propagation

Fractal dimensions of different parts of a fracture surface formed by slow stable crack propagation, induced by the combined effect of hydrogen and static bending moment, were determined using the method of fracture profile analysis. The material used for this investigation was 30CrMnSiNi2A steel having the chemical composition (wt.%): 0.26% C, 1.02% Cr, 1.23% Mn, 1.08% Si, 1.56% Ni, 0.029% P and 0.007% S. The results showed that the fractal dimension increases with increasing transgranular fracture which increases as the crack propagates. This means that the increase of the fractal dimension responds to the increase of the energy needed to form the fracture surface, and in the authors' case the process of forming a fracture surface by slow stable crack propagation is one of increasing fractal dimension of the fracture surface; when the fractal dimension reaches a critical value, the crack propagation becomes unstable.

Influence of austenitizing temperature on stress corrosion in 4330m steel—The role of impurity segregation in stress corrosion cracking of high strength steel

Measurements of the threshold stress intensity for stress corrosion cracking (SCC), KISCC, and crack growth rate,da/dt, in distilled water were made, respectively, on bolt-loaded WOL and precracked three-point-bending specimens of a 4330M steel. A significant improvement of resistance to SCC was obtained by increasing quenching temperature and it is due to a reduction of segregated impurities of P and S at prior austenite grain boundaries. Intergranular cracking tendency increases with inter-granular concentration of impurities and the fracture mode changes from intergranular separation along prior austenite grain boundaries to transgranular quasi-cleavage as the segregated impurity becomes low enough. The combined effects of hydrogen and intergranular impurities on reducing intergranular cohesion and the time for approaching the critical concentration of hydrogen are dis-cussed in terms of a dynamic model which takes into account the accumulation of hydrogen ahead of a moving microcrack.

Solute segregation and hydrogen-induced intergranular fracture in an alloy steel

Hydrogen-induced intergranular fracture of laboratory heats of a 3.5 Ni-1.7 Cr steel doped with P, Sn, or Sb and having a yield strength of 840 MPa and a prior austenite grain size of 120 μm has been compared with that of an undoped steel at a hydrogen pressure of 0.17 MPa (1.68 atm). The intergranular concentrations of the impurities were controlled by varying the time of aging at 480 °C. Cracking of the undoped steel tested in hydrogen occurred along martensitic lath boundaries at high stresses. However, the susceptibility of the doped steels to hydrogen-induced intergranular cracking increased precipitously with impurity concentration. The susceptibility was measured in terms of the threshold stress intensity Kthfor the first detectable crack extension in precracked specimens and in terms of the threshold stress σth for microcrack formation in notched specimens. A comparison between the intergranular strength in hydrogen and in air revealed that absorption of hydrogen produced a profound intergranular weakening when the grain boundaries contained even a small amount of a segregated embrittling element. The relative embrittling potencies of P, Sn, and Sb in hydrogen gas were the same as in air. The combined effects of hydrogen and the impurities in reducing intergranular cohesion are discussed in terms of a newly proposed dynamic model which takes into account the accumulation of hydrogen ahead of a moving microcrack.