What happens to pressure in a three-stage centrifugal compressor?

In a three-stage centrifugal compressor, pressure increases with each stage of compression. The design of centrifugal compressors involves multiple impellers or stages that work together to elevate the pressure of the gas as it moves through the unit. Each stage consists of an impeller that accelerates the gas, followed by a diffuser that converts kinetic energy into static pressure.

As the gas passes through each stage, its velocity increases due to the work done by the impeller, and the diffuser aids in converting this increased kinetic energy into a higher pressure. The cumulative effect of passing through three stages results in a significant increase in pressure from the inlet to the outlet of the compressor. This arrangement allows the three-stage compressor to effectively achieve higher pressures that are necessary for many applications, such as in gas transmission or industrial processes.

The other options misrepresent the function of the compressor; pressure does not remain constant or decrease with each stage, nor does it vary randomly. Instead, it is a systematic increase in pressure that characterizes the operation of a multi-stage centrifugal compressor.