4Journal of Donghua University (Eng. Ed.) Vol. 20 No. 1 (2003)Testing and Analysis of the Speed of Water Jet in Water JetLoomsLI Ke-rang (李克讓)T5103 ADeparment of Silk Fashion, Anhui Ariculural Univrsiy, Hefei, 230036MA Wei-wei (麻偉巍)College of Science, Donghua Universiy , Shanghai, 200051CHEN Ming (陳明)College of Mechanical Enginering, Donghua Untversisy, Shanghai, 20051In the water jet looms, the distribution of the speedof water jet at the axis of the shed and its regularityregarded as the main standards which judge whether the waterare obtained by the Laser Doppler Tester. Based onjetis good or not. Among them the jet speed is the mostthe above, the water jet system is analyzed and theimportant. In this paper, the speed valuations of water jet aremain effective approaches to increase the fillingtested mainly by the Laser Doppler Tester.insertion rate and to widen the reed space of the loomare pointed out.Method of the TestingKeywords: Laser Doppler Tester, the speed of the waterjet, water jet looms.The displaying and the testing of jet flow are the two mainmethods usually adopted in the research of jet flowcharacteristics. The former includes hydrogen-bleb displaying,Introductionsmog displaying as well as muli-flashing photographtechnique , and so on. While the latter mainly includes the wireThe water jet loom, one of modem shuttleless looms, wasgauge flow jet speed tester and the Laser Doppler Tester, etc.innovated by a Cechboslovakian, V. Svaty in the fties of theFormnerly the testing of flow jet mostly adopted a pressuretwenty century.The basic idea of the water-jet weft insetion issensor tester and a high-speed photograph tester'. But as adrawing the end of the weft through a nozzle, through which aresult of adopting the pressure sensor tester, a T joint need tojet of water is pumped out in each loom cycle. The weft isbe insalled between the water pipe and the nozzle, and thethen entrained in the water jet and carried with it through theelastic deflection of this pressure sensor is slower than that oflhed. Water jet looms have characterstics of both a high weftinsertion rate and a low kinetic energy consumption. This isto be scaled. All these influence the accuracy of the testing.because of the high speed and a low mass of the weft insertionWhile a high-speed photograph tester only can shoot themedium(i.e, the jet of water) and smaller slppage of thelocation of the head of jet flow intermittently. The resultsweft relative to the jet water!. The commercially advantagetested by the above methods are all rough approximation. Irof water jet looms, ditinguished from other looms, is theirorder to obtain more exact data of the water jet speed, thehigh productivity and low specific floor space. Quite largeLaser Doppler Tester and the resistance strain gauge tester areinstallations of these looms are curently in operation all overadopted in this testing.the world. The real rotating speeds of water jet looms areWhen the speed of flow jet in water jet looms is analyzed,different for different fabric production and different rethe maximum of the speed of flow jet v at the axis at a certainspace, but they all run at the speed higher than 1000 r/min'2time t and at a certain displacement L from the nozzle exit isOf course, water jet looms are still required to raise their speedobtained as follows:higher in order to kee the superiority of speed to others. So it。=o(L, 1)is necessary to make an analysis of dynamics of the water jet inwater jet looms. To be the basic of optimized parameters ofIn view of the flight of weft yar only to be influenced bywater-jet system， their performance can be improved tothe speed of jet flow in the shed center line, so only the speedincrease the speed of weft insertion and then meet theof water jet in the certain line need to be tested while therequirement of the production. But as a rule this researchconcrete distribution of flow field in other location need not toshould be carried through from two aspects: the testing and thebe tested correspondingly.analysis of the speed of the water jet. In the research of water1 Laser Doppler Testerjet looms, the speed of water jet, the capability ofThe Laser Doppler Tester (LDT) is a new technologyconcentration of the jet beam and the distance from the nozzledeveloped in the sixties of the twenty century, it has many中國煤化工Received Nov. 7, 2001MHCNMHGJourna/ of Donghua University(Eng. Ed.) Vol. 20 No.1 (2003) 5advantages as follows'fo=fc-1。= sin(號)0o(a) Being a tester without touching, it does not disturbthe flow field;Herefo- the Doppler frequency of the sattering light;(b) It has a high spatial differentiation rate;fo- the frequency of scattering lIght received by the(c) Its dynamic response is fast and its testing precisionreceiver;is high;f.- the frequency of the laser beam;(d) The frequency of the output signal is in linearv一the speed of particle;proportion to the speed, and the frequency of the jet flow canλ一the wavelength of iradiating light;cover a very wide range of the speed of flow jet.a - the included angle of laser beams;On the basic of optic Doppler effect and with a laser beamβ一the included angle between the moving direction ofiradiating the moving particle with the speed field, LDT canparticle and the normal of the bisector of laserutilize the optic diference to test and get the Doppler frequencybeams.f。of the scattering light of the particle. Thereby LDT canPut the frequency signal into processor and calculate thecalculate the speed of the particle v(shown in Fig. 1).speed of the tested particle by a computer. The disposal oflight beam and the signal catching of the laser testing systemare shown in Fig.2.LDT has been applied in many fields; especially theTested particlekinetic study of the fluid dynamics shows its superiority. Totest the speed what we only need to do is to transmit the laserReceiverbeam to the testing-point. In the way the jet flow is not' Laser beamdisturbed. The spatial differentiation rate of LDT is very highFig. 1 The sketch of the speed testing by LDTNorzle一Pesse rglaing ciquceParticle generator一Hghressre gasLight dot displacement system←H Laser generaor一Electrical sourceTested locationPrinterFrequency generatorH Interface- ComputerGraph plotterFig.2 The skech of the sped testing by the rsisance strain gaugebecause the laser beam can be gathered to a very small testedresistance will be changed by the deflection of the armor platesubstance at a certain location. The typical differentiation ratedue to the jetting action， so the strain gauge and theofLDT is between 20 μm and 100 μn, which exceed otheroscilloscope can test the acting force F effectively( see Fig.3).means.One of the advantages of LDT is that the relation of the1 cm?frequency of output signal and the tested speed are linear, andits frequency tested can cover a very wide speed range of the10 mmjet flow from several mm.s-' to supersonics. We cancalculate the rectifying factor by the geometry relation of the|↑.70mmlight route. The signal of LDT is continuous in the flowage offluid as well as gas with scattering particles. And the responseFig.3 The sketch of the speed testing by the resistance strain gaugeof LDT has no lag esenially; it can get along with theAssuming the speed and the rate of flow of the waterpulsation of the onflow.2 The testing by a piece of resistancejet are v, q. Assuming the jet flow fies at a horizontal lineand under an atmospheric pressure. Assuming thestrain gaugemomentum modifying cofficient β = 1，the relationA pece of copper wafer with 1 cm' area and a piece ofbetween acting force F at the copper wafer and the speed varmor plate with 2. 5 mm thickness, 10 mm width and 70 mmcan be got asto:length are fixed together by two steel strips with 28 mm length.The resistance wire gauge is pasted on the armor plate. TF =pqucopper wafer is put at the centerine of the jet flow in中國煤化工(1)perpendicular to sustain its acting force. The value of theWhere.*YHCNMHG●m~':6Journal of Donghua University (Eng. Ed.) Vol. 20 No.1 (2003)1r-- the average sped of jet flow at the tested30-location, m●s";S- the urea of cupper wafer,I cm2.30}The curve of the force F with respect to the f1low speed v70can be obtained from lormula I (see Fig. 4). Thus the actingforce F. which has being tested. can calculate the averagespeed v.109030of. 60200400600800The excursion value of the light dot .x/mmFig.5 The curve of the speed of jet flow v with respeet to theexcursion value of the light dot與; 20Examination and Data ProcessingThe pessu endured by resistance picce F/cNBecause the jet flow is not steady the tested speeds areFig.4 The curve of the pressure endured byresistance pieccstraggling relatively. Thus the speed of jet flow in a certainwith respee 10) the speed to the flow jenlocation is evaluated by taking the average of reversal-tested'The resistance picce should be demarcated before itsspeeds，which inelude 20 groups (16 per group) of speeds thatapplication in order to get the force, which the ammor platehave been cllected in a definite period of time.sustatins al the (ested location, by the excursion value of theThe testing of speed adopts the water jet loom, whichlight dot of silloruph when we are testing the jet flow. Aftermanufactured by ShenYang Texile Machine Co.，with a No.having demarcated the resistuance picce . we obtain the relation1623 model nozzle manufactured by Nisan. The operationexpression of the force F with respect to the excursion value ofspeed of the loom is 900 r/min. Al the same location thelight dot λ as:testing is done by two means above. At a definite time theforce F acing upon the wafer is got by the offset of light dot ofF = 2. 548.Sx +0.4354the strain gauge x and the speed of flow jet v is obtained byWhere ---the force acted upon the wafer that the armorLDT. At dfferent distance along the jet axis the fluid speed vplate sustains, cN;is variable along with the time, and it has a peak value inx一the excursion value of the light dot ofphenomena. The tested data are shown in Fig 6 and ftted as aoscillograph. mm.curve by the least square method. Hereinto, the dots.So the formula 3 can be obtained from formula 1 andrepresent the tested data while the real line is ftted curve whichformula 2 as fllowing:is made by computer with MATLAB in polynomial form!71.巨5485x+0. 4354pSV25.485x+4.354(3)E60Thus the speed of fIow jet at a definite distance x from thenozzle also can he solved directly by formula 3 when we havehad the excursion value of light dot of oscillograph (see inFig. 5)In the interest of credibility, in this testing the testedresuls of the resistance strain gauge lesting was demarcated byThe expression 0f the fting curveLDT. The examination scheme is as follows:臺35- v= -0.0025 l.2 +0.071 3L+62 3799≌35Test the speed of jet flow at a certain location by LDT，and gct the excursion value of light dot of oscillograph at the500015same time as well as the speed tested with the resistance strainThe distance of the axis line from the nozzle cxit LIcmgauge lesting. Then the conversion relation of the speed tested中國煤化工ed ofjet fow in thewith the [Wo different 1means can be obtained.MHCNMHGJournal of Donghua University(Eng. Ed.) Vol. 20 No.1 (2003) 7We have the expression relation of the speed v withweft. If the relay technology of waterjet weft insertion can berespect to the distance from the nozzle exit L as formula 4:applied in practie we can not only raise the weft insetion rate。=-0.0025L2 +0.071 3L +62. 3799(4)of water jet looms grealy but also widen the reed space a lot.While L <30 cm v is nearly a const.This should be a main study aspect of the development of waterjet looms.Analysis and Discussion of the ResultsDiscussion of the resultsBecause the atomization of the jet flow has taken place at the1 Analysis of the resultsend of the shed, LDT is very difcult to aim at the centerine ofA conclusion can be drawn by the tested data and thethejet fow. Hence the speed of jet fow is tested by thefting curve of the speed shown in Fig 6 as follows:resistance strain gauge testing at the end of the shed. Of courseThe jet flow has a definite speed at the nozzle exit and itsthe esing has sorcomings as fllows,, which afer the accunecyspeed maintains in a small distance, and then the speedof the tested data. (a) The carateistis of rsitance will bedescends quickly. The speed of jet flow descends to aboutchanged when reistance is wet, this will make the accuney of38 m/s in the midd; and even smailer at the end of the sheddemarcating descended. So it has to be tested underwaterprooftrnvel and the available jet time of waler jet is limited. Thiscondition at first,(b) Because the distortion of shed armor takesgoes against raising the waler jet weft inserion rate more andplace continuously the force tested by the strain gauge has to havewidening the reed space.a snsitive response. (c) It is ieviable that the testing zero diftSo the fllowing several aspects should be taken intowillbe afeted. (d) The density of water drop is dfferent atacount lo retain the supeiority of water jet looms in weavingdifferent axis location so testing precision will be afected a lot.and to raise weft insertion rate more as well as to widen theTherefore, the test means of the speed of water jet shouldreed space a lot.be discussed in detail further.(1) To raise the speed of water jet looms more: Thespeed of water jet insertion will rise accordingly along with theConclusionelevation of the speed of jet flow; besides the available time ofwater jet weft insertion will be prolonged!",9l. So as to widenOn the basis of the speed variation of the water jet loomsthe reed space. But it is dfficul to raise the speed of water jetby Laser Doppler Testr, the dsribution of maximum speed oflooms more for a loom with2 m reed space and speed awater jet at the axis and its regularity are obtained. Based on1000 /min at present. The fllowing several problems need tothe above the water jet system is analyzed and it has pointedbe solved: improve the jeu system pertormance and elevate theout how we can increase the water jet speed more, prolong thewater pressure of the inner pump; aneliorate the perfornanceefiecivejet time as well as apply relay water jet weftof the pump and the norzle to improve the clleinserion, there are the main eftive approaches to increaseof the jet as well as increase the waler consumption of eachweft insertion rate and to widen the reed space of the loom. Atpick; improve the machine character of the runring bearing;the same time the main facos afctin the precision of estingimprove the adapability of the weaving raw material for highdata is also poined ou. The tst means of the sped of waterspeed of water jet looms, and so on.jet should be discussed in detail furtber.(2) Prolong the available jet time of weft insetion underthe condition hat the operation speed of water jet looms is notReferenceschanged. In the course of water jet insrtion the weft fieshrough the shed, crried by the jet fow of water. The speed[1] Wang Jinfu, Sun Yufang. Foreign WaterJet Looms. Texuileof weft insertionincreases at beginning and then descendsIndustry Prss, Beijing, 1998,1 -8 (in Chinese)slowly. While the speed of jet flow flls soon afer the drop[2] XiaoJiayu, Yam Xong Modem Ie Looms Werin. CinaJiar yu *Texile Univensiy Press, Shanghi, 1995, (1-15) (in ahinese)water fnies of the nozzle for the action of the air rsistance.[3] Yang Zhenhua. Teting and Analyis of Flow in Jet LoomsThus the weft is straight before the weft speed becomes equal(docoral thesis), China Textile University, Shanghai, 1996,the speed of water drop and so the bending of the weft can78 -94(in Chinese)be avoided to meet the need of the thnical requrement of[4] Wang Shikang, Sben Yan, Zhou Zuoyuan. The Techmologey ofweft insetion. In uhis period the water jet is beneficial to theLaser Dople Tsinghua University Pess, Bejing, 1985, 2-weft isertion, and this period of time is alled the available jet7,245 -278 (in Chinese)fime of weft inerion.Under the condition that the rotaing[5] Chen Ming. Modemcoms, China Texile University Pess,speed of wate jet looms is not changed, it can send the flyingShanghai, 1999, 56 -62 (in Chinese)weft fr-forth more to prolong the available jet time of weft[6] Zhang Yeying. Hydrodynamics, High Education Pess, 199180-190 (in Chinese)insertion, as well as to widen the reed space.(3) The water jeloms should be adopted the relay[7] Zhang Yihua. Masering MATLAB s, Tsinghua UniversityDean Bii 1005ρ-7 4s -27 _in Chinese)water-jet weft insertion. A relay water jet is reliable to be used[8中國煤化工，1974 65: 769-644by for wide looms; it is also suitable for the raw material of[9fYHCNMH.19.84701-6