🔍 Key Concepts

• Axial compressor blade tip clearance and why small clearances improve efficiency • Effect of centrifugal force and thermal expansion on rotor blades as speed and temperature increase • Difference between a design feature and a malfunction/abnormal condition

💭 Think About

• Ask yourself what happens to the rotor, casing, and blades of a large gas turbine compressor as it accelerates from low RPM to full RPM in terms of growth and movement. • Which answer choices describe something that would be intentionally built into the compressor for normal operation, rather than to fix or tolerate a fault? • How could allowing blades to move slightly in their root or attachment help keep the gap between blade tips and casing where the designer wants it?

✅ Before You Answer

• Eliminate any options that imply malfunction or damage as the primary reason for the design feature. • Consider which option is most clearly about maintaining compressor efficiency and proper internal clearances during all operating speeds. • Verify that the chosen choice matches what you know about how centrifugal force pushes blades outward and why designers care about the gap between blade tips and casing.