How to simulate the whole stage
 

I want to simulate the whole stage(rotor+diffuser+volute),but I cannot find any references.And I hve no idea about it.
Can anyone give me some references about.

Both rows (Impeller and Diffuser) can be meshed with AutoGrid5. Secondly you need to manually mesh your volute in IGG. Finally you open your AutoGrid5 project (Impeller and Diffuser) again and import the volute by using a "3D Effect". As a last step you define the FNMB-connection between diffuser and volute.