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