Abstract: Influence of each factor on blade inlet flow of a large vertical axial-flow pump is analyzed, formation mechanism of flow field in the cross section is studied. The idea is put forward that the blade cascade adversely effects the inlet flow and the flow adjusts automatically, that is to say, if inlet flow of cascade is not axial even flow, the characteristics of cascade will react on the flow and reach equilibrium with the flow. The results indicate that the flow field in blade inlet of large vertical ax-ial-flow pump is neither axial nor even, different from normal assumption. The flow field in blade inlet of pump with impeller diameter D=1.64 m is measured with five-hole probes, which field in inlet of blades on performances of pump, partial wear-ing of guide bearing and gap cavitation are analyzed and im-provement methods of the flow are put forward. Results mean much to improvement of design theories and methods on ax-ial-flow pump and its suction passage and increasement of op-eration performance.

Key words: Flow field in inlet of blades, Large vertical axial-flow pump, Operation performances, Reaction of blade cascade on inlet flow