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Short communicationDevelopment of a symmetrical spiral inlet to improvecyclone separator performanceBingtao Zhao*, Henggen Shen, Yanming KangDepartment of Environmental Engineering, Donghua University, No. 1882, Yanan Rd., Shanghai, Shanghai 200051, ChinaReceived 28 October 2003; received in revised form 24 February 2004; accepted 3 June 2004Available online 17 July 2004AbstractThree cyclone separators with different inlet geometry were designed, which include a conventional tangential single inlet (CTSI), adirect symmetrical spiral inlet (DSSI), and a converging symmetrical spiral inlet (CSSI). The effects of inlet type on cycloneperformance characteristics, including the collection efficiency and pressure drop, were investigated and compared as a function ofparticle size and flow rate in this paper. Experimental result indicated that the symmetrical spiral inlet (SSI), especially CSSI inletgeometry, has effect on significantly increasing collection efficiency with insignificantly increasing pressure drop. In addition, theresults of collection efficiency and pressure drop comparison between the experimental data and the theoretical model were alsoinvolved.Keywords: Cyclone; Symmetrical spiral inlet; Collection efficiency; Pressure drop1. IntroductionCyclone separators are widely used in the field of airpollution control and gassolid separation for aerosolsampling and industrial applications 1. Due to relativesimplicity to fabricate, low cost to operate, and well adapt-ability to extremely harsh conditions, cyclone separatorshave became one of most important particle removal devicethat preferably is utilized in both engineering and processoperation. However, the increasing emphasis on environ-ment protection and gassolid separation is indicating thatfiner and finer particles must be removed. To meet thischallenge, the improvement of cyclone geometry and per-formance is required rather than having to resort to alterna-tive units. Many researchers have contributed to largevolume of work on improving the cyclone performance,by introducing new inlet design and operation variables.These include studies of testing a cyclonic fractionator forsampling that used multiple inlet vanes by Wedding et al.2, developing a mathematic model to predict the collectionefficiency of small cylindrical multiport cyclone by DeOtte3, testing a multiple inlet cyclones based on Lapple typegeometry by Moore and Mcfarland 4, designing andtesting a respirable multiinlet cyclone sampler that minimizethe orientation bias by Gautam and Streenath 5, andcomparing the performance of a double inlet cyclone withclean air by Lim et al. 6. In this paper, the new inlet type,which is different type of inlet from that used by formerresearchers, was developed, and the experimental study onaddressing the effect of inlet type on cyclone performanceswas presented.2. ExperimentalThree kinds of cyclone separators with various inletgeometries, including conventional tangential single inlet(CTSI), direct symmetrical spiral inlet (DSSI), and converg-ing symmetrical spiral inlet (CSSI), were manufactured andstudied. The geometries and dimensions these cyclones arepresented in Fig. 1 and Table 1. To examine the effects ofinlet type, all other dimensions were designed to remain thesame but only the inlet geometry.* Corresponding author. Tel.: +86-21-62373718; fax: +86-21-62373482.E-mail address: (B. Zhao).Powder Technology 145 (2004) 4750The experimental system setup is shown in Fig. 2.The pressure drops were measured between two pressuretaps on the cyclone inlet and outlet tube by use of a digitalmicromanometer (SINAP, DP1000-IIIC). The collectionefficiency was calculated by the particle size distribution,by use of microparticle size analyzer (SPSI, LKY-2). Due tohaving the same symmetrical inlet in Model B or C, the flowrate of each inlet of multiple cyclone was equal to anotherand controlled by valve; two nozzle-type screw feeders wereused in same operating conditions to disperse the particleswith a concentration of 5.0 g/m3in inlet tube. The solidparticles used were talcum powder obeyed by log-normalsize distribution with skeletal density of 2700 kg/m3, massmean diameter of 5.97 Am, and geometric deviation of 2.08.The mean atmospheric pressure, ambient temperature, andrelative humidity during the tests were 99.93 kPa, 293 K,and less than 75%, respectively.3. Results and discussion3.1. Collection efficiencyFig. 3 shows the measured overall efficiencies of thecyclones as a function of flow rates or inlet velocities. It isusually expected that collection efficiency increase with theentrance velocity. However, the overall efficiency of thecyclone with symmetrical spiral inlet both Models B and Cwas always higher than the efficiency of the cyclone withconventional single inlet Model A at the same velocity; andespecially, the cyclone with CSSI, Model C has a highestoverall efficiency. These effects of improved inlet geometrycontribute to the increase in overall efficiency of the cycloneby 0.151.15% and 0.402.40% in the tested velocityrange.Fig. 4(a)(d) compares the grade collection efficiency ofthe cyclones with various inlet types at the flow rate of388.34, 519.80, 653.67, and 772.62 m3/h, with the inletvelocities of11.99, 16.04,20.18, and23.85m/s,respectively.As expected, the frictional efficiencies of all the cyclonesare seen to increase with increase in particle size. Theshapes of the grade collection efficiency curves of allmodels have a so-called S shape. The friction efficienciesof the DSSI (Model B) and CSSI cyclones (Model C) aregreater by 210% and 520% than that for the CTSIcyclone (Model A), respectively. This indicates that theinlet type or geometry to the cyclone plays an importantrole in the collection efficiency. It was expected thatparticles introduced to the cyclone with symmetrical spiralinlet (Models B and C) would easily be collected on thecyclone wall because they only have to move a shortdistance, and especially, the CSSI (Model C) changes theparticle concentration distribution and makes the particlepreseparated from the gas before entering the main body ofcyclone.Fig. 5 compares the experimental data at a flow rate of653.67 m3/h (inlet velocity of 20.18 m/s) with existingclassical theories 711. Apparently, the efficiency curvesbased on Mothes and Loffler model and Iozia and Leithsmethod match the experimental curves much closer thanother theories do. This result corresponds with the studycarried out by Dirgo and Leith 12 and Xiang et al. 13.Fig. 1. Schematic diagram of cyclones geometries: (a) conventionaltangential single inlet, Model A; (b) direct symmetrical spiral inlet, ModelB; (c) converging symmetrical spiral inlet, Model C.Table 1Dimensions of cyclones studied (unit: mm)DDehHBSab3001504501200112515015060Fig. 2. Schematic diagram of experimental system setup.Fig. 3. Overall efficiency of the cyclones at different inlet velocities.B. Zhao et al. / Powder Technology 145 (2004) 475048The comparison show that some model can predict atheoretical result that closed the experimental data, but thechanges of flow pattern and particle concentration distribu-tion induced by symmetrical spiral inlet having effects oncyclone performance were not taken into account adequatelyin developed theories.To examine the effects of the symmetrical spiral inlet oncyclone performance more clearly, Fig. 6 was prepared,depicting the 50% cut size for all models with varying theflow rate or inlet velocity. The 50% cut size of Models Cand B are lower than that of Model A at the same inletvelocity. As the inlet velocity is decreased, the 50% cut sizeis approximately decreased linearly. With inlet velocity20.18 m/s, for example, the decrease rate of 50% cut sizeis up to 9.88% for Model B and 24.62% for Model C. Thisindicated that the new inlet type can help to enhance thecyclone collection efficiency.3.2. Pressure dropThe pressure drop across cyclone is commonly expressedas a number gas inlet velocity heads DH named the pressureFig. 4. Grade efficiency of the cyclones at different inlet velocities. (a) Inlet velocity=11.99 m/s. (b) Inlet velocity=16.04 m/s. (c) Inlet velocity=20.18 m/s.(d) Inlet velocity=23.85 m/s.Fig. 5. Comparison of experimental grade efficiency with theories.Fig. 6. The 50% cut size of the cyclones.B. Zhao et al. / Powder Technology 145 (2004) 475049drop coefficient, which is the division of the pressure dropby inlet kinetic pressure qgmi2/2. The pressure drop coeffi-cient values for the three cyclones corresponding to differentinlet velocity are presented in Table 2.Obviously, higher pressure drop is associated with higherflow rate for a given cyclone. However, specifying a flowrate or inlet velocity, the difference of pressure drop coef-ficient between Models B, C, and A is less significant, andvaried between 5.21 and 5.76, with an average value 5.63,for Model B, 5.225.76, with an average value 5.67, forModel C, and 5.165.70, with an average value 5.55, forModel A, calculated by regression analysis. This is animportant point because it is possible to increase the cyclonecollection efficiency without increasing the pressure dropsignificantly.The experimental data of pressure drop were alsocompared with current theories 1420, and results arepresented in Table 3. The results show that the model ofAlexander and Barth provided the better fit to theexperimental data, although for some cyclones the modelsof Shepherd and Lapple and Dirgo predicted equallywell.4. ConclusionsA new kind of cyclone with symmetrical spiral inlet(SSI) including DSSI and CSSI was developed, and theeffects of these inlet types on cyclone performance weretested and compared. Experimental results show the overallefficiency the DSSI cyclone and CSSI is greater by 0.151.15% and 0.402.40% than that for CTSI cyclone, and thegrade efficiency is greater by 210% and 520%. Inaddition, the pressure drop coefficient is 5.63 for DSSIcyclone, 5.67 for CSSI, and 5.55 for CTSI cyclone. Despitethat the multiple inlet increases the complicity and the costof the cyclone separators, the cyclones with SSI, especiallyCSSI, can yield a better collection efficiency, obviously witha minor increase in pressure drop. This presents the possi-bility of obtaining a better performance cyclone by means ofimproving its inlet geometry design.References1 Y.F. Zhu, K.W. Lee, Experimental study on small cyclones operatingat high flowrates, Aerosol Sci. Technol. 30 (10) (1999) 13031315.2 J.B. Wedding, M.A. Weigand, T.A. Carney, A 10 Am cutpoint inlet forthe dichotomous sampler, Environ. Sci. Technol. 16 (1982) 602606.3 R.E. DeOtte, A model for the prediction of the collection efficiencycharacteristics of a small, cylindrical aerosol sampling cyclone, Aero-sol Sci. Technol. 12 (1990) 10551066.4 M.E. Moore, A.R. Mcfarland, Design methodology for multiple inletcyclones, Environ. Sci. Technol. 30 (1996) 271276.5 M. Gautam, A. Streenath, Performance of a respirable multi-inletcyclone sampler, J. Aerosol Sci. 28 (7) (1997) 12651281.6 K.S. Lim, S.B. Kwon, K.W. Lee, Characteristics of the collectionefficiency for a double inlet cyclone with clean air, J. Aerosol Sci.34 (2003) 10851095.7 D. Leith, W. Licht, The collection efficiency of cyclone type particlecollectors: a new theoretical approach, AIChE Symp. Ser. 68 (126)(1972) 196206.8 P.W. Dietz, Collection efficiency of cyclone separators, AIChE J. 27(6) (1981) 888892.9 H. Mothes, F. Loffler, Prediction of particle removal in cyclone sepa-rators, Int. Chem. Eng. 28 (2) (1988) 231240.10 D.L. Iozia, D. Leith, The logistic function and cyclone fractionalefficiency, Aerosol Sci. Technol. 12 (1990) 598606.11 R. Clift, M. Ghadiri, A.C. Hoffman, A critique of two models forcyclone performance, AI ChE J. 37 (1991) 285289.12 J. Dirgo, D. Leith, Cyclone collection efficiency: comparison of ex-perimental results with theoretical predictions, Aerosol Sci. Technol. 4(1985) 401415.13 R.B. Xiang, S.H. Park, K.W. Lee, Effects of dimension on cycloneperformance, J. Aerosol Sci. 32 (2001) 549561.14 C.B. Shepherd, C.E. Lapple, Flow pattern and pressure drop in cy-clone dust collectors: cyclone without inlet vane, Ind. Eng. Chem. 32(1940) 12461256.15 R.M. Alexander, Fundamentals of cyclone design and operation,Proc. Aust. Inst. Min. Met. (New Series) (1949) 152153, 202228.16 M.W. First, Cyclone dust collector design, Am. Soc. Mech. Eng. 49(A) (1949) 127132.17 C.J. Stairmand, Design and performance of cyclone separators, Trans.Inst. Chem. Eng. 29 (1951) 356383.18 W. Barth, Design and layout of the cyclone separator on the basis ofnew investigations, Brennst. Wa rme Kraft 8 (1956) 19.19 J. Casal, J.M. Martinez-Bennet, A batter way to calculate cyclonepressure drop, Chem. Eng. 90 (3) (1983) 99100.20 J. Dirgo, Relationship between cyclone dimensions and performance,Doctoral Thesis, Harvard University, USA, 1988.Table 2Pressure drop coefficient of the cyclonesCycloneInlet velocity (m/s)model11.9916.0420.1823.85averageA55.705.55B5.215.275.575.765.63C5.225.355.675.765.67Table 3Comparison of pressure drop coefficient with theoriesTheoryShepherdAlexanderFirstStairmandBarthCasalDirgoModel AModel BModel CValue6.405.626.185.015.187.854.855.555.635.67B. Zhao et al. / Powder Technology 145 (2004) 475050 外文翻译专 业 过程装备与控制工程 学生姓名 于 亮 亮 班 级 B装备032班 学 号 0310140146 指导教师 咸 斌 .旋风分离器对称蜗管进口的实验室研发Bingtao Zhao, Henggen Shen, Yanming Kang翻译：于亮亮摘要：设计三种具有不同几何形状进口的旋风分离器,一种是传统的单一切向进口(CTSI),一种是对称的直蜗管进口(DSSI),还有一种是对称的收敛蜗管进口(CSSI)。进口类型对旋风分离器工作特性的效果,包括收集效率和压降,本文研究并比较其与粒子大小和流速的关系。实验结果表明对称的蜗管进口(SSI),尤其是CSSI形状进口,随着新增的可忽略压降的条件下越来越多的对收集效率有重要的影响。另外,收集效率和压降的研究结果也包括试验数据和理论模型之间的比较。关键字:旋风分离器;对称的蜗管进口;收集效率;压降。介绍：旋风分离器广泛应用于空气污染控制领域，为含悬浮微粒气体进行气固分离等工业应用1。由于其制造简单,操作成本低,和对极端的苛刻条件的适应性好,因此无论是应用在工程上还是操作过程上旋风分离器成为最主要的除尘装置之一。然而,越来越多的提倡环境保护，气固分离都强调应该分离出最大量的微尘粒子。为达到这个要求,旋风分离器几何学和性能的改善要比替换可更换件来得重要。许多专家认为扩大旋风室是提高旋风分离器性能的主要因素,通过引进新设计的进口与操作变量。这包括对一台分离试样的旋风分离器的装有多个进口叶片的分馏器的测试并结合其他的研究2,德奥特建立一个数学模型来预算小型圆柱多谐振荡器旋风分离器的收集效率3,穆尔和麦克法伦以莱普勒的典型几何学为基准测试一个有多个进口的旋风分离器4,高塔姆和斯蒂纳斯设计和测试一个可换气的多进口旋风分离器取样器的最小方向偏差5,通过分离后的清洁空气来比较一个双进口旋风分离器的性能6。在本文中,介绍了一些形状研究员设计的不同形状进口的新式进口,和它们对旋风分离器的性能效果的实验性研究。试验性的研究三种具有不同几何形状进口的旋风分离器,包括传统的单一切向进口(CTSI),对称的直蜗管进口(DSSI),和对称的收敛蜗管进口(CSSI),已经研制出了。它们的几何形状和尺寸见Fig1和Table为了测试不同的进口类型所带来的效果,其它的尺寸设计完全相同,仅进口的几何形状不同。Fig.1 旋风分离器形状示意图：(a) Model A 传统的单一切向进口 (b) Model B 对称的收敛蜗管进口 (c) Model C 对称的收敛蜗管进口。. Table 1：旋风分离器尺寸统计：（单位mm）Fig.2：试验结构系统示意图图所示为实验系统机构。 压降是由接在旋风分离器进口和出口管的两压力计测量的。通过一数字微压计(SINAP ,压差1000-IIIC )读得。收集效率是通过微颗粒大小分析器(SPSI,LKY -2)所得粒度分布计算的。由于Model B,C具有一样对称的进口,所以组合式旋风分离器各进口的流速是相等的。并且流速可由阀来控制;运行条件也相同,将浓度为5.0g/m3的粒子用双喷管螺旋给料机喂到进口管中。固体颗粒为滑石粉核心密度的2700kg/m3,按原标准尺寸分配,平均直径的5.97Am,几何偏差为2.08。在这次测试过程中平均大气压,环境温度,和相对湿度分别是99.93kPa,293K,75%。结果和讨论3.1 收集效率图3显示所测量的旋风分离器总效率与流速或者进口速度的关系。正如预料的那样收集效率随进口速度的增加而增加。然而,Model B Model C两旋风分离器有着对称的蜗管进口,在同一进口速度下,两者的总效率永远要高于传统的单一切向进口旋风分离器(Model A)，特别是有CSSI的旋风分离器(Model C)的总效率最高。在测试给定的相同速度条件下,通过改善进口几何形状所带来的旋风分离器总效率的增加率分别为0.151.15%和0.402.40%。图4(a)(d) 比较不同进口类型的旋风分离器的分级收集效率。在进口速度分别为11.99,16.04,20.18,和23.85m/s时的流速分别为388.34,519.80,653.67,和772.62 m3/h。可见,旋风分离器的摩擦效率随粒子大小的增加而增加。所有旋风分离器的分级收集效率曲线都呈S形。DSSI(Model b)和CSSI(Model c)旋风分离器的摩擦效率分别比CTSI旋风分离器(Model a)大210%,520%。这表明进口的几何形状对旋风分离器的收集效率有着重要的影响。进入有对称的蜗管进口的旋风分离器(Model B和C)的粒子容易聚集在旋风分离器壁上,因为粒子只能移动很短的位移,尤其CSSI(Model C)改变了粒子分布浓度并使粒子在进入旋风分离器的筒体前就从气体中分离了出来.图5根据传统的理论711比较了流速为653.67m3/h(进口速度为20.18m/s)时的试验数据。很明显,以Mothes /Loffler模型Iozia/ Leith 理论得出的效率曲线比其它的学说所得的曲线更符合试验结果。这些结果与研究进行经过Dirgo、Leith 和Xiang 等人的研究结果相吻合。Fig.3 不同进口速度下旋风分离器的总效率比较表明有些模型可以推断一个还没有公开的理论结果。但是现有的试验数据理论还不足以推断出流态和粒子浓度分布的变化是对称的蜗管进口对旋风分离器性能产生的效果。为了更清楚地验证对称的蜗管进口对旋风分离器性能的作用效果,再看图6,表示随着流速或进口速度的变化引起的各个模型的50%切截尺寸。在相同进口速度下model c和model b的50%切截尺寸比model a要低。与进口速度的减少一样,50%切截尺寸也是近似呈线性减少的。例如，当进口速度为20.18m/s时,50%切截尺寸的减少率由model b的9.88%和model c的24.62%决定。这表明新型进口可以促进旋风分离器的收集效率。3.2.压降旋风分离器得压差数值通常表示为一定数量的气体入口速度压头高度差，用压差数值系数表示，压差数值系数是进口动压压差数值的分度。表2列出了在不同的入口速度时这三个旋风分离器的压差数值系数值。显然,旋风分离器的压降高低与流速高低有关。然而,一定流速或者入口速度下,A、B和C模式的压力降系数有所不同，在5.21和5.76之间变化，其平均值为5.63。例如模式B在5.225.76之间变化，平均值为5.67；模式C在5.165.70之间变化平均值为5.55；模式A根据回归分析计算。这是一个重点，因为由此有可能在没有有效的压差值增加的情况下提高气旋收集效率。表3列出了压降的试验数据与电流理论的比较结果。结果显示Alexander和Barth模式与试验数据最符合,尽管Shepherd ，Lapple 和Dirgo 气旋模式推算也很出色。Fig.4 不同进口速度时的选粉效率等级：(a)进口速度为11.99 m/s (b)进口速度为16.04 m/s (c) 进口速度为20.18 m/s (d) 进口速度为23.85 m/s.Fig.5 试验所得效率等级与理论的比较 Fig.6 旋风分离器的50%切截尺寸Table 2 ：旋风分离器的压力损失系数：Table 3 ：与理论压力损失系数比较：4、结论人们发明了一种具有对称的蜗管进口(SSI)，DSSI和CSSI的新型旋风分离器,并且测试和比较了这种进口类型的旋风分离器的性能。实验结果显示这种DSSI旋风分离器和CSSI旋风分离器的总效率分别比CTSI旋风分离器高出0.151.15%和0.402.40%。此外,DSSI旋风分离器、CSSI旋风分离器和CTSI旋风分离器的压力损失系数分别是5.63、5.67和5.55。尽管这些并联进口增加了旋风分离器的复杂程度并加大了其成本,然而具有SSI尤其是CSSI的旋风分离器具有更好的收集效率,而且显著的减少了压力损失。这篇文章介绍了借助于改进进气道几何形状设计而改善旋风分离器性能的可能性。 参考资料：1 Y.F. Zhu, K.W. Lee, Experimental study on small cyclones operating at high flow rates, Aerosol Sci. Technol. 30 (10) (1999) 1303 1315.2 J.B. Wedding, M.A.Weigand, T.A. Carney, A 10 Am cut point inlet for the dichotomous sampl Environ.Sci.Technol. 16 (1982) 602 606.3 R.E. DeOtte, A model for the prediction of the collection efficiency characteristics of a small, cylindrical aerosol sampling cyclone, Aerosol Sci. Technol. 12 (1990) 1055 1066.4 M.E. Moore, A.R. Mcfarland, Design methodology for multiple inlet cyclones, Environ. Sci. Technol. 30 (1996) 271276.5 M. Gautam, A. Streenath, Performance of a respirable multi-inlet cyclo