Single-phase Gas Research Articles

Image Charge effect on Metallic Particle Movement in a single phase Gas Insulated Bus Duct with Dielectric Coated Enclosure

Image Charge effect on Metallic Particle Movement in a single phase Gas Insulated Bus Duct with Dielectric Coated Enclosure

The impact of Particle on FGM insulator in a single phase gas insulated busduct on electric field stress

The impact of Particle on FGM insulator in a single phase gas insulated busduct on electric field stress

Study on the coupling model of wellbore temperature and pressure during the production of high temperature and high pressure gas well

During the production process of high temperature and high pressure gas well, high temperature fluids are produced from the formation. The change of wellbore temperature and pressure, due to the change of production, has an important impact on the production tubular column, which threatens the safety of the completion tubular column and the integrity of the wellbore. A single-phase gas transient flow temperature–pressure​ coupling mathematical model is developed for the fluid in the tubular column during gas well production, and the pressure and temperature distribution patterns of the gas in the tubular column during gas well production are obtained, and the influence of production rate on the temperature–pressure distribution in the tubular column during gas well production is analyzed. The coupled temperature–pressure model takes into account the mutual influence of temperature and pressure during the transient flow of gas in the column, and the comparison with the measured data in the field and the calculation results of the analytical model shows that the coupled model has higher accuracy. The model will provide theoretical support for the selection and optimal design of completion production tubular tools.

High temperature oxidation behavior of aluminide coatings applied on HP-MA heat resistant steel using a gas-phase aluminizing process

Aluminide diffusion coatings were applied on a high-performance micro-alloyed (HP-MA) heat resistance steel, using a single step gas-phase aluminizing process. Powder mixtures with different compositions were employed for the coating process to achieve low-Al and high-Al coatings. This paper investigates the phase composition, growth mechanism, as well as high temperature oxidation behavior of aluminide-coated HP-MA steels. X-ray diffraction (XRD), scanning electron microscope (SEM), and field emission scanning electron microscopy (FESEM) were used to investigate characteristics of coated specimens. To evaluate the oxidation behavior, specimens were heated to 1100 °C for 100 h in the air atmosphere. Weight measurements were conducted at regular ten-hour time intervals. Furthermore, the parabolic rate constant (kp) values were obtained from the (ΔW/A) vs. oxidation time graphs. Moreover, stresses generated in oxide scale, formed on the aluminide coatings, were theoretically calculated following the first cycle of oxidation. Results showed that the stresses created in the oxide scale exceed the compressive strength of alumina, resulting in its spallation. After 100 h of cyclic oxidation test, the thickness of the oxide scale for the HP-MA steel, low-Al, and high-Al aluminide coated specimens was 22, 14, and 6 μm, respectively. The oxidation behavior of all specimens followed the parabolic rate law. The value of kp was the lowest at all oxidation time intervals for the coatings with higher Al content. This was due to the presence of more Al and Cr elements in the high-Al aluminide coating, improving the ability to form an outer dense alumina layer.

Measurement of Oil–Gas–Water Flows in Vertical Pipes Using Electromagnetic Flowmeter and Dual-Conductance Sensors

Three-phase flows are significantly complicated in comparison to single-phase flows and gas–liquid two-phase flows. So far, faced with the presence of two nonconductive dispersed phases in oil–gas–water three-phase flows, the measurement characteristics of electromagnetic flowmeter (EMF) in three-phase flows are an unresolved problem. The flowrate of three-phase flows is difficult to measure due to the nonuniformity arising from interactions between dispersed phases. Aiming at the difficult problem of production logging in oil wells of three-phase flows, this article reports an experimental study on measuring three-phase flows via the EMF and the dual-conductance sensors. Among them, the phase holdups of three-phase flow in vertical pipe are extracted through newly designed distributed coaxial double-ring conductance sensor (DRCS) and rotating electric field conductance sensor (REFCS). A three-phase flow loop test in a pipe of 20 mm inner diameter is carried out. The results show that the EMF has the ability to substantively measure the flowrate of water phase under three flow patterns (bubble, slug, and churn flows) when the water cut is above 60%, and the average absolute percentage deviation (AAPD) for prediction of superficial water velocity is 3.55%. The measurement of superficial gas and oil velocities is implemented by solving the drift-flux models of three-phase flow based on the phase holdups and superficial water velocity, and the AAPDs for predictions of superficial gas and oil velocities are 4.33% and 5.95%, respectively. This research provides a new measurement strategy for production logging of oil, gas, and water three-phase flow production profile by combining the EMF with dual-conductance sensors.

Dielectric withstand capability of functionally graded material disc insulator in single phase - gas insulated busduct

Regardless of the environment, electrical substations must be secure and efficient, and they must also be able to recover rapidly from any damage they suffer. Metal inserts at the conductor end of a single-phase gas insulated busduct (GIB) are shown to minimise stress in FGM insulator and to assess stress on a Triple Junction. Functionally graded materials are spatially scattered with several filler materials and doped with varying permittivity values in order to create homogeneous electrical field stress.Various voltages and grades of FGM are used in the simulation, as well as the insulator. The effect of grading on electrical field stress is further decreased by inserting the Metal Insert into the FGM insulator. The suggested insulator's efficiency is demonstrated by the findings gathered and examined.

Calculation of depressurization coordinate in underground and offshore gas pipelines

The paper introduces a method for calculating the depressurization coordinate of an extended ultra-high pressure gas pipeline from the data measurements of pressure and flow rate at the outlet. The method is based on a mathematical model of a non-isothermal steady single-phase gas mixture flow through a pipeline of constant section on the quasi-linearization method. It allows to calculate the depressurization coordinate for extended underground and offshore ultra-high pressure gas pipelines with high accuracy, while considering varying leakage size and location. Examples of solving problems of practical interest are given. The influence of the flow rate and pressure settings error on the coordinate of depressurization calculating error has been demonstrated.

Resonantly Enhanced Difference-Frequency Generation in the Core X-ray Absorption of Molecules.

We use real-time time-dependent density functional theory simulations to numerically demonstrate that resonantly enhanced difference-frequency generation (re-DFG) involving intense ultrashort coherent X-ray pulses can selectively excite core states of atoms in molecules. As a model case, we evaluate the spectral selectivity of re-DFG excitation of the oxygen K-edge by illumination of a single gas-phase water molecule with two-color X-ray pulses of different photon energies and durations. The re-DFG excitation is further probed by a small delayed pulse with central photon energy resonant with the oxygen K-edge peak absorption line. Based on these results, we anticipate that highly selective excitation by re-DFG X-ray nonlinear processes might be achieved in more complex molecular systems and bulk materials by using highly penetrating two-color hard X-ray pulses, with extensive applications.

Relative permeability measurement of coal microchannels using advanced microchip technology

The gas–water flow in coal cleats is an important factor affecting coalbed methane production. However, difficulties are often encountered in the prediction of gas production. Limited understanding of two-phase flow behaviour in microchannels reduces prediction accuracy, often leading to overestimation. In this study, based on micro-computed tomography, advanced microchip technology is used to predict the optimal coal cleat in the polydimethylsiloxane chip. Gas and liquid injection experiments are carried out on the microchannels through the syringe pumps, as the two-phase flow morphology in the system can obtain flow information that cannot be provided by conventional laboratory measurements. The flow capacities of single-phase gas, water, and wetting liquid in the microchannels are compared, alongside determining the flow laws under different wettability and flow rates. The results show that in the single-phase fluid injection experiment, gas is more sensitive to the microchannel size effect than the liquid phase, and hydrophilic liquids flow readily. The gas–water relative permeability value in this study is significantly smaller than that obtained from conventional experiments, based on the steady-state method. This is a result of the gas–water forming a discontinuous plug flow in the microchannel, which produces higher resistance and reduces flow capacity. The occurrence of discontinuous flow regimes challenges the laminar flow assumption adopted in the steady-state method and suggests that conventional laboratory measurements of relative permeability measurements may misrepresent the physics of fluid flows in microchannels. The results also reveal that a hydrophilic environment and a suitable flow rate can increase the two-phase relative permeability. The results of this study enhance our understanding of and approach to core flooding measurement, with the differences in the relative permeability curves indicating that data uncertainty associated with the steady-state method is worthy of further research.

Experimental research and simulation of two-phase plume for R134a release and diffusion

The frequent occurrence of Liquefied natural gas (LNG) leakage accidents has caused serious economic loss and environmental damage. Therefore, it's of great significance to make assessments on the LNG hazards during its accidental release and associated consequences. This paper focuses on the two-phase release process in the liquefied gas release and dispersion accident and makes investigatatation on the two-phase plume with experimental and numerical approaches. A small-scale experimental system is developed with different sizes of release holes. With the experiment results, the mass outflow rate and temperature have been obtained, which provided initial parameters for the simulation. Jet velocities have been measured by PIV, and results reveal that an obvious velocity breach existing near the leakage nozzle due to the Joule-Thomson effect. Besides, given a point in the X-axis, the jet velocity is decreasing with an increasing diameter hole. Subsequently, the experimental data are utilized to verify the liquid-gas phase numerical model using Eulerian-Lagrange approach. Comparing with the results obtained by single gas phase model, the velocities obtained by liquid-gas phase model show good consistency with the experiments. Afterwards, the validated numerical liquid-gas phase model is employed to analyze the temperature distribution, concentration distribution and droplet size distribution in the near-source release region. With the simulation results, it depicts that there is a violent temperature decrease near the leakage nozzle in the liquid-gas phase model, which was caused by the evaporation of droplets. Meanwhile, concentration of R134a simulated by liquid-gas phase model is higher than the value of single-gas phase. These results emphasize that it’s essential to simulate the release accidents with liquid-gas phase model, especially in the near-source region. Both the experiments and numerical models are of great value for providing assessments and theoretical supports for the risk consequences in the process safety.

An experimental study of the optimal drainage working system in the single-phase gas flowing stage of coalbed methane wells

Accurately determining the optimal drainage system in the single-phase gas flow stage of coalbed methane (CBM) wells is important when trying to guarantee maximization of gas production. By using a self-made physical simulation device for stress–permeability–cumulative gas production, tests on continuously exponential and wave trough-type cumulative gas production under four drainage systems and different permeabilities were performed. The four working systems involve a stepped wave trough, stepped wave crest, stepped decline, and a stepped increase. On this basis, the optimal drainage system in the single-phase gas flow stage at different permeabilities of coal seams was determined and the associated permeability–drainage rate–drainage time chart was established. The results show that there is high cumulative gas production under the drainage system with the drainage rate that first decreases, then increases. The initial pressure difference, acceleration/deceleration coefficient of pressure difference and rate of change of effective stress jointly influence the cumulative gas production. For low-permeability coal samples, decreasing the acceleration/deceleration coefficient of pressure difference weakens the influence of the negative effect of effective stress and thereby leads to high cumulative gas production. For high-permeability coal samples, increasing the initial pressure difference and acceleration/deceleration coefficient of pressure difference shortens the time of action of the negative effect of effective stress, thereby resulting in high cumulative gas production. The research results provide a method of optimizing the drainage system in the single-phase gas-flow stage in CBM wells at different permeabilities.

Insights on the interaction of serpentine channels and gas diffusion layer in an operating polymer electrolyte fuel cell: Numerical modeling across scales

Three-dimensional direct numerical simulations were performed for investigating the flow in a serpentine channel and the under-laying porous gas diffusion layer (GDL) of a micro polymer electrolyte fuel cell (PEFC). The flow field comprised three straight sections and two U-turns. The geometry was acquired with high-resolution (2.9 μm) in situ X-ray tomographic measurements on an operating cell. Simulations considered the GDL under dry and partially saturated conditions, whereby saturation was established via electrochemically produced water. A lattice Boltzmann (LB) methodology was adopted for simulating the single-phase (gas) transport in the actual 3D channel and porous GDL geometry. The global pressure drop in the dry GDL was dominated by the turns in the gas channel, while the pressure drops were quite small along the straight channel sections. In the wet GDL case, however, the pressure drop was mainly dictated by the neck-shaped passages created by the large water clusters inside the channel. Owing to the water blockage, the local accumulated cross-flows along the serpentine channel length, when normalized by the inlet channel flow, were substantially higher in the wet GDL, reaching local values up to 45% compared to 18% for the dry GDL. The implications are that in an electrochemically operating cell, the GDL under the rib would receive more gas (and thus O2). The creation of cross-flows through the porous GDL would enhance cell performance under the ribs since diffusion will not be the main driving mechanism for oxygen transport and water evaporation. The analysis indicated that the flow field, although designed as serpentine, behaved like half-interdigitated (with a rib of 1.5 mm, half-serpentine flow field, depending on the state of channel flooding).

Transport Model for Gas and Water in Nanopores of Shale Gas Reservoirs

Because of the many nanoscale pores in shale gas reservoirs (SGRs), the fluid transport mechanisms in shale are complex. Also, previous research has shown that there exists water in the shale plays. Hence, two-phase gas-water transport model construction becomes very important so as to increase accuracy in numerical simulation work. However, most of the current study is still focused on single-phase gas transport. In this paper, based on the second slip model coupled with the fluid single-pipe flow equation, the Knudsen and surface diffusions, and combined with the fractal theory, the relative permeability model for gas-water in shale was constructed. The model reliability was proven by using the available two-phase gas-water relative permeability data. A sensitivity analysis has been carried out based on the proposed model. The results show that with the pressure decreasing, the relative permeability of gas increases. The increase of the pore size distribution fractal dimensions (Df) and fractal dimension (DT) caused the gas relative permeability (Krg) to increase. The Krg increases with the increase of Df and DT. The influence of the viscous slip flow, Knudsen diffusion, and surface diffusion are trade-offs, which are mainly controlled by water saturation (SW) and pressure (P). The Krg is extremely sensitive when P<1 MPa. Under low pressure and low water saturation, the effect of viscous slip flow is secondary. And its contribution increases gradually and becomes the main role with the increase of water saturation or pressure. The effect of the Knudsen diffusion is negligible when P>1 MPa and the water saturation SW>40%. However, it cannot be ignored under other conditions. The influence of surface diffusion reached 21.64%–72.78% when P<1 MPa and SW<10%. A surface diffusion contribution of less than 4.25% was obtained when P>1 MPa and SW>70%.

Behavior of S, SO, and SO3 on Pt (001), (011), and (111) surfaces: A DFT study.

In the hybrid sulfur (HyS) cycle, the reaction between SO2 and H2O is manipulated to produce hydrogen with water and sulfuric acid as by-products. However, sulfur poisoning of the catalyst has been widely reported to occur in this cycle, which is due to strong chemisorption of sulfur on the metal surface. The catalysts may deactivate as a result of these impurities present in the reactants or incorporated in the catalyst during its preparation and operation of the HyS cycle. Here, we report a density functional theory investigation of the interaction between S, SO, and SO3 with the Pt (001), (011), and (111) surfaces. First, we have investigated the adsorption of single gas phase molecules on the three Pt surfaces. During adsorption, the 4F hollow sites on the (001) and (011) surfaces and the fcc hollow site on the (111) surface were preferred. S adsorption followed the trend of (001)4F > (011)4F > (111)fcc, while SO adsorption showed (001)4F > (011)bridge/4F > (111)fcc and SO3 adsorption was most stable in a S,O,O bound configuration on the (001)4F > (011)4F > (111)fcc sites. The surface coverage was increased on all the surfaces until a monolayer was obtained. The highest surface coverage for S shows the trend (001)S = (111)S > (011)S, and for SO it is (001)SO > (011)SO > (111)SO, similar to SO3 where we found (001)SO3 > (011)SO3 > (111)SO3. These trends indicate that the (001) surface is more susceptible to S species poisoning. It is also evident that both the (001) and (111) surfaces were reactive toward S, leading to the formation of S2. The high coverage of SO3 showed the formation of SO2 and SO4, especially on the (011) surface. The thermodynamics indicated that an increased temperature of up to 2000K resulted in Pt surfaces fully covered with elemental S. The SO coverage showed θ ≥ 1.00 on both the (001) and (011) surfaces and θ = 0.78 for the (111) surface in the experimental region where the HyS cycle is operated. Lower coverages of SO3 were observed due to the size of the molecule.

Pressure Drops in Two-Phase Gas–Liquid Flow through Channels Filled with Open-Cell Metal Foams

This paper describes experimental investigations of single-phase and two-phase gas–liquid flow through channels with a diameter of 20 mm and length of 2690 mm, filled with metal foams. Three types of aluminium foams with pore densities of 20, 30 and 40 PPI and porosities ranging from 29.9% to 94.3% were used. Air, water and oil were pumped through the foams. The tests covered laminar, transitional and turbulent flow. We demonstrated that the Reynolds number, in which the hydraulic dimension should be defined based on foam porosity and pore diameter de = ϕdp/(1 − ϕ), can be used as a flow regime assessment criterion. It has been found that fluid pressure drops when flowing through metal foams significantly depends on the cell size and porosity of the foam, as well as the shape of the foam skeleton. The flow patterns had a significant influence on the pressure drop. Among other things, we observed a smaller pressure drop when plug flow changed to stratified flow. We developed a model to describe pressure drop in flow through metal foams. As per the proposed methodology, pressure drop in single-phase flow should be determined based on the friction factor, taking into account the geometrical parameters of the foams. We propose to calculate pressure drop in gas–liquid flow as the sum of pressure drops in gas and liquid pressure drop corrected by the drop amplification factor.

STUDY OF THE INFLUENCE OF CONSTRUCTION AND MODE PARAMETERS ON THE HYDRODYNAMICS OF A HOLLOW VORTEX APPARATUS

The research was to determine the more efficient design of the swirler from the point of view of hydrodynamics and heat and its optimal parameters. Various swirl designs were manufactured and tested. After preliminary studies conducted on a laboratory installation with a glass working apparatus, several swirlers were selected taking into account their hydraulic resistance, the structure of the swirling gas-liquid flow, and the amount of liquid entrainment by gas. The results of an experimental study of the hydrodynamics of a hollow vortex apparatus with one and two tangential and axial swirlers. Hydraulic losses in the channel and in the swirls during the direct downward movement of gas and gas-liquid flow are determined. In addition, studies of the hydraulic resistance of a vortex-type device allow us to determine the energy consumption of this device for conducting complex processes of dust collection and absorption or contact heat exchange. The hydraulic resistance in the presence of a liquid film is higher than in the case of a single-phase gas flow. The pressure drop in the studied vortex apparatus does not exceed the resistance of high-performance cyclones and vortex-type devices of other designs. The effect of the twist coefficient of gas swirlers, gas velocity, and liquid flow on the pressure drop in the vortex apparatus is established

Pore-Scale Perspective of Gas/Water Two-Phase Flow in Shale

SummaryThe transport behaviors of both single-phase gas and single-phase water at nanoscale deviate from the predictions of continuum flow theory. The deviation is greater and more complex when both gas and liquid flow simultaneously in a pore or network of pores. We developed a pseudopotential-based lattice Boltzmann (LB) method (LBM) to simulate gas/water two-phase flow at pore scale. A key element of this LBM is the incorporation of fluid/fluid and fluid/solid interactions that successfully capture the microscopic interactions among phases. To calibrate the model, we simulated a series of simple and static nanoscale two-phase systems, including phase separation, a Laplace bubble, contact angle, and a static nanoconfined bubble. In this work, we demonstrate the use of our proposed LBM to model gas/water two-phase flow in systems like a single nanopore, two parallel nanopores, and nanoporous media. Our LBM simulations of static water-film and gas-film scenarios in nanopores agree well with the theory of disjoining pressure and serve as critical steps toward validating this approach. This work highlights the importance of interfacial forces in determining static and dynamic fluid behaviors at the nanoscale. In the Applications section, we determine the water-film thickness and disjoining pressure in a hydrophilic nanopore under the drainage process. Next, we model water imbibition into gas-filled parallel nanopores with different wettability, and simulate gas/water two-phase flow in dual-wettability nanoporous media. The results showed that isolated patches of organic matters (OMs) impede water flow, and the water relative permeability curve cuts off at water saturation [= 1–volumetric total organic carbon (TOC)]. The residual gas saturation is also controlled by the volumetric TOC, ascribed to the isolation of organic patches by the saturating water; therefore, the gas relative permeability curve cuts off at water saturation (= 1–volumetric TOC).

Implementation of a CFD model for wall condensation in the presence of non-condensable gas mixtures

In this paper, we discuss a CFD model to predict vapor condensation on walls in the presence of non-condensable gases, with a specific focus on large scale applications, such as accidental flows in a nuclear reactor containment. It is conclusive from the previous works that the heat and mass transport resistance due to the diffusion boundary layer in the gas phase overwhelms the liquid film thermal resistance. Therefore, the two-phase wall condensation phenomenon is treated with a single-phase (gas) model. For the numerical implementation, the containmentFOAM CFD package, based on OpenFOAM is used. For the first time, the model implementation is discussed for arbitrary multi-component mixtures, and performances of two commonly used approaches – Volumetric source terms and Face-fluxes – are compared; the Face-flux model proved to be more accurate, computationally cheaper, and less grid-dependent. Concluding, the Face-flux approach was validated against the experimental database for forced convection flows, obtained at the SETCOM facility in Forschungzentrum Jülich, Germany. The results demonstrate the model’s predictiveness and robustness for a wide range of cases in the forced convection regime.

Application of Phase Change Tracking Approach in Predicting Condensate Blockage in Tight, Low, and High Permeability Reservoirs

Prediction of the timing and location of condensate build-up around the wellbore in gas condensate reservoirs is essential for the selection of appropriate methods for condensate recovery from these challenging reservoirs. The present work focuses on the use of a novel phase change tracking approach in monitoring the formation of condensate blockage in a gas condensate reservoir. The procedure entails the simulation of tight, low and high permeability reservoirs using global and local grid analysis in determining the size and timing of three common regions (Region 1, near wellbore; Region 2, condensate build-up; and Region 3, single-phase gas) associated with single and two-phase gas and immobile and mobile gas condensate. The results show that permeability has a significant influence on the occurrence of the three regions around the well, which in turn affects the productivity of the gas condensate reservoir studied. Predictions of the timing and location of condensate in reservoirs with different permeability levels of 1 mD to 100 mD indicate that local damage enhances condensate formation by 60% and shortens the duration of the immobile phase by 45%. Meanwhile, the global change in permeability increases condensate formation by 80% and reduces the presence of the immobile phase by 60%. Finally, this predictive approach can help in mitigating condensate blockage around the wellbore during production.

Investigation on the characteristics of single-phase gas explosion and gas-coal dust coupling explosion in bifurcated tubes

In order to deeply understand the overpressure propagation characteristics of explosion shock wave of single-phase gas explosion and gas-coal dust coupling explosion in bifurcated tube, this paper makes a comprehensive and in-depth study on the change and distribution law of explosion shock wave overpressure of single-phase gas explosion and gas-coal dust coupling explosion in bifurcated tube by means of experimental research, the results show that: the explosion shock wave overpressure of single-phase gas explosion and gas-coal dust coupling explosion is all affected by the bifurcation angle of the tube, the larger the bifurcation angle of the tube is, and the greater the explosion shock wave overpressure is. In terms of explosion shock wave overpressure distribution, single-phase gas explosion and gas-coal dust coupling explosion show a similar overall development trend, and the maximum explosion shock wave overpressure is obtained in front of the bifurcation point. The mutation coefficients of explosion shock wave overpressure of single-phase gas explosion and gas-coal dust coupling explosion before and after the bifurcation point of the tube are all affected by the bifurcation angle of the tube. In the straight tube section, the mutation coefficient of explosion shock wave overpressure increases gradually with the increase of the bifurcation angle of the tube, while the situation in the inclined tube section is just the opposite. Under the condition of the same bifurcation angle, the shock wave overpressure mutation coefficient of gas-coal dust coupling explosion is smaller than that of single-phase gas explosion.