CB LƯU LƯỢNG VÀ MỨC

7/31/2019 CB LU LNG V MC

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CM BIN O LU LNG V MC CHT LU

1. Khi nim chung

2. Cm bin o lu lng v vn tc3. Cm bin o mc cht lu


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KHI NIM CHUNG

icngvclucht v lulng: C ba trng thi kttp chnh l rn,lng v kh.

Trong trng thi kh, cc phn tchuynnghnnt do,

v th cht kh chim ton b th tch bnh cha, khng phthuc kch thckhong khng gian bnh cha trong nhitkhng i.

Trong trng thi rn, vtcht c mtth tch nhtnh v mt

hnh dngnhtnh. Cc cht trng thi rn chia thnh hailoi: cc tinh th v cc cht v nh hnh. Cc phn tchtrn, tinh th hay v nh hnh, ch dao ng quanh mtv trnhtnh.


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KHI NIM CHUNG

Trong trng thi lngvtcht c hnh dngph thuc hnh dngbnh cha v c th tch khng i. Cc phn tchtlng phnbtheo mt cu trc nht nh no , chng lun lun dao ngquanh v tr cn bngmtthi gian rilichuyn sang v tr cn

bng mibng cch i ch, chnh v vy cht lng c th tchnhtnhnhng khng c hnh dngnhtnh


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KHI NIM CHUNG

Chtlu (hay lucht) l tn gi chung chtlng v kh. Clucht lbphncachc nghin cuchuynng

ca cc mi trnglng v kh v tng tc ca chng vicc vtrn c bin gii chung (nh bnh cha).

Trong chcchtlu,cu trc phn tthcca cc chtlng v khc thay thbng khi nim l tng ha vmt mi trngvtcht c hai tnh chtcbn: tnh lintc v tnh linh ng (tnh chy).

Lu lng l lng cht lng hay cht kh chy qua titdin ngang ca dng chy trong mtnvthi gian.


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KHI NIM CHUNG

Lu lng c th o bng [kg/s] hoc bng [m3/s ]Nu tnh theo th tch th lu lng Q:

Q = v.S

Trong : vl vn tc cht lng ti tit din ang xtSl din tch tit din ca dng chy

Nu cht lng chy theo ng v khng chu nn th lulng Ql khng i mi tit din.


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KHI NIM CHUNG

My o lu lng cht lu thng qua ng dn c gil lu-lng-k hay cng-t lu lng, ch th lu lngtrung bnh chy trong mt khong thi gian.

Trng thi mi trng o, thng phi c quy i viu kin tiu chun: nhit o T = 200C;

p sut kh quyn P=101325 [Pa]= 760 [mm thy ngn];

m tng iRH%=0[%]).


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2.1. LU LNG V N V O

a) Lu lng : lng cht lu chy qua tit dinngang ca ng dn trong mt n v thi gian.

Lu lng th tch (Q) tnh bng m3/s, m3/gi ...

Lu lng khi lng (G) tnh bng kg/s, kg/gi...


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2.1. LU LNG V N V O

Lu lng trungbnh:

Lu lng tc thi:

dt

dVQ

hoc dt

dm

G (m3

/s)

t

VQtb

t

mGtb

(m3/s) (kg/s)hoc


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2.1. LU LNG V N V O

b) Phng php o: m trc tip th tch cht lu trong mt khong

thi gian xc nh t.

o vn tc cht lu khi lu lng l hm ca vntc. o gim p khi lu lng l hm ph thuc

gim p. Tn hiu o bin i trc tip thnh tn hiu in

hoc nh b chuyn i in thch hp.


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2.2 CB O LU LNG THEO TH TCH

1.2.1. Nguyn l o: m trc tip lng th tchcht lu i qua bung cha c th tch xc nhca cm bin.

dt

dnn - Tc quay ca trc lu k)(

nqdt

dNq

dt

dVQ vv Lu lng tc thi:

12

12vtb

ttNNq

tVQ

Lu lng trungbnh:

(qvth tch cht lu i qua cm bin trong mtvongquay ca trc cm bin)


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2.2.1 NGUYN L O

Phng php m s vng quay v o tc quay:

+ Dng nam chm quay + cun dy xung in.

+ Dng tc k quang.

+ Dng mch o tn s hoc in p.


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2.2 CB O LU LNG THEO TH TCH

1.2.1. Lu lng k bnh rng:

a) Cu to v nguyn l lm vic:

1&2. Bnh rng3. V

4. Cht lu5. Ca vo6. Ca ra

V1 2

1

3

4

56


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2.2.1 LU LNG K BNH RNG

v tr (a) cht lu lm quaybnh rng (2) y th tchcht lng (V1) sang ca ra ng thi lm bnh rng (1)quay theo (v tr b).

v tr (c) cht lu lmbnh rng (1) quay qu trnh lpli.

Th tch cht lu y sang ca ra:

V2

2 2

V1

2

1 11

021v V2VVq


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Thng o th tch cht lu V trong khong thigian t1 n t2:

( qc - h s lu lng k ; Nc1, Nc2 -s trn ch th calu lng k ti thi im t1 v t2)

1c2cc NNqV

m s vng quay hoc o tc Q tc trungbnh hoc Q tc thi.


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b) c im:Gii hn o t 0,01 - 250 m3/gi,

Cp chnh xc 0,5; 1, Tn tht p sut nh,

Yu cu cht lng o phi c lc tt,

Gy n khi lm vic.


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2.2.2 LU LNG K KIU CNH


1

2

3

2

4

2

2

5

1. V2. Cnh

3. Tang quay

4. Con ln5. Cam


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2.2.2LU LNG K KIU CNH

Th tch cht lui qua lu lng k trong mt

vng quay (qv) bng th tch vnh kh gia v v

tang quay.

m s vng quay hoc o tc nh c cu

lin kt vi trc lu lng k Q tc trung bnh

hoc Q tc thi.


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2.2.2 LU LNG K KIU CNH

b) c im:o lu lng cht kh.

o lu lng n 100 - 300 m3

/gi Cp chnh xc 0,25; 0,5.


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2.3 CB O LU LNG THEO TC

1.3.1. Nguyn l o:

Da trn quan h:

vtc dong chy;Stitdin ngang ca ng dn.

Bit S o v Q.

S.vQ


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2.3.2 LU LNG K TUABIN HNG TRC


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1

2

3

4

1. B chnh dngchy

2. Tuabin

3. B truyn bnhrng-trc vt

4. Thit b m


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o th tch cht lu i qua lu lng k trong khongthi gian t1 t2:

Tc quay ca trc tuabin: v.kn

Lu lng: nk

SS.vQ

12

NN

k

SV

(Vi - tng s vng quay ca lu

lng k trong khong thi gian t1 t2)

2

1

t

t

12 dt.nNN


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b) c im:ng knh tuabin t 50 300 mm,

Phm vi o t 50

300 m

3

/gi, Cp chnh xc 1; 1,5; 2.


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2.3.3 LU LNG K TUABIN TIP TUYN

a) Cu to & nguyn l lm vic:1

23

1. Tuabin 2. Mng lc 3. ng dn


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2.3.3 LU LNG K TUABIN TIP TUYN

b) c im:ng knh tuabin t 15 - 40 mm;

Phm vi o t 3 - 20 m3/gi;

Cp chnh xc thp 2; 3.


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2.4 CB O LU LNG THEO GIM P

1.4.1. Nguyn l o:

Da vo s ph thuc ca gim p vo tc cadng chy khi i qua tit dinb thu hp.

Kho st trng hp dng chy l tng qua mngchn (cht lu khng b nn).

F1F0

F2

W1 W2

p2p1

AB C


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2.4.1 NGUYN L O

Phnbvntccamt dngchy l tng qua thitb thuhp: (v) tng dn t v1 (A-A) t vmax (B-B) gim dn

n v3(C-C). Phn b p sut: (p) tng dn

t p1 (A-A) p1(trc mngchn), gim xung p2 (sau

mng chn) cc tiu p2 (B-B) tng dn tr li p3(C-C).

F1 F0F2

W1 W2

p2p1

p1

p2p2

p

p1

v1v2

p3

p

v3

A B C


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2.4.1 NGUYN L O

Vn tc dng chy ti B-B:

'2'122

2 pp2

m

1v

p1, p2 - .s. tnh ti A-A & B-B. - t trng cht lu. - h s tn tht thu lc.M=F0/F1 - t s thu hp ca TB, = F2/F0 - h s thu hp DC

21'2

'1 pppp Thay

21222 pp2

mv


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2.4.1 NGUYN L O

Lu lng:

212

pp24

dG

21

2

pp2

4

dQ

hoc

4

2c

Vi

Khi cht lu chu nn a vo h s hiu chnh

(


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2.4.2 THIT B THU HP

a) Mng ngn:

b ) Mng ngn

l hnh cn

c) Mng ngn

hnh phu

a) Mng ngn

chun


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2.4.2 THIT B THU HP

c im: Mng ngn chun (a) cu to n gin; d ch to, lp

t; tn tht ca dng chy lno lu lng cc dng

chy c tr s Re > Re ti hn. Mng ngn c l thu hp c bit (b, c) kh ch to; tn

tht ca dng chy nh; h s xc nh theo mi thitbo lu lng cc dng chy c tr s Re < Re ti

hn.


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2.4.2 THIT B THU HP

b) ng thu hp (ng venturi): Cu to:

c im: bin dng gn ging vi bin dng dngchy khi b thu hp; dng chy bin i t t tn tht

b; kh ch to v lp t.


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2.4.3 MCH O

a) Cc b phn ca mch o: Cc b phn c bn:+ Thit b thu hp;+ Thit b o p. Cc b phn khc:+ B bin i in;+ B tch phn lu lng;

+ B tnh khi lng cht lu;+ B tnh ton x l s liu;+ B bin i t trng cht lu


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2.4.3 MCH O

b) Yu cu lp t: L ca thitb thu hpphi ng tm vi ng

dn.ng o pphit ngay trc v sau thitb thu

hp. Trc v sau thitb thu hp, ng dnphi c

mt on thng khng thay i tit din, khngc van hoc cc vtcn lm thay i dng chyvichiu di cnthit.


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2.4.3 MCH O

c) Mt s mch o:

G

gh

a) ng Pito b) p k vnh khuyn c) Mng n hi


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2.4.3 MCH O

H thng o lu lng kiu

AB

a1

b1

a2

b2

12

3

4

5

6

7

8

9

10

14

15

16

10

11

12

13

1, 2 & 3) Cun dy v li st 4) B phn so snh 5) ng c xoay chiu6) Cam 7) Kim ch 8) ng c ng b 9&10) Chi in 11) Vnh bn khuyn

12 &13) Vnh khuyn dn in 14) Cun dy 15) Ly hp 16) Hp s

9

10

V tr chi than

trn vnh bnkhuyn


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2.5 CB O L .L THEO GIM P KHNG I


a) S cu tob) S c b bin i in

1. ng hnh cn2. Phao

3. Thc o

4. B bin i in

3P2

P1

G

1

2

4


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2.5 CB O L. L THEO GIM P KHNG I

Khi phao ang v tr cnbng, gi s Q tng p1tng phaob y ln tit din khe h (F) tng p1gim cho n khi t cnbng mi:

21 PGP S.pGS.p 21

const

S

Gpp 21

Lu lng: F.kp.2

F.Q

)constp.2

.k(

Q=f(F) Q ph thuc v tr phao.


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2.5 CB O L.L THEO GIM P KHNG I

b) c im v ng dng:

Cu to n gin;

D lp t.

ng dng: o lu lng nh.


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2.6 CB O LU LNG IN T


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a) Cu to & nguyn l lm vic:

N S

1

2

3 6

5

1 & 2. in cc

3. ng kim loi

4. Lp cch in

5. Nam chm

6. Milivn k

4


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Da vo hiu ng cm ng in t:

Khi cht lu c tnh dn in chy qua ng xut hinsut in ng cm ng:

Q.kQD

B4D.v.BE

(B- cng t trng; v- tc trungbnh ca dng

chy; D- ng knh ng; k =4B/D = const - h s tl)


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b) c im, ng dng: Khng cn phi o t trng cht lng,

Cc phn t ht, bt kh v tc ng ca mi trng

(nh nhit , p sut, ...) khng lm thay i dnin ca cht lu s khng nh hng n kt qu o.

ng knh ng t 10 1.000 mm;

Phm vi o 1 2.500 m3/gi vi v = 0,610 m/s, chtlu c dn in >10-5 - 10-6 simen/m;

Cp chnh xc 1; 2,5.


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3. CM BIN O MC CHT LU

3.1. Khi nim v phng php o3.2. CB o mc theo phng php thy tnh

3.3. CB o mc theo phng php in

3.4. CB o mc theo phng php bc x3.5. CB o mc theo phng php t gio

3.6. CB o mc theo phng php radar


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3.1 KHI NIM V PHNG PHP O

a) Khi nim:

o mc: xc nh mc hoc lng cht lu trongbnh cha (dng o lin tc)

+Xc nh ngng:pht hin mc ngng c thay khng (dng o theo ngng).


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3.1 KHI NIM V PHNG PHP O

b) Phng php o: Phng php thu tnh dng bin i in.

Phng php in da trn tnh cht in ca cht

lu. Phng php bc x da trn s tng tc gia bc

x v cht lu.


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3.2 CBM THEO PP THY TNH


a) Dng phao cu1. Phao 2. Dy mm3. Rng rc 4.i trng

5. CB v tr

c) Dng CB p sutvi sai1. Cmbin

2. ng ni

b) Dng phao tr1. Phao

2. Thanh truyn

3. CB o lc

1

2

1

2

3

1

2 35

4


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Trng hp (a): phao nng h theo mc cht lng omc o v tr bng CB o v tr.

Trng hp (b): mc cht lng thay i lc nng

phao thay i o mc o lcbng CB o lc:

Trng hp (c): mc cht lng thay i p sut p thayi:

o mc o lc chn lc p sutbng CB p sut visai.

gShPF

ghpp 0 ghppp 0


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S nguyn l cc phng n b tr CB:


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3.3 CBM THEO PHNG PHP IN

3.3.1. Cm bin dn3.3.2. Cm bin t in


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3.3.1 CM BIN DN

a) Cu to & nguyn l lm vic:

h h

hmin

a) CB o mchai in cc

c) Cm binpht hin mc

b) CB o mcmt in cc

hmax

in

cc 2

in

cc

1

~ 10V ~ 10V

incc 2

in

Cc 1

in

cc

1

in

cc

2


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3.3.1 CM BIN DN

Trng hp (a) v (b): Bin dng in trongmch t l chiu diphn in cc nhng trongkim loi: I0 = k.h.

Trng hp (c): Bin dng in trong mchtng t ngt khi cht lu chm in cc ccmc ngng.


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3.3.1 CM BIN DN

b) c im: Cu to n gin, d lp t;

D bin i thnh tn hiu in;

Ch o vi cht lu c dn in > 50Scm-1.


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3.3.2 CM BIN T IN

a) CB o mc cht lu khng dn in:

h

a) CB o mc 2 in cc

in

cc 2

in

cc 1

h

b) CB o mc 1 in cc

Thnh

bnh

in

cc

1

0

1

0

Do 10 mc cht lu (h) thay i Ct thay

i. o Ct h.


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3.3.2 CM BIN T IN

b) Cm bin o mc cht lu khng dn in:

h

Lp

cach

in

in

cc 1

in

cc 2

Mc cht lu (h) thay iSt thay iCt thay i .o Ct h.


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3.4 CBM THEO PP BC X

a) Cu to v nguyn l lm vic:1 2

3

a) Pht hin ngng

h

1 2

3

b) o mc lin tc

1. Ngun pht tia 2. B thu 3. Cht lu(60Co hoc 137Cs)


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Trng hp (a): Khi cht lu t ngng hp thtng nhanh chm tia gim mnh thay i t ngttn hiu ra gim t ngng.

Trng hp (b): Khi mc cht lu tng hp th tngdn chm tia gim dn tn hiu ra gim theo. Mc suy gim ca chm tia bc x t l vi mc cht lutrong bnh cha.


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b) c im: o mc khng cn tip xc vi mi trng o;

o mc iu kin mi trng c nhit , psut cao hoc mi trng c tnh n mn mnh.


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3.5 CBM THEO PP T GIO

T gio l hin tng mt vt t trong trng t schu tc dng ng sut ko hay nn. i vi cc chtst t, cc lc tc dng ny ln c th lm vt b

bin dng.

Cc my pht t gio o mc da trn nguyn l l sdng mt t trng ngoi to nn mt sng in-t

phn x trong ng dn sng lm bng vt liu t gio.


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Cm bin o mc kiu t gio

u d c to thnh t baphn t ng tm:

- Phn t ngoi cng lmt ng bo v.

- Bn trong ng ng dnsng, l phn t c todng lm bng vt liu t

gio.- Mt nam chm bn trong

phao.


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Mt xung in nh c to ra trong b phn in t camy pht v pht ra ng dn sng, to ra mt trngin-t dc theo chiu di ng ng. Khi t trng nytng tc vi t trng vnh cu ca nam chm gy nnmt xung sng.

Xung sng ny c phn tch nh xung hi v. Khongthi gian gia thi im pht xung thm d ban u v

thi im pht hin xung hi v c dng xc nhmc o vi kh nng thc hin v chnh xc cao.


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3.6 CBM THEO PP RADAR


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3.6 CBM THEO PP RADAR

Ttc cc kiuomc radar sdng nguyn l csl phng ra cc lung vi sng tcmbintu

bchahoc cc dng bnh cha khc.

Mtphnnnglngphnxngctrlicmbintbmtcachtco.

Khong thi gian chy ca tn hiu c dng lmthcomc.

CB LƯU LƯỢNG VÀ MỨC

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