1 MAE 4261: AIR-BREATHING ENGINES Overview of Axial Compressors Mechanical and Aerospace Engineering Department Florida Institute of Technology D. R. Kirk

2 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

3 CENTRIFUGAL COMPRESSORS

4 ALLISON 250: AXIAL + RADIAL DEVICE

5 WHERE IN THE ENGINE? PW2000 Fan Compressor

6 2 SPOOL DEVICE: PW2000 High Pressure Compressor (  high ) Low Pressure Compressor (  low ) High and Low Pressure Turbines

7 SCHEMATIC REPRESENTATION Single Shaft Compressor Twin-Spool Turbofan

8 2 SPOOL DEVICE Low Pressure Spool Low Pressure Compressor High Pressure Compressor

9 FEATURES OF INTEREST: PW2000 Change in cross sectional flow area Disks (centrifugal stress) also called ‘Blisks’ Blades are twisted Intra-Blade Supports

10 EXTREME TWIST: GE7000

11 AXIAL COMPRESSOR: SCHEMATIC REPRESENTATION Centerline

12 SCHEMATIC REPRESENTATION

13 AXIAL COMPRESSOR EXPLODED VIEW

14 HOW BLADES ARE ATTACHED

15 REVIEW: PRESSURE DISTRIBUTION Rotor –Adds swirl to flow –Adds kinetic energy to flow with ½  v 2 –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)

16 AXIAL COMPRESSOR ENERGY EXCHANGE Rotor –Adds swirl to flow –Adds kinetic energy to flow with ½  v 2 –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) Centerline  NGV R SR

17 COMPRESSOR AND FAN DATA FOR VARIOUS ENGINES

18 EXAMPLES OF BLADE TWIST

19 COMPRESSOR MAP

20 BOUNDARY LAYER LOSSES AND SEPARATION

21 LOSSES AND CASCADE TESTING Measure of loss correlated to Blade geometry and Easily measured in cascade

22 SHOCK AND HIGH SPEED LOSSES

23 ENGINE TESTING: BIRD STRIKE

24 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