Variation between Alpha 3 to Alpha 4 in Radial/ Mixed flow Diffuser

[kflee0]

Dear members,

I have some question about the alpha variation. For standard good design, is the variation from alpha3 to alpha4(90degree) going to be
linear variation or polynomial?. If either method can be used, how does each method affect the pump curve chracteristic? i am so interested to know about this, if someone has any reference book/material about this, please let me know.

Thanks
kflee0