How is capacity control achieved in centrifugal compressors?

Centrifugal compressors manage flow and capacity primarily through the use of guide vanes. Guide vanes adjust the airflow entering the compressor by changing the angle at which the air strikes the impeller. This angle adjustment allows for varying the amount of air entering the compressor, enhancing or reducing the capacity as needed based on the system’s operational requirements. By modulating the airflow through these guide vanes, the compressor can efficiently manage its performance under varying load conditions, ensuring optimal efficiency and operational stability.

In contrast, variable frequency drives typically control the speed of electric motors in compressors rather than directly affecting how the compressor itself modulates capacity. Throttle valves are generally used in systems to maintain pressure rather than to adjust the capacity of the compressor directly. Bypass lines are often employed for managing excess flow or pressure but are not the primary method for controlling the capacity of centrifugal compressors. Thus, the use of guide vanes stands out as the most effective method for capacity control in this context.