Behavior Of Gas Research Articles

Exploring the influence of metal oxides on the pyrolytic behavior and decomposition mechanism of the green gas generating agent 5-Aminotetrazole

5-Aminotetrazole (5AT) is widely used as a green gas-generating agent in fire extinguishers, but it exhibits low combustion stability. To enhance its combustion rate and modify gas production performance, this study investigated the catalytic effects of adding different metal oxides (Bi2O3, PbO, TiO2, and CoO) on its pyrolysis process and decomposition mechanism. The pyrolysis behavior and pyrolysis products of 5AT were studied by simultaneous thermal analyzer (thermogravimetry - differential thermal analysis, TG-DTA) and TG-FTIR/MS (mass spectrometry and fourier transform infrared spectroscopy) hyphenated instrument. Isoconversional methods were used to calculated kinetic parameters, and reaction mechanism was also speculated by combining the experimental and calculational results. The experimental results indicated that Bi2O3, PbO, TiO2 and CoO have minimal impact on the ring opening reaction process of 5AT, but they catalyzed the polymer decomposition process of 5AT, especially CoO. Consequently, the addition of metal oxides as catalysts to 5AT holds significant potential for improving its thermal safety and enhancing its suitability as a solid propellant gas generator.

The Effect of Wettability on Confinement-Induced Phase Behavior and Storage of Alkane in Nanoporous Media.

The impact of wettability on the confined phase behavior of fluids is paramount for various applications, such as gas storage, carbon dioxide sequestration, and water purification. However, the understanding of the fluid-solid intermolecular interactions in confined systems is still limited and requires further investigation. This work investigates the effect of hydrophilic and hydrophobic nanoporous materials on the adsorption and desorption isotherms of n-butane. The hydrophilic samples in this research are MCM-41 silica powder with two different pore sizes (80 and 100 Å). MCM-41 samples were successfully treated with hexamethyldisilazane (HMDS) to create hydrophobic adsorbents. Isotherms of n-butane in materials with different wetting states were generated at various temperatures using an upgraded gravimetric apparatus. The results demonstrated that n-butane was adsorbed more onto the hydrophilic MCM-41 materials during the initial adsorption process. The lower affinity between n-butane and the modified MCM-41 samples slightly increased the capillary condensation and evaporation pressures in these materials compared to those in the original ones. However, it is noted that wettability's influence on the confined phase transitions of n-butane was not significant in this study. Interestingly, the hysteresis behavior of the vapor-liquid and liquid-vapor phase transitions due to confinement was independent of the surface's wetting properties. Kelvin's equation for a hemispherical meniscus was adopted to evaluate the capillary evaporation pressures of n-butane in nanopores. The calculated pressures showed agreement with experimental data when appropriate pore size and surface tension values were applied. These findings provide valuable insights into the impacts of surface chemistry and wettability on the phase behavior of hydrocarbon gas in nanoporous media. Furthermore, this study enriches the experimental database on confined fluids, which is essential for developing accurate theoretical and modeling tools for numerous industrial and scientific applications.

Tribological Performance Enhancement of AISI 1050 Steel through FeNiCrCoMo High-Entropy Alloy TIG Weld Cladding

The tribological behavior of tungsten inert gas (TIG) welded high entropy alloy (HEA) FeNiCrCoMo cladding deposited on AISI 1050 steel substrate was studied. The response surface methodology (RSM) optimized the TIG welding parameters. The SEM images revealed no signs of intermetallic compounds in the cladding, and the XRD analysis showed that the FeNiCrCoMo greatest peak corresponds to the BCC+FCC mixed phase. The microhardness and sliding wear resistance of the cladding were superior compared to the steel substrate owing to the solid solution strengthening and the presence of mixed phase. The worn surfaces of HEA claddings showed the presence of wear debris, grooves and micro-cutting from sliding wear as revealed by the SEM and 3-D profilometry images.

Nonlinear wave dynamics in ferromagnetic media: A study with the Kuralay-IIA equation

In this research, we delve into the exploration of the Kuralay-IIA equation by employing two power full approaches, namely extended hyperbolic function method (EHFM) and the improved modified Sardar-subequation method (IMSSEM). Applications of the Kuralay-IIA equation can be observed in a variety of physical phenomena, particularly in optical fibers, magnetic materials, and nonlinear optics. This equation performs an essential part in understanding gas behavior. Specifically, it offers an image of the relationship between volume, temperature and pressure in a gas system. We proceed through the matter in detail through the use of space curves which demonstrate integrable motion. Using the proposed techniques, our investigation provides an extensive variety of soliton solutions, such as periodic, dark–bright, bright, dark, solitary, and some other solutions. These solutions are in good alignment with previous study findings in this area. Analytical wave solutions are vital as they provide a basic comprehension of the physics or mathematics at play and establish a framework for further studies. The findings obtained from this study may help design models to come. The techniques used in this study are very effective, straightforward, and capable of handling more nonlinear models with high reliability. We use the Mathematica software to validate the accuracy and reliability of our results. Using carefully constructed 2D and 3D graphs generated, the resulting solutions are visually shown.

Adsorption and sensing performances of transition metal doped ZnO monolayer for CO and NO: A DFT study

In this study, theoretically, density functional theory was employed to explore the adsorption behavior of CO and NO prevalent hazardouss gases, on transition metal (TM = Fe, Co, Ni, and Cu) doped ZnO monolayer. The multifaceted analysis encompasses an array of critical aspects, including the adsorption structure, adsorption energy, density of states (DOS) and electron transfer to unravel the adsorption behavior. Our calculations show that TM atom doped ZnO monolayer exhibit high stability. TM doped can significantly enhance the interaction between the gas molecules (CO and NO) and the ZnO monolayer. Analysis of the recovery time and electrical conductivity of the adsorbed systems suggests that the Co-ZnO could be a suitable material for CO sensing,while the Cu-ZnO and Ni-ZnO can be used for NO sensing. These results suggest that transition metal doped can be a promising sensor candidate for toxic gas molecules adsorption and detection.

Simulation of Adsorption and Separation Behavior of Elemental Gases on Lanthanide-Based Nd-MOF

Simulation of Adsorption and Separation Behavior of Elemental Gases on Lanthanide-Based Nd-MOF

Pore-scale binary diffusion behavior of Hydrogen-Cushion gas in saline aquifers for underground hydrogen Storage: Optimization of cushion gas type

Cushion gas is required to prevent hydrogen (H2) trapping and interactions between H2 and brine for underground hydrogen storage (UHS) in saline aquifers. However, selecting an appropriate type of cushion gas is not a straightforward task, as it affects the H2 diffusion characteristic in subsurface porous media, thereby impacting purity, recoverability, etc. In this paper, we developed a modified pore network model (PNM) for binary diffusion that incorporates multi-scale diffusion mechanisms to forecast the H2 effective diffusion coefficient (DH2e) and evaluate the impacts of the cushion gas on DH2e. Additionally, the model accounts for the water-lock effects of residual brine, focusing exclusively on the connected pore-throats occupied by the gas phase, which are identified using the invasion percolation algorithm with trapping. Our key findings are as follows: 1) CO2 and N2 demonstrate superior containment effects on H2 compared to CH4 under the specific conditions of the target aquifer, reducing the H2 contamination caused by binary diffusion; 2) The size and topology of porous media exert minimal impacts on the selection of cushion gas, yet they markedly affect the DH2e; 3) The pressure and temperature conditions of the saline aquifer are critical factors in cushion gas selection, with temperature being the more influential parameter. This study provides valuable insights for the implementation of industry-scale UHS in saline aquifers.

Study on the Impact of Porous Media on Condensate Gas Depletion: A Case Study of Reservoir in Xihu Sag.

During the depletion and pressure reduction process in condensate gas reservoirs, the precipitation of condensate oil transforms the single-phase gas flow into a two-phase gas-liquid flow, significantly reducing the permeability. Currently, microscopic studies of the phase behavior of condensate gas in porous media mainly focus on observing and describing the occurrence of condensate oil, lacking quantitative calculations and direct observations of condensate oil throughout the entire depletion cycle. This paper uses a microvisualization method to simulate the depletion process of condensate gas reservoirs. Condensate gases with oil contents of 175.3 and 505.5 g/cm3 were prepared by mixing methane, ethane, hexane, and decane in specific proportions. Pore structures were extracted from thin sections of real core casts, and microfluidic chips with a minimum pore diameter of 20 μm and an areal porosity of 20.75% were fabricated by using a chemical wet etching method. Subsequently, microfluidic condensate gas depletion experiments were conducted with chip images recorded during the depletion process. Grayscale analysis of the depletion images was performed using ImageJ software to quantitatively calculate condensate oil saturation and recovery rates, analyzing the effects of different condensate oil contents on condensate gas depletion, and comparing the differences between depletion in porous media and in a PVT cell. The conclusions drawn are as follows: the dew points of high and low in the porous media are 3.15% and 1.85% higher than those in the PVT cell, respectively. In the early stages of depletion, condensate oil saturation in porous media is higher than that in the PVT cell, while in the middle to late stages, condensate oil saturation in porous media is lower than that in the PVT cell. The condensate oil recovery rate in porous media is significantly higher than the depletion recovery rate in the PVT cell. Condensate oil tends to precipitate and disperse at blind ends and corners, while it easily forms patches in mainstream large pores.

Conservation laws of the one-dimensional relativistic magnetogasdynamics equations

Abstract The present paper offers a comprehensive analysis of the one-dimensional relativistic magnetogasdynamics equations in Lagrangian coordinates. These equations, describing the behavior of a relativistic magnetized gas, are reformulated in variational form to facilitate further analysis. A complete group analysis of the resulting Euler-Lagrange equation is performed, allowing us to systematically identify the symmetries inherent in the system. Using Noether’s theorem, we derive conservation laws in Lagrangian coordinates, offering critical insights into the invariants and conserved quantities of the system. This work expands the theoretical understanding of relativistic magnetogasdynamics.

Characterizing the development of gravity-driven slug flows using high-speed imaging and PIV-PLIF techniques

Although developing gravity-driven slug flow frequently occurs in oil and gas, and energy systems, its development dynamics remain underexplored; this gap, in turn, has left the underlying relationships between flow evolution and transport phenomena in these applications inadequately characterized as well. The present study experimentally investigates the spatiotemporal-spectral development of gravity-driven air–water and CO2-water slug flows in a vertical 25.4 mm ID pipe. Enhanced flow visualization techniques, utilizing high-speed imaging and particle image velocimetry-planar laser induced fluorescence (PIV-PLIF), were employed to determine the behaviors of gas and liquid phases and interactions at four positions along the pipe axis. A machine vision-based algorithm was employed to extract slug unit cell characteristics and instantaneous void fraction signals, allowing for a comprehensive statistical analysis of gas phase behavior across the flow domain. A novel algorithm was also developed to preprocess raw PIV-PLIF images, facilitating phase discrimination and noise reduction before PIV cross-correlation analyses are conducted. The results showed a logarithmic growth in the lengths of Taylor bubbles, liquid slugs, and slug unit cells along the pipe, with liquid slugs constituting nearly 60 % of slug units downstream. Taylor bubble length distributions correlated well with log-normal fits, while liquid slug and unit cell lengths transitioned from log-normal patterns upstream to near-normal distributions downstream with broader and less peaked shapes. Taylor bubble velocities and appearance frequencies of the flow structures declined exponentially along the pipe, with Taylor bubble velocities showing narrower and more peaked near-normal distributions downstream. Instantaneous void fraction signals exhibited fewer, wider peaks and troughs with reduced small-amplitude oscillations downstream. The analysis of the signals indicated a complete bubbly-to-slug transition at Z/D=30. Gas-liquid phase interactions, classified as almost-zero, weak, and strong, impacted liquid phase velocity profiles and the behavior of Taylor bubbles, with minimum stable liquid slug lengths of 8–9 D and a wake length of 1.8 D observed. Empirical correlations were developed to represent the spatiotemporal-spectral aspects of flow development, with spectral parameters, particularly liquid slug frequency, identified as the most reliable indicators of the fully developed region, predicting entrance lengths of 114.0 D and 113.4 D for air–water and CO2-water, respectively. Gas density was found to strongly influence flow characteristics and transition, accelerating the approach to the fully developed region.

Application of Raman spectroscopy for analyzing the behavior of gases in sandstone reservoirs

The behavior of gases within subsurface pores determines the oil and gas recovery and CO2 storage in the region. In this study, we report a novel method based on Raman spectroscopy for observing the distributions of CH4 and CO2 gases in the pores of sandstone reservoirs. First, we designed a pressure-cell to inject gases into a sample. Then, CH4 and CO2 gases were injected into the sample using the pressure-cell placed on the Raman spectroscopy system sample stage. Quartz and feldspar were the predominant minerals in the sample. The CH4-occupied pores exhibited a Raman peak at 2917 cm−1. Two-dimensional (2D) and three-dimensional (3D) mapping of the pores depicted the geometry of the CH4 gas-filled pores. After injecting CO2 gas, we observed an intensity peak at 1388 cm-1; we obtained 2D and 3D maps of the CO2 gas-filled pores based on this peak value. This study demonstrates the potential use of Raman spectroscopy as a visualization tool to reveal the pore geometry of sandstone reservoirs and determine the distribution of gases within such reservoirs. Our study can serve as a foundation for understanding the behavior of gases in subsurface reservoirs, improving oil and gas prospecting and exploration, and assessing CO2 storage..

A data-driven method for fast predicting the long-term hydrodynamics of gas–solid flows: Optimized dynamic mode decomposition with control

Data-driven methods are of great interest in studying the hydrodynamics of gas–solid flows. In this paper, we developed an optimized dynamic mode decomposition with control (DMDc) method for long-term and fast prediction of one physical field with the aid of another physical field. Using the computational fluid dynamics-discrete element method (CFD-DEM) simulation results as the benchmark, the prediction ability of the standard DMDc method and the optimized DMDc method is evaluated. It was shown that the optimized DMDc method is superior when the order of magnitude of the predicted data is much larger than that of the auxiliary data, which cannot be addressed by using scaled or dimensionless data, for instance, the prediction of gas pressure with the aid of solid volume fraction; on the other hand, both DMDc and optimized DMDc methods can reasonably predict the long-term behavior of gas–solid flows, when the magnitude of the elements of the predicted field is comparative to that of the auxiliary field. This study proposes a fast and relatively accurate method for predicting the hydrodynamics of gas–solid flows with the aid of a known field.

Influence of the equation of state for moderate to high pressure gaseous systems

For transportation and defense systems, equations of state describe the thermodynamical behavior of gases, as a function of pressure, density, and temperature and are often used to close systems of equation (such as Navier–Stokes for fluid mechanics). For low pressure system (under a few dozen MPa), the ideal gas equation can be used, whereas for high pressure system (above 1000 MPa), dedicated equations of state are used (Jones-Wilkins-Lee: JWL or Becker-Kistiakowsky-Wilson: BKW). For intermediate pressure systems, such as interior ballistics or pyromechanisms, where the pressure is around a few hundreds MPa and many phenomena interact closely and simultaneously (multiphysics system: combustion, fluid dynamics, thermics, fluid-structure interaction, thermodynamics…), the ideal gas equation is not valid anymore and nor are the JWL or BKW equations. A dedicated equation of state is then necessary for intermediate level of pressures, and its choice is not obvious. This paper presents a comparison of equations of state for this range of pressure (Noble-Abel, Van der Waals, virial), details the calculations of the involved coefficients and their effects on uncertainties, and studies the influence of the equation of state on the predictions of pressure, density, pressure coefficient, and heat transfer, with both analytical and numerical approach. The results highlight the importance of the choice of the equation of state, especially for a multiphysics system, as the equation of state influences not only thermodynamical properties (pressure, density, temperature) but also thermical properties of a system, such as heat transfer.

Capturing non-equilibrium in hypersonic flows: Insights from a two-temperature model in polyatomic rarefied gases

The study utilizes a two-temperature model to analyze non-equilibrium in normal shocks within hypersonic flows in polyatomic rarefied gases. Derived from the extended second law of thermodynamics, this model separates translational and internal temperatures in polyatomic gases, providing a more accurate depiction of non-equilibrium gas flow compared to classical theories like the Navier–Stokes and Fourier (NSF) system. Notably, the analysis reveals that the two-temperature model incorporates an additional contribution to the heat flux due to the gradient of the dynamic temperature, resulting in improved accuracy, especially for high Mach numbers. Results show that the model gives satisfactory shock density and temperature profiles up to Mach 10, with very good agreement observed up to Mach 6.1 compared to the classical NSF model. We conduct an order of magnitude analysis on the dynamic temperature and heat flux gradients appearing in the new constitutive equation using the Mott-Smith method. This analysis highlights the impact of these terms on accurately modeling polyatomic gas behavior in high-speed flows. The effects of bulk viscosity and incoming temperature on shock profiles are also investigated, contributing to a better understanding of shock wave structures in polyatomic gases and their implications for hypersonic flow dynamics.

Two-phase modelling for fission gas sweeping in restructuring nuclear oxide fuel

In this work, we propose a modelling approach for the intra-granular fission gas behaviour in UO2 under restructuring process. Leveraging the definition of restructured volume fraction, we consider the fuel matrix transition from the non-restructured to the restructured phase, together with the evolution of the corresponding fission gas concentrations retained in the fuel matrix. Firstly, we derive a sweeping term that exchanges fission gas atoms from the non-restructured to the restructured fuel region. The sweeping term is then included in the conventional intra-granular fission gas diffusion problem. Secondly, the spectral diffusion algorithm is employed to solve two spatially-dimensionless problems, properly representing the non-restructured region with micrometric grains and the restructured region with sub-micrometric grains. The model developed is implemented in SCIANTIX, a 0D meso-scale code for physics-based modelling of fission gas behaviour in nuclear oxide fuel and compared with experimental data and semi-empirical models.

MOF-derived In2O3 nanotubes modified by Bi2Se3 for enhanced NOx detection at room temperature

The In2O3/Bi2Se3 composite was synthesized by loading Bi2Se3 flakes on MOF-derived In2O3 tubes through solvothermal method. The chemical composition, morphology and chemical state of elements for composite were examined through XRD, SEM, TEM and XPS. The In2O3/Bi2Se3 composite exhibited significantly enhanced sensing performance compared to pure In2O3 and Bi2Se3. The response value of In2O3/Bi2Se3 composite is 844 for 30 ppm NOx at 25 °C, which is 21 times that of pure In2O3, and it also displays shorter response /recovery time and lower detection limit. The remarkable gas-sensing properties of In2O3/Bi2Se3 composite are attributable to its large specific surface area, rapid electron mobility, abundant oxygen vacancies and the presence of n-n heterostructure. The adsorption behavior of NOx gas on the surface of In2O3/Bi2Se3 was explored using the in-situ diffuse reflectance infrared Fourier transform (DRIFT) spectrum.

A plethora of novel solitary wave solutions related to van der Waals equation: a comparative study

In this article, we explore exact solitary wave solutions to the van der Waals equation which is crucial for numerous applications involving a variety of physical occurrences. This system is used to define the behavior of real gases taking into consideration finite size of molecules and also has some applications in industry for granular materials. The model is studied under the effect of fractional derivatives by employing two different definitions: β\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$\\beta$$\\end{document}, and M-truncated. Further, new extended direct algebraic method is employed to construct the solitary wave solutions for the model. The solutions transmit several novel solutions, such as dark-singular, dark–bright, singular-periodic and dark solutions, and this method establishes the conditions required for the formation of these structures. To show the comparative analysis between two different fractional operators, results are graphically represented in the form of 2-dimensional and 3-dimensional visualizations.

A first-principles investigation into the adsorption behavior and deposition mechanism of boron-containing gases on Si(100) surfaces during chemical vapor deposition

Polysilicon serves as a primary raw material in the production of solar cells and semiconductors. However, its impurity content, particularly boron, poses significant challenges during the chemical vapor deposition (CVD) process. Therefore, it is essential to investigate the behavior of boron impurities during CVD. In this study, we conducted first-principles calculations to explore the adsorption behavior and deposition mechanism of boron-containing gases (BCl3, BHCl2, B2H6) on the Si(100) surface. We considered different adsorption sites and performed a systematic analysis of various adsorption systems' adsorption energy, charge transfer, and electronic properties. Our findings indicate that BCl3, BHCl2, and B2H6 molecules undergo dissociative chemisorption at specific adsorption sites. Moreover, charge transfer analysis confirms that each of these adsorbed molecules functions as an electron acceptor. Subsequent analyses, including total charge density (TCD), charge density difference (CDD), total density of states (TDOS), and projected density of states (PDOS), collectively underscore the robust electronic interactions between the gaseous molecules and the Si(100) surface. Through the computation of transition states and energy barriers across three potential reaction pathways, we identify a predominant sequence: BCl3→BCl2+Cl→BCl+Cl→B+Cl, that governs boron impurity formation on the Si(100) surface during CVD. Our work elucidates the underlying microscopic mechanisms of boron-containing gas adsorption and deposition in the CVD context.

Profoxydim in Focus: A Structural Examination of Herbicide Behavior in Gas and Aqueous Phases.

This study investigates the chemical structure of profoxydim, focusing on its E-isomer, the main commercial form. The research aimed to determine the predominant tautomeric forms under various environmental conditions. Using proton and carbon-13 NMR spectroscopy alongside theoretical modeling, we examined tautomers and their conformers in different solvents (MeOD, DMSO, CDCl3, benzene) to mimic gas and aqueous phases. The findings reveal that the enolic form dominates in the gas phase, while the ketonic form prevails in aqueous environments, providing key insights into the herbicide's environmental behavior. We also observed an isomeric transition from E to Z under acidic conditions, which could affect profoxydim's reactivity in natural environments. The theoretical calculations indicated that in acidic conditions, the E and Z forms are nearly degenerate, with the E form remaining dominant in neutral environments. Additionally, QSAR models assessed the toxicity of various tautomers, revealing significant differences that could impact bioactivity and environmental fate. This research offers crucial insights into the structural dynamics of profoxydim, contributing to cyclohexanedione chemistry and the development of more effective herbicides.

Computational analysis of the effect of bed particles in a dual chamber internally circulating fluidised bed

ABSTRACT Internal circulation of particles in a dual-chamber fluidised bed can be developed by applying air of unequal velocity at the bottom of each chamber. This internal circulation results in an energy transfer between the chambers which is desirable in several industrial applications. ANSYS-Fluent software is used in this paper to simulate the influence of bed particles on the flow behaviour of gas and solids in a dual-chamber fluidised bed. The results of the simulation are expressed as solids circulation rate (Gs ) and discharge coefficient (Cs ). Simulations show that Cs at the slot ranged from 0.50 to 0.60 whereas Gs in the reactor is significantly affected by varying the bed particles. The pressure difference (due to the difference in density) between the chambers develops the internal circulation of particles in the dual-chamber internally circulating fluidised bed. It was observed that the denser the bed material, the higher the internal circulation is along with the pressure difference near the slot, and vice versa. Therefore, it can be concluded that the ICFB’s performance does depend on the bed particle type.