Increasing Gas Pressure Research Articles

Piezo-ferroelectric response of bismuth ferrite based thin films and their related photo/piezocatalytic performance

Bismuth ferrite based thin films were grown by RF magnetron sputtering under different experimental conditions. The effects of substrate temperature, Ar:O2 mass flow ratio and gas mixture pressure on the films’ microstructure, phase evolution, optic, ferroelectric and magnetic properties were systematically investigated. The structural analysis results revealed an amorphous phase for the films deposited at a substrate temperature below 500 °C, while for the thin films deposited at 700 °C, a ε-Fe2O3 secondary phase was detected. The diffraction lines of the samples deposited at 600 °C were associated with Bi2Fe4O9 and Bi25FeO40 phases. The increase in the mixture gas pressure up to 1 Pa showed an improved crystallinity of the deposited films, while, at higher working gas pressures, the films were found to be amorphous. The use of low O2 to Ar mass flow ratio during the deposition led to a phase transformation process. EDX and RBS measurements exposed a uniform distribution of the main elements, revealing some stoichiometry changes induced by the pressure variation. The optical band gap values were influenced by the substrate temperature and pressure of the Ar:O2 gas. The magnetic properties were correlated with the structural features, the highest magnetic response being observed for the sample deposited at 600 °C, 1 Pa and 3:1 Ar:O2 gas pressure. According to the PFM results, the film deposited at 700 °C, Ar:O2 ratio 3:1 and total gas pressure 1 Pa clearly outperformed the others due to their excellent ferroelectric properties and outstanding piezo-response. The sample deposited at 700 °C showed both visible light-driven degradation and piezodegradation activities. The piezocatalytic and photocatalytic activities were ascribed to the high piezoresponse and to a more efficient separation of electrons and holes induced by a built-in electric field that is caused by the larger remnant polarization of Bi2Fe4O9 and Bi2Fe4O9/ε-Fe2O3 hetero-junction.

Experimental and theoretical research on the debrining process in sediments for a gas storage salt cavern

The sediments account for a large part of the total mined volume of the cavern in high impurity salt mines. This paper was aimed at the scientific problem of gas storage in the pore space of the sediments, and expanded the storage capacity of salt cavern in high impurity salt mines. Debrining in the mined space of salt caverns (contained sediments) is a vital step to complete the gas storage. To experimentally observe the debrining process, debrining experiments are carried out using a self-developed experimental device. The debrining process can be divided into four typical stages, e.g., rapid increase of injection gas pressure, discharging the upper brine, i.e. the brine free of sediments, discharging the brine in sediments, and rapid decrease of injection gas pressure. A mathematical model is proposed for calculating debrining parameters of a salt cavern including sediments based on the pressure equilibrium principle at the gas-brine interface. A numerical method is established for calculating the total debrining time of irregular salt caverns including sediments. The effective cross-sectional area of debrining process is calculated by using the porosity of the sediments. A linear function of the porosity of the transition zone of the sediment surface is put forward. Therefore, the porosity of the upper brine space can gradually transition to the sediments, avoiding the error of sudden increase of the gas-brine interface and debrining rate, which is consistent with the practical debrining process. The porosity of sediments is considered to be a decaying exponential function of depth based on the accumulation of sediment particles. The cross-sectional area at any depth can be obtained through the interpolation of the sonar scanning data. The Jianghan salt cavern is selected for the applications of the proposed model, and the descending speed and depth of the gas-brine interface, and injection gas pressure with debrining time are analyzed. Results show that the greater the debrining rate, the shorter the time to reach the final sediment surface. The descending speed of the gas-brine interface shows a U-shaped curve, which is significantly affected by the cavern shape and porosity of sediments. The increment of the debrining rate has little effect on the ultimate injection gas pressure but has a significant effect on the increasing rate of injection gas pressure. These results can provide a reference for enhancing gas storage by using the sediment pore space of the mined volume and thereby expanding the effective gas storage volume of salt caverns.

Spectral splitting of the lasing emission of nitrogen ions pumped by 800-nm femtosecond laser pulses.

We report on a spectral splitting effect of the cavity-less lasing emission of nitrogen ions at 391.4 nm pumped by 800-nm femtosecond laser pulses. It was found that with the increase of the nitrogen gas pressure and pump pulse energy, both R and P branches experience spectral splitting. With an external injected seeding pulse, a similar split spectral line is observed for the amplified emission. In contrast, for the fluorescence radiation, no such spectral splitting phenomenon is observed with much more abundant R branch structures. Our theoretical model considers gas ionization by the pump pulse, the competition of excitation of all relevant electronic and vibrational states, and an amplification of the seeding pulse in the plasma with a population inversion. Our simulation reproduces this spectral splitting effect, which is attributed to the gain saturation resulting in the oscillation of the amplitude of the amplified signal.

Study on prediction of blasting cracking radius of liquid CO2 in coal.

In this study, we sought to improve the efficiency of coal seam gas extraction, master the characteristics of different factors on the liquid carbon dioxide (CO2) phase change blasting cracking radius, and effectively predict the hole spacing. In this study, we used ANSYS/LS-DYNA numerical simulation software to predict the crack radius of liquid CO2 phase change blasting combined with orthogonal design scheme. The results showed that the primary and secondary factors affecting the fracture radius of liquid CO2 phase change blasting were in ground stress, gas pressure, coal firmness coefficient, and gas content. The fracture radius decreased with the increase of in ground stress and decreased with the increase of gas pressure, coal firmness coefficient, and gas content, which was linear. A prediction model for predicting the cracking radius of liquid CO2 phase change blasting based on four groups of different factors was established. Through the double verification of numerical simulation and field industrial test, the cracking radius of liquid CO2 phase change blasting ranged from 2 m to 2.5 m. The maximum error of numerical simulation was 2.8%, and the maximum error of field industrial test was 5.93%.

Response characteristics of gas pressure under simultaneous static and dynamic load: Implication for coal and gas outburst mechanism

Coal and gas outbursts are dynamic disasters in which a large mass of gas and coal suddenly emerges in a mining space within a split second. The interaction between the gas pressure and stress environment is one of the key factors that induce coal and gas outbursts. In this study, first, the coupling relationship between the gas pressure in the coal body ahead of the working face and the dynamic load was investigated using experimental observations, numerical simulations, and mine-site investigations. It was observed that the impact rate of the dynamic load on the gas-bearing coal can significantly change the gas pressure. The faster the impact rate, the speedier the increase in gas pressure. Moreover, the gas pressure rise was faster closer to the impact interface. Subsequently, based on engineering background, we proposed three models of stress and gas pressure distribution in the coal body ahead of the working face: static load, stress disturbance, and dynamic load conditions. Finally, the gas pressure distribution and outburst mechanism were investigated. The high concentration of gas pressure appearing at the coal body ahead of the working face was caused by the dynamic load. The gas pressure first increased gradually to a peak value and then decreased with increasing distance from the working face. The increase in gas pressure plays a major role in outburst initiation by resulting in the ability to more easily reach the critical points needed for outburst initiation. Moreover, the stronger the dynamic load, the greater the outburst initiation risk. The results of this study provide practical guidance for the early warning and prevention of coal and gas outbursts.

Experimental Study on Mechanical Behavior and Energy Evolution Characteristics of Gas-Filled Deep Coal under Cyclic Loading

To study the mechanical behavior and energy evolution law of gas-filled deep coal, conventional triaxial compression experiments under different confining pressure and gas pressure conditions and cyclic loading and unloading experiments under different gas pressures were carried out. The failure characteristics and mechanical parameters evolution of two loading modes were analyzed. In addition, the energy density and ratio evolution law under cyclic loading was revealed, and based on these findings, an attempt was made to depict the relation of cumulative dissipated energy density and volumetric strain by fitting the experimental data. The results indicated that failure of coal is expressed as a single shear surface under conventional compression, while under cyclic loading mode, coal behaves with multi-fracture crushing failure. Mechanical parameters showed a trend of decay with increasing gas pressure, and that cyclic loading and unloading increases the bearing capacity of coal by 8–38%. The dissipated energy density and ratio grew significantly when coal entered the yield stage. In the compaction stage, the cumulative dissipated energy density rose with volumetric strain in the form of an exponential function, and it increased with relative volumetric strain as a power function.

Формирование плазмы в атмосфере азота импульсным электронным пучком вблизи диэлектрической мишени при форвакуумных давлениях

Features of the processes of beam plasma formation near a dielectric (aluminum oxide ceramic) target being irradiated by an intense pulsed electron beam in the forevacuum pressure range (4–15 Pa) have been investigated. It has been established that the density of the beam plasma near the irradiated dielectric target is higher than in the case of "free" propagation of the electron beam. The observed increase in plasma density depends on the emission current (electron beam current), gas pressure, and accelerating voltage. The influence of the dielectric target on the beam plasma density is due to emission of electrons from the target surface and the uncompensated negative potential on the target surface, which determines the energy of emitted electrons. An increase in gas pressure leads to a smaller increase in the beam plasma density due to a decrease in the absolute value of the negative potential. Varying the electron beam current and accelerating voltage provide to control the beam plasma density.

Study on Dynamic Performance and Induced Breakdown of the Plasma-Triggered-Based Protective Gas Gap Switch

The plasma-triggered-based protective gas switch (PTGS) has obvious advantages in the control switch application of fast energy dissipation device used in the hybrid dc transmission projects. However, the high-pressure environment critically limits the plasma jet ability, easily leading to the trigger failure. Therefore, this article establishes a plasma-jet-triggered experimental platform to study the dynamic performance and induced breakdown laws of PTGS. It is shown that the evolution of plasma jet is divided into three stages: plasma jet of high-pressure, saturated stability, and dissipation. The induced breakdown mainly occurs in the high-pressure jet and saturated stability stage. The initial plasma jet velocity increases, as the energy storage capacitance and the charging voltage increase, making it faster to reach the jet length for induced breakdown, resulting in a significant reduction in switch-on time and improving the PTGS trigger stability. The increase in trigger gas pressure inhibits the plasma jet ability, but improves the electrical strength of PTGS. In order to achieve induce breakdown of PTGS, the plasma jet must reach the critical jet length. SF6 gas improves the insulation strength of PTGS and prevents the formation of plasma jet. To achieve stable trigger conduction, the trigger energy of PTGS must be increased. The findings can be used to develop theoretical guidance for improving the working performance of the high-voltage and large-capacity protective gas gap switches (GGSs).

Temperature and electric field distribution of tri‐post insulator in DC‐GIL based on numerical multiphysics modelling

AbstractThe temperature distribution of the tri‐post insulator in a ±500 kV direct current gas‐insulated transmission lines (DC‐GIL) is investigated. The influence of thermal gradient on the electric field characteristics is investigated as well. A horizontally installed GIL model is applied in the simulation. The thermal and electric parameters of the insulator are measured and employed. The temperature results indicate that the gas shows a layered distribution pattern while the insulator shows a radial distribution pattern. The temperature of the upper post is higher. With increasing ambient temperature, the surface temperature increases linearly following the variation of ambient temperature. With increasing load current, the temperature near the conductor shows an obvious increase. With increasing gas pressure, the temperature decreases due to the promotion of convection. Besides, the electric field strength of the insulator surface increases if the surface temperature increases during the variation of operating conditions. And the peak of field strength moves towards the enclosure. After 10 h, the temperature reaches a quasi‐stationary state. Since the thermal gradient affects the distribution of gas density and electric field strength of the insulator, the investigation of temperature characteristics is necessary when evaluating the insulating performance of DC‐GIL with insulators.

Analisis kualitas pelayanan pada PT Perusahaan Gas Negara tbk, area Karawang

The purpose of this study is to conduct an investigation into the level of service provided by PT. Perusahaan Gas Negara Tbk in the Karawang Area. Participants in this study include both employees and customers. This study employs qualitative research methods that are descriptive. Research focuses on five aspects of Prasuraman's theory: responsiveness (responsiveness), assurance (assurance), tangibility (physical), empathy (empathy), and reliability (reliability). These five aspects are listed as follows: responsiveness, assurance, tangible (physical), empathy (empathy), and reliability (reliability). The data collection method consisted of three stages, which were observation, interviews, and documentation of the results of the interviews. There are obstacles in the Responsiveness dimension, specifically in responding to messages from the community through WhatsApp services, and there are obstacles in the Physical Evidence dimension, specifically in the facility of interference, according to the findings of research related to the five dimensions of service quality. The dimensions of Assurance, Empathy, and Responsiveness all fall into the good category. increased gas pressure, which results in the gas being unstable. The findings of this research provide information that can be used by PT. Perusahaan Gas Negara Tbk, Karawang Area in terms of the quality of service on what dimensions ought to be evaluated so that it can be improved.

Investigation of internal gas pressure and internal temperature of cylindrical Li-ion cells to study thermodynamical and mechanical properties of hard case battery cells

This study is the first to measure the relationship between gas pressure, internal gas temperature and state of charge of cylindrical Li-ion battery cells. For this purpose, a new, simple and affordable setup for in-situ investigation of internal gas pressure and internal temperature of commercial cylindrical Li-ion cells is designed and tested. Setups to investigate the internal gas pressure have so far only been performed on pouch and prismatic cells or require complex and expensive measurement equipment. In this work, the mechanical effects of an increasing gas pressure in cylindrical Li-ion cells are addressed for the first time. It is shown that the measurement of internal gas pressure and internal temperature over multiple charging and discharging cycles is possible. Measurements at different current rates show the dependency of the gas pressure to the total amount of charge transferred and the temperature of the cell. The pressure, which depends on the degree of lithiation of the electrodes, relaxes after the Li-ion cells have been exposed to a high current. Additionally, phases of the phase transition are visible via differential capacity analysis. The differential pressure analysis shows an equivalent trend to the differential capacity. Thus demonstrates the predominant phase transformations, namely the restructuring of lithiated graphite, the lithiation of silicon, and the phase transformation of nickel–cobalt–manganese (NCM) oxide. These effects contribute significantly to the pressure change, as they cause electrode expansion, which results in a reduction of the gas volume of the Li-ion cell, leading to an increase in pressure.

Experiment, Model, and Mechanism of Multiscale Dynamic Diffusion-Permeability in Coal under Different Fluids.

The permeability of coal exhibits multiscale characteristics in space and time, which is caused by the presence of micro and nanopores in coal. Water, free gas, and adsorbed gas are common engineering fluids in coal seams during gas extraction. Thus, it is of significance to study the multiscale characteristics and mechanisms of seepage-diffusion of different fluids in coal for gas extraction engineering. Experiments of seepage-diffusion for He, CH4, and water are carried out using ϕ50 × 100 mm cylindrical coal. It is found that the apparent diffusion coefficient for He, CH4, and water are not a constant but a variable that decays dynamically with time. The phenomenon is independent of fluid properties and determined only by the multiscale characteristics of pores in coal, and then a novel model of multiscale dynamic apparent diffusion that can accurately describe the full-time process of flow in various fluids is proposed. The mechanism of dynamic seepage-diffusion for different fluids in coal is elucidated based on a new proposed geometrical model of multiscale pores. At the early stage of flow, fluids first flow in or out of the largest pores outside coal, and at the later stage of flow, fluids flow in the micro and nanopores inside the coal matrix. The pore sizes through which the fluid flows decrease with time, which leads to a dynamic attenuation of the apparent diffusion-permeability with time. The initial apparent permeability K 0 for He/CH4 shows a "U"-shaped pattern of decreasing and then increasing with the decrease of gas pressure. When the gas pressure is lower than the turning point, the slip effect dominates, making the initial apparent permeability K 0 decrease with the increase of gas pressure. When the gas pressure is higher than the turning point, the effect of the pressure difference of the gas dominates, and K 0 increases with the increase of gas pressure. When water flows in multiscale pores, it occupies the space of large pores, making the homogeneity of pores increase, and the decay coefficient of apparent permeability becomes smaller. The multiscale permeability can explain the reason for the rapid attenuation of coalbed methane production in the late stage. It is of great significance for coalbed methane productivity prediction.

Realization of the triple point of carbon dioxide in a transportable cell using long-stem SPRTs

The action of the Minamata Convention requests in the near term to develop alternative fixed points to replace the mercury triple point (Hg TP) from the set of the defining points of the International Temperature Scale (ITS) of 1990. Carbon dioxide (CO2) TP is a candidate that exhibits the advantages of high chemical and physical stability and low health risk, and the disadvantage of relatively high pressure at room temperature. We report our study on the realization of the CO2 TP using long-stem standard platinum resistance thermometers (SPRTs). We present a novel design for a CO2 TP cell with thermometer immersion depth extending from 110 –200 mm with no increase in sample gas pressure. The outer dimension of the new cell is suitable for a drop-in compatible replacement of a normal cell for the Hg TP. We realized 14 plateaus of the CO2 TP using two long-stem SPRTs over a span of 12 months. The mean temperature at the CO2 TP is 216.591 30 (36) K at the melt fraction F = 0.5 and 216.591 36 (37) K at F = 1.0. Within the given uncertainties, the uncertainty arising from the transformation to ITS-90 contributes a major part of 0.29 –0.30 mK. The uncertainty formed by the pressure-head effect and the axial heat leak through the thermometer well of the new cell, the impurities of the sample gas and the inaccuracy of the electronic instruments contribute a smaller part of 0.21 –0.22 mK. The plateaus consistently exhibit small slopes of heights of less than 0.21 mK and time spans from 147 –347 h between F = 0.3 and F = 0.75. The small slopes of the plateaus demonstrate the repeatability of 0.056 and 0.059 mK, respectively, for the melt fraction F = 0.5 and 1.0, and the long-term stability of 0.031 mK.

Effect of Cetane-Coupled Pilot Injection Parameters on Diesel Engine Combustion and Emissions.

The effects of cetane number (CN) coupled with pilot injection ratio and pilot injection timing on the combustion and emission characteristics of a four-cylinder diesel engine were investigated. The results showed that as the pilot injection ratio increases, the peak cylinder gas pressure (CGP) increases, and the peak of heat release rate (HRR) increases accordingly; the coupled CN increases, the brake specific fuel consumption (BSFC) decreases, and the brake thermal efficiency (BTE) increases; CO and HC emissions increase; and NO x emissions increase. In addition, the number concentration and total mass of particulate matter (PM) decrease with the increasing pilot injection ratio. Only when the pilot injection ratio reaches 20% does the fuel produce pilot injection heat release. The ignition delay time (ID) and combustion duration (CD) are redefined for the pilot injection heat release operating conditions. With the delay of the pilot injection timing, the peak CGP increases, the coupled CN increases, the BTE increases, the BSFC decreases, CO and HC emissions increase, and NO x emissions decrease. With the delay of the pilot injection timing, the number concentration and total mass of PM decrease. In addition, no pilot injection heat release was generated for any of the five fuels at pilot injection timings from 30°CA BTDC to 45°CA BTDC.

Emission induced by interaction between nitrogen molecules and electronic excitations of α-quartz single crystal

The spectral and kinetic characteristics of emission in the region of 300–380 nm caused by photoexcitation of α-quartz single crystal placed into gases of N2 molecules, He atoms and atmospheric air are studied. It is found that the interaction between electronic excitations (EE) created in α-quartz by the two-photon absorption at 205 nm with surrounding N2 molecules leads to emission of a complex “α-quartz surface – N2 molecule”. This fact is proved, particularly, by the growth in the radiant energy of studied emission correlated with the increase in the N2 gas pressure in the region of 0.1–200 Torr. Simultaneously, the spectral energy distribution of the emission as a function of wavelength differs from that for a free N2 molecule. This result shows that the electronic-vibrational states of N2 molecules are significantly distorted due to interaction with α-quartz surface. The results are explained by excitation of the intercombinational X1Σg+→ C3Πu transition of N2 molecules induced by the energy transfer from the EEs in α-quartz and subsequent short-term chemical bond formation between the excited N2 molecules and the α-quartz surface.

Experimental research on adsorption characteristics of N2, CH4, and CO2 in coal under different temperatures and gas pressures

AbstractThe coal deformation was induced by the gas adsorption of N2, CH4, and CO2. However, the differences between different gas adsorption performances and the deformation mechanism of coal need to be further studied. In this study, the experiments were conducted using self‐developed equipment to reveal the adsorption characteristics of different gases. The results showed that the gas adsorption capacity followed the sequence of CO2 > CH4 > N2. The gas adsorption capacity was negatively correlated with temperature. The maximum decrease in adsorption capacity (23.70%) was N2. The gas adsorption capacity was positively correlated with gas pressure. The maximum increase in gas adsorption capacity (232.79%) was N2. Correspondingly, the coal deformation of CO2 was the largest, and that of N2 was the smallest. The maximum decrease in deformation (31.09%) was CO2 during the temperature increase. The initial coal deformation rates of N2, CH4, and CO2 were 0.060, 0.091, and 0.042 mm·h−1, respectively. The maximum increase of deformation (234.65%) was CH4 with the gas pressure increase. The initial coal deformation rates of N2, CH4, and CO2 were 0.024, 0.045, and 0.016 mm·h−1, respectively. This work guided further clarifying the mechanism of different gases' adsorption capacity and coal deformation.

Effect of Internal Moisture and Outer Relative Humidity on Concrete Carbonation

With steadily rising CO2 concentrations in the ambient air and fast-changing concrete compositions with reduced clinker contents, the availability of reliable and accelerated concrete carbonation tests is of crucial importance to design durable structures. This paper focuses on the effects of moisture under accelerated conditions and the effects of different CO2 exposure conditions. Mortar prisms incorporating three different cement types were cured and stored at either 50% or 65% relative humidity (RH). Afterwards, the prisms were carbonated at different ambient humidities (50, 57 and 65%), different CO2 concentrations (0.04, 1 and 3 vol.%) and complemented by a series of tests at increased gas pressure (2 barg). High-resolution test methods were used to explain the underlying carbonation mechanisms. The results show that pre-conditioning for two weeks—as currently suggested by the European Standard—seems to be too short because the initial inner moisture content severely affects the carbonation rate. Relative humidity during carbonation of 57% led to higher carbonation rates compared to 50% and 65%. In addition, climate data needs to be periodically (preferably permanently) recorded in research experiments and in laboratory testing to ensure fair interpretation of experimental results.

Experimental study on the influence of gas pressure on CH4 adsorption-desorption-seepage and deformation characteristics of coal in the whole process under triaxial stress

CH4 adsorption-desorption-seepage characteristics of coal is an important indicator to measure the gas extraction capacity of coal seam. The deformation of coal caused by CH4 adsorption-desorption-seepage is an important factor affecting the extraction ability of CH4. Synchronous test experiments of CH4 adsorption-desorption-seepage and whole-process coal deformation under different gas pressures were carried out by using the self-developed comprehensive test experimental system of gas-solid coupling for coal measure gas. The timeliness characteristics of CH4 adsorption-desorption-seepage and coal deformation were analyzed. The influence of gas pressure on CH4 adsorption-desorption-seepage and coal deformation was clarified. The quantitative relationship between CH4 adsorption-desorption-seepage and coal deformation was discussed. A whole-process strain model of coal for CH4 adsorption-desorption-seepage was established. The results showed that increasing gas pressure could promote CH4 adsorption-desorption-seepage of coal. The higher the gas pressure was, the greater the capacity of CH4 adsorption-desorption-seepage in coal was. Increasing gas pressure could promote the expansion/contraction deformation caused by CH4 adsorption-desorption-seepage in coal. The higher the gas pressure was, the stronger the deformation ability of CH4 adsorption-desorption-seepage in coal was. The expansion or contraction deformation caused by CH4 adsorption-desorption-seepage in coal was simultaneously affected by coal bedding structure and external stress. The axial/circumferential strain caused by CH4 adsorption-desorption-seepage in coal showed exponential function, quadratic function, and exponential function growth relationship with adsorption capacity, desorption capacity, and seepage capacity of CH4, respectively. The stress in the process of CH4 adsorption-desorption-seepage in coal covered the expansion stress of adsorbed CH4 to coal matrix, the compression stress of free CH4 to coal matrix, and the expansion stress of free CH4 to coal microporous fracture. Considering three kinds of deformation effects by CH4 in two states, the whole process strain model of CH4 adsorption-desorption-seepage in coal was established, which could effectively reflect the deformation timeliness characteristics of the whole process of CH4 adsorption-desorption-seepage in coal. This research provides some theoretical support for the efficient extraction of coal seam gas.

Профилирование торцевых окон трохоидной машины

There is a proposal of a method for the profiling the end windows of trochoid rotary machines according to the given geometric parameters for constructing the trochoid and the degree of gas pressure increase. Its area of application is rotary piston engines and trochoid compressors and pumps. Verification of the mathematical model was carried out on the basis of gas flow simulation data in a three-dimensional setting in the AVL Fire software package. The model of the working process of a trochoid machine is based on the fundamental equations of momentum, energy, diffusion and continuity, written in the Reynolds form and supplemented by the k–?–f turbulence model. The developed method makes it possible to estimate quickly the throughput of the windows of a trochoid rotary machine with less computing resources than in a three-dimensional calculation.

Study on the Differences between Various Gas Injection Sources in the Process of Coal Seam Methane Replacement by Gas Injection.

To study the differences between various gas injection sources in the process of coal seam methane replacement, experimental research was conducted to study the influences of different gas injection sources and gas injection ratios on coal seam methane replacement by considering the strong adsorption gas CO2 and the weak adsorption gas N2. The experimental results show that the temperature rise effect of the CO2 injection gas is greater and lasts longer than that of the N2 injection gas in the process of coal seam methane replacement by gas injection, and the temperature rise can promote the desorption of adsorbed methane well. However, due to the different effects of gas compressibility, the increase in gas pressure caused by injecting N2 under the same conditions is higher than that of CO2; due to the strong adsorption of CO2, the gas pressure after injecting CO2 continues to decrease slowly. From the displacement effect, the adsorbability of the injection source gas has a significant effect on the displacement rate and injection-placement ratio, while the injection ratio has a significant effect on CO2 displacement but not on N2 injection. From the experimental results, for N2 injection, the effects of coal seam methane replacement by gas injection can be enhanced by improving the gas injection method and process; for CO2 injection, the effects of coal seam methane replacement by gas injection can be improved by the following two aspects: gas injection volume and gas injection time.