Dr. Ir. Harinaldi, M.EngMechanical Engineering Department
Faculty of Engineering University of Indonesia
AxiAl flow compressor and fans
Axial CompressorAxial Compressor
Axial FanAxial Fan
ConstructionConstruction
ConstructionConstruction
Velocity TriangleVelocity TriangleEuler Equation:
or:
Compressor StageCompressor Stage
0221
2212 xx WWhh
22 211
222 WhWh
21
22
21
22Constant WWWWC xxa
refref hh 0102
Compressor StageCompressor StageIsentropic Efficiency
0103
010301
0103
0103 1
input work actualinput work isentropic ideal
TTTTT
hhhh ssss
c
Pressure Ratio
1
01
01031
01
03
01
03 1
T
TTT
Tpp
css
Other Relation
p
a
CUCTT 21
0103tantan
Compressor StageCompressor StageWork Done Factor
capacity absorbing work idealcapacity absorbing work actualfactor doneWork
In practice Ca is not constant work done factor
p
a
CUCTT 21
0103tantan
Hence:
Reaction RatioReaction Ratio
13
12
stagein riseenthalpy staticrotorin riseenthalpy static
hhhhR
A measure of the static enthalpy rise that occurs in the rotor expressed as a percentage of the total static enthalpy rise across the stage
12010313
22
2112 2
xx CCUhhhhWWhh
h01rel = h02rel
C1 = C3
12
2121
12
22
221
2
12
22
21
2
22
xx
xxxx
xx
xaxa
xx
CCUWWWW
CCUWCWC
CCUWWR
Cx2 = U-Wx2
Cx1 = U-Wx1(Cx2-Cx1)=(Wx1-Wx2)
tantan2
tantan2
2121 UCU
CUWWR a
axx
2tantan1 12 R
Reaction RatioReaction Ratio
Stage LoadingStage Loading
Lift and Drag CoefficientLift and Drag Coefficient
Lift and Drag CoefficientLift and Drag Coefficient
ExampleExample
Solution:
Blade CascadeBlade CascadeCascade: a row of geometrically similar blades arrange at equal distanceIn axial compressor: High solidity Gas flow around a blade is affected by the flow around adjacent blade
Cascade wind tunnel and Cascade theory to obtain information on the effect of different blade designs on: air flow angles pressure losses expected energy transfer
Data from cascade testing to be corrected: annulus wall boundary layer at hub and tip interference of alternate blade row solidity decrease from hub to tip blade velocity varies from hub to tip
affecting blade inlet angle
Data from cascade testing applied only for one radius and inlet blade angle
NomenclatureNomenclature
Deflection and Pressure Loss CurvesDeflection and Pressure Loss Curves
Deflection and Pressure Loss CurvesDeflection and Pressure Loss Curves
Deflection and Pressure Loss CurvesDeflection and Pressure Loss Curves
Cascade Lift and Drag CoefficientCascade Lift and Drag Coefficient
12
3
21
0
coscos2
Cp
csCD
Drag Coefficient
Lift Coefficient
tantantancos2 21 DL C
csC
01010 ppp
2tantantan 21
Let:
Cascade Lift and Drag CoefficientCascade Lift and Drag Coefficient
Cascade Lift and Drag CoefficientCascade Lift and Drag Coefficient
Blade EfficiencyBlade Efficiency
Stage EfficiencyStage Efficiency
Three Dimensional FlowThree Dimensional Flow
0constant drdCC aa constrCrCdrdC xxx
Multistage PerformanceMultistage PerformanceCompression 1 5Single compression:
III
IIIscIIIs hh
hhhhmW
Staged compression: III
s
ss
sss
hhmW
hhhhhhhhmW
s
4534
2312
cs
4534
2312
IIIsss
ss
hhhhhhhhhh
However:
Multistage PerformanceMultistage Performance
Axial Flow Compressor CharacteristicsAxial Flow Compressor Characteristics