Abstract: Under the influence of guide blade discharge circulation, discharge bend pipe secondary flow, the flow in the 1-channel discharge passage of an axial flow pump is complicated spiral flow, the discharge in the left channel is bigger than that in the right one as for 2-channel passage, and the passage hydraulic losses are abnormal. The section current energy of the passage is measured and determined with 5-hole probes accurately. The hydraulic loss characteristics are determined and analyzed. The methods deducing the hydraulic losses are investigated. The results indicate that the passage hydraulic losses are not proportional to the flow discharge. Compared with circle pipe, the hydraulic losses of divergent discharge passage are smaller and the pump assembly efficiency is higher with 10%~30%. As for 1-channel passage , axial-flow pump outlet circulation is too big usually, the passage hydraulic losses are big too, but small circulation can slightly reduce hydraulic losses. As for 2-channel passage, discharges in 2 channels are not equal and the hydraulic losses increase. The outlet guide blade with small discharge circulation or without circulation could reduce discharge passage hydraulic losses and pump assembly efficiency increases with 6%~11%.

Key words: 5-hole probe, Axial-flow pump, Discharge passage Hydraulic losses