Effect of speed on centrifugal compressor performance at a given pressure ratio: choose the correct trend. For a centrifugal compressor operating at a fixed pressure ratio, what is the typical effect of increasing rotational speed?

Concept/Approach
Raising speed generally shifts the characteristic to higher mass flow and head. At a fixed pressure ratio away from the new design point, the operating point tends to a higher flow with some off-design penalties, often reducing efficiency.

Result
Flow increases; efficiency typically drops when operating off optimum speed-line at the same pressure ratio.

Final Answer
Increase in flow and decrease in efficiency.