共查询到20条相似文献,搜索用时 0 毫秒
1.
2.
The cyclone separator is an important separation device. This paper presents a new type of embedded two-stage cyclone, which includes a 2nd-stage cyclone (internal traditional cyclone) with multiple inlets and a 1st-stage cyclone (outer cylinder) that unifies the 2nd-stage cyclone inlets into one inlet. The Taguchi experimental method was used to study the two-stage cyclone separator's inlet area on its performance. Studies have shown that the increase of the 1st-stage cyclone inlet area and the increase in the number of 2nd-stage cyclone inlets (N) positively affect reducing the pressure drop and a negative effect on efficiency. It is recommended to use 2S (the original 1st-stage cyclone inlet area) of the 1st-stage cyclone inlet area and 2N of the 2nd-stage cyclone inlets when separating fine particles. Compared with a traditional cyclone, the pressure drop is reduced by 1303 Pa, the mass separation efficiency (Eq) is increased by 0.56%, and the number separation efficiency (En) is increased by 2.05%. When separating larger particles, it is recommended to use 2S of the 1st-stage cyclone inlet area and 4N of the 2nd-stage cyclone inlets. Compared with a traditional cyclone, although En decreases slightly, the pressure drop is reduced by 3055 Pa, and the Eq is increased by 0.56%. The research results provide new insight into the design of the cyclone. 相似文献
3.
Three cyclone separators with different inlet geometry were designed, which include a conventional tangential single inlet (CTSI), a direct symmetrical spiral inlet (DSSI), and a converging symmetrical spiral inlet (CSSI). The effects of inlet type on cyclone performance characteristics, including the collection efficiency and pressure drop, were investigated and compared as a function of particle size and flow rate in this paper. Experimental result indicated that the symmetrical spiral inlet (SSI), especially CSSI inlet geometry, has effect on significantly increasing collection efficiency with insignificantly increasing pressure drop. In addition, the results of collection efficiency and pressure drop comparison between the experimental data and the theoretical model were also involved. 相似文献
4.
Theodoros Atmakidis Eugeny Y. Kenig 《Chemical engineering journal (Lausanne, Switzerland : 1996)》2009,155(1-2):404-410
In this work, the influence of the confining walls on pressure drop in packed beds is studied numerically for moderate tube/particle diameter ratios. Two different configuration types are investigated, a regular type and an irregular one. The regular configurations follow the atomic body-centered cubic and face-centered cubic structure in ideal crystals, whereas the modified ballistic deposition method is employed to generate the irregular configurations. To validate the simulation results, four experimental pressure drop correlations are used, namely by Ergun (1952) [1], by Carman (1937) [2], by Zhavoronkov et al. (1949) [3] and by Reichelt (1972) [4]. Simulation results for the regular configurations are in a good agreement with the Carman correlation. For the irregular configurations, which are closer to real packed beds, agreement with the correlations of Zhavoronkov et al. (1949) [3] and Reichelt (1972) [4] is better. This is explained by the fact that the latter two correlations take the wall effect into account. CFD simulations provide useful data on the flow field inside packed beds which can be used for the improvement and further optimization of the design and operation of packed bed reactors. 相似文献
5.
This study involved the analysis and characterization of the multiphase flow phenomenon inside the lower stage cyclone separator used in the clinker burning process. The analysis was performed using both CFD and experimental research methods. Very few studies are devoted to such types of cyclone separators, which in addition to their basic functions are also responsible for the technological process. Due to the atypical working conditions of these cyclone separators, they are characterized with a complex geometry, which significantly differs from that of the traditional separators.Furthermore, the evaluation of the accuracy and level of reliability of the two models of turbulence closure—k-e RNG and RSM(RANS), and the LES. The results obtained led to the conclusion that for the lower stage cyclone separators, the LES model proved to be the most accurate(both in the case of forecasting the separation efficiency and pressure drop). The performance parameter(in particular the separation efficiency) values obtained for the RSM model were also characterized by high accuracy. The k-e RNG model was characterized by significantly larger deviations. 相似文献
6.
7.
Younggeun Park Chang Yeon Yun Jongheop Yi Honggon Kim 《Korean Journal of Chemical Engineering》2005,22(5):697-704
In synthesizing COF2 from CO, a considerable amount of CO2 is produced. A method of solidifying CO2 at low temperature and separating CO2 particles from the COF2 gas using a cyclone was designed and the separation efficiency according to the cyclone feature was studied. Optimal sizing
and operation conditions of the cyclone were investigated by reviewing the flow velocity profile and the particle trajectory
using a numerical analysis with computational fluid dynamics (CFD). The effects of the inlet flow velocity and the ratio of
the cyclone diameter to the cone length (D/L) on the recovery efficiency were estimated. Results revealed that the separation
efficiency increases with an increase in the ratio of D/L and a decrease in the cyclone size. The recovery efficiency of CO2 increases with the increase in the inlet flow velocity. Based on these results, we could propose a concept and methodology
to design the optimal features and sizing of a cyclone suitable for separating solid CO2 from gaseous COF2 at low temperature. 相似文献
8.
In addition to collection efficiency, pressure drop is the most important characteristic of a filter medium. While there are numerous analytical expressions available for predicting the pressure drop of the filters made up of fibers with a unimodal fiber diameter distribution, there are not enough studies dedicated to filters composed of fibers with a bimodal (or multimodal) fiber diameter distribution. In this work, the pressure drop per unit thickness of filters made of bimodal fiber diameters is calculated by solving the Navier-Stokes equations in a series of 2-D geometries. These results are used to find the unimodal equivalent diameters of each bimodal filter that could be used in the existing expressions for calculating pressure drop. In agreement with the work of Brown and Thorpe [Brown, R.C., Thorpe, A., Glass-fiber filters with bimodal fiber size distributions. Powder Technology 118 (2001) 3-9.], it was found that the area-weighted averaging of the fiber diameters in a bimodal filter provides a relatively good estimation of its equivalent unimodal fiber diameter. We, however, noticed that in such an averaging the error percentage in the pressure drop prediction is sensitive to the fiber diameter ratios as well as the fraction of each fiber diameter in the bimodal filter. We, therefore, obtained a correction factor for the estimation of the unimodal equivalent diameters as a function of fiber diameter ratio and their number fractions. 相似文献
9.
力旋流器进口尺寸的设计是提高分离精度的一种有效方法。长期以来,对旋流器进口尺寸影响分离性能的认识主要来自工程实践经验,鲜见从旋转流场和分离机理的角度进行系统性分析的报道。采用计算流体力学方法进行旋转流场模拟,并考察进口尺寸缩小后的压力分布特性、三向速度分布和二次涡流结构。研究结果表明:进口尺寸缩小后切向速度数值的上升趋势明显,同时轴向速度和径向速度数值上相对变化较小,管内离心强度显著增高的同时保留了主要的分离结构。而且柱段流体,尤其是远离进口一侧的流体旋转更为充分,轴向速度双峰结构也更为明显。从上述角度来看,进口尺寸缩小后的流场分布情况更加有利于分离。但是,进口尺寸的缩小会加剧旋流管内的二次涡流运动,增大进口处射流的卷吸作用,使流场更加不稳定,从而对分离产生不利影响,因此分离粒度不可能随着进口尺寸的缩小无限制地降低。另外,进口尺寸缩小后,局部损失增大,且二次涡流运动加剧,导致旋流管的能耗会有一定的增加。 相似文献
10.
在旋风分离器的排气管处增加二次流,通过控制二次流的大小及进风方向达到改变旋风分离器内部流场分布,从而减少上灰环和短路流的产生,提高了对微细粉尘的分离能力。 相似文献
11.
Numerical and experimental study on the effect of solid particle sphericity on cyclone pressure drop
The continuous flow inside cyclone separator is usually simulated by solving the Reynolds averaged Navier–Stokes equations in Eulerian reference frame whereas the dispersed phase is modeled using Lagrangian approach. Although these methods have had a remarkable success, more advanced ideas are needed to model particulate phase in cyclones, especially the non-spherical shaped particles. Numerical simulation is verified with experimental results for the gas-solid flow in a cyclone separator. Reynolds Averaged Navier–Stokes equations (RANS) employing the RNG-based k–ε turbulence model are used to simulate the gas phase. 3-D particle tracking procedure is used for the solid phase. Three different equations for the drag coefficient are utilized in the numerical modeling to acquire more understanding of the behavior of non-spherical particles in cyclones. Computations resulted in the difference of pressure between the inlet and exit of the cyclone, and results are compared with experimental data. Experiments included measuring the separation efficiency of different shapes and sizes of particles. The results indicate that the CFD simulation can effectively reveal the pressure drop behavior as well as separation efficiency of gas-non-spherical particle flow in cyclone. 相似文献
12.
Studies on the performance of a hydrocyclone and modeling for flow characterization in presence and absence of air core 总被引:2,自引:0,他引:2
Hydrocyclones are getting more and more interest from various industries. They are widely used to separate particulates from liquid at high throughput because of their advantages like simple structure, low cost, large capacity and small volume, require little way of maintenance and support structure. Modeling of complex and multiphase flow behavior inside the hydrocyclone is done usually with the help of computational fluid dynamic study. Current study involves experimental investigation of separation performance characteristics of the hydrocyclone using new design parameters. For experimental purpose, a new hydrocyclone was designed with insertion of solid rod, at central portion of conical section of hydrocyclone, inside the hydrocyclone . By which air core could be eliminated effectively and hydrocyclone performance is improved. This effect may be observed due to reduction of radial and axial components of velocity and turbulence in the area near the entrance of the vortex finder. Therefore, the flow field characteristics inside the hydrocyclone with no air core become more suitable for separation. Also the effect of flow rate, vortex finder depths, air core and particle interaction were studied experimentally. A new arrangement was suggested to eliminate the air core formed inside the hydrocyclone. In this case, effect of diameter and height of solid rod inserted inside the hydrocyclone with changing total inlet flow rate was studied experimentally. Three-dimensional geometry and meshing of hydrocyclone is created in Gambit, preprocessor of commercial software—Fluent, for hydrodynamic study. 相似文献
13.
The flow characteristics and particle collection efficiencies of a long-cone cyclone with twice as long a conical section as that of the Stairmand cyclone were analyzed numerically to see the effect of the cylinder shape on the flow and collection performance. The three-dimensional flow field is obtained using the commercial package, FLUENT, and particle paths are calculated with the Lagrangean integration of the particle equation of motion. A number of turbulence models were tested, and it was confirmed that only the second-order Reynolds stress model gave reasonable results for the flow velocity profile.It is also shown that the shape of the core-annulus interface is important for the overall flow and collection characteristics, and the interface shape is in turn strongly affected by the distance from the bottom of the inlet to the cylinder-cone junction. By adjusting the diameters of the cylinder and the view finder with the mass flux and inlet area kept constant, the shape of the core-annulus interface could be changed. As a result, the short-circuiting of the inlet flow to the view finder and the total pressure drop could be reduced by properly adjusting the cylinder body diameter. 相似文献
14.
旋风流场的导流与整流 总被引:1,自引:0,他引:1
针对环流式旋风除尘器分离区内存在影响分离效率的涡流与非理想流动情况,提出在旋风除尘器内增设导流件以改进其性能,利用CFD大型流体模拟软件F luent6.2提供的雷诺应力模型(RSM)进行了数值模拟研究,优化了导流件结构,并进行了实验验证。模拟结果表明:增设导流件后,环流式旋风除尘器一次分离区内气流旋转更加规整,气流旋转圈数增加,流体的切向速度增大,有利于粉尘分离。实验结果证明:添加导流件后,除尘器分离效率由94%左右提高至96%左右,设备压降略有增加。 相似文献
15.
旋风反应器内压力降及分离效率的计算及测定 总被引:8,自引:2,他引:8
利用模型计算了旋风反应器的压力降及分级分离效率,并通过了实验验证。结果表明,模型计算结果与实验数据基本一致,可以作为旋风反应器设计的理论依据。 相似文献
16.
双循环旋风分离器采用筒锥结构,有2个切向进气口,即主进气口和回流口,分别位于筒体的中部和顶端。排灰口底部设有稳流锥,灰仓侧壁设置了抽气口。通过实验研究了进口位置、进口气速、稳流锥和抽气操作对此新设备分离性能的影响。实验设备直径为0.250 m,实验物料采用粒径0.1—36μm,平均粒径为8.72μm的石英砂。结果表明:主进口进料,风速在12—19 m/s变化时,总分离效率为98.5%—99.17%,可以基本去除大于3μm的颗粒。主进口进料比回流口进料总分离效率大1.5%—3.5%。采用主进气口进料时,稳流锥可以提高总分离效率0.15%—0.2%,抽气操作可以提高总分离效率0.3%—0.4%;回流口进料时,分别提高1.5%—2%和0.6%—1%。 相似文献
17.
In this paper, a newly designed distillation column consisting of a wetted wall with a rectangular cross section is analyzed and compared with a conventional packed column with regard to the operating range of both apparatuses. As expected, the pressure drop is considerably lower in the wetted-wall column and, therefore, it offers a higher range of operation. However, in the wetted-wall column, the separation efficiency decreases rapidly with increasing F factors. This effect can be overcome by the serial connection of two wetted-wall columns. 相似文献
18.
通过改变旋向和芯管直径,设计了3种差异旋风分离器,并按中心对称方式组成了3种并联方案:相同分离器、旋向差异分离器和芯管差异分离器并联。在冷态实验装置上,测量了单分离器和并联分离器的性能,并利用FLUENT软件分析了并联分离器的流场。结果表明,并联分离器的效率均高于单分离器,且效率-气速曲线未出现“驼峰”;与相同分离器并联相比,旋向交替变化时并联总压降较小,分离效率也更低,但各分离器流量分配均匀,未发现“窜流”现象;当芯管有差异时,并联总压降增大,各分离器进口流量分配不均匀,且进、出口流量平均相差6.0%,公共灰斗中存在“窜流”,旋流稳定性变差,效率降低。为了保证并联分离器的性能,应采用相同分离器对称并联的方式。 相似文献
19.
Bo Wang Binbin Pei He Liu Yunchao Jiang Delong Xu Yanxin Chen 《American Institute of Chemical Engineers》2017,63(10):4508-4518
The inner vortex plays a key role in the performance of cyclone separators. To explore the function and effect of the inner vortex in cyclone separators, a series of metal rods and metal blades are inserted in the typical Lapple cyclone separator to reduce the intensity of the inner vortex. First, the changes in general performance of cyclones are measured by experimental methods after insertion of the metal rods and metal blades. The flow field and particle motion are then simulated, respectively, by means of a Reynolds stress model (RSM) and a Lagrangian particle tracking (LPT) model. The results show that when the length of the metal blades is less than the boundary between the inner and outer vortexes, that is, the outer vortex remains unchanged and the inner vortex is destroyed partly, the separation efficiency remains constant and the pressure drop significantly decreases. When the length of the metal blades exceeds the boundary, the inner vortex is completely destroyed, and the outer vortex is significantly damaged, which results in sharp decrease of both the separation efficiency and pressure drop. The results indicate that the inner vortex has a notable effect on the pressure drop and virtually none on the separation efficiency. © 2017 American Institute of Chemical Engineers AIChE J, 63: 4508–4518, 2017 相似文献
20.
Jan Tobi? 《Chemical engineering science》2008,63(10):2670-2681
In this work, experimental investigations and computational simulations were combined into a hybrid method of complex phenomena modelling. In particular, the thermo-anemometric technique and the multi-scale methodology of modelling were applied to investigate air turbulent flow within a rectangular container filled with spheres in cubic arrangement and different baffles alternatively inserted between the spheres. The model systems formed the complex geometric structures where three length scales were distinguished. Hence, the local fluctuations of air velocity were examined in the micro-scale determined by the size of the anemometric probe. The interstitial flow distributions, in turn, were investigated in the cell scale related to the sphere diameter. At last, the pressure drop changes caused by the superficial flow distributions were analysed in the apparatus scale. In each case, the particular experimental data were approximated by numerical modelling. However, when the information exchange between the complementary models was arranged, the significance of the flow mechanisms dominating in particular length scales could be confirmed in relation to all the experimental data determined in this work. In recapitulation, it was indicated how experimental and numerical investigations can be effectively combined in searching for a “profitable” anisotropy of the packing resistance to flow. 相似文献