FAA Aviation Mechanic Powerplant (AMP)Turbine EnginesHard
A turbine engine's axial compressor has a measured inlet total pressure of 14.7 psi and a discharge total pressure of 220.5 psi. What is the compressor's overall pressure ratio?
- A15:1
- B10:1
- C12:1
- D18:1
Show answer & explanationAnswer & explanation
Correct answer: A. 15:1
Overall compressor pressure ratio equals discharge pressure divided by inlet pressure: 220.5 / 14.7 = 15. This means the compressor increases air pressure by a factor of 15 from inlet to discharge.
Why the other options are wrong
- B. 10:1 does not match the calculated value of 220.5/14.7.
- C. 12:1 is lower than the correct ratio.
- D. 18:1 overstates the actual compression ratio.
Compressor Pressure Ratio
The ratio of compressor discharge total pressure to compressor inlet total pressure, indicating how much the compressor increases air pressure.
- Ratio = discharge pressure ÷ inlet pressure
- Multistage axial compressors can achieve ratios of 15:1 or higher
- Higher pressure ratios generally improve thermal efficiency
Memory trick: 'Discharge over Inlet, that's the ticket' - divide to get the ratio