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GIO TRNH TUABIN THY LC

Thng 11-2010

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LI NI U

p ng nhu cu hc tp Thu in ca sinh vin khoa Xy dng Thu li - Thu in thuc Trng i hc Bch khoa Nng trong giai on mi, chng ti bin son gio trnh "Turbine thu lc - cc thit b thu lc v Cng trnh trm Thu in" (l gio trnh mn hc Thu in 2). Gio trnh ny c bin son theo ni dung " cng mn hc Thu in" c nh trng ph duyt nm 2005. Gio trnh Thu in 2 gm 17 chng, c trnh by trong hai phn ln: phn I (thit b thu in) v phn II (cng trnh Thu in): Phn I - "Turbine thu lc - cc thit b thu lc" ca trm thu in, gm 8 chng (t chng I n chng VIII). Phn ny dng ging vi 20 tit trn lp, ni dung tm hiu: turbine thu lc, thit b iu tc, cc thit b ph v cc h thng thit b ph thu lc ... v cu to, tnh nng hot ng cng nh la chn, tnh ton xc nh cc thng s c bn v kch thc ca thit b phc v cho thit k trm thu in. Phn II - "Cng trnh trm thu in", gm 9 chng dng ging 40 tit trn lp, thuc hai phn: Phn IIa -"Cc cng trnh thuc tuyn nng lng" vi 7 chng (t chng IX n chng XV), bao gm cc cng trnh thuc tuyn nng lng: ca ly nc, b lng ct, cng trnh dn nc, b p lc, ng ng turbine, bung iu p. Ni dung trnh by v cu to cng nh tnh ton xc nh kch thc cc cng trnh thng qua tnh ton thu lc v tnh ton dng khng n nh ca chng. Phn IIb - "Nh my thu in", gm 2 chng XVI v XVII, ni dung trnh by cc loi nh my thu in v mt s thit b c in ca chng, cch b tr, xc nh kch thc nh my, tnh ton n nh v tnh kt cu cc phn di nc ca nh my. Gio trnh ny cp kh y ni dung chuyn mn ca mn hc Thy in 2, p ng 60 tit ging trn lp v cn c th dng tham kho thm sau ny khi sinh vin ra trng tham gia vo lnh vc thit k cng trnh thu in s gp phi. Trong qu trnh bin son gio trnh, do kh nng c hn do vy khng trnh khi thiu st, mong nhn c nhiu kin ng gp ca ng nghip v bn c sa cha cho tt hn. Thng 5 - 2006 Tc gi

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Phn I TURBINE THY LC & CC THIT B THY LC CA TT

Turbine thy lc l loi ng c chy bng sc nc, n nhn nng lng dng

nc quay v ko r to my pht in quay theo to ra dng in. T hp turbine thy lc v my pht in gi l "T my pht in thy lc". phn ny chng ta ch nghin cu v turbine thy lc, thit b iu tc v gii thiu mt s h thng thit b thy lc c lin quan .

Chng I. KHI NIM CHUNG V TURBINE THY LC

I. 1. PHN LOI TURBINE THY LC CA TRM THY IN

Trong qu trnh u tranh sinh tn v ci to th gii t nhin, loi ngi sm bit s dng cc ng c thy lc: t nhng bnh xe nc dng vo vic ko my xay xt nng sn n pht trin chng ln thnh nhng turbin thu lc hin i ko my pht in sn xut ra in nng ngy nay. s dng mt cch c hiu qu nng lng dng nc c trng bi t hp ct nc v lu lng khc nhau cn phi c nhng loi turbine khc nhau v cu to, kch thc cng nh qu trnh lm vic ca chng.

Da vo vic s dng dng nng lng trong c cu bnh xe cng tc (BXCT) ca turbine ngi ta chia turbine thy lc ra lm hai loi: turbine xung kch v turbine phn kch. Trong cc loi li chia ra cc h v cc kiu turbine.

Vit phng trnh Becnully cho ca vo (ch s1) ca ra (ch s2) ca bnh xe cng tc turbine, ta c nng lng vit cho mt n v trng lng nc nh sau:

H = (Z1 - Z2) + p p1 2

+ 1 12 2 22

2V V

g

Z1-Z2 : l thnh phn nng lng do chnh lch v tr to ra, gi l v nng;

p p1 2

: l p nng; gp v nng v p nng thnh th nng ( T ). 1 12 2 22V V

2g : l ng nng ( ).

T nhng thnh phn nng lng trn ta c nhng loi turbine thu lc sau: * Turbine ch s dng phn ng nng lm quay BXCT gi l loi turbine xung kch. Loi ny cn gi l turbine dng chy khng p v dng chy trong mi trng kh quyn nn chuyn ng ca dng tia trn cnh BXCT l chuyn ng khng p, p sut ca vo v ca ra nh nhau v bng p sut kh tr

sau: i. Turbine xung kch uc chia

ra cc h+ H turbine xung kch go (turbine Penton); + H turbine xung kch kiu phun xin; + H turbine xung kch hai ln (turbine Banki).

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y ng

sau: c ( gi tt l l turbine tm trc, hay Franxis);

+ H TB dng ( gm turbine dng na thng v turbine dng thng ); m vic theo hai ch : my bm v turbine).

dng tia trn cc cnh bnh xe cng tc (BXCT) l chng ta nghin cu c

th cc

rbine, lm uay BXCT ko theo trc turbine 5 quay, nc p vo cnh go b bn ra hai pha v c v 6 ca turbine gom li dn v hm x tho v h lu ca nh my.

* Turbine s dng c th nng v ng nng, trong phn th nng l ch yu gi l loi turbine phn kch . Loi ny cn gi l turbine dng chy c p, p lc dng ch ca vo ca BXCT lun ln hn p lc ca ra ca n. Dng chy qua TB l dlin tc in y nc trong ton b mng cnh. Loi ny c chia ra cc h + H TB xuyn tm hng tr + H TB hng trc ( gm turbine cnh qut v turbine cnh quay ); + H TB hng cho; + H TB thun nghch ( l

I . 2. TURBINE XUNG KCH Nh trn ni, turbine xung kch l loi ch s dng phn ng nng ca dng

chy. loi turbine ny, dng nc sau khi ra khi vi phun th ton b nng lng dng chy u bin thnh ng nng y bnh xe cng tc. V chy trong mi trng kh quyn nn chuyn ng ca chuyn ng khng p hay cn gi l dng tia t do. Sau y

h ca turbine xung kch: I . 2 .1. Turbine xung kch go ( cn gi l turbine Penton )

Turbine ny do ngi M tn l Penton a ra nm 1880 nn cn gi l turbine Penton. Qu trnh hot ng ca turbine go nh sau (xem hnh 1-1): nc t thng lu theo ng p lc 1 chy qua vi phun 2 ( y lu lng c iu chnh trc khi phng vo cnh BXCT nh van kim 7), ri phng vo cnh dng go 4 ca tuq

Hnh 1-1. Turbine xung kch go Sau y chng ta xem xt cu to v tc dng cc b phn chnh ca turbine go

(hnh 1-2). Vi phun 1 nhn nc t ng p lc bin ton b nng lng dng nc thnh ng nng trc khi a vo BXCT v iu chnh lu lng vo turbine nh dch

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. S ph hp dch chuyn van kim v thit b tch dng lin hp vi nhau nh c cu lin hp trong my iu tc (xem chng VII -Thit b iu tc ca turbine thu lc).

chuyn qua li ca van kim 3 t bn trong (hnh 1-2,a). Turbine go ct nc cao v ng p lc di cn c b phn tch dng 5 hng mt phn hay ton b tia nc khng cho vo BXCT trnh hin tng nc va xy ra qu ln khi ng nhanh van kim ca n. B phn ny ch lm vic khi ct gim ph ti my pht in. Khi ph ti gim, van kim cn phi nhanh chng ng bt m gim lu lng thich hp, tuy nhin nu van ng qu nhanh trong vi phun s xut hin p lc nc va qu ln lm b vi phun. gim tr s p lc nc va, lc ny my iu tc s nhanh chng nhc thit b tch dng 5 ln ngt bt phn lu lng tha ra khi cnh go. Nh vy lu lng vo BXCT vn gim ngay theo yu cu gim ti m van kim ch phi ng t t

i

Hnh 1-2. Cc b phn chnh ca turbine go

Bnh xe cng tc ca turbine go ( hnh 1-1 v 1-2b,c ) gm c a 1 trn chu vi a c gn cc cnh dng go 2 (nn gi l go). Ph thuc vo ct nc m s go c t 1460 cnh. BXCT c th l mt khi lin khi cc cnh go v a c c thnh mt khi, v khng phi l khi lin khi cnh go c c ring v c gn ln a bng bu lng hoc hn. Chnh gia cnh go c gn 3 chia go lm hai phn bng nhau chia tia nc tc ng vo go thnh hai phn i v hai hng bn ra hai bn. ui di ca cnh go c khot hm 4 cho tia nc xuyn qua hm ca cnh trc

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p th c (th o chi ay n ca mmen quay v trnh mmen ng c.

V turbine c n ra ngoi gian my. V

c b tr u chung

ng vo cnh go thng g e u quay) lm tng cnh tc ca tia nc vo pha sau go nm pha tr

him v khng cho nc t bung BXCT bn phi c kch thc v hnh dng th no hng nc t go xung hm x

m khng ri ngc tr li pha sau go lm cn tr vic quay ca BXCT. iu ny rt quan trng i vi turbine go trc ng c nhiu vi phun.

Hm x c nhim v tp trung nc sau khi i khi BXCT li dn v h lu. Mc nc trong hm x phi bo m thp hn cao trnh thp nht ca BXCT mt khong no , thng l bng ng knh D1 v t cao hn mc nc trong hm x.

Loi trc ngang thng c cng sut b v c t mt n hai vi phun cho mi BXCT (hnh 1-1,b), s lng bnh xe cng tc trn mt trc thng nh hn ba. Loi trc ng c s vi phun nhiu hn, thng hai n su vi, quanh BXCT. Hnh 1-3 l biu th turbine go trc ng c su vi phun.

Mt bng Mt ng

Hnh 1-3. Turbine go trc ng nhiu vi phun

Turbine go s dng ng nng quay do vy cn to nn vn tc dng phun ln tng cng sut turbine, mt khc kt cu BXCT rt vng chc do vy turbine ny c s dng vi ct nc cao lu lng nh. Turbine go loi ln c phm vi s dng ct nc t 2002000m hoc hn na, turbine go loi nh th t 40250m. Trc turbine go c th ng (hnh 1-3) hoc ngang. Trm T Bgta Clombia t n ct nc rt cao H = 2000m, cng sut lp my N = 500 MW. Trm Raisec c c ct nc H = 1767m. Nc ta c cc trm H = 500800m nh Vnh Sn v a Nhim, s dng h turbine xung kch go. I. 2. 2. Turbine xung kch hai ln ( turbine Banki )

Turbine xung kch hai ln c phm vi s dng ct nc t 6150m, thng t 1060m. Kt cu ca n rt n gin (hnh1-4), d ch to nn c s dng rng ri

, ccc trm thy in nh c lu lng b t nc va, trc thng nm ngang.

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Hnh 1-4. Turbine xung kch 2 ln

Turbine gm c vi phun tit din hnh ch nht 4 c ni lin vi on ng chuyn tip 8. Vi c c cu iu chnh lu lng gm van phng 3 gn vi trc iu khin 2 c tay quay v lng. Khi v lng quay, trc iu chnh s tnh tin v pha trc hoc pha sau lm cho tit din ra ca vi phun thay i, nn lu lng vo turbine cng c thay i theo. Bnh xe cng tc gm cc cnh cong 7 c gn gia cc a 6, s cnh t 1248. Trc turbine xuyn qua gia bnh xe cng tc gn cht vi cc a bng then. V (bung) 9 dng chn khng cho nc t BXCT bn ra ngoi. Hm x 5 c nhim v dn nc v h lu.

Hnh dng BXC ng sc. Dng nc t vi phun tc dng vo cc cnh pha trn (nhn khong chng 80% nng lng ca

ht, xong li i vo khong trng gia BXCT ri li tc dng l

y c th ch to turbine vi ng knh b c vng quay ln, do vy gim gi

thnh ch to turbine v t my thy lc. I. 2. 3 Turbine xung kch phun xin Turbine xung go ch khc

T turbine xung kch hai ln gn ging l

dng nc) y BXCT ln th nn th hai vo cnh trc khi ra khi bnh xe cng tc (nhn thm 2030% phn

nng lng cn li). Cng chnh v th ta gi n l turbine xung kch hai ln. Hiu sut ca loi turbine ny ty thuc vo s cnh ca BXCT v vo khong 8085%. u im c bn ca turbine xung kch hai ln l c th chn ng knh BXCT v s vng quay turbine trong mt phm vi rng m khng ph thuc vo lu lng, bi v lu lng khng ch ph thuc vo ng knh m cn ph thuc vo chiu rng BXCT na. Nhv

kch phun xin (hnh 1-5) c hnh dng ging turbine kt cu BXCT v hng ca tia nc vo BXCT. Tia nc bn vo BXCT khng trc giao vi cnh m lm vi cnh mt gc , nh th c th lm vnh ghp mp ngoi ca BXCT nn n gin ha c cch ghp cnh vo a. Hnh dng cnh loi ny cng d ch to hn. N cho php gia cng hng lot bng cch p. Turbine tia nghing t c s dng rng ri, n ch c s dng TT nh c ct nc vo khong H = 30400m.

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Hnh 1-5. Turbine xung kch phun xin

I . 3. TURBINE PHN KCH

Turbine phn kch l loi s dng phn th nng v mt phn ng nng ca dng nc. Bnh xe cng tc ca n lm vic trong mi trng cht lng lin tc v p lc nc pha trc bnh xe cng tc ln hn pha sau ca n. Khi chy qua rnh to bi b mt cong ca cc cnh, dng nc s thay i hng tc dng ln cnh v lm quay BXCT. Da vo hng ca dng nc ca vo v ca ra BXCT ngi ta chia turbine lm cc h: tm trc, hng trc, cnh cho, turbine dng, thun nghch.

Hnh 1-6. Cc b phn chnh ca turbine phn kch.

Xt v mt cu to, bt c h turbine phn kch no cng gm cc b phn chnh sau: bung turbine 1, vng b 2, c cu hng dng 3, BXCT 4, bung BXCT 5, ng x 6, trc v trc 7 v cc thit b ph ca chng (hnh 1-6).

Su b phn u hnh thnh b phn qua nc ca turbine, cn trc v trc l b phn kt cu c nhim v tip nhn v truyn m men quay t BXCT n rto ca 8

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my ph

I. 3. 1.

theo hng dc trc. Do vy gi l turbine tm trc. Turbine ny do k s ngi i l turbine Franxis.

t in. Trong cc b phn qua nc th BXCT l b phn trc tip bin i thy nng thnh c nng chuyn ng quay. B phn c cu hng nc c tc dng thayi tr s lu lng v hng dng chy trc khi i vo BXCT, cn ng x c dng tho nc t BXCT v h lu.

Sau y chng ta ln lt xem xt cc b phn ca turbine phn kch, cc h turbine khc nhau ch yu l bnh xe cng tc cn cc b phn khc nhn chung ging nhau. Vic phn loi TB phn kch da vo hng dng nc i vo v ra khi BXCT.

Bnh xe cng tc ca turbine tm trc (turbine Franxis ) Turbine tm trc (xem hnh 1-7) l mt trong nhng h TB phn kch c s

dng rng ri nht. Cht lng t bung 4 qua cnh hng dng 3 vo ca vo cnh 1 BXCT theo hng xuyn tm ri chuyn chuyn hng 900 v ra khi BXCT vo ng xPhp tn l Franxis hon chnh nm 1849 nn cn g

Hnh 1-7. Bnh xe cng tc ca turbine tm trc BXCT ca turbine tm trc gm c vnh trn 14 v vnh di 13, cc cnh 1 c

dng cong khng gian ba chiu gn cht vo hai vnh. S cnh t 12 n 22 cnh, thng l 14 n 18 cnh. Thng BXCT c c lin thnh mt khi, trng hp b iu kin vn chuyn hn ch c th ch to BXCT thnh tng phn, khi lp rp s dng cc bulng ghp vnh trn v ai ghp nng vnh di ca cc phn li hoc hn

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ni cc rnh phn chia. i vi turbine nh c th dp cnh, sau nh v chng ri c lin vnh trn v di c BXCT lin khi vng chc.

Ty theo ct nc s dng, ng knh ln nht ca vo D1 (ng knh tiu chun) v ng knh ln nht ca ra D2 m ngi ta chia turbine tm trc lm 3 dng: - Dng D1 < D2 gi l turbine t tc cao loi ny dng vi ct nc thp (H< 80m) v cu to ca chng c kh nng chu lc khng cao (hnh 1-7,b); - Dng D 1 > D2 gi l turbine t tc thp (hnh 1-7,c) loi ny c cu to vng chc do vy chng c dng vi ct nc cao, c turbine lm vic vi ct nc 550m; - Dng D1 = D2 gi l turbine t tc trung bnh, n l loi trung gian gia 2 loi trn.

Turbine tm trc c phm vi s dng ct nc thng t vi mt n 550m. nc Nga, Trm thy in Cracnoarck s d oi ny vi cng sut mi turbin l 508MW, ng k An u dng turbine

ng l enh D1 = 7,5m. nc ta, TT sng v Tr

tm trc, TT Ha Bnh dng 8 turbine tm trc, cng sut mi turbine l 240MW, H = 88m. I. 3. 2. Bnh xe cng tc ca turbine hng trc

Gi l turbine hng trc v hng chy ca dng nc trong phm vi BXCT theo hng trc quay ca turbine. Trn (hnh 1-8) nc t bung xon chy qua ct vng b 10 vo cnh hng nc 3 i hng v chy vo v ra khi cnh 11 ca BXCT 1 theo chiu dc trc v theo ng x v h lu nh my.

Hnh 1-8. Turbine hng trc. BXCT gm c bu 1 c ni bch vi trc turbine 2, xung quanh bu b tr cc

cnh hnh vn v p lc nc tc ng ln cnh lm quay BXCT. Lin kt gia cnh v bu theo kt cu cngxn nn chu p lc thp, s cnh thng t do vy kh nng tho nc ln. Trong h hng trc da vo s lin kt gia cnh v bu ngi ta chia h hng trc ra hai dng: turbine c cnh gn c nh vi bu l turbine cnh qut, cn turbine cnh c th quay quanh trc ca n trn bu l turbine cnh quay.

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1. Turbine cnh qut BXCT ca turbine cn u, c gn t 3 n 9 cnh, h qut (hnh 1-9) gm c b

thng thng l 4 n 8 cnh. Cnh c th ch to lin vi bu to thnh mt khi thng nht hoc ch to ring bit sau gn cht vo bu bng bulng. Khi i qua cc mt cong ca cnh, dng nc buc phi i hng chuyn ng do to ra mt p lc tc

Hnh 1-9. BXCT ca turbine cnh qut dng ln cnh lm quay BXCT. Nhc im ca loi BXCT ny l c ng c tnh cng tc dc, do vy khi lu lng, ct nc hoc cng sut thay i lch vi ch thit k th hiu sut turbine s gim i rt nhanh. i turbine t tc cao ch cn lu lng gim n cn 45% lu lng tnh ton th hiu sut v cng sut c th gim n khng. Do vy nn cho turbine cnh qut m nhn cng sut v ct nc t thay i. Turbine cnh qut c s dng Trm thu in c ct nc H = 1,540m, hin nay thng dng TT nh, tuy rng c turbine dng ny ng knh t n 9 m.

2. Turbine cnh quay ( Kaplan ) Turbine cnh quay (hnh 1-10) l loi ra i sau cnh qut. Nm 1924 gio s

ngi Tip tn l Kaplan ci tin thnh cng turbine cnh c nh thnh cnh quay c, nn turbine ny cn c gi l turbine Kaplan. Nh cnh c th quay c xung uanh bu, do vy thch ng c cc ch lm vic khc ch thit k dn n

vng lm vic ca turbine v . Do vy TB cnh quay c kh nng lm vic vi cng sut v ct n i nhiu. BXCT ca TB cnh quay

qi hiu sut cao c m rng

c thay gm c: bu, cnh, chp thot nc v b phn quay cnh xung quanh BXCT. Bu phi c hnh cu gim bt khe h gia cnh vi bu khi quay cnh. Chp thot nc c tc dng lm cho nc chy khi BXCT thun dng hn v gim c tc dng mch ng. Khi lm vic, cc cnh BXCT hng trc chu tc dng p lc nc dng s chu lc kiu dm cngxn do khng c vnh di, ti ni tip gip cnh vi bu chu mmen un ln nht. Ngi ta o c p lc nc tc dng ln mt cnh c th t ti 240 tn. Do vy phi s dng ng c tip lc du cao p mi quay c cnh .

B phn quay cnh gm trc cnh 6 (hnh 1-10,b), ng c tip lc 4, h thng thanh truyn 7. Tay quay 8 c ni vi trc cnh 6, cn thanh truyn c cht ni lin

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u c p vo mt ngn no ca xi cn ngn kia du thng vi l du x th pittng ln thanh truyn 7 s dch ln

pttng 5 ca ng c tip lc vi tay quay. Pittng 5 chia xi lanh ca ng c tip lc lm hai ngn: trn v di. Du c p t thit b du p lc qua hai ng dn ng tm lng vo nhau nm bn trong trc t my. Khi dlanh

Hnh 1-10. Turbine Kaplan xoay cc cnh theo cc gc quay nh nhau. So vi turbine cnh

ut th turbine cnh quay c dng vi ct nc thp hn do kh nng chu lc ca n c yu hn. Cng vi turbine tm trc, turbine cnh quay c s dng rt rng ri. Ngy nay th gii c nhng turbine cnh quay cc ln, nh TT Xaratp Nga c ng knh tiu chun D1 = 10,3m, ct nc thit k H = 9,7m, vi cng sut N = 59,3MW, vng quay nh mc n = 50 vng/pht, trng lng 1229tn. Turbine trm T Porto Primavera Brasil c D1 = 8,6m, N = 105MW, ct nc H = 22m.

hoc xung, do lmq

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I. 3. 3. Turbine cnh cho

Hnh 1-11. Turbine cnh cho

trn. Turbine cnh cho c s dng cc TT c ct nc H = 30150m. N thuc h quay. BXCT gm 10 n 14 cnh c gn vo bu 3 hnh chp nh

c cnh 2. Trc cnh lm 0,450,600 nn dng chy trong XCT ho gc vi ay, cc cnh BXCT quay c

oi turbine ny T Buctamin c cng sut N = 77MW, ct nc H =

61m,

Turbine cnh cho (hnh 1-11) c ra i chm hn cc loi turbine trn, n l loi trung gian gia tm trc v hng trc. N kt hp c cc u im ca hai h turbine

loi turbine cncc tr vi trc turbine mt gc 30B c trc. Cng nh turbine cnh ququanh trc ca n, nh c cu quay cnh gm vnh sao 5 v thanh truyn 4 nm trong bu nn hiu sut bnh qun ca n cao hn turbine tm trc hu ht cc ch lm vic. Mt khc s cnh BXCT ca turbine ny nhiu hn so vi turbine cnh quay nn c th lm vic vi ct nc cao hn m vn khng b kh thc. Lc ch to Nga dng cho T

ng knh D1 = 4,35m, n =150 vng/pht.

Ngoi ra, TB cnh quay lm vic vi ct nc thp, mun chu c ct nc cao hn th phi tng s lng cnh BXCT ca n ln t 6 n 10 cnh. Nh vy bu BXCT phi c ng knh ln. c th tng s cnh m khng phi tng ng knh th tt hn ht l trn mi trc cnh lp hai cnh kp (hnh1-12). Loi ny c lp t nh my thy in Thc B vi ng knh D1 = 4,5m, H = 32m.

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Hnh 1-12. Bnh xe cng tc ca turbine cnh kp I. 3. 4. Turbine dng

Turbine dng gm hai loi: dng c y thng v na thng. Turbine dng thc

hiu sut cao hn so vi turbine phn n 30% do kh nng tho nc a n. Turbine cap xun c s dng rng

i Nga, Nht, M... cc sng vng ng bng hoc cc TT thy triu. Trm T Trereparec c cng sut mi turbine N = 20MW, H = 14,9m. Trm thu in c turbine cp xun ln nht l Kiev c N = 320MW.

hcht l turbine cnh quay trc ngang, nn BXCT ca n hon ton ging turbine cnh quay. Loi ny dng vi ct nc rt thp v lu lng rt ln.

1. Turbine dng na thng (hnh 1-13), turbine ny cn gi l turbine Capxun. T my c turbine trc ngang ni lin trc vi trc my pht in t trong bc kn bng kim loi 1 (gi l cp xun) c dng thun dng. Cp xun cha my pht in c th nm trc BXCT hoc nm sau BXCT trong ng ht thng 2. Cc cnh hng dng 3 thuc loi hng tm hoc hnh chp. Stator thuc loi v cng vi cc tr ta s truyn ti trng t my ln mng my. Lin h gia cc thit b t trong cp xun vi gian my bng cc thp 4. Turbine cap xun c kch khc r

c

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Hnh 1-13. T my cp xun

Tur d turbine dng thng (hnh 1-14), dng n ng turbine hnh tr th

a r t n hng dng 2 v tc n T u theo t R m y pht in 4 n vo m cnh d q

2. bine ng th ng

c theo bu ng i qu Stato rc 1 vo b ph g vo BXC 3 v h ldng hng. tor c g t TB, o vy khi BXCT uay

Hnh 1-14. Turbine dng thng

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v my m tr

th cng chnh l rotor quay. Turbine dng thng c cu to phc tp, c bit l cc vng m chng thm vng quanh m hiu sut khng cao hn turbine hng trc bnh thng my, nn t c s dng. Trm thu in Ortatran Lin X c s dng turbine ny vi cng sut turbine N = 6,3MW, ct nc H = 10,5m. I. 3. 5. Turbine thun nghch

Turbine thun nghch c dng trong " t my hai my" cc TT tch nng, c kh nng lm vic hai ch : bm nc v pht in. T my gm c hai my: turbine thun nghch v my in ( "my pht in - ng c in") lm vic 2 ch my pht v ng c. T my loi ny thay cho cc loi t my lm vic cc ch ring bit khng kinh t hoc " t my ba my ". Nguyn l lm vic ca turbineb i ngc nhau, do vy lm vic mt ch c th phi chnh chiu quay cnh thch hp vi tng ch lm vic. Sau y l mt v d v turbine Capxun thun nghch (hnh 1-15). Turbine ny gm c cc b phn chnh sau: BXCT 1 l TB thun nghch c kh nng thay i gc nghing cnh theo hai ch bm hoc turbine; c cu

Hnh 1-15. Turbine Capxun thun nghch

ng dng (CCHD) 2 dn i ch bm hay turnine; c gn c nh vo btng nh my nh cc ct 3.

g hnh cn thay i ph hp vh

"bng n" (capxun) 4 kn nc, Bn trong cpxun 4 b tr trc t my trn ta 6 v chn 7 v "my pht - ng c" 8. Ging thng 5 c dng t cp in, ng ng dn du ..v.v...n ng c tr ng ca BXCT v ln xung gian my pha trn. BXCT thun nghch c ng knh

0 05,35m, bn cnh quay xung quanh bu vi cc gc t -5 n +35 so vi v tr tnh ton. Vi cng sut 10 MW lu lng bm c l 105 m3/s khi H = 6m v 225 m3/s khi H = 1m; lu lng ln nht ch turnie l 230 m3/s . Vng quay n = 97,75 v/p, my pht - ng c ng b, c in p 3,5 kV.

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Chng II. CC B PHN CHNH CA TURBINE THU LC

chng I chng ta nghin cu khi qut v cc loi turbine v tnh nng ng u c th hn v cu to, cng dng

b phn chnh ine

u stator : kiu ct ring r v kiu vng (a). dng kiu vng tng cng, cn kiu ct

ng r

dng ca tng loi turbine. Chng II s nghin cca cc b phn chnh ca turbine v tm hiu cc xc nh kch thc ca chng. Ngoi BXCT, cc b phn chnh ca turbine gm: thit b dn nc (bung turbine), thit b tho nc (ng x), phn tnh (stator), c cu hng dng (CCHD) ..v.v..

. II. 1. VNG B, C CU HNG DNG, TRC CA TB. PHN KCH

Nh trn ni, ngoi BXCT, turbine phn kch cn c nhngrc v trc ca turbsau y: vng b ca turbine, c cu hng dng, t

II. 1. 1. Vng b (Stator) ca turbine: Vng b ca turbine (hnh 1-6 v 2-1) l phn c nh ca turbine, c tc dng

my, sn v btruyn xung mng nh my cc ti trng gm trng lng ton b t my pht in, p lc nc dc trc tc dng ln BXCT v khi b tng ph ln n v.v... Stator bao gm mt s ct chng 2 vi tit din ngang hnh ng dng, lin kt vi vnh trn 1 v di 3. C hai kiPhn ln cc turbine phn kch u sri ch s dng cho bung xon b tng ct thp, chn khng lp trn np turbine. S lng ct stator bng mt na s cnh hng nc.

Hnh 2-1. Vng b v CCHD ca turbine xc nh kch thc bung xon cn phi bit hnh dng v cc kch thc ca vng b v cnh hng dng.Hnh kch thc vng b (stator) 2-1,b v bng (2-1) xc nh

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ca turbine. Trong bng: Da, Db l ng knh ngoi v trong ca vng b, b0 l chiu cao cnh hng dng (bng 6-5 v 6-6 chng VI), Z0 l s lng cnh hng dng.

Bng 2-1. Bng kch thc vng b ( n v cm)

D1 D0 Z0 Cho bung xon b tng ct thp Cho bung xon kim loi cn D D D R h h D D D R H

h b a 4 1 2 b a 4

180 220 16 260 305 330 20 21 200 240 16 285 335 360 20 23 225 275 16 320 375 400 20 23 250 290 24 340 390 400 28 32 23 330 390 415 25 25 280 325 24 382 438 448 30 35 25 372 438 463 25 25 320 375 24 437 500 510 30 40 30 426 500 535 30 32 360 420 24 485 500 570 35 40 30 480 555 590 35 35 400 465 24 542 620 630 35 45 35 532 615 650 35 41 450 525 24 610 700 710 40 45 45 600 695 735 40 41 500 580 24 675 777 780 40 50 40 660 765 805 40 46 550 24 745 855 805 50 50 40 730 845 885 50 46 640 600 700 24 875 935 945 50 55 45 800 925 965 50 50 II. 1. 2. C cu hng dn

ng turbine 1 chy vng qua cc ct stator 2, chy qua khe h gia

yn v

r nc cn c m chng r bng cao su. B ph

n 5 t my iu tc quay ko tay quay 6 v thanh ko 7 lm quay v

g (CCHD): Nc ln lt t bu cc cnh hng dng 3, y lu lng c iu chnh do thay i khe h

gia cc cnh trc khi vo BXCT 4 (hnh 1-6 v 2-2,a).C cu ny c tc dng sau: - Hnh thnh hng dng chy nht nh trc BXCT; - iu chnh lu lng nc vo turbine, do thay i cng sut ca turbine. B phn CCHD gm c hai thnh phn chnh: cc cnh hng dng hnh lu tuc cu quay cnh. Mi cnh hng nc c thn 3 v trc cnh 5. u trn trc cnh c lng vo cc l khot np TB, cn u di th c lp vo vnh di, nh cc cnh c th quay c quanh trc ca n thay i m a0 ca CCHD. Khi cnh hng nc ng hon ton a0 = 0, gim

n quay cnh hng dng gm c cc chi tit: np turbine 6 cha trc trn ca cnh, vng di cha trc di ca cnh, cc cnh hng 3 v c cu tay quay 7. m a0 dc thay i nh nhau cho cc cnh nh vng iu chnh 8 ca CCHD. Nh chuyn ng tnh tin hai cn 10 ca hai ng c tip lc 9 ca my iu tc m vng iu chnh 8 xoay, ko theo CCHD xoay dn vo BXCT lu lng yu cu. Hnh 2-2,b l s n gin ca CCHD dng cho TB nh trc ng bung h. Nc t bung h qua khe h gia cc cnh 2 vo BXCT 11. iu chnh m a0 theo yu cu nh trc diu khi

ng iu chnh 8 tc thay i trc 4 lm cnh hng 2 xoay quanh trc 10 ca n.

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Hnh 2-2. B phn xoay CCHD

II. 1. 3. trc v trc turbine:

Trc turbine c dng truyn m men xon t BXCT n rtor my pht ng dn du (i vi cnh quay),

n khin Trc turbine trc ng bn trong rng lp ccd xung BXCT ph chn khng cho turbine tm trc v ng dy in ..v.v... trc nh hng nh tim trc, c bi trn bng du hoc bng nc. Loi bi trn bng nc thng c lp trn np turbine. Loi bi trn bng du khong th tm bc ca trc lm bng hp kim babt.

Hnh 2-3 l th xc nh ng knh trc turbine. ng knh trc ph thuc vo mmen xon ca dng chy Mkp = 97400.N/n ( kGcm). Trong N (kW) v n (vng/pht). C Mkp tra ra ng kch trc turbine DB (mm).

Hnh 2-3. Biu quan h ng knh trc v cng sut turbine.

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nh lng chy vng ti ca vo CCHD. Bung turbine cn bo m nhng yu cu chnh sau: - Dn nc u n ln chu vi cc cnh hng dng to nn dng chy i xng i trc quay c

- Thun tin cho vic b tr turbine v thit b ph ca n trong gian my ca TT. n khng u tr

ng

II. 2. THIT B DN NC CA TURBINE

Thit b dn nc (bung turbine) l phn ni cng trnh dn nc ca trm thy in vi turbine v hnh th

v a turbine. - Tn tht thy lc trong bung v c bit l trong CCHD nh nht. - D ni tip vi ng dn ca trm thy in. - Bung c kch thc gim nh v kt cu n gin.

- p lc tc dng ln BXCT u nhau trnh m c. Da vo ct nc v cng sut ca TT m bung turbine c cc kiu: bung

h, bung hnh ng v bung xon c.

II. 2. 1 Loi bung h ca turbine

Bung h l loi n gin nht thng dng cho ct nc H = 56 m v knh D1 < 1,2 m , gii hn ct nc ln nht l 10 m v ng knh D1 = 1,6m. S d c gii hn s dng trn v khi ct nc v ng knh ln th kch thc ca bung rt ln, trc turbine di v p lc nc trn thnh bung s ln. V vy loi bung ny ch

Hnh 2-4. Bung turbine h

. dng cho turbine nh. Bung h c th lm bng g, gch hoc xy hay bng btng Bung h c th trc ng hoc trc ngang v h ch nht hoc h xon. Bung h ch nh to nn dng xoy cc gc lm tng tn tht ct nc. khc phc nht d c im n . Chiu di v chi 1

y nn dng bung h xon. Hnh 2-4 th hin hnh thc cc loi bung hu rng ca bung ly theo kinh nghim A = B = (3- 4).D , nhng

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hmin

m n 2530 m. Bung ny c m bng ki g dng 4 dn

n dng

c turbine 11 ine tm trc t

n ca b th ng knh tiu chu ca BXCT D1, kho (2,8 -3,5)D1 , chiu di bung khong (2,5 - 3)D1.

ti thiu ca np TB so vi mc nc nh nht trong bung: (0,9 -1)D1. II. 2. 2. Bung hnh ng

Loi ny thng dng vi ct nc H = 67l m loi cha cc b phn ca turbine (hnh 2-5): chp nn hn

c vo thun dng, cc cnh hng dng 1, BXCT t pha trong CCHD. Hnh ca bung ging mt ni xpde, na trc 5 ni vi ng p lc 7, na sau 2 ch a cm BXCT v ni vi on khuu cong 8 ca ng x 12. Tr trc 10 a ra ngoi bung v t nm ngang. Loi ny dng vi turb rc ngang, loi turbine nh. g knh ln nht ung ly eo

ng

. 2. 3. Bung xon c

y bo ine nh v m bo ch

t it din trn. ung xon l gc t din ca ra ( r v max).

Khi max = 34503600 th gi l gc bao hon ton (hnh 2-7,a), cn max < 3450 gi l

Hnh 2-5.Bung turbine hnh ng

II

Bung xon (hnh 2-6) l loi c s dng rng ri nht hin nay. Loi bung n m dn nc vo TB vi kch thc mt bng ca turb thy lc tt nht.Ph thuc vo ct nc bung xon c th lm bng b tng hoc kim loi. Bung btng ct thp c dng vi ct nc H 40 m, mt ct a gic. Khi H > 40 m hng dng bung xon kim loi hoc b tng ct thp t Phn loi b ty thuc vo gc bao max max ca bung xon , y c tnh t ti = 0) n tit din ca vo ca bung xon ( =

bung xon khng hon ton ( hnh 2-6,c ).

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rng gian my cho ) ph thuc vo quan h gia tit din ca o bung xon chn gc bao. Khi tit din ca vo chn, nu tng gc bao, mt

y i

n b

i nht . Kinh nghim cho thy, chiu rng gian my l nh nht khi bung xon c gc

ao m 0 m thnh

cao do lu lng tng i nh, nnc th ch n gc bao l n hn: t m x = 270 345 . Vi trm thu in ng dn v sau p chn bung xon gc bao ln s tin cho vic i tip gia ng ng p lc vi bu g xon.

Kt qu th nghim m hnh cho thy, tn tht nng lng trong turbine, vng b v CCHD ( khi chiuvmt s lm cho dng chy phn b u chu vi CCHD, bo m c dng chng trong turbine, nh n xon v hnh x ng li lm tng vn tc dng nc trong ph

nthnh dng chy xoy, kt qu lm tng t tht nng lng trong CCHD. Qua thnghim m hnh BXCT ch vi cc loi ung xon khc nhau ngi ta la chn loi bung xon l

b ax = 180 .V vy i vi TT c c t nc thp ( kiu lng sng ) gixy d 0 0ng TT nn chn gc bao 180 192 . i vi TT c ct nc trung bnh v

0 0 a

n n

Hnh 2-6. Bung xon

Khi ct nc H 80 m v gc bao max = 27003450 c th s dng bung xon tit din trn hoc ch T. Bung xon kim loi thng c gc bao max = 3450.

Hnh dng tit din vo bung xon: i vi turbine dc trc ct nc thp v va thng dng bung xon c tit din ch T hoc hnh thang, cn i vi TT ct nc cao 5080 m th tit din l hnh trn hoc ellipse. Hnh dng tit din bung xon cn ph thuc vo iu kin c th xy dng nh my ca TT. Trong iu kin gc bao nh nhau, bung c tit din hnh thang bo m kch thc mt bng ca gian t my nh nh rng b/a catit din cng l

t, cn tit din trn s ln nht v t s chiu cao trn chiun th mt bng gian my cng nh.

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T l gia chiu cao v chiu rng a tit din hnh ch T (hnh 2-7) nn chn theo c bng, kiu pht trin ln trn so vi

kt hp v nu ng c tip lc t ngay trn np turbin m khng b tr hm turbine. Cc gc v h iu kin thy lc

trong bung s km v kh b tng khong cch c t my. Kin ngh dng nh sau: = 20350 v thng ly 300. Ni chung, khi n n th = 1

khc kin ngh chn nh sau: khi m = 0 hoc n = 0, b/a = 1,51,85. Khi m v n 0 th

cu to ca bung xon, c th chn kiu trn

trc ca CCHD kiu pht trin xung di hoc kiu sn bng. Cc tr s m v n ch yu la theo yu cu b tr phn di nc ca nh my, n khng nh hng my n iu kin thy lc. Khi n = 0 (tc trn bng) hoc m > n th c th gim th tch khi b tng phn di nc ca nh my v d b tr ng c tip lc v c th rt ngn khong cch gia cc trc t my. Tit din ch T pht trin ln trn so vi trc CCHN ch nn dng khi pha di bung xon c b tr ng hm x nc ca TT x l

khng nn qu nh, v nu ly qu nh t tr ng c tip lc, nu qu ln th

trm th = 20350 cn khi m > 0200; khi n = 0, = 10150. Cc gi tr

b / a khng qu 22,2. Theo quan im thy lc th tit din ch T i xng hoc gn i xng c tt hn cht t.

Hnh 2-7. Cc ti n c T c ng xon b tng.

ta gi thit: l dng

t di h a bu Bung xon lm nhim v dn nc vo BXCT v hnh thnh c tnh ca dng chy trc mp vo CCHD. thit k bung xon ngi - Dng chy trong bung xon l dng chy dng, i xng qua trc quay v

th; lu lng qua tit din bt k Q ly theo gc i i l: i tt iQ Q=

; 0360 - Dng chy c coi l tng hp ca dng chy thng v dng xoy,

c trng bi

lu lng Q v lu s = 2 RV, gi thit khi thay i ch lm vic th Q v thay

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i sao nh phn vn tc hng

m Cr

cho cc ng dng trong bung xon khng i. Th

t phn b u theo chu tuyn trc mp vo cnh hng dng: Cr = tta

QD b 0 ;

(trong : Qtt l lu lng ca turbine, Da l ng knh ngoi ca cnh hng dng, b0 l chiu cao cnh hng dng). Vic tnh ton kch thc bung xon tin hnh trn c s turbine c chn, tm ra kch thc mt ct v quan h gia chng v gc. Hin nay c nhng phng php tnh ton sau:

* Phng php mmen tc vng l hng s Vu.r = K; Phng php ny dng hy c p dng i c i xng qua trc, dng c th v b qua tn tht dng chy. N

vi bung xon c gc bao max = 180 3600 , v nu gc nh hn th iu kin dng v ton

l hng s Vu = K; Phng php ny gi thit tc nhau. N cha lp lun khi

nh lp v n c nhng thiu st sau: + Dng chy tnh ton theo phng php ny khng hon ton ph hp thc t;

Tuy nhin qua nghin cu thy i v iu kin xo ng php ny ph hp hn ng php V g php n ho T c thp, b ng xon b tng gc bao nh giai on thit k .

* Ph ng php tc vng gim dn t ca vo Vu n ca ra t (0,60,8)Vu; Phng php ny c nh c im l tnh i xng ca dng chy b ph h i, nhng gim thc b xon. V ch dn ine ct n .

ng xon theo hai phng php u.

chy s khng cn i xng qua trc. Phng php ny kh chnh xc v thun hc nn c p dng rng ri;

* Phng php tc vng vng bnh qun cc mt ct ngang bung xon u nh

th + Gc bao cng ln th cng khng ph hp.

i gc bao khng V

vy phn

n th phy dng tt cph u.r = K.

T c ct n u v s b

o

nh kch ung vy n g vi turb c thp qu ln

Sau y chng ta nghin cu cch tnh bu

1. Tnh ton thu lc mt ct bung xon theo phng php Vu.r = K

Bc ny c thc hin sau khi chn gc bao max v hnh thc bung xon. Da vo nguyn tc nu ta i thnh lp cng thc chung:

l tc trung = k

Gi ttQ l lu lng ln nht qua mi turbine; bnh trong mt ct bung xon, xc nh theo: tbV

tbV H ( H = 2m th k = 1; H = 300m th k = 0,5) hoc theo th (hnh 2-9,a). i yu c hu vi c cu hng dng, v vy nu g l gc

no ng vi tit din cn tm th lu lng qua n l

V u lu lng phn b u c i i

i ttiQ Q= 0360 , din tch mt

ct tng ng l iitb

tt itb

FQV

QV

= = ..

360; tng t vi max ta c:

maxmax.F

QV

tttb

= 360

.

Nu ct mt di bt k c b rng dr, chiu ng b th din tch phn t dF = b.dr, vy:

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; v Vu.r = K nn Vu = K/r, vy ta c: i ura

Ri

ra

RiQ dQ V b dr= = . .

ira

Ri

ra

Ri ttiQ

Kr bdr K

br dr

Q= = = 360 ( 2-1 )

Hnh 2.8. S lp cng thc tnh ton bung xon.

Sau y ta p dng nhng cng thc trn tnh ton c th cho hai loi bung xon: t ct trn ( hoc ellipsse) v bung xon mt ct a gic.

rn (hoc ellipsse):

h 2-9,b), ngha l phi xc nh ra c quan h

m a. Tnh ton bung xon mt ct t

Ni dung ca vic tnh ton bung xon l v ra c ng bao xon v xc nh mt ct ngang ca bung xon (hngia gc i , bn knh Ri v din tch mt ct ngang tng ng Fi. T (2-1) t i

raS r

dr= , vy Qi = K.Si v K = Qi/Si, v K = hng nn K = Ri b

s maxmax

QS

ttGi bn knh mt ct ca vo (ng vi max ) l max = uV . .

Q . max360

,

y Coi l tit din trn nn i2 = ( bi/2 )2 + ( ri - a)2, rt ra bi v thay vo Si ta c Si v thavo (3-1) ta c gc :

ittQK = 720 . . ( )[ ] ( )[ ]

Trong

a a a a a a = 2 r r r c r r r2cng thc c = ( 720.K.) / Qtt = hng s. Gii phng trnh i ta c c :

ii r

= 2 a ic c

(2-2)

T (2-2) n nh ra ta s tm ra u bit c m i i . Da vo iu kin bin ca vo, c:

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c = ( )maxmax max a a ar r r 2 = hng s (2-3)

c hng s c ta nh ra cc gc i v lp bng tnh ( bng 2-2 ) sau: Bng 2-2. Bng tnh ton xc nh kch thc bung xon trn ( hoc ellipsse)

i 2

26

i ic

2 a ir c 2 a ir c

i i i aR r= 2

Cc bc tnh ton lp bng 2-2 nh sau:

- Chn gc bao max nh trnh by trn; - T bng 3 tra ra kch thc ng knh trong v ngoi ca vng b CCHD; - Xc nh mt ct bung xon ca vo Fmax nh ra max tnh ra hng s c theo (2-3) - nh ra cc gc i t 0 n max v tng ng tnh ra i theo (2-2) v xc nh Ri. quan h i ~ Ri v ra ng xon v t quan h i ~ Ri v mt ct ngang tng ng em (hnh 2-9,b).

Tx

Hnh 2-9. Tnh ton bung xon mt ct trn hoc ellipse.

b. Tnh ton bung xon mt ct a gic T lu lng ln nht ca vo bung xon Qmax v kinh nghim chn c chi tit kch thc ( m, n, bo , t s b/a, cc gc , ) tnh ra din tch mt ct ca vo Fmax v da vo tc trung bnh Vu nh ra mt ct ln nht. Cc mt ct khc coi nh xp chng t ln t Rmax n ra trn cc ng AC v EH ng vi cc Ri khc nhau

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(hnh 2-10). AC v EH c th quan nim theo ng thng hoc ng cong bc hai hoc ba.Thc t quan nim ng cong hp l hn. Sau y l cch tin hnh tnh ton:

Hnh 2-10. S tnh bung xon a gic.

T Qi = K.Si ta cn tm ira

RiS

br dr= . Ta c th dng phng php gii

xc nh Si l din tch ca b/r v r. Do vy trc tin ta cn phi v cc ng quan h r ~ b/r ( l cc ng mnab ca mt c ca vo, ng miniab ca mt ct th i, ..v.v... ) da theo tnh ton bng tnh 2-3. Cch tnh ton nh sau: - ng vi mt ct ca vo ABCHDE ta nh cc ri ( t Rv n rb ) v tng ng o c bi ri tnh ra bi/ri, dng ct r ~ b/r v ra cc ng mnab (hnh 2-10);

Hnh 2-9a

27

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- ng vi mt ct khc ta cng lm tng t v dng ct r ~ b/r v cc ng khc. o din tch gii hn gia cc ng va v v trc r ta s c c Si tng ng. Vi Smax ta tnh ra c hng s K = Qmax/Smax v tnh ra i theo cng thc: i

iSS

= maxmax

. (2-4)

Bng 2-3. Bng tnh ton bung xon a gic

r Rv R4 ... ...... ra rb Mt ct ABCHDE b bv b0 b0 b/r r R4 R3 ra rb M. ct A'B'CHD'E' b bi b0 b0 b/r bi/ri r Mt ct ...... b b/r

c quan h r ~ Q. ra c V = Q/F v v c r ~ V.

p bng tnh cc quan h ~ ~ R ( bng 2-4 ):

tin tnh ton xc nh cc mt ct bt k no ta tin hnh v th quan h ~ r, Q ~ r v V ~ r . Cch v cc ng ny nh sau: - Vi mi r ta c S v da vo (3-4) ta tnh c v v c quan h ~ r. - Vi mi c r v tnh ra Q = Qtt. / 360 v v - Vi tng r c Q v o c din tch F, tnh T cc ng ny ta d dng tra v v ng xon v mt ct bung xon.

2. Tnh ton bung xon theo phng php Vtb = K

Trong tnh ton bung xon theo quy lut Vu.r = K cho ta vn tc trung bnh ti cc tit din s khc nhau, iu ny dn n tn tht thu lc dc chiu di bung xon khc nhau nh vy tr s ct nc khc nhau, gy nn ti trng ln BXCT khng u lm mn trc v gy rung ng my. Ct nc cng thp th cng nh hng xu ny cng ln, do vy A.A Berrni a ra phng php tnh ny. Phng php s dng c p dng vi H < 40 m. Phng php Vtb = K coi tc dng nc qua cc mt ct bung xon khng i v bng Vtb c th ly theo biu (hnh 2-9,a).

a. Tnh ton vi bung xon mt ct trn ( hoc ellipsse)

Ni dung v cc bc tnh ton: - Chn gc bao ca bung xon, thng vi mt ct trn v ellipsse ly ln; - S b xc nh cc kch thc vng b v CCHD, c th ly theo cc bng 2-1 v cc bng 6-5, 6-6 chng VI. - L

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29

Bng 2-4. Bng tnh ton bung xon mt ct trn theo V = hng s

Mt ct a = ra + R = 2 + ra 1 2 3 4 5

Ca ra 0 0 ra ra . .

Ca vo max max ra + max R = 2max + ra

Ni dung v cc bc tnh ton:

Ct 1: ghi tn mt ct tng ng vi gc , t mt ct ca ra n mt ct ca vo; Ct 2: nh gc , ly t mt ct ca ra = 0 n mt ct ca vo max, ly cch nhau gi cc mt ct chng 450; Ct 3: Bn knh mt ct trn ( hoc bn knh nh ca ellipsse ) tnh theo cng thc:

maxmax =

ttu

QV360

(2-5)

itt i

uiQ

V

= =

..

.maxmax

maxmax360

(2-6)

Hnh 2-11. Tnh ton bung xon mt ct trn (ellipsse) v a gic.

Ct 4: Tnh i i aa r= Ct 5: Tnh ra bn knh i i aR r= 2 T s liu hai ct 2 v 5 v c ng xon. T s liu ct 4 v 5 v c kch thc cc mt ct ngang ca tng tit din (hnh 2-11,a).

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30

b. Tnh ton bung xon a gic Vic tnh ton bung xon mt ct a gic theo phng php Vtb = K tin hnh

cc bc (xem hnh 2-11,b) di y: - Chn gc bao max v hnh thc mt ct nh trnh by cc phn trc; - Tra cc bng 2-1, 6-5 v 6-6 xc nh cc kch thc b0, Da, D ;

- Da vo Qtt v Vtb tra ra tit din mt ct ca vo bung TB:

b

maxmax.

.FQ

Vtt

tb= 360

,

c Fmax da knh nghim chn cc kch thc: b/a, , sao cho din tch mt ct ca vo ng bng din tch Fmax; - Lp bng tnh ton (bng 2-5) xc nh quan h R ~ F ~ : Ct 1: t tn cho cc mt ct bung xon: t mt ct ca vo n mt ct ca ra; Ct 2: Chn quy lut thay i ng t ca cc mt ct l ng thng hoc parboll, nh cc bn knh R t bn knh ca vo Rmax n bn knh ca ra rb; Ct 3: o din tch mt ct Fi tng ng vi Ri ( phn gch cho ) v ghi vo ct 3;

Bng 2-5. B = hng s ng tnh bung xon a gic theo V

Tn mt ct Ri Fi i 1 2 3 4

Ca vo maxR maxF max . . . . . . . .

Ca ra br 0 0

Ct 4: T cng thc tnh din tch mt ct c vo v mt ct th i Fi : maxF

maxmax.

.V tb

Qtt= F 360i

tt itb

lp t l Fi/Fmax ta c F V=

.360Q . ( )i iF F if R

= =mamax

x (2-7),

l quan h ng thng, do vy c Fi tnh ra tng ng i , ghi vo ct 4. n s a v ng ra ng quan h

) v vo h R o b F ~ m nga a xo

ti ng quan

d ta ~

d vo b 7

ng x v c

n cac F ~

a vo q ~ R (hnh 2-

uan h11,b da ung, d ~R v t ct ng c bung n.

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31

II. 3. T

Thi t) l b phn khng th thiu turbine vi tn tht nng lng n - S dng ng chy sau khi ra khi BXCT;

c tnh Hs (gi l chn khng tnh) tnh t mt ct ca ra BXCT

HIT B THO NC CA TURBINE THU LC

t b tho nc (ng x hay cn gi l ng h phn kch. N c nhim v tho nc t BXCT xung h luh nht. Ngoi ra ng x trong turbine phn kch c nhng tc dng sau y:

thm phn ln ng nng cn li ca d - Tn dng thm ct n

n mc nc h lu hm x nc. xc nh gi tr v ngha ca ng x ta vit phng trnh nng lng cho 3 trng hp: khng c ng x, ng x tr trn v ng x hnh nn ct (hnh 2-12) ri so snh .

Hnh 2-12. Cc s tnh ton so snh vai tr ng x.

Vit phng trnh Becnuly cho tr hp a) khng c ng x cho hai mt ct mt thong 1-1 v mt ct ca ra BXCT 3-3, ly mc nc knh tho 0-0 lm chun nu b qua tn tht ct nc trong bung h v v p lc mt thong 1-1 v 3-3 u bng p sut kh tri p1 = p3 = pat , vn tc c chy trn mt thong 1-1 coi nh bng khng V1= 0, vy ct nc c th s dng c l Ha:

ng

n

a o oH E Ep

Zp V

g Z Z ZVg

= = = 1 3 1 3 3 32

3 33 3

2

2 2

( )

Vit phng trnh Becnuli cho trng hp c) c ng ht cho hai mt ct 1-1 v mt ct ca ra ng x 5-5, c tnh n tn tht ct nc h3-5 ca ng x, ta c ct nc m turbine c th s dng c l Hc:

c oat

oH E Ep

Z Zp Z V

h ZVg h

= =

= 1 5 1 5 5 5 5

23 5

5 52

3 52

Ly Hc tr cho Ha ta c c ct nc t ng thm H do c lp thm ng x so vi trng hp khng lp ng x:

H H H Z V Vg hc a= = 3 3 3

2 5 52

3 52

(2-8)

Trong ch s 3 tng ng vi c ng x (hay ly gn ng l ca ra BXC thu i do 3

i, gi l chn khng

a vo T), ch s 5 tng ng ca ra ca ng x. T cng thc H ta thy: nng lng ng x gm: thnh th nht l thm ct nc tnh Z k hiu l Hs gi l h

chn khng tnh , thnh phn th hai bao gm hai phn cn l

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32

ng. Thnh phn th nht c lin quan n thit k cng trnh, c th l vic chn cao trnh t turbine, thnh phn th hai gn lin vi cu to ca ng x. Hiu sut ng x c biu th qua hiu qu thu hi ng nng ca ra BXCT sau:

oxV V

gh

Vg

=

0 th gim p sut tng ng

s l 9

00, mt khc tng tnh an ton ta nhn thm vo H mt lng ( +)H, ta

c:

HS [ HS] = 10 - 900 - ( +)H (3-4)

hoc: HS [ HS] = 10 - 900 - k H (3-5) tra theo biu (hnh 3-2);

s k ly k = 1,05 - 1,1. H

Hnh 3-2. Quan h = f(H). III. 4. XC NH CAO TRNH T TURBINE trn trnh by nguyn nhn v iu kin xy ra hin tng kh thc. Mt

nh

khng xy ra xm thc ch thit k. i vi mi loi turbine th chiu cao ht S c

c nc lu (hnh 3-3,a), cn cao trnh e lm ly cao trnh qua gi

Tu

trong nhng iu kin khng pht sinh kh thc trong turbine l cao trnh t turbine phi m bo HS [ HS]. Tuy nhin vic chn im x l im gi thit c p lc nh nht thng khng th xc nh chnh xc c, nn thng quy v tr ca n l ni c th xy ra p sut nh nht v ti c tnh n mt i lng d tr an ton

nc quy c H ng khc nhau (hnh 3-3) nh sau: - Turbine hng trc v hng cho trc ng th HS ly t tm trc cnh n mc nc h lu (hnh 3-3,c), cn cao trnh t turbine lm ly cao trnh qua gia CCHD; - Tu e t ly t mp di cnh hngrbin tm rc trc ng th HS dng n m

t turbin a CCHD; h - rbine trc ngang, HS l khong cch t im cao nht ca ng ht ti mc nc h lu (hnh 3-3,b), cn cao trnh t turbine lm ly cao trnh qua tim trc turbine.

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Hnh 3-3. Quy nh chiu cao ht nc v cao trnh t turbine.

a h t turbine (lm nh trn, c lin quan n cao ht nc HS phi ly nh hn cao

ht cho php [ HS] theo cng thc (3-4) hoc (3-5). Nh vy cao trnh lm t cng su v kh thc, tuy nhin khi lng phn di nc ca nh my s cng

ln. V vy chn lm sao cho va an ton v kh thc va m bo khi lng cng nh.

h lp turbine c tnh cho cc loi turbine nh sau: - i i turbine t ng (hnh 3-3,a):

C o trn ) c quy nhht nc; khng pht sinh kh thc th cao

cng an ton

tr Cao trn v m trc trc

40

lm hl soZ H

b = + + 2 (3-6) - i vi turbine hng trc trc ng (hnh 3-3,c):

lm hl sZ H x D = + + 1 (3-7) 10,46

i turbine trc Vi x = 0,4 - i v ngang (hnh 3-3,b):

2

DHZ 1shllm += (3-8) Trong cc cng thc trn, khi ct nc H v lu lng Q pht in thay i th

mc nc h lu Zhl v cao ht nc HS cng thay i. Trong thc t da vo iu kin thit k chn cao trnh t my: Dng ct nc thit k (HTK) tnh ra [HS], ng rbine tnh mc nc h lu Z , cao trnh thc th dng lu lng ca mt tu hl

cht l cao trnh t turbine ta cha bit, tuy vy do t s

900ng k do vy c th ly ng chng cao trnh d nh t turbine (thng c th ly ng cao trnh mc nc thp h lu).

tr s lm , sau v ng tn sut lm ~ p%, da vo tn sut thit k ca trm tra ra lm ri phn tch chn kt qu tho .

qu b, sai s khng

b

tnh cao trnh t my ng hn, c th cho cc H, Q thay i ri tnh ra cc

c ng

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41

N L CNG TC V LUT TNG T CA TURBINE TH LC

IV. 1. DNG CHY TRONG TURBINE THU LC

ng lng trong BXCT ca turbine thu lc trc ht tm h chy trong BXCT rt hc tp, ng cong khng ian li v a chy vng quan

bine. t c cc p ng trong vng BXCT u tun theo hai chuyn ng:

huyn

Chng IV. NGUY

xt qu trnh bin i nta iu dng chy trong . Qu trnh chuyn ng ca dng

cc phn t cht lng va chy men theo b mt cnh dp g h trc quay ca turbine, l chuyn ng khng gian ba

chiu. S thay i lu tc c hng ln tr s s lm thay i cc thng s ca turbine nh lu lng, vng quay, hiu sut ...v.v.. ca tur T hn t cht lc ng tng i theo bin dng cnh v chuyn ng theo vn tc quay ca bnh xe. Nh vy chuyn ng tuyt i ca phn t cht lng l tng vect vn tc ca hai

chuyn ng (hnh 4-1). Gi U

l vn tc theo, W

l vn tc tng i, th vn tc

tuyt i V

s c xc nh theo cng thc: V

= U

+ W

. Ba vect ny to thnh tam gic khp kn gi l "tam gic tc ". Tam gic tc ca vo (im 1) v tam gic

Hnh 4-1. S dng chy trong BXCT ca cc turbine. tc ca ra (im 2) ca bnh xe cng tc c trnh by trn (hnh 4-1,b, d). Cc gc to thnh tam c c tng ng ni trn gm: l gc to thnh bi vn tc tuyt i V

vi vn tc theo U

, cn l gc to thnh bi vn tc

gi t

tng i vi

vn tc th .Cc gc , thuc vo cu to v hnh dng cnh. Dng nc tro hy

dc theo thnh cnh, do vect vn tc tng i ca dng nc s hng theo trc ng i W s t l nghch

ng vn t

W

eo U

1 2 tung cc khe gia cc cnh ca turbine tm trc (hnh 4-1,a) c

cc khe ny. Nu chiu cao cc khe khng i th vn tc tvi chiu rng ca khe. V trong turbine tm trc khong khng gian gia CCHD v BXCT b nn ni chung c th cho vn tc tuyt i ca ra CCHD b c tuyt

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42

1), nu y s

vy trong vn hnh c gng bo m iu kin ny. Trong turbine hng trc (hnh 4-1,c), ngoi nhng iu rt ra c turbine

tm trc, cn c nhng c im sau: - Chuyn ng

B phn CCHD nm cch xa BXCT, nn khong khng gian gia chng tng i n do v vect vn tc tuyt i mp ra cnh hng dng V0 khng th bng vn tc

y iu kin "chy vo khng va"

tc c v v ca

t dng nguyn t ca dng chy trong turbine ch lm vic n nh. T suy ra chung cho ton dng chy trong hm vi BXCT vi cc gi thit

- BXCT c s lng cnh nhiu v hn, cnh cc mng. Nh vy khe h gia cc p, lc qu o chuyn ng tng i ca cht lng trng

- Dng chy trong turbine l dng n nh. Nh vy th ng dng s trng vi qu o chuy g ca ch n it ny cho php c v tr v hnh dng

ca ng dng trong turbine; - Dn c ng l tng, do vy khng tnh n tn tht thu lc. X T. Ly h trc totc tuy R U Z

n tc vng c g gy men hai thnh men quay v y ta ch s c vng

thi

ng (hnh 4-1,e). Khi chy men theo b m , vn tc hng ngng i c hng v tr s, v vy cc ht cht l ng ca cnh BXCT. Theo nh lut ba ca Niu tn th cc ht cht l

o c h . Nu x

i ca vo BXCT (V0 = V vn tc tng i mp vo W1 trng vi tip tuyn ca mp vo BXCT th dng ch rt thun khi chy ln bao prfin cnh v l chy vo khng va" ca vo. V"

dng chy trong BXCT c hng song song vi trc quay; - l ytuyt i ti mp vo bnh xe cng tc V1 c. Do vkhng bo m i vi turbine cnh qut khi lm vic khc vi ch thit k, turbine cnh quay do cnh xoay c do khc phc c c im ny. ca ra ca BXCT cn lm sao cho dng chy t ca ra vo ng x cn c gn gim tn tht xoy n mc thp nht tng hiu sut ca turbine. IV. 2. PHNG TRNH C BN CA TURBINE Phng trnh c bn ca turbine thu lc xc lp quan h gia mmen lc tc dng ca dng nc vo BXCT v cc thnh phn vn a o ra ca n. Nh trn thy dng nc chy trong BXCT l dng khng gian ba chiu phc tp, do vy n gin khi lp phng trnh ny, ta xt m

p sau:

cnh k tip nhau s rt hvi tuyn AB ca cnh (hnh 4-1,e);

n n t l g. Gi th ta tm

g hy qua turbine l dt chuyn ng ca dng nguyn t tch ra t dng chy trong BXC

(r, u, z) theo phng hng tm, hng vng v hng ng, phn tch vn t i V theo h trc trn ta c c thnh phn vn tc tng ng V , V v V ,

trong ch c thnh phn v kh nn m quay, cnphn vn tc kia khng gy m i trc Z.Do v dng vn t

t lp mmen quay cho BXCT, v ta c th chuyn nghin cu bi ton khng gian v bi ton phng bng cch chiu vn tc tuyt i V ra cc thnh phn U v W trn cc mt phng t ng ti cc im dng nguyn t

t cnh dng chy kng chu tc dng cng c tc dng tr li cnh mt lc cng tr s nhng c chiu ngc li,

chnh lc to nn mmen xon ln trc turbine. p dng lut bin thin mmen ng lng lp quan h trn. Theo lut ny, o hm mmen ng lng vi thi gian ca c h bng mmen ca tt c cc ngoi lc tc dng v

t dng nguyn t di chuyn t ca vo 1 n ca ra 2 sau thi gian dt th:

dLdt dt L L Mc

= =1 2 1( ) (4-1) trong : L1 , L2 l mmen ng lng tng ng ca dng nc u v cu dt; Mc l mmen cc ngoi lc tc dng ln dng nguyn t ang xt.

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Ti ca vo 1 cch trc turbine bn knh r1 dng nguyn t c vn tc tuyt i V1 v cc thnh phn vn tc theo U1, vn tc tng i W1, ti ca ra 2 cch trc turbine bn knh r 2 c vn tc tuyt i V2 v cc thnh phn vn tc tng ng l U2 v W2. Gi lu lng nc qua 1 hoc 2 trong n v thi gian l q, b qua tn tht

43

. . . . .cos

dung tch khi chuyn t 1 n 2 th khi lng nc ti hai im u l m = . .q dt Tng ng ta c mmen ng lng ti ca vo v ca ra BXCT l:

1 1 1 1L m V r= =. . .cos 1 1 1q dt V r 2 2 2 2 2 2 2L m V r q dt V r= =. . .cos . . . . .cos

Thay gi tr L1 v L2 vo (4-1) ta c: dL q r V r V Mc= = ( cos cos2 2 2 1 1 1 (*) Trong cng thc (*), Mc l mmen ca cnh turbine tc dng ln cht im nc, vy nu gi Mn l mmen ca cht im nc tc dng ln cnh turbine th Mn = - Mc, vy q r V r V M( cos cos n= (**) 1 1 1 2 2 2Phng trnh (**) lp cho mt dng nguyn t chy trong BXCT, dng chy trong ton BXCT ta thay Q =

m rng cho ton q v M = nM v nhn hai v ca (**) vi

vn tc gc ta c: Q V r V r M( . . .cos . . .cos ) .1 1 1 2 2 2 = ; Mt khc, ta bit 1 1r U. = ; 2 2r U. = ; v M. = N = g Q H. . . T rt ra: H V U V U= 1 ( cos cos )g 1 1 1 2 2 2 (4-2)

Phng trnh (4-2) va lp trn cho turbine c s cnh v hn, cnh v cng mng v cht lng l tng. Thc t turbine c s cnh hu hn, c b dy v cht lng

lc trong BXCT v ct nc thc t Hth ch cn bng H, vi l hiu s t thu c (H = H - . Vy (4-2) vit li l: thc, do vy c tn tht thu

u l th H = H) H g V U V U=

1( cos1 1 1 2 2 2cos ) . T y rt ra phng trnh c bn

dng khc, dng cho turbine thc t:

=

V-1), theo phng trnh (4-3) th hiu sut ln nht ca BXCT c c khi V U cos = 0. V ct nc ang xt khng

c U2, c l iu kin chy ra thng gc hay iu kin "php tuyn ca ra". Tuy nhin qua

hiu th nghim chng t rng thc t nn chn 2 < 900 mt t tch s 2U2cos2 = 0,2gH th hiu sut turbine cao hn, v khi 2 < 900 th dng chy sau khi khi BXCT c xoy mt t to iu kin chy trong BXCT v trong ng x tt hn.

- Ap dng phng trnh (4-3) vit cho turbine xung kch go (hnh 4-1,d): c t vi phun bn vo cnh go theo cc tia trn, sau khi ra khi vi phun, ton b ng lng dng tia tr tn tht u bin thnh ng nng vi vn tc

11 1 1 2 2 2g H V U V U

( cos cos ) (4-3)

h g (4 vin s E P n trnh -3) do ule lp ra nm 1754, c gi l phng trnh c bn ca turbine. Phng trnh ny vit chung cho c turbine phn kch v xung kch. - nng cao hiu sut ca turbine ngoi vic c gng m bo vn hnh turbine iu kin "chy vo khng va" (nh trnh by I

2 2 2

i, vn tc V2, U2 khng th bng khng do vy ch c th cos2 = 0 hay 2 = 900. h vy iu kin chy ra li nht l vc t vn tc VN 2 thng gc vi vc t vn t

tnVra Nn 0 2V gH= , khi n go, tia nc c tch ra hai phn bng nhau v chy vo hai na go dng

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44

cong ellip n c theo gn nh ngc chiu vi . Nu b qua tn th a nc v

hong gn nh nhau, do

sse, dng nc ri khi cnh go vi vn tc tuyt i 2V rt nh, cn vt 2 2go th 1W = 2W . im vo (1) v im ra (2) cch trc mt k

W V t ma st gi

vy m 1 2U U U= = . Da vo tam gic tc ca vo v ca, thnh trong (4-3) s l: 1 1 1 1V U V Ucos = ; (*) 2 2 2 2 2 2 1 2V U W U W U V Ucos cos cos ( ) cos = + = + = + (**) Thay (*) v (**) vo (4-3) ta c phng trnh c bn (4-4) ca turbine xung kch go:

= 1 11 2gH U V U( ) ( cos ) (4-4) T phng trnh (4-4 thy rng tng hiu sut turbine go, khi H bit th: Tch U(V1 - U) phi ln nht, do vy ta o hm tch ny theo U v cho bng 0, ta c: U = 0,5 V1, ngha l tc vng phi bng mt na tc tuyt i ca dng phun. Nhng iu ny khng t c v c tn tht, thc t U = (0,43 - 0,47) V1. Tch (1- cos 2 ) ln nht, mun vy gc 2 0180 = . Nhng v nu 2 0180 = th phng ca 2W trng vi phng , nh c cnh sau s c

I LNG QUY DN

n cy

u cu , ngi ta thu nh kch thc turbine m

qua cc quan h tng t vi turbine m bo

trn m hnh p dng cho turbine thc t cn phi c hng

2U vy dng n p ngpha sau cnh trc lm gim mmen quay ca BXCT, do vy ly 002 177176 = .

IV. 3. LUT TNG T CA TURBINE V CC CA TURBINE

Cng tc thc nghim m hnh v hin trng c tc dng b sung ti

cho kt qu nghin cu thit k turbine cng nh cc thit b, cng trnh khc. Nh thc nghim khc phc bt nhng khim khuyt do cha lng trc hoc do cha th cp c ht nhng yu t thc t. Vi ycn ch to thnh turbine tng t, gi l turbine m hnh. Tin hnh th nghimhnh v v ra cc ng c tnh turbine, t thng

m hnh phc v cho vic nghin cu, thit k, ch to turbine mi. tin cy gia kt qu nghin cun iu kin v cc tiu chun tng t. IV. 3. 1. Cc iu kin tng t Hai turbine hoc my thu lc c gi l tng t khi chng tho mn ba iu kin tng t l: tng t v hnh hc, tng t v ng hc v tng t v ng lc hc

1. iu kin tng t v hnh hc Nu ta k hiu nhng thng s ca turbine m hnh bng cch ghi vo thm ch

s (M), cn thng s ca turbine thc cn ch to bng ch s (T) th iu kin tng t v hnh hc l cc kch thc hnh hc tng ng gia chng phi theo mt t l:

1M1

2M2

00TD D b

constT T

M= = = = (4-5) Tp h

D D b

p cc turbine ng dng v hnh hc c gi l cc turbine cng kiu. 2. iu kin tng t v ng hc ai turbine tng t v ng hc l s phn b vn tc ti cc im

gia cc vn tc tng ng phi bng nhau, tam gic tc phi ng dng:

iu kin htng ng trn dng chy ca hai turbine cng kiu phi tng t, ngha l t l

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45

MT

MT

MT

VV

UU

WW

= = (4-6) v cc gc kp gia cc thnh phn vn tc tng ng phi bng nhau. 3. iu kin tng t v ng lc hc iu kin hai turbine tng t v ng lc hc l cc lc ( trng lc, lc nht, c qun tnh ...) tc dng ln cc phn t tng ng ca dng chy phi t l. Trong l l

thuyt tng t ngi ta thng dng cc chun s: Ry nn (Re = V l. ), Frt (Fr =

2Vg l. ), Struchan (Sh =

Vn l.

) v le (Eu = pV. 2 ) lm cc iu kin tng t.

iu kin tng t ng lc hc l: ReM = ReT, FrM = FrT, ShM = ShT, EuM = EuT, trong yu cu ti thiu c coi la ng dng ng lc hc l hai chun s:

ReM = ReT, FrM = FrT (4-7)

Hai turbine nu c chun s Re bng nhau s m bo tmng t v lc nht v lc qun tnh, nu chun s Fr bng nhau s m bo tng t v trng lc v lc qun

nh, cn chun Eu l k

iu ki ch m

3. 2. Cc quan h ca hai turbine tng t i vi cc turbine tng t, trc tin ta

i

tnh, chun s Sh bng nhau s bo m tng t v lc qun tu ca hai dng chy m bo tng t v Re, Fr.

t q

Trong thc t th nghim my thu lc cho thy khng th no m bo c n tng t ng lc hc c, v rng cc turbine khc nhau v kch thc s

kh m bo t l nhm do trnh gia cng ... V vy ngi ta c xu hngbo theo ng mt trong hai chun s Raynon hoc Frt, vic chn chun no tu thuc lc no c tc dng ch yu m quyt nh, v d dng chy c p trong ng v trong turbine phn kch th tnh nht c tnh quyt nh do vy cn phi m bo chun s Re.

IV. thnh lp cc cng thc tng t xc nh quan h tng quan gia cc vn tc dng chy theo cc gc 1 2 1 2 , , , v ct nc ca turbine ti ca vo v ca ra BXCT. Gi thit rng dng chy ra khBXCT theo hng php tuyn, ngha l phng trnh c bn c dng tlgH U V= 1 1 1cos . Mt khc theo tam gic tc v lng gic ta c: 1 1 1

W U V

1 1 1sin sin ( ) sin = = 1

do vy: 11 1V

U=1 1

sinsin ( )

v: 1

1 1WU=

1 1

sinsin ( )

; do vy ta c:

tlgH U V= 1 1 1cos = 2 1 1 1

1 1

U

sin cossin ( )

T y rt ra:

11 1

1 122 2U g H K g Htl u tl=

=sin ( )cos sin

(4-8)

tng t ta cng rt ra c cc tc sau:

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11

1 1 122 2V g H K g Htl v tl= =

sincos sin ( )

(4-9)

12 1 1 1

1 12

1 122g H Ktl W =sin cos sin ( ) 2W g Htl=

sin sin ( ) , (4-10) Cc h s u v wK K K, , ph thuc vo gc ca tam gic tc v t s D2 / D1. Nu hai turbine tng t th cc h s ny khng thay i ( iu kin tng t v hnh hc v ng lc hc). Vy ta ta c th suy ra cc cng thc biu th quan h ca cc thng s chnh ca turbine m hnh v turbine thc cn ch to Chng ta cng nhn thy i vi turbine cng kiu lm vic vi ch cng gc th 1 v 1 ca vo bng nhau. Do vy cc h s tc ca vo s bng nhau v vn tc tng ng bng nhau. 1. Quan h v vng quay Vn tc vng cu hai turbine m hnh v thc c xc nh t cng thc (4-8):

M uM M tlMMU K g H

D n= =2 601M .

T uT T tlTT TU K g H

D n= =2601 . .

ch lm vic cng gc th uM uTK K= , v vy nu lp t s cho hai vn

tc trn ta c: MT

T M tlM

T

nn

D H

D H= 1

1M

(4tlT

-11)

2. Quan h v lu lng c ch

Lu lng n y qua BXCT t l vi tit din t (F) ca BXCT v vn tc

u sut dung tch (q). Vy vit cng thc tnh lu lng tng i (W) v c k n hicho hai turbine m hnh v turbine thc s l:

qM M MK g H.2M M WM tlM 1MQ F W F. . . . .= = qT T T T T WT T tlTQ F W F K g H . . . . .= =1 2

i vi turbine cng kiu th t s tit din F t l vi bnh phng ng knh, ngha

l 1M1

1M2

12

FF

DDT T

= , lp t s lu lng ta c:

MQ D H=

2

T T T qM tkTQ D H12 (4-12)

3. Quan h v cng sut Cng sut ca turbine m hnh v thc c tnh nh sau: M M M M

M qT tlM1M

N Q H= 9 81, T T T TN Q H= 9 81, lp t s gia hai cng sut v thay t s lu lng

eo cng thc (4-12) ta c quan h v cng sut:

th

MT

M M M qM tlM

T T T T qT tlT

NN D H H

= 1M12 (4-13)

D H H2

46

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47

cng thc tng t ca turbine thu hnh bit, dng cc cng thc

Cc cng thc (4-11) n (4-13) ch quan h gia cc thng s cng tc i vi ch tng t ( ch ng gc) gi l nhng

c thng s turbine mlc. Qua th nghim m hnh cng tt trn tnh ra cc thng s tng ng ca turbine thc m ta cn tm. Trong

thc t tnh ton thit k ta chn turbine bc ban u thng tnh gn ng, b qua s sai khc nhau v hiu sut gia turbine m hnh v turbine thc v t l kch thc vi ng knh D1 . Ta c cc quan h gn ng ln th nht sau:

M T Mn D H1T Tn D H=

1M (4-14)

MT

M

T T

QQ

D HD H

= 1M2

12 (4-15)

M M MN D H H1M2 T T T TN D H H=

12 (4-16)

IV. 3. 3. Cc i lng quy dn Trong thit k turbine cc thng s ca turbine (H, Q, n, N) khng th c trng cho cc turbine cng loi tng t nhau. c trng cho cng mt loi turbine ngi ta a

cng sut ca mt

( thng l nh hn 1m), vi ct nc lm vic no v o ra cc cc vng quay , lu lng ... Dng cc cng thc tng t trn tnh i ra cc i lng quy dn t cc s liu th nghim: Gi turbine m hnh l turbine c ng knh = 1m, ct nc = 1m theo nh ngha th = = , v b cc ch s (T) trong cc cng thc (4-14, 4-15, 4-16) ca cc i lng ch turbine thc, vy cc cng thc quy dn l:

ra cc i lng mang tnh c l gi l i lng quy dn ( hay i lng dn xut). Cc i lng quy dn ca turbine l: vng quay, lu lng vturbine c ng knh tiu chun D1 = 1m, lm vic vi ct nc H = 1m. c cc i lng quy dn, ta th nghim vi turbine m hnh c ng knh tu MD MH

Mn MQ

MD MH

Mn 1'n , MQ 1'Q

11'n

n DH

= (4-17)

11D H

2'Q = (4-18) Q

1 1 129 81' ',N Q H H D= (4-19)

Nh vy cc turbine tng t nhau th c cng mt i lng quy dn. Trong thit k turbin knh ,

d 1M 1D m=e, nu chn c mt m hnh no c ng

M m= 1 v cc i lng quy n 1 1 1, ,n Q N th ta c th xc nh cc thng s ca turbine cn thit k theo cc cng thc sau:

' ' 'H

Q Q D= 1 1

H 2'

nn

DH= 1

1

'

(4-20)

N N D H H Q D= =2 29 81' ', H H1 1 1 1

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c kiu BXCT khc hau, tuay

thnh lp cng thc tnh vng quay c trng, ta s dng cc cng thc tng t (4-16) v (4-14). Nu gi turbine m hnh c , ,

IV. 3. 4. S vng quay c trng ( h s t tc) biu th mt cch tng hp cc c tnh thu lc ca turbine theo s vng quay, k so snh cc h turbine vi ch nng tho nc, ng ti

rong ngnh ch to my thu ln c thng s dng i lng vt l gi l vng q c trng hay h s t tc, k hiu nS. V thc cht h s t tc l s vng quay trong mt pht ca mt turbine c kch thc sao cho khi lm vic vi ct nc 1m c th pht ra cng sut bng mt m lc (hoc 736 W).

M Sn n= MH m= 1MN = 1 mlc, v c cc i lng ... Cc i lng ca turbine thc trong cc

cng thc b ch s (T). T cng thc (4-16)vit li theo quy c trn ta c:

MD

M M MNN

D H HD H H

= 1M2

12 , thay MH m= 1 v MN = 1 ta c

1 1 11M2

12N

DD H H

= ;

rt ra: 11M

DD

NH H

= (*) T cng thc (4-14) vit li theo quy c ta c:

MT

T M

T

nn

D HD H

= 11M

, thay M Sn n= v MH m= 1 , ta c: SnnD

D H= 1

1M

1, rt

ra:

SM

n nD

D H= 1

1 thay (*) vo ta c:

Snn NH H

= 4 (4-21) Trong cng thc (4-21): n (v/ph), H (m), N (mlc), nS (v/ph). Nu thay th

nguyn ca N l (kW) th Snn NH H

= 1167 4, , (v/ph) (4-22) Ta cn c ng cng

c (4 (4-20), ta c: th tnh h s t tc theo cc thng s quy dn v tng t; d

th -22), vi n tnh theo cng thc

Snn H

D H HQ D H H= 1167 9 811

1 41 1

2, ,'

' = 3,65 1 1' 'n Q (4-23) Q'1 tnh theo m3/s. S vng quay c trng nS(hay h s t tc) l h s tng hp v n cha ng

cc thng s chnh ca turbine (H, Q, N, n) v n c thnh lp t cc i lng ca turbine m hnh theo cc cng thc ng dng

hc ca turb, n khng i i vi mt kiu turbine, ine.

ng knh v cc thng s H, Q, N. V vy ngi ta cn dng t tc nS vic trong vic

nhng n khng phi l vng quay tMi kiu turbine do phm vi lm vic ca ct p v cng sut khc nhau th nS

cng khc. Turbine hng trc c H thp, N ln mc du s vng quay thc t nh nhng lu lng ln nn nS cng ln ( nS = 500950 v/ph); turbine go lm vic vi H cao, N tng i nh, Q nh nn h s t tc cng nh (nS = 570 v/ph) ...

Cc turbine tng t th c chung mt vng quay c trng khng ph thuc vo

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cc turbine theo t ch .

hng

IV. 3. 4. Tnh ton hiu sut turbine thc t turbine m hnh Trong thc t tuy hai turbine tng t cng lm vic ch tng t nhng

hiu sut ca chng v knh BXCT. S d s khc nhau ny v trong cng thc chng ta tnh gn ng b qua cc t s hiu

a hai turbine tng t do tnh phc

thng phi dng n cc cng .

phn loi turbine. Lu l rng khi ch lm vic ca turbine thay i, ng vi mi tr s ct nc cho trc th h s t tc cng thay i, bi vy so snhiu t kin chng lm vic cng mk tc ch c th tin hnh trong iu

T h s t tc c tnh ng vi turbine c cng sut nh mc, ct nc tnh ton v s vng quay ng b. T cc cng thc t tc trn ta thy: nu hai turbine c cng ng knh BXCT D1 v cng ct nc H th turbine no c t tc ln hn s cho cng sut v vng quay ln hn. Do vy nu dng turbine c t tc ln ng vi cng sut cho trc s cho php gim D1 v s vng quay ln. Do xu th pht trin ca ngnh ch to turbine l tm cch tng t tc ca turbine gim nh kch thc turbine v kch thc my pht.

n khc nhau. ph thuc vo ct nc v ngcsut, do vy b qua s khc nhau v tn tht gitp v cng cha c cch tnh chnh xc cc tn tht ny.

Trong thc t xc nh hiu sut ca turbine thc thc kinh nghim v cng ch mi da vo ch lm vic ti u ca turbine m hnh Cng thc kinh nghim xc nh hiu sut ton phn ca turbine thc nh sau : Khi ct nc H 150 m:

max max( )T MT

DD

= 1 1 1M1

5 (4-24)

Khi ct nc H > 150 m:

max max( )T MT

MT

DD

HH

=

1 1 1M1

5 20 (4-25)

i vi turbine khi th nghim m hnh ta xc nh c hiu sut thu lc vi mi tr s ct nc th c th xc nh hiu sut turbine thc tng ng theo cng thc sau:

iT iMeMeT

RR

= bine,

kh tn

+ 1 1 1

6( ) ( ) (4-26)

Trong (4-26) l s phn trm hiu sut, n ph thuc vo ch lm vic ca turh ra c, ngi ta chn gn ng theo iu kin lm vic ti u ca turbine l

= 0,5 v dng chung cho mi ch lm vic. Cn eMeT T

M

T

RR

DD

HH

= 1M1

.

Trong tnh ton hiu chnh hiu sut turbine thc t m hnh ngi ta thng s dng cc cng thc (4-24) v (4-25) tnh, vi chnh xc gn ng cho php.

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Chng V. TH NGHIM M HNH V C TNH TURBINE

50

T L V H THNG TH NGHIM Hin nay nhng phng php tnh ton l thuyt vn cha xc nh hnh dng tt nht ca cc b phn qua nc ca turbine (BXCT, CCHD, vng b, bung turbine, ng x ....) phn ln cc ch lm vic. c bit kh, hoc khng th, xc nh c cc tnh cht nng lng v kh thc cu turbine ch lm vic khc vi ch thit k nu ch da vo l thuyt. V vy, thit k cc turbine hin i thng ngi ta a ra mt s phng n phn qua nc v tnh ton chng theo cc cng thc l thuyt. Theo kt qu tnh ton, ch to ra cc m hnh ca phn qua nc ca turbine ri em th nghim phng th nghim, t kt qu th nghim v thng qua lut tng t tnh ton chnh l thnh cc ng c tnh m hnh, t xy dng thnh cc ng c tnh khc ca turbine thc t. Vic th nghim cng c th tin hnh trc tip qua nhng turbine ang hot ng cc TT nhng tn km v khng iu kin bng trong phng th nghim. Vic th nghim tin hnh trong mi trng nc do vy ch yu cn m bba iu kin tng t v chun s Raynon. xc nh cc c tnh nng lng v kh thc ca turbin thng th nghim bao gm nhng b phn chnh sau:

c qua p trn xung b di v c m l

chn

V. 1. M HNH V

o

e, cn xy dng nhng h thng th nghim. H - Hai b cha nc c dung tch ln ng vai tr b nc thng v h lu; - Turbine m hnh, thng c ng knh BXCT D1M thng 250 v 460 mm; - My bm bm nc t b h lu ln b thng lu lu thng nc gia cc b v to ct nc cho turbine m hnh; - Thay th my pht in l mt thit b o cng sut trn trc turbine m hnh; - Cc thit b o cc thng s cn thit nh Q, H, n, ...

Thng c hai loi h thng th nghim: h thng h v h thng kn. V. 1. 1. H thng th nghim h

Hnh (5-1,a) trnh by s h thng th nghim h. c im ca n l c mt thong hai b nc thng v h lu, mt thong chu p sut kh tri. Ct nc ca m hnh l hiu chnh lch mc nc ca hai b, v vy ct nc to c l nh. M hnh h ch c th th nghim nng lng m khng th th nghim kh thc.

Theo s th nghim ny, khi lm vic nc t b thng lu 2 chy qua ng p lc vo turbine 4 tho qua ng x xung b h lu 7, y lu lng Q c o bng p trn thnh mng tam gic vung 8. Nb n b 2 nh my bm 1 v qu trnh li tun hon.

Khi lm th nghim, tin hnh o cc i lng chnh nh: lu lng Q, ct nc H, s vng quay n, mmen xon M, cn dng nhng thit b v c cu sau:

Lu lng Q chy qua turbine c xc nh theo chiu cao lp nc trn nh p trn h (m), bit h c th xc nh lu lng theo cng thc kinh nghim sau:

Q h= 1 343 2,47, (l/s) h xc hn c th o Q bng phng php th tch, tc l dng thng ong.

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51

ng lu v b h lu khi mc

m hoc dng

o ct nc H bng ng o p ni ring b thnc hai b n nh, hoc o theo hiu s v tr phao ca mc nc hai b. o s vng quay n (v/ph) trc turbine bng vng quay k kiu ly tmy m vng quay bng in. o mmen xon trn trc turbine bng b hm kiu ma st (hnh 5-1,b). Mmen xon c tnh theo cng thc: M = P.l, t M c th tnh ra cng sut hu ch Nh = M.

Hnh 5-1. S h thng th nghim h.

Ni dung th nghim xc nh c tnh nng lng ca turbine trn cc bng th gm: Th nghim vi mt s m cnh hng dng a0 v gc t cnh . - Vi mi m cnh hng dng khng i a = const, v gc t cnh khng i i vi turbine cnh q ng ng p lc ca

vng quay

ng v h lu ng kn khng o ra.

gun to u x

ung

0

uay) = const, ta iu chnh van kho trn (turbine. ng vi mi m van kho ta o c thng s: ct nc H, sn, lu lng Q, cng sut hu ch Nh ca turbine. Tin hnh thay i m van kho theo th t t ln n nh (khong chng 6 - 8 m) v o cc i lng H, n, Q, Nh tng ng vi tng m kho. - Sau khi c cc gi tr H, n, Q, N ca cc im ng vi mi m kho, tnh hiu hsut v xy dng cc ng cong quan h gia tng cp thng s vi nhau. T cc ng c tnh quan h xy dng c tnh tng hp ca m hnh. V. 1. 2. H thng th nghim kn c im ca h thng th nghim kn l b ththng vi kh tri v ct nc th nghim do my bm t Hnh (5-2) l mt s ca h thng th nghim kn. H thng g m np bm 1, van kho 12, nc vo bnh cao p 13, trn ng p lc t thit b o llng 11, nc vo bnh n nh vn tc 8, 9 trc khi vo turbine 4, ri theo ngx b kn h lu 2, tr v my bm 1, v qu trnh lp li. Thit b o cc thng s gm c: o vng quay 5, o cng sut 6, cc p k 14, 15 o ct nc .H thng kn ngoi vic tin hnh th nghim nng lng cn c kh nng th nghim v kh thc . Do vy trong h thng ny c trang b thm bm chn khng 3 ht khng kh pha trn mt nc bnh 2.

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H thng kn c u im l c kh nng th nghim kh thc, kch thc nh, tuy nhin h thng ny c kt cu phc tp, thit b o cng phc tp hn h thng h.

Hnh 5-2. S h thng th nghim tirbine kn

V c th nghim nng lng tin hnh vi cc m a0 = const v cc gc t c tin hnh theo trnh t v ni ch trnh by cch th nghim kh

c uan h m a0 (v ) hng s. Kt

kh thc trn

m kh th c tin hnh trn h au khi n h nh th m c tnh nng l nh ra cc c n thit phi ti n

nh c tnh kh thc ti cc ch , c th l xc nh h s kh thc a cc ch . V d cn xc nh h s ch A no ( c a0, , HA, QA, nA, A) ta iu chnh kho 12 trn ng p l c c cc thng s HA, QA, nA, NA . Sau , c chn n lm ic o p sut trong b l 2 gi p t n ng n 2. H kh thc tnh c th n c:

ica cnh BXCT = const (i turbine cnh quay)

thng h. ydung tng t tin hnh i vi h thc. Ni dung ca th nghim kh th c trn h thng th nghim kn nhm v q gia hiu sut v h s kh thc ng vi ccqu o c quan h = f() tnh ton v v c cc ng ng h sng c tnh tng hp chnh ca turbine. Ph ng php th nghi

nghic

ng th c th thng kn. Sh cti

hnh xc

c N c ho bm kh g 3 v , h u c tr such kh P2 o b s eo c g th

= 2P

HPH

HHA

bhA

sA

(5-1)

Trong (5-1): Pbh p s t ho hi g vi nhit n m; S - ch u ine th nghim.

Tng ng thc chung:

l u n c th nghi H icao ht ca turb

ng vi trng thi A ta cng tnh c A theo c 52

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53

= =h NN Q H. .

M102100%

. . (5-2)

trong cNh v y bm chn khng to ra v nhi nh theo cng thc (5-1) v theo cng thc (5 khng P2 bng cch thay i ch lm vic c . lp quan

vo th (hnh 5-2,b) xc nh h s kh thc ti hn KP (im k)

hi m

uan h gia cc thng s ca turbine gi l ng c tnh ca turbinetnh biu th

g

quan h N,nc H = ng s dnguyn tnh theo ph .

Qua cc ng tr- Trn ng c tnh cng tc cng sut (hnh a): khi = 0 v N = 0 th Q v a0

vn khc k u c mt lu gtht nht ng vi cng sut ln nh ng vi mt gi tr cng sut nh hn cng sut ln nht.

- Trn hai ng c tnh lu lng v m (hnh b,c) ta thy hiu sut v cng sut hu ch bng khng ng vi Q v a0 lun nh hn 100%.

Trong cc ng c tnh cng tc ngi ta hay dng dng ring biu th quan h

ng thc (5-1): M = P.l (kGm); = 1000 kG/m3, Q (m3/s), H (m ct nc). y ng vi mi gi tr ca p sut chn khng P2 do mt ca nc, ta c c mt tr s t-2). Gi nguyn ch A, thay i chna my bm chn khng 3, ta c mt lot cc cp quan h gia v

h = f() ng vi a0. Hin tng kh thc s xy ra khi lu lng, ct nc v p sut gim mnh, ko theo s rung ng my v ting n. Trn thit b o ta c th xc nh c cc gi tr ny. Cn cch A. Thay i ch khc, theo cc quy trnh trn lp li. Th nghim kh thc i

t nhiu cng sc v kinh nghim mi bo m chnh xc.

V. 2. NG C TNH CA TURBINE ng biu th q. C hai loi ng c tnh: c tnh n v c tinh tng hp. Cc ng c n biu th quan h gia cc cp hai thng s mt; cc ng c tnh tng hp quan h gia nhiu thng s ca turbine.

V. 2. 1. ng c tnh n T kt qu th nghim, sau khi xc nh c c thng s cc ch khc nhau ta c th thit lp quan h gia cc cp thng s, cn cc thng s khc l hng s. C ba loi n c tnh n: c tnh cng tc, c tnh vng quay, c tnh ct nc.

1. ng c tnh cng tc Cc ng c tnh cng tc nu biu th cc quan h: , Q, a0 = f(N), hoc cc

, a0 = f(Q), hoc quan h Q, , N = f(a0), trong iu kin: n = const v ct const (hnh 5-3). Cc quan h ny biu th cc th ng khng th

n trm n cho php ta c nhng nhn xt cn thit i vi turbine:

hng, v rng mu n pht ra c mt cng sut h ch no th cn phi lng khng ti tn ng vi m nh nht no khc phc cc tn nh trong turbine. Mt khc ta thy hiu sut ln nht khng t, m

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Hnh 5-3. Cc ng c tnh cng tc cu turbine

gia hiu sut v cng sut ca cc loi turbine khc nhau ( hnh 5-4), nhm so snh c tnh hiu sut gia cc turbine. Qua ng ny ta c nhn xt:

Hnh 5-4. ng c tnh c loi turbine

ng

- Hi loi turbine c tng i dc nn vng lm vic c g lm vic vi hiu sut cao b thu hp nhiu; - Turbine cnh quay c ng c tnh cng tc thoi hiu sut cao ln, do vy c vng lm vic vi hiu sut cao m rng hn c. S d c c tnh u vit ny l nh cnh xoay c a trng thi lm vic v gn trng thi thit k.

2. ng c tnh vng quay ng c tnh vng quay biu th cc thng s Q, N, theo vng quay n khi ng knh D1, H, a0 khng i (hnh 5-5,a). T ng ny ta thy hiu sut cao khng trng vi N v Q ln nht. Khi n tng th cc thng s s thay i.

cng tc ca c

- Turbine go c hiu sut max nh nht, nhng ng c tnh thoi nn c vlm vic vi hiu sut cao c ni rng;

u sut max cu turbine tm trc v turbine cnh qut ln nht trong cc . Tuy vy nhng ng ny ca turbine tm tr hiu sut cao b gim, cn ng ca turbine cnh qut th rt dc nn vn

54

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l/s

Hnh 5-5. Cc ng c tnh vng quay v c tnh ct nc.

3. ng c tnh ct nc ng c tn s Q, N, ca turbine theo

t n qu trnh vn hnh. Trn th ta y:

hc nhau. Cn lu

ng thi tham gia vn hnh v thay i. c

ng c tnh tng hp chnh c lp ra t th nghim m hnh ca mt rbine mu i din cho mt kiu turbine, t kt qu th nghim m hnh , s dng

c cng thc tng t v quy dn tnh ton v ra cho mt turbine c ng knh D1 = m, lm vic vi ct nc H = 1m. Do vy ng ny dng cho mi turbine c kch c khc nhau nhng cng mt kiu .ng c tnh tng hp ch yu biu din cc

h ny biu th quan h gia cc thong c c H. Ct nc ca turbine lun thay i trong th ng vi = 0 v N = 0 th cn c ct p no c trng cho tn tht thu lc ch khng ti. Nhn chung khi H tng th cng sut turbine tng, nhng hiu sut cao nht li t c mt gi tr ct nc no ng vi m a0 klng Q th tng cng vi H tng (hnh 5-5,b). V. 2. 2. ng c tnh tng hp Cc ng c tnh n nghin cu trn ch mi biu th c quan h gia tng cp thng s trong khi nhng thng s coi nh khng thay i, iu ny khc vi thc t vn hnh ca turbine l cc thng sV vy cn c ng c tnh biu th cc thng cng tham gia vn hnh. ng tnh nh vy gi l ng c tnh tng hp. C hai loi ng c tnh tng hp l: ng c tnh tng hp chnh v ng c tnh tng hp vn hnh. 1. ng c tnh tng hp chnh

tuc1th

55

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56

u lng quy dn Q1, cc h ng sau (hnh 5-6):

thng s turbine thng qua hai bin l vng quay quy dn n1 v ln gm

Hnh 5-6. Cc ng c tnh tng hp chnh

- H cc ng ng hiu sut = f (n1, Q1) ; - H cc ng ng m cnh hng dng a0 = f (n1, Q1) ; - H cc ng ng h s kh thc = f (n1, Q1) ; - ng hn ch 5% cng sut (ch c turbine tm trc v cnh qut, hnh 5-6,a) ; - H cc ng ng gc t cnh = f (n1, Q1) dng i vi turbine cnh quay em hnh 5-6,c).

- T ng c tnh ca TB go (hnh 5-6,b), ta thy cc ng ng m a0 c ay th bi cc ng ng hnh trnh van kim trong vi phun s = f (n1, Q1) .

Cc ng ng hiu sut ca turbine cnh qut rt dc, ngha l vng lm vic i hiu sut cao rt hp. Ngc li, turbine cnh quay v turbine go th cc ng ng hiu sut thoi, do vy vng lm vic vi hiu sut cao ca nhng loi turbine ny

(x th

v

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c m rng. T thy rng khng nn cho turbine cnh qut m nhn phn ph ti thay i hiu sut thp.

ng ng h s ay c tr s ln hn nhiu

hn ch lm vic ch turbine thc nh

i nhiu, v vi ch lm vic turbine cnh qut lm vic vCc kh thc ca turbine cnh qu

so vi turbine tm trc, do vy vn kh thc trong vn hnh i vi turbine cnh quay l vn cn c bit ch khi chn ng knh D1 cng nh khi vn hnh..

Trong hai loi turbine tm trc v cnh qut c thm ng hn ch 5% cng sut, nu vn hnh vt qu gii hn ny hiu sut turbine s gim thp rt nhiu. Do y trong vic chn thng s turbine ny cn ch m bo yu cu . v

ng c tnh tng hp chnh l c tnh m hnh ca mt kiu turbine, n nh gi kh nng lm vic v cht lng ca turbine m hnh. N l ti liu gc c

2. ng c tnh tng hp vn h ng c tnh tng hp vn hnh l ng c tnh ca ca mt turbine c th c ng knh D1 v vng quay n bit. ng c tnh ny c xy dng trong h trc to ct nc H v cng sut N, n biu din cc ng sau (hnh 5-7,a): - H cc ng ng hiu sut = f (N, H); - H cc ng ng cao ht nc Hs = f (N, H); - H cc ng hn ch cng sut turbine v my pht . Trn ng c tnh tng hp vn hnh ta thy: im A l giao ca hai ng hn ch

Hnh 5-7. ng c tnh tng hp vn hnh. cng sut ca turbine v my pht, im ny tng ng vi ct nc Htk. Ta thy rng khi ct nc nh hn ct nc thit k H th khng th pht ra c cng sut nhtk mc (th hin cng sut chu cn do thiu ct nc), ch c lm vic vi ct nc H Htk th mi c th pht c cng sut nh mc. ng c tnh tng hp vn hnh

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gip ch ngi vn hnh xc nh cc ch lm vic ca turbine, xc nh cc thng s ti cc ine.

ng c tnh tng hp v d on h t turbine lm vi c

y pht) cng lm vi ng p hi cc ng ng hiu sut phi t hp cc ng

t tur t pht c cc mt y. xy d u su a nhm y. y d v ng cn N) a t hnh 5 ng n h a t -8, h m t

n n ca y b qua ia t v cng t m (N) ng I) n h = f a ha y

c t cn honh ng cch ly honh II).V my g hau o t i

III) n t y ta c v theo rnnh c tnh cng tc c m c m n th cho chy mt y; cu N1 N2 t y 1 v g lm c song song l t cu N th c my cng lm v ti n nh c c ca nhm t bao t -2

n ra r cn nh ti i m th u s c n cc

g m hn t vy vng lm v hi cao a mt hp vn c c u t s cao . i rt c ngha i nh h t y i n u. tnh hp v hnh c m t y n h tn p vn hnh ca nh m c x ng

trn c ca ng c tnh tng hp vn hnh ca mt t my bng cch cho trc

hp vn hnh l

ch lm vic, cho php xc nh kh nng pht ra cng sut turb n hnh cn biu th

nhm t y ng to H ~ Q (hnh 5-7,b) .

V. 2. 3. ng c tnh c thc t vn

a mTr g nh TT khng ch c m

c, do vy phc m nhiu t

my (turbine + m i xy dng c tnh tng hvn hnh cho nhiu t my. Khiu su bine, hiu su my ng ng hiu sut ca t mSau ng ng ng hi t c t m Di l v c tnh g tc ( = f( ca b my ( -8,a) v ng t hp v nh ctrm c 3 my (hnh 5 b). 1. ng c tn

g c tnh ccng tc ca nh my

g tc 1 t m iu th n h g hiu susut ca y 1m = f

h ra c (

ung . v ng q

N xc ua 2m

nh b(N) c i t m

ging nhau ta ny nmt t m hn vi 2 ( ng i 3 t ing n nhn h nh m my v

3 (ng . Vi nhm m ng cch t . H 5-8,a l l ng a nh ba t y ging hau: - Khi ph ti yu cu N N1 t m - Khi ph ti yu < N m 2 cn vi i u; - Khi ph ti yu > N2 ba t ic th u. V vy g c t ng t my l ng rn 0-1 -3-4. Tng c t t m a cng

u, n mt y chnh nhm y t nh ng g m n ph thay

nh nha u ch lp t m o tr tuy hi

ut max

a n cao hmax tn y cng n i, tuy

iic c u sut c my

hn, cn g lm vi a nh my hn u ny i vtrm m n phn p i tha hi 2. ng c tng n a nh m g c tn g h m t y ging nhau y d

smt s gi tr ct nc H s c c tng ng cc gi tri hiu sut v cng sut N ca mt t my. Nhn cc gi tr , N vi 2, 3, 4, ... t my. Ni cc im c cng hiu sut khi TT lm vic vi 1, 2, 3, 4, ... t my ring li vi nhau bng cc ng cong trn, ta s c ng c tnh tng hp vn hnh ca nhm t my (hnh 5-8,b). i vi trm c cc turbine khc nhau th ng c tnh tng tp hp cc ng c tnh tng hp vn hnh ca ring tng t my hay ca tng nhm t my ging nhau lm vic cc khu vc khc nhau.

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Hnh 5-8. c tnh hm t y. V. 3. X C TNH TNG HP V N HNH Ph ta bit mt s ng c tnh ca turbine. Trong ng c tnh t ng g a mt k turbine c v t th nghim m hnh, k v to turb e thc h v cung p. i vi lnh vc la c e cn su hn iu qu a tnh ton nng lng c lin quan n, do vy chng ta cn bi ch xy ng ng c tnh tng rb c th. S u bit c gm: Ct n t nc t k H a turb e thc;

ng knh tiu chun ca turbine thc D1; Vng quay ng b ca t my n ca turb e thc; g c tnh tng hp chnh ca turbine m hnh c ng nh D . Sau y l n hnh: 1. Xy dng cc ng ng hiu sut = f (N, H) ng knh turbine thc v m hnh khc nhau do vy hiu sut, vng quay, lu lng ca chng s khc nhau. Do vy trc khi tnh ton v ng c tnh tng hp vn hnh ta phi tin hnh tnh ton hiu chnh cc i lng ny: - Hiu chnh hiu sut ca turbine thc theo hiu sut turbine m hnh:

ng ca n m

Y DNG NG n V. 2. chng ng hp chnh l

t c c iu , n

in ra

do cc c quan thiin

ch in chn v s dng turb

c ch i v h c

c n turbine t dhp vn hnh ca mt tu ine li tr c lm vic t Hmin n Hmax, c thi TK c in

Cng sut nh mc ca turbine v ca my pht in;

inn 1M

i dung v cc bc tnh ton v xy dng ng c tnh vn

T M = + (5-3) 59

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Khi ch lm vic ca turbine thay i th hiu sut cng thay i, rt kh tm ra c chnh lch hiu sut gia hai turbine ng vi tng ch lm vic. Do vy ngi ta da vo ch lm vic ti u ca hai turbine tnh ra = T max - M max v dng chung cho mi ch lm vic. Trong T max , M max xc nh theo cc cng thc cho (4-24) hoc (4-25) chng IV. Nu < 3% th khng cn hiu chnh hiu sut. i vi turbine cnh quay, chnh hiu sut ng vi cc gc t cnh , cng hiu chnh theo ch lm vic ti u ca hai turbine. - Hiu chnh vng quay quy dn n' , cng da vo ch lm vic ti u hiu chnh cho mi ch lm vic:

1

1 10 1' ' maxmax

( )n n MM

= v 1' ; nu gia s n'1 3% th cng khng cn hiu chnh vng quay quy dn. Sau khi hiu chnh ta lp bng tnh quan h = f (N, H) cho cc loi turbine vi mt s ct nc: bng tnh 5-1, bng 5-2 nh sau:

Bng 5-1. Tnh cho turbine Tm trc v Cnh qut. Hmin Htk Hmax

1 1M' 'n n n= +

1 1' min( ):n n D H= 1 1' ( ):n n D Htk= 1 1' max( ):n n D H= Hiu chnh ' ' '= 1M 1 1n= 1M 1 1n= ' 'n n ' 'n n 1M 1 1' 'n n n

minN Q D H= 9 81 1 12 3 2, ' / N Q 2 3 2, ' N Q D H= 9 81 1 12 3 2, ' max/D Htk= 9 81 1 1 /

M N Q'1 N Q'1 N Q'11 3 4 5 6 7 8 2

Ct 1: tra trn ng c tnh tng hp chnh; Ct 2: Ly ct 1 cng vi ; Ct 3, 5, 7: k ng ngang n'1M trn ng c tnh tng hp chnh, gp cc ng ng hiu sut M tng ng s tra ra Q'1; Ct 4, 6, 8: Tnh ra theo cng thc tng ng vi tng ct nc.

Bng 5-2. Tnh cho turbine Cnh quay.

Hmin Htk Hmax 1 1' min( ):n n D H= 1 1' ( ):n n D Htk= 1 1' max( ):n n D H= 'n1M 1 1' 'n n= 1M 1 1' 'n n= 'n 'n1M 1 1' 'n n= N Q D H= 9 81 1 12 3 2, ' min/ N Q D Htk= 9 81 1 12 3 2, ' / N Q D H= 9 81 1 12 3 2, ' max/ M Q'1 N M Q'1 N M Q'1 N 1 2 3 4 5 6 7 8 9 10 11 12 13 14

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Ct 1: Tra trn ng c tnh tng hp chnh;

, mi gc c hiu chnh ring; Ct 3,7,11: k ng ngang n'1M trn ng c tnh tng hp chnh, gp cc ng ng gc t ni suy ra hiu sut mu; Ct 4, 8, 12: ly ct M cng vi ct 2; Ct 5, 9, 13: ng vi M dng tm Q'1; Ct 6, 10, 14: Tnh theo cng thc ghi trn vi ct nc tng ng

T cc s liu tnh cc bng trn (cc ct 2 ~ 4, ct 2 ~ 6 v 2 ~ 8 ca bng 5-1 cho turbine Tm trc v Cnh qut; cc ct 4 ~ 6, 8 ~ 10, 12 ~ 14 i vi turbine Cnh quay) v ra cc ng c tnh cng tc = f (N), vi mi ct nc s c mt ng (hnh 5-9,a). - Lp h to H ~ N (hnh 5-9,b) cng t l honh N, t bn di h ~ N;

+Trn trc H ca h trc H ~ N k cc ng nm ngang Hmim, H tk, Hmax; + Trn trc nh ra cc gi tr v k dng ngang, ct cc ng ~ N mi

ct nc c hai im v d 1~1' hay 2~ 2'; 3~3' dng xung gp cc ng ct nc tng ng (hnh 5-8,b);

+ Ni cc im cng hiu sut ( c hai nhnh) li ta c ng ng hiu sut. sut = f (N, H)

. Xy dng ng hn ch cng sut ng hn ch cng sut trong ng c tnh tng hp vn hnh c hai nhnh o turbine v my pht hp thnh, chng ct nhau ti tung ct nc thit k Htk

pht l ng thng ng c

onh

Ct 2: tnh nh trnh by nhng ly giao im vi cc gc

Vi nhiu tr s cho trc ta s v ra nhiu ng ng hiu 2

d(im A) trn hnh (5-9,c). ng hn ch cng sut my

h l mpTB

mp

lmNN N

so may= = . ng hn ch cng sut turbine c th l cong hoc gn ng l thng. Cch xy dng ng hn ch cng sut turbine nh sau:

Xy dng nhnh hn ch cng sut cho turbine Tm trc v Cnh qut da vo ng hn ch 5% cng sut trn ng c tnh tng hp chnh ca kiu turbine mu (hnh 5-9,d). bit im A ( mp tkN H, ) , cn xc nh thm im B ( BN H, )min ri ni hai im A v B li theo ng thng l

c. T 1min

1'nn D= , k ng thng nm ngang n gp ng hn ch H

cng sut 5% v tra c 1'Q v ni suy c hiu sut mu M tng ng,

tnh ra hiu sut turbine thc = M + v xc nh ra cng sut turbine ti im B theo cng thc bit. C NB, Hmin xc nh c im B.

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Hnh 5-9. V cc ng ng hiu sut v ng hn ch cng sut.

* Xy dng nhnh hn ch cng sut cho turbine Cnh quay phc tp hn v c rbine ngh, cho rng: hai cch tnh. y trnh by cch tnh ca nh my ch to tu

Khi ct nc H > Htk th cng sut turbine b hn ch bi gc t cnh max; Khi ct nc H Htk th cng sut turbine b hn ch bi m a0max . Ta bit nhnh hn ch cng sut turbine dc xy dng t ct nc H Htk , do vy ta tnh v nhnh hn ch cng sut turbine theo m a0 nh sau: - im A l giao ca ng hn ch cng sut my pht v Htk xc nh d dng trn h to H ~ N (hnh 5-10,a). i to im A sang to n'1 ~ Q'1 trn ng c tnh tng hp chnh ca turbine m hnh (im A') bng cng thc quy dn:

62

1tk1'n

n D= v Htk 1A 12 3 29 81 /,

N'QD HA tk

suy ra Q'A 1A'

B, lm cc bc sau: t ng ngang

v Q'1, tnh ra B

= t im A' (Q'1A', n'1tk ) ln hnh (9-10,b) v ni suy c a0max . - Tnh ton xc nh im B ng vi ct nc Hmin v N

+ V ni suy ng ng m a0max (hnh 5-10,b), ng ny cn'1M ng vi ct nc Hmin ti im B' v ni suy ra B'M+ Tnh ra B BN Q D H= 9 81 1B 12 3 2, . . . .' min/ . Nh vy xc nh c im B; + Ni im A vi B ta c nhnh hn ch cng sut turbine phn H H

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Hnh 5-10. Xy dng ng ph tr.

3. Xy dng cc ng ng cao ht Hs xy dng ng ng cao ht HS = f (N, H), ta cn v cc ng ph tr

N ~ Q ' (hnh 5-10,c) da trn kt qu tnh ton bng -1 , ho

, ng thi cng tra c Q'1 tng ng. C Q'1 tra ra cng liu trn vo cc ct t 1 - 4 v

ca cc ct nc trn to 15 c bng 5-2 trn. Sau lp bng tnh (5-3) tnh di y: - Lp bng 5-3 vi cc ct nc cho trc (t nht ba ct nc Hmin, Htk, Hmaxs); - Trn ng c tnh tng hp chnh (hnh 5-10,d) ng vi tng ct nc ta c n'1M, k ng ngang n'1M , ng ny gp cc ng ng h s kh thc ti cc im, ti ta ni suy ra M, tnh ra sut N tng ng vi ct nc trn (hnh 5-10,c). Ghi stnh cc ct 5, 6 v HS = 10 - /900 - kH; - T bng 5-3 v ng ph tr HS ~ N, mi ct nc c mt ng (hnh 5-10,e); - Gi thit cc tr s cao ht HS v k cc ng ngang gp cc ng H , ta c cc N tng ng v xc nh im c cp to N, H. Vi nhiu im ta s v c cc ng ng HS= f (N, H) trn ng c tnh tng hp vn hnh.

63

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Bng 5-3. Bng tnh xy dng ng ng cao ht Hmin Htk Hmax

64

1 1' min( ):n n D H= 1 1' ( ):n n D Htk= 1 1' max( ):n n D H= 1M 1 1' ' 'n n n= 1M 1 1' ' 'n n n= 1M 1 1' ' 'n n n=

k = 1,05 - 1,10 k = 1,05 - 1,10 k = 1,05 - 1,10 Q'1 N kH HS 1 2 3 4 5 6 ... ... T kt qu ca cc tnh ton nh trnh by t