Before using boolean VS after using boolean !
 

Hey guys

I'm working on a centrifugal compressor for analysis in fluent
The compressor has 20 impellers and I'm modelling just 1/20 of whole model
So I'm modeling the air path and then use boolean to Subtract compressor from air
Before using the boolean the side surfaces of air model have equal area but when I'm trying boolean the number of the edges are the same but the surfaces area are difference!

How can I solve this problem?