Vortex Gas Research Articles

Gas–liquid two‐phase flow characteristics of the jet vortex drainage gas production tool based on computational fluid dynamics

AbstractThis study is aimed at the problems of traditional vortex tools in gas wells, including notable pressure losses and short effective distances. An organic combination of jet vortex drainage and gas production tools was designed and installed without additional power equipment. Based on the liquid film force balance model, gas–liquid two‐phase flow and turbulence models of the jet vortex tool were established with UG and Fluent flow simulation software. The gas–liquid mixture was analyzed before and after the jet vortex tool, and the flow trajectory, pressure loss, liquid volume fraction change, and change rate were examined. According to the simulation results, the comprehensive influence of each structural parameter on the effective working distance was optimized, and optimal structural parameters of the jet vortex tool were obtained. The results indicate that the jet vortex tool reduces the critical liquid‐carrying flow rate and pressure loss and increases the axial and initial velocities of the gas and liquid phases, combined with swirl tool distance model, the effective flow distance is increased correspondingly, and the liquid‐carrying capacity of the gas well is improved.

Decaying quantum turbulence in a two-dimensional Bose-Einstein condensate at finite temperature

We numerically model decaying quantum turbulence in two-dimensional disk-shaped Bose--Einstein condensates, and investigate the effects of finite temperature on the turbulent dynamics. We prepare initial states with a range of condensate temperatures, and imprint equal numbers of vortices and antivortices at randomly chosen positions throughout the fluid. The initial states are then subjected to unitary time-evolution within the c-field methodology. For the lowest condensate temperatures, the results of the zero temperature Gross--Pitaevskii theory are reproduced, whereby vortex evaporative heating leads to the formation of Onsager vortex clusters characterised by a negative absolute vortex temperature. At higher condensate temperatures the dissipative effects due to vortex--phonon interactions tend to drive the vortex gas towards positive vortex temperatures dominated by the presence of vortex dipoles. We associate these two behaviours with the system evolving toward an anomalous non-thermal fixed point, or a Gaussian thermal fixed point, respectively.

Numerical Investigation on Bubble Distribution of a Multistage Centrifugal Pump Based on a Population Balance Model

This work aimed to study the bubble distribution in a multiphase pump. A Euler-Euler inhomogeneous two-phase flow model coupled with a discrete particle population balance model (PBM) was used to simulate the whole flow channel of a three-stage gas-liquid two-phase centrifugal pump. Comparison of the computational fluid dynamic (CFD) simulation results with experimental data shows that the model can accurately predict the performance of the pump under various operating conditions. In addition, the liquid phase velocity distribution, gas-phase distribution, and pressure distribution of the second stage impeller at a 0.5 span of blade height under three typical working conditions were compared. Results show that the region with high local gas volume fraction (LGVF) mainly appears on the suction surface (SS) of the blade. With the increase in inlet gas volume fraction (IGVF), vortices and low velocity recirculation regions are generated at the impeller outlet and SS of the blade, the area with high LGVF increases, and gas–liquid separation occurs at the SS of the blade. The liquid phase flows out of the impeller at high velocity along the pressure surface of the blade, and the limited pressurization of fluid mainly happens at the impeller outlet. The average bubble size at the impeller outlet is the smallest while that at the impeller inlet is the largest. Under low IGVF conditions, bubbles tend to break into smaller ones, and the broken bubbles mainly concentrate at the blade pressure surface (PS) and the impeller outlet. Bubbles tend to coalesce into larger ones under high IGVF conditions. With the increase in IGVF, the bubble aggregation zone diffuses from the blade SS to the PS.

The vortex gas scaling regime of baroclinic turbulence

The mean state of the atmosphere and ocean is set through a balance between external forcing (radiation, winds, heat and freshwater fluxes) and the emergent turbulence, which transfers energy to dissipative structures. The forcing gives rise to jets in the atmosphere and currents in the ocean, which spontaneously develop turbulent eddies through the baroclinic instability. A critical step in the development of a theory of climate is to properly include the eddy-induced turbulent transport of properties like heat, moisture, and carbon. In the linear stages, baroclinic instability generates flow structures at the Rossby deformation radius, a length scale of order 1,000 km in the atmosphere and 100 km in the ocean, smaller than the planetary scale and the typical extent of ocean basins, respectively. There is, therefore, a separation of scales between the large-scale gradient of properties like temperature and the smaller eddies that advect it randomly, inducing effective diffusion. Numerical solutions show that such scale separation remains in the strongly nonlinear turbulent regime, provided there is sufficient drag at the bottom of the atmosphere and ocean. We compute the scaling laws governing the eddy-driven transport associated with baroclinic turbulence. First, we provide a theoretical underpinning for empirical scaling laws reported in previous studies, for different formulations of the bottom drag law. Second, these scaling laws are shown to provide an important first step toward an accurate local closure to predict the impact of baroclinic turbulence in setting the large-scale temperature profiles in the atmosphere and ocean.

Образование и снижение выбросов бенз(а)пирена и оксидов азота на котлах с вихревым движением газов

Образование и снижение выбросов бенз(а)пирена и оксидов азота на котлах с вихревым движением газов

On the issue of reducing the negative impact of nitrogen oxides in the system recirculation of diesel exhaust gases on applying the vortex effect

The problem of negative impact on the environment of motor transport is one of the most fundamental in the complex of global problems. The constant increase in the number of cars with internal combustion engines encourages the search for methods and ways to reduce the volume of negative impulses. The operation of heat engines is accompanied by significant emissions of gaseous harmful substances into the atmosphere, i.e. nitrogen oxides, carbon monoxide, hydrocarbons, as well as solid particles, including soot. The solution to this problem should be implemented within the framework of a systematic approach. To do this, it is necessary to combine the study of technical, economic, and organizational approaches to the organization of the exhaust gas disposal process. To date, there is a significant methodological base in the field of organizational and economic decisions. The article discusses various methods of cleaning exhaust gases of piston engines, their advantages and disadvantages are noted. The method of processing using ammonia is widely known. It is noted that a catalytic method for reducing nitrogen oxides using ammonia is quite economical. However, the optimal temperature range at which nitrogen oxides are reduced is rather narrow. To solve this problem, it is proposed to use the vortex effect in the exhaust system. The efficiency of using a vortex gas recirculation pipe is due to its significant influence on the thermal gasdynamic processes occurring in the exhaust system. Using the principles of non-equilibrium thermodynamics allows us to take into account dissipative processes when establishing the relationship of fuel and economic indicators of internal combustion engines with thermodynamic parameters. This significantly increases the accuracy of calculations and allows you to develop measures to reduce the level of negative impact on the environment.

Multichannel Capacitive Imaging of Gas Vortex in Swirling Two-Phase Flows Using Parametric Reconstruction

Swirl-based inline phase separation is a promising approach in the process industry with potential application in oil and gas separation in petroleum industry. To increase the efficiency of the separation, the process may be controlled. In this direction, the position and the diameter of the gas vortex are two parameters that can be used in the control loop, provided that they can be non-intrusively estimated. This article presents a capacitive sensor-based imaging method to extract these geometrical parameters. The proposed method consists in obtaining high-temporal resolution capacitance measurements at the pipe boundary of a test rig, which in turn are used in a reconstruction and extracting the targeted parameters of the gas vortex. The calculated parameters are then used to visually present the swirling flow. The measurement system was evaluated quantitatively by performing experiments with different phantoms of known diameters and positions in the sensing area. Dynamic measurements were also performed in a test rig for liquid-gas swirling flow. The capacitive imaging system is capable of detecting characteristics of the flow for a wide range of gas and liquid flow rates. A qualitative analysis was also carried out by comparing time series of the capacitive images with high-speed camera recording. The geometrical parameters obtained by the proposed approach presents a good agreement with the real data, with a root mean square deviation of 0.76mm for diameter and 0.88mm for vortex position. It can be utilized in future work as an alternative or complementary input for the controlled inline liquid-gas separation system.

Numerical Study on Separation Performance of Cyclone Flue Used in Grate Waste Incinerator

The traditional treatment of waste incineration flue gas is mostly carried out in low temperatures, but there are some problems such as corrosion of the heating surface at high and low temperatures, re-synthesis of dioxins, and low efficiency. Therefore, it is necessary to remove the pollutants at high temperatures. For the grate waste incinerator, this study proposes an adiabatic cyclone flue arranged at the exit of the first-stage furnace of the grate waste incinerator to pre-remove the fly ash at high temperatures, so as to alleviate the abrasion and corrosion of the tail heating surface. In this paper, computational fluid dynamics (CFD) method is applied to study the performance of a cyclone flue under different structural parameters, and the comprehensive performance of the cyclone flue is evaluated by the technique for order preference by similarity to an ideal solution (TOPSIS) method. The results show that particle separation efficiency increases at first and then decreases with the increase of the vortex finder length, the vortex finder diameter, and the distance between vortex finder and gas outlet tube, while it decreases with the increase of the gas outlet tube diameter. The pressure drop increases with the increase of the vortex finder length, and the vortex finder diameter, while decreases with the increase of the distance between the vortex finder, the gas outlet tube, and the gas outlet tube diameter. In the scope of this study, when h1/a = 1.1, D1/A = 0.33, h2/A = 1.5, and D2/A = 0.50, the comprehensive performance of the cyclone flue is much better.

Morphological signatures induced by dust back reaction in discs with an embedded planet

ABSTRACT Recent observations have revealed a gallery of substructures in the dust component of nearby protoplanetary discs, including rings, gaps, spiral arms, and lopsided concentrations. One interpretation of these substructures is the existence of embedded planets. Not until recently, however, most of the modelling effort to interpret these observations ignored the dust back reaction to the gas. In this work, we conduct local-shearing-sheet simulations for an isothermal, inviscid, non-self-gravitating, razor-thin dusty disc with a planet on a fixed circular orbit. We systematically examine the parameter space spanned by planet mass (0.1Mth ≤ Mp ≤ 1Mth, where Mth is the thermal mass), dimensionless stopping time (10−3 ≤ τs ≤ 1), and solid abundance (0 < Z ≤ 1). We find that when the dust particles are tightly coupled to the gas (τs < 0.1), the spiral arms are less open and the gap driven by the planet becomes deeper with increasing Z, consistent with a reduced speed of sound in the approximation of a single dust–gas mixture. By contrast, when the dust particles are marginally coupled (0.1 ≲ τs ≲ 1), the spiral structure is insensitive to Z and the gap structure in the gas can become significantly skewed and unidentifiable. When the latter occurs, the pressure maximum radially outside of the planet is weakened or even extinguished, and hence dust filtration by a low-mass (Mp < Mth) planet could be reduced or eliminated. Finally, we find that the gap edges where the dust particles are accumulated as well as the lopsided large-scale vortices driven by a massive planet, if any, are unstable, and they are broken into numerous small-scale dust–gas vortices.

Influence of the inlet gas velocity components on the survival of the vertex of gas in the plasma torch

The vortex gas injection into plasma torch is considered as a method for reducing electrodes erosion. In order to investigate the effects of vortex gas injection on plasma structure, as well as the effect of gas viscosity on the rate of rotation, a three-dimensional nonequilibrium and time-dependent non-transferred DC plasma torch model has been simulated. Viewing the general characteristics of the plasma shows that the model works well. The results have shown that if the components of the inlet gas velocity are not properly selected, it is possible that the rotary effects of the gas are greatly depleted even before the gas reaches the cathode tip and plasma formation. In this case, only the change in the axial component of the gas causes changes in the structure of the plasma. Vortex reduction is also observed during the movement of cold gases. It is observed that the change in viscosity of gas has significant effects on the rate of the vortex.

VORTEX GAS SEPARATORS DESIGN OPTIMIZATION

Currently, one of the ways to intensify oil production is to increase the depression to the reservoir by reducing the bottomhole pressure, usually to values below the saturation pressure. Therefore, a gas-liquid mixture is formed in the well, and gas separators are included in the composition of the electric centrifugal pump installations. However, with an increase in flow rate, firstly, the time spent by the gas-liquid mixture in the field of centrifugal separator forces decreases and the separation efficiency decreases. Secondly, the removal of rock particles increases, especially in wells after hydraulic fracturing, which, under the action of centrifugal forces, accumulate at the walls of the gas separator housing, which leads to their hydroabrasive destruction. A possible solution of this problem is the use of vortex gas separators, which use a shortened separation unit (screw), after which, downstream, there is a vortex chamber, where the liquid continues to rotate by inertia. Initially, vortex separators were designed to reduce the hydroabrasive effect of rock particles on the hull through the use of shorter screws. The purpose of this work is to solve the problem of optimizing the design of vortex gas separators. We have proposed a dimensionless criterion that determines the value of the separation ratio of gas separators depending on the geometrical dimensions of the vortex chamber, the operating conditions: gas concentration and shaft rotation frequency. Bench tests of three new designs of vortex gas separators in 5, 5A and 6 dimensions were carried out, showing that the dependence has a relatively narrow maximum which allows choosing the optimal dimensions of the vortex chamber for the given operating conditions.

The influence of pressure-sampling position on calibration K-factor of gas vortex flowmeter

According to the gas equation of state, the volume of gas at a certain time is related to the current temperature and pressure. Therefore, the calibrated K-factor of gas flowmeter will be affected by the temperature and pressure during the calibration process. Normally, in the ordinary pressure calibration process, the temperature change of calibration medium does not exceed 0.2 degrees, and the influence on the measurement results is about 0.08%. However, the influence on the measurement results can reach 3%∼4% due to the different position of the pressure-sampling. An array experiments were carried out on the gas vortex flowmeter (which was most influenced by the pressure-sampling position). It was found that different pressure-sampling positions affect the calibrated K-factor of the gas vortex flowmeters without temperature and pressure compensation, and the degree of influence is proportional to the pressure drop generated by the gas passing through the flowmeter. And the influence is nonlinear. The greater the gas flow velocity is, the more obvious the pressure difference among different pressure-sampling positions of the pipeline is and the more serious the deviation of calibrated K-factor from normal value is. So, when the calibrated K-factor deviate greatly at large flow velocity points but linear at other flow velocity points, the correctness of the pressure-sampling position in the calibration process should be considered.

Entropy of Negative Temperature States for a Point Vortex Gas

We study the dynamics and statistical mechanical equilibria of a neutral two-dimensional point vortex gas with Coulomb-like interactions confined in a squared and a rectangular domain. Using a punctuated Hamiltonian model in which we model the process of vortex–antivortex annihilation in superfluids by removing vortex dipoles, we show that this leads to evaporative heating of the system. Consequently, the vortex gas enters the negative temperature regime and subsequently relaxes to a maximum entropy configuration. We demonstrate that the large scale flows that emerge in this regime can be explained by using an equilibrium statistical mechanical mean field theory of point vortices based on a Poisson–Boltzmann equation. In particular, we observe that the emergent large scale flows in our point vortex simulations in the squared domain give rise to a spontaneous acquisition of angular momentum whereas the flows in the rectangular domain prefers a state with zero angular momentum. In addition to the observed qualitative agreement between the dynamical simulations and the theory that we demonstrate for the two geometries, we also present an approach that allows us to accurately compute a coarse-grained vorticity field, and henceforth recover the entropy from our dynamical runs. This allows us to perform a quantitative comparison between the dynamical point vortex simulations and the statistical mechanical predictions of the mean field theory thereby allowing us to clearly assert the validity of the assumptions of the statistical approaches as applied to this system with long-range interactions.

Study of the effects of walls on vortex formation and liquid maldistribution with two-phase flow around a spherical particle via numerical simulation

With the ever-increasing dependency on the activity of industrial catalysis in fixed bed reactors (FBRs), recent microscale studies based on liquid film spreading behavior on particle surfaces using numerical methods have attracted much attention. However, most studies have investigated one particle separately, and the effects of vessel walls or other particles are not considered. In our preceding study, we found that liquid spreading behavior and flow patterns are strongly related to the gas vortex and its shape under the particle. Therefore, in this work, the formation and scale of the gas vortex, as well as its generation and breakdown during the flow process, are considered as the parameters in the simulation. Two geometries named the near-wall configuration and the normal configuration were assumed and fully investigated using ANSYS FLUENT v15.0 with different operating parameters. As a result, both the size and the formation of the gas vortex without wall effects are larger and steadier than those with wall effects, and correspondingly, the liquid film is well distributed on the surface regardless of the gas and liquid (G/L) velocity because of the equivalent velocity of the gas trace near the particle. In contrast, in the near-wall configuration, when the flat wall approaches the particle, two vortexes under the particle probably break down and further merge into one larger vortex and cause liquid maldistribution on the particle surface during the development of the flow process. The velocities of the gas traces are inequivalent, even causing a reversed flow and thus trapping the liquid phase inside the interstices, which can be alleviated by increasing the rate of G/L velocity and setting a larger interstice between the particle and the flat wall. The newly uncovered information will enhance the understanding of liquid spreading behavior on particle surfaces and thus be applicable to the performance of FBRs.

Modeling of a compact gas vortex lens for high-power lasers

With 3D steady-state fluid simulations, we show that a negative lens can be created from a rotating gas (vortex) in a compact structure. The gas flow is well described by a compressible Bernoulli principle assuming an adiabatic, ideal gas. The gas lens’ focal length can be varied by adjusting the mass flow rate. The dominant aberration is spherical. Transient simulations show a 60 μs time scale for switching of the focal length. The gas vortex lens allows operation of high-power lasers above the damage thresholds of conventional optics and, additionally, its self-healing design allows operation near gas breakdown thresholds without risk to the optical element.

Vortex shape and gas‐liquid hydrodynamics in unbaffled stirred tank

AbstractThe present study investigated the effect of impeller speed and vortex ingestion on vortex shape, gas holdup, and bubble size distribution in an unbaffled stirred tank using optical probe measurements. Further, the ability of the volume of the fluid model to predict vortex shape was examined. Without vortex ingestion, an increase in impeller speed resulted in a significant variation in vortex shape, whereas it had a negligible effect on vortex shape with ingestion. This suggests that when vortex ingestion occurred, most of the energy was consumed for the dispersion of gas rather than the deformation of the gas‐liquid interface. It was observed that a large number of gas bubbles were entrained into the vortex core around the impeller region, which led to a lower gas holdup at the top axial locations. An increase in the impeller speed also resulted in the formation of larger bubbles. The absence of baffles limits shear for bubble break up, resulting in larger bubbles above the impeller plane.

Computational Fluid Dynamics Investigation of the Flow of Trailing Edge Cooling Slots

Slot film cooling is a popular choice for trailing edge (TE) cooling in high pressure (HP) turbine blades because it can provide more uniform film coverage compared to discrete film cooling holes. The slot geometry consists of a cutback in the blade pressure side connected through rectangular openings to the internal coolant feed passage. The numerical simulation of this kind of film cooling flows is challenging due to the presence of flow interactions such as step flow separation, coolant-mainstream mixing, and heat transfer. The geometry under consideration is a cutback surface at the trailing edge of a constant cross-section aerofoil. The cutback surface is divided into three sections separated by narrow lands. The experiments are conducted in a high-speed cascade in Oxford Osney Thermo-Fluids Laboratory at Reynolds and Mach number distributions representative of engine conditions. The capability of computational fluid dynamics (CFD) methods to capture these flow phenomena is investigated in this paper. The isentropic Mach number and film effectiveness are compared between CFD and pressure sensitive paint (PSP) data. When compared with the steady k − ω shear stress transport (SST) method, scale adaptive simulation (SAS) can agree better with the measurement. Furthermore, the profiles of kinetic energy, production, and shear stress obtained by the steady and SAS methods are compared to identify the main source of inaccuracy in RANS simulations. The SAS method is better to capture the unsteady coolant–hot gas mixing and vortex shedding at the slot lip. The cross flow is found to affect the film significantly as it triggers flow separation near the lands and reduces the effectiveness. The film is nonsymmetric with respect to the half-span plane, and different flow features are present in each slot. The effect of mass flow ratio (MFR) on flow pattern and coolant distribution is also studied. The profiles of velocity, kinetic energy, and production of turbulent energy are compared among the slots in detail. The MFR not only affects the magnitude but also changes the sign of production.

Multiple Wire-Mesh Sensors Applied to the Characterization of Two-Phase Flow inside a Cyclonic Flow Distribution System.

Wire-mesh sensors are used to determine the phase fraction of gas–liquid two-phase flow in many industrial applications. In this paper, we report the use of the sensor to study the flow behavior inside an offshore oil and gas industry device for subsea phase separation. The study focused on the behavior of gas–liquid slug flow inside a flow distribution device with four outlets, which is part of the subsea phase separator system. The void fraction profile and the flow symmetry across the outlets were investigated using tomographic wire-mesh sensors and a camera. Results showed an ascendant liquid film in the cyclonic chamber with the gas phase at the center of the pipe generating a symmetrical flow. Dispersed bubbles coalesced into a gas vortex due to the centrifugal force inside the cyclonic chamber. The behavior favored the separation of smaller bubbles from the liquid bulk, which was an important parameter for gas-liquid separator sizing. The void fraction analysis of the outlets showed an even flow distribution with less than 10% difference, which was a satisfactorily result that may contribute to a reduction on the subsea gas–liquid separators size. From the outcomes of this study, detailed information regarding this type of flow distribution system was extracted. Thereby, wire-mesh sensors were successfully applied to investigate a new type of equipment for the offshore oil and gas industry.

Система для автоматического измерения объемного газосодержания и вихревой дегазации бурового раствора

Система для автоматического измерения объемного газосодержания и вихревой дегазации бурового раствора

Design and characterization of an electromagnetic‐resonant cavity microwave plasma reactor for atmospheric pressure carbon dioxide decomposition

Plasma processes are ideally suited for the conversion of renewable electricity into gas‐phase reactivity, such as for the decomposition of carbon dioxide (CO2). The design, development, and characterization of a microwave plasma reactor for atmospheric pressure undiluted carbon dioxide decomposition are presented. The reactor operates as an electromagnetic‐resonant cavity in which the generated plasma forms a bulb attached to a converging‐diverging nozzle and stabilized by streams of tangentially injected processing gas. Electromagnetic wave confinement, residence time, and critical gas vorticity constitute fundamental reactor sizing and operation parameters. Experimental results show that flow rate plays a dual role in plasma stabilization and process performance, whereas deposited power has a minor role in CO2 decomposition.