btl bom quat may nen

HUMG 2015

Nguyn Vn Phong_LHD B K57 Page 1

LI NI U

Bm, qut, my nn l nhng my rt quan trng v c ng dng rng ri trong cc

h thng cng ngh. S hot ng ca bm, qut, my nn c nh hng ln n hot ng

ca ton b dy chuyn cng ngh, n mi trng, n qu trnh iu khin, n nng sut

nh my v gi thnh ca sn phm. Chnh v vy vic hiu bit v nm vng nguyn l lm

vic, cu to, tnh ton, thit k, sa cha, lp t v vn hnh cc my bm, qut, my nn l

ht sc cn thit.

Bm, qut, my nn l mt mng rt rng v chuyn su, v vi iu kin thi gian

cng nh yu cu ca mn hc, em xin trnh by s tm hiu khi qut v mt s loi bm,

qut my nn trong cng ngh lc ha du.

I. BM

1.1.1 Khi nim

Bm l my di chuyn dng mi cht v tng nng lng dng mi cht. Khi bm lm

vic nng lng m bm nhn c t ng c s chuyn ha thnh th nng, ng nng v

mt chng mc nht nh thnh nhit nng ca dng mi cht.

Bm l loi my thy lc dng bin i c nng ca ng c thnh nng lng vn

chuyn cht lng hoc to nn p sut cn thit trong h thng truyn dn thy lc.

1.1.2 Phn loi

a. Theo nguyn l lm vic v cu to ca bm

Bm c 3 loi:

1. Bm cnh dn:

Bm ly tm

Bm hng trc

Bm hng cho

Bm xoy

2. Bm th tch:

Bm piston

Bm roto

Bm piston-roto

3. Bm phun tia

b. Theo cng dng

Bm cp nc ni hi

Bm du

Bm nhin liu

Bm cu ha

Bm ha cht

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c. Theo phm vi ct p v lu lng s dng

Bm ct p cao, trung bnh v thp

Bm c lu ln ln, trung bnh v nh

Trong k thut c 3 loi bm c s dng rng ri l bm ly tm, bm hng trc v bm

piston.

1.1.3 Cc thng s lm vic c bn

Bm c 5 thng s lm vic c bn:

Lu lng Q, ct p H, cng sut N, hiu

sut v ct p ht cho php [HCK].

Khi bm lm vic, cht lng t b

ht qua li chn rc theo ng ht i vo

bm. Sau khi qua bm, cht lng c

bm cp cho nng ln chy vo ng y

ln b cha. T b cha cht lng c

phn phi ti cc ni tiu th. Trong h

thng truyn ng thy lc, cht lng sau

khi ra khi bm c p sut cao, qua b

phn phn phi i vo ng c thy lc

thc hin cc chuyn ng ca nhng c

cu lm vic.

S h thng bm

1.2 Bm ly tm

1.2.1 u nhc im

u im c bn ca bm ly tm:

Bm c nhiu loi cht lng nh nc, du, nhin liu, ho cht, k c cc hn

hp ca cht lng v cht rn

Ni trc tip vi ng c in

Loi b c cu chuyn ng kiu bin tay quay, xupap, bu kh

Nn mng nh khng tn nhiu din tch

C th iu chnh rng ri

Phm vi s dng ln v nng sut cao, c th :

- Ct p H t 10 mH2O n hng ngn mH2O

- Lu lng Q t 2 70.000 m3/h

- Cng sut t 1 6000 kW

- S vng quay t 730 6000 v/ph

Kt cu nh gn, chc chn, lm vic tin cy

HUMG 2015


Hiu sut ca bm (bm c cng sut ln) tng i cao so vi cc loi bm khc:

= 0,65 0,90

Ch tiu kinh t tt ( gi thnh tng i r)

Nhc im:

Mi khi ng khng c kh nng ht nc, phi c b phn mi nc

Khng nn to ra p sut qu 7at (v iu kin bt kn)

Hiu sut ca bm (bm c cng sut nh) khng ln lm (theo nh lut thy lc;

ng, rnh cng nh th tr lc cng ln)

Nng sut Q ph thuc vo chiu cao H

1.2.2 Phn loi bm ly tm

1. Theo p sut : Thp, trung bnh, cao. i vi bm p sut thp v va thng lm

mt gung, v vy hay xy ra hin tng x dch gung cng vi trc v hin tng tun

hon cht lng. khc phc hin tng ny ngi ta lm gung kp c cnh 2 pha, nn

lc chiu trc c cn bng. kh lc chiu trc ngi ta lm bm c nhiu cp c ming

gung t ngc chiu nhau.

2. Theo s lng gung : Bm 1 cp vi p sut thp v va, bm nhiu cp vi p

sut cao.

3. Theo cch dn cht lng t gung vo ng y: gm c bm khng thit b hng

v bm c thit b hng.

4. Theo cch truyn ng c:

Bm trc tip: ni lin vi ng c in hoc my n qua trc ni n hi.

Loi ny c hiu sut cao.

Bm c c cu truyn ng ng (hp tng tc, dy ai, bnh rng kha) c

hiu sut ca thp.

5. Theo v tr ca trc c bm ly tm thng ng, nm ngang.

6. Theo h s cao tc ns

Bm ly tm vn

tc chm

Bm ly tm vn

tc va

Bm ly tm vn

tc ln

Bm cho Bm hng

trc

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D0 - ng knh vo ca ming gung, m

D1 - ng knh trung bnh ca chn cnh gung ming vo, m

D2 - ng knh trung bnh ca chn cnh gung ming ra, m

1.2.3 Qu trnh lm vic

S kt cu bm ly tm

Bm ly tm gm cc b phn ch yu

sau:

1 - Bnh cng tc 2 - Trc bm

3 - B phn dn hng vo

4 -B phn dn hng ra ( cn gi l

bung xon c)

5 - ng ht 6 - ng y

Trc khi cho bm lm vic cn phi

lm cho thn bm trong c bnh cng

tc v ng ht c in y cht lng,

gi l qu trnh mi bm.

Qu trnh lm vic:

Khi bm lm vic, bnh cng tc quay, cc phn t cht lng trong bnh cng tc

di nh hng ca lc ly tm b dn t trong ra ngoi chuyn ng theo c mng dn v i

vo ng y vi p sut cao hn, l qu trnh y ca bm. ng thi li vo ca bnh

cng tc to nn mt vng c p sut chn khng, v di tc dng ca p sut b cha

ln hn p sut li vo ca bm, cht lng b ht lin tc b ht vo bm theo ng ht.

l qu trnh ht ca bm. Qu trnh ht v y ca bm l cc qu trnh lin tc, to nn

dng chy lin tc qua bm. B phn dn hng ra, c dng xon c nn gi l bung xon

c l dn cht lng t bnh cng tc ra ng y c iu ho, n nh v cn c tc dng

bin mt phn ng nng ca dng cht lng thnh p nng cn thit.

1.2.4 Hin tng xm thc

Vng xy xa xm thc

p sut dng cht lng chy qua bm lun

lun thay i v khng bng nhau trong tng

im ring r trn mt ct ca dng chy.

Trong nhng bm thng thng, p sut nh

nht l gn li vo ca bnh cng tc

pha lm ca cnh dn, t c l ch no vn

tc tng i W v ng nng ng vi n

W2/2 t c gi tr ln nht (vng A trn

hnh).

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Nu vng A p sut bng hay nh hn p sut hi bo ho ca ch lng trong bm, th s

xut hin hin tng xm thc. Hin tng ny s lan rng ra cc vng ln cn ca dng

chy. Hin tng xm thc c hi khng ch v n hu hoi kim loi m cn v my lm vic

khi c xm thc s lm gim rt l n hiu sut. Bm lm vic khi c xm thc rt n, rung

mnh v khi cng xm thc ln cao xut hin s va p s rt c hi cho bm.

Nguyn nhn ca hin tng xm thc l:

1. Vn tc cc b ca cht lng tng trong rnh gung.

2. Ca vo hp v c chiu dy ca gung.

3. Tr lc gy ra do mt chi tit khng nhn.

4. p sut v vn tc phn b khng u v lc ly tm.

5. S thay i hng chuyn ng ca cht lng ng ht.

6. Chiu cao ht qu ln.

7. p sut kh quyn qu thp so vi bnh thng.

Bin php khc phc:

Hn ch vn tc cht lng trong dng chy ca bm

ng dng hnh dng tin li cho dng chy v cho mt ct ca bnh cng tc

S dng bm ch gn vi ch tnh ton trc

Mt bin php quan trng trong vic chng xm thc ca bt k loi bm no l

cn c cao ht thch hp, m vi cao ht ny khng xy ra xm thc gi l

cao ht cho php.

1.2.5 Kim tra bm

1. Chn bm ng yu cu k thut, da vo ng c tnh ca bm, trong c

bit ch ng c tnh c bn (H-Q).

2. Cc thit b v ng h o p sut, o chn khng, o in cn c y . Cn lp

van mt chiu ng ht v ng y d dng khi mi v khi ng bm.

3. Trc khi cho bm lm vic phi mi bm

4. Trc khi bm khi ng phi kim tra du m trong bm v ng c, cc mi

ghp bulng, h thng in.

5. Khi khi ng bm, cho ng c quay n nh ri mi t t m kho ng y

(nhng vi bm p sut thp th ngc li, m kho ng y ri mi khi ng nu

khng ng c kh khi ng v d b qu ti).

6. Khi bm lm vic, cn theo di ng h o, ch nghe ting my kp thi

pht hin nhng bt thng x l kp thi.

7. Khi chun b tt my, lm th t ng tc ngc vi khi cho my chy: ng van

ng y trc, tt my sau.

8. Khi bm lm vic cht lng khng ln hoc ln t, cn dng my v kim tra li:

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Cc van hoc kho ng y v ng ht.

Li chn rc c b lp kn hoc ming ng ht khng ng su cn thit

cch mt thong ca b ht.

Bnh cng tc quay ngc (bm in c th b u dy ngc pha).

1.2.6 iu chnh ch lm vic ca bm

im iu chnh

im lm vic ca bm l

giao im ca hai ng c

tnh ca bm v ca h thng

trong cng mt h to .

Qu trnh thay i im lm

vic ca bm theo mt yu

cu no gi l qu trnh

iu chnh.

Khu vc iu chnh

khu vc iu chnh

Ta thy rng mun iu chnh bm th phi

thay i ng c tnh li hoc thay i

ng c tnh bm. Nhng thc t khng

phi c th iu chnh im lm vic v bt

c im no trn ng c tnh ca bm.

V d: Trn hnh v , c mt bm lm vic

trong h thng vi cc ng c tnh nh

c th hin, trong ng c tnh ca

bm c dng li. im T l im gii hn

chia ng c tnh ra lm hai khu vc: bn

phi im T l khu vc lm vic n nh,

cn bn tri im T tu theo v tr ca ng

c tnh li, bm c th lm vic khng n

nh gi l khu vc lm vic khng n nh

ca bm.

Thc nghim chng t rng:

Khng th iu chnh bm trong khu vc khng n nh.

Khi khi ng bm, cn h thp Hli im lm vic ca bm khng ri vo

khu vc khng n nh.

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i vi cc bm quan trng nh bm cao p cp nc cho ni hi (nh my nhit in),

yu cu v ng c tnh ca bm l khng c vng lm vic khng n nh, tc l ng

c tnh c dng dc ng hoc thoi.

V tr ca im gii hn T ph thuc vo g c 2. Gc 2cng nh th khu vc lm

vic khng n nh cng nh.

C 2 phng php iu chnh:

iu chnh bng kha

iu chnh bng kho to nn s thay i

ng c tnh li bng cch iu chnh

(ng hoc m) kho ng y thay i

lu lng ca h thng(khng iu chnh

ng ht v d gy ra hin tng xm thc).

- Khi m kho hon ton ta c im lm vic

A (HA, QA).

- Khi ng bt kho li th tn tht kho s

tng ln (A => B), lu lng ca h thng

gim, ngha l ng c tnh li s thay

i dc hn, trong khi c tnh bm khng

i. Do im lm vic t A chuyn n B

(HB, QB).

=> Phng php ny n gin, thun tin

nhng khng kinh t v gy thm tn tht.

iu chnh bng thay i s vng quay ca trc

bm

Ni dung ca phng php ny l thay i

ng c tnh ri ng ca bm bng cch thay

i s vng quay ca trc bm. im lm vic A

(HA,QA) ng vi s vng quay lm vic nA. Khi

tng s vng quay n nB > nAth ng c

tnh ca bm s khc i trong khi ng c

tnh li khng thay i, im lm vic t A

chuyn n B (HB, QB).

=> Phng php ny dng cho bm c thit b

thay i s vng quay. Phng php ny kinh t

hn so vi phng php trn. Nhng i vi

bm khng c thit b thay i s vng quay lm

vic th phng php iu chnh bng kha thng

dng hn.

i khi ngi ta kt hp c 2 phng php

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1.3 Bm piston

1.3.1 cu to v nguyn l lm vic

Cu to v nguyn l lm vic ca bm piston tc dng n

Bm piston c ko bi ng c, chuyn ng quay ca trc ng c c bin i thnh

chuyn ng tnh tin ca piston 1 trong xilanh 2 nh h thng thanh truyn tay quay vi

hnh trnh S = 2R (R- chiu di tay quay). Hai im B1, B2 ca piston tng i vi hai v

tr C1, C2 ca tay quay. Khi trong bung lm vic 5 cha y cht lng, nu tay quay t v

tr C2 quay theo chiu mi tn th piston di chuyn t B2 v pha tri. Th tch bung 5 tng

dn, p sut p trong gim i v b hn p sut mt thong b cha pa(p < pa). Do cht

lng t b ht qua van ht 6 vo bung lm vic 5, trong khi van y 4 ng. Khi piston

chuyn ng t B2 -> B1 bm thc hin qu trnh ht. Khi tay quay n v tr C1(piston n v

tr B1) th qu trnh ht ca bm kt thc.

Sau , tay quay tip tc quay t C1 -> C2, piston i chiu chuyn ng t B1 -> B2. Th

tch bung lm vic gim dn, p sut cht lng tng ln, van ht 6 b ng, van y 4 m

cht lng chy vo ng y. Qu trnh piston di chuyn t B1 -> B2 gi l qu trnh y.

Nh vy, c mt vng quay ca tay quay th bm thc hin c 2 qu trnh ht, y lin

nhau. Nu tay quay tip tc quay th bm li lp li qu trnh ht v y nh c. Do qu

trnh ht v y ca bm piston gin on v xen k vi nhau. Mt qu trnh ht v y k

tip nhau gi l mt chu k lm vic ca bm.

Kh nng t ht ca bm piston:

Khc vi bm ly tm, bm piston kh ng cn phi mi, bm c th t ht c.

Gi W0 l th tch khng kh ng ht v bung lm vic (khi piston B2). Nu

piston di chuyn n B1 th khng kh gin ra vi th tch ln hn, bng W0+ FS (FS - th

tch xilanh). Cho rng khng kh gin n on nhit, th p sut khng kh lc by gi trong

bung lm vic l p < pa:

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Do p < pa nn cht lng t b ht chy vo ng ht v dng ln c mt cao:

(cha k ti tn tht)

Nu piston tip tc lm vic, cht lng t b ht s dng dn theo ng ht v in y bm.

Khi xem nh bm t mi xong.

u im ca bm piston:

C th to nn p sut ln.

Cu to n gin.

Khuyt im:

Chuyn ng ca cht lng qua bm khng u. Do lu lng ca bm dao ng.

Kt cu ca bm tng i cng knh.

Khi p sut nh hoc trung bnh, thng dng bm ly tm c li th hn. Khi cn p sut cao

hoc rt cao (t 200 at tr ln) v lu lng tng i nh th bm piston chim u th.

1.3.2 Cu to piston, xi lanh v van trong bm piston

Thn bm (xi lanh), piston v van l nhng b phn quan trng nht ca bm. Xilanh

thng c ch to bng thp hoc c bng gang, hoc bng vt liu c bn ha hc cao

nh ferosilic, snh, thp chu axit, v.v Mt trong ca xilanh c gia cng k, t nhn

cao gim ma st. i khi trn b mt trong ca xilanh cn c ph lp ng nht cho

thun li khi sa cha.

Piston c cu to theo kiu a hoc kiu plngi. Piston kiu a c mt a bng

gang hay thp ni vi cn piston. Trn thnh a c lp vi vng m (xecmng) bng d, cao

su, kim loi hay vt liu tng hp (hnh a, b). Plngi c dng hnh tr rng c c bng

gang (nu c ng knh ln), hoc gia cng bng thp (nu ng knh b, nhng p sut

ln). B mt plngi c gia cng nhn hoc bc mt lp ng (hnh c, d, e). Piston kiu

plngi c u im l b mt trong ca xilanh khng cn gia cng k nh kiu a.

Van dng trong bm piston c rt nhiu loi vi cu to khc nhau, nhng loi

thng dng nht l van a v van hnh vnh khn, n van hnh cu (van bi) v van bn l.

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(a): Van a

(b): Van hnh vnh khn

(c): Van bi

(d): Van bn l

Van c ch to bng nhiu loi vt liu nh ng, thp, cao su hay cht do. L xo

ca van c lm bng ng hay thp. Trong bm, van hot ng theo nguyn tc t hnh,

c ngha l m ra di tc dng ca bm p sut cht lng v ng li di tc dng ca khi

lng bn thn, hay lc l xo.

Van c chn cho bm theo tng trng hp c th ph thuc vo c tnh ca cht

lng cn bm v s vng quay ca bm. Nh van a v an bi c dng cho cht lng c

nht cao, c bit van bi dng thch hp khi cht lng c ln cc ht rn (huyn ph), khi s

vng quay nh v nng sut thp. Vi cht lng bn (d lm tc bm) th dng van bn l c

tit din rng.

1.3.2 Phn loi

a. Theo hnh dng piston: 2 loi

Bm piston a: piston c dng hnh a, mt xung quanh ca piston tip xc vi

thnh nn gi l piston gip thnh.

Bm piston tr: piston c dng tr vi ng knh tng i nh, mt xung

quanh khng tip xc vi thnh.

b. Theo s ln tc dng:

Bm tc dng n hay cn gi bm tc dng mt chiu. Trong loi bm ny,

cht lng lm vic v mt pha ca piston. Mt chu k lm vic ca piston ch c

mt qu trnh ht v mt qu trnh y ni tip nhau

Bm tc dng kp, hay cn gi bm tc

dng 2 chiu. Trong loi bm ny, piston

lm vic c hai pha, do c hai bung lm

vic A v B, 2 van ht 1, 4 v 2 van y 2,3.

Trong mt chu k lm vic ca bm c 2

qu trnh ht v 2 qu trnh y (khi bung

A ht th bung B y v ngc li).

Bm piston tc dng 2 pha

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Bm tc dng nhiu ln: c 2 loi

- Bm tc dng 3 ln: Trong mt chu k lm vic (mt vng quay ca trc bm) loi

bm ny c 3 qu trnh ht v 3 qu trnh y. N chnh l do 3 bm tc dng n

ghp li vi nhau, cc piston c dn ng bng mt trc khuu, c chung mt ng

ht v mt ng y. c dao ng lu lng nh nht, cc tay quay c b tr lch

nhau 1 gc 1200

- Bm tc dng 4 ln: n cng l do 2 bm tc dng kp ghp li vi nhau. Tay quay

ca 2 bm t lch nhau 1 gc 900

c. Theo p sut:

Bm p sut thp : p < 10 at

Bm p sut trung bnh: p = 10 ?20 at

Bm p sut cao : p > 20 at

d. Theo lu lng:

Lu lng nh : Q < 15 m3/h

Lu lng trung bnh : Q = 15 60 m3/h

Lu lng ln : Q > 60 m3/h

1.3.3 Khc phc chuyn ng khng n nh ca cht lng trong bm piston

Tc hi ca chuyn ng khng n nh trong bm:

Lm tng tn tht thy lc

Gy chn ng

Nu bm lm vic trong h thng ng di c th xut hin va p thy lc lm hng

cc b phn ca bm v h thng.

Trng hp h thng nhiu bm cng lm vic, c th xut hin hin tng cng

hng bin dao ng ca p sut.

Bin php khc phc chuyn ng khng n nh: 3 bin php

1. Dng bm tc dng hai chiu (bm tc dng kp).

2. Dng bm ghp. Nh phn trn ta thy, h s khng u v lu lng ca cc bm

piston ghp nh hn ca bm tc dng n rt nhiu.

3. Dng bnh khng kh iu ha lu lng v p sut. Bnh khng kh iu ha lu

lng v p sut (gi tt l bnh iu ha ) c kt cu rt n gin. chnh l

nhng bnh cha kn t ngay st trn ng ht v ng y.

Bnh iu ha lp trn ng ht gi l bnh iu ha ht, bnh iu ha lp trn ng y gi l

bnh iu ha y.

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Bnh iu ha ht

Trong cc qu trnh lm vic ca bm,

mt phn cht lng c tch ly li trong

bnh iu ha. Nu kch thc bnh ln

th dao ng cht lng trong bnh s nh.

Hn na trn mt thong ca cht lng

trong bnh lun lun c khng kh v c p

sut chn khng. V th m cht lng chy

t ng ht ln bnh mt cch lin tc v c

th xem nh d ng chy n nh. Chuyn

ng khng n nh ch xut hin trn mt

on t bnh cha n mt piston.

Do lc qun tnh trong ng ht ch xut

hin trn mt on ngn t bnh iu ha n

bm => gim c tn tht nng lng trong

ng ht.

t bnh iu ha trn ng ht cho php:

- Tng thm c chiu cao ht ca bm.

- Tng s vng quay lm vic ca bm.

- Gim c dao ng p sut ca bm trong

qu trnh ht.

Bnh iu ha y

Trong qu trnh y mt phn lu lng ca

bm (phn ln hn lu lng trung bnh) c

tch ly li trong bnh, mc cht lng s dng

ln, nn khi khng kh phn trn ca bnh,

to nn p sut ln. Khi van y ng nh c p

sut ln ca khi khng kh b nn trong bnh,

nn cht lng c tip tc y ra ng y, v

vy dao ng ca lu lng v p

sut trong ng y c gim i, dng chy

iu ha hn. Cng nh bnh iu ha ht, bnh

iu ha y c tc dng lm gim lc qun

tnh trong ng y ca bm piston. Lc qun

tnh ch cn xut hin trn mt on ngn t

bm n bnh iu ha.

bnh iu ha y c tc dng, cn phi bo

m thng xuyn mt lng khng kh cn

thit nht nh trong bnh.

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1.4 Bm hng trc

1.4.1 Cu to v phm vi s dng

a. Phm vi s dng

Bm hng trc c phm vi s dng rt rng ri khi cn lu l ng ln v ct p thp, c th:

Lu lng : Q = 0,1 25 m3/s

Ct p: H = 4 10 mH20

c bit c khi H = 22 m.

b. Cu to v nguyn l

S kt cu bm hng trc

1.B phn dn hng vo

2.Thn bm

3.Bnh cng tc

4.Mc cht lng

5.Trc bm

Kt cu ca bm hng tr c n gin v chc chn. N gm c phn ng v phn tnh.

Phn quay (phn ng) gm bnh cng tc gn lin vi trc. Bnh cng tc hnh khi tr c

gn cc cnh dn mt cong phn b u xung quanh. Thng s cnh dn ca bnh cng tc

t 3 6 cnh. Phn ng yn (phn tnh) l v bm c dng hnh tr rng, pha trong c

cc cnh dn hng v b phn trc. Pha trn b phn dn hng thn bm un cong

tin b tr cc b phn dn ng trc bm.

Trc ca bm hng trc thng c ni trc tip vi ng c in. Khi bm lm vic,

bnh cng tc quay trong mi trng cht lng v do c cc cnh dn mt cong dng cng

xn (cong theo khng gian 3 chiu) nn cht lng c ht vo bm v di chuyn theo

phng song song vi trc vi lu lng ln.

1.4.2 iu chnh ch lm vic

Do cc c im ca ng c tnh ca bm hng trc, khng nn ng kho ng

y v khng nn iu chnh bm bng kho. Trong bm hng trc nn dng cc bin

php iu chnh khc bm c th lm vic vi hiu sut tng i cao.

Thng thng c cc phng php iu chnh bm hng trc sau:

1. iu chnh s vng quay lm vic ca bm, khi c kh nng thay i c s

vng quay lm vic ca ng c.

2. Dng khp ni thu lc cho php thay i s vng quay lm vic ca bm trong

khi s vng quay ca ng c vn khng i.

HUMG 2015


II. Qut

2.1.1 Khi nim

Qut thuc loi my c cnh. Chng c dng bin c nng ca ng c thnh

nng lng di chuyn mi cht v to cho n mt p nng cn thit.

Qut bao gi cng lm vic trong h thng bao gm bnh cha, ng ng ht v

ng ng y. Qut cng vi ng c ko n c gi l thit b qut. i vi qut, do p

sut sau n kh ng ln hn p sut trc n l bao nhiu nn s nn ca mi cht c th b

qua v vic tnh ton qut cng c tin hnh tng t nh vi bm.

2.1.2 Cc thng s c trng

Cc thng s c trng cho s lm vic ca qut l: nng sut (lu lng), ct p, cng sut

v hiu sut.

a. Nng sut

L lng mi cht do qut qut c trong mt n v thi gian. Nng sut cn c gi l

lu lng. Nu lng mi cht c o bng n v trng lng (kG/s, N/s,) th c gi

l nng sut trng lng, k hiu l G.

Nu lng mi cht c o bng n v th tch (m3/s, m3/h, l/s,) th gi l nng sut th

tch, k hiu l Q. Gia G v Q c mi lin h:

Thay trng lng ring bng th tch ring ta c:

b. Ct p

S ca h thng my qut

pI - p sut trn mt cht lng trong bnh ht

p1 - p sut trc u vo qut

v1 - vn tc cht lng u vo

p2 - p sut u ra qut

v2 - vn tc cht lng u ra

y - khong cch gia hai im o ca ng h chn

khng k v ng h p k

pII - p sut trn mt cht lng trong bnh cha

Ct p ca qut l lng nng lng

do qut cung cp cho 1kg mi cht

khi mi cht ny chuyn ng qua

chng. Ct p c k hiu l H.

V mt hnh hc, ct p ca qut

c xem nh chiu cao m

lng cht lng c th nng ln

c do nng lng m chng nhn

c v c o bng mmH2O.

=> Ct p do qut sinh ra ch dng

thng tr lc trn ng ng.

HUMG 2015


c. Cng sut v hiu sut

Trong thi gian qut lm vic, mi cht c nhn t qut mt s nng lng. Nng

lng cung cp lin tc cho dng chy ny do ng c truyn cho trc ca qut.

Cng sut do ng c truyn qua trc qut gi l cng sut trn trc.

Nng lng truyn cho dng cht lng c gi l nng lng hu ch. Nng lng hu ch

trong mt n v thi gian gi l cng sut hu ch.

Cng sut hu ch l:

N = G.

H = .Q.H ; W

Trong :

- c o bng N/m3

G - c o bng N/s

Hay N =

; kGm/s

Trong :

- c o bng kG/m3

G - c o bng kG/s

Hiu sut:

Hiu sut ton phn

2.2 Qut ly tm

2.2.1 Kt cu v mt s chi tit chnh

Qut ly tm c dng vn chuyn cht kh v to nn p sut ton phn khng

qu 1500 kG/m2 (khi = 1,2 kg/m3) v c h s tng p < 1,15. Do p sut b nh vy, s

nn khng nh hng nhiu n s lm vic ca my v tnh b nn ca kh c th b qua.

Bi vy cc c s l thuyt ca qut cng ging nh bm v ch khc nhau rt t v kt cu.

S kt cu qut

1 Trc

2 a chnh ( a sau)

3 Cnh dn

4 a ph (a trc)

5 Mng cnh

6 Thanh truyn ng

7 V qut

8 B qut

9

10, 11 ng ra, ng

vo

HUMG 2015


Kt cu:

Bnh cng tc ca qut c to bi trc 1, c gn cht vi a chnh 2. Cc cnh dn lm

vic 3 c gn cht vi a chnh 2 v a trc 4. a ny m bo cng cn thit ca

mng cnh 5; 6 l thanh truyn ng ca qut. V qut 7 c gn vi b 8 trn c 9

mang trc qut c bnh cng tc 10 v 11 l np kp ca ng vo v ng ra. Bnh cng tc c

cnh dn cong v pha trc s c p lc cao hn bnh cng tc c cnh thng hoc cong v

pha sau khi c cng s vng quay song hiu sut thy lc s thp hn. Trong qut thng

dng bnh cng tc c cnh cong pha trc hoc thng. Cui ng dn ra thng dng on

ng chuyn tip c dng loa tip tc tng p kh sau khi ra khi v.

Nguyn l:

S nguyn l v tnh ton

Dng kh i vo bnh

cng tc qua ng vo

theo hng dc trc, sau

s quay 1 gc 900 v

chuyn ng trong rnh

cnh t tm ra ngoi. Sau

khi ra khi bnh cng

tc, dng kh i vo v

xon c v i ra ng ra.

Cc thng s ca qut: p sut, lu lng qut, Cng sut v hiu sut ca qut.

2.2.2 iu chnh qut

iu chnh lu lng qut, c 3 phng php sau:

iu chnh bng cch thay i s vng quay

iu chnh bng tit lu li vo v ra ca qut

iu chnh bng cc thit b nh hng ca vo.

a. iu chnh bng cch thay i s vng quay

y thay i s vng quay ca qut bng cch thay i s vng quay ca ng c ko n,

hoc khi s vng quay ca ng c khng i th lp thm b phn thay i tc . Trong c

hai trng hp ny, thit b qut phc tp v t thm, v vy cch iu chnh ny ch dng

i vi qut ln. Trong mt s trng hp, mi qut ngi ta dng ng c in . Loi

ng c ny c iu chnh bng cch thay i in tr trong mch ca roto cho php iu

chnh u n s vng quay. Trong giai on hin nay, iu chnh qut bng cch

thay i s vng quay, ngi ta thng dng ng c truyn dn c thit b bin tc.

Phng php ny dng rt kinh t.

HUMG 2015


b. iu chnh bng tit lu

Phng php ny c s dng kh rng ri v n gin. Cch iu chnh tng t nh

trong bm.

c. iu chnh bng cc thit b nh hng ca vo

Ta thy rng nng lng ring m qut cung cp cho dng kh phn ln l do iu kin ca

vo ca bnh cng tc. S xon ca dng kh vo bnh cng tc nh hng n ct p v vi

mt ng c tnh li nht nh, n s lm thay i lu lng ca my. Do vy c th iu

chnh qut bng cch tc dng ln dng kh vo qut bng cc thit b c bit. C hai loi

thit b nh hng: loi hng trc v loi hng knh.

Thit b nh hng hng trc (dng

trong trng hp dng chy li vo bnh

cng tc l hng trc)

Cnh dn vi cc trc hng knh ng thi

quay nh mt thit b c bit. Mt trong cc

v tr c trng ca n l ng vi v tr cnh

dn mt phng chnh phng (m hon

ton) v lc y dng li vo bnh cng tc

s i theo hng trc, lu lng lc ny l

ln nht Qmax. Mt v tr c trng khc ng

vi trng hp cc cnh dn ny ng hon

ton, ngha l Q = 0. Cc v tr trung gian cho

ta cc gi tr iu chnh. Thit b ny tin li

khi dng cht kh i vo qut theo hng dc

trc.

Thit b nh hng hng knh (dng

trong trng hp dng chy li vo bnh

cng tc l hng knh)

y mng li cnh hnh tr trn, cc cnh

dn c dng elip tr c trc song song vi

trc

roto ca my, mng li ny s gy ra s i

hng ca dng khi mt phng chnh

phng. S lch dng c iu chnh bng

gc lch gia mt phng trung bnh ca cc

cnh vi mt phng chnh phng (l mt

phng i qua trc quay ca cnh). T hnh

v ta thy, thit b iu chnh hng knh

i hi dng vo phi c hng knh. Thit

b iu chnh t ngay ca vo bnh cng

tc cng gn cng tt, c nh vy hiu qu

iu chnh mi cao.

HUMG 2015


th thay i cng sut khi iu chnh bng thit

b nh hng

Trn hnh l ng c tnh ca ct p,

cng sut khi n = const, ng vi 3 v tr

khc nhau ca thit b nh hng

ca vo l H1, H2, H3v N1, N2, N3. Khi

qut lm vic vi ng c tnh li

cho trc, ta c 3 im tng ng A1,

A2, A3, cho ta nhng gi tr tng ng

ca lu lng Q1, Q2, Q3v cng sut l

N1, N2, N3. Ta xc nh c cc im

I, II, III. Ni chng ta c ng

thay i cng sut khi iu chnh bng

thit b nh hng hng knh.

Phng php ny c dng rng ri trong tt c cc loi qut nht l cc loi qut ln.

Nu cc thit b nh hng c thit k v gia cng tt, gc ngot ca cc cnh qut hng

b th tn tht do iu chnh s t v phng php iu chnh ny c u vit hn so vi iu

chnh bng tit lu.

2.2.3 La chn qut theo iu kin cho trc

la chn qut, ngi ta cho trc nng sut Q v p sut p. Cc i lng ny c cho

trong iu kin lm vic ca qut. Cc tham s c tnh c cho theo iu kin tiu chun,

ngha l t = 200C, p sut kh quyn po= 760mmHg v m tng i 50%. Vic la chn

qut theo cm nang c tin hnh vi d tr 5% v lu lng v 10% v p sut, ngha

l:

QK= 1,05.Q v pK = 1,1. p.

y QK, pK, thng s trong iu kin chun cho.

T cc gi tr ca QK, pK ta la chn loi qut cn thit. Phng php ny cho php ta xc

nh loi qut, kch thc qut cng nh s vng quay. t hng mua cc loi qut, th

ngoi loi qut, kch thc v s vng quay, cn phi bit cc tham s ph khc nh: cc

thng s c dng lm c s chn qut, chiu quay ca roto, v tr ca ng ht v ng

y, loi ng c c dng ko, Vic xc nh v N trong iu kin lm vic v tnh

ton cc kch thc hnh hc ca n c th tin hnh theo cc c tnh khng th nguyn v

s kh ng ca loi qut chn.

2.2.4 Phn loi qut v mt s chi tit chnh ca qut ly tm

a. Phn loi qut: Thng ngi ta phn loi qut theo cc tiu chun sau:

1.Theo p sut do qut to nn:

Qut p sut thp: C p sut ton phn ( hiu s cc p sut ton phn tit din ra

v tit din vo) di 100 kG/m2

HUMG 2015


Qut p sut trung bnh: c p sut ton phn t 100 200 kG/m2

Qut c p sut cao: p sut ton phn t 300 1200 kG/m2

2. Theo hng quay ca bnh cng tc:

Qut c hng quay bn phi: khi bnh cng tc quay theo chiu kim ng h

Qut c hng quay bn tri: khi bnh cng tc quay ngc chiu kim ng h

3. Theo s pha ng ht:

Qut mt pha ht

Qut hai pha ht

4. Theo s vng quay c trng nS:

Qut c s vng quay c trng b: nS< 25 vg/ph

Qut c s vng quay c trng trung bnh: nS= 25 50 vg/ph

Qut c s vng quay c trng ln: nS > 50 80 vg/ph

Ngoi ra, ngi ta cn phn loi qut theo s kt cu, theo tnh nng lm vic,

b. Mt s chi tit ca qut ly tm

Cch a dng kh vo bnh cng tc c nh hng rt ln n hiu qu, n qu trnh lm

vic ca qut ly tm. Nu phn vo ca qut tt, c kt cu ng s lm cho dng kh phn b

u n ti thit

din vo ca bnh cng tc v m bo cho n c ph ti u n. Do vy, mt trong nhng

b phn quan trng ca qut l:

1. ng vo

Cc loi ng vo

li vo ca qut c t ng vo. Hnh dng khc nhau ca n c th hin hnh. Hnh

dng hnh hc ca ng vo phi m bo tn tht nng lng ch vo l b nht. iu

ny c m bo khi ng vo c hnh dng u n (khng gp khc). Cn khi t qut vo

h thng cc ng ng qut khng kh i khi i hi phi t li vo cc hp v ng

c cu to c bit. Nhng chi tit ny ph hy tnh i xng ca dng ch vo v s u

n ca ph ti ca bnh cng tc dn n gim hiu sut. Cc hp vo c s dng trong

HUMG 2015


trng hp ht t hai pha. Do c hp vo, cc pali ( bc ) ca qut trc c t ngoi

ng khi ( cc qut khi) . iu ny rt quan trng khi vn chuyn cc kh nng v vic

kim tra lp rp cc pali cng d dng hn. i khi cc hp vo cng c lp qut c

hp ht mt pha, khi roto s c lp trn 2 gi, chiu rng bnh cng tc tng v tc

vng quay cng tng.

Trong trng hp do lp rp phi un cong cc ng ng trc qut, th cng nn t hp

vo. Nu ca vo c thit b iu chnh th tin nht nn t n trong hp vo.

Hp vo phi c din tch ln. i lng tng i

iH =

= 1,75 2,25

Trong : H- tit din ca hp; O- din tch tit din vo ca bnh cng tc

Gc t Hca hp vo tt nht khi H = 900

2.a ph

Hnh dng ca a ph c nh hng rt ln n tn tht nng lng ca dng trong bnh

cng tc. Tn tht s t nht khi hnh dng a ph u n v cnh vo nghing.

3. Chiu rng bnh cng tc

Chiu rng bnh cng tc tng th chiu di cc lu tuyn tng, dn n gim cong ca

gc ngot, tn tht nng lng s gim.

4.V qut

V qut thng c dng xon c v trong mt s t trng hp c dng ng tng p vng.

Trong v xon c, khng phi lc no tc ra ca kh sau qut cng gim cho n khi

bng tc ca dng trong ng ng. Trong trng hp nh vy, ch ra ca qut ngi ta

t thm ng tng p hnh cn.

HUMG 2015


ng ra xon c thng c dng li. Kinh nghim cho thy, li s lm tng ting n khi

qut lm vic v c th lm gim hiu sut ca n. ng tng p hnh cn ch ra sau ng

xon c c dng i xng vi gc loe n 250v pha bnh cng tc.

2.2.5 nh hng tp cht kh n s lm vic ca qut

Trong mt s trng hp, cht kh do qut vn chuyn c cha cc ht cng nh. V d nh

khi vn chuyn kh nn, ht khng kh c bi, cc thit b qut khi.

Khi lm vic vi loi kh c tp cht ny, bnh cng tc cn c sc chng tt i vi s bo

mn ca cc ht cng c trong dng chy. V vy, bnh cng tc v may- ca n phi c

ch to t nhng vt liu cng, chng mi mn tt. S cnh ca bnh cng tc cn chn t,

khong t 6 8 cnh tho ri v sa cha nhanh.

Ta cn xt nh hng ca cc ht cng cha trong cht kh n cc thng s lm vic ca

qut. Nng cc ht cng trong cht kh c c trng bng h s nng khi lng :

=

Trong :

CM - khi lng ht cng c trong cht kh dch chuyn trong mt giy, kg/s

MK - khi lng cht kh sch ca tp cht dch chuyn c trong mt giy, kg/s

* Thc nghim cho thy rng khi tp cht c nh v kch thc ca ht bi nh th ct p

v lu lng qut cng bng nh khi lm vic vi kh sch. Ch c khi lng ring , p

sut p v cng sut N l thay i.

Nu qut vn chuyn tp cht c nhng ht cng c kch thc ln, th thnh phn nm

ngang ca vn tc trong dng chy khng gi ht cng trng thi l lng na. Xy ra

s va p cc ht cng vo b mt, sinh ra thm tn tht nng lng ph na thng lc ma

st ca cc ht cng vi b mt. Lc , tn tht nng lng trong bnh cng tc ti ng vo

v ra ca qut s tng ln, p lc do qut to nn gim v cng sut s tng.

Ta thy, qut dng vn chuyn hn hp lm vic rt nng n (v d: qut khi trong cc

nh my nhit in). Bt than v tro s lm cnh qut chng b h hng. Qut h hng cng

nhanh nu cnh cng mng, s vng quay cng ln v kch thc cc ht cng cng ln. Thi

gian lm vic ca qut khi cn ph thuc vo hnh dng cnh. V d: qut c cnh dn

nghing v pha sau s t b h hng hn so vi qut c cnh dn nghing v pha trc trong

cng mt iu kin lm vic.

HUMG 2015


Cc bin php chnh gim s h hng ca qut khi:

Gim s vng quay.

Tng chiu dy ca cnh n 8 mm.

Hn thm trn b mt cnh mt ming kim loi cng chng mn.

Dng cc tm mng bo v.

Bo v tng xon c bng nhng tm kim loi c bit dy 10 ?12 mm.

Ci tin cc thit b lc tro.

Chn hnh dng thch hp cho cnh qut.

2.3 QUT TRC

2.3.1 Nhng ch v qut trc

Trong cc loi my trc, c th l qut trc, s truyn nng lng t qut cho dng chy xy

ra nh s gip ca bnh cng tc c nhng cnh dn cng-x n c gn ch t vi ng lt.

V bnh cng tc ca my khi quay c gi theo hng trc, cn cnh dn ca n c gn

chc di mt gc nghing i vi mt phng quay, nn bnh cng tc vn chuyn cht lng

( hay cht kh) dc theo tr c. V vy nn dng chy c b xon mt phn.

kho st qu trnh lm vic c a my trc, ngi ta s dng thuyt mng prfin cnh

(mng bin dng cnh).

S nguyn l kt cu qut trc

Ct vng bnh cng tc theo mt phng tr bng bn knh r v tri mt phng ny ra

cng cc thit din cnh dn, ta thu c mng prfin phng ca qut trc.

Mng prfin cnh dn

HUMG 2015


Cc gi tr c bn, c trng hnh hc ca mng l:

t - bc ca cnh dn, o theo hng chuyn ng ca mng;

b - di dy cung ca thit din cnh dn;

B - chiu rng ca mng, o song song vi trc quay;

1,2 - gc ca vo v ra ca cnh dn, gc gia dy cung cnh dn v trc mng.

C mt s khi nim c bn sau:

a - Mt ca mng: k hiu l t s gia dy cung v bc cnh dn.

b - Bc tng i ca cnh dn: k hiu t l i lng nghch o ca mt .

t =

=

Khi xy dng s vn tc ca vo v ra, ta a vo c c thng s ng hc c bn ca

dng chy qua mng

S vn tc ca mng

u1, w1, c1v u2, w2, c2 tng ng vi vn tc dch chuyn, vn tc tng i, vn tc tuyt

i ca vo v ca ra.

1, 2 - gc vo v gc ra.

i1 - gc tin ca cnh dn ca ca vo ( gc gia tip tuyn ca ng trung bnh ca mng

vi vn tc tng i ca vo).

i2 - gc tin ca cnh dn ca ca ra

i - gc tin ca cnh dn ca mng (gc gia dy cung ca mng v vec-t vn tc

tng i trung bnh w).

T s vn tc ny, ta suy ra: mng prfin lm thay i gi tr v hng ca vn tc tng

i v tuyt i. iu khc bit c trng ca qut trc l s xon ca dng chy (c2u > c1u )

v s hin din ca s lu li ca dng chy li ra ( 0).

HUMG 2015


2.3.2 Qut trc nhiu cp

S qut trc nhiu cp

Phn tch cng thc p1 = . (cot g1 cot g2), c th thy rng p sut c to nn bi

1 bnh cng tc qut trc b gii hn bi cc yu t vn tc v hnh hc. Trong cc my trc

hin i ca cc thit b vn ti, ngi ta s dng vn tc u c c cnh dn ca bnh cng

tc rt cao, n 400m/s. Nhng d c nh vy, trong nhiu trng hp vn khng m bo p

sut cn thit. Khi ngi ta s dng my nhiu cp. Qut trc nhiu cp c mt s vng

ng trc c t tr n mt trc chung. C gia hai bnh cng tc c t mt thit b nh

hng.

Cng dng ca n:

Vn li dng ra t bnh cng tc.

Cho dng mt hng cn thit trao i nng l ng tch cc cp sau.

Bin i mt phn ct p ng thnh th nng.

Thit b nh hng c lm t nhng tm cong u c chiu dy bin i, c sc cn mt

trc nh. S cp p sut trong my trc c khi ln n 20 cp.

2.3.3 iu kin lm vic ca qut trc

Cc thnh phn ca cnh dn ca qut trc, nhng khong cch khc nhau cch tm, quay

vi nhng vn tc khc nhau. V vy, cnh dn vi chiu rng khng i v cc gc ra vo

khng i to nn ct p thay i theo chi u di ca cnh dn. iu ny dn n s di

chuyn hng knh ca cc phn t cht lng trong dng chy ca bnh cng tc v s tho

dn lm gim hiu sut ca qut.

Hin tng di chuyn hng knh ny c bit r trong cc cp ca qut trc c di cnh

dn ln. V vy cc cp ca qut trc c di cnh dn ln thng c thit k t iu

kin khng c s di chuyn hng knh ca dng cht lng.

Ta bit rng: trong cc loi my trc, nu b qua lc nht ca dng, th iu kin cn bng

hng knh c th hin bng ng thc:

r.cu= const (*)

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Cng thc ny c gi tr thc t rt ln. iu kin khng c s chuyn ng hng knh

ch thc hin c khi khng c s thay i ca qu trnh tun hon theo chiu di cnh

dn. Trong trng h p ny, mi mt phn t ca dng chy chuy n ng theo mt tr trn

ca bn knh tng ng.

Phng trnh (*) l lun quan trng nht trong thuyt Giuk pxki. Thc hin c biu

thc ny trong qut trc cho php tng rt nhiu hiu sut ca my.

nh hng ca iu kin (*) ln hnh dng kt cu ca cnh th hin ch cnh dn c dng

cong xon c vi nhng gc 1, 2 thay i theo chiu di cnh dn. Nhng cnh dn loi ny

c s dng rt rng ri, c bit nhng my ng lt c ng knh tng i nh. Trong

nhng my ng lt c ng knh tng i ln, cnh dn c lm khng cong, nhng dy

cung gim t trong ra ngoi.

2.3.4 iu chnh lu lng

iu chnh lu lng ca qut trc c th c tin hnh bng cch thay i s

vng quay, thay i gc quay ca cnh dn lm vic bng thit b hng dng ca vo v

bng tit lu. Cch th nht c hiu qu hn c.

iu chnh bng tit lu c bit khng kinh t, v lu lng b gim trong khi cng

sut khng i hoc tng. V vy tiu hao nng lng trn mt n v th tch cht lng khi

iu

chnh bng phng php ny tng. Khi iu chnh qut bng gc quay cnh dn ca bnh

cng tc hay bng thit b hng dng ca vo tit kim rt ln nng lng trong qu trnh

truyn ng. Khi iu chnh bng gc quay cnh dn hoc thit b hng dng rt tin li

trong vic s dng ng c tnh iu chnh tiu chun.

III. MY NN

3.1.1 Khi nim chung

My nn l my nn kh vi c s tng p > 1,15 v c lm lnh nhn to ni xy ra

qu trnh nn kh. Cng dng ca my nn l nn kh v di chuyn kh nn n ni tiu th

theo h thng ng dn.

My nn dng tho kh t bnh chn khng v nn chng n p sut kh quyn hoc p

sut ln hn, c gi l bm chn khng.

Cc thng s c bn c trng cho s lm vic ca my nn l: lu lng th tch Q (thng

c tnh trong iu kin ht), p sut u p1v p sut cui p2 hoc h s tng p = p2/p1,

s vng quay n v cng sut N trn trc ca my nn.

3.1.2 Phn loi my nn

1. Theo nguyn l lm vic c th chia my nn ra lm 3 loi:

My nn th tch.

My nn cnh dn.

HUMG 2015


My nn phun tia.

2. Theo kt cu:

- My nn th tch c 2 loi:

My nn piston.

My nn roto.

- My nn cnh dn c 2 loi:

My nn ly tm.

My nn trc.

Ngoi ra cn c th chia my nn ra thnh tng nhm theo dng cht kh lm vic, theo

dng truyn dn,

3.1.3 S kt cu mt s my nn in hnh

My nn piston( mt piston vi mt cp nn)

Vi chuyn ng tnh tin ln xung ca

piston, cc qu trnh sau c thc hin: Dn

n, Ht, Nn, y. Phng php tc dng

ca my nn piston da vo s thi kh

bng piston, cho php xy dng c nhng

kt cu vi ng knh v hnh trnh piston

nh, c p sut ln khi lu lng b.

My nn roto dng tm phng

My nn roto dng tm phng

1. V 2. Roto

3. Cc tm phng 4. ng ht

5. ng y

Khi roto 2 quay, trong cc rnh dc ca

roto, cc tm phng 3 c th t do di

chuyn, kh c in y trong khong

khng gian gia cc cnh c mang t ng

ht 4 n ng y 5 v c thi ra h

thng ng dn.

Trc roto ca my nn c th ni vi trc ca ng c khi ng mt cch trc tip khng

cn b truyn ng. iu ny lm cho my gin tin, d dng v lm gim khi lng.

My nn trc

HUMG 2015


My nn trc

1. Cnh dn cng tc (cnh dn ng)

2. Roto 3. Cnh dn hng dng

Kt cu gm roto c gn cnh dn lm

vic, v c gn cnh dn hng dng c

nh. Kh c ht vo ng ht, chuyn

ng dc trc v ng thi b nn trong

cc cp nn ca cnh dn. Qua ng y

kh c y vo h thng ng dn n

ni tiu th. khi ng my nn trc

dng ng c in, tuabin hi nc hoc

tuabin kh.

3.1.4 Lm lnh trung gian v nn nhiu cp

p sut m my nn to c khi lm vic trong s cng ngh sn xut t ti nhng gi

tr rt ln. Mt khc, to c p sut cao trong mt cp ca my nn gp kh khn.

Nguyn nhn:

Trong my nn th tch: l s tng qu mc nhit cui qu trnh nn, gy nn

s khng th thit k mt my nn c th ly nhit lng t kh nn mnh.

Trong my nn cnh dn: l khng cho php vn tc cnh dn qu ln, v cnh dn

c lm t nhng vt liu c bn xc nh.

V vy: tng p sut trong qa trnh nn ngi ta thng dng:

Lm lnh kh trong qu trnh nn

Tin hnh nn kh nhng cp ni tip, ng thi thc hin gim nhit kh

thit b lnh c t gia cc cp.

S chung ca my nn c cc cp nn

S nn nhiu cp

1,2 Thit b lnh

3,4,5 Cp my nn

S dng my nn c cp vi s lm lnh kh

nhng thit b lnh (TBL) gia cc cp a

li tit kim ln nng lng phi tiu hao

dn ng my nn.

iu ny thy r trn th T-S v p-v ca my nn 2 cp

HUMG 2015


Nu qu trnh nn tin hnh trong 1 cp, th ng nn c biu th bng ng a bin c

n > k : 1-2. Khi nn cng trong khong p sut y, 2 cp c biu th bng ng gp

khc 1-2-1-2, c to bi 2 ng a bin 1-2 v 1-2 v mt ng ng p 2-1,

l qu trnh lm lnh thit b lnh gia cp vi p sut cp pc = const. Trong 2 th, nng

lng tit kim c t qu trnh nn 2 cp c lm lnh gia cp c biu din bng din

tch c gch ngang 1-2-2-2.

Trong my nn hin i, ngi ta s dng:

1. Lm lnh my nn bng cch a nc vo khoang c lm c bit trong v c

gi l lm lnh trong. Phng php ny lm tt mt cch ng k iu kin tra du m

ca my nn piston. Cn bng phng php ny mun tit kim nng lng v a qu

trnh nn v ng nhit khng thc hin c. Nguyn nhn l iu kin trao i nhit

gia cc dng kh v nc lnh gp kh khn.

2. Lm lnh trong thit b lnh c t gia hai cp ring r gi l lm lnh ngoi.

Vi phng php ny s dng thit b lnh dng ng c b mt tip xc ln c th thu

c tit kim nng lng tiu hao 1 phn. Trong cc my nn ly tm, cc thit b lnh

thng c phn b gia cc nhm cp lm n gin kt cu ca thit b.

3. Lm lnh lin hp l kt hp c lm lnh trong v lm lnh ngoi. Phng php ny c

tnh hiu qu ln nht v c s dng rt rng ri mc d kt cu phc tp v tng gi

thit b.

4. Lm lnh bng s phun nc lnh vo dng kh trc cp th nhtca my nn. Vi

phng php ny nhit lng kh c tiu hao tng phn lm bay hi nc lm lnh

v nhit cui qu trnh nn b gim kh nhiu. Nhc im ca phng php ny l

lm m kh do trong mt s trng hp khng th dng c.

3.2 My nn cnh dn ly tm

3.2.1 Nguyn l lm vic

S nguyn l ca cp my nn ly tm

1.a chnh

2.Cnh dn

3.a ph

4.Trc

5.ng tng p

6.Rnh cnh hng quay

7.Rnh cnh hng ngc

8.on vo

HUMG 2015


Trn s l hnh v n gin ca bnh cng tc ca my nn ly tm. Kh i vo bnh cng

tc theo hng trc (nh hnh v) sau quay 1 gc 900 v i vo rnh cnh. Rnh cnh c

to nn bi a chnh 1, cc cnh dn 2 v a ph 3.

Cnh dn trong khi quay truyn cho kh mt chuyn ng quay. y lc ly tm xut

hin v y cc phn t kh chuyn ng t trong ra ngoi v nh vy kh b nn li. Chuyn

ng tng i ca dng kh trong my nn ly tm theo ng xon c. Sau khi ra khi

bnh cng tc, kh b nn i vo ng tng p 5 nm bao quanh bnh cng tc. y ng

nng bin thnh th nng, tc l p lc tnh ca khng kh nn tng. ng tng p c th c

cnh hng hoc khng c cnh hng. Trong ng ny kh nn cng chuyn ng theo

ng xon c. Nh c cc cnh qut h ng quay 6 v cnh qut hng ngc 7, kh nn

c a vo bnh cng tc qua tng sau. cc cnh dn ny dng cng b xon theo

chuyn ng xon c. on vo 8 m bo cho kh nn vo bnh cng tc tng sau c

u. Tng (hay cp) my nn bao gm: bnh cng tc, ng tng p, cc cnh nh hng xui

v ngc.

3.2.2 Vn hnh v bo dng my nn kh ly tm

1. sc (surging)

Thng thng p sut ngay ti ming y phi ln hn p sut ca ni cn chuyn kh ti

(gi l p sut ca h thng). Do mt nguyn nhn no m p sut ca h thng cao hn

p sut ti ming y ca my nn, r rng kh khng th chuyn ti h thng c m

ngc li kh t h thng s chuyn ngc li ngun ban u qua my nn cho n khi p

sut ca h thng nh hn p sut ti ming y ca my nn. Trong trng hp ny kh

chuyn ng qua li my nn. Hin tng nh vy gi l hin tng sc.

Sc c th gy h hng my nn. Sc thng sy ra khi my nn hot ng di nng sut

thit k ti thiu. ngn nga hin tng ny xy ra, ngi ta c th thit k thm van x

kh hoc ng bypass nh trnh by trong mc di y.

2. X kh v by-pass

My nn kh thng c gn thm mt van x kh pha sau hoc lp thm mt ng by-pass ni

lin rc my vi sau my, van x kh v ng by-pass c minh ho nh hnh v sau:

HUMG 2015


Trn hnh v trn, van x thc cht l van an ton p sut. Khi p sut sau my nn cao hn

setpoint (p sut mong mun c t cho van an ton) th van ny s t ng m x kh

ra ngoi. Trong cng nghip, kh x ny thng c x vo mt h thng ng ri dn ti

uc t hoc dn ti h thng thu hi.

Trn hnh v trn, ng by-pass thc cht l mt on ng ni trc v sau my nn. Mt van

an ton p sut hoc van iu khin c lp trn ng ng ny. Khi p sut trong my nn

tng cao c nguy c xy ra hin tng sc th van s m hi lu mt phn kh t pha sau

my nn quay tr li b sung vo ngun kh ang nn. ng hi lu c t sau thit b lm

ngui kh v kh sau khi nn s nng nu hi lu s lm nng thm.

3. Mc ch iu khin

C 3 mc ch chnh:

- Vn chuyn mt lng kh khng i

- Vn chuyn lng kh sinh ra

- Vn chuyn lng kh cn

thc hin cc mc ch ny ngi ta c th iu chnh van cung cp kh ti my nn hoc

thay i tc ng c chnh. Tu theo mc ch iu khin m tin hiu iu khin s khc

nhau. Trong trng hp vn chuyn kh vi lu lng khng i th chng ta c th ly tn

hiu l lu lng dng kh iu khin. Trong trng hp vn chuyn kh sinh ra th p sut

khi ni sn sut l tn hiu. Cn trng hp vn chuyn lng kh cn th tn hiu iu khin

l p sut kh ni tiu th nh minh ho hnh sau:

4. Ni song song v ni ni tip

HUMG 2015


Cng nh my bm, my nn cng c th ni song song hoc ni ni tip. Ni song song

nhm tng lu lng dng kh cn nn cn ni ni tip nhm tng p sut kh cn nn. Tt c

cc my nn mc song song u phi c lp t van mt chiu trnh trng hp dng kh

chy ngc tr li.

Van mt chiu ch ngn dng kh chy ngc tr li qua my nn nhng khng ngn c

trit hin tng sc. khc phc hin tng ny th vn phi cn s h tr ca van x

kh hoc ng bypass nh ni trn. Lu ng by-pass phi t trc van mt chiu.

5. Trch nhim ca ngi vn hnh

Pht hin nhng iu bt thng trc khi xy ra s c. Mt s s c c chung bo ng

phng iu khin nhng cng c s c phi pht hin trc tip tai hin trng.

Trong khi i kim tra, ngi vn hnh cn phi kim tra cc thng s vn hnh quan trng

nh lu lng dng du m kn (nu cao cho thy cc vng m b mn nhiu), mc du

trong bn cha (nu cn th phi b sung thm),

Lu trong mt s my nn, h thng du m kn v du bi trn c th chung nhau bn

cha v c th c bm, nhng thng thng chng l hai h thng ring bit. V vy khi bm

du m kn b hng th bm d bi trn khng cung cp du bi trn n cc vng m kn

v ngc li.

kim tra cc thit b lc du, chnh lch p sut trc va sau thit b lc ln hn mc thit k

cho thy thit b lc b bn cn phi chuyn sang nhnh d phng v lm sch thit b lc

b bn.

i vi thit b lm mt cng vy, khi nhn thy hiu sut lm ngui gim th phi chuyn

sang nhnh d phng v lm sch thit b km hiu qu.

Kim tra v pht hin ting ku l trong my.

Ghi chp y cc thng s vn hnh quan trng trn ng h o sau nhng khong th

gian nht nh (2 gi mt ln), cng nh ghi li y cc s c, nhng c im lu trong

khi ang vn hnh. Nu c s thay i t ngt trong cc thng s ghi li ny chng t ang

c s c lin quan.

6. Chun b khi ng

C rt nhiu bc cn phi kim tra trc khi khi ng. Sau y l mt s im c lu :

- Kim tra lm sch cht lng trong h thng.

- Kim tra mc du m kn v du bi trn.

- Khi ng h thng du lm kn v du bi trn trc khi khi ng my nn mt khong

thi gian nhit du t n gii hn cho php ca thit b

- Kim tra chnh lch p sut qua thit b lc.

- Kim tra s hot ng ca thit b lm ngui du (n ch hot ng khi nhit ca du

n nhit hot ng).

HUMG 2015


- m bo cc thit b iu khin v van an ton trng thi hot ng tt (lu cc tn hiu

bo v ch hot ng khi my nn hot ng n nh).

7. Khi ng

Khi khi ng my nn kh ngoi vic phi tun th ng theo qui trnh vn hnh m nh sn

xut a ra ta cn phi lu thm mt s im sau:

- Ch khi ng khi h thng chung sn sng.

- Phi c s kt hp gia cc b phn lin quan.

- i vi motor in th n cn t n tc vn hnh cng nhanh cng tt trnh lm tn

hi motor nn phi tm mi cch gim ti ti a.

- i vi turbine, do momen khi ng ln, my nn c th khi ng ch ton ti.

8. Ngng hot ng

Yu t chnh nh hng n quy trnh ngng hot ng l my nn kh vo mt h thng c

p sut c nh hay khng c nh.

Nu h thng c p sut khng c nh, khi ng c chnh gim tc , dng kh cng gim,

tc cng gim theo cho n khi ngng hn. Trng hp ny s khng b sc. Nu h thng

p sut c nh, khi p sut y ca my nn gim xung nh hn p sut ca h thng, van

mt chiu s ng v ngn khng cho kh ngc tr li. Nng sut my nn kh s gim ngay

xung 0. Trong khi tc my nn ang gim dn, phn kh phn kh kt li pha sau my

nn s gy ra sc. trnh hin tng ny cn ngng hot ng vi van x hoc van by-pass

m.

Trong hu ht my nn, van t ng by-pass c iu khin bng lu lng dng kh sau

my nn ch khng phi bng p sut trong my nn. Nu lu lng sau my nn gim

xung di setpoint th van s m. Trong trng hp dng p sut sau my nn iu khin

van t ng by-pass, n s khng t ng ngn chn hin tng sc. (Trong trng hp sc

p sut sau my nn lin tc tng gim).

Sau khi ngng hot ng, h thng lm mt, du bi trn, du m kn vn tip tc hot ng

cho n khi my ngui.

Lm sch my nn nu chng dng nn kh c.

9. bo dng k thut my kh ly tm

- Thng xuyn v sinh bn ngoi my nn v ng c dn ng.

- Kim tra v khc phc s r r cc ng ng dn kh, nc lm mt, du bi trn v

nhin liu.

- Khim tra v sit li cc mi ghp bng bulng, ai c ng lc sit quy nh.

- Kim tra thay th cc bnh cng tc ca my nn kh.

- Thay th cc m lm kn nu chng khng m bo kn.

- nh k thay nht v lm sch h thng bi trn ca my nn v ng c dn ng.

HUMG 2015


- nh k sc ra h thng cung cp nhin liu ca ng c dn ng (cc b lc ca thng

cha nhin liu).

- nh k r li xupp, kim tra iu chnh khe h nhit ca xupp cho ng c dn ng.

- Tra m vo cc bi theo s ch dn ca nh ch to.

10. Phn on v x l s c

Hin tng Nguyn nhn Cch khc phc

1. p sut du bi trn

trc b lc gim thp hn

tr s quy nh.

- Thiu du bi trn.

- H mch du bi trn.

- iu chnh p sut bm

du b trn kng ng tr s

.

- thm du bi trn

ng mc quy nh.

- Kim tra sit li cc mi

ghp.

- iu chnh li p lc ca

bm nht.

2. p sut du bi trn

trc b lc tng qu gi tr

s quy nh.

- B lc b tc do bn.

- iu chnh p sut bm

du bi trn khng ng tr

s.

- Sc ra b lc.

- iu chnh li p lc ca

bm nht.

3. Nhit du bi trn

vt qu quy nh.

- Thiu nc lm mt.

- h thng lm mt nc b

h hng.

- Cp thm nc lm mt.

- kim tra v khc phc.

4. Nhit trc ln cao

qu 70C.

Du bi trn khng Kim tra h thng bi trn

v cp thm du bi trn.

5. Nhit kh nn qu cao. - Thiu nc lm mt.

- Bm nc hoc qut lm

mt c h hng.

- Cn bn trong bnh lm

mt nhiu

- Cp thm nc lm mt.

- kim tra khc phc cc h

hng.

- Sc ra sch bnh lm

mt.

6. Lng cung cp kh nn

gim cng vi gim p sut.

- H hng cc m lm kn.

- H b mt lp ghp ca v

my.

- Km tra v thay th m

mi.

- Kim tra v xit li ng

lc. Thay m b mt lp

ghp.

7. Kh nn ln nhiu nc. - Nc lm mt lt vo my

nn kh.

- Thit b phn ly nc lm

vic khng tt.

- Nc lm mt lt vo kh

- Kim tra tm nguyn nhn

v khc phc.

- Kim tra khc phc.

- Kim tra khc phc.

HUMG 2015


nn ti cc bnh lm mt

trung gian hoc lm mt sau

cng.

8. My nn kh b rung

ng mnh.

- Khng m bo s ng

tm gia trc my nn v

trc ng c dn ng.

- trc b mn vt qu

gii hn cho php.

- Nn t my khng phng.

- Kim tra v iu chnh li

ng tm.

- Thay trc mi.

- K kch li.

9. My nn kh cp kh nn

c p sut cao hn mc qui

nh.

- Van an ton b hng hay

do iu chnh khng ng.

- Kim tra khc phc v

iu chnh li.

3.3 My nn trc

3.3.1 Cu to chung ca my nn trc, cu to cp

S cu to chung ca my nn trc

1. Cnh dn lm vic

2. Roto trng

3. Cnh dn nh hng

Khc vi my nn ly tm, my nn trc kh nn chuyn ng dc theo trc.

Roto 1 c dng trng. Trn roto c gn cc cnh dn lm vic 3. Cc cnh dn nh

hng c nh 4 c gn tr n thn my 2. Nhng cnh dn ny cng c gn trc cp

th nht v sau cp sau cng.

Kh c cc thng s ban u p1, T1, C1 i vo ng vo ca my nn, sau khi i qua tt c cc

cp, chng s i qua ng tng p, sau i qua ng y n ni tiu th. ng vo c cc

cnh hng dng lm cho dng hi ngot v pha quay ca roto hoc v pha ngc li ty

theo tnh cht ca tng tng. Trong mt s my nn, b vo khng c.

Trong cc rnh tng p ca cc cnh dn ng, nng lng ca dng s tng, tc l p sut

v vn tc tng. Khi dng kh chuyn ng qua cc cnh dn ng xut hin lc P = Px+ Py.

Lc ny c hng ngc vi hng quay ca bnh cng tc v to ra cng nn. Cn trong

HUMG 2015


cc rnh ca cnh nh h ng ch c s bin ng nng thnh th nng v gip cho

dng kh c mt hng nht nh trc khi vo dy cnh ng sau.

Cu to cp my nn trc

My nn trc c to bi mt s c p p sut. Mi cp gm mt vnh quay cc cnh dn

lm vic v mt vnh c nh cc cnh dn hng dng to thnh mng cnh dn. Cc cnh

dn lm vic c gn cht vo cc a hay gn cht vo roto trng, cn cc cnh dn hng

dng c gn cht vo v ca my nn.

Cp u ca my nn c th c lm c cnh dn hng hoc khng c chng. Cn cp

cui cng lun lun c cnh dn hng dng ra, mc ch ca n l vn dng v lm gim

mt mt nng lng ca ra.

3.4 My nn piston

3.4.1 Nguyn l lm vic

V cu to, my nn piston hon ton ging

bm piston, tc l gm xilanh 1, piston 2

chuyn ng tnh tin, trn piston c lp mt

vi vng m (xecmng) 3. Mi u xilanh c 2

hp van. Khi piston chuyn ng sang tri th

khong xilanh bn phi c chn khng, van

4 v van 7 m, van 6 v van 9 ng, kh qua

ng ht 5 vo bn phi, cng lc th

khong khng gian bn tri c y ra ng

y 8. Khi piston chuyn ng ngc li t tri

sang phi th van 7 v 4 ng li, cn van 6 v

van 9 m ra, phn xilanh bn tri ht v phn

xilanh bn phi y.

S nguyn l my nn piston

1 xilanh 2 piston 3 vng m

4, 9 van ht 5 - ng ht

6, 7 van y 8 ng y

HUMG 2015


Nh vy, sau mt vng quay ca trc, piston chuyn dch sang tri mt ln v sang phi mt

ln, kh c ht vo v y ra 2 ln. V tr bin hai u xilanh gi l v tr cht v khong

khng gian gia piston v tr cht v u xilanh gi l khong hi. Tr s khong hi ph

thuc vo cu to ca van v c nh hng xu trong qu trnh lm vic ca my nn.

So snh vi cu to ca bm piston th trong my nn piston th trong my nn piston cc hp

van cn phi kn, kht v do trong qu trnh

nn kh ta nhit nng ln, nn phi t thm b phn lm ngui, nht l khi nn nhiu cp.

3.4.2 Qu trnh nn l thuyt v thc t

Biu din qu trnh lm vic ca my nn tc dng n trn th p V ta thy, khi piston

v tr bn tri (a) chuyn ng v bn phi th kh c ht vo xilanh theo ng AB vi p

sut p1. Khi piston n v tr cht (b) th ht c th tch V1 vi p sut p1 v nhit t1.

Khi piston chuyn ng v bn tri th van ht ng li, nn kh c nn v p sut tng dn

n p2, theo ng BC l qu trnh a bin (nu qu trnh ng nhit theo BC1, qu trnh on

nhit theo BC2). Khi piston n v tr (c), tc p sut kh trong xilanh t p2 bng p sut ng

y th van y m ra, nn kh c y vo ng y vi p sut khng i p2 theo ng

CD. Qu trnh nn ny l qu trnh l thuyt, khng c khong hi v cc nh hng khc.

Trong thc t, qu trnh nn kh xy ra phc tp

hn do nhng nguyn nhn sau :

- Tn ti khong hi: khi piston n v tr

cht, hai u xilanh vn cn tn ti mt lng

kh c th tch bng th tch khong hi v p

sut y p2. Do khi tin hnh qua trnh ht

lng kh ny c gin ra cho n khi t p

sut p1 ng DA, th ban ht mi m ra c

v qu trnh ht kh mi bt u. Do lng

kh ht c thc t nh hn th tch l thuyt

ca xilanh.

- nh hng ca lc cc van ht v y: Do

lc ca cc van m thc t cc van ht v y

m ra khi p sut thp hn p1 v cao hn p2 mt

cht, im A v C.

- nh hng ca sc cn thy lc trn ng ng v cc van, nhit , m ca kh tng

khi nn, van, xilanh, piston khng tht kn, nn th ca qu trnh nn thc t khc vi nn

l thuyt.

Biu l thuyt ca qu trnh nn kh

HUMG 2015


Trong thc t ngi ta thng dng th ch th kim tra cc qu trnh lm vic ca my

nn. Phn tch th ch c ch n nh hng ca khong hi v b qua nh hng ca

cc yu t khc, ta thy c bn cht ca qu trnh nn.

Biu qu trnh nn thc t Biu ca qu trnh nn l thuyt

3.4.3 nh hng ca khong khng cht

Xilanh ca my nn lun c lm c khong khng gian cht. iu ny cn thit trnh

s va p ca piston vo np my khi hnh trnh ca n n im cui.

Khong khng gian c hi thng c nh gi bng s phn trm so vi th tch lm vic

ca xilanh v c gi l th tch tng i ca khong khng cht:

a =

Trong cc loi my nn 1 cp hin i a = 0.025 0,06 (khi kha c phn b np).

Trong khi nn nhiu cp, cc kha c phn b b mt sn ca xilanh a 0,2.

S hin din ca khong khng cht dn n: qu trnh ht khng bt u ti thi

im bt u ca hnh trnh ngc ca piston, m thi im cui ca qu trnh dn n (ti

im 4). Suy ra, th tch ht vh m thc t piston ht c nh hn th tch lm vic ca

xilanh vh < vlv. Th tch ca khong khng cht c nh hng xu n s thi ca my nn.

Khi tng gi tr tng i ca khong cht c th dn n ng thc:

a(

)

v lu lng tnh theo biu thc sau s bng 0:

Q1 =* ( )+. T.K.vlv.n

Trong :

T - h s nhit, tnh nh hng ca s lm nng kh khi ht t b mt ca

kha v thnh xilanh;

K - h s kn, tnh nh hng ca s r r qua kha v cc vnh m ca

piston v xilanh.

HUMG 2015


iu ny thy r trn hnh: th ch th khi thay i khong khng cht

Khi tng vch, trc ta p dch chuyn sang tri, ng nn a bin phn b rng hn v

n mt gi tr gii hn no ca vch im 2 s trng vo im 3. Th tch thi bng khng,

lc ng nn v ng dn n trng nhau, my nn khng ht , khng thi.

Khong khng c hi nh hng n s thi cng ln khi h s tng p cng ln, v vy gi

tr tng i ca khong khng cht c chn cng nh khi h s tng p cng ln .

3.4.4 Cch b tr my nn nhiu cp

My nn nhiu cp c lm theo 2 cch chnh:

loi c piston dng vi sai v mt s cp nn trong mt xilanh

loi c nhiu cp nn trong cc xilanh ring r.

Ta xt mt s trng hp.

a. My nn 2 cp c piston vi sai tc dng 2 hng

Trong my nn loi ny cc cp nn c b tr theo 2 bn ca piston. Nguyn l lm vic

c th biu din r rng bng th ch th, c xy dng chung cho c 2 cp.

Nu gi s rng my nn ht khng kh t kh quyn, th ng ht ca cp u tin s nm

thp hn mt cht so vi ng p sut kh quyn. Khi chuyn ng ca piston sang phi

xy ra qu trnh ht vo cp u theo ng 4-1, nn v y ca cp th 2 theo ng 3-2

HUMG 2015


v 2-3. Khi piston bt u di chuyn sang tri, cp u xy ra qu trnh nn, cn cp

th 2 xy ra qu trnh dn n kh. Qu trnh cui xy ra n khi no p sut trong xilanh cn

cha t ti p2 ti im 4. Ti thi im ny van ht ca cp th 2 m v piston, khi

chuyn ng sang tri, s ht kh t khong khng kn ca thit b lnh. V lc ny p sut

kh s gim. Khi piston chim c v tr xc nh bi im 2, p sut kh thit b lnh

gim n chng no van y ca cp th nht m v kh s t cp th 1 qua thit b lnh vo

cp th 2. p sut kh thay i theo ng 2-3. Vo lc u ca hnh trnh v pha bn

phi cp th 1 xy ra qu trnh dn n kh theo ng a bin 3-4. Th tch ca cc

xilanh ca cp 1 v cp 2 khng bng nhau, v vy th ang xt c t l v trc honh

khc nhau. Trong my nn loi ny qu trnh nn cc cp c thc hin nhng hnh

trnh khc nhau ca piston, v v vy lc tc dng ln cc phn ca khung c phn b kh

u.

b. My nn 2 cp c piston vi sai tc dng 1 pha

c bit ca my nn loi ny l s phn b cp th nht v cp th 2 theo mt pha ca

piston; iu ny dn n: qu trnh ht cng nh qu trnh y xy ra trong c hai cp l ng

thi. Khi bt u t im 3 trn hnh 8.4, vi chuyn ng ca piston v pha phi xy ra

qu trnh dn n cp th 2 n p sut p2, p sut ny c to thit b lnh bi cp khi

hnh trnh ca piston sang phi. v tr ca piston c xc nh bi im 4, van ht ca

cp th 2 m v xy ra qu trnh ht kh t th tch kn ca thit b lnh. y cng l qu

trnh dn n kh theo ng a bin 4-1. cui qu trnh ny p sut trong cp th 2 gim

n p1. Khi hnh trnh ca piston tip tc sang tri cp th 2 kh b nn theo ng 1-2

v c thi ra theo ng 2-3 vo ng y. Trong thi gian ny cp th nht xy ra qua

trnh nn theo a bin 1-2 n p sut p1. Ti im 2 van y ca cp th nht m v kh

b y t cp vo khoang kn ca thit b lnh. Qu trnh din ra theo ng a bin 2-3 v

gy ra s tng p sut t p1 n p2. Khi hnh trnh piston sang phi xy ra qu trnh dn n

v ht cp th 1.

HUMG 2015


Trong my nn loi ny cc khoang ca cp 1 v2 lun lun c phn cch bng

nhng van ng, nhng vn c nhng qu trnh, xy ra ng thi cc khoang ca mt cp

no y v ca thit b lnh.

Thit b lnh: ngoi cng dng chnh ca n l lm lnh kh nn, n cn ng vai tr nh mt

bnh cha tc l dung tch nhn kh ra t cp th 1, sau s kh vo cp th 2.

Trong my nn c piston loi vi sai tc dng 1 pha ny, qu trnh nn v thi kh xy ra c

2 cp ng thi, do trong phn khung ca my nn sinh ra nhng lc ln phn b khng

u, i hi s dng bnh c khi lng ln cn bng cc lc ny. S ny thng

dng trong mt t hp vi s thun dng i vi loi my nn c s cp ln hn 2.

c. My nn 3 cp c piston vi sai

S my nn 3 cp c piston vi sai

S my nn 3 cp c piston vi sai c s

phn chia cp th 1

d. My nn nhiu cp c piston vi sai

Khi s dng nguyn l to cp vi piston c ng knh thay i, c th thit k my nn

vi khi lng ln cc cp.

Ti liu tham kho

1) Cc qu trnh, thit b trong cng ngh ha cht v thc phm, tp 1, Nguyn Bin

2) Gio trnh bm qut my nn, T.s L Xun Ha Th.s Nguyn Th Bch Ngc

3) Bm qut my nn trong cng ngh, G.s TSKH Nguyn Minh Tuyn

4) V nhiu ti liu khc

btl bom quat may nen

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