Tuyen tap Cdng trinh Hdi nghi Khoa hoc Cff hoc Thiiy khi Todn qudc, Phan Thiet, 2008 377 Md phong he thong phun trirc tiep nhien lieu khi thien nhien nen trong dong ca dot trong danh liia cu ong birc[.]
Trang 1Tuyen tap Cdng trinh Hdi nghi Khoa hoc
Cff hoc Thiiy khi Todn qudc, Phan Thiet, 2008 377
Md phong he thong phun trirc tiep nhien lieu khi thien nhien
nen trong dong ca dot trong danh liia cu-ong birc
Le Van Tuy, Phan Minh Due
Trudng Dgi hoc Bdch khoa-Dgi hoc Dd Niing
Tdm tdt: Khi thiin nhiin nen (CNG) Id mdt trong nhirng nhien lic'u thay thi tricn vgng
cho vdn di gidm thieu d nhiim mdi trudng vd da dgng hda nguon nhiin lieu, lie thdng
phun CNG true tiip cho phep ndng cao ty so nin dgng ca vd td chirc qud trinh chdy
phdn lap de ndng cao hiiu sudt cdng sudt ddng ca vd tiet klim nhiin lliu
Bdo cdo trinh hay phuang phdp md phdng mdt hi thdng cung cdp CNG bdng phirang
phdp phun true tiip vdo trong xy lanh ddng ca dugc diiu khiin bdi van thuy khi
-diin tir Kit qud nghiin ciru cho thdy -diin biin cdc thdng sd dgng lire hge thuy khi
cua CNG trong hi thdng phun true dip: qua do cho phip phdn tich dnh huirng cdc
thdng sd kit cdu cimg nhu van hdnh din chdt lugng phun nhdm tdi uu hi thdng phun
Khdc vdi hi thdng phun nhiin lieu long truyin thdng, md hinh \di hi thdng phun true
dip CNG kiiu vdi phun mgt Id, dudng kinh Id phun Idn vd dp sudt phun thdp (4,4 din
8,4 MPa) vdn bdo dam chdt lugng cdp nhiin liiu td chirc chdy vin hda khi phdn lap
A Simulation of CNG Direct Injection System for Spark
Ignition Engine
Abstract: Compressed natural gas (CNG) is one of alternative fuel to reduce exhaust
gas emission and diversify fuel for internal combustion engine CNG direct Infection
provides ability of increase of compression ratio, therefore engine power and fuel
economy This paper presents simulation of a CNG direct infection system with
electro-hydraulic injector for spark Ignition engine Dynamic of the CNG In the
system with varied system geometry and operational condition was analyzed and
optimized The results revealed a reversed trend compared to injection system for
conventional liquid fuel: stratified charge could be achieved even with a large
diameter single-hole injector, low Infection pressure (about 4.4 to 8,4 MPa)
Keyword: Natural Gas, Spark Ignition Engine, Direct Injection, Stratified Charge
1 Gioi thieu :
Trude tinh hinh can kiet cua dau md va ap lyc ciia luat bao ve mdi trudng ddi vdi bau
khi quyen, ngoai cac giai phap hoan thien ddng co nhiim tiet kiem nhien lieu, ban che cac
chit thai ddc hai do dgng co ddt trong gay ra, viec tim kiem cac ngudn nhien lieu mdi thay
the, la myc tieu hudng tdi ciia phan Idn cac nghien cuu phat trien hien nay tren the gidi; va
dd cung la muc tieu hudng tdi cua dc tai Trong cac loai nhien lieu mdi sach, thi nhien lieu
khi thien nhien nen CNG {Compressed Natural Gas) dugc cac nha khoa hoc quan tam hang
diu vi day la ngudn nhien lieu sach va day trien vong cho old sinh thai trong tuang lai [I,
8]
Nhien lieu CNG dugc menh danh la nhien lieu eye sach nhd thanh phan carbon chua
h-ong nhien lieu la thip nhit trong tat ca cac nhien lieu hydrocarbon CNG la ngudn nhien
lieu triln vgng vi chung phan bd <Tlu khip tren trai dat va vdi trii' lugng cd the khai thac
trong vdng 250 nam tdi trong khi diu md chi cd the diing trong vdng 50 den 60 nam nira
Trang 2Md phdng he thdng phun true tiep nhien lieu khi
378 ^ !biin nhiin nen trong ddns caddnh lua eir&ng buc
Mgt uu dilm ndi bac nira cua CNG la nd cd tinh chiu nen lot va tinh chdng kich nd cao
{nh& chi sd Octane cao ed the len din 130) [8] nen cd the img dung lam nhien lieu khdng
nhiing thuan Igi ddi vdi dgng ca xang ma ca dgng co diesel dudi diing dgng co da nhien
lieu (Bi-fuef) hoac ddng ca kep {sir dung ddng thai hai logi nhien lieu : Dual-fuef) [6, 7]
Trong ngi dung bai bao nay, chung tdi se trinh bay kha nang ung dung CNG tren dgng eg Diesel cd ty sd nen cao bang phuang pbap phun trye tiep nhien lieu CNG vao trong xy lanh dgng eg
Cung gidng nhu xang vii LPG, nhien lieu CNG ciing de xuat hien hien lugng kich nd khi sir dung trong dgng co cd ly sd nen cao Theo ket qua nghien ciru cua nhicu tac gia \e dgng CO CNG thi vdi hdn hgp) ddng nhat cd ty le tucmg duang gan vdi ly thuyet, nhien lieu CNG ehi cd the phat huy hieu qua vdi dcmg co cd ly sd nen cd lgi khoang e = 1 1^12 [17]
De cd the irng dung CNG trong dgng ca cd ly sd nen cao nhu diesel, nhat thiet phai su dung cdng nghe phun true ticp CNG vao trong xy lanh dpng co [2, 3, 12, 13]
Nham phat huy the manh vc kha nang chiu nen cao ciia nbicn lieu CNG, hicn nay cac nghien cun phat trien tren the gidi dang tap trung nghien cuu ung dung nhien lieu CNG trong ddng ca diesel theo kieu dgng co Dual-Fuel bang phuong phap phun true tiep ap suat
cao HPDl {High Pressured Direct Injection) vdi ap suat phun CNG Icn den 3000 H- 3600
[Psi] nhd cdng nghe kieu vdi phun ket hap Diesel-CNG [14, 15]; trong dd lugng phun diesel chu yeu dung lam mdi lua cho nhien lieu CNG; khi can thiet cd the thay the cho CNG vdi ty trgng cao ban
2 X a y d y n g m o hinh he thong p h u n t r y e tiep nhien lieu C N G dieu khien dien tu-:
De tranh su phu thugc vao dau md, chiing tdi tap trung nghien ciru kieu vdi phun CNG don, ddc lap dicu khien bdi kieu van dicn tir kep [10, 11], nham xay dyng md hinh he thdng cung cap nhien lieu thuan CNG cho dgng co theo cdng nghe phun hai giai doan : phun sdm
de tao hon hgp ddng nhat loang va phun mugn de tao hdn hap phan IcDp DISC {Direct
Injection Stratified Charge) [4, 5], Vice moi lira se dugc thyc hicn bang vdi phun diesel
mdi hoac buji danh lira Kieu vdi phun true ticp CNG don, dgc lap ma chiing tdi dua ra dya tren nen tang cong nghe vdi phun cao ap dicu khien dicn tir kieu Common Rail; trong dd nhanh dieu khien dung bai van dicn lir etc dicu khien bai van nap - xa dgc lap Trude het, de
tai nghien ciru vdi phun vdi kieu van dicn tir don thong dung {van phdn phdi nap - thdi phu
thudc - dieu khiin b&i mdt van dien tir), duac the hien bang so dd md hinh hda nhu tren
hinh H I 1 [9]
Tir so dd md hinh hda cac phan tir tren hinh 111.1, chung tdi xay dung sa dd md hinh tinh loan cho he thdng dugc chi ra tren hinh HI.2; trong dd : cac khoang chua nhien lieu CNG (3, 5, 13 16, 18 20) dugc thay the bdi cac dung tich Vj tuang irng ; cac tuang tac tir bien (1, 8, 10, 22, 27) Icn he thdng dugc thay the bdi cac "dieu kicn bicn" - ki hieu B, - va dugc d^c trung bdi cac phuang trinh dac tinh bien tuang irng ; cac phin tu lilt luu dugc thay the bdi tiet luu Urang duong va dugc dac trung bing kha nang thong qua la (pS)k, trong^do p la he sd luu lugng cdn S la dien tich tilt dien thdng qua ciia tilt luu, va k la chi so^bieu thi cho tiet luu thir k Vdi cac tilt luu chi dan thuin la dudng ong (hoac lo thdng) giua cac dung tich tbi dien tich till dien thong qua la khdng ddi; cdn ddi vdi cac van tilt luu
thi tiet dien thdng qua la thay doi theo muc do md van
Trang 3Li Van Tuy, Phan Minh Dire 379
25 26 27
uy^ W^ l a ' ^ 20/
PTinh Hl.l: Sa dd md hinh hda cdc phan tir cua hi thdng phun CNG true tiep
(MSJ,
Vs
) ( ( M S ; ,
\ / i
Ve
fnSJ7 )|( (nSJ7
^ ^
Va
) ( 0 S ) c
\ / 7
— » — (Bf)
;B4I
I
t
Vl
X
( M S J 2
©
///»^ ///,2,- 5(7 dd md hinh tinh todn cho hi thdng phun CNG true dip
Tir phuang trinh can bing luu lugng ddi vdi cac dung tich V, ( ^ ^ ^ = Q) ^^^ P^^P ^
xac dinh phuang trinh vi phan xac djnh luu lugng khdi lugng Gi [kg/s] (hay the tich Q, [mVs]) luu lai trong cac dung tich Vj:
Trang 4380
Md phdng he thdng phun true tiip nhien lieu khi thien nhiin nen trong ddns ca ddnh lua cuong birc
~dt
^ V dp dV ^
(2.1)
(2.1b)
J
kp, dt dt
Cdn cac luu lugng qua cac tiet luu dugc xac dinh dya tren phuang trinh Becnuli tdng quat:
^ + J
r 2 \
v 2 y
ov
-I- — dx + g.dhj -0
dt
(2.2)
Bang each trien khai phuong trinh Becnuli (2,2) rdi bien ddi ta se cd phuong trinh vi phan
md ta chuyen dgng ciia ddng khi qua cac tiet luu tuong irng cd dang chung nhu sau :
-{.,s,)
-IJ V-J J
la':
( * - l )
\n )
dv
2 1:
dt
(2.3)
k P, k-\p, 1 - KP.y
dv v' ' dt ^-' 2
Vdi : {khdng ed Id van) j 1
\ ' ^ z
. ^H;^
(2.4)
(2.5a)
(cd Id van)
t-'y =
' ^
(2.5b)
V o \2
s VJ
v ;
Cae phuang trinh tir (2.1) din (2.5) se duac khep kin khi cac dilu kien bien cua he dugc
xac dinh
a) PhuoTig trinh can bdng chuyin ddng tgi niit bien dinh piston B^:
lp2k'-kk')+PA:^ + P,,ii-k;ff = [Fj + x,c, + p, ^
d.x,
nd dv,
dt (2-0^
b)^ Phuang Irinh can bang tgi mil bien Bj ndi v&i xy lanh ddng ca : Ap dung djnh luat nhi?t ,
ddng hge thir nhat ddi vdi hon hgp cdng tac tinh theo gdc quay true khuyu a ta cd cac ^
Trang 5Le Vdn Tuv, Phan Minh Dire 381
phuang trinh vi phan bilu diln sy biln thien ap suit, nhiet do va thi tich chira moi ifhit trong xy lanh dgng ca :
dp _ I
da " V
dT ^
— = T
da
+ —
\^dp_ ]_dV_
p da V da
dQ _A,h{T-T,)
da
V = TlD], 2R
( £ - 1 )
f
— + R
dV _ nD;,R,
CO
l - c o s a ) + L
R, sin ( 2 a ) 2L '
sin a
yj
(2.7b)
(2.7e)
'R^
s i n ' a
c) Phirang trinh cdn bdng chuyin vi tgi nut bien Bm xdc dinh qui lugt diiu khiin ciia van dien lir:
Xfmml
1 nnn
n Rnn
G 600
n <inn
n 9nn
-n -n-n-n J
0.0000 0.0005 ^
t1
/UO ]10
tn 0,0015
^
t
\ ^
\ 0,0020
th
t2
1
0,0025 o.oc
t [ s ]
Hinh H2.12b : Ddc tinh ndng van kiiu dien tir (Piezo Lift Function)
d) Phuang trinh cdn bdng trgng thdi tgi ngudn vdo BQ / ra 5^ • hang sd khdng ddi (dinh
trude)
Cuoi cimg xay dung dugc md hinh tdng quat cho phep tinh toan cac thdng sd ddng lyc bgc cua he thdng phun true tiep nhien lieu CNG dieu khien dien tir gdm 3 giai doan, gdm :
Trang 6382
Md phdng he thdng phun true tiip nhien lieu khi thien nhien nen trong ddns caddnh lua cuons birc
Giai doan 1 : qua do bat dau phun
Nhdnh phun:
dp 2
dt
dp,
dt
dt dt
= ( ^ 2 3 - ^ 3 4 J
kp^
V,
\6C,klkp,
\6CXjAt)^n^d:[kl-kl)kT,
Nhdnh diiu khiin :
<
^ = {Q.-Q.-Q
dt ^^'^ ^''' K3
dt v^
dPn _
dt
f n'd'
[j^^dp, [ ' dl
d^ V,
Giai doan 2 : Giai doan duy tri phun
+ [K-^D dp,^ dt \6C,kp^
(2.8)
(2.8b)
^,=(ai-Q.-Qj^
dt ^' ^
dj3, r
dt
\(CX dt ^' '^j)\6C,V,it)+n' \6C,V,it)+n'd;kp
dt ^^' ^ * v
(2.9)
Trang 7Li Vdn Tuy, Phan Minh Dire 383
Nhdnh phun:
dp 2
dt
dp,
dt
[Qn-QiX
2 J 4
K V
\6CX
dp, dp,
dt dt
W
2)
= (^23-^34 J
Vdi A = ^^C,k'-kp
i6c,kXit)+n'd:(k:-k:)kp,
Giai doan 3 : Giai doan qua do ket thuc phun
Nhdnh phun:
r
dp
dt
dp
kp,
'\6C,kX{t) + n'd:(k:-k:)kp,
Nhdnh dieu khiin :
*'=(a,-e.-eJ*^ dt
dp
V
dt
dPe
-{Q.s-Qsi,) kPs
V,
dt
dp,
= {Qs.-Qe.-Qj'^'^' ^ 6
^"dU,2dp
16C k V k dt + ik:-kl) i\dp2
dt
\6C^kp.,
\6C,V,{t) + n'd;kp,
^ = ((9 -0 )
dt
kPi
V,
(2.9b)
(2.10)
(2.10b)
Cd dugc phuang trinh tich phan xac dinh lugng phun nhien lieu cung cap chg dgng ca trong mdt chu trinh lam viec :
/
m = \
eye J k,\3V '"' ( i - 1 ) 1
-Pi)
-11 j-^
(2.11)
Trang 8384
Md phdng he thdng phun true tiep nhien lieu khi thiin nhien nen trong đng ea đnh lira cuans birc
3 Mot so ket qua dat duoc ciia mo hinh :
Kit qua tinh toan vl lugng phun chu trinh cho bdi mo hinh dat dugc la m,nj = 17,098
[mg/inj] vdi thdi gian phun hieu qua xac dinh bdi md hinh t.nj = 0,700 [ms] {ung v&i 2,73
dp gdc quay tnic khuyu) So vdi ket qua thyc nghiem cua John T Kubesh [16] thi lugng
phun chu trinh dat dugc d ciing cbc do phun la nicyc = 17,094 [mg/inj ]; sai sd vap phai 0,234%o< I%ọ
m «l«h»n«iẠ«rd>.™ nh«iliiu*WI>li>)M*»l>l'«n*Jn»c«Dlwl-(llthtoh»lMm«n^li»pCWaa
n -•.''C'l iM- t > u i # ( X I
" i v i bwadV l u ^ aio v^i, »oi iikuú [ Tlr^t.^ %f 1-3 ii: ••••-1 vp p'uj, i- tfr^ w | l"^ (••*(• 1C'(^ ' *;•• JPr^-J.^r, l»! j ^-jsm | [-^(.^rf-iif rjtf vl 1.- (jyt^ i-^ipt.or
I •
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CKJU) uiui,' uio,"- ;í.tií ujj'O '.'U-ij Hu)* uu/ị' 'Íty-i b<n^- uiu»
i r ' i U j « JM * i s r j i x i Ji"is m i j )>>* J«:x> IAUJ* m ạ'jinoi
Í.iu; '-lAijL :•'»-«/> UIM;.' OWO iíSi ] j - « :i*iB jK L^ j » ; * 1; II i i i n :»
I ii:»i:: nọ.-*
ạ j40tr :««»i "^1 r.L
j> 0 * i f tinh dfi-h i-huwn m4ycac i o n o i j i«i/;)/iu/i Yi /m/rj/ fe/ C>,ir u/iA ất tU^n 0i(ini^ qua c^k- v«n Mb/>Aun 5.' [mm"}]
Hinh H3.1 : Dien hien cdc đc tinh dong-ma cac van vol phun
> M a M n ailii uirdi^V fitiitn k w kM Itirin nhiin M n « n g sa OiM*l • [Mb M l h phun i n c b<p C N d
o i l a i t r d U i
JJ'j: i«:|^ 1_S2'^^"'.^?'#!5£' ii;r^ nn*r :*ij i u •s*;' J l>«rB !>««•» d|i M*\ • * Vu k^.«|t*-'t pkvn
»L' OMK :J:':» ccL'ig c.)::;: ĐOM
yii^'- i U r t iMM l i i ; i j t t i i ^ H l i i n l i S i Mucu -jtuM M.fl;ir>ị|
j ; 0 » m trfn ^ - jttdl diai khJn dp su^i phun f (lUir tj
puoo ctwc coot?- DttB? oLDic cOd: •.•<x\* oooi:- 0COỈ QOD:? oatc*
iL'st in*", l u * IK u i > i : r i ! i i J i n mfii i c n u^-u i t i i r t i J t i fc) O i m iN.r/1 luu itAJnf, 4fi4U cik: »vin »dtf ^-jAtwr ^) /.yn-'-^.j/
Hinh H3.2 : Diin biin cdc dgc tinh lim luang vd dp sudt
mm-M?:^
Trang 9Le Vdn Tuv Phan Minh Dire
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I T:,C:it C-ji.Ji^ J;.c, p,-ii'.i,x'j,;.[: | Vit ! « • <|,ia« b-; dinj tliini U; ,gj , i , 1 Cjh- ?<i » 'Jl " *" IWj! 'Ci r*»^
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i
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KM mn m e JJMT w - t y"'> T^'- ra* < " * " " ' ' MU,'ICAII
ai Diin bit'n kV io donf qua IS u n «J W >« pAiin v /m'j)
um^tj-QOiio oiko: O'jts aau^T nic-o aa?-; nor* ':-»IT O-JCIS ax:; oac«
ia;ii J3« iMB jr.u 3*-:t 3JMS ifc-o iMiJE -Mac M-u )*187J>e|
bt Goc ma CI ldo}, d^ xuyen :hau Stinvn} idirJd tijphun MfmnlsJ
P'^v-y
///«/z / / i , i Diin biin mot sd thdng sd ddng hoc nhien lieu khi qua vdi phun
Cac ylu to anh hudng din chit lugng phun : Lugng phun chu trinh phu thugc bac hai
theo ap suit phun pf, dudng kinh lo phun {vd ty sd duang kinh Id phun) nhung chi phy
thudc bac nhit theo thdi gian phun
minj [mg/inj]
35 -r
30
25
20
15
10
5
0
11,186.|),2-64,1)75,p, + 82,131
Xk[mm] 0.350 0.300
0.250 0.200 0.150 0.100
— 0.050 0.000
3.9 4.0 4.1 4.2 4,3 4.4 4,5 4.6 4.7 4.8 4.9
ap suit phun Pf [MPa]
Hinh 4.1 : Diin biin luang phun chu trinh khi thay ddi dp sudt phun
Trang 10386
nirj Img/inj]
Md phdng he thdng phun true tiep nhien lieu khi thien nhiin nen trong ddns ca ddnh lira cuonis birc
m,n, = 1,0375.[)p'- 11.£05 Dp-;.9.628
tn, : 0,0838
^
Dp- 1,2:22
0,300 0.250 0.200 0.150 0.100 0.050
0,000 15,5 15.6 15.7 15.8 15,9 16.0 16.1 16.2 16.3 16,4 16.5
Difang kinh piston 6ieu khiSn kim phun Dp Imm]
Hinh 4 2 : Dien biin luang phun chu trinh khi thay ddi du&ng kinh phun
vfk.^^\rl i<>f « u i - l J- I iJ o-B ^ -.liJiT i m J.- C4:ii:X> i;i.4ljii:i: ».iJ.»a.-U a - - ' ' " I Pitfl t i f f ar 3 0 1 1 ? tol l i m * i » 5 i r i j ( » '
I M i
• 1 i f
-I i -I
~ r ^ ' — • • • ; :
i ; ) i i o « t : i i « Oijm; i : / < « • « : II-JT «•*«: I U » J <U)';;
il;' t 7>.l U.V i < « LlA •£ / i l l •*_; < j j j Ji ;.•_
'/ D i ^ ij*r.T J t ' A A S ( i f i ( A.'-ii't, J;' M^i/ ;.'\itir P !5^'^
1
1
il
i Jl
1 J
1
1
1
1
: \
Jl ;—
\
;i '•
1
'1 •
KM !i:o I:JJ lujo i:w ;(:» i;'« :t:w i:m aow; i:'«
4A>U' A/V JIIU -JIM X>-'^ -JJJ« tLA ti'U >^'U M.^ >; U.|-^l i'l D ( ^ t»;r! ^(W itfi^?7W"tJi" <«•: -wf p^"Q jvrr.'-i-'iS
Hinh 4.3 : Diin biin luong phun chu trinh khi thay ddi thai gian phun
mini [mg/injl inj Ims]
30 T ,- i n
25
-20 ^
15
10
5
0
-m r i = :5.617.1, i
0,3 0.4 0.4 0.5 0.5 0
Thd'i gian duy tri p
8.9046
l|n| =
6 0
l u n t, [m
0,9988.1,
6 0 s]
^ 0,3806
- 2.5
• 2.0
- 1 5
- 1.0
- 0,5
8
Hinh 4.3b : Sir biin ddi Iwo'ng phun chu trinh, hru luang phun theo th&i gian t