In compressor map discussions, Technician A claims choke lines indicate efficiency drops, Technician B claims turbo speed lines represent constant speed. Which technician is correct?

In compressor map discussions, Technician A claims choke lines indicate efficiency drops, Technician B claims turbo speed lines represent constant speed. Which technician is correct?

• A. A only
• B. B only
• C. Both
• D. Neither

Answer: (C)

The map is showing how a compressor behaves across flow and pressure ratio, with lines for efficiency and for rotor speed. The choke boundary is the point where flow becomes sonic at the throat, so you hit a maximum possible mass flow for that speed. Beyond or along that boundary, you can’t push more flow by increasing pressure ratio, and the flow dynamics become dominated by compressible effects and losses. That tends to place the operating point in a less efficient region, so choke lines are associated with efficiency dropping as you push toward that limit. Lines of constant rotor speed on the map are exactly that: they show performance at a fixed speed. These speed lines help compare how the compressor behaves as you change flow and pressure ratio while the rotor speed stays the same. So the statement about turbo speed lines representing constant speed is correct as well. Both observations are describing legitimate features of compressor maps, so the answer is that both are correct.

The map is showing how a compressor behaves across flow and pressure ratio, with lines for efficiency and for rotor speed. The choke boundary is the point where flow becomes sonic at the throat, so you hit a maximum possible mass flow for that speed. Beyond or along that boundary, you can’t push more flow by increasing pressure ratio, and the flow dynamics become dominated by compressible effects and losses. That tends to place the operating point in a less efficient region, so choke lines are associated with efficiency dropping as you push toward that limit.

Lines of constant rotor speed on the map are exactly that: they show performance at a fixed speed. These speed lines help compare how the compressor behaves as you change flow and pressure ratio while the rotor speed stays the same. So the statement about turbo speed lines representing constant speed is correct as well.

Both observations are describing legitimate features of compressor maps, so the answer is that both are correct.