Which statement about centrifugal flow compressor advantages is incorrect?

• A. Constant efficiency at all RPM speeds
• B. Cheaper than axial
• C. Not subject to flow disruptions such as surge and stall
• D. Requires highly specialized materials

Answer: (D)

The statement that centrifugal flow compressors require highly specialized materials is not an actual advantage. These compressors are valued for their simplicity, robustness, and cost efficiency, and they typically use standard materials and conventional manufacturing processes. Requiring highly specialized materials would raise cost, weight, and complexity, which runs counter to the practical benefits people look for in centrifugal designs. In practice, you get the favorable trade-offs from the impeller and diffuser design without needing exotic materials.

Some other points to keep in mind: efficiency does not stay constant at every RPM; performance curves show how efficiency varies with operating point. The idea that centrifugal compressors are always cheaper than axial ones is often true, especially at smaller sizes, but it’s not a universal rule in every scenario. And while centrifugal machines can be less prone to certain flow issues than axial compressors, they can still experience surge and stall under certain operating conditions, so that statement isn’t universally accurate either.