What are the two elements that primarily contribute to the functionality of a centrifugal compressor?

The correct choice highlights the two key components of a centrifugal compressor: the impeller and the diffuser.

The impeller is crucial because it is responsible for converting the mechanical energy from the engine into kinetic energy, effectively increasing the velocity of the air passing through it. As the air moves through the impeller, it experiences an increase in pressure due to the centrifugal forces generated by the spinning blades.

Following this process, the diffuser plays its critical role by transforming that kinetic energy into static pressure. As the high-velocity air exits the impeller, the diffuser slows it down, which results in a rise in pressure. This combination of the impeller's capability to accelerate the air and the diffuser's function to convert that speed into pressure is fundamental for the effective operation of a centrifugal compressor, making the selection of these two components as the primary contributors entirely accurate.

In contrast, while components like the turbine and rotor may be relevant in other contexts such as turbine operation, they do not hold the same direct significance in the functionality of a centrifugal compressor specifically.