Cyclone Dust Research Articles

2735 円筒形サイクロン分離器内の旋回気流の Spin-Up Time と Spin-Down Time との関係

2735 円筒形サイクロン分離器内の旋回気流の Spin-Up Time と Spin-Down Time との関係

107 接線流入式軸流形サイクロン分離器内の定常流と脈動流状態における固体粒子の軌道解析(流体工学II)

107 接線流入式軸流形サイクロン分離器内の定常流と脈動流状態における固体粒子の軌道解析(流体工学II)

204 サイクロン分離器内の力学的釣合粒子の挙動に及ぼす脈動旋回気流の影響の数値解析(流体工学)

204 サイクロン分離器内の力学的釣合粒子の挙動に及ぼす脈動旋回気流の影響の数値解析(流体工学)

109 定常及び脈動状態における接線流入式軸流型サイクロン分離器の分離性能の評価(流体工学II)

109 定常及び脈動状態における接線流入式軸流型サイクロン分離器の分離性能の評価(流体工学II)

2736 固定案内羽根形式軸流型サイクロン分離器内の旋回気流の速度分布と角運動量分布に及ぼすボス直径の影響

An axial flow cyclone dust collector with fixed vanes is very simple construction and it is very easy to maintain and control. Therefore, it is used widely. Until now, the various constructure of cyclone is devised. In order to estimate the optimal collection efficiency, it is important to investigate the correlation between the constructions of the cyclone and the performances of collection Efficiency. Therefore, in this report, when the body diameter D_1 of the given cyclone and the imaginaly cylindrical length Hi as well as the angel of the fixed guide vanes as D_1=99mm, Hi=134mm and θ_B=45° was fixed, then the velocity distribution was measured by a cylindrical Pitot-tube with one hole on each boss diameter D_B=33,47 and 60mm. And then the correlation between the angular momentum flux in the vortex chamber and the Boss diameter D_B was discussed.

108 固定案内羽根形式軸流型サイクロン分離器内の気流の流動状態に及ぼすボス直径の影響(流体工学II)

108 固定案内羽根形式軸流型サイクロン分離器内の気流の流動状態に及ぼすボス直径の影響(流体工学II)

Estimation of collection efficiency depended on feed particle concentration for axial flow cyclone dust collector

A cyclone dust collector is applied in many industries. Especially the axial flow cyclone is the most simple construction and it keeps high reliability for maintenance. On the other hand, the collection efficiency of the cyclone depends not only on the inlet gas velocity but also on the feed particle concentration. The collection efficiency increases with increasing feed particle concentration. However until now the problem of how to estimate the collection efficiency depended on the feed particle concentration is remained except the investigation by Muschelknautz & Brunner[6]. Therefore in this paper one of the estimate method for the collection efficiency of the axial flow cyclones is proposed. The application to the geometrically similar type of cyclone of the body diameters D1=30, 50, 69 and 99 mm showed in good agreement with the experimental results of the collection efficiencies which were described in detail in the paper by Ogawa & Sugiyama[8].

Theoretical Investigations of Rotating Instabilities

AbstractThis paper collates recent theoretical work which sets out to model the characteristics of rotating instabilities often generated by industrial swirl generators such as swirl burners and cyclone dust separators. Results generated from three modelling approaches are discussed: a perturbation analysis about an axisymmetric viscous flow; a two‐dimensional variational approach of incompressible inviscid flow; and numerical solutions of the three‐dimensional Navier‐Stokes equations using contemporary turbulence models. Each modelling approach can predict some of the features of the complex flowfield associated with these rotating instabilities.

Experimental Analysis of Rotating Instabilities in Swirling and Cyclonic Flows

AbstractThis paper reviews the work carried out since 1990 in establishing the characteristics and properties of rotating instabilities found in swirling flows, such as those of cyclone dust separators and swirl burners. Considerable efforts have been made over the years in establishing the cause and use of these instabilities in swirling flows. The general conclusion indicates that there is potential benefit in its existence in combustion systems, but is detrimental within dust separation/classification systems. The analysis of these flows have included laser diagnostics (Laser Doppler anemometry, particle image velocimetry and flow visualisation), temperature mapping and numerical analysis. Many of the experimental measurements use a phase locking system based on cyclic pressures. The following paper reviews and updates the numerical modelling of the instability found in rotating flows.

Alternate Eddy Shedding Set Up by the Nonaxisymmetric Recirculation Zone at the Exhaust of a Cyclone Dust Separator

Two cyclone dust separators with geometric swirl numbers of 3.324 and 3.043 were used to analyze the motion of the complex three-dimensional time dependent motion set up in the free exhaust. A quantitative analysis of the flow was carried out, obtaining time dependent velocity measurements with the use of laser Doppler anemometry (L.D.A.) techniques. The investigations highlighted a eddy or vortex shedding mechanism in two distinct areas of the flow. This was in part caused by a reverse flow zone and a precessing vortex core within the exhaust region of the separator. Changes in the Reynolds number by a factor of 2 were observed to have no effect on the main characteristics of the flow. Some changes were seen in the flow structure with change in swirl number, particularly the size of the reverse flow zone and the position of the large engulfment vortices.

Computational and experimental investigations in a cyclone dust separator

Three-dimensional turbulent flow in a model cyclone has been simulated using PHOENICS code and experimental studies carried out using a laser Doppler anemometry (LDA) system. The experimental results were used to validate the computed velocity distributions based on the standard and a modified k-∊ model. The standard k-∊ model was found to be unsatisfactory for the prediction of the flow field inside the cyclone chamber. By considering the strong swirling flow and the streamlined curvature, a k-∊ model, modified to take account of the Richardson number, provided better velocity distributions and better agreement with the experimental results.

Mechanical Separation Process and Flow Patterns of Cyclone Dust Collectors

A cyclone dust collector (called herein a cyclone) is applied in many industrial fields, for example, powder technology, combustion chambers, various chemical plants, etc. Until now, there are many types of cyclones for the purpose of separation of solid particles; however generally-speaking, the following types of the cyclone are typical: returned flow or reversed flow type, axial flow type, and rotary flow cyclone with tangential injection of the second gas flow to the cyclone body. In order to understand the performance of the cyclone and the problems of turbulent rotational flow and the separation mechanism for solid particles, this review article describes the flow pattern and distribution of the tangential velocity for pure gas flow and for dust laden gas flow, which are most important factors for estimating the pressure drop and the separation characteristics of the solid particles, and also the mechanical separation process in the centrifugal flow field. This review article includes 162 references.

Estimation of the collection efficiency of the axial flow cyclone dust collector with the fixed guide vanes

In order to estimate the cut-size Xc and the mechanically balanced particles in the axial flow cyclone with the slit-separation method, the tangential velocity distributions were calculated by the finite difference method. In comparison of the calculated results of the total collection efficiency with the experimental results, the calculated results showed a little higher than the experimental results due to the re-entrainment of the collected particles by turbulence. The effect of the slit for promoting the collection efficiency was not recognized.

低レベル放射性試料の焼却実験システムの設置と燃焼実験

An incineration system was constructed which were composed of a combustion furnace (AP-150R), a cyclone dust collector, radioisotope trapping and measurement apparatus and a radioisotope storage room built in the first basement of the Radioisotope Center.Low level radioactive samples (LLRS) used for the combustion experiment were composed of combustible material or semi-combustible material containing 500 kBq of 99mTcO4 or 23.25 kBq of 131INa. The distribution of radioisotopes both in the inside and outside of combustion furnace were estimated. We measured radioactivity of a smoke duct gas in terminal exit of the exhaust port. In case of combustion of LLRS containing 99mTcO4 or 131INa, concentration of radioisotopes at the exhaust port showed less than legal concentration limit of these radioisotopes. In cases of combustion of LLRS containing 99mTcO4 or 131INa, decontamination factors of the incineration system were 120 and 1.1, respectively.

Modern design of aerocyclones

Unsolved problems in the field of hot gas cleaning led to a renewed interest in the performance of cyclone dust separators. Various calculation procedures exist for the calculation of cyclones. Most of these models need high calculation expenditure. For practical cyclone design a rough calculation of the separation efficiency and the energy consumption is often sufficient. This paper presents two possibilities to calculate the grade efficiency and the pressure drop. The first one is easy to handle but is based on simplified physical assumptions. The second one is a more complex calculation procedure which uses a detailed physical description of the flow field and considers turbulence, re-entrainment and the secondary flow. The results of the two calculation models are compared with experimentally obtained data for different gas temperatures.

The Use of Centre Bodies and De-Swirl Vanes in the Exhaust of Cyclone Dust Separators

This study arises from vibration problems that have been encountered in cyclones operated at high pressure. Work has shown that such vibrations can be triggered by the complex flow process and regular fluid dynamic periodicities that can occur especially in the exhaust nozzle. One such phenomenon is the precessing vortex core (PVC); this is where the central forced vortex region of the flow precesses about the central axis of the system.

Investigations into the Precessing Vortex Core Phenomenon in Cyclone Dust Separators

Experimental investigations have been carried out to examine the effect of downstream pipework configurations on the precessing vortex core (PVC) generated within the exhaust region of a cyclone dust separator. Characterization of the PVC using a non-dimensionalized frequency parameter (NDFP) was used to determine the relationship between Reynolds number and geometrical swirl number of the cyclone. The results show that the NDFP tends towards an asymptotic value for Reynolds numbers of about 50 000 and high swirl numbers (> 3.043). This value is reached earlier with lower swirl numbers. It was concluded that any exhaust pipework configuration produced a significant drop in the PVC frequency, and certain configurations either delayed or promoted the development of the PVC.

THEORY OF THE FRACTIONAL COLLECTION EFFICIENCY FOR THE AXIAL FLOW CYCLONE DUST COLLECTOR

ABSTRACT A cyclone dust collector is a simple device with no moving parts, so it is applied in many industrial fields. However there is still no satisfied theory to estimate the collection efficiency for a given cyclone with high reliability since it is very difficult to predict the movement of the fine solid particles in the three dimensional turbulent rotational flows in the cyclone. A new model of the fractional collection efficiency including the diffusion effect of the solid particles and the decay effect of the tangential velocity of gas flow along the concave wall surface has been derived. In order to confirm this model, a simplified axial flow cyclone of body diameter D1 = 99 mm has been constructed and fly-ash particles were used as a test dust. The experimental results of collection efficiency were compared those predicted by the Ogawa model and the Fuchs model.

Characterization of the PVC phenomena in the exhaust of a cyclone dust separator

A laboratory scale cyclone dust separator with swirl numbers varying from 3.043 to 1.790 was used to examine the effects of different downstream pipework configurations, flowrates and swirl numbers upon the size, shape, and position of the precessing vortex core. Also examined was the effect the precessing vortex core had on the reverse flow zone, and the relationship between the two.

Mueasurement of Flow Field in Cyclone Dust Collector with Internal Perforated Cylinder.

Measurements of tangential, radial, and vertical velocity components and pressure distribution in a cyclone dust collector which provides an internal perforated cylinder have been made. It is found that the tangential velocity in the cylindrical section is relatively large and almost the same as in a conventional cyclone without an internal perforated cylinder ; and the inward radial velocity is relatively small and constant at all vertical or circumferential positions between the outer and inner cylinders. It is also found that the static pressure distribution in the radial direction has a shape like a dish, and the pressure drop in the cyclone is considerably small. As a result, the dust collection efficiency was improved to 5%, and the pressure drop was decreased to about 30% compared with the conventional cyclone.