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MAE 4261: AIR-BREATHING ENGINES

Overview of Axial Compressors

Mechanical and Aerospace Engineering Department

Florida Institute of Technology

D. R. Kirk

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TWO PRIMARY TYPES OF COMPRESSORS

• Radial (Centrifugal) Devices– Can not handle as high mass flow– Less efficient than axial device– Short length– Robust– Less Parts

• Axial Devices– High mass flow– High efficiency– Stackable (multi-staging)– More parts– More complex

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CENTRIFUGAL COMPRESSORS

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ALLISON 250: AXIAL + RADIAL DEVICE

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WHERE IN THE ENGINE? PW2000

FanCompressor

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2 SPOOL DEVICE: PW2000

High Pressure Compressor (high)

Low Pressure Compressor (low)

High and Low Pressure Turbines

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SCHEMATIC REPRESENTATION

Single Shaft Compressor

Twin-Spool Turbofan

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2 SPOOL DEVICE

Low Pressure Spool

Low Pressure Compressor High Pressure Compressor

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FEATURES OF INTEREST: PW2000

Change in cross sectional flow area

Disks (centrifugal stress)also called ‘Blisks’

Blades are twisted

Intra-Blade Supports

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EXTREME TWIST: GE7000

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AXIAL COMPRESSOR: SCHEMATIC REPRESENTATION

Centerline

Centerline

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SCHEMATIC REPRESENTATION

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AXIAL COMPRESSOR EXPLODED VIEW

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HOW BLADES ARE ATTACHED

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REVIEW: PRESSURE DISTRIBUTION• Rotor

– Adds swirl to flow

– Adds kinetic energy to flow with ½v2

– Increases total energy carried in flow by increasing angular momentum

• Stator

– Removes swirl from flow

– Not a moving blade → cannot add any net energy to flow

– Converts kinetic energy associated with swirl to internal energy by raising static pressure of flow

– NGV adds no energy. Adds swirl in direction of rotor motion to lower Mach number of flow relative to rotor blades (improves aerodynamics)

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AXIAL COMPRESSOR ENERGY EXCHANGE• Rotor

– Adds swirl to flow

– Adds kinetic energy to flow with ½v2

– Increases total energy carried in flow by increasing angular momentum

• Stator

– Removes swirl from flow

– Not a moving blade → cannot add any net energy to flow

– Converts kinetic energy associated with swirl to internal energy by raising static pressure of flow

– NGV adds no energy. Adds swirl in direction of rotor motion to lower Mach number of flow relative to rotor blades (improves aerodynamics)

CenterlineN

GV R S R

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COMPRESSOR AND FAN DATA FOR VARIOUS ENGINES

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EXAMPLES OF BLADE TWIST

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COMPRESSOR MAP

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BOUNDARY LAYER LOSSES AND SEPARATION

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LOSSES AND CASCADE TESTING

Measure of loss correlated toBlade geometry andEasily measured in cascade

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SHOCK AND HIGH SPEED LOSSES

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ENGINE TESTING: BIRD STRIKE

http://100.rolls-royce.com/facts/view.jsp?id=215

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ADDITIONAL ISSUES AND BLADE TESTING

• Other Issues

– High Cycle Fatigue

– Materials

– Manufacturing

– Containment of Blade

– Disk Rupture

– Sealing

– Tip and Hub Losses

– Turbine Cooling Bleed

– Inspection

– Replacement Parts ($) ‘Blade-Out’ Simulation