MAE 4261 AIRBREATHING ENGINES Overview of Axial Compressors

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

TWO PRIMARY TYPES OF COMPRESSORS • Axial Devices – High mass flow – High efficiency – Stackable (multi-staging) – More parts – More complex • Radial (Centrifugal) Devices – Can not handle as high mass flow – Less efficient than axial device – Short length – Robust – Less Parts 2

CENTRIFUGAL COMPRESSORS 3

ALLISON 250: AXIAL + RADIAL DEVICE 4

WHERE IN THE ENGINE? PW 2000 Fan Compressor 5

2 SPOOL DEVICE: PW 2000 Low Pressure Compressor (wlow) High Pressure Compressor (whigh) High and Low Pressure Turbines 6

SCHEMATIC REPRESENTATION Single Shaft Compressor Twin-Spool Turbofan 7

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

FEATURES OF INTEREST: PW 2000 Intra-Blade Supports Change in cross sectional flow area Disks (centrifugal stress) also called ‘Blisks’ Blades are twisted 9

EXTREME TWIST: GE 7000 10

AXIAL COMPRESSOR: SCHEMATIC REPRESENTATION Centerline 11

SCHEMATIC REPRESENTATION 12

AXIAL COMPRESSOR EXPLODED VIEW 13

HOW BLADES ARE ATTACHED 14

REVIEW: PRESSURE DISTRIBUTION • Rotor – Adds swirl to flow – Adds kinetic energy to flow with ½rv 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) 15

AXIAL COMPRESSOR ENERGY EXCHANGE w Centerline • NGV • R S R Rotor – Adds swirl to flow – Adds kinetic energy to flow with ½rv 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

COMPRESSOR AND FAN DATA FOR VARIOUS ENGINES 17

EXAMPLES OF BLADE TWIST 18

COMPRESSOR MAP 19

BOUNDARY LAYER LOSSES AND SEPARATION 20

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

SHOCK AND HIGH SPEED LOSSES 22

ENGINE TESTING: BIRD STRIKE http: //100. rolls-royce. com/facts/view. jsp? id=215 23

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 24