What is the primary factor that controls the pressure ratio of an axial-flow compressor?

What is the primary factor that controls the pressure ratio of an axial-flow compressor?

• A. Inlet air temperature
• B. Blade speed
• C. Air density
• D. Number of stages in the compressor

Answer: (D)

The overall pressure rise in an axial-flow compressor comes from stacking multiple compression stages in series. Each stage adds a certain amount of pressure, so the total pressure ratio is essentially the product of the pressure rises of all the stages. Therefore, the more stages you have, the higher the potential overall pressure ratio, assuming the per-stage performance stays similar and you stay within design limits. Blade speed, rotor and stator geometry, and inlet conditions all influence how much pressure each stage can generate, but they don’t set the maximum pressure ratio by themselves—the stage count sets the multiplying effect. Inlet temperature and air density affect the actual operating point and efficiency, but the primary factor determining the achievable pressure ratio is how many stages are stacked in the compressor.

The overall pressure rise in an axial-flow compressor comes from stacking multiple compression stages in series. Each stage adds a certain amount of pressure, so the total pressure ratio is essentially the product of the pressure rises of all the stages. Therefore, the more stages you have, the higher the potential overall pressure ratio, assuming the per-stage performance stays similar and you stay within design limits.

Blade speed, rotor and stator geometry, and inlet conditions all influence how much pressure each stage can generate, but they don’t set the maximum pressure ratio by themselves—the stage count sets the multiplying effect. Inlet temperature and air density affect the actual operating point and efficiency, but the primary factor determining the achievable pressure ratio is how many stages are stacked in the compressor.