Vibration Characteristic Analysis of Axial Fan Shell Based on ANSYS Workbench

Transcription

1 Internatonal Conference on Logstcs Engneerng, Management and Computer Scence (LEMCS 2015) Vbraton Characterstc Analyss of Axal Fan Shell Based on ANSYS Workbench Lchun Gu College of Mechancal and Electrcal Engneerng Zhqun Guo College of Mechancal and Electrcal Engneerng Lchang Chen College of Mechancal and Electrcal Engneerng Abstract Axal fans wth the advantages of ts smple structure, large amount of wnd, wdely used n agrculture that respect, but agrcultural cross flow fan n the sze range of bg, prone to resonance problems. In ths paper, to a certan type of agrcultural ppelne fxed shaft flow fan shell as the research object, usng the ANSYS Workbench for the modal analyss. Analyss showed that: When the external exctaton frequency s wthn the range of 102Hz~161Hz and 354Hz~356Hz, the large deformaton dsplacement of the shell s n the drecton of the X and Y drecton; The analyss results provded theoretcal bass for the optmum desgn of the shell of the axal fan and the selecton of the drve motor. mport.prt fle format, but due to the software verson of the restrctons, not necessarly to be successful mport. IGS s a general format for CAD fle, whch s manly used for fle converson of dfferent 3D software system. It can effectvely avod the trouble that the model can't successfully mport[6]. Keywords-Axal Fan; ANSYS Workbench; Modal Analyss;Harmonc Response Analyss;Vbraton I. INTRODUCTION Axal flow fan s a fan of arflow and wnd vane n the same drecton due to ts smple structure and large volume n agrcultural ventlaton obtaned wdely applcaton[1-3]. Agrcultural cross flow fan n a larger sze of range, the fan s n operaton, blade and gas group resultng from the nteracton of nose and vbraton, the desgn needs to avod the natural frequency of the fan and prevents vbraton volume caused by wnd leaf sweep chamber, the damaged parts and hgh nose fault[4-5]. Ths paper uses ANSYS Workbench for the modal analyss and harmonc response analyss to a fxed ppelne type axal flow fan shell. II. SHELL MODEL The research object s a fxed ppelne type shaft flow fan shell and the nner dameter of the ppe s 825mm, ppe wall thckness s 4mm, fxed flange wdth of 20mm, ppelne length of 600mm, the establshment the parametrc model of the research object wth Creo based on the sze of the fan shell. After the completon of the model, the model fle s converted nto the.igs fle of the.prt format of the Creo format, and s mported nto the Workbench ANSYS, as shown n Fgure 1. Although Workbench ANSYS can III. Fgure 1. Fan shell model MATERIAL DEFINITION AND MESHING ANSYS Workbench provdes not only wdely used n engneerng materals and related parameters, but also allows users to create ther own materal type n the materal lbrary. If necessary, defne a name n the Workbench for QSTE420T materal, the elastc modulus of 200GPa, Posson's rato of 0.3, a densty of 7.85x103kg / m3. And the mpeller model defned for ths materal. The extent of the grd structure and densty drectly affects the accuracy of the calculaton, and the mesh coarseness ncreases wll ncrease the computng tme and storage space on your computer. Ideal for the analyss of the stuaton no longer change wth the coarseness of the mesh change, but cannot make up for the error fne mesh naccurate assumptons and nputs caused The authors - Publshed by Atlants Press 221

2 In ANSYS Workbench, the dvson method of the grd manly contans automatc meshng, tetrahedral mesh, hexahedral domnant meshng, sweep method[7]. Ths paper adopts automatc mesh grd method, and addng a number of parameters to control on the mpeller mesh, fnte element mesh model as shown n Fgure 2, a total of nodes, unts. Fgure 2. Fnte element mesh ANSYS Workbench provdes a powerful method of grd dvson and also provdes grd statstcs and qualty evaluaton methods, such as unt qualty, Jacoban rato, parallel devaton, devaton etc. Skewness s one of the man methods for grd qualty checkng. There are two algorthms, namely Skewness Normalzed and Equangular Skewness Equlateral-Volume-Based. The value s between 0 and 1, and the 0 represents the best, and the 1 represents the worst[7]. As shown n Fgure 3, n the Skewness assessment dagram, about 86% of the unt dstrbuton between , 90% of the unt dstrbuton between 0-0.5, ndcatng that the grd s good, accord wth the analyss requrements. Fgure 3. The assessment of mesh qualty 2 K { } 0 M (1) Where, [K] s the stffness matrx, mass matrx [M], are assumed to be constant. The mode s determned by the geometry of the structure, materal propertes and constrants. In ths paper, the load and restrant of the statc analyss are used, and the modal analyss of the mpeller s carred out, and the stress mode equatons are as follows: 2 K S { } 0 M (2) Wth the do not consder prestressed modal analyss compared to prestressed modal analyss consdered statc analyss results, consderng the elements and nodes of the prestressed, closer to the workng condton of the mpeller, makes the modal analyss results more accurate and and the modal shapes are reflected more real[8]. B. Appled Load Ppelne fxed axal fan casng at work are fxed through the flange, the paper wll be more practcally fx sxteen screw holes on the housng flange wth a fxed constrant. C. Modal Analyss Results Wth the ncreasng order, the error of the modal analyss results wll be larger. Based on need, usng Block lanczos method to extract only the frst sx mpeller modal analyss, the results are shown n Table 1 below: TABLE I. ANALYSIS OF THE RESULTS OF THE FIRST EIGHT MODES Mode Frequency[Hz] Max Fgure 4 and Fgure 5 are shell s one modal and second mode shapes cloud, and ther vbraton frequency s relatvely smlar, t should be a double root vbraton equaton, ths happens n modal analyss symmetrcal structure s normal. Ther shapes are also smlar, except that there s a phase dfference resonance. In both modal, the maxmum dsplacement occurs at the center poston of the shell. ANSYS Workbench s a default on the mass matrx normalzed modal, the numercal szes shown n the fgure are not real dsplacement szes, just a pont dsplacement rato [9]. IV. MODAL ANALYSIS A. Modal Analyss Prncples The modal analyss s a common method for studyng the dynamc characterstcs, vbraton analyss and dynamc optmzaton of mechancal structure. Mode s the nherent characterstc of mechancal structure, each structure has multple modes, each mode has a correspondng vbraton frequency w I and modal shape & Oslash; I, they can calculated by the followng equaton[8]: 222

3 Fgure 4. The frst mode cloud Fgure 7. The fourth mode cloud Fgure 8 and Fgure 9 are shell s ffth modal and sxth modal shapes cloud, they have the same vbraton frequency, t should be a double root vbraton equaton. Fgure 5. The Second Mode Cloud Fgure 6 shows the thrd mode cloud of the shell, the maxmum dsplacement occurs at the center of the housng, smaller housng wall deformaton. Fgure 8. The Ffth Mode Cloud Fgure 6. The Thrd Mode Cloud Fgure 7 shows the fourth mode cloud of the shell, smaller housng wall deformaton, the maxmum dsplacement occurs at the center of the housng. Fgure 9. The Sxth Mode Cloud Fgure 10 s the case of the seventh modal shape of the shell, the mddle part of the deformaton s small, deformaton occurs manly n the outer wall of the shell, and s concave and whte, and the entre outer wall to one sde of the shft. 223

4 Fgure 10. The seventh mode cloud Fgure 11 s the case of the eghth modal shape of the shell, the entre shell has a large dsplacement, where the largest dsplacement occurs n the mddle part of the. Fgure 11. The eghth mode cloud V. HARMONIC RESPONSE ANALYSIS In the modal type of cloud and ANSYS Workbench default s a mass matrx normalzed modal, as shown n the fgure, the numercal sze, and not the real dsplacement sze, just pont dsplacement rato. In order to get the vbraton characterstcs of the shell more accurately, the harmonc response of the shell s analyzed, and the relatonshp between the frequency and the dsplacement of the shell s obtaned. A. Harmonc response analyss prncple The harmonc response s analyzed by scannng n the frequency doman, and then the structure s analyzed under dfferent frequency and ampltude load, so the resonance s detected. The general mechancs equaton for the object s[10-11]: (3) Where, [M] s the mass matrx; s the acceleraton vector; [C] dampng matrx; velocty vector; [K]stffness matrx; {x} dsplacement vector. In harmonc response analyss, the force s a harmonc load, the harmonc load nto the formula (4): (4) B. Harmonc response analyss setup By the shell's modal analyss shows that the frst eght order mode of vbraton frequency scope of Hz~387.24Hz. Due to the hgh frequences of resonance structure wth smaller, so wthn the range, shell occurred serous vbraton of the possblty of a larger [9]. Based on the modal analyss results wll be harmonc response analyss to solve the frequency segment s set to 100Hz~300Hz, n order to get more accurate frequency and dsplacement relatonshp curve, frequency scannng nterval selecton s 2Hz. To solve the frequency range of 150 steps, ths paper calculates the harmonc response analyss. C. Slvng and post-processng The relatonshp between the frequency and dsplacement of at any node of the model s obtaned by solvng after, axal flow fan of stand-alone nstalled n the mddle poston of the shell, the mddle poston of the shell vbraton wll drect nfluence on the vbraton of the shaft of the motor, thereby affectng the vbraton of the fan blade, the mddle poston of the vbraton of axal flow fan s one of the greatest mpact. For accurate analyss of the ntermedate housng part of the vbraton characterstcs of selected at the mddle part of the node memory processng, obtaned the frequency of the node and the nodes along the X drecton dsplacement relatonshp curve, frequency and node along the Y drecton dsplacement relatonshp curve, frequency and node along the Z drecton dsplacement relatonshp curve. Poston of the node n the X drecton dsplacement manly affects motor blade n the X drecton, Fgure 12 for frequency and the frame along the X drecton dsplacement relatonshp curve, the curve by mult extremum, whch n the 102Hz~161Hz, 354Hz~356Hz range wll appear larger relatve dsplacement and the maxmum dsplacement value for 7.97mm. Fgure 12. The relatonshp curve between frequency and Dsplacement of nodes along the X drecton Due to the X axs and the Y axs are located wthn the blade plane, second only vbraton phase dfference of 90 degrees, so frequency nodes along the X drecton dsplacement relatonshp curves and frequency - node along the Y drecton dsplacement relatonshp curve s bascally the same. Poston of the node n the Z drecton dsplacement manly affects motor blade n the Z drecton, Fgure 13 for frequency and the frame along the Z drecton dsplacement relatonshp curve, the curve s more extreme, whch n the 356Hz~390Hz range wll appear larger 224

5 relatve dsplacement, but the maxmum dsplacement value for 1.44e-2mm. Fgure 13. The relatonshp curve between frequency and Dsplacement of nodes along the Z drecton Vbraton of the mddle poston of the shell nodes along the X drecton and the Y drecton wll drectly affect the wnd turbne blade n the shell space poston, f the ampltude of vbraton s too large wll lead drectly to the sweep chamber and other hazards; mddle poston of the shell nodes along the Z drecton of vbraton wll drectly affect the blade n the axal drecton of the shell, affect the normal work of the fan s not; from the harmonc response analyss results can be seen n the mddle poston of the shell along the X drecton and the Y drecton of dsplacement s larger, along the Z drecton of the dsplacement s small, n the selecton of fan drve motor, should avod to choose the exctaton frequency n 102Hz~161Hz, 354Hz~356Hz wthn the scope of motor. VI. CONCLUSIONS (1) The dsplacement of the mddle part of the fan housng s large, and the number of the renforcement plates can be ncreased and the stablty of the ntermedate part s ncreased. (2) When the external exctaton frequences are wthn 102Hz~161Hz, 354Hz~356Hz range, the shell part along the X drecton and the Y drecton wll appear larger dsplacement, so the choce of fan drve motor should avod the frequency range. REFERENCES [1] Tngwe Zeng. Axal fan desgn research and development of CAD software [D]. Zhejang Unversty, [2] Mngang Zhen. Fan of [D]. Tanjn Unversty performance smulaton of axal tunnel, [3] Langyu Ma,We Duan,Bng Wang. The general mathematcal performance model [J]. Thermal power engneerng of the axal flow fan, 2001,02: [4] Hayng Wu. Numercal study of the nfluence of desgn elements on the performance of axal fans [D]. Inner Mongola Unversty of Technology, 2014 [5] GuoLang Qn, Hengxn Lu, Lang Zhu. Agrcultural low-pressure axal flow fan development of automatc testng system [J]. General machnery, 2003,07: [6] [6]Yu Wang,Yonglong Ln,Lbo Zhou. Model data converson between Pro / E and Ansys software to study [J]. lftng transport machnery, 2013 (12): [7] Xnlong Dng,Gulong Lng. ANSYS Workbench 14.5 fnte element analyss case Xangje [M]. Tsnghua Unversty press, 2014: [8] Jcheng L,Ln Guo,Tanhu Zhang. Based on flud sold couplng combne cross flow fan mpeller dynamc characterstcs analyss [J]. Agrcultural Mechanzaton Research, 2015,09: [9] Yanpng L. Fnte element analyss and optmzaton of the centrfugal fan mpeller [D]. Northwest Agrculture and Forestry Unversty, [10] Shufeng Huang,Yunca Zhao. Analyss of column mode and harmonc response of vertcal powder mll [J]. mnng research and development, 2012,06: [11] Tao Lu,Wehu Wang,Fe Lu. Workbench based box arm modal and harmonc response analyss [J]. manufacturng automaton, 2015,04: