1

NGHIN CU XC NH MT S THNG S CHNH CA H THNG TI PHUN SNG CA NH GIM HOM CY GING LM NGHIP

L Xun Phc

Vin Khoa hc Lm nghip Vit Nam TM TT Nhu cu cy ging cht lng cao cho trng rng nc ta ngy cng ln. Phng php gim

hom ph hp nht vi iu kin Vit Nam p ng yu cu trn v m bo hiu qu cao. Nghin cu c cha y v ng b cho thit k nn cht lng ti nc phun sng cc nh gim hom (NGH) trong nc cha m bo yu cu cng ngh, lm gim rt nhiu t l hom ra r v cht lng cy hom, tng chi ph sn xut,... Bng thc nghim kt hp l thuyt, chng ti chn c: loi vi phun thch hp cho cng ngh gim hom (Coolnet C20 vi 4 u phun), xc nh c cc thng s c bn ca h thng phun sng (p sut phun 3,5- 3,6 kG/cm2, khong cch vi phun 65 cm, chiu cao vi phun so vi mt bu m 30 cm), phng php xc nh s vi phun ti a trn nhnh phun v la chn my bm t cht lng ti tt nht vi chi ph hp l. Kt qu ny l c s khoa hc cho tnh ton thit k, lp t h thng ti phun sng cc NGH lm nghip nhm khc phc tn ti trn.

T kho: H thng ti nc phun sng, Vi phun, My bm, Mi trng gim hom.

M U Cht lng cy ging quyt nh rt ln n nng sut, cht lng ca rng. Phng php nhn

ging bng hom cnh (gim hom) m bo tnh di truyn y t cy m, h s nhn cao, khng cn thit b hin i v u t ln nn rt ph bin trn th gii v ang c p dng kh rng ri nc ta. Kh nng ra r v pht trin ca hom ph thuc rt nhiu vo m khng kh v gi th trong mi trng gim hom (MTGH). H thng ti phun nc dng sng m c bit quan trng trong vic to m MTGH ph hp cung cp nc cho hom, gim nhit MTGH khi nng nng, chng kh ho cho hom gim. Nhiu loi nh knh c th nghim gim hom cy lm nghip song hiu qu rt thp do t l ra hom r khng cao, chi ph thit b v chi ph sn xut rt ln song vn khng to c mi trng ph hp theo yu cu cng ngh. Vit Nam, nhiu NGH c nghin cu, xy dng song vic thit k, lp t cc h thng ti vi cc thng s kt cu v ch s dng,.. rt khc nhau, cha theo mt tiu chun thng nht, cht lng ti phun thp, cha to MTGH thun li cho qu trnh ra r v sinh trng ca cy hom. Cc nhc im c bn ca h thng phun sng: ti mn ca ht nc ( phun ti) rt thp, chnh lch ln v lng nc ti trn mt lung gim hom, tha nc lm ng gi th, lng nc phun ra ngoi lung qu nhiu, loi bm khng ph hp vi h thng phun gy ra lng ph ln v chi ph thit b my, in nng,.. Mt s thit b phun sng cht lng cao (i Loan, Ixraen,..) c th nghim cho cc h thng ti trong nng nghip t kt qu tt song cha c kim nghim, nh gi s ph hp vi cng ngh gim hom cy lm nghip Vit Nam. Bi vy, vic nghin cu b sung c s khoa hc cho tnh ton thit k, ng dng cng ngh, thit b mi, lp t h thng ti phun sng trong cc NGH nng cao cht lng ti nc, gim chi ph l rt cn thit v c ngha thc tin cao.

NI DUNG V PHNG PHP NGHIN CU Ni dung nghin cu - Xc nh cc thng s k thut v xy dng c tnh thc nghim ca mt s loi vi phun

sng lm c s chn loi vi phun v cc thng s k thut ph hp cho h thng ti. - Xc nh cc thng s k thut chnh ca nhnh phun sng trong lung gim hom. - Xc nh cc thng s chnh, ch lm vic ca my bm ca h thng ti. Phng php nghin cu Xc nh cc thng s k thut v xy dng c tnh thc nghim ca mt s loi vi phun

sng. Loi vi phun v p sut phun thch hp cho h thng ti ca NGH c la chn m bo cc

yu cu: ti mn cao, chnh lch lng ti thp, tit kim nc; bn knh phun ph hp vi b rng lung gim hom (BL) c ph bin trong sn xut... Cn c la chn da trn cc c tnh sau y ca vi phun v theo trnh t sau:

- Quan h ti mn ca ht nc - p sut phun, bn knh phun - p sut phun Rf = f(p), lu lng phun p sut phun q = f (p) chn loi vi phun, p sut phun ti thiu (pmin) cho cc th nghim tip theo.

- Quan h gia chnh lch lng nc ti q1 trn din tch phun ca 1 vi phun v p sut phun: q1 = f (p) chn p sut phun thch hp nht (p0) cho loi vi phun m bo q1 nh v p sut

2

phun khng qu ln tit kim chi ph cng sut my bm v in nng. Cc c tnh v thng s nu trn thng khng c cung cp bi Nh sn xut, do vy phi xc

nh bng thc nghim. Xc nh cc thng s k thut ca vi phun bng thc nghim: S th nghim xc nh cc thng s xy dng c tnh ca mt vi phun nh hnh 1, khu

vc th nghim c che kn trnh sai s do nh hng ca gi, iu chnh van 4 v 7 to cc p sut phun theo yu cu t thp ln cao trong qu trnh th nghim.

- Xc nh p sut phun ti thiu (pmin) cho qu trnh th nghim bng cch tng dn p sut phun v quan st qu trnh phun, so snh mc phun ti thnh sng m ca chm tia phun vi cc h thng phun sng thng thng c trong sn xut chn pmin

- Xc nh phun ti bng phng php phn tch nh chp, kt hp xc nh c ht nc khi phun trn tm knh, so snh vi c ht nc khi phun khong p sut phun 3,5 4,0 kG/cm2 ca vi phun Coolnet (kch thc cc ht nc khong t 30 90 m [10] ).

a = 10 cmR10 = 10 cmR20 = 20 cm.......Rn = Rn-1 + 10 cm

1 23

4

6

7

8

1819

20

21

22

23

24

25

26

27

28

29

3031

32

R70

R60

R50

R40

R30

R20

R10

1

1

23

4 5 6 7 8

9

7

43

2

17 1615

14

13

12

11

10

9

8

40 c

m

5

R80

X

Y

Y

10

Hnh 1.

S th nghim xc nh cc thng s k thut ca mt vi

phun

1- B nc chm 2- ng ht ca bm, 3- ng x nc v b cha 4,7- Van iu chnh p sut, 5- My bm 6- ng trc chnh PVC D34 8- Cc thu nc ri 9- Tr phun v vi phun sng

10- ng h o p sut thy lc

- Xc nh bn knh phun ln nht ( Rf ) cc p sut phun p > pmin da trn vt nc ri trn mt phng nn th nghim.

- Xc nh lu lng phun (q) cc p sut phun (p): thu ton b lng nc phun ra trong mt n v thi gian.

- Xc nh chnh lch lng ti q1 bng cch s dng cc cc nha hnh cn ng nht v kch thc thu nc ri. Cc cc c xp trn mt phng nn ti cc giao im gia cc vng trn ng tm c bn knh cch u nhau 10 cm vi tm l chn tr phun v cc tia bn knh qua tm cch u nhau v gc (hnh 1). So snh lng nc thu c gia cc cc trn ton b th nghim. Chnh lch lng ti ln nht q1 trn ton b vng trn phun bn knh Rf ca 1 vi phun cc p sut p pmin theo cng thc:

q1 = 100. (qi - qTB) max /qTB (%), vi: qTB = (1

n

qi )/n (ml) (1)

qi (ml): lng nc thu c trn 1 cc, n: tng s cc thu nc trong vng trn phun qTB (ml): lng nc trung bnh trong 1 cc tnh trn tng cc cc trong vng trn Rf Vi phun sng c s dng th nghim gm 5 loi (hnh 2)

3

Hnh 2: Cc loi vi phun sng 1.Vi phun sng kiu tn p (VP1): thng

dng trong lm nghip do cc c s t nhn Vit Nam sn xut

2.Vi phun sng kiu dng xoy PS.97 (VP2): thng dng trong nng nghip - sn phm ti KHCN cp Nh nc Vin KH Thy li

3.Vi phun sng kiu tn p (VP3): i Loan 4.Vi phun Coolnet C20 (VP4): hng Netafim

(Ixraen) sn xut 5. Vi phun Coolnet C30 (VP5): hng Netafim

(Ixraen) sn xut

Xc nh cc thng s k thut chnh ca nhnh phun sng trong lung gim hom Kt cu lung gim hom thng dng c m t trn hnh 3.

1101300

280

130

600 6

7

3-4%

8

9

h p1

2

3

4

5

h hom

h bau

10

Hnh 3. Kt cu lung gim hom thng dng ci tin v nhnh ti phun sng [5] 1- Rnh thot nc, 2 ng thot nc, 3- Thnh lung gim hom (xy gch); 4- Khung thp vm che (thp D8), mt ngoi ph nilon trong sut 5- Cp nilon, 6- Thanh nh v khung vm 7- Vi phun sng, 8- Tr phun sng, 9- Trc nhnh phun sng, 10- ng phn phi kh (thng gi nng hoc lnh) ch c NGH quy m sn xut cng nghip vi cc thng s MTGH c iu khin t ng

Hom c gim trc tip trong bu t c v mm bng ti nilon. Loi bu m ch yu c ng knh 5 6 cm, chiu cao 10 11 cm [4], [7]. Mt s thng s k thut ca lung gim hom c tiu chun v p dng trong sn xut: b rng lung 1,1 1,3 m, chiu di lung 3 20 m. H thng ti phun sng bng my bm in v vi phun sng VP1, khong cch vi phun 9,0 1,2 m, chiu cao vi phun so vi mt bu m 20 30 cm.

Cc thng s chnh gm: - Khong cch vi phun lin tip trn nhnh ti (Lp) - Chiu cao vi phun so vi mt bu m (hp) - S vi phun ti a cho php trn mt nhnh phun (nmax) tng ng vi mi loi ng dn Tiu ch la chn: - La chn Lp, hp m bo chnh lch lng ti phun q2 trn mt lung gim hom p sut

phun p0 nh nht cho php. - La chn nmax tng ng vi Lp, hp, p0 m bo chnh lch lu lng phun q ca cc vi phun

trong ton b nhnh ti trong phm vi cho php. Tnh ton xc nh cc thng s ca nhnh phun: - Xc nh khong cch vi phun l thuyt trn mt nhnh ti (Lmax) tng ng vi p sut phun

p0, bn knh phun Rf, b rng lung BL nhm m bo ton din tch trong lng lung gim hom u c ti phun [4] (hnh 4).

Na

O

b m c

O1

D

K

l3

Din tch tui lp

Tm vi phun

Lung gim hom

Hnh 4: Phng php xc nh khong cch vi phun l thuyt

trn nhnh ti

Lmax = OO1 = 2 (OM2 - MK

2)

1/2 = 2 (Rf

2 - BL

2/4)

1/2 = (4Rf

2 - BL

2)

(m) (2)

3

4 5

2 1

4

- Xc nh s vi phun ti a cho php trn mt nhnh ti (nmax) da trn l thuyt tnh ton tn tht p sut thy lc. S tnh ton ti hnh 5 v phng php tnh ton nh sau:

po

qoF

l3l3

L4 E

D

qo

(n-1)qonqo

2qo

0

Q

L1 2 3 (n-1) n Hnh 5: S phn b lu lng trn nhnh phun trong lung gim hom

Cc thng s chn tnh ton: - p sut phun ca vi phun cui nhnh (th n): p0

- Chnh lch p sut phun cho php gia vi phun u v cui nhnh [p] - Khong cch vi phun khng i v bng l - Trc nhnh phun ng nht v loi ng dn v ng knh ng (d). Loi ng dn ph bin

hiu qu v thun tin nht cho cc h thng ti trong nng lm nghip l ng uPVC vi c ng tiu chun ti thiu c ng knh ngoi x dy = d x b = 21 x 1,5 mm.

Trong h thng phun sng (hnh 7) s dng ng uPVC, do lu lng phun ca vi phun nh, tc dng chy v ma st trong cc on ng dn khng ln nn c th xem dng chy trong cc on ng l chy tng, b qua tn tht cc b ca dng chy khi phn nhnh v mi vi phun c lu lng phun bng q0.

p sut thy lc (ASTL) ti u nhnh phun (mt ct D) phi tha mn: p1 = pD = pDE + pEF + p0 = p4 pEF: Tn hao ASTL trn on tr phun ca vi phun th n (c ng knh d, chiu di l4):

pEF = p5 pDE: Tn hao ASTL trn on trc nhnh ti DE Tn tht ASTL dc ng trn on ng l: hd = .l.v

2/ (2.d.g) = 8 l q2/ [ (3,14)2g.d5 ] (mH2O)

Vi: v : Vn tc dng chy trung bnh trong ng: v = 4.q/ (3,14 d2) (m/s) l : Chiu di on ng (m) d : ng knh trong ca ng (m). Re: Tr s Raynon Re = v.d / = 4.q/ ( 3,14.d. ) : H s nht ng hc ca nc (ph thuc nhit ca nc) Vi nhit nc ti trung bnh 250C = 0,9* 10-6 (m2 /s) : h s ma st thy lc, do dng chy tng: = 64/ Re = 50,24 .d. / q Trn cc on ng dn ca nhnh phun c lu lng nc chy qua (qi) v h s ma st ca dng

chy (iqo) khc nhau nn chnh lch p sut ti 2 im D v E c tnh:

p4 = pDE = 1

2{8. / [ , . ]}

n

i

liqo iqoq

2 5

3 14 g d

Cn c gin phn b lu lng nc trong cc on ng (hnh 5) xc nh c: p4 = 8.l3. q0

2 [(q0 + 4 2q0 + 9 3q0 + + n

2 nq0]

/ [(3,14)

2.g.d3

5] (3)

S vi phun ti a trn mt nhnh ti tha mn iu kin: p4 = pDE [p] (mH2O) (4)

- Xc nh khong cch vi phun thch hp nht (Lp) bng thc nghim: la chn Lp, xc nh mc chnh lch ln nht q2 gia lng nc thu c trn tng cc v

lng nc trung bnh trn ton b cc cc trong th nghim (hnh 6) vi chiu cao vi phun so vi mt bu m mc trung bnh ph bin trong sn xut, p sut phun p0 v mt s mc khong cch vi phun L L max.

q2 = 100. (qi - qTB) max / qTB (%), vi: qTB = ( 1

m

qi ) / m (ml) (5)

5

R 60+R 50+

1 3

2

4 75 6

8

h p

1 2 3 4 5 6 7 8 9 10 1112 13

b b b b b b b b b b b b

Lp Lp

R 40+

R 20+

R 20-

R 40-

R 60-

R 30+

R 10+

R 0

R 10-

R 30-

R 50-

5

Hnh 6. S th nghim xc nh khong cch vi phun trn mt nhnh ti

1- B nc chm, 2- ng ht ca bm, 3- My bm (Hmax > 50 mH2O)

vi: 1 kG/cm2 = 10 mH2O 4- Van iu chnh p sut, 5- Cc thu nc 6- Vi phun Coolnet C20

7- ng h o ASTL 8- Thnh lung gim hom.

qi (ml): lng nc thu c trn 1 cc, m: tng s cc trong th nghim (2 Lp x BL ) qTB (ml): lng nc trung bnh trong 1 cc - la chn hp: xc nh mc chnh lch ln nht q3 gia lng nc trong tng cc v lng

nc trung bnh trn ton b cc cc trong th nghim (theo hnh 6) vi khong cch vi phun Lp , p sut phun p0 v mt s mc chiu cao vi phun h h min = (hhom + 10) cm

hmin: chiu cao vi phun ti thiu theo phng thng ng so vi mt bu m hhom : chiu cao ngn hom so vi mt bu m (ph bin 10 cm)

Xc nh cc thng s chnh, ch lm vic ca my bm ca h thng ti. * La chn my bm da trn 2 thng s k thut chnh - p sut bm (ct p) Pb (mH2O, kG/cm

2) m bo p sut phun p0 ti vi phun xa nht:

Pb ( p0 + p max ) (6) p max : tn hao p sut thy lc trn ng ng dn tnh t bm n vi phun xa nht, - Lu lng cp ca bm Qb (lit/gi, m

3/gi) tng ng vi ct p Pp: Qb Nvp .q0 (7) Nvp : tng s vi phun hot ng ng thi trong h thng: Nvp = m.n. q0 m : s nhnh phun, n : s vi phun/ 1 nhnh * Xc nh ch lm vic ca my bm c qua s vi phun ti a cho php hot ng ng

thi trong h thng ti phun xc nh: Nvp = Qb / q0 (8) pmax c xc nh bng thc nghim. Trong h thng ti phun sng khi s dng ng dn

bng nha uPVC v c lp ghp ng yu cu k thut: pmax 0,3 0,4 kG/cm2

pmax c th xc nh theo l thuyt thy lc hc da trn s tnh ton trn hnh 7

A

C

B

D

E

l2

l 2

D

C

D

DL1

l3

F

i1

i2

Hnh 7. S nguyn tc kt cu v tnh ton p sut thy lc

h thng ti phun sng trong nh gim hom

AB- Trc chnh (ng uPVC D34), BC- Trc phn phi (ng uPVC D34) CD- Cm van kha iu chnh p sut DE- Trc nhnh ti (ng uPVC D21) EF- Tr phun (ng thp m km D15)

pmax= pAB + pBC + pCD+ pDE + p EF = p1 + p2 + p3 + p4 + p5 (mH2O) (9)

p1, p2, p3, p4, p5 : Tn tht p sut thy lc (ASTL) trn cc on AB, BC, CD, DE, EF Cn c la chn bm v xc nh ch lm vic ca bm: da trn ng c tnh lu lng

p sut: Qb = f (Pb) ca bm do nh sn xut cung cp hoc c xc nh bng thc nghim theo s th nghim hnh 8.

6

3

4

2

1

5

6

Hnh 8

S th nghim xc nh c tnh ca my bm bng thc nghim

1- B nc chm, 2- ng ht ca bm, 3- Van iu chnh p sut, 4- My bm th nghim, 5- ng h o p sut thy lc 6 Thng cha (km cc o lu lng) (hoc b cha km thc o th tch).

My bm nc c nghin cu th nghim gm 3 loi s dng in p 1 pha, cng cng sut (1,5 Hp), khc nhau v cp ct p cc i (Hmax) theo tiu chun (hnh 9)

Hnh 9:

Cc loi my bm c nghin cu th nghim 1- Bm B1: 220V, 1,5 Hp, Hmax = 52 mH2O 2- Bm B2: 220V, 1,5 Hp, Hmax = 33 mH2O 3- Bm B3: 220V, 1,5 Hp, Hmax = 22 mH2O

Ghi ch: 1 kG/cm2 = 10 mH2O

KT QU NGHIN CU & THO LUN Xc nh cc thng s k thut v xy dng c tnh thc nghim ca mt s loi vi phun sng.

Kt qu nghin cu xc nh c cc c tnh lm vic ca 5 loi vi phun nh trn hnh 10, 11 v mt s thng s k thut chnh nh sau:

Quan h gia bn knh phun v p sut phun Rf = f (p)

55

60

65

70

75

80

85

90

95

100

105

110

1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4.0

p sut phun (kG/cm2)

B

n k

nh

ph

un

(c

m)

VP1 : Vi phun sng tn p VN VP2: Vi phun sng tn p i Loan

VP3 : Vi phun dng xoy PS97 VP4 : Vi phun Coolnet C20

VP5 : Vi phun Coolnet C30

VP1

VP3

VP2

VP4

VP5

Quan h lu lng v p sut phun ca cc loi vi phun

-

20

40

60

80

100

120

140

160

1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6 2.8 3 3.2 3.4 3.6 3.8 4.0

p sut phun (kG/cm2)

Lu

u l

ng

n

c

ph

un

(li

t g

i)

Vi phun VP 1 Vi phun VP 2 Vi phun VP 3

Vi phun VP 4 Vi phun VP 5

VP1

VP3

VP2

VP5

VP4

Hnh 10: Quan h gia bn knh phun

v p sut phun ca cc vi phun Hnh 11: Quan h gia lu lng nc phun

v p sut phun ca cc vi phun - p sut phun ti thiu m bo phun ti ca vi phun PS 97 thp nht, trn 1,6 kG/cm2, ca

cc vi phun VP1, VP2 trn 1,8 kG/cm2. Vi phun Coolnet ch bt u phun c p sut trn 2,6

kG/cm2 v khi p sut phun trn 3,0 kG/cm2 phun ti t mc rt ln.

- Mc tng lu lng phun theo p sut ca vi Coolnet C20 v C30 rt t, song mc tng ny ca cc vi phun VP1, VP2 v VP3 rt ln. Lu lng phun ca vi Coolnet C20 thp nht (khong 20 lt/gi), ca vi phun Coolnet C30: 30 lt/ gi, ca vi phun VP1 ti 80 lit/gi (gp hn 4 ln vi phun

1

2

3

7

Coolnet C20), ca vi phun i Loan (VP2) ti 120 lit/gi. - Bn knh phun ca cc loi vi phun tn p (VP1, VP2) tng ln nhanh theo p sut phun sau

li gim nhanh v t ln nht khong 105 cm. Vi b rng lung gim c tiu chun (BL = 110 130 cm), khi s dng cc loi vi phun ny, lng nc phun ra ngoi lung rt nhiu. Chm tia phun ca vi phun VP3 dng hnh nn vi y pha trn nn khng ph hp vi lung gim hom c vm nilon do chm tia b nilon cn li v ngng t thnh dng chy. Bn knh phun ca vi phun Coolnet lun tng theo p sut phun v gn nh khng tng khi p sut phun vt mc 3,5 3,6 kG/cm

2 v bn knh phun ti a ch t 80 82 cm.

Do cn phi to c m khng kh rt cao trong MTGH chng mt nc cho hom gim, lung gim hom c vm nilon bao ph gi m v gi th c ti m cn thit trc khi gim hom nn lng nc ti phun nh k ch cn rt t b lng m mt i do qu trnh bay hi qua cc khe h ca vm nilon v chng ng nc gi th. Bi vy, loi vi phun Coolnet C20, C30 rt ph hp cho h thng ti phun to m v gim nhit cho MTGH nht l cc NGH cng nghip c cc h thng iu tit tiu kh hu c iu khin t ng. Loi vi phun Coolnet C20 tit kim nc hn nn c chn cho nghin cu.

Kt qu kho st c tnh ca vi phun Coolnet loi 4 u phun trn hnh 12, 13, 14:

.0

10.0

20.0

30.0

40.01

23

45

6

7

8

9

10

11

12

1314

151617

1819

2021

22

23

24

25

26

27

28

2930

31 32

ng R40 ng R50 ng R60

ng R70 ng R80

0

5

10

15

20

25

30

35

40

1 3 5 7 9 11 13 15 17 19 21 23 25 27 29 31 1

Gc

L

n

g t

i /

n v

d

in

tc

h (

ml)

Vng bn knh R40 Vng bn knh R50 Vng bn knh R60

Vng bn kinh R80 Vng bn knh R70

Hnh 12:

Bin dng phun ca vi phun Coolet C20 v C30

Hnh 13:

khng u lng ti phun theo phng bn knh phun (Vi phun C20, p sut phun p0 = 3,6 KG/cm

2)

- Phn b lng nc ti trn 1 n v din tch tp trung ch yu vng bn knh R25 R55 cm. cng xa tm vi phun, lng ti cng gim

- Khi tng p sut phun, chnh lch lng ti gia cc vng bn knh cng nh. - Bin dng vt nc ri trn mt phng ngang hnh hoa th, do vy khi lp t cn xoay cc vi

phun lin tip trn nhnh ti lch vi nhau 1 gc bng 450 (hnh 15) lm u lng ti trn mt lung gim hom.

8

0

5

10

15

20

25

30

35

R10 R20 R30 R40 R50 R60 R70 R80

Bn knh phun

R (cm)

L

n

g p

hu

n t

rn

1

n

v d

in

tc

h q

(m

l)

p sut phun 3,0 kG/cm2 p sut phun 3,2 kG/cm2

p sut phun 3,4 kG/cm2 p sut p =3,6 kG/cm2

p sut phun 3,8 kG/cm2 p sut phun 4,0 kG/cm2

Hnh 14

Quan h gia lng phun trung bnh trn 1

n v din tch v bn knh phun cc p sut phun khc

nhau

(vi phun Coolnet C20)

1,3

m2

3 4

5

Lp Lp

1 2

3

45

Hnh 15: S b tr vi phun Coolnet trn lung gim hom

1- Vi phun,

2- Bin dng ti phun, 3- Hng tia phun 4- Thnh (b) lung GH; 5- Vng ti lp ca 2 vi phun Lp - Khong cch gia hai vi phun

Hnh 16: cho thy, khi s dng vi phun Coolnet C20, khng nn tng p sut phun qu 3,5 3,6 kG/cm

2 do m bo phun ti cn thit, chnh lch lng ti gim rt t trong khi chi ph

cng sut my bm, in nng tng ln nhiu v gim kh nng ti phun ca bm

60

70

80

90

100

110

120

130

3.0 3.2 3.4 3.6 3.8 4.0

p sut phun (kG/cm2)

Chn

h l

ch l

ng t

i t

rn v

ng

trn p

hun

q1

(%)

Hnh 16

Quan h gia chnh lch lng ti trn 1 n v din tch trn ton din tch phun

v p sut phun (Vi phun Coolnet C20)

Xc nh cc thng s chnh ca nhnh phun sng trong lung gim hom: Kt qu xc nh c nh sau: Khong cch vi phun (Lp) v chiu cao vi phun so vi mt bu m cy (hp): Khi s dng vi phun Coolnet C20 p sut p0 = 3,5 3,6 kG/cm

2, bn knh phun Rf 75 cm v

b rng lung gim BL = 130 cm, theo cng thc (2), khong cch vi phun ti a theo l thuyt: L max 75 cm, chnh lch lng ti trn mt lung gim hom tng ng vi 5 mc khong cch vi phun: Lp = 50, 55, 60, 65, 75 cm v 5 mc cao vi phun hp = 20, 25, 30, 35, 40 c

xc nh bng thc nghim v nu trn hnh 17 v 18.

9

50

55

60

65

70

75

80

85

55 60 65 70 75

Khong cch vi phun Lp (cm)

Ch

n

h l

c

h l

ng

t

i

q

2

(%)

50

55

60

65

70

75

20 25 30 35 40

cao vi phun hp (cm)

Ch

n

h l

c

h l

ng

t

i

q

3

(%)

Hnh 17. Quan h chnh lch lng ti trn

mt lung gim hom v khong cch vi phun (Vi Coolnet C20, p = 3,6 kG/cm

2, hp = 30 cm)

Hnh 18. Quan h chnh lch lng ti trn mt lung gim hom v cao vi phun

(Vi Coolnet C20, p = 3,6 kG/cm2, Lp = 65 cm)

- Khi gim khong cch vi phun (Lp) hoc tng chiu cao vi phun so vi mt bu m (hp), chnh lch lng ti phun q2, q3 trn mt lung gim hom u gim.

- Khng nn gim Lp di mc 65 cm (v s lng vi phun trong lung tng ln, lm tng chi ph ch to lp t v chi ph sn xut trong khi chnh lch lng ti phun gim khng ng k).

- Khng nn tng hp qu 30 cm (v th tch khng gian trong MTGH tng ln lm tng chi ph cng sut thit b v chi ph nng lng cho vic iu tit nhit MTGH trong ma lnh).

S vi phun ti a trn mt nhnh ti phun: Kt qu nghin cu, tnh ton xc nh c chnh lch p sut phun trong nhnh ti theo

s vi phun ti bng 1 vi cc thng s tnh ton nh sau: - ng knh trong ca ng dn trc nhnh phun uPVC D21: d3 = 17. 10

-3 m

- Khong cch vi phun l3 = Lp = 0,65 m - Lu lng phun ca vi phun Coolnet C20: q0 = 20 lt/gi - Nhit nc ti trung bnh 250C: = 0,9* 10-6 (m2/s) - Chnh lch p sut phun cho php [p] gia vi phun th nht v vi phun th n (cui nhnh)

c chn ty theo yu cu chnh lch lu lng phun gia cc vi phun trong di p sut phun m bo phun ti (p p0) cn c hnh 11 v cng thc (3)

p4 = 8.l3. q02 [(q0 + 4 2q0 + 9 3q0 + + n

2 nq0]

/ [(3,14)

2.g.d3

5] [p]

Bng 1. Quan h gia s vi phun trong nhnh ti v chnh lch p sut phun

S vi phun trn 1 nhnh phun (n)

10 11 12 13 14 15 16 17 18 19 20

Chnh lch p sut phun trong nhnh

(mH2O)

0.38 0.49 0.61 0.74 0.89 1.05 1.23 1.41 1.62 1.83 2.06

Chnh lch p sut phun trong nhnh

(kG/cm2)

0.04 0.05 0.06 0.07 0.09 0.11 0.12 0.14 0.16 0.18 0.21

Theo kt qu thc nghim v quan h gia lu lng phun - p sut phun ca vi Coolnet C20, gia 2 mc p sut phun 3,4 v 3,6 kG/cm2 (chnh 0,2 kG/cm2), lu lng phun tng ng: 19,50 v 20,18 lt/gi, mc chnh lch l 3,4 % nh vy s vi phun ti a trong 1 nhnh phun c th chn 15 - 19 chic. Xc nh cc thng s chnh, ch lm vic ca my bm ca h thng ti

c tnh quan h gia lu lng cp Qb v p sut y Pb T c tnh thc nghim ca 3 loi my bm cng cng sut (hnh 19) cho thy: - Kh nng to c p sut ca 3 loi rt khc nhau. Bm c thng s Hmax cng ln, to c p

sut ti ca y cng cao.

10

Quan h gia lu lng cp Qb v p sut y Pb ca 3 loi bm nc

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

11000

12000

0.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

2.2

2.4

2.6

2.8

3.0

3.2

3.4

3.6

3.8

4.0

4.2

4.4

4.6

p sut (kG/cm2)

L

u l

ng ( l

t /g

i )

Bm B2: 220 V / 1,5 Hp

Hmax = 33 mH2O

Bm B1: 220 V / 1,5 Hp

Hmax = 22 mH2O

Bm B3: 220 V / 1,5 Hp

Hmax = 52 mH2O E

D

C

B

A

Hnh 19: Quan h gia lu lng cp ca bm v p sut y Qb = f (Pb)

- Quan h Qb = f(Pb) nghch bin, do vy nu ti mn ca ht nc cha t do p sut phun thp, cn kha bt nhnh phun gim s vi phun hot ng thi p sut phun ca cc vi phun cn li s tng ln. Cng mc gia tng p sut Pb nh nhau, lu lng cp ca bm B3 gim t nht cn lu lng bm B1 gim nhiu nht. So snh 2 bm B2 v B3, nu cn bm hot ng vng Pb > PE s dng bm B3 hiu qu hn bm B2 v ngc li.

Khi s dng cc loi vi phun kiu tn p v kiu dng xoy (VP1, VP2, VP3), m bo phun ti sng m cn thit, cn p sut phun p0 = 1,6 1,8 kG/cm

2, p sut y ca bm cn 1,9 2,0 kG/cm

2. T cc ng c tnh Qb = f(Pb) cho thy s dng bm B2 s cho lu lng cp Qb = QA ln

nht ngha l cho php nhiu vi phun hot ng ng thi trong khi tiu th cng sut in nh cc bm B1, B3.

Khi s dng vi phun Coolnet C20, p sut phun p0 = 3,5 3,6 kG/cm2 bm cn to c p

sut 3,8 3,9 kG/cm2 nn ch c bm B3 p ng c yu cu.

La chn my bm cho h thng phun sng Vi h thng phun sng c th, cc thng s k thut ch yu ca bm (Pb, Qb) cn t c

tnh theo cc cng thc (6) v (7) - Lu lng ca bm khi c s vi phun lm vic ti a Nvp : Qb = Nvp.q0 (lt/ gi) - p sut y cn thit ca bm tng ng vi Qb: Pb = p0 + pmax (kG/cm

2, mH2O)

- Xc nh ta im X0 (Pb, Qb) trn th c tnh Qb = f(Pb) ca nhiu bm khc nhau. Loi bm c chn thch hp nht phi c ng c tnh i qua X0 hoc nm pha trn gn nht im X0.

Xc nh s vi phun ti a cho php hot ng ng thi vi loi bm c - Xc nh p sut cn thit ca bm trong h thng: Pb = p0 + pmax - Xc nh im D trn th c tnh Qb = f(Pb) c PD = Pb v gi tr Qb = QD (hnh 19) - S vi phun ti a cho php hot ng ng thi vi bm c: Nvp = QD/ qo Khi s dng bm B3 nu trn cho h thng phun sng ca nh gim hom vi loi vi phun

Coolnet C20, m bo cht lng ti, s vi phun ti a cho php hot ng ng thi khong 125 vi.

KT LUN 1- Loi vi phun Coolnet vi 4 u phun thch hp nht cho cc h thng phun sng to m v

lm mt khng kh cho NGH lm nghip do to c phun ti rt cao v tit kim nc trong vi phun Coolnet C20 ph hp nht, lng tiu th nc t nht (20 lt/gi). p sut phun thch hp nht vi vi Coolnet C20 ( t cht lng phun cao v chi ph cng sut my in nng hp l) t 3,5 3,6 kG/cm

2 v cc vi phun lin tip nhau trn cng nhnh phun cn c lp lch nhau gc 450.

2- H thng phun sng trong mi lung gim hom khi s dng vi Coolnet C20 ch cn 1 dy (1 nhnh) v khong cch vi phun thch hp nht 65 cm, chiu cao vi phun so vi mt bu m 30 cm. Chiu di nhnh phun, tng ng l s vi phun /mt nhnh, cn c hn ch m bo s ng u v lng ti v phun ti trong ton nhnh. Nn s dng h thng ng dn chm mt nn NGH bng loi ng tiu chun uPVC chu c p sut ti thiu 6 bar (tng ng 6,12 kG/cm2) gim chi ph

11

u t v tn thp p sut thy lc trn ng ng. Trc nhnh phun ch cn c ng D21, s vi phun ti a trn nhnh phun nn t 1519 chnh lch lng ti gia cc vi phun di 5%.

3- My bm c cp ct p cc i Hmax < 20 22 mH2O khng s dng c cho cc h thng phun sng. My bm c Hmax = 30 35 mH2O thch hp nht cho cc h thng ti phun sng khng cn phun ti ln, s dng loi vi phun sng kiu tn p (VP1, VP3) v dng xoy (VP2). H thng ti phun bng vi phun Coolnet C20 v C30 ch hot ng hiu qu vi loi my bm c cp ct p Hmax > 50 mH2O.

TI LIU THAM KHO 1- Bi Hiu, L Th Nguyn (2004). K thut ti tiu nc cho mt s cy cng nghip, Nh xut

bn Nng nghip. 2- L nh Kh, Dng Mng Hng (1988). Gio trnh ci thin ging cy rng. 3- L Xun Phc (2007). Kt qu bc u nghin cu ci tin nh gim hom cy ging lm nghip.

Tp ch khoa hc lm nghip s 2/2007. 4- L Xun Phc v cc CTV (2009). Nghin cu mt s gii php k thut nhm ci thin mi

trng nhn ging cy rng bng hom cnh trong vng chu nh hng ca gi Lo v gi ma ng Bc. Bo co tng kt ti, Vin Khoa hc Lm nghip Vit Nam.

5- Nguyn Ti (2008), Thy lc, Nh xut bn Xy dng. 6- i s qun Ixraen (2004). Kinh doanh nng nghip, c hi hp tc gia cc cng ty Israen & Vit

Nam.

7- Trung tm Nghin cu Ging cy rng (2010). Bo co kt qu xc nh di bin cc thng s mi trng ph hp cho gim hom mt s loi cy rng - ti trng im cp B Nghin cu cng ngh che sng v ti phun t ng cho vn m cy lm nghip

8- Gislerod, Hans R. 1983. Physical conditions of propagation media and their influenceon the rooting of cuttings: The effect of the greenhouse environment on the temperature of propagation

media. Pant and soil.

9- Hess, Charlers E. and Snyder. 1995. Interrupted mist found superior to constant mist in tests with cuttings.

10- Netafim, Coolnet for evaporative cooling, humidifying, rooting and chemical applications. Email: postmaster@netafim.com * website: www.netafim.com

DEVELOPING A SYSTEM FOR MIST IRRIGATION IN THE CUTTING HOUSES

Le Xuan Phuc

Forest Science Institute of Vietnam

SUMMARY In Vietnam there is an increasing demand of high quality genetically improved seedlings for forest

plantation establishment. Most seedlings are propagated as cuttings as this is a relatively simply

technology which allows for efficient rapid production and can be undertaken at a local level by rural

communities.

However there can by production issues which may prevent satisfactory production such as inadequate

misting irrigation reducing the striking rate of cuttings leading to reducing seedling quality.

The results of testing various misting systems indicates that the Coolnet sprayer, Model C20,

manufactured by Netafim, is suitable under Vietnam conditions when operated with 4 spraying units at

a spraying pressure of 3.5 to 3.6 kg/cm2 covering a width of 65 cm at a height of 30 cm.

Keywords: System of mist irrigation, Sprayer, Water pump, Cutting environment

Ng i thm nh: TS. on Vn Thu