Vortex Finder Research Articles

Effects of feed size distribution on separation performance of hydrocyclones with different vortex finder diameters

Interactions between feed size distribution and separation performance for hydrocyclones with different vortex finder diameters (Do) are crucial for hydrocyclone designs but not clearly understood. In this work, the optimum range of Do is numerically confirmed for a 50mm diameter hydrocyclone using computational fluid dynamics. Furthermore, effects of feed size distribution (FSD) on separation performance for hydrocyclones with different Do are discussed. For a given FSD, the lower limit of Do can be determined from the flow stability characterized by lower turbulence intensity and larger tangential velocity. Below the lower limit, a large proportion of fine particles report to the underflow. The upper limit can be determined from separation performance. Above the upper limit recovery to the underflow for coarse particles decreases drastically, which is caused by an outward shift of the locus of zero vertical velocity (LZVV) and an inward shift of particles equilibrium radius. For a given Do, FSD has no significant effects on partition curves when Do is in the optimum range. When Do is above the optimum range, both recovery to underflow for coarse particles and separation sharpness are decreased as the feed median size increases. In summary, when Do is in the optimum range, the hydrocyclone can adapt to different FSD to obtain the expected cut size by self-adjusting the LZVV and particles equilibrium radius. This method for determining the optimum range of Do is based on flow pattern characteristics and can be used as a universal tool for hydrocyclone design.

Classification performance analysis of a novel cyclone with a slit on the conical part by CFD simulation

Abstract This paper proposes a novel slit-cone cyclone design and presents the subsequent evaluation of the effects of different slit locations on gas flow fields and particle separation efficiencies using experimentation and computational fluid dynamics (CFD) simulation. The slit increased the radial motion of the gas flow and improved the ability of the jacket to capture finer submicron particles with a size less than 1 μm. Because some gas escaped from the cyclone through the slit, the shearing between the core upward and annulus downward streams decreased, and the gas bypassing to the vortex finder also decreased. Because of these two mechanisms, cyclone designs that included a cone slit demonstrated enhanced partial separation efficiencies, primarily attributable to submicron particle capture. The overall separation efficiency increased from 74.5% for a conventional cyclone to 80.7% for a cyclone with a lower cone slit. In addition, the cut size decreased from 1.35 μm in a conventional cyclone to 0.83 μm in a cyclone with a lower cone slit.

Development of a Regression Model of <i>Stk<sub>50</sub>Eu </i>for a Hydrocyclone

A hydrocyclone is a device used widely in various industries, especially for separation of solids from liquids. Many factors affect the separation efficiency of a hydrocyclone. In this research, the main objectives were a study of the conical length that affected the separation efficiency and proposal of a regression model of Stk50Eu for a hydrocyclone. First, research was performed on the separation efficiency using a 40-mm hydrocyclone. The effects of conical lengths of 200, 240 and 280 mm were investigated. The tested suspension was a mixture of silica and water. The silica particles have an average size of 9–10 μm at a solid concentration of 0.5% w/v. The feed-flow rate of 1 m3/hr was operated with the constant flow ratio of 0.1. From the experimental result, it was found that the shorter conical length obtained the higher separation efficiency. For a conical length of 200 mm, the cylindrical length of 60 mm and the vortex finder length of 40 mm showed the best separation efficiency, up to 84.06%. Second, a regression model of Stk50Eu of the hydrocyclone was established. In this work, data obtained from a total of 75 experiments in the first part and from earlier research were used to form the relationship between the dimensions of the hydrocyclone and Stk50Eu. The calculated Stk50Eu can successfully be used to predict experimental Stk50Eu.

Effect of inlet configuration on hydrocyclone performance

Inlet configuration is important parameter of hydrocyclones, which has great impact on the classification performance. The effects of inlet configuration on the precise classification were studied by computational fluid dynamics under various combinations of inlet diameter and inlet velocity. The results showed that a high sharpness of classification was achieved with specific inlet diameter and inlet velocity. The separation efficiency of the coarse particles by underflow significantly decreased when inlet had an oversize diameter owing to a stronger short-circuit flow. It is resulted from the chaotic flow and the stronger pressure gradient around the vortex finder. Meanwhile, a low separation efficiency of the fine particles by overflow was achieved when inlet velocity was high, which indicated a low sharpness caused by the overlarge centrifugal force.

Impacts of the vortex finder eccentricity on the flow pattern and performance of a gas cyclone

Abstract The impact of eccentricity of the vortex finder with deviations in the range of 4–10% on the flow pattern and performance of gas cyclone was studied. The Eulerian-Lagrangian approach in conjunction with the Reynolds stress turbulence model (RSM) of the ANSYS-FLUENT 15 code was used in these simulations. It was found that with increasing deviation of vortex finder up to 10%, the tangential velocity was increased. The maximum tangential velocity obtained for the radial profiles was 1.8 times that of the inlet velocity and the lowest tangential velocity was 1.58 times that of the inlet velocity. The maximum periodic variation in axial and tangential velocities was in the free vortex (central portion of the cyclone). It was shown that increasing the eccentricity of the vortex finder led to an increase in the intensity of oscillation of the axial velocity. For 6% eccentricity, the axial velocity was reduced due to a decrease in the oscillation rate downstream of the cyclone, which is a major factor affecting the cyclone performance. The pressure drop was also increased with increasing eccentricity of the vortex finder. It was found that the gas cyclone with an eccentricity of 8% was more efficient for droplets larger than 1 µm. In this case, also the liquid film flow does not occur on the cyclone wall.

Geometry optimization of a deswirler for cyclone separator in terms of pressure drop using CFD and artificial neural network

Four main geometrical parameters of a deswirler (core diameter, number of vanes, height of vanes and leading edge angle) for cyclone separators have been optimized using CFD and artificial neural network. The results indicated that the most significant geometrical parameters of the deswirler are the number of vanes, the vane angle and the vane height. A new optimized deswirler geometry was obtained using the genetic algorithms and its effects on the flow field, pressure losses and cyclone collection efficiency were numerically investigated. The deswirler positively affects the flow field within a cyclone. It dramatically reduces tangential velocities in the vortex finder and only slightly (by 4.5%) decreases maximum tangential velocities in the separation zone. The deswirler also reduces the length of the inner vortex, redistributes uniformly axial velocities at the vortex finder outlet and prevents backward flow. Additionally, the deswirler converts the dynamic energy of the swirling flow into pressure and allows pressure recovery. It reduces pressure losses in the vortex finder by 95.67% that leads to 43.17% reduction in total pressure drop and slightly decreases the separation efficiency for some particle diameters, increasing the cyclone cut size from 1.5 to 1.72 μm.

Hydrodynamics within flooded hydrocyclones during excursion in the feed rate: Understanding of turndown ratio

Abstract The underflow purity coefficient of a de-oiling hydrocyclone operating at a fixed split ratio is limited by the existence of a finite turndown ratio during excursion in the feed rate. The purpose of this paper is to use advanced computational fluid dynamic methods to identify a hydrodynamic reason for this phenomenon. The results of the simulation show that as the feed Reynolds number increases beyond a critical value, a redistribution of the angular momentum within the hydrocyclone decreases the distance of the zero axial gradient of radial pressure gradient, ( d ( dP / dr ) / dz ) r = 0 = 0 , from the vortex finder, which thereby shortens the length of reverse flow core. The breakdown of reverse flow core at a high feed Reynolds number causes a catastrophic drop in the separation efficiency and possesses a finite turndown ratio. This insight offers guidance on how to maintain separation performance during an excursion in the feed rate.

An alternative for the collection of small particles in cyclones: Experimental analysis and CFD modeling

Abstract The collection efficiency of gas-solid flows in cyclones applied to fine particles is of fundamental importance. In this context, the effects of a reduction in the cross section of the vortex finder outlet duct together with a stretched cylindrical body on the flow pattern and performance of a conventional cyclone was investigated. A test facility and CFD-based modeling using an Eulerian-Lagrangian approach with the Reynolds stress turbulence model (RSM) were employed in experimental and numerical studies, respectively. Based on the results, an alternative design for a cyclone aimed at capturing fine particles (

Effect of cold air stream injection on cyclone performance at high temperature

Abstract A cold air stream was injected into a cyclone operating at a high temperature through slits created in the cylindrical part of the wall. The effects of the cold stream injection on the cyclone performance were investigated by experiment and CFD simulation. The particle deposition on the wall was observed to be closely related to the cyclone wall temperature distribution, with the particles mainly deposited on the high-temperature (>932 K) parts of the wall, and no particle deposition occurring on parts with temperatures lower than 873 K. However, the separation efficiency decreased with increasing flow rate ratio of the cold air stream. This was because the injection of the cold stream caused the bypassing of the hot stream through the vortex finder, thereby decreasing the tangential velocity of the hot gas. Hence, when particle deposition on the wall severely interferes with the operation of a cyclone, the injection of a cold stream can be used to significantly reduce the particle deposition, although this also decreases the separation efficiency and 50% cut size.

Large Eddy Simulation Investigation of an Industrial Cyclone Separator Fitted with a Pressure Recovery Deswirler

AbstractA cyclone fitted with a deswirler of original design has been investigated by means of large eddy simulation. Installation of the deswirler reduces significantly the positive static pressure near the wall as well as the negative static pressure in the central region. It also decreases the maximum tangential velocities in the main separation zone. The deswirler enables a substantial reduction of the backward flow at the gas outlet and a more uniform distribution of the axial velocities at the gas outlet. It also considerably reduces pressure losses in the vortex finder lowering the cyclone pressure drop by almost about one third but it deteriorates the collection efficiency of particles with diameters of less than 8 µm, thus increasing the cut size.

Local linear stability analysis of cyclone separators

Local linear stability analysis is applied to the flow inside a cyclone separator to investigate the unsteady precession of the vortex core. The results of the stability analysis are compared with experimental measurements of the vortex oscillations using high-speed photography with particle seeding and hot-wire anemometry. The experiments reveal distinct spatial variation in the oscillation behaviour within the cyclone. The unsteady motion is focused at each end of the device, at both the narrow cone tip and just below the exhaust duct at the top of the cone, which is known as a vortex finder. The local stability analysis shows that an absolute instability is present throughout the flow for some non-zero azimuthal wavenumbers. The unsteady flow is observed to be driven by coupling between the shear layer and inertial waves confined within the vortex core. Comparison of the stability analysis with experiments shows the same frequency and mode shape behaviour and suggests that the local analysis accurately predicts the unstable modes of the system. The precessing vortex core is responsible for a narrow-band acoustic noise. Comparisons are also drawn with acoustic measurements made on cyclones in which the system is defined by key non-dimensional parameters, such as the swirl number and outlet diameter ratio. The results in this study demonstrate the applicability of local stability analysis to a complex swirling system and yield credible details about the underlying mechanisms of the unstable flow inside the cyclone.

The effect of cross-shaped vortex finder on the performance of cyclone separator

This paper presents a numerical study on a traditional Lapple cyclone separator with the inserted cross-shaped metal blades in the vortex finder. The Reynolds stress model (RSM) is used to simulate the gas flow, and the Lagrangian particle tracking model (LPT) is used to simulate the particle flow. The model is validated by good agreement between the numerical results and experimental data and then is used to simulate cyclones with inserted blades of different dimensions in the vortex finder. The results show that the vortex finder with cross-shaped blades could decrease the pressure drop significantly by 16.41% while improving the separation efficiency slightly by 0.64%. Facilitated by the simulations, the effect of the inserted blades on the flow field in the vortex finder is analyzed, which helps elucidate the mechanisms of the flow field in the vortex finder on the improved performance. It is found that the pressure drop in the vortex finder is generally decreased by the reduction of the vortex core diameter. The variation of the pressure in the vortex finder could change the pressure of the whole cyclone body. The turbulence intensity in the vortex finder and inner vortex have little influence on the separation efficiency, and the increase of the turbulence intensity in the outer vortex will decrease the separation efficiency.

Comparative Analysis of Various CFBC Cyclone Separator REPDS Profiles

In the last decade research on CFBC (Circulating Fluidized Bed Combustion Boiler) has been increased but research on cyclone separator has not been paid well attention. All the existing designs of cyclone separator were mainly concentrating on a single parameter that is collection efficiency. But this work mainly concentrates on other parameters like pressure drop and denudation rate. Previous works related to cyclone separator having REPDS (Reduced Pressure Drop Stick) suggest that 50% REPDS in the vortex finder gives the optimum results for all the existing cyclone models. Existing REPDS profile is only circular; we attempted to change the REPDS profile to polygon shapes like square, hexagonal. All the cyclone separators with different REPDS profile have been designed for flow rate of 500m3/hr with operating velocity of 15m/s. CFD (Computational Fluid Dynamics) analysis has been done with operating velocity ranging from 15m/s to 30m/s, using K-€ turbulence model. The results obtained in CFD analysis reveal that there is no much variation in pressure drop, but there is a drastic change in the denudation rate while operating CFBC cyclone separator twice the designed velocity. Thus REPDS can be included in vortex finder of cyclone separator with any polygon profiles as mentioned above.

Separation efficiency and heat exchange optimization in a cyclone

Abstract This work presents a study on a gas-solid cyclone separator used in a complex cement production plant. The objective of the study consists on the performance evaluation and optimization of the cyclone separator in terms of particle separation and heat transfer efficiencies, while keeping pressure losses under control. The thermal interaction is between two gas-solid mixtures, one feeded at 850 °C and the other at 600 °C, respectively. The solid phase consists, mostly, of calcium carbonate subsequently intended to the so-called baking process for the production of clinker and then cement. The main goal of the study is maximizing the separation efficiency, minimizing the temperature at the exit of the plant and maintain the pressure drop not far from its value in the running plant. In a previous study, the authors defined the suitable setup of the mesh, physical models and turbulence; the same setup has been adopted in the present work during all the optimization phase. Vortex finder length (initially of cylindrical shape), its conicity angle and the pressure losses are the parameters (independent variables), taken into account to optimize the separation efficiency and the temperature of the gas at the exit of the plant. The optimization process was started with the base case that replies the geometric shape of the plant in operation. A detailed overview of the classical and recent optimization methods, is included in the Appendix, together with a brief illustration of a general pattern concerning an optimal design procedure. The numerical approach, for all the cases, is based on implicit unsteady simulations using the Eulerian Multiphase model.

Numerical study of the effect of changing the cyclone cone length on the gas flow field

Models of six different cyclone separator designs have been investigated numerically to study the effect of changing cone length on the gas flow field. The cone length was changed in two ways, one by fixing the cone diameter and the other by fixing the cone angle. The Reynolds stress model was applied to predict the turbulence of gas flow. The model was validated by comparing the numerical results to published experimental data. The results show that, for the cyclone without cylindrical part, the pressure drop and the value of tangential and axial velocity components increase with increasing cone length with fixed cone angle until they reach maximum value. It was found that increasing the cone length with the same cone diameter increases the back flow and the lip leakage below the vortex finder. The back flow and the lip leakage phenomena was observed to be reduced by increasing cone length with fixed cone angle. The effect of contraction ratio Dx/D, which is defined as the ratio between the vortex finder diameter and the cone diameter, on the turbulent kinetic energy and the velocity components also was investigated. As the contraction ratio decreases, the maximum value of the turbulent kinetic energy and the tangential and axial velocity components increases. The pressure drop was fitted into a correlation as a function of dimensionless quantities (Re, Dx/D, and lc/D) for each design, so that the designers could select the appropriate dimensions according to their design limitations.

Analysis of the Influence of Vortexbinder Dimension on Cyclone Separator Performance in Biomass Gasification System

Producer gas produced from biomass gasification still contains particulate ash. It is cleaned by using a cyclone separator. Cyclone separator capability to ‘capture’ ash is characterized by its performance known as collection efficiency. One major factor influencing cyclone separator performance is vortex finder dimension. A cyclone separator model with 2D standard configuration with 150 mm diameter has beenmade. Standard configuration model isused to minimize geometrical factors affecting cyclone separator performance other than vortex finder itself. Three variations of length (3/8 D; 5/8 D; 1 D) and three variations of diameter (35; 70; 85 mm) of vortex finder are used to identify their influences on cyclone performance. Experimental study and CFD simulation using ANSYS Fluent were performed. Experimental study aims to find out vortex finder dimension effects on collection efficiency trend, whileCFD simulation goal is to determine the velocity profile of air inside cyclone separator. RNG k-ɛ for swirl dominated flow was chosen as the turbulence model. Velocity magnitude inside cyclone separator is used to predict the collection efficiency trend. Collection efficiency fromexperimentare determined by weighing method, i.e. percentage of total mass of ash captured divided by total mass of ash entering cyclone separator. Experimental results show that increasing vortex finder length and decreasing vortex finder diameter can increase the collection efficiency. In general, increasing vortex finder length and decreasing vortex finder diameter can also increasethe velocity magnitude of air inside cyclone separator. Highest collection efficiency is achieved by using vortex finder with 35 mm (1/4 D) in diameter and 1 D (150 mm) in length.

Optimization high vortex finder of cyclone separator with computational fluids dynamics simulation

Cyclone separator is an equipment that separates particles contained in the fluid without using filters. The dust particles in the flue gases can be separated by utilizing centrifugal forces and different densities of particles, so that the exhaust gases to be cleaner before discharged into the environment. In this paper carried out a simulation by Computational of Fluids Dynamics to determine the number of particles that can be separated in several cyclone separator which has a ratio body diameter against vortex finder high varied as : 1:0.5 ; 1:0.75 ; 1:1 ; 1:1.25 and 1:1.5. Fluid inlet are air with antrachite impurity particles that are commonly found in the exhaust gases from tire manufacturers with inlet velocities varied as: 15 m/s and 30 m/s. The results of simulation show the fluids with 15 m/s of inlet velocity is generate particle separation value is higher than the fluids with 30 m/s inlet velocity for ratio of body diameter and height vortex finder a: 1:0.5 and 1:1.5. For both of inlet velocities the best ratio of body diameter and height vortex finder is 1:1.25, where it has the highest values of percentage trapped particles about 86% for 30 m/s input velocity and also for 15 m/s input velocity.

Numerical prediction of short-cut flows in gas-solid reverse flow cyclone separators

The effect of operational and geometrical parameters on the short-cut flow in cyclone separators has been investigated computationally using the Reynolds stress model (RSM). The motion of solid particles in the flow field was simulated using the Eulerian-Lagrangian approach with one way discrete phase method (DPM). Eleven cyclones with different cone tip diameters, vortex finder lengths and diameters were studied and the simulation results were analyzed in terms of velocity fields, pressure drops, cut-off diameters and short-cut flows. The numerical simulation was verified with the published experimental results. The results obtained demonstrate that all three parameters, particularly, vortex finder diameter, have significant effects on the cut-off diameter (collection efficiency), the short-cut flow and the pressure drop.

Effect of some operating variables on the performance of a 150 mm Heavy Medium Cyclone treating high ash Indian Coking Coal

Tests were carried out on a 150 mm heavy medium cyclone test rig treating coal in the size range - 13 +0.5 mm. A total of twenty seven experiments were carried out by varying the parameters like vortex finder diameter, spigot diameter and inlet feed pressure. The effect of these variables on the performance of the 150 mm Heavy Medium Cyclone was investigated. The results indicate that it is possible to achieve about 30.1% clean coal at an ash content of 18.5% at a feed pressure of 10 lb/in2, vortex diameter of 63.75 mm and spigot diameter of 31.5 mm. The tromp curves obtained from operating the cyclone gave a probable error of 0.04, indicating good separation efficiency.

Effect of some operating variables on the performance of a 150 mm Heavy Medium Cyclone treating high ash Indian Coking Coal

Tests were carried out on a 150 mm heavy medium cyclone test rig treating coal in the size range - 13 +0.5 mm. A total of twenty seven experiments were carried out by varying the parameters like vortex finder diameter, spigot diameter and inlet feed pressure. The effect of these variables on the performance of the 150 mm Heavy Medium Cyclone was investigated. The results indicate that it is possible to achieve about 30.1% clean coal at an ash content of 18.5% at a feed pressure of 10 lb/in2, vortex diameter of 63.75 mm and spigot diameter of 31.5 mm. The tromp curves obtained from operating the cyclone gave a probable error of 0.04, indicating good separation efficiency.