Flow Field Of Continuous Phase Research Articles

A theoretical model for calculating particle trajectory in a vane-type separator

A vane-type separator has been successfully applied to gas-liquid and liquid-liquid separation. In order to evaluate the separation performance of the separator, a theoretical model for calculating the particle motion trajectory in the vane-type separator was developed. Firstly, the simplified steady incompressible Navier-Stokes equations were derived to acquire the equations of tangential velocity and axial velocity of continuous phase flow field. Then, the coefficients were determined by fitting the CFD results and it can be used to obtain the velocity at different swirler structure conditions. Further, the force analysis on the particle was conducted to develop the motion governing equations to predict the trajectory. The predicted separation lengths at different geometric swirl number conditions show a good agreement with the experimental results and its relative error is smaller than 3%. Besides, the effects of the key parameters including density difference, particle size and viscosity of the continuous phase on the separation length were investigated.

CFD-DEM simulation of particle revolution and high-speed self-rotation in cyclones with different structural and operating parameters

Systematically researching the association of the turbulentflow in cyclone with the particle revolution and high-speed self-rotation may provide new insights for improving the separation performance and expanding the application of cyclones. In this study, the effect of cyclone structural parameters and inlet gas velocity on the continuous phase flow field as well as the revolution and high-speed self-rotation of the dispersed phase particles. It was observed that the particle self-rotation speed increases with the increase of cylinder-to-cone ratio, the decrease of the cone angle, and the increase of the inlet gas velocity. With the cylinder-to-cone ratio, i=1, half-cone angle, α=4.7° and the inlet gas velocity of 20 m/s, the average particle self-rotation speed was determined to be 7124 rad/s. Meanwhile, it was also revealed that the cyclone structure and inlet gas velocity remarkably affected the velocity of the flow field, vorticity, pressure drop and residence time of revolution movement of particles within the cyclone. This study can provide theoretical fundamental for the industrial applications of cyclone in chemical engineering and environmental engineering related to the separation of pollutants on the surface of particles and in pores.

Simulation analysis of gas-solid separation system for hazardous materials’ collection truck

In view of the hazardous materials’ leakage caused by traffic accidents during their transportation, a concept and design of a hazardous materials’ collection truck is proposed for a safe collection and transportation to a professional processing factory. In order to prevent secondary pollution caused by hazardous materials in the vacuum collection process, the gas-solid separation operation must be performed in the hazardous materials collection truck. According to the needs of the gas-solid separation, the structural composition and working principle of the hazardous materials collection truck were analyzed, and the separator was modeled by the finite element analysis method. In the simulation process, the continuous phase flow field simulation of the air is performed first, and on this basis, the discrete phase analysis of the particles is added. The effects of gas flow inlet velocity and particle size on the separation efficiency of the separator were analyzed. Based on the response surface method, the structure of cyclone separator was improved to find the optimal solution and enhance the separation efficiency.

Single bubble breakup in the flow field induced by a horizontal jet—The experimental research

AbstractBubble breakup in multiphase reactors has a direct and important impact on the mass transfer and reaction process. This paper experimentally investigated the single bubble behaviors of deformation and breakup under the affecting of a jet submerged in a water‐filled tank. The dispersed phase motion was captured by a high speed camera, while the continuous phase flow field was analyzed by Particle Image Velocimetry. By changing the downstream location of bubble generation, the liquid flow rate and the initial bubble size, the breakup processes were analyzed and discussed. The breakup point, break pattern, and distribution of daughter bubbles were summarized. The position where the bubble gets the maximum acceleration was defined as the shear position, and the forces on the bubble at the shear position had a significant impact on whether breakup will occur. The expected bubble number, which could reflect a combination of the breakup probability and daughter bubbles distribution, was defined and found to be directly proportional to the capillary number of bubbles at the shear position. The research result will contribute to promoting the understanding and control of multiphase flow, and providing a theoretical basis and technical support for the design and optimization of multiphase reactors.

Parametric CFD studies on erosion in 3D double elbow

Elbow as an integral part of natural gas piping systems, is vulnerable in erosive environments. This paper presents a computational fluid dynamics (CFD)-based erosion prediction model and its application to 3D double elbow. The salient features of this methodology include Eulerian continuous phase flow field generation through steady simulation using RNG turbulence model, and evaluation of particle distribution behaviour through discrete phase modelling using particle injection technique. Effects of gas velocity, sand mass flow, particle diameter, pipe diameter, elbow radius, angle of bend and bend orientation on the erosion rate in the double elbow are examined. The simulation results show that slow gas velocity, slow particle mass flow rate, small particle diameter, large pipe diameter, and high elbow radius bring about long service life for the double elbow.

CFD simulation and PIV measurement of liquid–liquid two-phase flow in pump-mix mixer

A computational fluid dynamics (CFD) simulation based on Eulerian–Eulerian two-phase method and Reynolds average Navier–Stokes (RANS) approach accompanied by experimental velocity field measurements via particle image velocimetry (PIV) has been applied to study flow characteristics of liquid–liquid system in pump-mix mixer in the present work. Effects of impeller speed, flow ratio and drop size on continuous phase flow field and dispersed phase holdup were investigated. Results show that low location of impeller causes remarkable heterogeneity of velocity field and holdup. Lower impeller speed, smaller flow ratio and finer droplet increase the homogeneity of holdup distribution. Dual-impeller configuration was then investigated. Effects of spacing between upper and lower impeller on flow field, holdup and three dimensionless numbers were also evaluated. Compared to single impeller, the proposed dual-impeller, which dissipates 48% more power but discharges 193% more fluid, enhances the velocity of fluid in upper region of mixer and improves the homogeneity of holdup effectively.

Stochastic separated flow models with applications in numerical computations of supersonic particle-laden turbulent flows

In this article, three stochastic separated flow models were applied to predict the dispersion of inertial fuel particles in the supersonic turbulent flows. The flow field of continuous phase was simulated by means of Reynolds-averaged Navier–Stokes method with a two-equation turbulence model. Clift’s expression was used to modify the drag force on the particle considering the compressibility effects. The particle-phase statistics were obtained by a secondary-order time-weighed Eulerian method. The ability of those stochastic separated flow models was then compared for predicting the mean particle velocity and the particle dispersion. For obtaining a statistically stationary solution, the stochastic separated flow model required the largest number of computational particles, whereas the improved stochastic separated flow model was found to need the least. The time-series stochastic separation flow model lay in-between. Compared with the other two models, the particle dispersion was over-predicted by the stochastic separated flow model in the supersonic particle-laden boundary layer flow, while the improved stochastic separated flow model was less predictable for the particle spatial distribution in the particle-laden strut-injection flow. Three models could well predict the mean velocities of the particle phase. This study is valuable for selecting a validated model used for predicting the particle dispersion in supersonic turbulent flows.

Flow field of continuous phase in a vane-type pipe oil–water separator

In this work, the measurements of the swirling field of continuous phase in a new vane-type pipe separator have been carried out to validate the separation characteristics by the Particle Image Velocimetry. The radial, tangential and axial velocities were obtained. The results show that the new separator can successfully form a symmetrical swirling field. The transition region of the tangential velocity between the free vortex and the forced vortex shows a wider range than that in the traditional hydrocyclone. The axial velocity is always positive from the pipe wall to the central area and appears three-peak distribution. The tangential and axial velocities are dependent to the inlet flow rate, and yet show a low sensitivity to the ratio of flow split when the ratio of flow split is less than 13.1%. These results are helpful to the optimal design of the downhole oil/water separator.

Numerical Simulation of Particle-Laden Coaxial Turbulent Jets

In this study, the near flow field characteristics of particle-laden coaxial jets are numerically investigated at three outer to inner mean velocity ratios of 1.11, 0.48, and 0.18. Three-dimensional, steady, incompressible, turbulent flow RANS simulations are carried out to this effect. The single-phase predictions are compared with the available experimental data to validate the numerical approach. Later, two phase simulations are carried out by adding discrete particles, glass beads of 240 microns, to the continuous phase. The flow field details and the turbulent characteristics of the particle-laden coaxial jets are investigated at two mass loading ratios of 0.074% and 0.22%. The predictions of the mean axial velocity and axial turbulent intensity, correlation coefficient, vorticity, and dissipation of turbulent kinetic energy are compared between the single-phase and two-phase flows to highlight the influence of discrete particles on the fluid phase. This work also shows a good agreement between the RANS calculations and experimental data, when a proper turbulence model is adopted. The results demonstrate the importance of velocity ratio on the flow field development and turbulent characteristics of coaxial jets. The results show that the influence of discrete particles on the continuous phase flow field is marginal at the mass loadings studied in this work.

Drag on a single fluid sphere translating in power-law liquids at moderate Reynolds numbers

A numerical investigation has been carried out to obtain the steady state drag coefficients and flow patterns of a single Newtonian fluid sphere sedimenting in power-law liquids. A finite difference method based simplified marker and cell (SMAC) algorithm has been implemented on a staggered grid arrangement to solve the continuity and momentum equations. For both phases, the convective terms have been discretized using the quadratic upstream interpolation for convective kinematics (QUICK) scheme, and diffusive and non-Newtonian terms with central differencing scheme. An exponential transformation has been applied in the radial direction for the continuous phase computational domain. In order to ensure the accuracy of the solver, extensive validation has been carried out by comparing the present results with the existing literature values for a few limiting cases. Further, in this study the effects of the Reynolds number ( Re o ) , internal to external fluid characteristic viscosity ratio ( k ) and power-law index ( n o ) on the continuous phase flow field, pressure drag ( C dp ) , friction drag ( C df ) and total drag ( C D ) coefficients have been analyzed over the range of parameters: 5 ⩽ Re o ⩽ 500 , 0.1 ⩽ k ⩽ 50 and 0.6 ⩽ n o ⩽ 1.6 . Based on numerical results obtained in this work, a simple correlation has been proposed for the total drag coefficient, which can be used to predict the rate of sedimentation of a fluid sphere in power-law liquids.