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GIO TRNH TUABIN THY LC

Thng 11-2010

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:2 1 V12 2 V2 p1 p 2 + H = (Z1 - Z2) + 2g Z1-Z2 : l thnh phn nng lng do chnh lch v tr to ra, gi l v nng; p1 p 2 : l p nng; gp v nng v p nng thnh th nng ( T ). 2 1 V12 2 V2 : l ng nng ( ). 2g 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 tri. Turbine xung kch uc chia ra cc h sau: + 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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* 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 chy ca vo ca BXCT lun ln hn p lc ca ra ca n. Dng chy qua TB l dng lin tc in y nc trong ton b mng cnh. Loi ny c chia ra cc h sau: + H TB xuyn tm hng trc ( gi tt l l turbine tm trc, hay Franxis); + H TB hng trc ( gm turbine cnh qut v turbine cnh quay ); + H TB hng cho; + H TB dng ( gm turbine dng na thng v turbine dng thng ); + H TB thun nghch ( lm vic theo hai ch : my bm v turbine). 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 dng tia trn cc cnh bnh xe cng tc (BXCT) l chuyn ng khng p hay cn gi l dng tia t do. Sau y chng ta nghin cu c th cc 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 turbine, lm quay 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.

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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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. S phi 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).

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 thng vo cnh go thng gc (theo chiu quay) lm tng cnh tay n ca mmen quay v trnh mmen ngc ca tia nc vo pha sau go nm pha trc. V turbine c nhim v khng cho nc t bung BXCT bn ra ngoi gian my. V 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, c b tr u chung 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 cc trm thy in nh c lu lng b, ct 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 BXCT turbine xung kch hai ln gn ging lng sc. Dng nc t vi phun tc dng vo cc cnh pha trn (nhn khong chng 80% nng lng ca dng nc) y BXCT ln th nht, xong li i vo khong trng gia BXCT ri li tc dng ln 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. Nh vy 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 kch phun xin (hnh 1-5) c hnh dng ging turbine go ch khc 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

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my pht 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 thay i 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. I. 3. 1. 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 x theo hng dc trc. Do vy gi l turbine tm trc. Turbine ny do k s ngi Php tn l Franxis hon chnh nm 1849 nn cn gi l turbine Franxis.

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 dng loi ny vi cng sut mi turbine l 508MW, ng knh D1 = 7,5m. nc ta, TT sng v Tr An u dng turbine 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 cnh qut (hnh 1-9) gm c bu, c gn t 3 n 9 cnh, 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 quanh bu, do vy thch ng c cc ch lm vic khc ch thit k dn n vng lm vic ca turbine vi hiu sut cao c m rng. Do vy TB cnh quay c kh nng lm vic vi cng sut v ct nc thay i nhiu. BXCT ca TB cnh quay 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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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 du c p vo mt ngn no ca xi lanh cn ngn kia du thng vi l du x th pittng ln thanh truyn 7 s dch ln

Hnh 1-10. Turbine Kaplan hoc xung, do lm xoay cc cnh theo cc gc quay nh nhau. So vi turbine cnh qut 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.

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I. 3. 3. Turbine cnh cho

Hnh 1-11. Turbine cnh cho 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 trn. Turbine cnh cho c s dng cc TT c ct nc H = 30150m. N thuc loi turbine cnh quay. BXCT gm 10 n 14 cnh c gn vo bu 3 hnh chp nh cc trc cnh 2. Trc cnh lm vi trc turbine mt gc 300,450,600 nn dng chy trong BXCT cho gc vi trc. Cng nh turbine cnh quay, cc cnh BXCT quay c quanh 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. Loi turbine ny c ch to Nga dng cho TT Buctamin c cng sut N = 77MW, ct nc H = 61m, 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 chy thng v na thng. Turbine dng thc cht 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 hiu sut cao hn so vi turbine phn kch khc n 30% do kh nng tho nc ca n. Turbine cap xun c s dng rng ri 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.

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Hnh 1-13. T my cp xun 2. Turbine dng thng turbine dng thng (hnh 1-14), dng nc theo bung turbine hnh tr thng i qua Stator trc 1 vo b phn hng dng 2 v tc ng vo BXCT 3 v h lu theo dng thng. Rtor my pht in 4 c gn vo mt cnh TB, do vy khi BXCT quay

Hnh 1-14. Turbine dng thng

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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 turbine v my bm tri 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 hng dng (CCHD) 2 dng hnh cn thay i ph hp vi ch bm hay turnine; "bng n" (capxun) 4 kn nc, c gn c nh vo btng nh my nh cc ct 3. 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 5,35m, bn cnh quay xung quanh bu vi cc gc t -50 n +350 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.

16

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 dng ca tng loi turbine. Chng II s nghin cu c th hn v cu to, cng dng ca 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 nhng b phn chnh sau y: vng b ca turbine, c cu hng dng, trc v trc ca turbine 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 truyn xung mng nh my cc ti trng gm trng lng ton b t my, sn v b 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 kiu stator : kiu ct ring r v kiu vng (a). Phn ln cc turbine phn kch u s dng kiu vng tng cng, cn kiu ct ring r 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 2-1,b v bng (2-1) xc nh kch thc vng b (stator)

17

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 180 200 225 250 280 320 360 400 450 500 550 600 D0 220 240 275 290 325 375 420 465 525 580 640 700 Z0 cn h 16 16 16 24 24 24 24 24 24 24 24 24 Cho bung xon b tng ct thp Db Da D4 R h1 h2 Cho bung xon kim loi Db Da D4 R H 260 285 320 330 372 426 480 532 600 660 730 800 305 335 375 390 438 500 555 615 695 765 845 925 330 360 400 415 463 535 590 650 735 805 885 965 20 20 20 25 25 30 35 35 40 40 50 50 21 23 23 25 25 32 35 41 41 46 46 50

340 382 437 485 542 610 675 745 875

390 438 500 500 620 700 777 855 935

400 448 510 570 630 710 780 805 945

28 30 30 35 35 40 40 50 50

32 35 40 40 45 45 50 50 55

23 25 30 30 35 45 40 40 45

II. 1. 2. C cu hng dng (CCHD): Nc ln lt t bung turbine 1 chy vng qua cc ct stator 2, chy qua khe h gia 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 tuyn v c 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 r nc cn c m chng r bng cao su. B phn 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 khin 5 t my iu tc quay ko tay quay 6 v thanh ko 7 lm quay vng 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 in Trc turbine trc ng bn trong rng lp cc ng dn du (i vi cnh quay), dn kh 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.

19

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 thnh 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 vi trc quay ca 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. - Thun tin cho vic b tr turbine v thit b ph ca n trong gian my ca TT. - p lc tc dng ln BXCT u nhau trnh mn khng u trc. 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 ng 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 nht d to nn dng xoy cc gc lm tng tn tht ct nc. khc phc nhc im ny nn dng bung h xon. Hnh 2-4 th hin hnh thc cc loi bung h. Chiu di v chiu rng ca bung ly theo kinh nghim A = B = (3- 4).D1 , nhng

20

ti thiu ca np TB so vi mc nc nh nht trong bung: hmin (0,9 -1)D1. II. 2. 2. Bung hnh ng Loi ny thng dng vi ct nc H = 67m n 2530 m. Bung ny c lm bng kim loi cha cc b phn ca turbine (hnh 2-5): chp nn hng dng 4 dn nc vo thun dng, cc cnh hng dng 1, BXCT t pha trong CCHD. Hnh dng ca bung ging mt ni xpde, na trc 5 ni vi ng p lc 7, na sau 2 cha cm BXCT v ni vi on khuu cong 8 ca ng x 12. Trc turbine 11 trc 10 a ra ngoi bung v t nm ngang. Loi ny dng vi turbine tm trc trc ngang, loi turbine nh. ng knh ln nht ca bung ly theo ng knh tiu chu ca BXCT D1, khong (2,8 -3,5)D1 , chiu di bung khong (2,5 - 3)D1.

Hnh 2-5.Bung turbine hnh ng II. 2. 3. Bung xon c Bung xon (hnh 2-6) l loi c s dng rng ri nht hin nay. Loi bung ny bo m dn nc vo TB vi kch thc mt bng ca turbine nh v m bo ch 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 thng dng bung xon kim loi hoc b tng ct thp tit din trn. Phn loi bung xon ty thuc vo gc bao max max ca bung xon , y l gc c tnh t tit din ca ra (r = 0) n tit din ca vo ca bung xon (v = max). Khi max = 34503600 th gi l gc bao hon ton (hnh 2-7,a), cn max < 3450 gi l bung xon khng hon ton ( hnh 2-6,c ).

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Kt qu th nghim m hnh cho thy, tn tht nng lng trong turbine, vng b v CCHD ( khi chiu rng gian my cho ) ph thuc vo quan h gia tit din ca vo bung xon chn gc bao. Khi tit din ca vo chn, nu tng gc bao, mt mt s lm cho dng chy phn b u chu vi CCHD, bo m c dng chy i xng trong turbine, nhng li lm tng vn tc dng nc trong phn xon v hnh thnh dng chy xoy, kt qu lm tng tn tht nng lng trong CCHD. Qua th nghim m hnh BXCT chn vi cc loi bung xon khc nhau ngi ta la chn loi bung xon li nht . Kinh nghim cho thy, chiu rng gian my l nh nht khi bung xon c gc bao max = 180 0 .V vy i vi TT c ct nc thp ( kiu lng sng ) gim thnh xy dng TT nn chn gc bao 18001920. i vi TT c ct nc trung bnh v cao do lu lng tng i nh, nnc th chn gc bao ln hn: t max = 27003450 . Vi trm thu in ng dn v sau p chn bung xon gc bao ln s tin cho vic ni tip gia ng ng p lc vi bung xon.

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 nht, cn tit din trn s ln nht v t s chiu cao trn chiu rng b/a ca tit din cng ln th mt bng gian my cng nh.

22

T l gia chiu cao v chiu rng ca tit din hnh ch T (hnh 2-7) nn chn theo cu to ca bung xon, c th chn kiu trn bng, kiu pht trin ln trn so vi 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 kt hp v nu ng c tip lc t ngay trn np turbin m khng b tr hm turbine. Cc gc v khng nn qu nh, v nu ly qu nh th iu kin thy lc trong bung s km v kh b tr ng c tip lc, nu qu ln th tng khong cch trc t my. Kin ngh dng nh sau: = 20350 v thng ly 300. Ni chung, khi m n th = 20350 cn khi m > n th = 10200; khi n = 0, = 10150. Cc gi tr khc kin ngh chn nh sau: khi m = 0 hoc n = 0, b/a = 1,51,85. Khi m v n 0 th 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 tit din ch T ca bung xon b tng. 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 ta gi thit: - Dng chy trong bung xon l dng chy dng, i xng qua trc quay v l dng i th; lu lng qua tit din bt k Q i ly theo gc i l: Q i = Q tt ; 360 0 - 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

23

i sao cho cc ng dng trong bung xon khng i. Thnh phn vn tc hng Q tt tm Cr phn b u theo chu tuyn trc mp vo cnh hng dng: Cr = ; D a b0 (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 chy i xng qua trc, dng c th v b qua tn tht dng chy. N c p dng i vi bung xon c gc bao max = 180 360 0 , v nu gc nh hn th iu kin dng chy s khng cn i xng qua trc. Phng php ny kh chnh xc v thun v ton hc nn c p dng rng ri; * Phng php tc vng l hng s Vu = K; Phng php ny gi thit tc vng bnh qun cc mt ct ngang bung xon u nh nhau. N cha lp lun khi thnh lp v n c nhng thiu st sau: + Dng chy tnh ton theo phng php ny khng hon ton ph hp thc t; + Gc bao cng ln th cng khng ph hp. Tuy nhin qua nghin cu thy i vi gc bao khng iu kin xon th phng php ny ph hp hn phng php Vu.r = K. V vy phng php ny dng tt cho TT c ct nc thp, bung xon b tng gc bao nh v giai on thit k s b. * Phng php tc vng gim dn t ca vo Vu n ca ra t (0,60,8)Vu; Phng php ny c nhc im l tnh i xng ca dng chy b ph hoi, nhng gim nh kch thc bung xon. V vy n ch dng vi turbine ct nc thp qu ln. Sau y chng ta nghin cu cch tnh bung xon theo hai phng php u. 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: Gi Q tt l lu lng ln nht qua mi turbine; V tb l tc trung bnh trong mt ct bung xon, xc nh theo:V tb = k H ( H = 2m th k = 1; H = 300m th k = 0,5) hoc theo th (hnh 2-9,a). Vi yu cu lu lng phn b u chu vi c cu hng dng, v vy nu gi i l gc i , din tch mt no ng vi tit din cn tm th lu lng qua n l Q i = Q tt 360 0 Q tt . i Q ct tng ng l F i = i = ; tng t vi max ta c: V tb 360 . V tb Q tt . max . F max = 360 V tb Nu ct mt di bt k c b rng dr, chiu ng b th din tch phn t dF = b.dr, vy:

24

Ri

Qi =

dQ = V u. b. dr ; vrara

Ri

Vu.r = K nn Vu = K/r, vy ta c: ( 2-1 )

Qi =

ra Ri K

r

b dr = K

Ri

Q b dr = tt i 360 ra r

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: mt ct trn ( hoc ellipsse) v bung xon mt ct a gic. a. Tnh ton bung xon mt ct trn (hoc ellipsse): Ni dung ca vic tnh ton bung xon l v ra c ng bao xon v xc nh mt ct ngang ca bung xon (hnh 2-9,b), ngha l phi xc nh ra c quan h gia gc i , bn knh Ri v din tch mt ct ngang tng ng Fi. T (2-1) t S i = Ri b ra r

dr , vy Qi = K.Si v K = Qi/Si, v K = hng s nn K =Q tt . max

Q max S max

, V u . . 360 Coi l tit din trn nn i2 = ( bi/2 )2 + ( ri - a)2, rt ra bi v thay vo Si ta c Si v thay vo (3-1) ta c gc : 720 . K. i = r a r a ( r a 2) = c r a r a ( r a 2 ) Q tt Trong cng thc c = ( 720.K.) / Qtt = hng s. Gii phng trnh i ta c c :

Gi bn knh mt ct ca vo (ng vi max ) l max =

[

] [

]

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

i =

i

2 ra

i

25

= hng s (2-3) max ra ra 2 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)

c=

max

r a max

(

)

i

i c

2 ra i c

2 ra i c

i

2 i

R i = 2 i r a

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. T quan h i ~ Ri v ra ng xon v t quan h i ~ Ri v mt ct ngang tng ng xem (hnh 2-9,b).

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 trn cc ng AC v EH ng vi cc Ri khc nhau t Rmax n ra

26

(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 2-9a

Hnh 2-10. S tnh bung xon a gic.Ri b T Qi = K.Si ta cn tm S i = dr . Ta c th dng phng php gii ra r 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);

27

- 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: S i = max . i (2-4) S max Bng 2-3. Bng tnh ton bung xon a gic Mt ct ABCHDE r b b/r r b b/r r b b/r Rv bv R4 bi bi/ri R4 ... ...... ra b0 ra b0 rb b0 rb b0

R3

M. ct A'B'CHD'E'

Mt ct ......

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 c quan h r ~ Q. - Vi tng r c Q v o c din tch F, tnh ra c V = Q/F v v c r ~ V. 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. - Lp bng tnh cc quan h ~ ~ R ( bng 2-4 ):

28

Bng 2-4. Bng tnh ton bung xon mt ct trn theo V = hng s Mt ct 1 Ca ra . . Ca vo

2 0 max

3 0 max

a = ra + 4 ra ra + max

R = 2 + ra 5 ra 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: Q tt max max = (2-5) 360 V u

i =

360 V u . max

Q tt i . max

= max .

max

i

(2-6)

Hnh 2-11. Tnh ton bung xon mt ct trn (ellipsse) v a gic. Ct 4: Tnh a i = i r a Ct 5: Tnh ra bn knh R i = 2 i r a 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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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, Db; Q tt . max , - Da vo Qtt v Vtb tra ra tit din mt ct ca vo bung TB: F max = 360 . V tb 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. Bng tnh bung xon a gic theo V = hng s Tn mt ct 1 Ca vo . . Ca raQ tt . max

Ri 2R max

Fi 3F max

i max

4

. .rb

. . 0

. . 0

Ct 4: T cng thc tnh din tch mt ct c vo F max v mt ct th i Fi :F max = Fi = 360 .V tb Q tt . i

lp t l Fi/Fmax ta c i = max F i = f ( R i) (2-7), 360 . V tb F max i , ghi vo ct 4. l quan h ng thng, do vy c Fi tnh ra tng ng tin s dng ta da vo bng 7 v ra cc ng quan h F ~ ~ R (hnh 211,b) v da vo quan h ~ R v ng xon ca bung, da vo quan h F ~ ~ R v mt ct ngang ca bung xon.

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II. 3. THIT B THO NC CA TURBINE THU LC Thit b tho nc (ng x hay cn gi l ng ht) l b phn khng th thiu turbine phn kch. N c nhim v tho nc t BXCT xung h lu vi tn tht nng lng nh nht. Ngoi ra ng x trong turbine phn kch c nhng tc dng sau y: - S dng thm phn ln ng nng cn li ca dng chy sau khi ra khi BXCT; - Tn dng thm ct nc tnh Hs (gi l chn khng tnh) tnh t mt ct ca ra BXCT 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 trng 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 nc chy trn mt thong 1-1 coi nh bng khng V1= 0, vy ct nc c th s dng c l Ha: 2 2 p3 3 V 3 p1 3 V3 Z3 ) = Zo Z3 Ha = E1 E3 = Zo ( 2g 2g 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: 2 2 p1 pat Z5 5 V5 5 V5 h 35 h 35 = Zo Hc = E1 E5 = Zo Z5 2g Ly Hc tr cho Ha ta c c ct nc tng thm H do c lp thm ng x so vi trng hp khng lp ng x: 2 2 3 V 3 5 V5 (2-8) H = Hc Ha = Z3 h 35 2g Trong ch s 3 tng ng vi ca vo ng x (hay ly gn ng l ca ra BXCT), ch s 5 tng ng ca ra ca ng x. T cng thc H ta thy: nng lng thu hi do ng x gm: thnh th nht l thm ct nc tnh Z3 k hiu l Hs gi l chn khng tnh , thnh phn th hai bao gm hai phn cn li, gi l chn khng

31

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:2 2 3 V3 5 V5

ox =

2g2 3 V3

h 35

0 th gim p sut tng ng s l , mt khc tng tnh an ton ta nhn thm vo H mt lng ( +)H, ta 900 c: HS [ HS] = 10 - ( +)H (3-4) 900 hoc: HS [ HS] = 10 - k H (3-5) 900 tra theo biu (hnh 3-2); H s k ly k = 1,05 - 1,1.

p p p = a H s H p hh ; rt ra a H s hh = H a H s H hh ; 0 0 T iu kin chun nhit bnh thng (15 - 30 ) th p sut ho hi khong (0,180,43m ct nc), ly p hh = 0,33m, p sut kh tri l Ha = 10,33m ct nc, mc

px

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 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 nh 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 khng xy ra xm thc ch thit k. i vi mi loi turbine th chiu cao ht nc quy c HS cng 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; - Turbine tm trc trc ng th HS ly t mp di cnh hng dng n mc nc h lu (hnh 3-3,a), cn cao trnh t turbine lm ly cao trnh qua gia CCHD; - Turbine 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. Cao trnh t turbine (lm) c quy nh nh trn, c lin quan n cao ht nc; khng pht sinh kh thc th 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 cng an ton 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 trnh. Cao trnh lp turbine c tnh cho cc loi turbine nh sau: - i vi turbine tm trc trc ng (hnh 3-3,a): bo (3-6) lm = Z hl + H s + 2 - i vi turbine hng trc trc ng (hnh 3-3,c): (3-7) lm = Z hl + H s + x D1 Vi x = 0,410,46 - i vi turbine trc ngang (hnh 3-3,b): D lm = Z hl + H s 1 (3-8) 2 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], thng dng lu lng ca mt turbine tnh mc nc h lu Zhl, cao trnh thc qu b, sai s khng cht l cao trnh t turbine ta cha bit, tuy vy do t s 900 ng k do vy c th ly ng chng cao trnh d nh t turbine (thng c th ly bng cao trnh mc nc thp h lu). tnh cao trnh t my ng hn, c th cho cc H, Q thay i ri tnh ra cc tr s lm , sau v ng tn sut lm ~ p%, da vo tn sut thit k ca trm tra ra c lm ri phn tch chn kt qu tho ng.

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Chng IV. NGUYN L CNG TC V LUT TNG T CA TURBINE TH LCIV. 1. DNG CHY TRONG TURBINE THU LC xt qu trnh bin i nng lng trong BXCT ca turbine thu lc trc ht ta tm hiu dng chy trong . Qu trnh chuyn ng ca dng chy trong BXCT rt phc tp, cc phn t cht lng va chy men theo b mt cnh dng cong khng gian li va chy vng quanh 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 turbine. Tt c cc phn t cht lng trong vng BXCT u tun theo hai chuyn ng: chuyn 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 gic tc 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 tng i W vi vn tc theo U .Cc gc 1, 2 tu thuc vo cu to v hnh dng cnh. Dng nc trong cc khe gia cc cnh ca turbine tm trc (hnh 4-1,a) chy dc theo thnh cnh, do vect vn tc tng i ca dng nc s hng theo trc cc khe ny. Nu chiu cao cc khe khng i th vn tc tng i W s t l nghch vi 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 bng vn tc tuyt

41

i ca vo BXCT (V0 = V1), nu vn tc tng i mp vo W1 trng vi tip tuyn ca mp vo BXCT th dng chy s rt thun khi chy ln bao prfin cnh v l "chy vo khng va" ca vo. V 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 dng chy trong BXCT c hng song song vi trc quay; - B phn CCHD nm cch xa BXCT, nn khong khng gian gia chng tng i ln do vy vect vn tc tuyt i mp ra cnh hng dng V0 khng th bng vn tc tuyt i ti mp vo bnh xe cng tc V1 c. Do vy iu kin "chy vo khng va" khng 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 tc ca vo v ca 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 mt dng nguyn t ca dng chy trong turbine ch lm vic n nh. T suy ra chung cho ton dng chy trong phm vi BXCT vi cc gi thit sau: - BXCT c s lng cnh nhiu v hn, cnh cc mng. Nh vy khe h gia cc cnh k tip nhau s rt hp, lc qu o chuyn ng tng i ca cht lng trng vi tuyn AB ca cnh (hnh 4-1,e); - Dng chy trong turbine l dng n nh. Nh vy th ng dng s trng vi qu o chuyn ng ca cht lng. Gi thit ny cho php ta tm c v tr v hnh dng ca ng dng trong turbine; - Dng chy qua turbine l dng l tng, do vy khng tnh n tn tht thu lc. Xt chuyn ng ca dng nguyn t tch ra t dng chy trong BXCT. Ly h trc to (r, u, z) theo phng hng tm, hng vng v hng ng, phn tch vn tc tuyt i V theo h trc trn ta c c thnh phn vn tc tng ng VR, VU v VZ, trong ch c thnh phn vn tc vng c kh nng gy mmen quay, cn hai thnh phn vn tc kia khng gy mmen quay vi trc Z.Do vy ta ch s dng vn tc vng thit 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 tng ng ti cc im dng nguyn t (hnh 4-1,e). Khi chy men theo b mt cnh, vn tc dng chy khng ngng i c hng v tr s, v vy cc ht cht lng chu tc dng ca cnh BXCT. Theo nh lut ba ca Niu tn th cc ht cht lng 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 vo c h . Nu xt dng nguyn t di chuyn t ca vo 1 n ca ra 2 sau thi gian dt th: dL 1 (4-1) = ( L 2 L1 ) = M c dt dt 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.

42

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 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: L1 = m . V 1 . r1 .cos 1 = . q . dt. V1 . r1 .cos 1 L 2 = m . V 2 . r 2 .cos 2 = . q . dt. V 2 . r 2 .cos 2 Thay gi tr L1 v L2 vo (4-1) ta c: dL = q ( r 2 V 2 cos 2 r1 V 1 cos 1 = M c (*) 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 ( r1 V 1 cos 1 r 2 V 2 cos 2 = M n Phng trnh (**) lp cho mt dng nguyn t chy trong BXCT, m rng cho ton dng chy trong ton BXCT ta thay Q = q v M = M n v nhn hai v ca (**) vi vn tc gc ta c: Q ( V 1 . r1 . .cos 1 V 2 . r 2 . .cos 2 ) = M . ; Mt khc, ta bit r1 . = U1 ; r 2 . = U 2 ; v M. = N = g . Q . H . T rt ra:1 (4-2) ( V1 U1 cos 1 V 2 U 2 cos 2 ) g 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 thc, do vy c tn tht thu lc trong BXCT v ct nc thc t Hth ch cn bng H, vi l hiu sut thu lc (Hth = H - H = H). Vy (4-2) vit li l: 1 H = ( V1 U1 cos 1 V 2 U 2 cos 2 ) . T y rt ra phng trnh c bn g dng khc, dng cho turbine thc t: 1 ( V1 U1 cos 1 V 2 U 2 cos 2 ) = (4-3) gH H =

Phng trnh (4-3) do vin s Eule 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 IV-1), theo phng trnh (4-3) th hiu sut ln nht ca BXCT c c khi V2U2cos2 = 0. V ct nc ang xt khng i, vn tc V2, U2 khng th bng khng do vy ch c th cos2 = 0 hay 2 = 900. Nh vy iu kin chy ra li nht l vc t vn tc V2 thng gc vi vc t vn tc U2, tc l iu kin chy ra thng gc hay iu kin "php tuyn ca ra". Tuy nhin qua nhiu th nghim chng t rng thc t nn chn 2 < 900 mt t tch s V2U2cos2 = 0,2gH th hiu sut turbine cao hn, v khi 2 < 900 th dng chy sau khi ra 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): Nc t vi phun bn vo cnh go theo cc tia trn, sau khi ra khi vi phun, ton b nng lng dng tia tr tn tht u bin thnh ng nng vi vn tc V 0 = 2gH , khi n go, tia nc c tch ra hai phn bng nhau v chy vo hai na go dng

43

cong ellipsse, dng nc ri khi cnh go vi vn tc tuyt i V 2 rt nh, cn vn tc theo W 2 gn nh ngc chiu vi V 2 . Nu b qua tn tht ma st gia nc v go th W1 = W 2 . im vo (1) v im ra (2) cch trc mt khong gn nh nhau, do vy m U1 = U 2 = U . Da vo tam gic tc ca vo v ca, thnh trong (4-3) s l: (*) V 1 U1 cos 1 = V1 U ; V 2 cos 2 = U 2 + W 2 cos 2 = U + W cos 2 = U + ( V1 U ) cos 2 (**) Thay (*) v (**) vo (4-3) ta c phng trnh c bn (4-4) ca turbine xung kch go: 1 (4-4) U ( V1 U ) ( 1 cos 2 ) = gH 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 = 180 0 . Nhng v nu 2 = 180 0 th phng ca W 2 trng vi phng U 2 , nh vy dng nc cnh sau s p ngc pha sau cnh trc lm gim mmen quay ca BXCT, do vy ly 2 = 176 0 177 0 .IV. 3. LUT TNG T CA TURBINE V CC I LNG QUY DN CA TURBINE

Cng tc thc nghim m hnh v hin trng c tc dng b sung tin cy 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 yu cu , ngi ta thu nh kch thc turbine cn ch to thnh turbine tng t, gi l turbine m hnh. Tin hnh th nghim m hnh v v ra cc ng c tnh turbine, t thng qua cc quan h tng t vi turbine m hnh phc v cho vic nghin cu, thit k, ch to turbine mi. m bo tin cy gia kt qu nghin cu trn m hnh p dng cho turbine thc t cn phi c nhng 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: D1M D 2M b 0 M (4-5) = = = = const D1T D 2T b 0T Tp hp cc turbine ng dng v hnh hc c gi l cc turbine cng kiu.2. iu kin tng t v ng hc iu kin hai turbine tng t v ng hc l s phn b vn tc ti cc im tng ng trn dng chy ca hai turbine cng kiu phi tng t, ngha l t l gia cc vn tc tng ng phi bng nhau, tam gic tc phi ng dng:

44

V M UM WM (4-6) = = VT UT WT 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, lc qun tnh ...) tc dng ln cc phn t tng ng ca dng chy phi t l. Trong l V. l thuyt tng t ngi ta thng dng cc chun s: Ry nn (Re = ), Frt (Fr = p V2 V ), Struchan (Sh = ) v le (Eu = ) lm cc iu kin tng t. g. l n. l . V 2 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 tnh, chun s Sh bng nhau s bo m tng t v lc qun tnh, cn chun Eu l kt qu ca hai dng chy m bo tng t v Re, Fr. Trong thc t th nghim my thu lc cho thy khng th no m bo c iu kin 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 hng ch m bo 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. 3. 2. Cc quan h ca hai turbine tng t

thnh lp cc cng thc tng t i vi cc turbine tng t, trc tin ta 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 khi BXCT theo hng php tuyn, ngha l phng trnh c bn c dng tl gH = U1 V 1 cos 1 . Mt khc theo tam gic tc v lng gic ta c: W1 U1 V1 = = sin 1 sin ( 1 1 ) sin 1

U1 sin 1 U1 sin 1 do vy: V1 = v: W1 = ; do vy ta c: sin ( 1 1 ) sin ( 1 1 ) tl gH = U1 V 1 cos 1 =

2 U1 sin 1 cos 1 sin ( 1 1 )

T y rt ra:

U1 =

sin ( 1 1 ) 2 cos 1 sin 1

2g tl H = K u

2g tl H

(4-8)

tng t ta cng rt ra c cc tc sau:

45

V1 =W1 =

sin 1 2 cos 1 sin ( 1 1 )

2g tl H = K v

2g tl H

(4-9)

sin 2 1 sin ( 1 1 ) 2 sin 1 cos 1 sin 2 ( 1 1 )

2g tl H = K W

2g tl H , (4-10)

Cc h s K u , K v , K w 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): D1M . n M U M = K uM 2g H M tlM = 60 D1T . n T . U T = K uT 2g H T tlT = 60 ch lm vic cng gc th K uM = K uT , v vy nu lp t s cho hai vnn M D1T H M tlM (4-11) = nT D1M H T tlT 2. Quan h v lu lng Lu lng nc chy qua BXCT t l vi tit din t (F) ca BXCT v vn tc tng i (W) v c k n hiu sut dung tch (q). Vy vit cng thc tnh lu lng cho hai turbine m hnh v turbine thc s l: qM . Q M = F M . W1M = F M . K WM . 2g. H M . tlM

tc trn ta c:

qT . Q T = F T . W1T = F T . K WT 2g. H T . tlT i vi turbine cng kiu th t s tit din F t l vi bnh phng ng knh, ngha D2 F l 1M = 1M , lp t s lu lng ta c: 2 F1T D1T2 Q M D1M H M qT tlM = (4-12) 2 QT D1T H T qM tkT 3. Quan h v cng sut Cng sut ca turbine m hnh v thc c tnh nh sau: N M = 9,81 Q M H M M lp t s gia hai cng sut v thay t s lu lng N T = 9,81 Q T H T T theo cng thc (4-12) ta c quan h v cng sut: 2 N M D1M H M H M M qM tlM (4-13) = 2 NT D1T H T H T T qT tlT

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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 cng thc tng t ca turbine thu lc. Qua th nghim m hnh cc thng s turbine m hnh bit, dng cc cng thc tng t 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: n M D1T H M (4-14) = n T D1M H TQM QT =2 D1M 2 D1T

HM HT HM HT

(4-15) (4-16)

2 N M D1M H M = 2 NT D1T H T

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 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 v cng sut ca mt turbine 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 ( thng l D M nh hn 1m), vi ct nc lm vic no H M v o ra cc cc vng quay n M , lu lng Q M ... 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 D M = 1m, ct nc H M = 1m' ' theo nh ngha th n M = n1 , Q M = Q1 , 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: n D1 ' (4-17) n1 = H

' Q1 =

Q2 D1

H

(4-18)

' 2 ' (4-19) N 1 = 9,81 Q1 H H D1 Nh vy cc turbine tng t nhau th c cng mt i lng quy dn. Trong thit k turbine, nu chn c mt m hnh no c ng knh D1M = 1m , ' ' ' H M = 1m v cc i lng quy dn n1 , Q1 , N 1 th ta c th xc nh cc thng s ca turbine cn thit k theo cc cng thc sau: ' 2 Q = Q1 H D1

' n1 H n= D1' 2 N = N 1 D1 H ' 2 H = 9,81 Q1 D1 H

(4-20)H

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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, kh nng tho nc, ng ti so snh cc h turbine vi cc kiu BXCT khc nhau, trong ngnh ch to my thu lc thng s dng i lng vt l gi l vng quay 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). 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 n M = n S , H M = 1m , N M = 1 mlc, v c cc i lng D M ... 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: 2 2 D1M 1 1 1 N M D1M H M H M , thay H M = 1m v N M = 1 ta c ; = 2 = 2 N D1 H H N D1 H H

rt ra:

D1 = D1M

N H H

(*)

T cng thc (4-14) vit li theo quy c ta c: D1 1 nS n M D1T H M = , thay n M = n S v H M = 1m , ta c: = n n T D1M H T D1M H ra:

, rt

nS = nnS = n

D1 D1MN

H

thay (*) vo ta c:

(4-21) H4 H Trong cng thc (4-21): n (v/ph), H (m), N (mlc), nS (v/ph). Nu thay th n N nguyn ca N l (kW) th n S = 1167 , (v/ph) (4-22) , H4 H Ta cn c th tnh h s t tc theo cc thng s quy dn v tng t; dng cng thc (4-22), vi n tnh theo cng thc (4-20), ta c: ' n1 H ' ' 2 ' (4-23) , 9,81 Q1 D1 H H = 3,65 n1 Q1 n S = 1167 H4 H D1 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, n khng i i vi mt kiu turbine, nhng n khng phi l vng quay thc ca turbine. Mi 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 ng knh v cc thng s H, Q, N. V vy ngi ta cn dng t tc nS vic trong vic 48

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 snh cc turbine theo kiu t tc ch c th tin hnh trong iu kin chng lm vic cng mt ch . Thng 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.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 vn khc nhau. ph thuc vo ct nc v ng knh BXCT. S d c s khc nhau ny v trong cng thc chng ta tnh gn ng b qua cc t s hiu sut, do vy b qua s khc nhau v tn tht gia hai turbine tng t do tnh phc tp v cng cha c cch tnh chnh xc cc tn tht ny. Trong thc t xc nh hiu sut ca turbine thc thng phi dng n cc cng 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: D max T = 1 ( 1 max M ) 5 1M (4-24) D1T Khi ct nc H > 150 m: D H max T = 1 ( 1 max M ) 5 1M 20 M (4-25) D1T HT 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: R iT = 1 ( 1 iM ) + ( 1 ) 6 eM (4-26) R eT Trong (4-26) l s phn trm hiu sut, n ph thuc vo ch lm vic ca turbine, kh tnh ra c, ngi ta chn gn ng theo iu kin lm vic ti u ca turbine l R eM D1M H M = 0,5 v dng chung cho mi ch lm vic. Cn = . R eT D1T H T 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 TURBINEV. 1. M HNH VT 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 bo ba iu kin tng t v chun s Raynon. xc nh cc c tnh nng lng v kh thc ca turbine, cn xy dng nhng h thng th nghim. H thng th nghim bao gm nhng b phn chnh sau: - 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. Nc qua p trn xung b di v c bm ln 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 = 1,343 h 2,47 (l/s) chnh xc hn c th o Q bng phng php th tch, tc l dng thng ong.

50

o ct nc H bng ng o p ni ring b thng lu v b h lu khi mc nc 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 tm hoc dng my 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 a0 = const, v gc t cnh khng i (i vi turbine cnh quay) = const, ta iu chnh van kho trn ng ng p lc ca turbine. ng vi mi m van kho ta o c thng s: ct nc H, s vng quay n, 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, Nh ca cc im ng vi mi m kho, tnh hiu sut 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 thng v h lu ng kn khng thng vi kh tri v ct nc th nghim do my bm to ra. Hnh (5-2) l mt s ca h thng th nghim kn. H thng gm ngun to p bm 1, van kho 12, nc vo bnh cao p 13, trn ng p lc t thit b o lu lng 11, nc vo bnh n nh vn tc 8, 9 trc khi vo turbine 4, ri theo ng x xung 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.

51

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 Vic th nghim nng lng tin hnh vi cc m a0 = const v cc gc t ca cnh BXCT = const (i turbine cnh quay) c tin hnh theo trnh t v ni dung tng t tin hnh i vi h thng h. y ch trnh by cch th nghim kh thc. Ni dung ca th nghim kh thc trn h thng th nghim kn nhm v c quan h gia hiu sut v h s kh thc ng vi cc m a0 (v ) hng s. Kt qu o c quan h = f() tnh ton v v c cc ng ng h s kh thc trn ng c tnh tng hp chnh ca turbine. Phng php th nghim kh thc c tin hnh trn h thng kn. Sau khi tin hnh th nghim c tnh nng lng th c th nh ra cc ch cn thit phi tin hnh xc nh c tnh kh thc ti cc ch , c th l xc nh h s kh thc ca cc ch . V d cn xc nh h s ch A no ( c a0, , HA, QA, nA, NA) ta iu chnh kho 12 trn ng p lc c c cc thng s HA, QA, nA, NA . Sau , cho bm chn khng 3 lm vic , o p sut trong b h lu 2 c gi tr p sut chn khng P2 no b 2. H s kh thc tnh c theo cng thc: P2 P bh Hs (5-1) = HA HA HA Trong (5-1): Pbh l p sut ho hi ng vi nhit nc th nghim; HS - chiu cao ht ca turbine th nghim. Tng ng vi trng thi A ta cng tnh c A theo cng thc chung:

52

=

N h 102. M. = 100% .Q . H N

(5-2)

trong cng thc (5-1): M = P.l (kGm); = 1000 kG/m3, Q (m3/s), H (m ct nc). Nh vy ng vi mi gi tr ca p sut chn khng P2 do my bm chn khng to ra v nhit ca nc, ta c c mt tr s tnh theo cng thc (5-1) v theo cng thc (5-2). Gi nguyn ch A, thay i chn khng P2 bng cch thay i ch lm vic ca my bm chn khng 3, ta c mt lot cc cp quan h gia v . lp quan 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 c vo th (hnh 5-2,b) xc nh h s kh thc ti hn KP (im k) ch A. Thay i ch khc, theo cc quy trnh trn lp li. Th nghim kh thc i hi mt nhiu cng sc v kinh nghim mi bo m chnh xc.V. 2. NG C TNH CA TURBINE ng biu th quan h gia cc thng s ca turbine gi l ng c tnh ca turbine. C hai loi ng c tnh: c tnh n v c tinh tng hp. Cc ng c tnh n biu th quan h gia cc cp hai thng s mt; cc ng c tnh tng hp biu th 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 ng 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 quan h N, , a0 = f(Q), hoc quan h Q, , N = f(a0), trong iu kin: n = const v ct nc H = const (hnh 5-3). Cc quan h ny biu th cc thng s dng khng th nguyn tnh theo phn trm. Qua cc ng trn cho php ta c nhng nhn xt cn thit i vi turbine: - Trn ng c tnh cng tc cng sut (hnh a): khi = 0 v N = 0 th Q v a0 vn khc khng, v rng mun pht ra c mt cng sut hu ch no th cn phi c mt lu lng khng ti tng ng vi m nh nht no khc phc cc tn tht nht nh trong turbine. Mt khc ta thy hiu sut ln nht khng ng vi cng sut ln nht, m 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

53

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 cng tc ca cc loi turbine - Turbine go c hiu sut max nh nht, nhng ng c tnh thoi nn c vng lm vic vi hiu sut cao c ni rng; - Hiu sut max cu turbine tm trc v turbine cnh qut ln nht trong cc loi turbine. Tuy vy nhng ng ny ca turbine tm trc tng i dc nn vng lm vic c hiu sut cao b gim, cn ng ca turbine cnh qut th rt dc nn vng 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.

54

l/s

Hnh 5-5. Cc ng c tnh vng quay v c tnh ct nc.3. ng c tnh ct nc ng c tnh ny biu th quan h gia cc thong s Q, N, ca turbine theo ct nc H. Ct nc ca turbine lun thay i trong qu trnh vn hnh. Trn th ta thy: 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 khc nhau. Cn lu lng 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 s ng thi tham gia vn hnh v thay i. V vy cn c ng c tnh biu th cc thng cng tham gia vn hnh. ng c 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 ng c tnh tng hp chnh c lp ra t th nghim m hnh ca mt turbine mu i din cho mt kiu turbine, t kt qu th nghim m hnh , s dng cc cng thc tng t v quy dn tnh ton v ra cho mt turbine c ng knh D1 = 1m, lm vic vi ct nc H = 1m. Do vy ng ny dng cho mi turbine c kch thc khc nhau nhng cng mt kiu .ng c tnh tng hp ch yu biu din cc

55

thng s turbine thng qua hai bin l vng quay quy dn n1 v lu lng quy dn Q1, n gm cc h ng sau (hnh 5-6):

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 (xem hnh 5-6,c). - T ng c tnh ca TB go (hnh 5-6,b), ta thy cc ng ng m a0 c thay 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 vi 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

56

c m rng. T thy rng khng nn cho turbine cnh qut m nhn phn ph ti thay i nhiu, v vi ch lm vic turbine cnh qut lm vic vi hiu sut thp. Cc ng ng h s kh thc ca turbine cnh quay c tr s ln hn nhiu 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 vy trong vic chn thng s turbine ny cn ch m bo yu cu . 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 chn ch lm vic ch turbine thc 2. ng c tnh tng hp vn hnh 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 Htk th khng th pht ra c cng sut nh 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

57

gip ch ngi vn hnh xc nh cc ch lm vic ca turbine, xc nh cc thng s ti cc ch lm vic, cho php xc nh kh nng pht ra cng sut turbine. ng c tnh tng hp vn hnh cn biu th dng to H ~ Q (hnh 5-7,b) . V. 2. 3. ng c tnh ca nhm t my Trong thc t vn hnh TT khng ch c mt turbine lm vic m c nhiu t my (turbine + my pht) cng lm vic, do vy phi xy dng ng c tnh tng hp vn hnh cho nhiu t my. Khi cc ng ng hiu sut phi t hp cc ng hiu sut turbine, hiu sut my pht c cc ng ng hiu sut ca mt t my. Sau xy dng ng ng hiu sut ca nhm t my. Di y l v d v ng c tnh cng tc ( = f(N) ca ba t my (hnh 5-8,a) v ng tng hp vn hnh ca trm c 3 t my (hnh 5-8,b). 1. ng c tnh cng tc ca nhm t my ng c tnh cng tc ca 1 t my biu th quan h gia hiu sut v cng sut ca t my 1m = f (N) (ng I). v ng quan h 2m = f (N) ca hai t my ging nhau ta nh ra cc tung cn honh N xc nh bng cch ly honh mt t my nhn vi 2 ( ng II).Vi 3 t my ging nhau nhn honh mt my vi 3 (ng III). Vi nhm n t my ta cng v theo cch trn. Hnh 5-8,a l l ng c tnh cng tc ca nhm c ba t my ging nhau: - Khi ph ti yu cu N N1 th cho chy mt t my; - Khi ph ti yu cu N1 < N N2 t my 1 v 2 cng lm vic song song l ti u; - Khi ph ti yu cu N > N2 th c ba t my cng lm vic th ti u. V vy ng c tnh cng tc ca nhm t my l ng bao trn 0-1-2-3-4. T ng c tnh nhm t my ta cng nhn ra rng cng m nhn ph ti thay i nh nhau, nu ch lp mt t my cho trm th tuy hiu sut max ca n cao hn cc max tng my cng nhn ti, tuy vy vng lm vic c hiu sut cao ca mt my hp hn, cn vng lm vic ca nhiu t my s cao hn. iu ny rt c ngha i vi trm m nhn phn ph ti thay i nhiu. 2. ng c tnh tng hp vn hnh ca nhm t my ng c tnh tng hp vn hnh ca nhm t my ging nhau c xy dng trn c s ca ng c tnh tng hp vn hnh ca mt t my bng cch cho trc mt 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 hp vn hnh l 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. ng c tnh ca nhm t my.V. 3. XY DNG NG C TNH TNG HP VN HNH Phn V. 2. chng ta bit mt s ng c tnh ca turbine. Trong ng c tnh tng hp chnh l ng gc ca mt kiu turbine, n c v ra t th nghim m hnh, do cc c quan thit k v ch to turbine thc hin v cung cp. i vi lnh vc la chn v s dng turbine cn i su hn v hiu qu ca tnh ton nng lng c lin quan n turbine c chn, do vy chng ta cn bit cch xy dng ng c tnh tng hp vn hnh ca mt turbine c th. S liu bit trc gm: Ct nc lm vic t Hmin n Hmax, ct nc thit k HTK ca turbine thc; Cng sut nh mc ca turbine v ca my pht in; ng knh tiu chun ca turbine thc D1; Vng quay ng b ca t my n ca turbine thc; ng c tnh tng hp chnh ca turbine m hnh c ng nh D1M. Sau y l ni dung v cc bc tnh ton v xy dng ng c tnh vn 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: T = M + (5-3)

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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'1, cng da vo ch lm vic ti u hiu max ' ' ' ' ' 1 ) v n1 = n1M + n1 ; nu chnh cho mi ch lm vic: n1 = n10M ( M max 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 ' n1 = ( n D1): H min ' ' ' n1M = n1 n1' 2 N = 9,81 Q1 D1 H 3 / 2 min

Hiu chnh

Htk ' n1 = ( n D1): H tk ' ' ' n1M = n1 n1' 2 N = 9,81 Q1 D1 H3/ 2 tk

Hmax ' n1 = ( n D1): H max ' ' ' n1M = n1 n1' 2 N = 9,81 Q1 D1 H3/ 2 max

M 1

2

Q'1 3

N 4

Q'1 5

N 6

Q'1 7

N 8

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 ' n1 = ( n D1): H min ' ' ' n1M = n1 n1' 2 N = 9,81 Q1 D1 H 3 / 2 min

Htk ' n1 = ( n D1): H tk ' ' ' n1M = n1 n1' 2 N = 9,81 Q1 D1 H3/ 2 tk

Hmax ' n1 = ( n D1): H max ' ' ' n1M = n1 n1' 2 N = 9,81 Q1 D1 H3/ 2 max

1

2

M 3

4

Q'1 5

N 6

M 7

8

Q'1 9

N 10

M 11

12

Q'1 13

N 14

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Ct 1: Tra trn ng c tnh tng hp chnh; Ct 2: tnh nh trnh by nhng ly giao im vi cc gc , 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. Vi nhiu tr s cho trc ta s v ra nhiu ng ng hiu sut = f (N, H)2. Xy dng ng hn ch cng sut

ng hn ch cng sut trong ng c tnh tng hp vn hnh c hai nhnh do turbine v my pht hp thnh, chng ct nhau ti tung ct nc thit k Htk (im A) trn hnh (5-9,c). ng hn ch cng sut my pht l ng thng ng c N TB N lm = honh l N mp = . ng hn ch cng sut turbine c th l cong mp so may 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 ( N mp , H tk ) , cn xc nh thm im B ( N B , H min ) ri ni hai im A v B li theo ng thng l n D1 ' c. T n1 = , k ng thng nm ngang n gp ng hn ch H min' cng sut 5% v tra c Q1 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 hai cch tnh. y trnh by cch tnh ca nh my ch to turbine ngh, cho rng: 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: n D1 NA ' ' v Q1A = suy ra Q'1A' n1tk = 2 9,81 A D1 H 3 / 2 H tk tk 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 NB, lm cc bc sau: + V ni suy ng ng m a0max (hnh 5-10,b), ng ny ct ng ngang n'1M ng vi ct nc Hmin ti im B' v ni suy ra B'M v Q'1, tnh ra B ' 2 + Tnh ra N B = 9,81. B . Q1B . D1 . H 3 / 2 . Nh vy xc nh c im B; min + 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 ca cc ct nc trn to N ~ Q1' (hnh 5-10,c) da trn kt qu tnh ton bng 5-1 , hoc 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 , ng thi cng tra c Q'1 tng ng. C Q'1 tra ra cng sut N tng ng vi ct nc trn (hnh 5-10,c). Ghi s liu trn vo cc ct t 1 - 4 v tnh 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.

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Bng 5-3. Bng tnh xy dng ng ng cao ht Hmin Htk Hmax ' = ( n D ): H ' = ( n D ): H ' n1 n1 n1 = ( n D1): H max 1 min 1 tk ' ' ' ' ' ' ' ' ' n1M = n1 n1 n1M = n1 n1 n1M = n1 n1 k = 1,05 - 1,10 k = 1,05 - 1,10 k = 1,05 - 1,10 Q'1 N HS kH 1 2 3 4 5 6 ... ...

T kt qu ca cc tnh ton nh trnh by trn v ln cng to N ~ H ta xy dng c ng c tnh tng hp vn hnh cho mt turbine c th (hnh 5-7,a).

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Chng VI.

CHN KIU LOI V CC THNG S CA TURBINE THU LC

La chn t my thu lc (turbine, my pht in) l phn vic tin hnh khi tnh ra cc thng s Thu nng (Nlm, cc ct nc). La chn turbine ng, hp l chng nhng v mt kinh t c li m cn to iu kin tt cho t my c ch tiu vn hnh cao, an ton. Sau y l nhng ni dung c bn trong vic chn turbine thu lc.VI. 1. VN CHUN HO TURBINE V PHM VI S DNG CT NC CA CC LOI TURBINE VI. 1. 1. Vn tiu chun ho turbine khai thc sng sui phc v cho vic pht in mt cch ch ng v c hiu qu, ngoi vic lp quy hoch Thu nng c d kin xy dng trm thu in, vic tin hnh ch to thit b p ng nhu cu khai thc thu in l vic phi tin hnh ng b. V ngun thu nng c tnh a dng; cc v tr xy dng trm thu in c ct nc, lu lng v cng sut khng ging nhau, do vy i hi cn c nhng kiu, nhng h loi turbine khc nhau. Nu thit k v ch to thit b n chic cho tng trm s dn ti gi thnh cao, thi gian ch to lu ... gim nh cng vic ny, cc n v thit k ch to turbine tnh ton, th nghim v a ra nhng ti liu thng nht v cc kiu turbine c quy cch v tiu chun ho. l danh mc turbine (cn gi l gam turbine). Da vo nhng s liu quy chun ny, nh thit k ch to turbine s thit k ch to ra nhng turbine mi; ngi chn turbine s la chn c turbine m h cn vi thng s thch hp. Ngnh ch to turbine ca ta hin cn cha th c iu kin lp ra danh mc turbine cho mnh, chng ta ang dng turbine ca nc ngoi, phn ln l turbine Lin x c v Trung quc, m ch yu da vo danh mc turbine ca Lin x. Danh mc turbine c lp cc dng: - Bng tra phm vi s dng v cc s liu tnh ton c bn ca BXCT, lp c cho turbine phn kch (bng 6-1); - Biu phm vi s dng ca cc kiu turbine (hnh 6-1, 6-2, 6-3, 6-4 cho turbine phn kch v cc biu 6-5, 6-6 cho turbine xung kch). Trn biu phm vi s dng ca mi kiu BXCT l mt hnh bnh hnh gii hn bi ct nc Hmin, Hmax v cng sut gii hn Nmax, Nmin. Gii hn cng sut ca mt kiu BXCT c xc nh bi ng knh BXCT D1max v D1min thch hp. Dng cc biu ny chn kiu BXCT thch hp vi ct nc v cng sut cho. Ngy nay i vi turbine va v ln thng da vo tnh nng kh thc cho php theo quan im kinh t v bn c hc ca cnh BXCT chn phm vi s dng ca BXCT turbine. i km mi kiu BXCT cn c biu ring ca n (hnh 6- ) c th tra ra ng knh D1, vng quay n v chiu cao ht hS ( cao = 0 ) ca turbine kiu .

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Bng 6-1. Phm vi s dng v cc thng s ca turbine phn kch Vng quay qdn Loi turbine n'1 n'1 tnh ton ti u Lu lng qdn Q'1min 2010 1850 1710 1430 1240 1100 1040 940 1370 1250 1030 650 420 280 200 150 1100 900 850 725 600 500 Q'1max 2250 2130 2040 1940 1700 1400 1240 1150 1400 1370 1250 1030 650 420 280 200 13500 1100 1000 750 750 600 H s m hnh

Phm vi ct nc Hmin- Hmax Turbine hng trc cnh quay 3 10 CQ10/592 165 5 15 CQ15/510 150 10 20 CQ20/661 138 15 30 CQ30/587 125 20 - 40 CQ40 115 30 - 50 CQ50/642 110 40 - 60 CQ60/642 106 45 - 70 CQ70/5A 103 Turbine tm trc 30 - 40 TT45/123 75 40 - 75 TT75/128 73 70 - 115 TT115/697 68 110 - 170 TT170/741 67 160 - 230 TT230 62 220 - 310 TT310 60 290 - 400 TT400 58 380 - 500 TT500 57 Turbine hng cho cnh iu chnh 30 - 40 HC60 -1 120 40 - 60 HC60-1 100 60 - 90 HC45-1 90 90 - 120 HC45-2 85 120 - 160 HC30-1 80 160 - 200 HC30-2 75

vi Q'1min1,14 0,84 0,68 0,505 0,4 0,325 0,27 0,23 0,23 0,16 0,097 0,06 0,047 0,04 0,035 0,03

vi Q'1max1,4 1,0 0,835 0,745 0,68 0,505 0,40 0,36 0,27 0,243 0,168 0,10 0,065 0,048 0,042 0,036

180 160 152 140 130 120 112 107 78 74 72 69 67 65 62 60 120 110 95 90 85 80

0,2 0,16 0,14 0,1 0,07

Danh mc turbine phn kch trc ng c ln ca Lin x dng c hin nay gm c 8 n 9 kiu BXCT turbine cnh quay v 8 kiu BXCT turbine tm trc. Cc thng s thu lc v thng s kt cu ca cc kiu u c ghi trong danh mc turbine (bng 6-1) trn. c trng cu turbine turbine c k hiu bi cc ch v s sp xp theo th t nht nh, gi l nhn hiu turbine. Cch k hiu ca Lin x nh sau: - Hai ch u biu th h turbine (PO - tm trc; p - cnh qut; - cnh quay ... ) - Phn s vit tip theo: t s l ct nc ln nht (Hmax) / mu s l s hiu ca kiu turbine m hnh (turbine c khng ghi phn s m ch ghi s hiu ca kiu TB m hnh) - Hai ch tip theo l: phng thc lp trc ( B - trc ng, - trc ngang) v loi bung turbine ( M - bung xon kim loi, - bung xon b tng, - bung hnh ng, O - bung h); - Phn con s cui cng biu th ng knh tiu chun D1 (cm) ca BXCT.

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V d 1: Cch ghi nhn hiu turbine loi mi: 30/587 - B - 500 l turbine cnh quay, ct nc ln nht Hmax = 30m, s hiu BXCT m hnh l 587, lp trc ng, bung xon bng b tng, c ng knh tiu chun BXCT D1 = 500 cm. ( c trng hp nhn khng ghi loi bung turbine th nhn hiu ghi l 30/587 - B - 500 ); V d 2: Cch ghi nhn hiu ca ca turbine loi c: PO123 - M 100 (loi c khng ghi ct nc ln nht). y l nhn hiu turbine tm trc, s hiu BXCT m hnh l 123, lp trc ngang, bung xon bng kim loi, ng knh BXCT D1 = 100 cm. Nhn hiu turbine go c k hiu gm hai phn: - Phn u ghi theo th t sau: ch h turbine go (KB), phng thc lp trc (B trc ng, - trc ngang), ng knh BXCT (cm), s lng BXCT lp trn mt trc; - Phn th hai sau du gch ngang ghi theo th t: ng knh tia dng nc (mm), s vi phun lp trn BXCT. V d: KB 125 x 1 - 140 x 2, c ngha l: turbine go trc ngang, ng knh tiu chun BXCT D1 = 125 cm, ch c mt BXCT, ng knh tia dng l 140mm, c hai vi phun trn mt BXCT. Ghi nhn hiu ca cc nc tng t nhng khc ch ci, tng ng sau: H lai turbine K hiu bng ting Vit nam Lin X T.Quc Nc khc H turbine: ZD Pr Turbine Cnh qut CC p Cnh quay CQ ZZ K Tm trc TT PO HL F Cho trc CT Go G KB QJ P Tia nghing N H T XK hai ln X2 B Cch lp trc: Trc ng D B L V W H Trc ngang N Kiu bung turbine: Bung h H O M ng T Z Xon kim loi K M J Xon b tng B H Ghi ch: K hiu ting Vit nh trn l mi d kin, cha chnh thc.

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Hnh 6-1. Biu phm vi s dng ca turbine phn kch ln.

Hnh 6-2. Min s dng cc turbine phn kch

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Hnh 6-3. Min s dng cc kt cu ca turbine phn kch

Hnh 6-4. Biu tng hp h loi turbine trung bnh v nh

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Hnh 6-5. Biu tng hp h loi turbine xung kch va v nh

Hnh 6-6. Biu h loi ring ca turbine xung kch hai ln

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VI. 1. 2. Phm vi s dng ct nc ca cc loi turbine Ngy nay vic s dng turbine ln v trung bnh, mt cch gn ng thng da vo tnh nng kh thc (xc nh ct nc ln nht ca mi kiu turbine theo iu kin gn ng: H = (10 - HS) / ) v bn c hc ca thit b qua nc turbine. Ngi ta chn turbine da vo phm vi s dng ct nc nh sau: - Turbine hng trc thng c dng vi ct nc H = 1,52 n 80 m, ring turbine hng trc cnh kp H = 30100 mt; - Turbine tm trc : H = 30550 m , ph bin H = 30350 m; - Turbine cnh cho : H = 30150 m; - Turbine go: H = 2002000 m; Ngy nay, phm vi s dng ct nc c m rng l nh nhng thnh tu t c trong lnh vc ch to turbine: Trc kia turbine hng trc, m c bit l turbine cnh quay thng c s dng vi ct nc H =1550m; vi ct nc ny kch thc v trng lng my ln, gi thnh tng. Vic tng ct nc s dng ca turbine cnh quay ln H = 5080 m nhm mc ch tng hiu sut bnh qun ca t my trong trng hp ph ti v ct nc thay i nhiu. Ct nc H = 315 m c thay th bng vic s dng turbine capxun c t tc cao v r hn. Nhc im ca turbine hng trc trc ng l c c tnh kh thc km hn turbune tm trc, do vy turbine cnh quay cng b hn ch khng nn lm vic ct nc cao. Kinh nghim thy rng khi chiu cao ht HS khng nh hn - 6 n 8 m th h cnh quay c li v kinh t. H turbine cnh cho quay ra i nhm kt hp nhng u im ca h cnh quay nh hiu sut bnh qun tng i cao khi ct nc v ph ti giao ng ln v c im ca turbine tm trc l c c tnh kh thc v su lp turbine tng i nho. Hin nay phm vi s dng ca turbine cnh cho c nng ln H = 50200 m. Turbine tm trc ngy nay c ct nc s dng m rng ln H = 30700 m, c th thay th phm vi ct nc H = 300700 m m turbine go thng m nhn. Trong phm vi ny nn dng turbine go ch khi ph ti thay i nhiu, nc c nhiu tp cht v iu kin xy dng khng cho php t turbine su qu ln. cc iu kin kin khc nn s dng turbine tm trc v n c hiu sut ln hn ca turbine go t 2 n 3%. Ring i vi turbine nh, do iu kin xy dng cng nh kh nng ch to m pm vi s dng ct nc cng c khc, v nh turbine go c th s dng vi ct nc chng H = 100m; turbine tm trc c th s dng ct nc H = 380 m; turbine cnh qut H = 216m ... VI. 2. NHNG VN CHUNG KHI CHN TURBINE i vi ngi thit k trm thu in, vic chn thit b c in ni chung v chn turbine ni ring, l da vo cc ti liu turbine do nh my ch to cung cp chn turrbine thch hp vi cc thng s thc t ca trm. Trong trng hp khng c turbine thch hp th c th tnh ton ra cc thng s c bn turbine ca trm t

71

hng nh ch to turbine thit k v ch to turbine mong mun. Trong phn ny ch cp n cch chn turbine sn xut hoc thit k c trong h loi turbine. VI. 2. 1. Ti liu gc chn turbine Khi la chn turbine cn bit cc s liu gc sau: - Cc ct nc ca trm: ln nht Hmax, nh nht Hmin, ct nc thit k Htk; - Cng sut lp my ca trm hoc cng sut ca t my; - Cao trnh mc nc thng, h lu nh my ng vi cc ct nc; - Mc nc h lu ng vi cc lu lng tho qua nh my. Cc ti liu ny do c quan kho st thit k thu in cung cp. Cng vi nhng ti liu trn chn turbine cn phi c nhng ti liu v turbine sau: - Bng tng hp h loi hoc biu tng hp h loi turbine; - ng c tnh tng hp chnh ca kiu turbine; - H s kh thc cu turbine cc ch lm vic ca kiu turbine; - ng c tnh quay lng ... . VI. 2. 2. Ni dung v vn chung khi chn turbine 1. Ni dung chn turbine Ni dung chn turbine theo yu cu thit k trm bao gm nhng vic sau: a. Xc nh s lng t my; b. Chn h, kiu turbine v kiu t my; c. Xc nh ng knh tiu chun BXCT D1; d. Xc nh s vng quay ng b ca turbine; e. Tnh cao ht cho php [HS] v cao trnh t turbine 2. Nhng vn chung khi chn turbine Kt qu la chn