How does a centrifugal flow compressor compress air?

• A. Air enters the center of a spinning impeller and flung outward by centrifugal force into a diffuser, converting velocity to pressure
• B. Air flows axially through multiple stages to increase pressure
• C. It uses a radial-axial combining mechanism
• D. Air is compressed by a turbine expanding the gas

Answer: (C)

The basic mechanism is converting rotational energy into outward flow and then into pressure. As the impeller spins, air is drawn into the center and pushed outward along the blades by the spinning motion. This radial outward acceleration increases the air’s velocity and kinetic energy. Downstream, a diffuser slows the air down; because the flow is decelerated, the kinetic energy is transformed into an increase in static pressure, producing the compressed air. This radial outward path with a diffuser pressure-rise is the hallmark of a centrifugal compressor. In contrast, axial compressors move air along the shaft axis through multiple stages to build pressure. Some designs can blend radial and axial elements, but the essential idea remains: outward radial flow from the impeller and diffusion to raise pressure.