Abstract: The influences of angle of flare, section figure and centerline of strike of discharge passage of a large pump on its hydraulic loss are studied. The concept of equivalent angle of flare is advanced. For the purpose of minimizing discharge passage total hydraulic loss, which includes frictional hydraulic loss, diffuse hydraulic loss and exit hydraulic loss, the angle of flare and section figure of the passage are optimized, the optimizing principles of the passage centerline of strike are put forward. The research results indicate that the passage has the optimum angle of flare which makes its hydraulic loss the least for certain positions of inlet section and exit section. Tests prove that the actual angle of flare from which separation fluids just occur is smaller than the optimum angle of flare obtained by theoretical calculation because of the influences of discharge curved pipe. The gradual changing optimum angle of flare could make the hydraulic loss even smaller than the constant optimum angle of flare. The optimum passage section figure of rectangle is square, and the rectangle has 4 optimum corner circular arcs which make the hydraulic loss of friction loss of per unit length passage the least. The results are significant for decreasing hydraulic loss of discharge passage, pump assembly optimum design and increasing pump assembly efficiency.

Key words: Discharge passage, Hydraulic losses, Large pump, Optimum design