What condition in the compressor inlet can lead to compressor stall?

What condition in the compressor inlet can lead to compressor stall?

• A. Too much fuel reduces stall risk.
• B. The exhaust too cold cause stall.
• C. Excessive lubrication causes stall.
• D. Distortion and uneven flow at the inlet to the compressor leads to stall and high temperatures.

Answer: (D)

The key idea is that the air entering the compressor must be uniform in velocity and pressure to let every blade row contribute a smooth, progressive pressure rise. Distortion or uneven flow at the inlet disrupts that uniformity, causing some passages to see more flow and others less. This can trigger local blade stall and, if the disturbance is severe, lead to surge where the flow becomes unsteady or reverses. The disrupted flow also makes the compressor work harder, increasing losses and heating the gas, so temperatures rise in the process. Fuel quantity, cold exhaust, or excessive lubrication don’t create this inlet-flow mismatch in the same way, so they’re not the correct mechanism here.

The key idea is that the air entering the compressor must be uniform in velocity and pressure to let every blade row contribute a smooth, progressive pressure rise. Distortion or uneven flow at the inlet disrupts that uniformity, causing some passages to see more flow and others less. This can trigger local blade stall and, if the disturbance is severe, lead to surge where the flow becomes unsteady or reverses. The disrupted flow also makes the compressor work harder, increasing losses and heating the gas, so temperatures rise in the process. Fuel quantity, cold exhaust, or excessive lubrication don’t create this inlet-flow mismatch in the same way, so they’re not the correct mechanism here.