Cyclone Inlet Research Articles

CFD investigation of the flow and heat transfer characteristics in a tangential inlet cyclone

This work presents a computational fluid dynamics (CFD) calculation to investigate the flow field and the heat transfer characteristics in a tangential inlet cyclone which is mainly used for the separation of the dens phase of a two phase flow. Governing equations for the steady turbulent 3D flow were solved numerically under certain boundary conditions covering an inlet velocity range of 3 to 30 m/s. Finite volume based Fluent software was used and the RNG k−ɛ turbulence model was adopted for the modeling highly swirling turbulent flow. Good agreement was found between computed pressure drop and experimental data available in the literature. The structure of the vortices and variation of local heat transfer were studied under the effects of inlet velocity.

Experimental research on cyclone performance at high temperature

To predict the influence of operating temperatures on cyclone performance, an experimental investigation was conducted on particle separation in a reverse flow, tangential volute-inlet cyclone separator with a diameter of 300 mm and with air heated up to 973 K. The test powder silica has a mass median diameter of 10 um, while inlet velocity range was 12–36 m/s. Both the separation efficiency and pressure drop of the cyclone were measured as a function of the inlet velocity and operating temperature. At the same inlet velocity, both the separation efficiency and pressure drop decrease with increasing temperature. In addition, optimum inlet velocity, at which the cyclone has its highest separation efficiency, tends to increase with a rise in temperature. An analysis on our own data and published results has shown that the fractional efficiency of a cyclone is a definite function of dimensionless numbers such as the Stokes number, the Reynolds number, the Froude number, dimensionless cyclone inlet area, and dimensionless outlet diameter. A nondimensional experimental correlation of the cyclone performance, including the influence of temperature, was obtained on the basis of our own previous work. The prediction of the influence of temperature on separation efficiencies and pressure drops is in fairly good agreement with experimental results.

Girdaplı Akışlarda Türbülans Modellerinin Uygunluğunun İncelenmesi

The aim of this work is to investigate the suitability of various turbulence models in highly complex swirl- ing flows which occur in tangential inlet cyclones. Three dimensional steady governing equations for the incom- pressible, turbulent flow inside the cyclone are solved numerically by using Fluent CFD code, under certain boundary conditions. Different turbulence models and wall functions are tested to get axial and tangential velocity profiles, pressure drop and turbulent quantities. Predicted results are compared with the experimental and numerical values given in the literature. Results obtained from the numerical tests have demonstrated that the key to the success of CFD lies with the accurate description of the turbulent behavior of the flow and the RSM turbulence model performs much better than the other models employed.

Effect of the bottom-contracted and edge-sloped vent-pipe on the cyclone separator performance

Abstract The influence of the bottom-contracted and edge-sloped vent-pipe on the separation efficiency and pressure drop of a cyclone separator under different vent-pipe insert depth and different orientation of the sloped edge were studied in a visual cold circulating fluidized bed (CFB) experimental setup according to a commercial 100 MW CFB boiler with a scale of 20:1. And the correlative results were also compared with the traditional linear-pipe-shaped cyclone separator. Results indicate that the cyclone inlet stream velocity has a strong influence on the separation efficiency and pressure drop, and the results are similar to that of the conventional cyclone. Namely, both separation efficiency and pressure drop increase with increasing cyclone inlet stream velocity. The separation efficiency of the modified cyclone separator increases firstly and then decreases with the increasing of the vent-pipe insert depth. However, there is not a very clear rule of the effect of vent-pipe insert depth on the pressure drop for modified cyclone separator. Both the separating efficiency and the pressure drop change with the orientation of the sloped edge, and they have the same rule of change, the maximum at 90° and the minimum at 270°. Due to the configuration of the bottom-contracted and edge-sloped vent-pipe is suitable with the flow field inside cyclone separator, the separation efficiencies of the modified cyclone separator are usually higher than those of traditional cyclone separators.

A Study on Flow Performance of Axial Inlet Cyclone for Dust Collector

In this study, numerical analysis to develop optimal dust collector having an axial inlet cyclone was performed for the 3 dimensional flow field with a control volume including gases and particles. We applied FVM(Finite Volume Method) for calculating the flow distribution and the pressure drop into the control volume using a commercial code FLUENT. The k-ε turbulence model was used to obtain the analytical results and the major parameters were the geometrical dimension of helical guide vanes, the inner diameter and length of cylindrical part. Particle trajectory calculations were performed for the particle sizes of 5~75㎛ corresponding to KS A 0090. Finally we found out and recommended one dust collector that showed appreciable performance improvement. The experiment for confirming the numerical results was conducted by KS R 1041. From the numerical analysis and the experimental test, it was seen that the specified collector recommended in this study had dust collecting rate of about 99.91% and the pressure drop of 23.9mbar, and was more effective than old one that had been conventionally used in real work field.

An axial flow cyclone to remove nanoparticles at low pressure conditions

In this study, the axial flow cyclone used in Tsai et al. (2004) was further tested for the collection efficiency of both solid (NaCl) and liquid (OA, oleic acid) nanoparticles. The results showed that the smallest cutoff aerodynamic diameters achieved for OA and NaCl nanoparticles were 21.7 nm (cyclone inlet pressure: 4.3 Torr, flow rate: 0.351 slpm) and 21.2 nm (5.4 Torr, 0.454 slpm), respectively. The collection efficiencies for NaCl and OA particles were close to each other for the aerodynamic diameter ranging from 25 to 180 nm indicating there was almost no solid particle bounce in the cyclone. The 3-D numerical simulation was conducted to calculate the flow field in the cyclone and the flow was found to be nearly paraboloid. Numerical simulation of the particle collection efficiency based on the paraboloid flow assumption showed that the collection efficiency was in good agreement with the experimental data with less than 15% of error. A semi-empirical equation for predicting the cutoff aerodynamic diameter at different inlet pressures and flow rates was also obtained. The semi-empirical equation is able to predict the cutoff aerodynamic diameter accurately within 9% of error. From the empirical cutoff aerodynamic diameter, a semi-empirical square root of the cutoff Stokes number, √St 50 * , was calculated and found to be a constant value of 0.241. This value is useful to the design of the cyclone operating in vacuum to remove nanoparticles.

A universal model to calculate cyclone pressure drop

The definition and composition of the pressure drop over a tangential inlet, reverse flow cyclone have been analyzed. It is assumed that two factors mainly contribute to the pressure drop, i.e., the local loss and the loss along the distance. The former includes the expansion loss at the cyclone inlet and the contraction loss at the entrance of the outlet tube (or vortex finder). The latter consists of the swirling loss resulting from friction at the cyclone walls and the dissipation of gas dynamic energy in the outlet tube. By use of the measured results of the flow field in cyclones, the calculation methods for each loss have been developed. And a universal model to predict the cyclone pressure drop is thus obtained simply by summing each loss. A detailed comparison between the calculated and experimental results shows that this accurate model is suitable either for pure or for dust laden gases at normal or high temperatures and can meet the requirement of most cyclone designs.

Analysis of Aerosol Particles and Coarse Particulate Matter Concentrations in Chillán, Chile, 2001–2003

Daily particle samples were collected in Chillán, Chile, at six urban locations from September 1, 2001, through September 30, 2003. Aerosol samples were collected using monitors equipped with a Sierra Andersen 246-b cyclone inlet on Teflon filters. Average concentrations of coarse particulate matter (PM10) for the 2001–2003 period ranged from 43.4 μg/m3 to 81.8 μg/m3 across the six sites. Annual PM10 concentration levels exceeded the European Union concentration limits. Mean PM10 levels during the cold season (April through September) were more than twice as high as those observed in the warm season (October through March). Average contributions to PM10 from organic matter, soil dust, nitrate (NO3 −), elemental carbon, ammonium (NH4 +), and sulfate (SO4 2−) were 31%, 27%, 11%, 8%, 7%, and 5%, respectively. The chemical analyses indicated that carbonaceous substances were the most abundant components of PM10 in cold months, whereas crustal material was the most abundant component of PM10 during warm months. Higher concentration levels were observed in the downtown area suggesting a clear anthropogenic origin, whereas in the rural sites the source was mainly natural, such as resuspended soil dust associated with traffic on unpaved roads and agricultural activities.

Studies on Gas-Solid Heat Transfer in Cyclone Heat Exchanger

Abstract Cyclones can be used for heating solid particles where the direct contact with the gas is permitted. Since cyclones have potential applications as heat exchangers in fertilizer, polymer powder, pharmaceutical and other industries, study of cyclone as heat exchanger is deemed important. Experiments on air-solid heat transfer were carried out in a cyclone heat exchanger of 100mm inside diameter, using sand. The effects of solid feed rate (0.5-7.5g∕s), cyclone inlet air velocity (9-22m∕s), and four average particle sizes (163-460μm) on the heat transfer rate, exit solid temperature, and heat transfer coefficient have been studied. An empirical correlation has been proposed for the prediction of heat transfer coefficients based on the present experimental data. The proposed correlation predicts the heat transfer coefficients with an error of +10%to−15% for the present data and within an error of +25%to−15% for the data of other investigators.

Continuous Collection of Soluble Atmospheric Particles with a Wetted Hydrophilic Filter

Approximately one-third of the area (14-mm diameter of a 25-mm diameter) of a 5-microm uniform pore size polycarbonate filter is continuously wetted by a 0.25 mL/min water mist. The water forms a continuous thin film on the filter and percolates through it. The flowing water substantially reduces the effective pore size of the filter. At the operational air sampling flow rate of 1.5 standard liters per minute, such a particle collector (PC) efficiently captures particles down to very small size. As determined by fluorescein-tagged NaCl aerosol generated by a vibrating orifice aerosol generator, the capture efficiency was 97.7+% for particle aerodynamic diameters ranging from 0.28 to 3.88 microm. Further, 55.3 and 80.3% of 25- and 100-nm (NH4)2SO4 particles generated by size classification with a differential mobility analyzer were respectively collected by the device. The PC is integrally coupled with a liquid collection reservoir. The liquid effluent from the wetted filter collector, bearing the soluble components of the aerosol, can be continuously collected or periodically withdrawn. The latter strategy permits the use of a robust syringe pump for the purpose. Coupled with a PM2.5 cyclone inlet and a membrane-based parallel plate denuder at the front end and an ion chromatograph at the back end, the PC readily operated for at least 4-week periods without filter replacement or any other maintenance.

Modelling of the Pressure Drop in Tangential Inlet Cyclone Separators

This article introduces a new mathematical model that predicts the pressure drop in a tangential inlet cyclone. The model calculates the pressure drop from the frictional losses in the cyclone body, using a wall friction coefficient based on the surface roughness and Reynolds number. The entrance and exit losses are also included in the model by defining new geometrical parameters. The pressure drop coefficient is obtained as a function of cyclone dimensions and operating conditions. The model is validated by studying 12 different cyclones presented in the literature. Comparison of the model results with predictions and measurements published in the literature show that the new model predicts the experimental results quite well for a wide range of operating conditions covering a flow rate of 0.3–220 l/s and a temperature range of 293–1200°K, in different cyclones. The pressure drop coefficient is also examined in view of the outlet pipe diameter, friction coefficient, surface roughness, and Reynolds number.

COMPUTATIONAL STUDY OF CYCLONE FLOW FLUID DYNAMICS USING A DIFFERENT INLET SECTION ANGLE

The conventional design of the cyclone model has been used without significant modifications for about a century. Recently, some studies were carried out to improve equipment performance by evaluating the geometric influence of the tangential inlet section and scroll inlet duct design. In this work, the influence of cyclone inlet section geometry was studied using an angle of 45 degrees in relation to the cyclone body. The study was conducted for the gas and gas-particle phases, based on an experimental study available in the literature, where a conventional inlet section was used. Numerical experiments were carried out with the CFX computational code. The fluid dynamics profiles and tangential velocity component were evaluated for three inlet velocities (2.75, 7.75 and 15.2 m/s) using the Reynolds Stress model. The results showed that this proposal is useful for improving the cyclone performance.

COMPUTATIONAL STUDY OF CYCLONE FLOW FLUID DYNAMICS USING A DIFFERENT INLET SECTION ANGLE

The conventional design of the cyclone model has been used without significant
modifications for about a century. Recently, some studies were carried out to improve
equipment performance by evaluating the geometric influence of the tangential inlet section
and scroll inlet duct design. In this work, the influence of cyclone inlet section geometry
was studied using an angle of 45 degrees in relation to the cyclone body. The study was
conducted for the gas and gas-particle phases, based on an experimental study available in
the literature, where a conventional inlet section was used. Numerical experiments were
carried out with the CFX computational code. The fluid dynamics profiles and tangential
velocity component were evaluated for three inlet velocities (2.75, 7.75 and 15.2 m/s)
using the Reynolds Stress model. The results showed that this proposal is useful for
improving the cyclone performance.

A new semi-empirical model for predicting particulate collection efficiency in low-to-high temperature gas cyclone separators

Abstract A new semi-empirical model has been developed to predict particulate collection efficiency in low-to-high temperature gas cyclone separators. It has been tested at 20 and 600°C using various flow rates and dust loadings. The model is particularly suitable for efficiency predictions in cyclones attached to fluidized bed gasifiers using rice husk as feedstock, where de-volatilization, which occurs in the temperature range 300-600° C, is the major contributor to gasification of the feedstock, which is 70-90% volatile matter. To develop the particulate collection model, the cylinder-on-cone reverse-flow gas cyclone separator was geometrically modeled as an equivalent right circular cylinder, which was then divided into three zones, reflecting the main hydrodynamically distinct flow zones that result after dust-laden gas enters the device, i.e. inlet, outer (free) vortex and inner (forced) vortex zones. Mass balance computations were then carried out using residence time as the independent parameter, in order to determine the dust loadings in the various zones and subsequently compute the capture efficiency of each particle size in the polydisperse flow. This approach contrasts with ones in which the cyclone is either viewed as one cylindrical region or else, when multiple zones are employed, the axial location in the cyclone, as opposed to residence time, is utilized as the independent variable in mass balance computations. The effects of cyclone inlet temperature, gas flow rate and dust loading on particulate collection efficiency are incorporated in the model equations, along with the cyclone's geometric parameters. In validation of the model, comparisons were made with widely used models in the literature, the new model being shown to produce predictions of grade efficiencies in closer agreement with the experimental data than those by the other models. Thus, the current model constitutes a significant contribution to current knowledge of the particulate capture process in gas cyclone separators.

Axial inlet cyclone for mineral processing applications

An axial inlet cyclone was developed and tested for wet size classification of particulate materials with the purpose of providing an alternative to the tangential inlet cyclone used traditionally in the mineral processing industry. The proposed device shared many of the fundamental features of a conventional cyclone, but had a circular opening on the roof of the cylindrical section and surrounding the vortex finder for feed entry, instead of a tangential inlet. The feed material spiraled down through that opening and generated the necessary spin for separation inside the cyclone. Experimental work was carried out on a sample of copper–nickel mill tailings having a particle size of 91% passing 300 μm, and the performance of the cyclone was evaluated at different inlet pressures, feed pulp densities and vortex finder lengths. In comparison to the tangential inlet cyclone, the axial inlet cyclone provided higher throughputs, coarser cut-sizes in relatively dilute pulps, and greater flexibility and control over the cyclone separation process.

03/01880 Size and chemical characteristics of fine particulate emissions from oil and coal-fired pilot scale boilers: Lee, S. W. et al. Preprints of Symposia - American Chemical Society, Division of Fuel Chemistry, 2002, 47, (2), 679–680

Introduction The Canada Wide Standards for particulate matter (PM) was proposed in Canada in 2000, soon after the publication of the new US National Ambient Air Quality Standards in 1997 . Subsequently, increased research activities were noted in the following years in addressing the apparent knowledge gaps related to fine PM emissions. Measuring PM2.5 and PM10 emissions from combustion sources began to replace the traditional means of monitoring and reporting of total suspended particulates. Identification and quantification of PM from regional point sources are critical in controlling the PM emissions effectively at source as well as in apportioning the ambient PM concentrations to the contributing local sources. A new methodology was developed to determine fine PM emissions under plumesimulating conditions that are comparable to ambient PM characteristics. The method, unlike traditional high temperature measurement methods, applies initial cooling of the flue gas by diluting with clean air inside an inert tunnel to mimic plume conditions. The source dilution approach allows for atmospheric transformation processes for the PM and thus provides ambientcomparable source signature profiles for source apportionment modeling. At present, fine PM data from industrial sources are limited and often not representative of reality, being derived from high temperature source measurement techniques. Research is being co-sponsored by two Canadian utilities, Environment Canada with the objective of examining source PM characteristics from the electric power generation sector. Two prototype samplers have been developed for the combustion units having low stack velocities (<5 m/s) and medium velocities (<10 m/s). The larger sampler is being retrofitted for field measurement on utility-scale boilers. The basic sampling protocol involves dilution of flue gas with purified air by 20 to 40 times inside a dilution chamber maintained at a 40% relative humidity (RH) to allow for cooling and simulation of atmospheric transformation processes. Portions of the diluted gas are withdrawn, while maintaining isokinetic sampling, through selected cyclone and impactor inlets and filter packs to collect the PM fractions. The method provides mass concentrations of PM2.5, PM10 and total PM and their size and chemical composition information. To date, fine PM emissions from the combustion of No. 2 and No. 4 heating fuels and pulverized coal have been determined and characterized using the two samplers. The paper summarizes the preliminary size and chemical characteristic data from the combustion of three experimental fuels.

Characteristics of the collection efficiency for a double inlet cyclone with clean air

Two single inlet cyclones and a double inlet cyclone were designed and fabricated to evaluate, and compare, their collection efficiencies. Two single inlet cyclones had different inlet sizes and vortex finder diameters. The double inlet cyclone had two inlet parts that divided the cyclone inlet in two. Clean air was introduced to the inlet near the cyclone wall, and particle-laden air was introduced to the inlet away from the cyclone wall. This double inlet made the clean air swirl in the region near the vortex finder, and the particle-laden air swirl in the region close to cyclone wall. The performance of the double inlet cyclone was evaluated at various clean air flow rates, keeping the particle-laden air flow rate constant. The collection efficiency of the double inlet cyclone was found to be 5–15% greater than that of the single inlet cyclone with the same inlet size and vortex finder diameter. As the flow rate of clean air was increased, the collection efficiency increased. This result indicates the possibility of achieving higher collection efficiencies with a double inlet cyclone.

Effects of flow and geometrical parameters on the collection efficiency in cyclone separators

A mathematical model has been developed for calculation of cut-off size and fractional efficiencies in cyclone separators, by taking into account the effects of flow, particle and geometrical parameters, and acceleration assuming that the mixture of fluid and particles is homogenous, and acceleration diminishes depending on the friction and geometry. Collection efficiency curves and cut-off size values predicted by the proposed model showed a good agreement with experiments over a wide range of inlet velocities for different types of cyclones. Comparison of the obtained results with semi empirical models available in literature also indicated that the present model may be used successfully for determination of the performance of a tangential inlet cyclone. Analyses of the effects of various parameters reveals that, in addition to flow and geometrical parameters, surface friction, vortex length and flow regimes play an important role on cyclone performance especially in small cyclones.

Analysis on cyclone collection efficiencies at high temperatures

In order to predict the influence of operating temperature on cyclone performance, an experimental investigation on particle separation was conducted in a 300 mm diameter, tangential volute-inlet and reverse flow cyclone separator with air heated up to 973 K. The test powder silica has a mean mass diameter of 10 microns and the inlet velocity ranges from 12 m·s −1 to 36 m·s −1. Both the overall efficiency and fractional efficiency of the cyclone were measured as a function of the inlet velocity and operating temperature. It is shown that at the same inlet velocity both the overall efficiency and fractional efficiency decrease with an increase of temperature. An analysis of our own data and published results has shown that the fractional efficiency of a cyclone is a definite function of such dimensionless numbers as Stokes number, Reynolds number, Froude number and dimensionless cyclone inlet area and dimensionless outlet diameter. A nondimensional experimental correlation of the cyclone performance, including the influence of the temperature, was obtained on the basis of our own previous work. The prediction of the influence of temperature on separation efficiencies is in fairly good agreement with experimental results.

Effect of apex cone height on particle classification performance of a cyclone separator

Abstract Experimental and simulation studies have been conducted about the effect of apex cone height on particle separation performance of a cyclone separator. It is found that the effect of an apex cone is to decrease the cut size and to increase the collection efficiency. The cut size indicates the minimum value for the specific height of the apex cone. The optimum apex cone height changes to the lower position as the cyclone inlet velocity increases. When the apex cone is set to the high position, the resistance of an incoming particle entering to the dust box increases. The low apex cone position induces a strong upward fluid flow component and increases the number of escaping particles from the dust box. The magnitude of fluid velocity in the upper part of the dust box decreases under the optimum apex cone height condition. The experimental data agreed with the numerical simulation based on the direct flow calculation method.