Which statement describes a disadvantage of a centrifugal-flow compressor related to stage counts?

Which statement describes a disadvantage of a centrifugal-flow compressor related to stage counts?

• A. Poor efficiency at low speeds
• B. High maintenance cost due to seals
• C. More than two stages are not practical because of losses in turns between stages
• D. Noise levels are excessive

Answer: (C)

In a centrifugal-flow compressor, air moves outward through an impeller and is then slowed in a diffuser to convert velocity into pressure. To add another stage, the flow must be redirected back toward another impeller, which requires a turn between stages. This interstage turning introduces significant losses—friction, flow separation, and nonideal diffusion—that accumulate with each additional stage. Because these turn losses grow quickly, stacking more than two stages becomes impractical from an efficiency and packaging standpoint. Therefore, the statement that more than two stages are not practical because of losses in turns between stages best captures the disadvantage related to stage counts. Other issues like low-speed efficiency, seal maintenance, or noise are not specifically about the limitation on the number of stages.

In a centrifugal-flow compressor, air moves outward through an impeller and is then slowed in a diffuser to convert velocity into pressure. To add another stage, the flow must be redirected back toward another impeller, which requires a turn between stages. This interstage turning introduces significant losses—friction, flow separation, and nonideal diffusion—that accumulate with each additional stage. Because these turn losses grow quickly, stacking more than two stages becomes impractical from an efficiency and packaging standpoint. Therefore, the statement that more than two stages are not practical because of losses in turns between stages best captures the disadvantage related to stage counts. Other issues like low-speed efficiency, seal maintenance, or noise are not specifically about the limitation on the number of stages.