turbomachinery basics
TRANSCRIPT
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JongSik Ohojsturboojsturbo@@koreakorea.com.com
Turbomachinery BasicsCentrifugal Compressors
TURBOMACHINERY BASICSCENTRIFUGAL COMPRESSOR
JAN. 28, 2004
JONGSIK OH
JongSik Ohojsturboojsturbo@@koreakorea.com.com
Turbomachinery BasicsCentrifugal Compressors
WHAT ARE TURBOMACHINES ?
Rotating dynamic machines with energy transferdue to changes of angular momentum
Torque on fluid = Rate of change ofangular momentum
Angular momentum = Moment of momentum= Tangential force x Distance= Momentum flow x Distance= rCm θ&
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Turbomachinery BasicsCentrifugal Compressors
EULER EQUATION
)CUC(Um TP Power
)rCrC(mT Torque
1122
1122
θθ
θθ
−=ω=
−=
&
&
2W
2C ω= 22 rU
ω= 11 rU
2Cθ
1Cθ
1mC
2mC
1C1W
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Turbomachinery BasicsCentrifugal Compressors
RELAVANT UNIT
WsJ
kgJ
skg
sm
skgP Power
sm
kg
msmkg
kgm.N
kgJK
kg.KJ
gas) ideal(for TCh Enthalpy (Specific)
Watt:Unit )CUC(Um
TP PowerN.m :Unit
)rCrC(mT Torque
2
22
P
1122
1122
===
=
====×
=
−=ω=
−=
θθ
θθ
&
&
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Turbomachinery BasicsCentrifugal Compressors
PREWHIRL OR PREROTATION
ω= 11 rU1Cθ
1C
1W
0C ,CC 11m1 == θ
1mC
1α
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Turbomachinery BasicsCentrifugal Compressors
PART-LOAD CONTROL
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Turbomachinery BasicsCentrifugal Compressors
SLIP FACTOR2W
ω= 22 rU
2mC
1W
ω= 11 rU
1r
2r
2Cθ
b2W
b2Cθ
b2β
2β
2α b2α
2Cb
2b
2
CC
θ
θ≡ζ
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Turbomachinery BasicsCentrifugal Compressors
IMPELLER EXIT BLADE ANGLE
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Turbomachinery BasicsCentrifugal Compressors
EFFICIENCY
efficiency polytropic the is where gases idealfor
1pp
1pp
gases idealfor 1
TT
1pp
gases idealfor TTTT
hhhh
Work alRe WorkIsentropic Efficiency Isentropic
P1
1
2
1
1
2
1
2
1
1
2
12
12'
12
12'
C
p
η
−
−
=
−
−
=
−−
=
−−
=
≡η
γη−γ
γ−γ
γ−γ
Independent of overall pressure ratios
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Turbomachinery BasicsCentrifugal Compressors
ROTHALPY & TOTAL ENTHALPY
0hh const. enthalpy Total (a)
Region Vane Stationary
1OO2 =−=
const.
U21W
21h
U21hI
const. Rothalpy (b)CUCUhh
)C21h(h const. enthalpy Total (a)
Region Blade Rotating
sstreamlinealong machinesAdiabatic
22
2relO,
11221OO2
2O
=
−+=
−≡
=
−=−
+≡≠
θθ
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Turbomachinery BasicsCentrifugal Compressors
ENERGY TRANSFER
0
1
2
3
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Turbomachinery BasicsCentrifugal Compressors
SPECIFIC SPEED
Machine Operation Parameter
• Operation speed at which machine producesa unit head rise per unit flow rate
• Independent of machine SIZESIZE
U.S.)(for ft : H /s,ft : Q rpm, : N where
HNQ
DNgH
NDQ
N
3
4/3
2/1
4/3
22
2/1
3
S =
≡
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Turbomachinery BasicsCentrifugal Compressors
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Turbomachinery BasicsCentrifugal Compressors
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Turbomachinery BasicsCentrifugal Compressors
(Balje) m : H /s,m : Q rad/s, : N where)gH(
NQN
3
4/3
2/1
S =
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Turbomachinery BasicsCentrifugal Compressors
VANED DIFFUSER
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Turbomachinery BasicsCentrifugal Compressors
VANED DIFFUSER
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Turbomachinery BasicsCentrifugal Compressors
LSD (Low Solidity Diffuser)
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Turbomachinery BasicsCentrifugal Compressors
AXIAL VANED DIFFUSER
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Turbomachinery BasicsCentrifugal Compressors
VOLUTE/SCROLL
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Turbomachinery BasicsCentrifugal Compressors
PERFORMANCE MAP
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Turbomachinery BasicsCentrifugal Compressors
PERFORMANCE MAP
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Turbomachinery BasicsCentrifugal Compressors
CORRECTED CONDITIONS
p(Pa) T(K), (kg/s),m N(rpm), where
101325p
15.288Tm
m
15.288TNN
1O
1O
CORRECTED
1OCORRECTED
&
&& ≡
≡
288.15N
TN
101325288.15m
pTm
0TN ,
pTm
,TT ,
ppf
0RTND ,
pDRTm
,TT ,
ppf
0)RT ,p ,m N, f(D,
AnalysislDimensiona
CORRECTED
O1
CORRECTED
1O
O1
O11O
O1
O1
O2
1O
2O
O11O2
O1
O1
O2
1O
2O
OO
=
=
=
=
=
&&
&
&
&
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Turbomachinery BasicsCentrifugal Compressors
IMPELLER INCIDENCEchokesurge
• Note : Angles measured from meridional referencefor axial-flow cascade tests
• Note : When angles from tangential reference,negative incidence in choke
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Turbomachinery BasicsCentrifugal Compressors
DIFFUSER INCIDENCE
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Turbomachinery BasicsCentrifugal Compressors
SPLITTER BLADES
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Turbomachinery BasicsCentrifugal Compressors
SPLITTER BLADES
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Turbomachinery BasicsCentrifugal Compressors
IMPELLER BLADE GEOMETRY
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Turbomachinery BasicsCentrifugal Compressors
SOME ANGLES
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Turbomachinery BasicsCentrifugal Compressors
IMPELLER CFD