Centrifugal Impeller and blade shapes

[Yam]

According to my lecture notes, for centrifugal impellers

Backward curved blades have a outlet blade angle of less than 90,
radial blades have curved blades have a outlet blade angle of 90,
Forward curved blades have a outlet blade angle of more than 90.

As such i have 2 questions

1) does the inlet blade angle have any relationship with outlet blade angles?
Example, for a radial blade, inlet blade angle = outletblade angle = 90 degrees?

2) What does it mean that the inlet velocity triangle remains the same for radial and forward vanes?
How can they be the same when there is a centrifugal impeller adding angular momentum into the fluid?

 

[Baluncore]

1. The blade must curve without sharp changes in flow direction. That relates the inlet to outlet angle.
2. The inlet velocity triangle is ahead of the impeller so is unaffected by momentum to be added later.