Influence Of Gas Mixture Research Articles

Моделирование работы самотечных участков нефтепровода

In the modern world it is difficult to underestimate the role of oil in the economy of each country. It is a raw material for chemical processing, an energy carrier with a long history of production and transportation. The prevailing volume is delivered overland by pipeline transportation due to high transportation speed, flow rate and the possibility of regulating pumping stops. However, the main difficulty in pipeline operation is the selection of the optimal pumping mode. Due to terrain peculiarities, as well as variable oil flow rates along the length of the pipeline route, gravity pumping sections occur. Operation of the oil pipeline with these sections is complicated due to the change of pumping from single-phase to two-phase and the influence of vapor-air mixture on oil pumping indicators. In this paper the main indicators of gravity mode of oil pumping are considered, numerical modeling methods are applied to derive a new formula that considers the influence of gas mixture on the transported oil flow; a 3D model of the stand is proposed, on which this mathematical model will be verified, as well as the invented instruments (devices) for determining the coefficient of oil pipeline filling will be tested.

INFLUENCE OF GAS MIXTURES OF HYDROGEN WITH METHANE ON THE OPERATIONAL AND THERMOPHYSICAL CHARACTERISTICS OF POLYETHYLENE PIPES OF OPERATING GAS DISTRIBUTION NETWORKS OF UKRAINE

The paper presents the results of complex studies of the influence of mixtures of hydrogen gas with natural gas in the ratios of 10%Н2/90%СН4 and 20%Н2/80%СН4 on the operational and thermophysical characteristics of PE-80 polyethylene pipes and their material Research was conducted on an experimental stand, the diagram of which is attached. The results of comprehensive strength and thermophysical studies of the material of PE-80 polyethylene pipes, which were previously operated in the current gas distribution networks of Ukraine for 15 years, after 6 months of hydrogen exposure, are presented. In order to indicate possible changes in the properties of the material, the same complex of studies was carried out before hydrogen exposure of the samples. The influence of gas mixtures on the thermophysical properties of polyethylene pipes has been established, which is manifested in the reduction of the size of polyethylene crystallites and their orderliness in the volume of pipe walls under the influence of gas mixtures. At the same time, the appearance of crystallites of a new shape was found on the surface of the inner wall of the pipes. It is assumed that this may be caused by the competing action of methane and hydrogen molecules. In the course of conducting hydraulic tests on the resistance of pipes to internal pressure and mechanical studies on uniaxial tension, it was determined that all pipe samples, according to their strength characteristics, meet the requirements of regulatory documents issued for polyethylene pipes used for natural gas transportation. The relationship between the concentration of hydrogen in the mixture and the degree of its influence on the strength characteristics of the samples was established. No changes in the chemical structure of the material of polyethylene pipes were detected. It should be noted that the given results are only the beginning of a more detailed study, during which it is also planned to investigate the effect of hydrogen mixtures on technical polyethylenes after 12 and 24 months of hydrogen exposure. Bibl. 17, Fig. 11, Tab. 2.

Microstructure and Wear Properties of a Low Carbon Bainitic Steel on Plasma Nitriding at Different N2-H2 Gas Mixtures

For the first time, the influence of gas mixture on first damage resistance of a plasma nitrided DIN 18MnCrSiMo6-4 bainitic steel was investigated. Samples were nitrided at 500 °C with three different N2-H2 gas mixtures, containing 5, 24, and 76 vol.% N2. Samples were characterized concerning the resulting roughness, microstructure, compound layer’s phase composition, residual stresses in the diffusion zone, and surface hardness. Tribological ball-on-flat tests were carried out in reciprocal mode using zirconia as ball material for friction coefficient and the compound layer resistance until the first damage. The test results were evaluated statistically by analysis of variance (ANOVA). As the amount of nitrogen in the gas mixture decreases, the ε-Fe2-3(C)N content in the compound layer decreases. A γ’-Fe4N monophasic compound layer was achieved at 5 vol.% N2 gas mixture. The diffusion zone as expected presented compressive residual stresses with the highest values near the surface. In the tribological tests, better results were obtained for 5 and 24 vol.% N2 in the gas mixture as higher amounts of γ’-Fe4N were formed. The 76 vol.% N2 gas mixture led to a brittle behavior, due to the biphasic compound layer (γ’-Fe4N and ε-Fe2-3(C)N) with a predominant content of ε-Fe2-3(C)N.

Effect of H<sub>2</sub>/N<sub>2</sub> Mixtures on Reduction of Nickel Oxide

This paper describes the reduction of nickel oxide under different gas mixture. The influence of gas mixture on phase, density, morphology and pore size of reduced nickel oxide were studied. Nickel oxide pellets sintered at 1400 °C were reduced under various hydrogen-nitrogen gas mixtures, namely 40% H2-60% N2, 60% H2-40% N2, 80% H2-20% N2. Phase identification, density measurement and observation of morphology were conducted on samples before and after reduction process. Under all gas mixtures, nickel oxide was completely reduced to nickel. Density of the samples decreased in the range of 21% to 32% depends on H2 percentage used. Results from the density shows that the higher the H2 gas concentration, the smaller the density changes. Significant change in porosity of the sample before and after reduction was observed. Size of pore after reduction determined by H2 concentration used during reduction where the higher the H2 concentration resulted in large pore size.

A study on the influence of gas mixtures on the property of plasma‐activated water

AbstractThe present study applying a plasma jet to activate water in a controllable environment is aimed to investigate the effect of a combination of (working/chamber gas) on the properties of plasma‐activated water. After 10 min of activation, results reveal that a significant decrease in solution pH is observed with the presence of N2. Hydrogen peroxide appears to be the major species for most gas mixtures, except [Ar + air/Ar] and [Ar + air/air], where nitrite and nitrate dominate. A gas mixture of [Ar + air/Ar] produces the maximum concentration of , while the maximum and H2O2 are observed for [Ar + air/air] and (Ar/Ar), respectively. Overall, the antibacterial efficacy correlates well with concentration.

Influence of Gas Mixture and Temperature on AP‐CVD Synthesis of Graphene on Copper Foil

The influence of methane and hydrogen concentration as well as temperature of synthesis on the number of layers, area of coverage, and quality of graphene formed by chemical vapor deposition on copper is studied in this paper. It is shown that methane concentration primarily affects the sample coverage area. The temperature determines the number of graphene layers and the defect rate of graphene planes. The influence of hydrogen concentration is complex: low hydrogen concentrations are insufficient to induce efficient decomposition of methane on the copper surface; high concentrations of hydrogen limit nucleation of graphene layers and the formed graphene structures are subject to etching.

Influence of gas mixture during N+ ion modification under plasma conditions on surface structure and mechanical properties of Al–Zn alloys

Aluminum, and particularly its alloys, are the materials of an increasing significance in construction and automotive industry due to the combination of their strength properties. However, their functionality is limited mainly because of the susceptibility on tribological wear. This paper presents the results of the study aimed at determining the optimum conditions of the process of alloy surface modification with N+ ions in the atmosphere of N2–H2, using the method of chemical precipitation from gaseous phase, combined with a discharge of a frequency of 13.56MHz (radio frequency chemical vapor deposition). It was demonstrated that the process of Al–Zn alloy surface modification with nitrogen ions is a necessary prerequisite to obtain low-friction coatings (SiCNH in this case) characterized by a good and stable adhesion to the aluminum alloy substrate. The highest hardness is obtained in the case of SiCNH coating deposition process, preceded by the process of surface modification in plasma conditions, provided for N2 only (hardness 10.0GPa) of the N2/H2 mixture (flow ratio 3/1, hardness 10.5GPa). The surface of alloy combined with the obtained DLC (diamond-like carbon) layers, doped with N and Si atoms is characterized by ca. 30% decrease in the friction coefficient value (up to the 0.2 value) and ca. 25% decrease in the value of surface roughness (Ra, 6.5nm), compared to unmodified substrates.

Influence of Gas Mixture on Quality and Shelf Life of Veal Calf Meat

The paper investigates the effect of two different gas mixtures on chemical, physical and microbiological quality of veal meat packed in modified atmosphere during chill storage. Experimental gas atmospheres tested were O246 (46% O2, 31% N2 and 23% CO2) and O270 (70% O2, 8% N2 and 22% CO2). Samples were stored at 4°C for 14 days and tested at 0, 2, 4, 6, 8, 10, 12 and 14 days after packaging. The different O2 concentration influenced many parameters. Lower O2 concentration showed a greater increase of a* values (P<0.01) from the 2nd to the 8th packaging day, and a lower increase in drip loss values, thiobarbituric acid reactive substances and protein oxidation (P<0.001). Total aerobic mesophilic and psychrophilic count showed a gradual increase in bacterial load over storage time in both the experimental treatments. Results obtained showed that O246 is better than O270 in calf meat packaging because of a belated decline of meat quality, particularly about oxidative parameters.

Low-temperature plasma carburizing of AISI 420 martensitic stainless steel: Influence of gas mixture and gas flow rate

Low-temperature plasma carburizing was studied aiming to determine the effect of the gas mixture and flow rate on the surface properties of AISI 420 martensitic stainless steel samples. Plasma carburizing was carried out for gas mixtures of 20% Ar+80% H2 comprising CH4 contents between 0.25 and 1.00%, and gas flow rates ranging from 1.67×10−6 to 6.68×10−6Nm3s−1. The modified layers were characterized by confocal laser scanning microscopy, X-ray diffractometry and microhardness measurements. The plasma was also characterized by optical emission spectrometry. Results indicate the presence of a hard and thin outer layer and a carbon-enriched martensite diffusion layer. It is shown that gas mixture composition plays an important role in the process kinetics. Spectroscopic characterization of the glow discharge shows that the variation of the CH4 content in the gas mixture leads to a variation of the emission lines intensity but does not significantly alter the relative peak intensities. It suggests a variation on the plasma density and no significant variation on the active species. It also indicates that, for the studied conditions, the emission spectroscopy cannot be applied as a tool for process control.

The Influence of Gas Mixture in the Glow-Discharge Nitriding Process of Austenitic Stainless Steel on Characteristic of Nitrided Cases

This paper presents investigations of nitrided cases after the glow-discharge nitriding process. The nitrided cases were obtained by using a different chemical composition of gas mixture at the temperature of 450OC. The glow-discharge nitriding process was carried out on austenitic stainless steel, grade of steel X5CrNi18-10. The chemical composition and phase identification of the nitrided cases were examined by using the glow-discharge optical emission spectrometry (GD-OES) and X-ray diffractometry (XRD)

Electrical analysis of positive corona discharge in air and N2, O2, and CO2 mixtures

This paper presents an experimental analysis of the electrical behavior of positive point-plane corona discharges. The corona current, streamer velocity, mean discharge frequency, and current-voltage characteristic are studied, firstly in synthetic air as a function of experimental parameters such as gap distance and tip radius. Different electrical diagnostics are used in order to better understand the streamer development as well as the dependence of its characteristics on the previous listed parameters. Then the influence of gas mixture (several proportions of N2 and O2 with or without CO2) is analyzed. When the gas concentration is varied the shape and amplitude of the corona current are significantly affected due to the variation of the gas electronegativity following its composition and concentration. The ionization and attachment coefficients are calculated from the electron energy distribution function in the case of these different gas mixtures in order to quantify the critical electric field value enabling the streamer development for a given gas mixture.

Study of the duplex treatment on 32CrMoV13 low alloy steel: Application in wood machining

The aim of this study is to optimise the application of duplex treatments by modifying the nitriding conditions and using a new kind of PVD coating like ZrBN compound. The influence of gas mixture (composed of N2, H2) and time of nitriding on the mechanical and structural properties of 32CrMoV13 low alloy steel was studied. An optimisation of a ZrBN coating was also conducted. After the characterisation of the nitrided layers and coatings (XRD, SEM, EDS, hardness profiles,…), different kind of cutting knives were treated and tested in the peeling of non-defect beech wood. It appears that the duplex treated knives (nitriding with 80% of N2 and a ZrBN coating) performed best and allowed an increase of almost twice the tools' service life.

New large area ultraviolet lamp sources and their applications

Dielectric barrier discharges are used to generate ultraviolet radiation in rare gases and rare gas-halide mixtures. The characteristics of the emission spectra of the excimers formed, from 126 to above 308 nm are found to be useful for thin film and surface processing. The underlying radiation generation mechanisms are described and the influence of gas mixture, concentration and total pressure on the UV emitted discussed. Conversion efficiencies (from input electrical to output optical energy) as high as 15% can be achieved under optimum conditions. These low cost, high power excimer systems can provide an interesting and potentially very useful alternative to conventional UV lamps for industrial large-scale low temperature processes.

Influence of gas mixture and primary ionization on the performance of limited streamer mode tubes

We report a study of the dependence of limited streamer mode operation on gas composition. Results are given for the plateau onset voltage, plateau length, charge versus voltage, charge spectra and pulse width for various fractions of (Ar, CO 2, pentane) and (Ar, isobutane). In addition, a series of argon-free strong quenching gas mixtures has been studied which have very attractive characteristics. Chamber lifetime tests for these are also reported. As part of a study of the nature of the limited streamer mode mechanism, the response to X-rays and minimum ionizing particles are compared and differences noted. The character of the primary ionization is found to have a clear effect on the chamber response even in the streamer region.

Influence of gas mixture and cathode material on limited streamer operation

A systematic study on limited streamer tubes 8 × 8 mm 2 in cross section has been performed, testing different gas mixtures and cathode materials. A discussion concerning the set of gas mixtures allowing streamer operation is presented. Plastic tubes with graphite cathode are found to exhibit a wider operation range than aluminum tubes.

Influence of Gas Mixtures on Cell Division and Root Elongation of Broad Bean, Vicia faba L.1

AbstractRoots were grown in airtight chambers in an intermittent nutrient solution mist. Various gaseous mixtures were used to determine the effects of short‐term aeration deficiencies on cell division and root growth. Following treatments of 4 to 24 hours, the roots were aerated with air for 5 days. Root tip samples were prepared for microscopic examination at several times during and after treatment.Oxygen levels of I to 10% without CO2 reduced the rate of cell division as much as 80% at the end of a 94‐ hour treatment; however, cell division resumed rapidly after treatment. Nitrogen reduced cell division in secondary roots within 15 minutes, stopped all division within 94 hours, and frequently killed primary root tips. After being returned to air, the rate of cell division in the old secondary root system was approximately 70% of normal within 48 hours, but few new roots developed. Mixtures of gases containing 1 to 10% O2 plus enough CO2 to equal 91% killed part of the secondary root system but rarely killed the primary root tip. These data show that either zero 02 or high CO2 for only 94 hours injures the root system of Vicia faba L. and that high CO2 is more injurious than zero 02.