Gas-liquid Mixture Research Articles

Numerical modeling of drying from saturated to unsaturated conditions with two-phase partitioning boundaries at the medium surface and interface-dependent phase change

To accurately predict the drying of a porous medium from saturated to unsaturated conditions over time, this paper proposes two-phase partitioning boundaries for liquid water evaporation and water vapor transport at the medium surface. A non-isothermal two-phase (liquid water and gas mixtures), two-component (dry air and water vapor) transport model with nonequilibrium and interface-dependent phase change is then developed. The governing equations are then numerical solved using COMSOL Multiphysics software and applied to describe a series of laboratory soil drying tests as examples. The performance of the proposed boundaries at the surface is illustrated by comparison with other three common used boundaries. The results show that a specific flux of vapor at the surface with a zero flux of liquid water cannot be adopted to describe the drying process of initially saturated media due to the lack of interconnected gas-filled pores. The merged liquid-vapor boundary applied in the Darcy–Richards model significantly prolongs the constant rate stage when the liquid water evaporation is dominant. Then, the effects of air/gas–water interfacial area and water retention parameters on the drying process are investigated. A faster reduction in the air–water relative interfacial area at the medium surface will shorten the drying process with earlier dominance of the vapor transport. An increased entry capillary pressure and a decreased pore size distribution index for the water retention curve will result in slower drying, more loss by vapor transport and a more homogeneous distribution of pore water respect to depth. The current study can promote the understanding of the evolution of drying mechanisms of a porous medium from saturated to unsaturated conditions.

From Nanovesicles to Nanobubbles Based on Repeated Compression Method.

Nanobubbles have been increasingly applied in biomedicine, which is attributed to their ability to work as ultrasound imaging contrast agents and powerful gene/drug carriers. Different production techniques or approaches have been developed to generate uniform and stable shelled nanobubbles. However, these shelled nanobubbles are usually prepared based on disordered shell materials, such as free phospholipids and polymers. In recent years, the continuous repeated compression method for a gas-liquid mixture has been developed to produce free and lipid-shelled nanobubbles. In this study, to explore the response of well-organized nanostructures to this method, the repeated compression method was used to treat preprepared liposomes and polymeric nanovesicles. Size distribution, morphologies, and ultrasound image contrast enhancement of these nanovesicles were determined before and after repeated compression. Results demonstrate that the presence of a phospholipid bilayer is vital to form liposome-based nanobubbles. And the low elastic modulus of the polymeric membrane is key to encapsulate gases into polymeric nanovesicles. Overall, it demonstrated the advantages of well-organized nanostructures to produce nanobubble structures, giving new insights into the preparation and understanding of nanobubbles.

Микропузырьковая безреагентная гидрофобизация поверхности угля

The paper describes methodological features of coal surface hydrophobization the using a microbubble gas-liquid medium to intensify the process of flotation concentration of coal. Air microbubbles were generated using decompression of liquid saturated under air pressure. The influence of water saturation pressure with gas on the size of the bubbles and their stability over time has been established. It is shown that addition of microbubbles leads to formation of an intermediate hydrophobic air layer on the surface of coal, which is the basis for catching bubbles of the flotation size. The results of coking coals flotation using a microbubble gas-liquid mixture are presented. By means of the method of differential particle size analysis, the preferred flotation of fine coal particles < 50 microns in size by micro-bubbles of air was established. It was found that for low-ash coals, the efficiency of reagentless microbubble flotation can be comparable with the results of concentration using traditional petrochemical reagents. In the reagent mode, the micro-bubbles are attached to the oil-hydrophobized surface of small particles with the formation of carbon-air complexes.

Thermoelectromagnetic SmallSat propellant positioning

Low gravity fluid management is key to a variety of spaceflight applications, from life support aboard the International Space Station to propellant management in satellite tanks. Capillary devices are traditionally employed to position fluids in a microgravity environment, but they fail to induce effective phase separation in the conformal tank geometries and saturated two-phase propellants adopted in modern CubeSat propulsion. In order to meet the stringent requirements of future small satellite missions, this paper explores the application of capillary, magnetic positive positioning, thermal, and dielectrophoretic fluid management devices to conformal propellant tanks. The electromagnetic and capillary devices rely upon body and surface forces, respectively, while the proposed thermal approach exploits phase change in saturated liquid–gas mixtures to position the fluid. Each concept is evaluated based on its ability to reorient the propellant and maintain its position during operation, as well as the resulting volume, mass, and power requirements. Ultimately, thermomagnetic and thermodielectrophoretic devices are deemed to be best suited for the case under analysis because of their low size, weight, and power demand in combination with their reliability and performance. These new systems offer a novel and robust solution to small satellite propellant management, a key enabling technology for the future of maneuverable CubeSats.

Experimental Study on Friction Coefficient of Gas–Oil Two-Phase Flow in a Large Annulus

Summary The friction coefficient is an important factor that affects the accurate calculation of wellbore annular pressure distribution and is of great significance for the safety of drilling operations. To date, investigations of the friction coefficient mainly focused on low-viscosity liquids (such as water and kerosene). Thus, the obtained friction coefficients have poor applicability in the calculation of gas–oil-based mud two-phase flow. This study reports gas–oil two-phase flow experiments for different viscosities (16–39 mPa·s) in the annulus of a large wellbore, performed using an experimental wellbore (Φ100×Φ60×12 000 mm). The gas–liquid mixture Reynolds number ranges from 500 to 10,000. The results reveal a consistent trend for the variation of the friction coefficient under different flow patterns. For the same mixture Reynolds number, a larger liquid viscosity corresponds to a smaller variation of the friction coefficient among different flow patterns. The larger the superficial liquid velocity, the greater the friction coefficient. Based on the dimensionless analysis of the experimental data, a model for the calculation of the friction coefficient of gas–oil two-phase flow in a large annulus is established, and its prediction error relative to the experimental data is found to be less than 30%. This study can provide a basis for accurate calculations of gas–oil-based mud two-phase flow in drilling wellbores.

Risk reduction of tank explosion based on passivation of unusable propellant residues

To reduce the risk of explosion of propellant tanks of expended spacecraft and launch vehicles with liquid rocket engines in orbit, as well as in case of emergency situation, for example, loss of orientation, the Inter-Agency Space Debris Coordination Committee recommends passivation measures, including the discharge of residual liquid propellant and pressurant gas. In ANSYS-Fluent program complex possible initial positions of liquid propellant residues in a spherical tank at its rotation under conditions of low gravitational fields are determined. The values of liquid propellant residues depending on their initial position in the spherical tank at opening of the drain line for discharge of gas–liquid mixture into the ambient space are determined. The concept of formation of two-phase flows of liquid propellant on the example of the spherical tank at tangential entry of compressed gas is offered. The relationship between the number of gas inlet points and the effectiveness of the developed method (expressed as the ratio of the mass of expelled liquid propellant to the mass of gas expended) is demonstrated. For instance, the use of 2 gas inlet points achieves an efficiency of up to 30 %, while employing 3 gas inlet points increases it to 89 %.

Effect of Blade Twist on The Flow Characteristics of Gas-Liquid Two-Phase Flow in a Spiral Axial Flow Pump

The mixing of oil and gas forms the foundation of deep-sea oil and gas extraction and transportation. However, traditional conveying equipment has low efficiency and high failure rates. In this study, a spiral axial flow gas and liquid multiphase pump was used as the base model. The Eulerian multiphase flow model and RNG turbulence model were used for numerical simulations to analyze the internal flow field of the multiphase pump. A modification scheme was proposed to twist the airfoil shape and create a twisted vane. The twisted blade with the center of the hub-side flange chord length as the twisting center was twisted in the counterclockwise direction to help reduce the relative volume of gas in the flow channel. When the twisted vane with the hub-side airfoil type trailing edge point as the twisting center was twisted in the suction side direction, it helped to accelerate the movement of the gas-liquid mixture at the trailing edge of the back of the vane and further reduced the low velocity zone at the back of the vane. When the twist center is located at the hub side wing type trailing edge point of the twist vane, the twist degree is 0.214. This results in the maximum head and efficiency of the pump, improves gas phase aggregation phenomenon, and enhances the performance of the multiphase pump.

Совершенствование проточной части мультифазных ступеней с использованием мультифазного коэффициента относительной скорости движения дискретных частиц

Equations are derived to design and develop the multiphase stages flow path in a diagonal form using the dimensionless multiphase coefficient of the discrete particles relative speed. An analysis was made of the formation fluid flow containing free gas bubbles in the serial multiphase stages flow path of axial and axis-diagonal types in comparison with the developed diagonal-type stages and with inclined-cylindrical and helical blades. It is shown that, compared to the axial and axis-diagonal type stages, multiphase stages of the diagonal type with the inclined-cylindrical and helical blades have higher pressure when operating on the gas-liquid mixtures, especially in the multi-stage design. When operating on water without free gas, pressure and efficiency of the multiphase stages exceed characteristics of the best analogues, which makes it possible to manufacture the full-size pumps operating efficiently on liquid without gas and on the gas-liquid mixture.

ABOUT THE FILLING FACTOR OF PROGRESSIVE CAVITY PUMPS

Progressive Cavity Pumps (PCP) are becoming more and more common in various industries. In the oil and gas sector, PCP are widely used in downhole pumping units for oil production, as well as multiphase pumps for transporting gas-liquid mixtures. In recent decades, PCP have been widely used in the drilling mud circulation systems in fine cleaning units using centrifuges, as well as in various environmental projects. At the same time, industrial experience shows that in order to increase the efficiency of the PCP in various technological processes in the oil, construction, food and other industries, it is necessary to clarify some provisions of the theory and practice of using single-screw hydraulic machines in nonstandard operating conditions. One of these issues, which has not yet been fully reflected in scientific and reference publications, is the study of the process of filling screw working cavities in the case of pumping high-viscosity fluids.
 The article discusses the theoretical foundations of modeling the process of filling the PCP and proposes dependencies for determining the filling factor, which allows for a reasonable approach to the choice of geometric and operational parameters of the pump in a wide range of changes in the properties of pumped products.

Hydraulic losses in cryogenic pipelines

Pressure losses in cryogenic pipelines for cases of monophasity of the flow are defined by known formulas of hydraulics for ordinary viscous liquids. The movement of the two-phase flow is much complicated by the hydraulic calculation of the cryogenic pipeline. There are basically three types of cryogenic flow movement in the pipelines. The first type is characterized by a sufficiently uniform distribution of the gas phase over the entire volume of the flow (homogeneous gas-liquid mixture). The second type is characterized by sections of gas and liquid (projectile structure). The third type is characterized by the movement of liquid along the annular section at the walls of the pipe and gas with a higher speed in its central part. In the absence of heat exchange with the environment, when pressure losses are associated with gravity and friction, the calculation formulas are offered in the paper for hydraulic calculation of multiphase cryogenic pipelines.

Использование мультифазных коэффициентов для анализа и совершенствования конструкций лопастных машин, работающих на газожидкостных, парожидкостных смесях, смесях из жидкости и твердых частиц

To increase the oil recovery factor, the bottom-hole pressure is reduced, which is accompanied by an increase in the free gas and mechanical impurities content at the pump inlet. As a rule, the serial equipment is not providing reliable and efficient operation in such conditions. In oil producing wells with the high free gas content, efficiency of the multiphase modules blade stages could be increased by correct selection of the serial equipment and introduction of the new design solutions. The paper analyzes specifics of the gas-liquid mixture flow in the flow path of the blade multiphase stages pumping the gas-liquid mixtures. Recommendations are provided for improving the flow path taking into account the multiphase specific speed coefficient formula. It is proposed to use the multiphase coefficient along with the cavitation specific speed coefficient in development of the blade pumps operating under the steam cavitation conditions.

Gas-hydrodynamics of gas-liquid flow in the reservoir-well system

A hydrodynamic model of gas-liquid flow in the reservoir-well system is developed and the boundary problem is solved.As the volume of liquid in the mixture is very small (5-10%), its effect on the gas-liquid mixture flow was considered only in terms of density change effect. It is assumed that liquid and gas particles move in the pipe at the same speed and there is no mass transfer.The gas is assumed to be ideal and an isothermal process is considered. The solution of some equations in initial and boundary conditions is found and the continuity condition at the well bottom is written, Pc(t) - bottom hole pressure is found. The borehole productivity is then determined by setting Pq.a (t) (taken from experiment).

Quasi-Gasdynamic Model and Numerical Algorithm for Describing Mixtures of Different Fluids

An elegant and easy-to-implement numerical algorithm for simulating flows of homogeneous gas mixtures with component temperatures and velocities assumed to be equal is constructed and tested. The algorithm yields monotone density profiles for the components even if their specific heat ratios are widely different. The algorithm can be used to simulate some flows of gas–liquid mixtures.

Motion of a Gas–Liquid Mixture in the Bed–Pipeline System Subject to Heat Transfer

Motion of a Gas–Liquid Mixture in the Bed–Pipeline System Subject to Heat Transfer

Numerical simulation of supersonic gas flow in a conical nozzlewith local plasma heating and experimental results

The results of the main theoretical calculations and some experiments on local heating of the supersonic flow of gases by an external inductor with low-temperature plasma during the ionization of gases in a ceramic, conical nozzle, carried out by means of a powerful, high-frequency, electromagnetic field, are given. Numerical calculations are based on the provisions of electromagnetic field theory based on the equations of Maxwell, Navier Stokes for gas dynamics, Saha Eggert for ions and electrons, which make it possible to calculate the basic parameters of the inductor and the necessary specific power for heating supersonic, multicomponent, gas flows with low-temperature plasma. A model of vortexless (laminar), supersonic, stationary gas flow was used and mathematical modeling of its movement in a conical nozzle was carried out with the aim of possibly using the effect of additional heating of the gas flow with low-temperature plasma to increase the efficiency of the liquid rocket engine. It was found that in order to effectively heat the gas flow with low-temperature plasma in the design diameter, a conductivity of gases of at least s 200 1/·m is required for the initial temperature Ta = 2528 2674 оK and the frequency f = 27,12 MHz, which is not feasible even in the presence of a high concentration of impurities based on alkali metals. Therefore, a special device was developed an ionizer for the combustion chamber. The use of an ionizer allows to achieve the specified conductivity for the pressure in the combustion chamber of 15 MPa (a link to the article is given in the list of references). Calculations indicate the possibility of effective heating with low-temperature plasma of the supersonic flow of gases in the initial volume of the conical nozzle, which is adjacent to the critical cross-section of the liquid rocket engine. This will allow in the future to significantly increase its specific impulse and thrust at the start, due to an increase in the flow rate of gases in the design section. It has also been determined that the parietal region of a conical nozzle has a significant temperature gradient in the radial direction, whereas along the symmetry axis of the conical nozzle, the temperature increase has a linear relationship. The results of numerical simulations are qualitatively consistent with the experiments conducted in a quartz reactor cooled by water, which made it possible to use a variety of gas and gas-liquid mixtures to select fuel with the optimal composition of components. Preliminary data obtained on a working stand with a thermal power of a quartz reactor not exceeding 4 kW are given.

Validation of the CFD Tools against In-House Experiments for Predicting Condensing Steam Flows in Nozzles

The issues addressed in this work concern the condensing steam flows as a flow of a two-phase medium, i.e., consisting of a gaseous phase and a dispersed phase in the form of liquid droplets. The two-phase character and the necessity to treat steam as a real gas make the numerical modeling of the flow in the last steam turbine channels very difficult. There are many approaches known to solve this problem numerically, mainly based on the RANS method with the Eulerian approach. In this paper, the two Eulerian approaches were compared. In in-house CFD code, the flow governing equations were defined for a gas–liquid mixture, whereas in ANSYS CFX code, individual equations were defined for the gas and liquid phase (except momentum equations). In both codes, it was assumed that there was no velocity slip between phases. The main aim of this study was to show how the different numerical schemes and different governing equations can affect the modeling of wet steam flows and how difficult and sensitive this type of computation is. The numerical results of condensing steam flows were compared against in-house experimental data for nozzles determined at the Department of Power Engineering and Turbomachinery of the Silesian University of Technology. The presented experimental data can be used as a benchmark test for researchers to model wet steam flows. The geometries of two half nozzles and an International Wet Steam Experimental Project (IWSEP) nozzle were used for the comparisons. The static pressure measurements on the walls of the nozzles, the Schlieren technique, and the droplet size measurement were used to qualitatively identify the location of the condensation onset and its intensity. The CFD results obtained by means of both codes showed their good capabilities in terms of proper prediction of the condensation process; however, there were some visible differences in both codes in the flow field parameters. In ANSYS CFX, the condensation wave location in the half nozzles occurred much earlier compared to the experiments. However, the in-house code showed good agreement with the experiments in this region. In addition, the results of the in-house code for the mean droplet diameter in the IWSEP nozzle were closer to the experimental data.

Multiobjective and multicondition optimization for a gas–liquid mixed-flow pump based on a three-dimensional inverse design

The mixed-flow pump performs well in transporting gas–liquid mixtures with large flow rates and high inlet gas volume fractions. However, its extensive development is still limited by the operating range and poor overall performance. In this study, a multiobjective and multicondition optimization methodology for improving the gas–liquid flow performance of a mixed-flow pump based on the inverse design is proposed. The impeller blade load is taken as the optimization variable. Moreover, the Euclidean distances of the pressure increment, efficiency, and gas volume fraction in the diffuser are adopted as optimization objectives. Results show that the numerical methodology is verified by the pressure increment and gas distribution obtained in the tests of the original pump. Optimized results demonstrate that the slope of the straight line, the stacking angle at the hub, and the intersection point of the rear parabola and the straight line significantly affect the objectives. The increased load of the first half of the impeller and the reduced load of the second half may improve the comprehensive performance of mixed-flow pumps. The blade length and wrap angle are reduced after optimization, which changes the inlet and outlet angles and deflection of the blade, thereby helping to enhance the cognition of mixed-flow pump performance optimization.

Detonation of a Gas–Liquid Mixture on an Oblique Boundary in the Case of Wave

Detonation of a Gas–Liquid Mixture on an Oblique Boundary in the Case of Wave

UNIVERSAL HYDROGAS-DYNAMIC PATTERNS OF THE DRAINAGE ZONE OF OIL AND GAS WELLS

Large-scale experimental hydrogasodynamic studies of the flow of a two-phase gas-liquid mixture in a vertical pipeline were carried out. Based on the analysis of the results of these experimental studies, it was found that among the results obtained there are dependencies with theoretical bases by which theoretical hydrogasodynamic methods for studying multiphase flow in a vertical pipeline can be developed. The article provides a theoretical hydrogasodynamic study using dependencies describing a two-phase flow in a vertical pipeline of a round section, and it is confirmed by existing experiments. As a result of the gas-hydrodynamic study of pumping wells, in order to confirm the rational use of formation gas energy, a positive effect due to an increase in oil production rate and well process parameters, a relationship was established between well Q production rate, bottom-hole pressure of well P and production of formation gas V. Parameters can be modeled using three-term polynomials. During operation of wells in three modes (Qi, Vi or ∆Pi,Vi, where i = 1,2,3), processing of data obtained as a result of studies, indicators determined by existing research methods were obtained, and the technological mode ensuring layer-bylayer cooperation of the well system was selected.
 It is known that the motion of a two-phase flow of gas-liquid mixtures in a vertical pipe string is described on the basis of energy balance theory. The hydrogasodynamic characteristics of the drainage zone can be obtained in a real oil and gas well, as an experimental installation in the form of

TECHNOLOGIES FOR THE DEPOSITS VOLUME ASSESSING USING REFERENCE LIQUIDS IN PIPELINES

The gas-liquid mixture flow along an oil and gas field pipeline is a complex process, the parameters of which, as a rule, are not determined along its length. Pressure and temperature of water-oil emulsion decrease along the pipeline length, pressure and temperature conditions of separation from oil both light components in the form of associated petroleum gas and heavy components – in the form of asphaltenes, resins, paraffins and mechanical impurities – change. Two techniques for deposit quantitative diagnostics in the pipeline are discussed in the article. Viscosity and velocity of injected reference fluid in the pipeline section complicated by deposits are considered as informative parameters when using pressure sensors and ultrasonic flowmeter.
 Technologies for the quantitative assessment of deposits in oilfield pipelines based on the control of the movement of a fluid with a reference property different from the property of the pipeline fluid are proposed. According to the first technology, the viscosity of the liquid is changed and the pressure difference at the beginning and at the end of the pipeline with deposits is fixed in time. According to the second technology, the value of the increased velocity of fluid movement in places where the pipeline is narrowed due to the presence of deposits is measured. The theoretical basis of the processes occurring with liquids in pipeline transport is substantiated. With an increase in the viscosity of the reference liquid, the degree of compression of the liquid increases and, as a result, the frequency of vibrations of the liquid molecules increases. With a decrease in the viscosity of the reference liquid, the reverse picture is observed.