Francis Turbine

• .1 INTROOUCTION

Foin.cisturbinci•an.'actionturbi"""ha"in1mi.1<etl flow. [I h""OHllal m1Q'ornl ex.al axil of waler. H is a \'Cf>ll11lc machine and works w11h m..'tl1um heads and d1..:~.

Thcl>'l!1crfl\lflldicpc:ns1ockrsadmincd1<.>1hc~pi111lcuin11or..:n.>llca1i1111

"'hirll disuibu1eslhewot<'re<jlllllYoroundlhe1urbinc. ThcguidcVDt11S(v.ictc1 gatcs)fixcdallaroundtheturbmcdm:cts thcwatcrtothcrunncrblOOcs.Apanof prc$Surcent'ltl)°isoon,•crteJinto b nc11ccncrgYin theguiUt •·111C$.Thcrunninll blades utilize lhc kinctic cnCJC n ..-ell as ~sun: cnc'll)' of '"alcr to produce power.As1hcrunncrro1a1ctundc-rl/ll:n:ac1ionl)fpn:swrc, i1 iscallcdn:oction turbine.

Thc"·holeof prt!S.Wn::CnergYof wm<!r isu1ihzedandwatcr1sdischargedinto •drafliubc:.Thcfm:cndofdrafl1ubc:i1.ubmcqi:cddccpin1hctail"'·01orand• clooied waterpau;ige irnbu.ined. Some kinetic ~ofwat~rleaving the 1urbine isreco•·cm:linthedrafl1ubc.

Mainltydroelectricplanliof lndiau" Frandstufbine. The examples are Oh nkra Dam Proje.:I, lhrakund Dam Project. Rihand DJm Project. Cuun•,.y H)'dl'Ol.'lectr1cs.:hem<.',ClwnbaLll)'dl'Ol.'lectricschemc.ctc

4.2 SPECIFIC SPEED AND TURBINE TYPE

ThcspccificspccdofahYdraulicturbincisddincdM1hcsp«(LufaHC<>ITIClricallY similarturbinewhichwh..'noperati 11gund.::rahcadoflrndc'clop5lkW.

Ns !!.jJ "hen: P, • turtlinepowcr (kW)

f/ • 1 .. 1crhead(m)

N • rotorspttd(rpm)

N1 • 1pecifoc1peed~rpm)

Thcspcc1ficspccdhasl:>ccnshowntobca1,1sc fulparamclcr1ncl~1fyin1

hYdrau licturbines:andingi•inginforma1ionon1h .. genen.lsha~ormKhine.

lfperfontW>Cecharnc1ctistic.cfficiencYisploncdagainstNs;.varioo<t)"Jl"Of runncr-ssho"·optimum dlkirncY in the rangcofd1ffcrrn1 spccifocspccds. Hence. diffcrrn11ypcsofnmnen:c1nbccl11$Sili~accordillilDthcrangtof5J1CCi fic specd. lli<. lhcrefore.called''1ypecllurac1<"ris1icWorRclw,.,,,.1uspA-·tr'

Spcr1ficspccd1;of••arioosninnenarcshownmF11. 4.landTablc4.l

Wh1k:designingarunnt-rforagin•flOUlpu11ndhc:ad,1hc.!{ll."CiflcSpeede1n be , .• ,;ro bY changn1g Ilic spxd of rota!loo. II ;, a oonunon P""lkc to si:kcl a hi!lh specific speed runner ""hich is always economical because Ille size of Ille gcneni1or as well u 1hat ofpov.·t-r house will b..'Come smaller.

llighspe.:if1C" ,pe.!dise:s.sernial"hcre"1tcrheadislowa11doutf!Uti'b.'Se. be-cause Olhcrwise the spctd of rot.;illon will be wrY lo,.· which muns 0051 of grn1.-r.iitorandpowcrhouscwillbchigh.Ontlleolhcr hand.1hm:isJ'l"lClicallYno ne..'<lofsclecti11gahigh\-alueofspeciflcspe..>dforhighhcadinstallationsb«aul't

.,...m..,nhlo,«spccificspccd.hi1hrom1onalspccdcanbcattaincd"'·nhmcdmm capa.:itY planL lligh ~pecifi~ 'p<.'Cd mean_, greater \'llue ofca~i1111ion factor.

A• the head fora •itc i• fi~cd. thcspcdficifl""d can also be •·aricd by sclcctingthcuni1sizcandnumbcroFmachincs. Thcspec1ficspccdc1nbcchangcd by changing 1hc: runn<Tdiameler. ,.;Jrh ofbtmks, flumbcr of~ancs and inlet and outlc1a11g le1;. f or lowN5.brgcdmnetcra11d>1nalltipw1dthlll'l'ncedcdmxlfor high/1$. smalldiamcltrandlarir:bladcwidthan:miuin:d.

•.3 MAIN COMPONENTS

Themaintompone!l!SOfaftWK:iSturbi..eare:

2. Sptralc"'i"gorscrollc:uing

J. Guide mechanism 4. RunnerandihaAusanblY

j_Drafl1ubc

• .3.1 Penstock

l1 isawa1crw.Ytoron11C<.:1w1t<:r~"Oir101ulbinccasing.Wa1crissuf'Plied

u1Kkrprcssure.thcrcfore.1hcpcru1ock1susuallYfabnca1edfromhighqu;ili1y steel plates. Thcwddscamsan:rad!Ojµ'llphcdandsubjcctcdlobydraulictcslat Joubk:theworkin11PJtSsun:.lfthc:lcng1hof1hcpcf1s10Ckisl\hort.asepara1e pcro.11ock is run from water rest'rvo1r 10 each turbine. For m00C"1':.l1C heads and long di,tar1Ccs.1sin11kpcns1ockiiuscdmfccdtwoornKll'<:turbincs. Thepcn5locks maybcbuncJ or embedded and e~~- fapansionjointS are~ with rigid pcn.11ocbha.vingar>rhor.igc

•.3.2 Spiral Casino or Scroll Casino

A WLI111 cas1n1., pn;1>·1dcd 1on:<:<:wc,.·•1cr from pcros1ock 100 Ji5mbu1cthc same C\Cnty1round1hc1urbiM1Ua•oideddi.s&nd1oensurceqwil'elocilYOfwatcra1 1ll se<.:tton5. Jtisof•·arYin11cross•se<.:lto11an<l as:5Ume5d1cshapcof1spiral,l1m1Y bcma<kof00ncre1cf0tlowhc.odsbu1forhighhc:id<;..i1isfabrica1edfn)m.llccl pla101;orcasts1eclcasin11sareu~.

• .3.3 GuideMechanism

A !Cries ofao:rofoil-shapcd vane~ called the 11uidc •·ancs or wicket 1~1cs, an: amni;cdin.•idcthcc"'ingmformanumbcrofnowJllL<;.<agcsbct"ccnthecasing and runn<:r blades. Aerofoil sccuoo cn.1ures minimum frictional and hYdrodYflatnie"'"°''· Thc!ievanl'Jcanbc::rotatcd aroundthc.'.irfulcrumand1hus thcp.11ssage~acanbc\·aricd.Thcromionisrccci•·edfromspccdgo•·cruor

whichkcqis1he 1urbinc~cdconsl~n1wi1h•·ar)'m11oadsbYadjus11n)lthc111i<k

.-a....,watl>t"JllL<sagcandhcncethcnow.TIICguidc\·a.....,,1regen<:111llYmadcofc2s1 st..~l.

4.3.4 RunnerandShattAssemblY

ThemnncrofFrancis1ulbinc~i•-c:sw•!crfromguilkvanc:snidi•llYa00111n15 the " 'RlC'rlhrough90"so1ha1 "'B!Crisd1>ehargcdaxiallY.

Thc:~apc:Qfthc:runnc:rdc:pc:n<buPQnthc:~pcc1fic~pccd. The.-.nc:smll}'bc: ca_.;i i111egn:i.lorr1brica1ed froms1cc1p1a1cs. Thcm:a1~-na1orcoos1ruc1iooi s u>uall)'

caSI iron. bronu, cut sieel or Sia mien steel. Theshaflisaforgingandiskc)'cdlo!hcrunncr. Thc\'CMicallUlbmcshavc

onl)'on<= radial-thru>I bcaring IO take 1hc axial io..J also. The runner wort<$ bmh due to impul• iw impact ca~"<l by change in dirrction of flow H ""di H ttaetivc imp;oc1ductochangc:inprcssurcand'"doc:11Y. Thc:numbc:rofbladcsmaY•'alY bel"''CCnl6ond24.

4.3.5 OrattTube

Thc"·atcrfrom1hcrunocrisdischargcdtothc1ailrace1hroughagr,iduallY c:xp.1ndi11jj pipc:calkddrafllubc:. The fra:c:nd issubmcfllcd in tail racc,.·atcr.11 performsdullfunction.

l. ltcon,ensthcki11eticencrgYofhitwatcrin1opn~reer>e<gYdue10 mcKasin1cross-11«1ionalarca. Thccx11cncl'l)'isra:o•-crcdand1ulbinc efficicnc)'imrro•·es.

2. The lurhme is inSlallcd aOO\'e the 1;ul race lc•·cl. Then: i~ SU\'ing in cxca,<11ioo cost. The m;un1cnanc<: oftulbmc becomes easier and l\"S\llts m saving mcoM.

<t .4 VELOCITY TRIANGLES OF FRANCIS TURBINE

lnaf'rancis1urbine.1heprcssureor"·a1ttismore111heink'1thanth:r.ta11heou11ei andwotcrinthe nubincflows m a"'losl:dwnduit. Thc•..:loo;1t)'rrian&lesa1 inkt andoulktorbl:u.ko.,f f111.....,is1urbincare>hownin f ig.4,4.

Thcflowvdoo;i1)'rcmain,wnsmnt

Thedischargcisuial

l'..,• O

a, - o Workdonc~rum1massflo"··

Thcturb111Cwork,

".,-o

The111lt1•·elocilYtrianglcsdcpendupon1hespttdof1herunncr1ndare s.hownmFig.4.~.

!'1 - 90°.t 30°

a, - ?O·

''"'- o

l',,> V,,

Theh)'dr.m!occllicienc)'.

ri. -~-~ pOgll gll

' 1·,.1

•, -nY-.Jl~·

J, - W" .. tlO"

uina, - ~

l/ , '" "1.ffiiii "here • • -f;;;; • llowratio

v., ~Jfiiii "·here t ~ spcclr.1110

-4 .5 SANKEY DIAGRAM

\-- llJ- - k ol ....... .._ - --Thi: m•in I~'" in• F11111Cis turbme •re

I. \'Qlumetric:IOM<:sdue1okaka"eof"·•terb<:1wei:nguide•·•n<:S •ndrunm:r {60)

2. llydrauliclosS<'$ (i) lleadlossduetodi~harge•elOC'itY

( i i) Shockandfrktlonlos...sm·crtM\.'lln<S

). Mech.ankall~J

(i)fnc1ionl<K5C5inchcbcanngs.

( ii) Windaac losscs.

I . \'olumctnccfficicnc)'.

fluidPO"'·crTrM1§fcm:d10V1lll:ll ,,,., .. f'O"'erAvailableatlnlettoTubine

(0.96 - 0.911)

,,. .. FluidPower Tn1nsferttdw Runncr

Flu1dJ>u,.·crTnmsf(Crm!ioVancs

J. Mtthanical cffK:irocy

"-• • Fluid P<I"·.::~.::.:::. !O Ru1111CJ (O.'}S - 0.9'})

~- Turbine cffidc....,y

Thl:ovcnillcffic1c....,Yof1urbinc

11, • 'l.00 '4'1 ... u·

4.6 DESIGN OF FRANCIS TURBINE

Thi: site ·••alcrhcada»d1otal l'O"·crtobedcwlop..."'darc koown,thcspccd of twbinc •nd turbine powcr 3n: scla:lcd lO ii:ct specific speed nttcSYt)i for th!: l)'J)C ofrnrbim.<ksin.'<l. Prac1icallyalldimcnsion.~fca1Unsandcharac1eri,;iiC1iof1hc

desired turbine can bcuprcs!>Cdasa funcuonof1hcspcc1fic lpttd. Hence. "f)«ifics.pccd i~thc kJ&ica lkcYlo 1hcdc.iJ>110f1t.. 1urbinc.

4.6.1 Speed Ratio and Runner Diameter

l'hc speed ratio which Bi•·cs maximum lurbinccffK:K:rteY 1s dmo!Cd as • , and its •11lucrnnge:<bcl,,.ccn0.55and0.9 . This ' ·alu.::may bcchlngcdintlicdcs1J>11 bY ahcnng certain angles .. id llNli of nmncr. The n."COmn><."t1<lcd •·al..cs of O, for difl'cn:nlspa:ifK: spa:d Ns arcg1'"cnmFig. 4.8

''· - ~''

lfB i•thcwidlhorhl:igh1oflhcrunner. firwl thcn11ioB/DfromFlg_4.I!

"mt] " •• t, ., 0'° 100 '"°~:so JGO

Thcflowr.Hio.

Where V, FloW\"dOCil)'

0 Arcaofnmnttx f lo" wlocitY

Takll!ll inio-ni 1hee1T~1ofblade 1hitkni:n(abou1 5~)

0 0.9SnDBl'1

B o · "' 0 • (0.9511mo')"IJ2iii

where P, • Turbm<: powtt[kW]

Thcsp«ifksp=l.

. . (1)

.(2)

. .. (3)

The flow ratio 'I' can b<:e~presstd in ttmlsofNs- t. Dand 11 1 wi1h1he hdpof cqualions(I). (2),and(J)y is useful in fi~in" inlclande~il an;lcsofbladcs.

4.6.3 BladeAnales

Tho:whirlro.uo.

where 1'.• whirl•·cla<;ilY

tana, • !

tan ~1 • (~~t) o.i - oo•.

E.t . o.s ~

4 .6.4 Number of Runner Vanes

lnonkr10aw1dan)' pul~ltons,1herunn<:rvani:sari:ofknm..dc•noddnumbcr.

Zowslll rKomm• nd•tlons Numberofruntl<:fV11n~-s.

11 • KJD K • l.7 For~lowrunner

K • l.Ofornonnal runncr

K • 2.2forfas1runn<:f

D • Runn<:rdm1T1C1crin fi:c1.

K' • 2.Sfora1 be1,.·«n !O"and20"

K' • l.Oforn1betw«n20"and30"

K' •3.5 fora1 bc1,.·«n30"and40°

The values ofn and 1f J.hould nol be umc norofan)' smglc multiple 10 avoid pulsations.

4.6 DESIGN OF FRANCIS TURBINE

Tbc•i!cwa1crh<-adal>dt<Kalpo,.crtobedewlopcdun:known.thcspc<"dof 1urbmc..idmrbin<=po"'·aar<:Kln:lcdto1<:1'f'CCificsp«dnccCliWlrYfor1hetYpc ofturbinede'i~.PmctictllYalldimonsioo,;,feature..andcharae1<.'fi>Li<:ilof1hc

dcsin:d 1urbmecanbeexpressed HI func1iooof1hespecific sp«d. fkll«. s1>«ificsp:edislh<:kl1icalkcY 1othcdf:si11.11ufth<:1urbin<=.

4 .6 .1 Siaed Rallo and Runner Oiamtler

Tbesp:edrat10.

·-~

v.-•.f2iii lhcsp:ed ratio which ll l>"CS maximum turbmc dlkK:ll<:Y isdcooled .. t, ul\d

ils•·at...,rangcsbetw"""O.SSa,,.J0.9.Thisvaluem;i.ybechangNinllt<<k•igpbY alttt1ngccrtain1ngle:1andattaSofninner.Thcn:conunendcdvaluesofO,for d1ffrn:mspcc1fklpccdN5 an:g1>·on1nfig,4 .8.

"·· ~\'

o - ~./2iii lf8 i>lhel>'id1horheightof1hcn1nncr. fi ndlhcn11ioR/DfromFig.4.H.

"iEHJ '·' •. ..

~50 l(lf uo !(If) 1'° *

ThellUl>'nllio,

If Flowwlocicy.

0 Areaofnmner>tflow•·elodO'

• r:f)81'1

T1km1 into Krount 11t< effect of blade 1h1drncs.• (about 5.,_)

0•0.95r:DBVr

• 0.9Sr:DR•./fiii

B 15 • 111

0 • \0.9Sr:111tf)•./fiii ... (I)

Thcturt>i111'0>>:ni.lldf1<:icncy.

~ .... - p()gll .(2)

when: P, • Turbinc:!X"'·Cf[kW]

•.. (3)

Th<: now r.ot"1 If can be c.~P"SsW in 1crms of N5• •· D •nd 11, wi1h th<: h<:lp of eqwuion~(l).(2).and(J)ll" is u;;.e folinfixinginLe1andc•i!ang~ofblalk.~.

4.6.3 Blada Anolas

Thc•••hirlmio.

V.•whirl•docitY

1ana1 t tan IJ1 (~~.)

Number of Runner Vanes

lnor<krio a~oid anYpulsatioo s. 1h<:runncr nncsar<:oftcnmadc •noddnumbcr.

ZowdlrKommand1flons Numbcr of n>nl>l'r•"llncs.

K • J.7forslowrunncr

K •l.Ofornormalrunncr

l\ • 2.2forfastrunncr

D • Runl>l'rdiamctCfinf""1.

4.6.5 NumberofGulde Vanes

/..~ ·2.$ forn:,bctv.Cflll0"and20"

K • J.0fora1 bc1v.Cfll20"and JO•

l\' • l.$for o: 1 bct,.·cct1JO"and40"

The ~•luc• ofn and~· •hould no1 be .. me norofanY ""lie multiple 10 ••·oid pul ... tioo•

4.7 DESIGN PROBLEM

O..--signa mrbon1:for1bcfollov,.1ng•i•cconditioo<

llcad•JZOm f'mo·cr •Sx l20MW.

No.ofpcn.ioc k• • Sw1thhc:idl0Mducmmc1ion .,J._ of1""shc.ld.

lcnKthofpcmlOCk • llOOmcach.

I f>.-te,.,,.inari<mof•mlt'rflo'o<•ral<!

Assumco•·mill111rbinecff1eicncY. l'l, • 0.87

Thc(rictionfx lor r -o.oos T\,,_ • 0.97(Ginn)

Grm1 head.II, • l?Om{Given)

Thcturbincpu.,.·a,

P, • p0gll1ri.,_x 11,

O• ____JL__ • 120xl0" pgllg'1.-X 'l, IOOOx9Jllx1lOx0..97xOJl7

(J,/~ • 0.D} x l20

0 ·7D'I' ,,.;g,

t:.11 -~ 1 2g0

J.6 - " ;~~;1:1~00 ·(":;or f>' . 4 x0.00Sx lJOOx l20

1x 4

1 • SS9Jm'

J-6x11x2x9Jll

w .. 1.,.,·cloei1Y 1hroughcx hpcnS10<k,

l' •~ - 4 x 1 2? • 4.2Sm/1 OK 'fl.lJ"" lfx6·

}1jp<'<ifturbiM

The<p«ific spttd.

Ns •~ From Fr:md•11ub1ncac Bhnra Po.,.·u l'roj«t.p • 18 •ndN• l66.7 1p111

1 66.7><~ N, • (lf

0-Alf

1)''

1 66.7x~ -~ • ISlrpm.

ForFranc,.tutbincfromF1g. 4.landTablc4_1.wnnolnmnui• •uitablcfor Ns • l ~ I rpm.

J Spi"1/ NUing

Thcsp1rul casin11d1am<:1ord,. can belakrnlcs.or<:quol1opcn'iockd1;1.1nc1cr. Al'°"'·ablc l't' canbcta~cn .. IOmls.

o - ~d/ l'r

- ~ Y-.-xiii

Jfe, is li.tcdto • ccomm00:11erunr'IC'randgu1<k•·ann.

Jfe,• Rc. • ~d,. ThcdimcnJioos of51!i111lc1151n1i1 focdb)' d111winii1o liCll lc.

lkrunm:rdi-.nc1<:r,

o, - ~.pgik. Roadfromgraph. o 0.7S

D, • ~"~~~ J2;ic9..S ;ic llM "' " ·Im

j_ frloci'>''ri~ngl~

Now. 0 • 0.9~>< '/tBDll1

"r• 0.9~><llO><Bx/J • 0.9S><'/tl::1.l><4J • 7·97 mls.

· -~ - Jh:9~~:l16.4 • 0.167

11.i • 0.90

Fo - ~ · 2::1s · 0.60

1an (11 • t • ~~!7 • 0.218

ll n ~I "'~ "' (Q~~;1S ~ ~. •-41°

~ - 90·

6.Numl>t'rof•'<l"Jla

(i) Numbttofrunncrv....,.

for"°"""'lrunncr. K • J.O

II "' J,/4.lill • I l

(ii) Numbttof11uidc•·ann

K' · 2.5 for a ,

11' • 2.sJ4.j<l3 - 9