Abstract: In outlet of a large axial pump, there is optimal swirling flow which will make hydraulic losses of the singular-tube discharge passage lowest. The optimal swirling flow may be made by the outlet diffuser whose blade outlet angle B was designed especially. To make the hydraulic losses lowest, 2 physical models are advanced for hydraulic design of outlet diffuser of the pump and its discharge passage as a whole in the pumping stations constructed and to be constructed, The methods solving the models and designing the outlet diffuser are also put forward.

Key words: Axial outlet diffuser, Discharge passage, Hydraulic losses, Large pump, Swirling flow