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i hc SPKT Vinh Khoa: C Kh ng Lc
LI NI U
Trong bi cnh ca t nc ta hin nay v ang pht trin mt cch nhanh
chng v ang trn pht trin thnh mt nc cng nghip trong thi gian sp ti,
th vai tr ca ngnh ng c t trong ni chung v nn cng nghip t ni ring
rt l quan trng. C th hn th nn cng nghip t gp phn rt nhiu trong cc
ngnh nng nghip ,cng nghip ,dch v,v c bit l kh nng di chuyn rt linh
ng lm cho phn ln ngi dn Vit Nam chn t xe my lm phng tin
di chuyn qua thc y ngnh cng nghip t pht trin.Hc qua mn kt cutnh ton ng c t trong gip chng ta phn no c th hnh dung ra c cch
tnh ton thit k ra mt ng c t trong.V di y l bn thit k tnh ton ng
c t trong m ti p dng nhng kin thc v tnh ton ng c thit k.Hi
vng bn c c th c gp gip ti ti c th rt kinh nghim trong nhng bn
thit k tip theo.V xin cm n thy Phm Hu Truyn gip em tn tnh
trong qu trnh thc hin bn thit k.
Xin chn thnh cm n thy c!
Vinh,ngy 27 thng 12 nm 2010
Sinh vin thc hin
V nh Cng
CHNG ITNH TON CHU TRNH CNG TC CA NG C T TRONG
n : Mn hc CT SVTH: V nh Cng1
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i hc SPKT Vinh Khoa: C Kh ng Lc
1.1Trnh t tnh ton:
1.1.1S liu ban u:
1 Cng sut ca ng c Ne = 150 ( m lc
)
2 S vng quay trc khuu n= 3100 ( v/ph )
3 ng knh xi lanh D = 100 ( mm )
4 Hnh trnh piston S= 95 ( mm)
5 Dung tch cng tc Vh = 0.74613 ( dm3 )
6 S xi lanh i= 8
7 T s nn = 6.5
8 Th t lm vic ca xi lanh 1 5 4 2 6 3 7 8
9 Sut tiu hao nhin liu ge = 220
( g/ml.h)
10 Gc m sm xupap np 1 = 31 ( o )
Gc ng mun xupap np 2 = 83 ( o )
11 Gc m sm xupap thi 1 = 67 ( o )
Gc ng mun xupap thi 2 = 47 ( o )12 Chiu di thanh truyn ltt= 185 ( mm )
13 Khi lng nhm piston mpt= 1.187 ( mm )
14 Khi lng nhm thanh truyn mtt= 1.272 ( mm )
1.1.2 Cc thng s cn chn:
1. p sut mi trng : pk= 0.1 ( Mpa)
2. Nhit mi trng: Tk= 297 ( o k )
3. p sut cui qu trnh np: pa = 0.085 ( Mpa)
4. p sut kh thi: pr= 0.105 ( Mpa)
5. Mc sy nng mi cht: T = 6 ( o c)
6. Nhit kh st ( kh thi ): Tr= 1000 ( o k )
7. H s hiu inh nhit: t = 1.1
8. H s qut bung chy: 2 = 1
9. H s np thm: 1 = 1.0210. H s li dng nhit ti z: z = 0.85
n : Mn hc CT SVTH: V nh Cng2
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i hc SPKT Vinh Khoa: C Kh ng Lc
11. H s li dng nhit ti b b = 0.856
12. H s hiu nh th cng: d = 0.929
13. Ch s m a bin: m = 1.45
1.2. Tnh ton cc qu trnh cng tc
1.2.1. Tnh ton qu trnh np:
1.H s kh st r :
H s kh st r dc tnh theo cng thc
2
1
1 2
.( ) 1. .
. . .
k rr
r a mr
t
a
T T p
T ppp
+ =
=
1
1,45
1.(297 6) 0,105 1. .
1000 0,0850,105
6,5.1,02 1,1.1.0,085
r
+=
= 0.0699
Trong : m l ch s gin n a bin trung bnh ca kh st. m = 1,45
1.Nhit cui qu trnh np Ta:
Nhit cui qu trnh np Tac tnh theo cng thc:
1
1,45 1
1,45
( ) . . .
1
0,085(297 6) 1,1.0,0699.1000.
0,105350,5
1 0, 0699
m
ma
k t r r
r
a
r
a
pT T T
pT
T
+ + =
+
+ + = =
+
( oK )
Ta > 310 oK t yu cu
1. H s np v :1
1 2
1. . . . . .
1 ( )
mk a r
v t
k k a
T p p
T T p p
= +
=
1
1,451 297 0,085 0,105. . . 6,5.1,02 1,1.1.
6,5 1 (297 6) 0,105 0,085v
= +
= 0.8116
2. Lng kh np mi M1 :
Lng kh np miM1 c xc nh theo cng thc :
n : Mn hc CT SVTH: V nh Cng3
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i hc SPKT Vinh Khoa: C Kh ng Lc
3
1
432.10 . .
. .
k v
e e k
pM
g p T
=
Trong :
pe l p sut c ch trung bnh dc xc nh theo cng thc:
30. .. .
ee
h
NpV n i
=
Vh l th tch cng tc ca ng c c xc nh theo cng thc:
2 26. . 3,14.100 .95 .10 0, 74613
4 4hD S
V
= = = ( dm3 )
30.150.4
0,71550,74613.3100.8
ep = =
31
432.10 .0,1.0,8116 0,5516220.0.7155.297
M = = ( kmol/kg nhin liu )
2. Lng khng kh l thuyt cn t chy 1 kg nhin liu Mo :
Lng khng kh l thuyt cn t chy 1 kg nhin liu Mo c tnh
theo cng thc :
10,5120
0,21 12 4 32oC H O
M = + =
( kmol/kg nhin liu )
i vi nhin liu ca ng c xng ta c:C = 0,855 ; H = 0,145.
3. H s d lng khng kh :
Trng lng phn t ca xng l nl = 114 nn i vi ng c xng ta c:
1
1 10,5516
114 1,0602
0,5120
nl
o
M
M
= = =
1.2.2 Tnh ton qu trnh nn:
1. T nhit mol ng tch trung bnh ca khng kh:
19,806 0,00209. 19,806 0,00209.297 19,806vmc T= + = + = ( kJ/kmol. )
2. Tnhit mol ng tch trung bnh ca sn vt chy ( = 1).
51'' (17,997 3,504 ) (360,34 252,4 )102v
mc T = + + + =
n : Mn hc CT SVTH: V nh Cng4
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i hc SPKT Vinh Khoa: C Kh ng Lc
51'' (17,997 3,504.1,05) (360,34 252,4.1,05)102v
mc T= + + + =21,74337T
(kJ/kmol.)
3. T nhit mol ng tch trung bnh ca hn hp.
c tnh theo cng thc:'' '
'.'1 2
v r v vv v
r
mc mc bmc a T
+= = +
+
Ta t :
19,806v
a = , 0,02092
vb
=
'' 17,997 3,504. 17,997 3,504.1,0602 21,71197v
a = + = + =
( )''
51 . 360,34 252,4. .10 0,003142 2
vb
= + =
''
' . 19,806 0,0699.21,71191 19,9301 1 0,0699
v r vv
r
a aa
+ += = =
+ +
''
'.
2 2 0,00209 0,0699.0,003140,0216
2 1 1 0,0699
v vr
v
r
b b
b
+ + = = =+ +
Vy ta c t nhit mol ng tch trung bnh ca hn hp' 19,930 0,00216.297 20,5712v
mc = + = ( kJ/kmol. )
4.Ch s nn a bin trung bnh n1:
c tnh theo cng thc:
( )11 '
1'
8,3141
. . 12
nvv a
nb
a T =
+ + ( )1
1 1
8,3141
19,930 0, 00216.350,5. 6,5 1nn
=
+ +
( I )
Ta chn : n1 = 1.375 thay vo hai v ca phng trnh ( I ) ta c
phng
trnh tng ng : 0.375 = 0.3743
Sai s n1 = 0.1929 < 0.2%
5. p sut cui qu trnh nn pc :
p sut cui qu trnh nn pc c xc nh theo cng thc
1 1,375. 0,085.6,5 1,1147nc a
p p = = = ( MPa )
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i hc SPKT Vinh Khoa: C Kh ng Lc
6.Nhit cui qu trnh nn Tc:
Nhit cui qu trnh nn Tc c tnh theo cng thc :
1 1 1,3750 1. 350,5.6,5 707,2nc a
T T = = = ( oK)
7.Lng mi cht cng tc ca qu trnh nn Mc:
Lng mi cht cng tc ca qu trnh nn Mc c tnh theo cng thc:
Mc = M1 + Mr= M1. ( 1 + r) = 0.5516.( 1 + 0.0699) = 0.590
1.2.3: Tnh ton qu trnh chy :
1. H s thay i phn t l thuyt o :
Ta c tng mol M ca cc loi ng c c xc nh theo cng
thc:
M = 0.21.( 1 ). Mo + 14 32nl
H O
+
Nn h s thay i phan t l thuyt o c xc nh theo cng thc:
( ) o1
0.21. 1 . M4 32
11
.
nl
o
o
nl
H O
M
+ +
= ++
=
( )0,145 1
0.21. 1 1,0602 . 0,5120 4 1141 1.0381
11,0602.0,5120
114
o
+ = + =+
2. H s thay i phn t thc t ( do c kh st ).
c xc nh theo cng thc:
1,0381 0,06991,0356
1 1 0,0699o r
r
+ += = =
+ +
3. H s thay i phn t thc t ti im z ( z ) (do chy cha ht ):Ta c h s thay i thc t ti im z, z c xc nh theo cng thc
:
11 .
1o
z z
r
= +
+
Trong :
0,850,9930
0,856
zz
b
= = =
n : Mn hc CT SVTH: V nh Cng6
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i hc SPKT Vinh Khoa: C Kh ng Lc
1,0381 11 .0,9930 1,0353
1 0, 0699z
= + =
+
4. Lng sn vt chy M2 :
Ta c lng sn vt chy M2 c xc nh theo cng thc:
M2 = M1 + M = o.M1 = 1,0381+ 0,5516 = 0,5726 ( kmol/kg n.l )5. Nhit ti im z Tz :
i vi ng c Xng, nhit ti im z Tz c xc nh bng cch gii
phng trnh chy :
( )' ''.
1
( ). . . .
1
z H Hv c z vz z
r
Q Qmc T m c T
M
+ =
+ ( * )
Trong :
QH : nhit tr thp ca nhin liu ta c, thng thng c th chn
QH = 44000 ( kJ/kgnl ).
QH : nhit lng tn tht do nhin liu chy khng ht khi t 1 kg
nhin liu, thng thng c th xc nh QH theo bng cng
thc sau:
QH = 120.103.(1- )Mo (kJ/kgnl) khi < 1
QH = 0 khi 1 ''. vzm c : L t nhit mol ng tch trung bnh ca sn vt chy c
xc nh theo cng thc:
( )
( )
''
'' '' ''
. . . 1 . .
. .
. 1
ro z v z v
o
vz vz vz z
ro z z
o
m c m c
m c a b T
+ +
= = +
+ +
Ta c:
( )
( )
'' '
''
. . 1 .
. 1
ro v z z v
o
vz
ro z z
o
a a
a
+ +
=
+ +
=
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i hc SPKT Vinh Khoa: C Kh ng Lc
( )
( )
0.06991, 0381.21, 71197. 0, 9930 1 0, 9930 .19, 930
1, 038121, 70070
0,06991, 0381. 0, 9930 1 0.99301,0381
+ + = =
+ +
( )
( )
'' '
''
. . 1 .2 2
. 1
v vro z z
o
vz
ro z z
o
b b
b
+ +
=
+ +
=
( )
( )
0,06991, 0381.0, 0314. 0, 9930 1 0, 9930 .0, 00216
1,03810,00313
0,06991, 0381. 0, 9930 1 0, 9930
1,0381
+ + = = + +
'' 21, 70070 0,00313.vz z
mc T = + .
Thay vo phng trnh ( * ) ta c:
( )
( )' '' ''.1
( ). . . .
1
z H Hv c z vz vz z z
r
Q Qmc T a b T T
M
+ = +
+( )
( )0, 85. 44000 0
20,5712.707,2 1,0353. 21,70070 0,003130,5516.(1 0,699) z z
T T
+ = =+
20,00324 22,468 83876.71z z
T T + =
( )1
2
2689,1 /
4807, 26( i)( )z
z
T t m
T loa m
=
=
Vy nhit ti im z Tz = 2689.1
6. p sut ti im z pz:
Ta c h s tng p:
. 3,937z
z
c
T
T = =
p sut ti im z pz c xc nh theo cng thc:
pz = .pc = 3,937 . 1,1147 = 4,389 (MPa)1.2.4. Tnh ton qu trnh gin n:
n : Mn hc CT SVTH: V nh Cng8
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i hc SPKT Vinh Khoa: C Kh ng Lc
1. H s gin n sm :.
.
z z
c
T
T
=
i vi ng c xng: = 1
2. H s gin n sau :
Ta c h s gin n sau c xc nh theo cng thc: =
Vi ng c xng : = = 6,5
3. Ch s gin n a bin trung bnh n2 :
Ta c ch s gin n a bin trung bnh n2 c xc nh t phng trnh cn
bng sau:
( )( ) ( )
( )2 *
''''
1
8,3141
. .. 1 . . 2
b z H vzvz z b
r z b
nQ ba T T
M T T
= + + +
+
Trong :
Tb l nhit tr ti im b v c xc nh theo cng thc :
2 21 1
2689,1
6,5z
b n n
TT
= = ( oK )
QH* : Nhit tr tnh ton
i vi ng c xng:QH* = QH - QH= 4400 0 = 4400
( kJ/kg. )
Thay vo phng trnh;
( )
( )2
2
2
1
1
8,314
1 0,856 0,85 .44000 2689,121, 70070 0, 00313. 2689,1
2689,1 6, 50,5516. 1 0,0699 .1, 0356. 2659,1
6,5
n
n
n
= + + + +
Chn n2 = 1.23 thay vo hai v ca phng trnh trn ta c phng trnh
tng ng:
0,223 = 0,2303
4. Nhit cui qu trnh gin n Tb :
Ta c cng thc xc nh nhit cui qu trnh gin n Tb :
n : Mn hc CT SVTH: V nh Cng9
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i hc SPKT Vinh Khoa: C Kh ng Lc
2 1 1.23
2689,10.439
6,5z
b n
TT
= = = ( oK )
5. p sut cui qu trnh gin n pb :
p sut cui qu trnh gin n pb c xc nh theo cng thc :
2 1,234,389 0,4396,5
zb n
pp
= = = ( MPa )
6. Tnh nhit kh thi Trt :
Tnh nhit kh thi c xc nh theo cng thc:
1 1.45 1
1.450.105. 1748. 1121.56
0.4390
m
mr
rt b
b
pT T
p
= = =
( oK )
Sai s ca nhit kh thi tnh ton Trt v nhit kh thi chn
ban u Tr= 1000 khng vt qu 15%, ngha l :
1121,56 1000.100% .100% 0,108% 15%
1121,56rt r
rt
rt
T TT
T
= = =
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