Effect Of Gas Pressure Research Articles

Enhanced strength-ductility synergy in a Ni–W–Co–Ta medium-heavy alloy via cryogenic supersonic fine particle bombardment

This study explores the influence of cryogenic supersonic fine particle bombardment (CSFPB) on a Ni–W–Co–Ta medium heavy alloy (MHA), and focus on the effect of gas pressure and impact time on the surface integrity, microstructural evolution, and mechanical properties of the MHA. CSFPB treatment creates a gradient structure, including surface layer with nanograins down to 9.0 nm due to severe plastic deformation, subsurface layer with high density dislocation structures and deformation twins due to weakened impact energy, and undeformed matrix. A key advantage of CSFPB is seen to be the cryogenic environment, which promotes superior surface integrity by reduced roughness. As the impact duration and gas pressure increase, the depth of deformation layer, surface hardness and strength of the MHA progressively rise. The optimal combination of strength and ductility is achieved at a gas pressure of 1.0 MPa for a duration of 90 s. This setting results in a maximum ultimate tensile strength of 1351 MPa and yield strength 796 MPa, with uncompromising elongation. However, excessively long treatment durations or high gas pressures can lead to the formation of surface microcracks, ultimately reducing the MHA's strength. Therefore, CSFPB offers the benefit of improved surface integrity through the cryogenic environment while maintaining a desirable balance between enhanced strength and ductility.

Autoignition of premixed hydrogen/air mixtures with uniformly dispersed carbon particles

The autoignition of a stoichiometric hydrogen/air mixture laden with uniformly distributed coal char particles is simulated with the Eulerian-Lagrangian approach under isochoric conditions. A zero-dimensional model is adopted to assess the effects of gas temperature, pressure, particle diameter, and concentration on ignition dynamics. Increasing the initial temperature reduces the ignition time and maximum heat release rate of the homogeneous reactions, while the parameters for particle reactions stabilize after reaching a critical temperature. Initial pressure exhibits a non-monotonic influence on gas phase ignition, with higher pressures promoting particle autoignition. An increase in particle diameter decreases the ignition time for the homogeneous reaction, approaching that of particle-free conditions. Meanwhile, particle ignition time first decreases and then linearly increases. Increasing particle concentration reduces the interphase disparities of ignition times, while the two-phase ignition times rapidly rise after exceeding the critical concentration. Moreover, pre-ignition temperature equilibrium (PTE) significantly impacts the ignition parameters and processes. PTE results in a minimal ignition time disparity between the gas and particles, with coal char particles markedly influencing hydrogen ignition. Failure to reach PTE leads to significant two-phase ignition time differences, with negligible impact from the solid phase on gas phase ignition. The particle effect ratio, δ, is introduced to evaluate these effects. Notably, the evolution variations in ignition time and heat release rate are determined by the existence of the PTE under corresponding initial conditions. The findings of this study are crucial for developing strategies to mitigate explosion hazards and enhance the performance of detonation propulsion systems using hybrid fuels.

Modelling of a continuous sorption-enhanced methanation process in an adiabatic packed-bed reactor system

The present study investigates a sorption-enhanced methanation process and successive solid regeneration stages using a dual-function catalyst containing nickel as a catalyst and zeolite 13X for water removal. An adiabatic packed bed, modelled by a dynamical and heterogeneous model, has been considered, and a five-stage sequence describes the sorption-enhanced methanation and successive solid regeneration. First, methanation occurs with in-situ water removal; then, the catalyst drying using a pressure and temperature swing approach implemented by blowdown, purge, cooling, and pressurisation stages. In adiabatic operation, heat management is crucial; on the other hand, the heat produced can be efficiently used to dry the zeolite. Process intensification is pursued by addressing the effect of gas inlet temperature, pressure, and GHSV on system performance. Achieving an average purity of 99 % of the methane for pressures greater than 2 bar is possible for long-time operation, with productivity averaging 0.8 mol/(kgads min) at the highest gas hourly space velocity investigated.

Modeling of high-pressure transient gas-liquid flow in M-shaped jumpers of subsea gas production systems

Two-phase flow with low liquid loads is common in high-pressure natural gas offshore gathering and transmission pipelines. During gas production slowdowns or shutdowns, an accumulation of liquid in the lower sections of subsea pipelines may occur. This phenomenon is observed in jumpers that connect different units in deep-water subsea gas production facilities. The displacement of the accumulated liquid during production ramp-up induces temporal variations in pressure drop across the jumper and forces on its elbows, resulting in flow-induced vibrations (FIV) that pose potential risks to the structural integrity of the jumper. To bridge the gap between laboratory experiments and field conditions, transient 3D numerical simulations were conducted using the OpenFOAM software. These simulations facilitated the development of a mechanistic model to elucidate the factors contributing to increased pressure and forces during the liquid purging process. The study examined the influence of gas pressure level, pipe diameter, initially accumulated liquid amount, liquid properties, and gas mass flow rate on the transient pressure drop and the forces acting on the jumper's elbows. The critical gas production rate required for complete liquid removal of the accumulated liquid was determined, and scaling rules were proposed to predict the effects of gas pressure and pipe diameter on this critical value. The dominant frequencies of pressure and force fluctuations were identified, with low-pressure systems exhibiting frequencies associated with two-phase flow phenomena and high-pressure systems showing frequencies attributed to acoustic waves.

Numerical simulation of hydrate flow in gas-dominated undulating pipes considering nucleation and deposition behaviors

The distribution and deposition of hydrates in deep-water gas transportation pipelines are crucial for safety. Current simulations of hydrate flow based on the population balance model have predominantly focused on water-dominant systems and neglect the nucleation and deposition of hydrates. By establishing a model for a hydrate flow in a gas-dominant system that considers the uneven distribution of the liquid film on the wall, hydrate nucleation, gas–liquid mass transfer, particle adhesion and aggregation, and dynamic deposition, we achieved simulation of the entire process of hydrate formation, aggregation, breakage, and deposition. Simulations in undulating pipelines were carried out to investigate the effects of gas velocity, liquid injection, pressure, and pipeline structure on distribution patterns. The results showed increasing the gas velocity enhanced the dispersion of particles and increasing the pressure increased the rate of aggregation. The formation of blocky aggregates posed significant risk in the rear section of the lower-bend pipe.

Effects of cushion gas pressure and operating parameters on the capacity of hydrogen storage in lined rock caverns (LRC)

Hydrogen storage in lined rock cavern (LRC) provides versatile site selection, safety, and stability, making it a crucial option. In this study, a thermodynamic mathematical model was established to describe hydrogen storage in LRC. This model is based on the principles of mass, momentum, and energy conservation while accounting for the authentic compressibility of hydrogen. The thermodynamic fluctuations throughout the seasonal cycle in LRC were computed using the COMSOL Multiphysics software. The results indicate that when the hydrogen storage reaches the operating pressure, the lower the cushion gas pressure, the greater the hydrogen injection amount, and the higher the utilization rate of storage capacity. With a cushion gas pressure of 3 MPa, the storage capacity utilization rate exceeds that at 15 MPa by 41 %. The injection rate of 0.5 kg/s results in a temperature increase of 12 °C compared to 0.27 kg/s, indicating twice the temperature rise at the 0.27 kg/s injection rate. An increase in injection temperature corresponds to higher temperature within the hydrogen storage cavern upon completion of gas injection, thereby reducing the time needed for gas injection to reach maximum operating pressure. A lower initial cavern temperature results in a longer time for hydrogen storage to reach maximum operating pressure.

Experimental study on effect of cyclic gas pressure on mechanical and acoustic emission characteristics of salt rock

The utilization of renewable resources like wind and solar energy has led the Chinese government to prioritize the development of energy storage systems, garnering significant attention for salt cavern compressed air energy storage (CAES) technology. The stability of the surrounding rock in salt caverns is critical for ensuring sustained operation. By conducting mechanical tests on salt rock under fixed axial and confining pressures with cyclic gas pressure, the mechanical behavior and acoustic emission characteristics of salt rock under the influence of gas pressure were analyzed. The mechanical and acoustic emission characteristics of salt rock were analyzed. The results indicated that the triaxial compressive strength of salt rock negatively correlated with constant gas pressure. Both radial and axial strains demonstrated distinct phases: deceleration, steady-state, and acceleration. The steady-state creep rate of axial strain and the lower limit of cyclic gas pressure can be fitted in the form of an exponential function. The number of cyclic air pressure cycles decreased as the lower limit of cyclic air pressure increased. Acoustic emission count was used to define the damage variables, clarifying the formation and accumulation of salt rock damage in each stage, distinguishing the growth rates of damage during loading and unloading. It was observed that the higher the lower limit of cyclic air pressure, the quicker the damage accumulated with cycling. During the test, the absolute energy of the acoustic emissions from the salt rock conformed to a damped power-law distribution. The power-law distribution index γ of the absolute energy of acoustic emissions shifted with the number of cyclic air pressure cycles, and the sudden decrease of the distribution index γ plays a certain early warning role for the failure of salt rock.

Improving plasma uniformity in the inductively coupled plasma by external magnetic field

To enhance etching efficiency and uniformity in process production, in this work, a two-dimensional fluid model was used to study the modulation effect of an external magnetic field on the argon–oxygen inductively coupled plasma (ICP). The study found that as the magnetic coil current increases, the electron density changes from center-high to uniform to edge-high distribution. The best plasma uniformity degree is 94%, obtained at a magnetic coil current of 10 A, which represents a 39% improvement over the unmagnetized ICP. The electric field reversal occurs during the transition from weak magnetization to strong magnetization. The electron temperature shows a single-peak to dual-peak to single-peak distribution during this period. In addition, we also found that gas pressure and oxygen ratio also impact magnetized plasma, where the effect of gas pressure on magnetized plasma is more significant than that of oxygen ratio. The results show that introducing an external magnetic field can significantly improve the plasma density and radial uniformity. This finding has contributed to enhancing plasma etching uniformity and optimizing etching processes.

From Silver Nanoparticle to Thin Films Produced by Pulsed Laser Deposition: Effects of Ar Gas Pressure and Substrate Surface Free Energy

From Silver Nanoparticle to Thin Films Produced by Pulsed Laser Deposition: Effects of Ar Gas Pressure and Substrate Surface Free Energy

Investigating neutron scattering in a Spherical Proportional Counter: A tabletop experiment

In this paper, we report on a tabletop experiment studying neutron scattering in a Spherical Proportional Counter using an Am-Be source. Systematic studies were carried out to investigate the effect of gas mixture, pressure, operating voltage, and sphere size on the drift time-rise time relationship of the signal in a spherical proportional counter. Our experimental results showed good agreement with MagBoltz-based simulations. These findings are a crucial step towards measuring the quenching factor in gases using a neutron beam for the New Experiments With Spheres-Gas (NEWS-G) experiment and has important implications for the development of neutron detection techniques and their potential applications in nuclear and particle physics.

Aerosol Deposition of CuFeO2 Photocathode Coatings for Hydrogen Production

AbstractPhotoelectrochemical (PEC) water splitting is a viable route for green hydrogen generation. In PEC cells, the electrodes are coated with suitable semiconductor materials, which absorb the sunlight, generating charge carriers that are used to split water molecules into H2 and O2. CuFeO2 is one promising photocathode material for water splitting. However, its performance is limited by electron/hole pairs recombination within the film and at the film/substrate interface. Aerosol deposition (AD) can be employed to minimize charge recombination by spraying dense, thin films and by establishing a good back-contact interface. In this study, CuFeO2 powders were synthesized through a conventional solid-state technique and sprayed by AD under varied parameter sets. The effect of particle size distributions, carrier gas, gas pressure and substrate temperature was investigated. The best spraying parameter set was then tuned to obtain thin coatings (< 1 µm). Single-particle deformation and coatings microstructure were investigated by scanning electron microscopy. Optical properties of CuFeO2 films were analyzed by UV–Vis spectroscopy, while photoelectrochemical performances were estimated through amperometry tests under simulated sunlight. The results of this research show that CuFeO2 photocathodes can be successfully manufactured by AD. Their performance can be optimized by adjusting coating thickness and by annealing in air.

Theoretical research on high-efficiency region in cryogenic micro flow heat transfer based on thermal and viscous Knudsen numbers

Cryogenic micro flow heat transfer (CMFHT) has been increasingly interest nowadays due to the urgent needs of superconductive technology, quantum engineering, space cryocooler and other frontier fields. Chasing its high-efficiency region is a key challenge as thermal penetration depth is limited in cryogenic microscale. Therefore, this paper focuses on high-efficiency region in CMFHT, and newly proposes two parameters: thermal and viscous Knudsen numbers (KnT and Knv) based on traditional Knudsen number Kn, which can improve the errors on micro measurement and the inconveniences on high-efficiency region analysis induced by Kn. High-efficiency region is modeled by the three Knudsen numbers and is separated into slip or continuum type bounded by Kn = 0.001. The effects of gas species, temperature and pressure on KnT and Knv are studied and it is found that the reductions of both thermal penetration depth and the range between thermal and viscous penetration depths with temperature dropping deteriorate heat transfer at low temperature. After applicability validations based on opened literatures, it is suggested that in cryogenics ensuring Kn>KnT (L<δT) is put in the first for good heat transfer, and the next is trying the best to ensure Kn<Knv (L>δv) or making Kn and Knv as close as possible.

Effect of Fiber-Laser Parameters on Cutting Accuracy of Thin and Thick S355JR Structural Steel Plates

Fiber lasers, the latest laser-cutting technology, are notable for their high process efficiency, cutting precision, and high cutting quality for thin materials. However, the quality of the cut significantly decreases when machining thicker materials. For now, this is a challenge for the metalworking industry. This study investigated the effects of laser power, cutting speed, and auxiliary gas pressure on the fiber-laser cutting quality of 4 and 6 mm thick S355JR steel plates. To evaluate the influence of cutting parameters on cutting quality, surface roughness, dimensional accuracy and cut taper were measured. A microscopic analysis of the laser cuts was performed, revealing the heat-affected zone, transition zone and unaffected base-material zone. Research results show that laser cutting is a complex process, and the correct choice of cutting parameters greatly influences the cutting performance and final quality. An artificial neural network was created and trained using the results from measuring the quality characteristics to achieve optimum cutting quality. The accuracy of the optimization model was assessed by control samples, which were cut using calculated optimum parameters. The actual values of the quality characteristics only slightly differ from the predicted values, showing that the optimization model is suitable for selecting cutting parameters.

Effect of gas pressure on the creep and seepage characteristics of low permeability coal

Effect of gas pressure on the creep and seepage characteristics of low permeability coal

Impact of Pressure and Temperature on Charge Accumulation Characteristics of Insulators in Direct-Current Gas-Insulated Switchgear

Direct-current gas-insulated switchgear (DC GIS) is an important device for promoting the lightweight and compact design of offshore wind power platforms. Gas pressure and temperature gradients are crucial factors that must be considered during the design process of the DC GIS. In this study, the multi-physics coupling model of basin insulators considering surface charge accumulation was established, and the corresponding real-sized insulator surface charge measurement platform was constructed. The effects of gas pressure and temperature gradient on the surface charge accumulation characteristics were investigated, respectively. The results show that the effect of gas pressure on the surface charge distribution characteristics depends on the dominant mode of surface charge. When volume conduction is dominant, the effect of gas pressure on the surface charge is negligible. However, when gas conduction is dominant, the accumulation of a uniform charge pattern on the insulator surface increases with the rise in gas pressure. Furthermore, due to gas convection, the temperature of the upper part of the DC GIS is significantly higher than that of the lower part, which leads to a temperature difference between the upper and lower surfaces of the insulator. The charge density on the insulator upper surface near the central conductor rises with the increase in load current.

Fabry-Pérot photothermal interferometry in a hollow-core antiresonant fiber for gas detection in mid-infrared

Hollow-core antiresonant fiber can simultaneously act as a miniature gas cell and the light guidance with broad wavelength range, introducing an powerful tool to photothermal spectrosocpy and sensitive gas detection. Photothermal interferometry (PTI) is a spectroscopic tehcnique that employs an interferometer to finely measure the photothermal signal of trace gas. By splicing the HC-ARF between solid core fibers, a Fabry-Pérot (F-P) cavity is formed and enables PTI with a brief in-line design. However, the previous structure commonly adopted single-mode solid core fibers and might introduce large optical loss due to mode field mismatch, particularly for MIR pump laser. This could lead to significant decrease in sensitivity. Besides, the gas pressure effect on the HC-ARF-based PTI gas sensor had not been fully studied. In this work, we demonstrated the PTI for 13CO2 detection at 4.35 µm by employing an HC-ARF with a 100-µm core. An InF3 multimode fiber was utilized for the efficient delivery of MIR pump beam and successfully enhanced the pump power by a factor of 6.7. The limit of detection was determined to be 0.4 ppb at the integration time of 240 s. Finally, the relationship between gas pressure and photothermal signal was experimentally studied and compared with theoretical results.

Determining the effect of laboratory testing conditions on working parameters of the ST-25 hall thruster

The object of this study is the ST-25 Hall thruster with limited discharge power, no more than 200 W, designed by Flight Control LLC (Ukraine). The problem that was solved in the current paper was to determine the effect of residual gas pressure in vacuum chambers on the operating parameters of the Hall thruster. To solve this task, the operating parameters of the ST-25 thruster were determined, which was tested in three vacuum chambers with different sizes of residual pressure. As a result of the laboratory study into the operating parameters of the ST-25 thruster, the volt-ampere characteristics of the engine discharge at fixed values of the working gas (xenon) flow rate were obtained. The dependences of the engine thrust on the mass flow rate of the working gas at fixed values of the discharge voltage were derived. Based on the experimental data, the dependences of the specific impulse of the engine anode unit on the discharge voltage, as well as the dependence of efficiency of the engine anode unit on the discharge voltage were calculated. The studies showed that when the residual pressure in the vacuum chamber is reduced by 2–3 times, the operating parameters of the engine increase by 15–20 %. Such a reduction in residual pressure increases thrust by 25–40 %. Special feature of the results is the determination of threshold values of residual gas pressure in vacuum chambers during experimental studies, in which the operating parameters of the Hall thruster are similar to its operating parameters under space conditions. This work’s findings could be used in practice when conducting experimental studies of electric rocket engines, when it is necessary to estimate the operating parameters of Hall thrusters that will be obtained under actual space conditions

The Effect of Internal Gas Pressure on the Compression Properties of Natural Rubber Foams.

This study explores the effect of internal gas pressure (P) on closed-cell natural rubber (NR) foams. Three key factors are analyzed using a 3D model during uniaxial compression: (1) the initial gas pressure (P0 = 1, 2, and 3 atm) inside the cells, (2) different cell sizes (D = 0.1, 0.2, 0.3, and 0.4 mm in diameter), and (3) the presence of defects (holes in the cell walls) in terms of their sizes (d = 0.07 to 0.1 mm). The findings reveal a negative relationship between the initial gas pressure and the relative internal gas pressure (α = P/P0) and a direct correlation with stress during compression. For instance, a change from 1 to 3 atm of the initial internal gas pressure results in a 158% decrease in α with only a 3% increase in stress. Larger cell sizes contribute to higher α but lower stress levels during compression. Changing the cell size from 0.1 to 0.4 mm generates a 27% increase in α but a 45% drop in stress. An analysis of hole sizes (cell connection) indicates that larger holes result in higher relative internal gas pressure, while smaller holes lead to higher stress levels because of more flow restriction. For example, increasing the hole size from 0.07 to 0.1 mm leads to an 8% higher α but a 32% stress reduction. These findings highlight the significant effect of the internal gas pressure inside the cells in determining the mechanical properties of rubber foams, which are generally neglected. The results also provide useful insights for better material design and different industrial applications. This study also generates predictive models to understand the relationships between stress, strain, initial gas pressure, cell size, and defects (holes/connections), enabling the production of tailor-made rubber foams by controlling their mechanical behavior.

Molecular dynamics investigation of gold nanoparticle coalescence under realistic gas-phase synthesis conditions

Dependence of nanoparticle (NP) coalescence on various physical parameters (e.g., temperature, number of NPs, NP size, orientation, crystallinity, shape, or composition, etc.) is a very active field of investigation. However, most computational studies on NP coalescence to date are performed in vacuum, with only a handful of studies taking gas pressure into account and even fewer doing a systematic analysis. This is due to two reasons: first, many computational studies complement inert-gas condensation experiments, which typically happen at high vacuum. Second, a simulation set-up in vacuum is simpler and computationally less costly. Here we utilised classical molecular dynamics for a rigorous investigation of the effect (or lack of) of gas pressure, as well as of other parameters (namely temperature, angular momenta, and inert-gas species), on the early stages of coalescence between two metallic NPs. Our approach is relevant for both inert-gas condensation in high vacuum and aerosol synthesis in standard atmospheric conditions. Multiple linear regression analysis confirmed temperature as the key factor determining the degree of coalescence; relative angular momenta direction was revealed as yet another important contributor, whereas the effect of pressure was deemed insignificant for early coalescence stages. To shed light onto the sintering process we elaborate on interesting atomistic mechanisms. We aspire that our study may indicate potential strategies for both gas-phase synthesis methods.

Pore-scale water–gas distribution and gas permeability of natural gas hydrate reservoirs in the South China Sea

Challenges in water drainage within natural gas hydrate reservoirs in the Shenhu area of the South China Sea, characterized by high clay content and strong hydrophilicity, significantly hinder natural gas recovery. Examining the effects of gas pressure and liquid/gas saturation on gas permeability reveals essential insights for increasing gas production potential. We report gas displacement experiments on clayey-silt sediment samples, alongside X-ray computed tomography imaging, that reveal critical findings: a notable increase in flow rate and permeability as displacement pressure nears compaction pressure, highlighting the role of pressure management in enhancing recovery; water displacement from varying pore sizes under different pressures, highlighting the influence of pore size on fluid dynamics, and structural changes, including microfracture formation and a significant fracture that enlarges total pore space by about 15%, which collectively suggest methods to improve gas flow and recovery. Moreover, our analysis identifies average throat length, fractal dimension, and succolarity as principal controls on gas permeability, indicating the substantial impact of microstructural properties on extraction efficiency. These outcomes offer valuable strategies for optimizing natural gas hydrate reservoir development in the South China Sea, emphasizing the need for meticulous pressure and saturation control and in applying a deep understanding of microstructural dynamics.