How do centrifugal compressors achieve higher discharge pressures?

Centrifugal compressors achieve higher discharge pressures primarily through the design of multiple impeller stages arranged on a common shaft. Each stage of the impeller increases the pressure of the refrigerant or gas by adding energy to it as it passes through. This multi-stage approach effectively compresses the gas in a series of steps, allowing for significant pressure increases.

When the gas enters the first stage, it gains energy from the impeller's rotation, which transforms kinetic energy into pressure energy. As the compressed gas exits one stage and enters the next, it experiences further compression. This process can be continued through multiple stages, essentially stacking the pressure increases to achieve the desired discharge pressure effectively.

Other mentioned methods, such as increasing motor speed, could contribute to achieving pressure, but they are not sufficient alone for significant pressure increases. Likewise, using a single impeller would limit the pressure capabilities compared to a multi-stage design, and smaller inlet valves do not inherently increase discharge pressure but could affect flow rates. Thus, having additional stages is the preferred method used in centrifugal compressors for obtaining higher discharge pressures.