CHNG 1 : KHI NIM C BN V C S THIT K

KHOA C KH NG TU

B MN NG LC DIESELTP BI GING H THNG NG LC

NGNH MY TU THY M 18.02.10

C1/HLTBG18.02.10

CHNG 1 KHI NIM C BN V C S THIT K1.1.KHI NIM C BNH thng ng lc l mt h thng thit b bao gm thit b y tu, thit b ng lc ph bo m nng lc hot ng ca tu v thit b m bo i sng, sinh hot ca thuyn vin.

Tng hp cc thit b trn c th phn chia thnh cc h thng sau:

1.1.1.H thit b y tu

H thit b y tu l mt h thng cc thit b c nhim v bo m tc , phng hng cho tu hot ng, bao gm cc b phn sau:

ng c chnh: Nhim v ca ng c chnh l to nn lc y tu. ng c chnh c th l ng c hi nc, tua bin hi, tua bin kh, diesel, ng c piston t do, my pht in v ng c in.

Thit b y: Thng dng cc loi thit b y nh gung quay, chong chng, chn vt, thit b y kiu pht... Trong cc loi thit b y, chong chng l loi thit b y c dng ph bin nht.

Thit b truyn ng: Thit b truyn ng c nhim v tip nhn cng sut t ng c chnh truyn cho thit b y to nn lc y tu. Thit b truyn ng thng bao gm: h trc tu thy, b gim tc, cc thit b ni trc, cc thit b chuyn mn truyn dn in v cc thit b phc v cho thit b truyn ng.

Ni hi chnh: Ni hi chnh c nhim v cung cp hi nc lm cng cht cho my hi, tua bin hi v cc my mc ph.

Thit b ti cng cht: Nhim v ca thit b ti cng cht l ti hi nc, kh chy n ng c chnh, ng c ph, bao gm cc h thng ng hi, ng kh chy...1.1.2.Thit b phThit b ph c nhim v cung cp cng cht cho tu lc hnh trnh, tc nghip, sinh hot v d tr, bao gm cc b phn sau:

T my pht in: C nhim v cung cp in cho ton tu, nu h ng lc ca tu l in truyn ng th phi c h thng my pht v ng c in ring.

H thng kh cao p: Nhim v ca h thng kh cao p l cung cp khng kh cao p cho tu dng khi ng ng c, dng trong cng tc sa cha, t ng hoH thng bao gm my nn kh, bnh cha khng kh cao p, ng ng dn khng kh v cc loi van gim p

H thng nc cao p: Dng trong sinh hot, v sinh (v bao gm c h thng cha chy bng nc cao p).

Ni hi ph: Ni hi ph c nhim v cung cp hi nc c p sut thch hp cho cc h thng hm, sy, si m, nc dng trong sinh hot hng ngy. Hi nc ca ni hi ph khng dng lm cng cht cho ng c chnh.

1.1.3.Thit b m bo an ton trn tu Thit b m bo an ton c nhim v phng chng nhng s c xy ra trn tu, m bo cho tu hot ng c an ton. Bao gm nhng h thng thit b sau:

H thng rt nc, x nc bn, h thng dn tu v cn bng tu.

Phng chy v cc s c khc, bao gm: h thng khng kh lnh; h thng hi x; h thng phun sng; h thng nc phng chy; hi phng chy; phng chy bng ha hc, h thng kh tr

Thit b phng ng c c nhn v tp th.

Thit b sa cha t xut gm sa cha trn tu, phn di nc cc ph tng v vt liu thay th.

1.1.4.Thit b sinh hotL nhng thit b m bo i sng cho thuyn vin v hnh khch trn tu, bao gm: h thng thng gi, si m, v sinh, lm mt, lm lnh v iu ha khng kh

1.1.5.Thit b tuThit b tu b bao gm thit b neo, li, thit b chng buc bc d hng, thit b cu sinh v cc thit b qun dng c bit.

Nu xt v tnh cht v nhim v ca cc thit b th thit b c gii trn tu thy c phn chia thnh by loi ln sau:

C gii ng lc ( cung cp cng cho tu) bao gm ng c chnh, ng c ph, ni hi my pht in, ng c in.

C gii cng tc bao gm thit b y tu, bm, my nn.

Thit b truyn ng gia c gii ng lc v c gii cng tc bao gm h trc, hp s, cc khp ni, cc loi dy in, ng ng

Thit b d tr du nhn, du nhin liu, khng kh v nc bao gm cc bu lc, b phn phn ly v cc thit b lng, lc khc.

Thit b ti cng cht bao gm ng ng v cc loi van.

Thit b trao i nhit bao gm cc b phn hm nng, lm mt1.2.CC CH TIU NH GI H NG LC

1.2.1.Ch tiu k thut

1Ch tiu cng sut

y l mt trong nhng ch tiu c bn v quan trng ca h ng lc, tnh theo cng sut nh mc ca ng c chnh. Ch tiu cng sut bao gm:11Ch tiu cng sut tuyt i

c biu th bng cng sut ca ng c chnh Ne, [hp hoc kW].

12Ch tiu cng sut tng i

c biu th bng bo ha cng sut

(11)

Trong :

Ne cng sut nh mc ca ng c chnh, [hp];

D lng chim nc ca tu, [tons].

Ch tiu tng i biu th cng sut cn thit cho mt tn lng chim nc ca tu. Ngoi hai loi ch tiu trn, i khi ch tiu cng sut cn c nh gi bng nghch o ca h s hi qun:

(12)Hoc l:

(13)Trong :(Ne tng cng sut ca cc my chnh, [hp hoc kW].

Bng di y thng k mt tr s ca cc ch tiu cng sut trn nh sau:Bng 11: Bng thng k cc ch tiu cng sutDng tu(M1/C

Tu du, tu hng0,1 ( 0,41/270 ( 1/370

Tu hng tng hp0,3 ( 0,91/180 ( 1/300

Tu container tc cao1,0 ( 1,51/220 ( 1/320

Tu khch bin ln0,8 ( 1,51/180 ( 1/260

Tu cnh ngm20 ( 60

2Ch tiu kch thc

21Ch tiu kch thc tuyt i

Biu th cc kch thc ca bung my: chiu di bung my LER, [m]; din tich mt sn bung my FER, [m2]; th tch bung my VER, [m3].22Ch tiu kch thc tng iBiu th thng qua i lng bo ha kch thc bung my

(14)Trong :

L khong cch gia 2 ng vung gc li v mi ca tu, [m].

Ngoi ra, ch tiu tng i cn c th hin thng qua cc bo ha sau:

(15.1)

(15.2)

(15.3)Cc i lng bo ha k trn th hin kh nng tn dng khng gian bung my trong b tr thit b v kh nng to cng sut ca h ng lc.

3Ch tiu trng lng

Trn tu, trng lng ca nhng phn bt buc phi lp t cng nh cng tt, c bit l trng lng ca trang tr ng lc. nh gi, ngi ta a ra cc ch tiu nh sau:31Ch tiu trng lng tuyt i GHT Trng lng ton b ca h ng lc khi cha k n lng du, nc trong my chnh v lng d tr (cn gi l trng lng kh ca h ng lc).

G'HT Trng lng ca h ng lc khi chun b khi ng,

(16)

Trong :

M trng lng cng cht dng cho vic khi ng.Vi h ng lc tuabin hi:

(17)Vi h ng lc diesel:

(18) G"HT Trng lng h ng lc trc khi khi ng, c k n trng lng d tr:

(19)

32Ch tiu trng lng tng i

(110)

(111)

(112)Trong :

Ne cng sut nh mc ca ng c chnh, [hp];

D lng chim nc ca tu, [tons].

1.2.2.Ch tiu kinh t

1Ch tiu tuyt i

Ch tiu kinh t tuyt i c nh gi bng cc i lng di y:

Tng chi ph nhit cho h thng: QHT[kCal/h] Tng chi ph nhin liu cho h thng:BHT[tons/h]2Ch tiu tng i Chi ph nhit tng i:

(113) Chi ph nhin liu tng i:

(114)i khi ch tiu kinh t c nh gi theo cng sut ca thit b y NP, khi c cc ch tiu sau:

(115)

(116)

1.3.PHN LOI TRANG TR NG LC. YU CU I VI H THNG NG LC TU THY1.3.1.Phn loi trang tr ng lc

Vic phn loi trang tr ng lc tu thy thng cn c vo ng c chnh v phng thc truyn ng. Trang tr ng lc tu thy tri qua qu trnh pht trin cho ti hin nay gm cc loi hnh:

Trang tr ng lc tuabin hi truyn ng hp s; Trang tr ng lc tuabin hi truyn ng in; Trang tr ng lc my hi nc trc tip truyn ng; Trang tr ng lc diesel trc tip truyn ng;

Trang tr ng lc diesel truyn ng hp s;

Trang tr ng lc diesel truyn ng in; Trang tr ng lc hn hp (my hi v tuabin hi hn hp, my hi v diesel hn hp, tuabin kh hn hp); Trang tr ng lc tuabin hi cao p truyn ng hp s; Trang tr ng lc tuabin kh truyn ng hp s; Trang tr ng lc piston t do tuabin kh; Trang tr ng lc nguyn t.1.3.2.Yu cu i vi trang tr ng lc tu thyTrang tr ng lc l mt trong nhng b phn quan trng cu thnh h thng nng lng ca tu thy, c im v yu cu ca trang tr ng lc quyt nh c trng ca ton b con tu.

Cc yu cu i vi trang tr ng lc tu thy hin i: S chuyn ha gia cc dng nng lng (nhit nng, c nng, ha nng) phi t c tnh kinh t cao; Thit b n gin; Lm vic tin cy; Kch thc v trng lng nh; Gi thnh r, chi ph khu hao thp; Ch ph vn chuyn thp; Tui th h hp (thi gian lm vic lin tc gia 2 ln sa cha ln)

Thng thng t c ton b cc yu cu trn l rt kh v khng thc hin c, bi v mt s cc yu cu trn l mu thun ln nhau. Do vy, ty thuc vo mc ch thit k m t c mt s yu cu nht nh. Nhng yu cu trn thng c xem xt da trn cc cn c di y.1Cn c theo c tnh chong chng v v tu

11Yu cu v cng sut

xc nh cng sut ca trang tr ng lc hay cng sut ca ng c chnh, trc tin phi xem xt n sc cn ca ton tu. Tu hnh trnh trn bin, sc cn ca tu c quan h vi hnh dng v tu, nhm b mt ca v, cc phn nh v phn ngm nc ca tu, tc tng i ca tu so vi dng nc, tnh hnh n nh ca tu, tnh hnh sng gi trn mt bin...Nh vy, khi xc nh c gi tr ca sc cn R (kG) v tc tng i ca tu v (m/s) th cng sut ko c ch ca trang tr ng lc s c tnh nh sau:

(117)

Ch : Cng thc (11) ch ng trong trng hp nc tnh v gi khng qu cp 3.

Cng sut cn thit cung cp cho chong chng c xc nh:

(118)

Trong :

hiu sut ca chong chng.

Cng c th xc nh cng sut ca chong chng theo cng thc Hi qun:

(119)Trong :

D lng chim nc ca tu, [tons];Cw h s Hi qun c xc nh theo tu mu.

Cng sut cn thit (l thuyt) ca ng c chnh c xc nh:

(120)

Trong :

sp hiu sut ca ng trc.Cng sut dng cho la chn ng c chnh c xc nh:

(121)

i vi tu thy, cng sut v tc thng c quan h nh sau:

(122)

Khi tc ca tu n nh, lc y ca chong chng sinh ra s cn bng vi sc cn ca tu; thng thng n = 3. Nu tc tu thp th n < 3, v ngc li nu tc tu ln th n > 3. Cn A, B l h s t l ph thuc vo cc thng s ca chong chng, tc v phn ngm nc ca tu,...

Trong thc t, mi ng c v mi chong chng u c cc ng biu din mi quan h gia cng sut v vng quay ring (cn gi l cc ng c tnh). Khi thit k phi cn c vo im phi hp gia chong chng v ng c m ti ng c t c hiu sut cao nht. Ngoi im ra ng c u lm vic ch khng ti, mmen xon v p sut c ch trung bnh ca ng c khng t tr s cao nht. ng c c th qu ti trong qu trnh khai thc, mc qu ti ca ng c thng t tr s 110%Ne. Nu tr s qu ti ln hn na, vng quay ca ng c s tng ln (khong 5%), mmen xon trn trc s tng ln kh r rt. Do , nu tng vng quay ca ng c s lm cho mmen xon ca ng c vt qu xa tr s cho php, ng sut nhit v nht l ng sut c gii tng ln rt ln.

Cng sut ca ng c chnh c la chn ph thuc vo loi tu, cng dng v lng chim nc ca tu. c trng cho vn ny thng dng cng sut tng i biu th. Gi ( l cng sut tng i:

(123)

Trong :

D Lng chim nc ca tu, [tons]12Yu cu v ch tiu kinh t ca tu

Cng dng ca tu khc nhau th yu cu v trang tr ng lc cng khc nhau. C loi tu ch yu cu trang tr ng lc n nh mt ph ti nht nh, nhng cng c loi tu i hi trang tr ng lc phi thay i cc ch ph ti khc nhau. iu ny phn nh l yu cu v ch tiu kinh t cc loi trang tr ng lc c khc nhau. Trong thit k trang tr ng lc i hi phi t c ch tiu kinh t ch thit k, ngoi ra cc ch ti khc ch tiu kinh t cng i hi t c mt cch tng i.

c trng cho cc ch tiu kinh t ca trang tr ng lc chnh l sut tiu hao nhin liu ca ng c chnh v sut tiu hao nhit lng cho ton b h thng nng lng.

Vi nhng h ng lc ch c mt ng c chnh, c tnh hiu sut ca ng c quyt nh c tnh kinh t ca trang tr ng lc. Yu cu mt ng c m hiu sut khng bin i theo ph ti l khng th c, c bit l khi ph ti thp hiu sut gim xung rt nhanh. khc phc iu ny, thng thng trong thit k phi s dng cc phng n sau:

Dng nhiu ng c quay mt chong chng.

Dng nhiu ng c quay nhiu chong chng.

Dng chong chng bin bc hoc phng thc truyn ng in.

2Cn c vo nng lc lm vic c lp (hoc cn c vo trng lng v kch thc tu)

Nng lc lm vic c lp ca tu hay kh nng hon thnh nhim v cng tc ca tu c th hin tnh kinh t, trng lng v kch thc ca tu. Mi loi tu khc nhau u c nhim v v tnh nng ring. Tuy nhin, cc tnh nng ca tu phi c da trn lng chim nc nht nh ca n.

21Yu cu i vi trng lng

Lng chim nc ca tu c th chia ra lm 4 thnh phn chnh: trng lng v tu, trng lng trang tr ng lc, trng lng ca cc thnh phn d tr v trng lng ca hng ha, hnh khch. Khi vi mt lng chim nc nht nh, mt trng lng thnh phn no tng ln th cc thnh phn khc bt buc phi gim xung. Do vy, trng lng ca trang tr ng lc c nh hng trc tip n tnh nng nhim v ca tu. Tu c lng chim nc nh nhau, nhng tc hnh trnh khc nhau, cng sut khc nhau th trng lng ca trang tr ng lc s khc nhau.

c trng cho trng lng ca trang tr ng lc ngi ta a ra khi nim trng lng tng i K1. y chnh l t s gia trng lng trang tr ng lc vi lng chim nc ca tu.

(124)

Trong :

W trng lng ca trang tr ng lc, [tons];

D lng chim nc ca tu, [tons].

(125)

Trong :

g1 trng lng ring ca trang tr ng lc, [kg/hp].

C th xc nh:

(126)

Biu din di dng tnh theo %:

(127)

Qua thng k cho thy tu c cng sut tng i ( ln th trng lng tng i ca trang tr ng lc K1 cng ln, khi trng lng hng v d tr s gim xung.

22Yu cu i vi kch thc ca bung my

Phn ln my mc trn tu c tp trung trong bung my. V vy kch thc bung my phi thch hp cho vic lp t cc thit b v thun tin cho vic bo dng, s dng v sa cha ngay ti bung my; ng thi cn phi xt n iu kin lao ng v m bo an ton cho th my khi lm vic. Nu ch da trn nhng yu cu th kch thc bung my cng rng cng tt. Nhng khi th kch thc khoang hng s gim xung, khng gian dng vo vic b tr cc chc nng khc s nh i, v tnh nng lm vic ca tu c th b nh hng. biu th vn ny ngi ta dng i lng bo ha bung my. C hai loi bo ha: bo ha th tch v bo ha din tch.

bo ha th tch l cng sut ca trang tr ng lc trn mt n v th tch bung my.

bo ha din tch l cng sut ca trang tr ng lc trn mt n v din tch bung my.

bo ha bung my (mt b tr thit b, my mc) cng cao th iu kin lm vic, sa cha cng khng c li.

23Yu cu i vi lng d trLng d tr ca tu l do bn thn tu mang i tip tc hnh trnh trong mt thi gian nht nh, y chnh l nng lc hot ng c lp ca tu. i vi trang tr ng lc, lng d tr chnh l nhin liu, du bi trn, nc ngt lm mt. Nhin liu d tr cng nhiu th nng lc hot ng c lp cng ln. Nhng trng lng nhin liu li l mt trong nhng thnh phn trng lng ca tu, v do vy lng nhin liu tng th cc thnh phn trng lng khc s gim xung.

Lng nhin liu d tr ca tu c xc nh s b nh sau:

(128)

Trong :

G lng nhin liu d tr, [kg];Ne cng sut ca trang tr ng lc, [hp];ge sut tiu hao nhin liu ca trang tr ng lc, [kg/hp.h]; thi gian thc hin hnh trnh c lp ca tu, [h].

Nu dng s phn trm ca lng chim nc biu th lng d tr nhin liu, c:

(129)

T (129) nhn thy mun tc hnh trnh khng thay i ((), nng lc c lp ca tu khng thay i () m gim bt c lng d tr nhin liu (G) th ch c cch l gim sut tiu hao nhin liu ca trang tr ng lc. Hoc l d tr c mt lng nhin liu nht nh, tc hnh trnh khng i v nng cao nng lc hnh trnh th cng ch c cch l gim bt sut tiu hao nhin liu (ge).

3Cn c theo tnh hnh mt bin

Do tnh cht an ton ca tu, khi tu hnh trnh phi ch n nhng yu cu sau:

trng thi tu lc dc, lc ngang cc thit b vn phi lm vic c bnh thng, do yu cu cc thit b ny phi c lp ghp tht cht vi v tu.

H thng bi trn phi c thit k sao cho khi tu lc vn m bo a c du n bi trn nhng ni cn thit.

Cc kt du nhn v nhin liu phi c b tr v thit k sao cho vn m bo lm vic c bnh thng trong khi tu nghing, lc.

Tt c cc thit b phi hot ng v iu chnh c d dng mi trng thi ca tu.

ng c chnh phi c thit b an ton (b iu tc gii hn vng quay ln nht) trong trng hp qu ti v vng quay.

Cc thit b c s vng quay cao phi c lp theo phng dc tu phng mmen quay ln.

ng c chnh phi c la chn sao cho c cng sut d tr khc phc sc cn trong lc cn thit.

Ngoi ra cn mt s yu cu khc cho cc trang tr ng lc ring bit.

4Cn c vo yu cu s dng

Trang tr ng lc tu c mt s yu cu v s dng nh sau:

Thi gian khi ng ngn v nhanh.

Phi pht huy c ton b cng sut trong mt thi gian ngn.

Cc thit b c gii phi lm vic an ton trong bt c iu kin no c a ra trong iu kin thit k.

Cc thit b phi c tnh c ng cao, thao tc thun tin, t c tnh tin cy cn thit.

i vi ng c chnh, sau khi o chiu quay phi pht huy c cng sut trong thi gian ngn v lm vic n nh.

Trang tr ng lc phi t gy ting n v chn ng i vi v tu v m bo c chc nng lm vic ca tu.

5Cn c vo yu cu ca Quy phm v Cng cThit k trang tr ng lc phi c c quan c thm quyn xt duyt (ng kim) trn c s cc iu lut quy nh i vi thit k, ng mi tu thy v phng tin ni. Do tt c cc vn thit k trang tr ng lc u phi tha mn cc iu lut trong cc quy phm v Thit k v Gim st ng mi, cng c v An ton sinh mng v trang thit b trn bin, cng c v Phng nga nhim mi trng bin.1.4.LA CHN TRANG TR NG LC V NG C CHNH

1.4.1.Loi hnh trang tr ng lc

Thit k tu dn dng hay qun dng, vic chn trang tr ng lc l mt vn phc tp v quan trng. Khi la chn hnh thc trang tr ng lc phi ng thi gii quyt hai vn , l: quyt nh kiu loi my chnh v phng thc truyn ng. Vic quyt nh s lng chong chng c lin quan mt thit n cc vn trn, iu ny nh hng n thc cht v hnh thc trang tr ng lc tu thy ( y phi xt n c tnh k thut ca ng c v phng thc truyn ng).

Vic la chn trang tr ng lc phi cn c vo nhim v th thit k (nhng yu cu thit k ch yu). Cn c vo nhim v th, tin hnh xt cc iu kin c th nh: cng dng, nhim v ca tu (i vi tu dn dng) hay kh nng tc chin (i vi tu qun dng); vng hot ng; tnh nng v tc ; cng sut h ng lc; phn khoang v kch thc bung my; tin cy; tnh kinh t; cc ch tiu nh gi v thit k; lut p dng v cc yu cu khc.1.4.2.ng c chnhMt trong nhng iu kin quan trng nht v cng l iu kin c tnh cht quyt nh l vn nhin liu v kh nng cung cp ng c (hay kh nng t mua ng c).

Trong pht trin trang tr ng lc, ng c diesel ang c s dng rng ri, ch yu l v cc l do sau:

Th nht, ng c diesel tng p v b gim tc c dng mt cch rng ri, thch hp cho vic s dng ng c c cng sut ln vi kch thc v trng lng nh; mc t ng ha cao; d dng cho phi hp v lp t.

Th hai, diesel s dng nhin liu nng mt cch c hiu qu, m bo cho chi ph vn ti gim xung mt cch thch ng. Th ba, do tin b ca khoa hc v cng ngh, ng c diesel ngy cng c ci tin v hin i, gim ng k sut tiu hao nhin liu kt qu nng cao c hiu sut ca h thng ng lc. iu lm cho ng c diesel ph hp hn vi trang tr ng lc ca cc tu hin ti.V k thut v cng ngh ch to my hi nc, cc kiu my hi c c thay th dn bng kiu my hi c thng s hi nc cao, nng cao tnh kinh t. Tuy nhin, vic s dng cc loi hnh trang tr ng lc hi nc l rt hn ch ch yu l do hiu sut thp, mc t ng ha v hin i ha, kh nng p ng i vi h thng ng lc hin i... Chnh v vy, loi hnh h thng ng lc hi nc ch p dng trong nhng trng hp c bit.

Ngoi ra vic s dng ng c phn lc, tuabin kh trong trang tr ng lc tng mt cch ng k, song phm vi p dng cha c rng ri.

Tm li, khi thit k trang tr ng lc, tt nht l tin hnh so snh cc phng n, tm u khuyt im ca tng phng n, sau chn ly phng n ti u nht, ph hp vi iu kin thc t s dng.

1.5.H THIT B Y. TNH TON CNG SUT V TC 1.5.1.c im ca h thit b y tu

H thit b y tu l mt h thng cc thit b c nhim v bo m tc , phng hng cho tu hot ng, bao gm cc b phn sau:

ng c chnh: Nhim v ca ng c chnh l to nn lc y tu. Thng thng dng ng c hi nc, tuabin kh, diesel, ng c piston t do, my pht in v ng c in lm ng c chnh.

Thit b y: Bao gm cc loi thit b y nh gung quay, chn vt, chong chng, thit b pht...; trong chong chng l thit b c s dng rng ri nht.

Thit b truyn ng: Nhim v l tip nhn cng sut t ng c chnh truyn cho thit b y to nn lc y tu. Thit b truyn ng bao gm h trc tu thy, b gim tc, cc thit b ni trc, cc thit b chuyn mn truyn dn in v cc thit b phc v cho thit b truyn ng.

Ni hi chnh: Nhim v ca ni hi chnh l cung cp hi nc lm cng cht cho my hi, tuabin hi v cc my mc khc.

Thit b ti cng cht: Nhim v l ti hi nc, kh chy n ng c chnh, ng c ph. Thit b ny bao gm cc h thng ng hi, ng kh chy...

1.5.2.Sc cn v cng sut y1Sc cn ca tu v cc thnh phn sc cnKhi tu chuyn ng, sc cn ca tu c th c phn tch theo cng thc sau:

(130)Trong :

R sc cn ton b ca tu;RW thnh phn sc cn sng;

Rp thnh phn sc cn hnh dng;

Rf thnh phn sc cn ma st;

Rd thnh phn sc cn ph.Sc cn sng RW, c xc nh theo cng thc:

(131)Trong :

(W h s sc cn sng;

( mt cht lng, [kg/m3];

v vn tc tu, [m/s];

( din tch mt t ca tu, [m3].H s sc cn sng (W c tra theo th, ph thuc vo tr s Frut ca tng loi tu. Trong th, nhng vng li lm l kt qu ca s trng hp bt li v c li ca hai h sng mi v sng li. Khi thit k nn trnh nhng vng li ca th v khi nm trong vng ny, sc cn sng s tng rt nhanh.

Sc cn hnh dng Rp, c xc nh theo cng thc:

(132)Trong :

(p h s sc cn hnh dng. (p c th tnh theo cng thc:

(133)Vi:

S din tch sn gia, [m2];LR chiu di vut nhn phn ui, [m].Sc cn ma st Rf, c xc nh theo cng thc:

(134)Trong :

(f h s sc cn hnh dng. (f c th tnh theo cng thc gn ng hoc tnh theo bng.

Theo Schocnherr, (f c tnh:

(135)Trong (135): Re h s Reynolds.

Theo Prandtl Schlichting:

(136)Thc t nh hng ca hnh dng v tu n sc cn ma st c tnh bng h s iu chnh af nh sau:

(137)Vi = 8,2 ( 5,6 th af nm trong khong 1,04 ( 1,08 (L chiu di tu, B chiu rng tu).

Ngoi ra, cn phi k n nh hng ca nhm ca v ( li lm do cng ngh, ln sng ca tn bao, rong ru, h, r bm vo v) n sc cn ma st ca tu. Tt c nh hng ny c c trng bng h s iu chnh af.Sc cn ph Rd, c xc nh theo cng thc:

(138)Trong :

(d h s sc cn ph.

Sc cn ph bao gm cc thnh phn sc cn sau:

Sc cn khng kh Ra. Nu tnh mt cch chnh xc, Ra c tnh theo cng thc:

(139)Trong :

(a h s sc cn khng kh, l kt qu nghin cu m hnh trong ng dng;(a khi lng ring ca khng kh, (a = 0,125 [kg.s2/m4];Fa din tch hnh chiu phn trn mt nc ca tu ln din tch sn gia, [m2];va vn tc tng i ca gi, c tnh theo cng thc:

(140)Vi:

vs vn tc ca tu, [m/s];w vn tc ca gi, [m/s];(a gc tc dng ca gi so vi trc gia ca tu, ((a=0 nu gi thi ngc).

Sc cn ca nhng phn li, nhng phn li ca tu nh: ki hng, ki ng, cc gi trc chong chng, phn li trc chong chng..., c nh hng ti sc cn ca tu. Nu so vi sc cn ton b tu, sc cn ca cc phn li thng nm trong khong:

(141)

v cao nht

(142) Sc cn khc, khi tnh sc cn cn phi k n cc iu kin khai thc ca tu nh hng ti sc cn ca tu: chiu su lung lch, iu kin sng gi thin nhin,...

Nh vy c th xc nh sc cn ton b ca tu theo cng thc:

(143)2Tnh sc cn ca tu bng phng php PapmielC nhiu phng php tnh sc cn tu, mi phng php u c iu kin p dng ring ph hp vi loi tu nht nh. Di y nu ra phng php tnh sc cn thng dng v n gin nht, l tnh theo phng php Papmiel.

Phm vi s dng ca phng php:

( = 0,35 ( 0,8

; ; Fr < 0,9

(( h s bo th tch; L chiu di tu; B chiu rng tu; T chiu chm tu)

Papmiel da trn c s th nghim m hnh v th cc loi tu thc, ra phng php tnh cng sut ko ca tu:

(144)Trong :

V th tch chim nc, [m3];L chiu di tu ng nc thit k, [m];vs vn tc tu, [knots];( h s tnh ton c xc nh theo cng thc:

(145)

L ( 100 m, th ( = 10

x h s ph thuc vo s lng ng trc chong chng, cho trong bng 12.Bng 12: H s xt n s lng ng trcS lng ng trc chong chng ZH s x

Z = 1x = 1,000

Z = 2x = 1,050

Z = 3x = 1,067

Z = 4x = 1,100

h s thon ca tu, c xc nh:

(146)B chiu rng tu;( h s bo th tch .Cp h s PapmielH s Cp c xc nh theo th Papmiel, ph thuc vo thng s vs', c tnh nh sau:

(147)Sau khi xc nh c N0, sc cn tu c tnh theo cng thc:

(148)Trong :

v vn tc tu, [m/s]3Cng thc Hi qun

Trong tnh ton s b, ngi ta thng p dng cng thc Hi qun tnh cng sut ko (hoc cng sut c ch) ca tu. Cng thc Hi qun c dng:

(149)hoc:

(150)Trong :

C0 h s Hi qun cho cng sut ko;Ce h s Hi qun cho cng sut c ch;vs vn tc tu, [knots].Cng thc (149) v (150) c th cho kt qu chnh xc nu chn tu mu c hnh dng ging nhau v cng tr s Fr, nhng thc t kh t c yu cu trn.1.5.3.Tc tuT mc 1.5.2. cho thy sc cn l hm ca tc tu, R = f(vs). Trn c s tnh ton, tin hnh xy dng th sc cn cho tu vi tng tc tu khc nhau.

Vi ng c chnh cho, da trn cng sut nh mc ca ng c chnh, xc nh cng sut truyn n chong chng (hay cng sut s dng). Cng sut truyn n chong chng lun nh hn cng sut ca ng c v c s tn hao cng sut trn ng trc; i lng ny c xc nh nh sau:

(151)

vi:

(152)Trong :

k h s d tr cng sut ca ng c chnh;(sp hiu sut ca ng trc;(sp1 hiu sut ca gi trc;

(sp2 hiu sut ca hp s, hp gim tc;

(sp3 hiu sut ca thit b ni trc, khp ni. i vi gi trc lc y, hiu sut vo khong (sp1 = 0,97. i vi hp s, hiu sut vo khong (sp2 = 0,96 0,98. i vi khp ni trc thy lc hay in t, hiu sut vo khong (sp3 = 0,94 0,95.Cng sut truyn n chong chng cng c th xc nh bng cng thc:

(153)Trong :

Mp mmen xon truyn n chong chng, [kG.m];np s vng quay ca chong chng, [v/p].i vi truyn ng in th cng sut truyn n chong chng c tnh:

(154)Trong :

(e1 hiu sut chung i vi truyn ng in Khi dng in thay i: (e1 = 0,86 ( 0,90. Khi dng in n nh: (e1 = 0,88 ( 0,93.Khi lm vic, chong chng s sinh ra mt lc y l P. Ton b lc y ny bao gm lc y c ch y tu chuyn ng Pe v phn khc phc lc ht ca tu Pt.

(155)Trong :

P lc y ca chong chng;Pe lc y c ch hay lc chuyn ng tu

Pt lc ht;t h s ht.Nh vy:

(156)hay:

(157)Theo Keldvil, tr s trung bnh ca h s ht i vi tu ko c 1 hoc 2 chong chng xc nh theo cng thc sau:

(158)Trong :

C1 = 0,5 ( 0,7, khi c bnh li v trc li thot nc tt sau chong chng;C1 = 0,7 ( 0,9, khi c bnh li v trc li hnh ch nht.( h s dng theo, i vi tu mt chong chng ( = 0,5.( ( 0,1, i vi tu hai chong chng ( = 0,5.( ( 0,16.Theo Papmiel:

(159)Trong :CB h s bo th tch ca tu;V th tch chim nc ca v tu, [m3];D ng knh chong chng, [m];z s chong chng, (tu 1 ng trc z = 1; tu 2 ng trc z = 2).Cng sut ko cn thit i vi tu mt chong chng:

(160)Quan h gia cng sut ko v cng sut y ca chong chng nh sau:

(161)Trong :

( hiu sut cng tc ca chong chng,

(162)T c th tnh:

(163)Kt qu l:

(164)Kt qu t (164) c th xy dng c th lc y c ch theo vn tc ca tu Pe = f(v).Khi tu chuyn ng v cn bng, ton b lc y c ch s cn bng vi lc cn ca tu, tc l:

(165)Do giao im ca hai th sc cn v lc y c ch s cho ta tc tu s b cn xc nh.Khi tnh ton cng sut ca tu ko, chng ta cn phi xt thm sc cn mc ko Z khi tnh cng sut ko.

D tr cng sut ca ng c chnh

Th nht, vic s dng khng ht cng sut trung bnh lc khai thc hoc phi mt lng cng sut dnh cho d tr l l v phi m bo tc tu trong trng hp v tu bin dng, b h bm v han r lm sc cn tng ln.

Th hai, vic quy chun trong quy trnh khai thc cng sut ng c l khuynh hng bo m an ton s lm vic ca ng c diesel tu thy trong thi gian c th ln hn hn nh sa cha.

Th ba, cng sut d tr l cn thit cho ng c v an ton ca phng tin trong trng hp sng gi ln, gp bo hoc tu chy ton tc lc ngc sng,...

Bin son: Nguyn Anh VitTel: (031)3856552 Mobile: 0913.041539Email: anhvietkdt@vnn.vnPage: 1A4 (210 x 297) mm

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