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?