Turbine Engine Construction, Components, and Operation
Domain 6 covers turbine engine flow path and components.
Flow path
- Air enters the inlet, is compressed by axial or centrifugal compressor stages, diffused, mixed with fuel in combustors, expanded through turbine stages, and exhausted.
- Stators convert velocity to pressure; rotors add energy; blade cooling uses compressor bleed air.
- Turbine types include turbojet, turbofan, turboprop, and turboshaft.
- Thrust is produced by momentum change; turboprops and turboshafts extract shaft power.
Ratings and limits
- N1 is fan/compressor speed; N2 is core speed; EPR compares exhaust pressure to inlet pressure.
- Turbine inlet temperature and exhaust gas temperature are limiting; exceedance reduces blade life.
- Compressor stall can result from distortion, bleed valve malfunction, or abrupt throttle movement.
Worked example
A turbojet takes 100 lb/s of air, exhaust velocity 1,800 ft/s, inlet velocity 500 ft/s. Thrust = m_dot × ΔV ÷ g = 100 × 1,300 ÷ 32.174 = 4,040 lbf. The reasoning divides by g because lb/s is mass flow in gravitational units; using 100 × 1,300 alone gives the wrong unit.
Traps
Confusing N1 and N2; treating EPR as a temperature limit; assuming all turbine engines produce thrust; ignoring cooling air when interpreting turbine damage; using sea-level thrust at altitude.