Is it true that the first stage impeller of a centrifugal is always unshrouded while the other stages can have shrouded impellers? what is the reason for having an open first stage impeller?
The advantage of an open impeller is the reduction in stresses which helps increase the max tip speed. In other words, you could have a high head first stage.
To the others:
Are these open first stage impellers used mainly on high MW machines with high 1st stage flow coefficients?