Comparison of Property Parameters of Pre-mixed Abrasive Water Jet

Transcription

1 Comparson of Proprty Paramtrs of Pr-mx Abrasv Watr Jt Nozzls by Smulaton Approach Jang Yuyng, Gong Lhang, Xu Xnln, Jang Runlan, Wang K Comparson of Proprty Paramtrs of Pr-mx Abrasv Watr Jt Nozzls by Smulaton Approach Jang Yuyng, Gong Lhang, 3 Xu Xnln, 4 Jang Runlan, 5 Wang K, Frst Author Engnrng Insttut of Fl Opratons, PLA Unv. of Sc. &Tch., Nanng, Chna,mgan98@63.com, Corrsponng Author Engnrng Insttut of Fl Opratons, PLA Unv. of Sc. & Tch., Nanng, Chna, GongLH006@63.com 3, 4, 5 Engnrng Insttut of Fl Opratons, PLA Unv. of Sc. & Tch., Nanng, Chna,x-ln-x@63.com,bstlan@63.com,cqq @qq.com Abstract Proprts of four tratonal pr-mx abrasv watr t nozzls wr compar by thory analyss an xprmntal approach n ths papr. Bas on th rsult, Sx typs of optmz nozzls wr sgn an smulat unr stay stat, turbulnt, two-phas flow contons by stanar -ε Equaton Mol an SIMPLE algorthm of prssur couplng. Two-phas flow ynamc prssur an vlocty of ffrnt nozzls wr gan. Aftr th comparson an analyss of th rsults, a nw combnatv way was gvn for th sgn of nozzl confguraton, whch may offr vncs for nozzls sgn.. Introucton Kywors: Pr-mx, Abrasv Watr Jt, Nozzl, Smulaton In th 970s, hgh prssur watr t tchnology ha wspra applcatons n many nustrs such as mnng, shpbulng, automotv an so on []. Ths applcatons rang from cuttng, rllng, mllng, to polshng ffrnt ns of matrals. Ab tn yars latr, abrasv watr t (AWJ) was nvnt to mprov th prformanc of th hgh prssur watr t qupmnts [-3]. Bas on th ffrnt mxtur mannr of abrasv an watr, AWJ was vlop nto two parts: th pr-mx AWJ an th rar-mx AWJ. Compar wth th rar-mx AWJ, th pr-mx AWJ has a numbr of stnct avantags, such as low worng prssur, hgh machnng ffcncy an grat cuttng capablty [][]. Howvr, th roson of th pr-mx AWJ nozzls has rstrct th vlopmnt of th tchnology. Thrfor, prolongng th lf of nozzls has grat sgnfcanc. Nozzl s a crucal componnt n th pr-mx AWJ qupmnt, t has grat nflunc on th usful lf of th qupmnt, th qualty of th abrasv watr t flow, th loss of nrgy an so on. Th man factors whch nflunt th proprts of nozzls nclu th matral an confguraton. Tang nto account th roson, usful lf an prc, mostly w choos SC, B 4 C, WC matral. Compar wth othr matrals, Y. H. Fng [] obtan that th lf of th SC nozzl s longr than WC nozzl. Howvr, SC matral s too brttl to us unr roson conton. B 4 C nozzl s a n of hgh war rsstanc matral, but t s ffcult to prouc, an wth xtrmly hgh cost. Th grant mols of nozzls wr sgn by L. L. Lu [3], whch ruc th war rat by changng th componnts of th nozzl matral along th nozzl axs. Through thortcal analyss, ths tchnology arrv at grat succssful. Howvr, t s xtrmly ntrcat n manufacturng procss. Snc th ntroucton of pr-mx AWJ machnng tchnology, many ns of nozzls, such as columnform nozzl, multpl nozzl, concal nozzl [], straght-con nozzl, paralll nozzl [5] hav bn sgn an us n th mllng, rllng, slottng procss. Howvr, n pr-mx AWJ cuttng procss, th nozzls mnton abov ar not always sutabl bcaus of th spcal ns of cuttng procss. In gnral, thr ar four typs of nozzl wly us n cuttng procss nclung columnform nozzl a, concal nozzl b an crcular arc nozzl c an, whch ar shown n Fg..Whr rprsnts t nput amtr, s pp amtr, L s th lngth of nozzl along th axs, l s columnform lngth, a s th tapr angl, r s raus of crcular arc. Intrnatonal Journal of Dgtal Contnt Tchnology an ts Applcatons(JDCTA) Volum7,Numbr5,March 03 o:0.456/cta.vol7.ssu

2 Comparson of Proprty Paramtrs of Pr-mx Abrasv Watr Jt Nozzls by Smulaton Approach Jang Yuyng, Gong Lhang, Xu Xnln, Jang Runlan, Wang K a b c Fgur. Four typcal confguratons of nozzls Concal nozzl s foun to b vabl bcaus of ts goo prformanc an asy machnng. Consquntly, othr thr typs of nozzls rcv lttl attnton, spcally to th crcular arc nozzl. Rsarch on concal nozzl has gan a funamntal nowlg of t flow ynamc charactrstcs such as th vlocty an prssur curvs, cuttng vlocty curvs through xprmntal stus. Howvr, ths wors ar complcat. Th paramtrs gan from ffrnt qupmnts hav prov to b qut napplcablty for othr qupmnts an othr contons. For crcular arc nozzls, whch ar ffculty to machn, xprmntal mtho s not vabl bcaus th hgh cost. To gan a comprhnsv unrstanng of th nozzl proprts an cuttng procss, CFD (Computatonal Flu Dynamcs) analyss s foun to b a goo approach bcaus rct vsualzaton of flu an partcl tractors whch ar qut ffcult for thortcal an xprmntal rsarch. Tang nto account prolongng th usful lf an nhancng th cuttng prformanc of nozzl, ths papr sgn sx typs of pr-mx AWJ cuttng nozzls. Aftr compar th proprts of ths nozzls through thortcal, xprmntal an smulaton mtho, th bst paramtrs wr gan.. Thortcal analyss an comparson In pr-mx AWJ cuttng procss, thr ar two typs of nrgy loss nclung loss along th way an local loss. In gnral, th loss along th way s nglgbl bcaus th lngths of nozzls ar vry short. Th man part s local loss [6][7]. For ffrnt typs of nozzls, th loss s ffrnt. For xampl, whn two-phas flow passs through th short thn columnform nozzl a, local loss s prouc. Bas on Brnoull quaton, p u + rg g p u = + + h rg g m () r Q u - u ) = p A - p A + p ( A - ) () ( A Whr p s nlt prssur, p s lt prssur, u rprsnts nlt man vlocty, u rprsnts lt man vlocty. h s local loss of nozzl. r s two-phas flow constant nsty, Q m rprsnts flow rat. A s pp cross-sctonal ara, A s nozzl cross-sctonal ara. ( - u ) h p - p u u rq u u u = + - = + - m rg g g A rg g g (3) Q = Au = (4) A u Wly us mprcal formula s, u h m = K (5) g 936

3 Comparson of Proprty Paramtrs of Pr-mx Abrasv Watr Jt Nozzls by Smulaton Approach Jang Yuyng, Gong Lhang, Xu Xnln, Jang Runlan, Wang K æ ö K 0.4ç - (6) = ç è ø Whr K rprsnts local loss coffcnt, a mnsonlss varabl. u s man vlocty. It can b notc that whn th valu of K ncrass, th valu of h ncrass too. s columnform m nozzl amtr, s pp amtr. Th rlatonshp btwn local loss coffcnt K an s shown n Fg.. [5]. It s obvous from Fg.3. that th crcular nozzl nlt local loss coffcnt K crass as th r ncrass, whch s ffrnt from columnform nozzl a. Th varaton of Local loss coffcnt K of concal nozzl b s almost th sam as that of crcular arc nozzl c [5]. K K / Fgur. Local coffcnt K for ffrnt / r/ Fgur 3. Local coffcnt K for ffrnt r/ As mnton abov, t can b notc that a corrsponng fn that mas th local loss lowr than of concal nozzl b. 3. Exprmntal analyss an comparson r valu of crcular arc nozzl c can b Unr th sam xprmntal conton, coffcnt of nozzls wth th sam nlt an lt amtr ar gvn n Tabl.. [] typ Tabl.Coffcnt of nozzls Rsstanc coffcntx Constrcton coffcnt Vlocty coffcnt Flow rat coffcnt m columnform nozzl a concal nozzl b(a = 3-4) crcular arc nozzl c Tabl.. shows th coffcnt of columnform nozzl a, concal nozzl b an crcular arc nozzl c. It ncats that th crcular arc nozzl c wth th lowst rsstanc an hghst vlocty ncrasng rat strng contrasts wth th othr two nozzls. Concal nozzl b hav much bttr prformanc than that of columnform nozzl a. J. J. Sun [8] vrf th rsult through conuctng a srals of xprmnts. Bss xprmnt, H. L. Wang [] gan th sam rsult through CFD analyss. Th ynamc charactrstcs paramtrs of stay stat, turbulnt flow n th nozzl ar mostly gvn by xprmntal ata or mprcal formula. Th concal nozzl has rcv lttl attnton. Unr th sam xprmntal conton, as wll as th sam nlt an lt amtr, compar wth concal nozzl b, t flow prssur of crcular arc nozzl ncrass mor raply along th axs n th ownstram rgon [8].Thrfor, t s ncssary to gan an nsght of charactrstcs of nozzl through CFD mtho. 4. Establshmnt of smulaton mol As mnton abov, th concal nozzl an th crcular arc nozzl hav low nrgy loss by thortcal analyss. Th lt prssur of crcular nozzl s hghr than that of concal nozzl by 937

4 Comparson of Proprty Paramtrs of Pr-mx Abrasv Watr Jt Nozzls by Smulaton Approach Jang Yuyng, Gong Lhang, Xu Xnln, Jang Runlan, Wang K xprmntal analyss. Howvr, a furthr rsarch on masurmnt of paramtrs an vsualzaton of flow tractory ar stll vry ffcult by thortcal an xprmntal approach. For ths purpos, sx ns of nozzl ar sgn for smulaton stuy bas on th four typcal pr-mx AWJ nozzls as mnton abov. Th rsults from CFD stuy ar thn analyz to gan an nsght nto th t flow charactrstcs an nozzls prformanc n cuttng procss. 4.. Mol confguraton Th cross-sctonal of sx nozzls ar shown n Fg.4. Intally, th two-phas (watr an partcl) s assum as contnuous mum, whch has contnuous vlocty an prssur strbuton. Thr ar only watr an abrasv partcls xst n th flow fl. Th two-phas flow s ncomprssbl. Th abrasv partcls ar assum to b smooth sphrcal wth unform sz. Thr s no hat transportaton. 4.. Govrnng quaton Th contnuty quaton [4] for th volum fracton of qth phas an th momntum quaton [4] ar gvn blow. ( a ) ( a u ) q t + q = 0 (7) ( ru ) P æ u u ö ru u mç + = (- ru ) ' u ' t ç è ø (8) Whr a s q th phas volum fracton, u s th vlocty n x q rprsnts tm. x an x ar coornat rcton, P s prssur, r s constant nsty, m s ynamc vscosty. ' ' uu coornat rcton, t s th Rynols strss, a b c f Fgur 4. Confguratons of nozzls Th flu turbulnt stanar quaton ar gvn by - quaton [] s us n ths smulaton wor. Th mathmatcal 938

5 Comparson of Proprty Paramtrs of Pr-mx Abrasv Watr Jt Nozzls by Smulaton Approach Jang Yuyng, Gong Lhang, Xu Xnln, Jang Runlan, Wang K ( r) t + ru éæ m ö ù t = ê ú + G + G - -Y b M x ç m + r x êë è s ø úû (9) ( r ) t + ru = éæ m ö ù t ê ç m + ú + C êë s è ø úû ( G + C G ) 3 b - rc (0) Whr u s vlocty n th nrgy u to th man vlocty grants, x coornat rcton, G s th gnraton of turbulnt ntc G s th gnraton of turbulnt ntc nrgy u to th b buoyancy, Y s th nflunc of comprssbl turbulnt pulsaton xpanson to sspaton rat, M m = rc s turbulnt vscosty. C =. 44, C =. 9, C = 0. 09, s =. 0, s =. 3 ar t m 3 th turbulnt Prantl numbrs for turbulnt ntc nrgy an sspaton rat []. To nvstgat th mol convrgnc crtron that traton rsu of th flow must blow 0.00, computatons wr prform usng fnt volum mtho scrtsaton approach an SIMPLE algorthm on gr Bounary contons Th nozzl s assum to b axsymmtrcal, an th uppr half was solv. Th nlt vlocty 3/ u p u = m / s, = 0.u, =, = 0, =0, p 0.05 = p rf = 0, = 0, n n n n = Plottng gr 5. Rsult an scusson Fgur 5. Plottng gr of nozzls A st of smulaton wth ffrnt confguratons hav bn carr. Th CFD rsults for th two-phas flow ynamc prssur an vlocty strbuton of nozzls ar shown n Fg.6.an Fg.7. Th blu rgon rprsnts th low ynamc prssur or low vlocty, whl th ynamc prssur or vlocty pas at th r rgon. 5.. Dynamc prssur an vlocty varaton Fg.6 an Fg.8 show th varaton of axal nozzl ynamc prssur unr th sam nlt prssur an vlocty. Th curvs n Fg.8 ncat that thr s ntal rap ncrasng n th ntranc of th nozzl wth th axal stanc of approxmatly mm.ths rsult may b caus by ynamc prssur grant actng on th contracton rgon. Snc a slght slow ncrasng xsts n th rgon of ab mm to 0mm, th ynamc prssur pas at ab 0mm.Whn th flow lavs th r rm of th nozzl, t ntrs th atmosphr as a fr t wth raply cay ynamc prssur. 939

6 Comparson of Proprty Paramtrs of Pr-mx Abrasv Watr Jt Nozzls by Smulaton Approach Jang Yuyng, Gong Lhang, Xu Xnln, Jang Runlan, Wang K a b c Fgur 6. Dynamc prssur (MPa) strbuton of nozzls a, b, c,, a b c Fgur 7. Vlocty (m/s) strbuton of nozzls a, b, c,, Dynamc prssur(mpa) a b c vlocty(m/s) a b c Axal poston(m) Fgur 8. Comparson of axal ynamc prssur (MPa) Axal poston(m) Fgur 9. Comparson of axal vlocty (m/s) Fg.7 an Fg.9 shows th two-phas flow vlocty varaton along nozzl axs. Th vlocty clos to th nlt ncrass raply that caus by contracton rgon. At ab mm, th vlocty approachs an almost balanc valu, thus th vlocty along th axs ncrass slowly. Whn th flow lavs th r rm of th nozzl an ntrs nto th atmosphr as a fr t, th raply cay vlocty s n 940

7 Comparson of Proprty Paramtrs of Pr-mx Abrasv Watr Jt Nozzls by Smulaton Approach Jang Yuyng, Gong Lhang, Xu Xnln, Jang Runlan, Wang K th smlar way to th ynamc prssur. Th nozzls a, b an c ncras mor raply than th nozzls an n th nlt rgon, but cay mor raply n th lt rgon. What s mor, an obvous turbulnc xsts at th bottom of t flow. Th rsults mnton abov ncats that n th nlt rgon, th ynamc prssur an vlocty of crcular arc nozzl b ncras th most raply u to th spcal crcular arc confguraton. Th nlt confguraton paramtr whch nfluncs th t flow acclraton an cuttng proprty s vry mportant for nozzl sgnng. A smallr nlt ara n th ntal rgon of nozzl wll ncras acclraton ffcncy bcaus both th flow ynamc prssur an vlocty ar gratr than that of largr ara. In th ml straght rgon of ab mm to 0mm, t s obsrv that th ynamc prssur changs towars a slow ncrasng typ whl th vlocty rmans roughly unchang. For crcular arc nozzl c, th bhavors of th flow changs towars anothr mor gratr valu that las to ynamc prssur an vlocty ncrasng n lt t flow rgon. Ths rsult s probably u to th fact that th lowr local nrgy loss n th nlt rgon. Howvr, th rsng of th ynamc prssur an vlocty n th r rm may la to matral roson. Whn th flow lavs th r rm of th nozzl an ntrs nto th atmosphr as a fr t, nozzl an hav a stnct long t stram cor rgon n whch th ynamc prssur an vlocty ar almost unchang. Although th axal stanc n ths rgon s vry short, t has grat nflunc on cuttng proprty. Th longr axal stanc wll ncras th cuttng ffcncy bcaus of th sustan mpact actng on wors. 5.. Effct of th rato of l an Jt flow wth pa lt vlocty was obtan unr th contons of th nlt prssur of 40MPa, th lt amtr of 0.8mm, l / = 3 [][8] an th nlt prssur of 60MPa,lt amtr of mm, l / = - 4 [8].From th xprmntal ata, t can b monstrat that l / s an mportant paramtr whch has nflunc on th lt pa vlocty. Gnrally, l / = 3 s consr to b th optmal valu. Fg.0 an Fg. show th ynamc prssur an vlocty valus rspctvly vrsus th axal stanc for ffrnt l / of 3 an 3.3 by CFD stuy. Dynamc prssur(mpa) a f vlocty(m/s) a f Axal poston(m) Axal poston(m) Fgur0. Comparson of axal ynamc prssur (MPa) Fgur. Comparson of axal vlocty (m/s) Unr th ntal conton of nlt prssur of 30MPa, lt amtr of 0.6mm, th valus of ynamc prssur an vlocty of nozzl f ar gratr than that of nozzl a. Obvously, th voluton of two-phas flow ynamc prssur an vlocty profl s not fully vlop at th lt of nozzl f. In fact, th valus ar much lowr than of nozzl a. For th valu of l / abov 3.3 at nlt prssur of 30MPa, th flow s clos to an unchang stat by CFD stuy. Thrfor, thr xts th optmal valu of l / that rangs from 6.7 to Concluson In ths papr, crcular arc nozzls wr consr to b th bst choc bcaus of th goo prformanc n cuttng procss by thortcal argumnt an xprmntal contrast. Sx typs of nozzls 94

8 Comparson of Proprty Paramtrs of Pr-mx Abrasv Watr Jt Nozzls by Smulaton Approach Jang Yuyng, Gong Lhang, Xu Xnln, Jang Runlan, Wang K wr sgn an smulat bas on th concluson. Th smulaton rsults ar conc wth thortcal arthmtc an xprmnt ata. Th analyss of fnngs l to th followng conclusons.. Compar wth othr nozzls, mor rap ncrasng xts n th nlt rgon of crcular nozzl b.. For crcular nozzl c, th pa ynamc prssur an vlocty wr gan n th r rm of th nozzl. Whl th nrgy loss n th r las to rap vlocty cayng, as wll as a short flow cor lngth an nozzl roson. 3. Th nlt vlocty of nozzls an ncras slowly an th flow wr not stay, whl th lt t stram cor s longr than that of othrs. 4. Svral paramtrs such as t flow prssur, vlocty an lt amtr shoul b too nto account whn choosng th valu of l /. 5. Through optmzng th confguraton of nozzl b an c, vlopng th strong ponts of nozzl b for ts rap ncrasng nlt ynamc prssur an vlocty, mang th bst us of th avantag of nozzl c for ts pa valus n th r rm of th nozzl, an avong th wa ponts of th two nozzls ar foun to b a goo way to ncras th two-phas flow cuttng ffcncy. 7. Rfrncs [] Shngxong Xu, Hgh Prssur Watr t Tchnology & Engnrng, Hf Unvrsty of Tchnology Prss, Chna, 006. [] Honglun Wang, Numrcal Smulaton of pr-mx Abrasv Hgh Prssur Watr Jt Cuttng Nozzl, Journal of PLA Unvrsty of Scnc an Tchnology, vol.8, no.4, pp , 007. [3] Yaun L, Hongtao Zhng, Ln Ca, Numrcal Rsarch on Prformanc of Swrlng Flow Combustor, JCIT: Journal of Convrgnc Informaton Tchnology, vol.7, no.9, pp.5-4, 0. [4] Wn Lu, Guoun Zhang, Kay Yu, WnZhng Ma, WW Mo, Optmzaton of Thxomolng Procss for Smsol AM50 Magnsum Alloy by Numrcal Smulaton, AISS: Avancs n Informaton Scncs an Srvc Scncs, vol.4, no.0, pp.303-3, 0. [5] Zurong Dng, Hyroynamcs, Hghr Eucaton Prss, Chna, 003. [6] Langmn Hu, Hyroynamcs, Wuhan Unvrsty of Tchnology Prss, Chna, 007. [7] Xanlang Xu, Chuanl Wang, Jun Zhang, Hyroynamcs, Natonal Dfns Inustry Prss, Chna, 006. [8] Jaun Sun, Watrt Cuttng Tchnology, Chna Unvrsty of Mnng &Tchnology Prss, Chna, 99. [9] Xng Dong, Anong Ma, Dongmng L, Numrcal Smulaton Stuy of th Nozzl Ins-flow of Prmx Abrasv Watr Jt, Machn Dsgn an Rsarch,vol.,no.6, pp.87-90,005. [0] WnChang Tsa, PngChng Yu, Dsgn of th Elctrcal Drv for th Hgh-Prssur GDI Inctor n a 500cc Motorb Engn, IJEI: Intrnatonal Journal of Engnrng an Inustrs, vol., no., pp.70-83, 0. [] Jang Fan, Huang Png, Flunt Avanc Applcaton an Exampl Analyss, Tsnghua Unvrsty Prss, Chna, 008. [] Yhua Fng, War Bhavors of th Cramc Nozzls n San Blastng Tratmnt, Journal of th Europan Cramc Socty, vol.3, no., pp.33-39, 003. [3] Ll Lu, Janxn Dng, Jun Zhao, Mngw Dng, Rsarch for th Rsst Ways of Nozzls Eroson War an Dsgn Grant Mols, Journal of Mchancal Strngth, vol.7, no.6, pp , 005. [4] H Lu, J Wang, N Klson, A Stuy of abrasv watrt charactrstcs by CFD smulaton, Journal of Matrals Procssng Tchnology, vol.53, no.54, pp , 004. [5] Yanxa Shn, Numrcal Smulaton of Straght Con Nozzl Abrasv Watr Jts Submrg, Journal of Daqng Ptrolum Insttut, vol.5, no., pp.5-54, 0. [6] Huxa Jn, Wmng Zuo, Smulaton an Hat Transfr Calculaton on A Journal Barng Wth A Cntr Crcumfrntal Groov n Loa Zon, IJACT: Intrnatonal Journal of Avancmnts n Computng Tchnology, vol.5, no., pp.54-6, 03. [7] Mngchang Lu, Rarch of Tubng Clanng by Hgh Prssur Jttng Watr Flow Tchnqu, Flu Machnry, vol.3, no.9, pp.34-36,