In a centrifugal flow compressor, which component accelerates the mass of airflow?

• A. Impeller
• B. Stator
• C. Diffuser
• D. Inlet

Answer: (A)

The key idea is that energy is added to the gas by the rotating impeller. As air moves through the impeller blades, the blades push on the air, imparting momentum and speeding it up—this is the acceleration of the flow and an increase in its kinetic energy (and total head). The impeller is the element that does the work, directly increasing the air’s velocity as it moves outward through the blade passages.

After the air leaves the impeller, the stator helps straighten the flow and remove swirl, while the diffuser slows the flow and converts that increased velocity into higher static pressure. The inlet merely guides the air into the compressor with little acceleration.