Flow Field Of Cyclone Research Articles

Transport hydrodynamics of catalytic particles in gradient cyclonic flow field and reaction characteristics to produce bio-oil

For the purpose of improving product yield and reducing energy consumption, a novel cyclonic integrated catalytic process was established for the biomass vapors upgrading based on simultaneous reaction-separation technology. In order to gain better insights into the biomass pyrolysis vapors upgrading in this heterogeneous system of novel gradient cyclonic flow field, the particle transport hydrodynamics, the product distribution characteristics and operating parameters effects in the newly developed uniflow cyclone reactor were explored by experimental and numerical simulation methods. The results demonstrate that the gradient cyclonic flow field has a positive effect on the contact efficiency and separation effect, and then beneficially promote catalytic reactions. During the movement of catalysts in the gradient cyclonic flow field, a catalyst-cluster is observed near the top of the reactor with a dense “body” and a dilute “shadow”. The characteristics of secondary vortexes and solid concentration distribution on radial and axial directions were further explained. The optimal reaction temperature, reaction time and catalyst to vapors mass ratio to produce bio-oil respectively are 550 °C, 1.5 s and 24.0. This work provides theoretical basis for optimization of reactor structure and operation parameters. It is beneficial to the improvement of biomass catalytic pyrolysis technology.

Experimental and simulation results of gasification of biomedical waste and Indian palm kernel shell in a fluidized bed gasifier under steam atmosphere

Gasification is the process that converts the stored energy in biomass into useful energy. In this study, a fluidized bed gasifier is used to steam gasify Biomedical Waste (BMW) such as face shields, air respirators, syringes, hand gloves, glucose plastic bottles, gowns, aprons and Indian Palm Kernel Shell (PKS). An experimental investigation is carried out in which, the co-gasification of Indian PKS and BMW in the ratio of 80PKS:20BMW, 60PKS:40BMW, 40PKS:60BMW, 20PKS:80BMW are used to synthesize producer gas from a Fluidized Bed Gasifier (FBG) using mineral olivine is a magnesium iron silicate (Mg2+, Fe2+) 2SiO4 as a main catalytic agent. Co-feeding BMW with PKS is studied for its effects on gas, char, tar yield, carbon conversion efficiency, tar and gas composition. The tar and char yield are reduced but gas yield is increased for co-gasification of BMW and PKS. The carbon conversion efficiency of 80PKS:20BMW and 20PKS:80BMW has increased to 77.7% and 97% respectively. The H2 and CO content are increase for 20PKS:80BMW but methane, carbon dioxide and ethylene content are drops because of the usage of olivine as a main catalytic agent. The cyclone flow field pattern has been simulated and analyzed with the aid of velocity components and static pressure. It is found that the separation effect on small particles size ratio and pressure drop is reduced by 41% and 13.3% respectively. Whereas the separation efficiency is improved, the overall performance of the separator is also improved and the energy consumption is reduced.

On the generalized Beltramian motion of the bidirectional vortex in a right-cylindrical cyclone with a hollow core

In this work, an exact inviscid solution is developed for the incompressible Euler equations in the context of a bidirectional, cyclonic flowfield in a right-cylindrical chamber with a hollow core. The presence of a hollow core confines the flow domain to an annular swirling region that extends into a toroid in three-dimensional space. The procedure that we follow is based on the Bragg–Hawthorne framework and a judicious assortment of boundary conditions that correspond to a wall-bounded cyclonic motion with a cylindrical core. At the outset, a self-similar stream function is obtained directly from the Bragg–Hawthorne equation under the premises of steady, axisymmetric, and inviscid conditions. The resulting formulation enables us to describe the bidirectional evolution of the so-called inner and outer vortex motions, including their fundamental properties, such as the interfacial layer known as the mantle; it also unravels compact analytical expressions for the velocity, pressure, and vorticity fields, with particular attention being devoted to their peak values and spatial excursions that accompany successive expansions of the core radius. By way of confirmation, it is shown that removal of the hollow core restores the well-established solution for a fully flowing cylindrical cyclone. Immediate applications of cyclonic flows include liquid and hybrid rocket engines, swirl-driven combustion devices, as well as a multitude of heat exchangers, centrifuges, cyclone separators, and flow separation devices that offer distinct advantages over conventional, non-swirling systems.

Effects of Inlet Types and Lengths on the Flow Field of Cyclone Separators

The effect of inlet type and length on the flow field was considered computationally for seven cyclone separators. The turbulent model was described by the Reynolds Stress Model (RSM). The air-water interface in underflow pipe and the spatial distribution of particles were tracked by the Volume of Fluid (VOF) model and Discrete Phase Model (DPM), respectively. Comparison investigations showed that inlet type and length had important impacts on flow field of cyclone. The instability flow field and back mixing phenomena were eliminated in symmetric double-inlet cyclone. The turbulent dissipation is obvious with a short inlet length. When it increased to 1.25D/2, the area and intensity of the turbulent dissipation tended to be stable. The optimum cyclone is the symmetric double-inlet with inlet length of 1.25D/2. When the particle diameter was larger than 5 μm, the complete separation could be realized.

Dominant Modes in a Gas Cyclone Flow Field Using Proper Orthogonal Decomposition

Dominant Modes in a Gas Cyclone Flow Field Using Proper Orthogonal Decomposition

Energy balance formation of sub-eutectoide fayalita at high pressures in particle separators

This article presents an approach to the problem of ceramic types adhesion, applying energy and matter balance to the established control volume (cyclone) with the use of mathematical formulas that are interrelated to develop mathematical calculations and establish a new mathematical model The first results are obtained by operating the energy balance considering the collision of particles, using the principle of conservation of energy, the first law of thermodynamics, in order to obtain information that allows describing the phenomena of thermoplasticity and creep, in the formation of adhesions, from a physicochemical and kinetic point of view, which will serve as the basis for understanding their effect. As a result, an energy value of 660 kJ / mol was obtained, sufficient energy to start the transformation of the solid particles to a state of thermo-flow that allows the adhesion phenomenon to be started.
 Keywords: Adhesion, energy balance, cyclones, elutriation, eutectoid, fayalite, thermoplasticity.
 References
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Exact Beltramian solutions for hemispherically bounded cyclonic flowfields

This study focuses on the development of two analytical models that describe the wall-bounded cyclonic flowfield in a hemispherical domain. The closed-form solutions that we pursue are motivated by the need to characterize the swirling bidirectional motion engendered in an upper stage thrust chamber, namely, the VR35K-A VORTEX® engine, conceived and developed by Sierra Nevada Corporation. Our analysis proceeds from the Bragg–Hawthorne formulation, which is quite effective in the treatment of steady, inviscid, and axisymmetric flows. In this work, we show that two rotational solutions may be derived for particular specifications of the stagnation head and tangential angular momentum expressions that appear in the Bragg–Hawthorne equation. Then, with the parental streamfunctions in hand, other properties of interest are deduced and these include the main velocity and pressure variations, vorticities, crossflow velocities, extensional and shearing strain rates, virtual energy dissipation rates, and both axial and polar mantle distributions; the latter consist of pairs of rotating, non-translating interfacial layers, separating the so-called inner and outer bidirectional and bipolar regions, respectively. More specifically, two Beltramian solutions are identified with mantles that appear at 50% and 61.06% of the chamber radius, respectively. By matching the outlet radius of the chamber to the mantle location in the equatorial plane, the outflow is permitted to exit the chamber seamlessly. In both models, the axial and radial velocities vary linearly with the injection speed and a characteristic inflow parameter consisting of a geometric ratio of the inlet area and the chamber radius squared.

A quasi complex-lamellar solution for a hemispherically bounded cyclonic flowfield

This work describes an inviscid solution for a cyclonic flowfield evolving in a hemispherical chamber configuration. In this context, a vigorously swirling motion is triggered by a gaseous stream that is introduced tangentially to the inner circumference of the chamber's equatorial plane. The resulting updraft spirals around while sweeping the chamber wall, reverses direction while approaching the headend, and then tunnels itself out through the inner core portion of the chamber. Our analysis proceeds from the Bragg–Hawthorne formulation, which proves effective in the treatment of steady, incompressible, and axisymmetric motions. Then using appropriate boundary conditions, we are able to obtain a closed-form expression for the Stokes streamfunction in both spherical and cylindrical coordinates. Other properties of interest are subsequently deduced, and these include the principal velocities and pressure distributions, vorticity, swirl intensity, helicity density, crossflow velocity, and the location of the axial mantle; the latter separates the outer annular updraft from the inner, centralized downdraft. Due in large part to the overarching spherical curvature, the cyclonic motion also exhibits a polar mantle across which the flow becomes entirely radial inward. Along this lower and shorter spherical interface, the polar velocity vanishes while switching angular direction. Interestingly, both polar and axial mantles coincide in the exit plane where the ideal outlet size, prescribed by the mantle position, is found to be approximately 70.7% of the chamber radius. We thus recover the same mantle fraction of the cyclonic flow analog in a right-cylindrical chamber where an essentially complex-lamellar motion is established.

Numerical study of flow field in new design cyclones with different wall temperature profiles: Comparison with conventional ones

In this paper, numerical study of flow field in the new design cyclones with five different wall temperature profiles are investigated. The new design cyclone is based on the idea of improving cyclone collection efficiency and pressure drop by increasing the vortex length. In this paper, the five wall temperature profiles are as follows: (A) cooling with uniform distribution, (B) without temperature change, (C) heating with uniform distribution, (D) incremental linear heating, (E) reduction linear heating. Results are compared in new design and conventional cyclones. The Reynolds averaged Navier–Stokes equations with Reynolds stress turbulence model (RSM) are solved. The Eulerian-Lagrangian computational procedure is used to predict particles tracking in the cyclones. The velocity fluctuations are simulated using the Discrete Random Walk (DRW).Results show that generally, heating the bottom zone of the cyclones can improve the collection efficiency and reduce the pressure drop while heating the top zone of the cyclones marginally affects the flow field. Moreover, cooling the cyclones reduces the efficiency and causes a higher pressure drop. Among five different wall temperature profiles, C and E profiles can increase the efficiency about 8% and profile C reduces the pressure drop by about 9%. The mentioned values in different conditions including particle diameter, flow rate, etc. can be different.

An exact irrotational solution for a hemispherically bounded cyclonic flowfield

This study focuses on the development of an internal potential flow solution in the context of a hemispherically bounded cyclonic chamber. The analysis proceeds from the Bragg–Hawthorne equation, which is quite effective in the treatment of steady, inviscid, and axisymmetric flows when expressed in terms of the streamfunction. Once the streamfunction is obtained, other flow properties are readily deduced; these include the principal velocity and pressure distributions, swirl intensity, crossflow velocity, and mantle location. Furthermore, given the overarching spherical geometry, two different types of mantles are identified and related to the coexistence of axially bidirectional and circularly bipolar regions. The first, axial mantle, which is traditionally used in the analysis of cylindrical and conical cyclone separators, consists of a rotating, non-translating interfacial layer along which the axial velocity vanishes. It thus separates the outer, vertical updraft, from the inner, swirling downdraft. The second, polar mantle, which arises in the context of a hemispherical flow configuration, coincides with the spherical interface along which the polar velocity vanishes. It hence partitions the flow domain into a much larger outer region, where the flow direction remains strictly counterclockwise, and a proportionally smaller inner region, where the outflow becomes clockwise. Despite their dissimilar structures, both axial and polar mantles meet in the exit plane at a fractional radius of 1/e2 or 13.53%. In this study, the unique characteristics of the resulting irrotational motion, which reduces to a continuously looping, hemispherically cyclonic potential vortex, are evaluated and discussed.

Effect of cylinder vortex stabilizer on separator performance of the Stairmand cyclone

The phenomena of precessing vortex core (PVC), entrainment of particles from the ash hopper, and swing of the vortex end in swirling flow have a negative effect on flow field and separation performance of cyclone. In order to alleviate these negative effects, a strategy to improve flow structure by installing cylinder vortex stabilizer is proposed, and the effects of different size stabilizers on the performance of cyclones are studied by experiment and CFD simulation. The results show that cylinder vortex stabilizer can improve the stability of the vortex in the cyclone, by reducing the impact of PVC, entrainment of particles from the ash hopper, and swing of the vortex end. This improves collection efficiency of fine particles, with an increase of 5.52% for particles whose diameters are smaller than 3 μm. The stabilizer has little effect on the pressure loss of the cyclone, with an increase of only 3.61%.

Effects of vortex finder length on flow field and collection efficiency of cyclone in an industrial‐scale circulating fluidized bed boiler: Numerical study

Effects of vortex finder length on flow field and collection efficiency of cyclone in an industrial‐scale circulating fluidized bed boiler: Numerical study

Flow and reaction characteristics on catalytic upgrading of biomass pyrolysis vapors in novel cyclone reactors

To improve the catalytic upgrading efficiency of biomass pyrolysis vapors and reduce secondary cracking of aimed products in current conventional reactors, a novel cyclone reactor was designed for the gas (biomass pyrolysis vapors)-solid (catalysts) heterogeneous reaction. The contact effect of gas-solid two-phase could be increased in the cyclonic flow field, and the separation between the gas products and catalysts occurs while flowing down due to the centrifugal force in short residence time. The rapid separation reduces secondary cracking effectively. In this study, the catalytic upgrading of pyrolysis vapors in the cyclone reactor were investigated from the aspect of fluid dynamics, residence time distribution and catalytic reaction by CFD simulation combining with the experimental method. The results indicate that in the reaction chamber of the cyclone reactor the concentration gradient of catalysts decreases gradually while flowing down. The cyclonic flow is intensified due to the guided vanes in the middle part of the reactor, and the separation effect is improved remarkably. The effects of outlet structures were investigated based on the residence time distribution and the product selectivity, the structure of Case 2 that has a vertical catalyst outlet and a horizontal gas outlet is better. The residence time of catalysts in Case 2 is 1.0s–2.0s. And the overall mass fraction of the bio-oil is 54%.

Effect of External Cyclone Diameter on Performance of a Two-Stage Cyclone Separator.

As a widely used separation device, a cyclone separator is especially important to improve its separation efficiency. In this paper, a new two-stage cyclone separator is designed and modeled by the Reynolds stress model. Under the premise of determining the diameter of the second-stage cyclone (D), the effects of five first-stage cyclone diameters (Du) on the performance of the two-stage cyclone are simulated. The performance of the single-stage cyclone separator is also obtained. The results show that Du has significant effects on the internal pressure field, flow field, and vortex core of the two-stage cyclone. Compared with the single-stage cyclone separator, the separation efficiency of the two-stage cyclone separator is significantly improved. When Du = 6D, the separation efficiency is improved by 15.5% compared with that of the single-stage cyclone. In addition, the two-stage cyclone separator can effectively reduce the Euler number.

Turbulence Models for Single Phase Flow Simulation of Cyclonic Flotation Columns

Cyclonic fields are important for cyclonic static microbubble flotation columns (FCSMCs), one of the most important developments in column flotation technology, particularly for separation of fine particles, where the internal flow field has enormous influence on flotation performance. PIV (particle image velocimetry) and CFD (computational fluid dynamics) are the most effective methods to study flow fields. However, data is insufficient for FCSMC flow fields and similar cyclonic equipment, with turbulence model simulations producing different views to measured data. This paper employs an endoscope and PIV to measure axial and cross sections for single-phase swirling flow fields in FCSMCs. We then compare various turbulence model simulations (Reynolds stress model (RSM), standard k-ε, realizable k-ε, and RNG (renormalization group) k-ε) to the measured data. The RSM (Reynolds stress model) predicts cyclonic flow field best in flotation columns with 16.22% average relative velocity deviation. Although the realizable k-ε model has less than 30% relative deviation in radial and tangential directions, axial deviations reach 78.11%. Standard k-ε and RNG k-ε models exhibited approximately 40% and 30% radial and tangential deviation, respectively, and cannot be used even for trend predictions for axial velocity. k-ε models are based on isotropic assumptions with semi-empirical formulas summarized from experiments, whereas RSM fundamentally considers laminar flow and Reynolds stress, and hence is more suitable for anisotropic performance. This study will contribute to flotation column and other cyclonic flow field equipment research.

The effect of inlet shape on separation performance and flow‐field characteristics in a gas–solid cyclone separator

AbstractThe gas–solid separation experiments were conducted to compare separation performance between cyclone separators with different inlet shapes. Besides, the Reynolds stress model was employed to simulate flow field in different cyclones. The results revealed that the cyclone with a trapezoidal inlet could enhance separation efficiency without almost increasing pressure drop. Compared with the conventional rectangular inlet, a trapezoidal inlet had negligible effect on flow field of cyclone's separation space, and it reduced lip flow and upper dust ring of cyclone. In addition, the cyclone with a trapezoidal inlet could improve the inhomogeneous gas flux distribution at the inlet, which was the root reason why secondary flows in cyclone were inhibited and separation efficiency was enhanced.

Experimental and CFD study on effects of spiral guide vanes on cyclone performance

This paper presents an experimental and numerical study on a tangential inlet cyclone separator with a spiral guide vane which is not often researched. Numerical pressure drop results were in close agreement with the experimental data. The spiral guide vane was also found to considerably influence the velocity distribution, turbulence intensity, pressure drop and collection efficiency in the cyclone. A critical value of spiral guide vane turns appeared below or above which there was a marked increase in collection efficiency, pressure drop, and tangential velocity. Compared to a cyclone with zero spiral guide vane turn, the maximal decrease in collection efficiency in the cyclone with the critical spiral guide vane turns (one turn) was 2% approximately. The maximum-efficiency inlet velocity appeared to exist independent of spiral guide vane turns, as inlet velocity affected the radial distance traveled by the rebounded particles from the inner wall. The analysis of flow field in cyclones indicated that the flow field was improved with the spiral guide vanes employed to some extent. The results presented here may provide a workable reference for the effects of spiral guide vanes on the flow field and corresponding performance in cyclone separators.

Influence of preheating and thermal power on cyclonic burner characteristics under mild combustion

Autoignition and stabilization of distributed combustion regimes have been proved to occur when a sufficient entrainment of hot species in the fresh reactants jets is reached, thus providing simultaneously for the sensible enthalpy to promote the auto-ignition process and the mass to dilute the incoming fresh reactants.The present study investigates the stabilization process along with the performance of the combustion process in a cyclonic burner operated under MILD combustion conditions. The cyclonic flow has been achieved by means of two pairs of oxidant/fuel jets injected using an anti-symmetric configuration in a prismatic combustion chamber thus realizing a centripetal cyclonic flow field directed toward the top-central gas outlet.Propane/air combustion experimental campaigns without external dilution, on a detailed grid of equivalence ratio and preheating temperature values, at different average residence time and nominal thermal power values were made. In each test condition, temperature measurements inside the chamber and gas sampling analyses have been carried out in order to evaluate the operability range of the cyclonic burner and its performances. These tests allowed to demonstrate the feasibility of stable MILD Combustion regimes in a wide range of operating conditions even when feeding the cyclonic burner with undiluted air.The residence time of the streams inside the burner plays an important role for both reactive structure stabilization and combustion performances/emissions. Significantly, fuel-lean conditions correspond, in the considered cases, to simultaneously low CO and NOx emissions.Furthermore, it has been demonstrated that stable combustion can be sustained in absence of any preheating in a considerable thermal load range and that it is possible, in this condition, to achieve a complete fuel conversion, with a remarkably low pollutant emission for thermal loads up to 8 kW.

Numerical simulation and experimental study on pressure drop of radial jet cyclone

Abstract The grade efficiency of fine particles is relatively inefficient for conventional cyclones, but the grade efficiency of the Radial Jet Cyclone (RJC) exceeds 90% for particles larger than 4 μm. The pressure drop of this cyclone is discussed based on the continuity equation, and a theoretical model is used to predict the pressure drop over the cyclone. Experimental results is in good agreement with the calculation. The inner flow field of cyclone is simulated by Reynolds Stress Model (RSM), and it indicates that there is a larger tangential velocity compared with the Stairmand Cyclone (SC) under the same inlet velocity. It reveals that the local loss in cushion chamber is in a significant proportion to pressure drop.

Effects of Wall Roughness on the Flow Field and Vortex Length of Cyclone

Cyclone separators are widely used in gas solid separation process. Their dimensions and configurations have a great influence on the performance, and have been widely studied. However, for a long-time used cyclone, the surface roughness may increase due to erosion and solid collision, and also is an important factor regarding the cyclone performance. Unfortunately, the study of roughness has been ignored for a long time. In this paper, the effects of wall roughness on flow field of cyclone are investigated. The three-dimensional flow field is simulated with Reynolds Stress turbulence model using Fluent. The simulation results indicate that wall roughness has a great influence on flow field. The increased roughness leads to a decrease in vortex length, and this reduces the separation efficiency a lot. The tangential velocity also decreased along the axial position, but there is no obvious trend for the axial velocity. However, a lower pressure drop can be achieved when the wall roughness is increased. In conclusion, the increased wall roughness has its pros and cons, on one hand, it leads to lower pressure drop; on the other hand, the separation efficiency is also decreased. For a particular cyclone, there must be a compromise condition between pressure drop and separation efficiency, which is in coincidence with Pareto optimality, and will be studied further.