STUDY OF AXIAL VELOCITY IN GAS CYCLONES BY 2D-PIV, 3D-PIY, AND SIMULATION

CHINA PARTICUOLOGY Vol 4. Nos 3-4. 204-210.2006STUDY OF AXIAL VELOCITY IN GAS CYCLONES BY 2D-PIV3D-PIV AND SIMULATIONZhengliang Liu, Jinyu Jiao and Ying ZhengDepartment of Chemical Engineering, University of New Brunswick15 Dineen Drive, P.O. Box 4400. Fredericton, NB. Canada E38 5A3. CanadaAuthor to whom correspondence should be addressed. Tel: 001-506-473329, E-mail: yzheng@unb.caAbstract The axial velocity distribution in a gas cyclone has been examined with two-dimensional particle imagevelocimetry(2D-PIV) and three-dimensional particle image velocimetry(3D-PIv) experiments in this study. due to theregistered in the axial velocity detected by 2D-PIV Efficient methods are proposed in this work to remove this contami-nation. The contamination-removed 2D-PIV data agree well with 3D-PIV results. The distributions of the axial velocity arealso computed by the Reynolds stress model(RSM)and verified using the PIv experimental results. Reasonableagreements are obtainedKeywords particle image velocimetry(PIV), numerical simulationelocity, cyclone separatorsIntroductionthis work, the axial velocity in a gas cyclone is studiedboth experimentally and numerically. Both two-dimensionalGas cyclones have been widely used as(2D)and three dimensional(3D )PIVs are used to measureseparators in the petrochemical and process itthe axial velocities. The contamination induced by thesince a centurury ago. The fiow pattems in gas cyclotangential velocity in the 2D-PIV measurements is re-of importance to their performance, and extensive research moved by mathematical methods. The contamina-has been caried out by experimental approaches and tion-removed results are compared with the experimentnumerical simulations. The experimental techniques for data obtained by 3D-PIV. The simulation results are veriobserving flow fields have been advanced from Pitot tubes fied using the experimental dataand hot-wire anemometers( HWA)to non-intrusive tech-niques such as laser Doppler anemometry(LDA)(Solero 2. Experimental Setup and MeasurementCoghe, 2002; Peng et al., 2002; Obermair et al. 2003; Huet al., 2005). However, all these aforementioned tech-Methodsniques have the common limitation that they make one- A schematic diagram of the experimental apparatus ispoint measurement for one test On the other hand, particle depicted in Fig. 1, where the cyclone was made of pleximage velocimetry(PIv) which can detect the whole-field glass. The detailed structure and dimensions(units in mmvelocity at the same time has been extensively used in of the cyclone are respectively shown in Fig. 2 and listed inrecent years( Stanislas et al., 2003; Liu et aL., 2005a).Table 1. Air stream was introduced to the cyclone tangenSince the flow field in an industrial cyclone was first tially through a scroll type inlet by a regenerative blowersimulated by Boysan et al. in 1982, numerical simulations (Gast R6150J-2)with a capacity of 365 m h-1.The inlethave attracted significant attention(HanjaliC, 1994; Meier& airflow rate being measured by a digital Pitot tube( KimoMori, 1999; Ma et al., 2000). In the field of modeling a con- AMI KS300)was controlled by a throttle valve and a byfined swirling flow, an important issue is how to accurately pass valve. the inlet air velocity ranged from 7.2 todescribe the turbulence behavior of the flow a number of 15.0.s", The pressure drop through the cyclone wasturbulence models are available, such as the standard k-e determined by a u-tube manometer. Detailed operatingmodel,the RNG. K-E model, and the Reynolds stress conditions are listed in Table 2. Tiny sugar particles(den-model(RSM)(Zhou, 1993). Hoekstra et al. (1999)evalu- sity: 1.58x10 kg m, refractive index: 1.54)of about 0.8ated the performance of these three turbulent closure microns in diameter were used as tracer particles, and theymodels with experimental results and reported that the were generated in a six-jet atomizer(TSI 9306A)by atom-RSM yields better prediction of the mean flow field in gascyclones. The RSM model involves the calculation of indi-izing a 5 wt% sugar solution. Experimental measurementsvidual Reynolds stresses using differential transport equa- tionswere performed across both0°-180°and90-270°sec中国煤化工 paration zonesnolds-averaged momentum equations. It has also been trace-nents First of all, theCN MHGy follow the centrifugaldocumented(Hu et al., 2005)that the results predicted by airflow. to determine the ability of tracer particles followingthe RSM model were in reasonable agreement with ex- the fluid and the speed at which the seed particles respondperimental dataLiu, Jiao& Zheng: Study of Axial Velocity in Gas Cyclones by 2D-P/V, 3D-P/, and Simulation1 Air filter, 2 Regenerative blower, 3 Bypass valve, 4 Throttle valve, 5 Atomizer, 6 Pitot tube, 7U-tube manometer, 8 Cyclone,9 Lightsheet optics, 10 Dual YAG laser, 11 Laser controller, 12 CCD cameras, 13 Synchronizer, 14 Computer systemFig. 1 Schematic diagram of the experimental apparatus and Piv systemto theusually introduced. It is defined asSttp/tgwhere tp is the characteristic time of tracer particles or180 velocity response time, and tg is the characteristic time ofthe vortex field4=2p+q2)d42136pd218(orp89direction from z-310 to-370 mm in the field of view. thelocus of zero axial velocity interface moves slightly inwardsDespite the magnitude of the velocity profiles decreasingproportionally, similar phenomena are observed when gasinlet velocity decrease-o-U=7.2ms(2D-PIV5 Conclusions0-U=150ms20PThe axial velocity of the gas flow in a gas cyclone isRadial tn o 4 60 7s measured by 2D-PIV and 3D-PIV. It is shown that the axialvelocity measured by 2D-piv can be distorted by the tarFig 7 Typical profiles of axial velocity at the axial position of gential velocity. This distortion is due to the intrinsicz-180 mm when Uin increases from 7.2 to 15.0 m-sweakness of 2D-PIV. This work proposed two methods toeliminate the contamination introduced by the tangentialvelocity. The corrected profiles of the axial velocity werecompared with those obtained by 3D-PIv, and goodagreements were obtained. The simulation results of theaxial velocity were verified by the experimental results. Itdemonstrated that the RSM is a good model, which canreasonably predict the axial velocity distribution in the gascyclone except the flow in the center of the cycloneAcknowledgementsThe authors gratefully acknowledge the financial assistancefrom AlF CFI and NSERc345 mm(3D-PIV)Nomenclatureinlet height, mmRadial position, r/mmclone inlet width. mimodel constant in Eq (6)345mmconical dust outlet diameter, mmvortex finder diameter. mmrticle diameter, mmcyclone cylindrical body height, mmcyclone conical body height, mm一·-370mclone inlet length,turbulent kinetic energy, ms"中国煤化工20Radial position, r/ mmCN MHGnsons of the contanvelocity (by 2D-PIV) with 3D-PIV experimental data and simu- tagential coordinate time, slation results in the conical body when Uh=150ms"inlet air velocity, ms-1210CHINA PARTICUOLOGY Vol. 4, Nos 3-4, 2006fluctuating velocity, mrsview of current status and future prospects. Int. J. Heat Fluidvvvzradial velocity, msFow,14,178-203tangential velocity, m-s"J.J.& van den Akker, H E. A (1999)axial velocity, mrsAn experimental and numerical study of turbulent swirling flow inverticalaxial coordinatescyclone cylindrical dust hopper height, mmgas cyclones. Che. Eng. Sci., 54, 2055-2065cyclone conical dust hopper height, mmHu, LY, Zhou, L.X., Zhang, J& Shi, M. X(2005). Studies oncyclone dust outlet height, mmstrongly swirling flows in the full space of volute cyclone sepa-Greek lettersrator. AIChE J, 51, 740-749Liu, Z.L., Zheng, Y, Jia, L. F.&Zhang, Q K(2005a). Study ofKronecker deltabubble induced flow structure using PIv. Chem. Eng. Sci., 60,dissipation of turbulent kinetic energy, ms3537-3552density, kg.mLiu, Z. L, Zheng, Y, Jia, L. F.& Zhang, Q. K.(2005b). An ex-fluid density, kg.mperimental method of examining the fiow structure in gas cy-clones by 2D-PIV. Chem. Eng J, Submittedstress tensor, kg. m.sMa, L, Ingham, D. B.& Wen, X(2000). Numerical modelling ofthe fluid and particle penetration through small sampling cyturbulence viscosityclones. J. Aerosol Sci, 31, 1097-1119model constant in Eq (13)Meier, H. F.& Mori, M. ( 1999). Anisotropic behavior of the Rey-characteristic timeholds stress in gas and gas-solid flows in cyclones. PowderSubscriptTechnol.,101,108-119Obermair, S, Woisetschlager, J& Staudinger, G(2003). Inves-lefttigation of the flow pattem in different dust outlet geometries of agas cyclone by laser Doppler anemometry. Powder Technol.138,239-251Peng, W,Hoffmann, A. C, Boot, P. J. A J, Udding, A, Dries, H.W. A, Ekker, A.&Kater, J (2002). Flow pattern in reverse-iowtrue values of the axial velntrifugal separators. Powder Technol., 127, 212-222axial positionsSolero, G& Coghe, A(2002). Experimental fluid dynamic char-acterization of a cyclone chamber. Exp. Therm Fluid Sci., 27,ReferencesBoysan, F, Ayers, w.H.& Swithenbank, J (1982). A fundamentalStanislas, M, Okamoto, M. Kahler, C. (2003 ). 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