| 摘要 |
PROBLEM TO BE SOLVED: To prevent generation of surging in partial flow quantity region, and increase a head by providing a fluid circulating hole for leading reverse flow component of a fluid generated at an impeller inlet to a spurn blade. SOLUTION: A fluid circulating hole 81 is formed on a shroud end part 80 for defining an impeller inlet 8a. Reverse flow which is generated at the impeller inlet 8a and having turning component of the same direction as a rotational direction of the impeller 8, flows into a fluid circulating hole 81 without flowing to a blade 9 again. The fluid circulating hole 81 is inclined so as to keep an opening 81b of a spurn blade side 12 away from a main shaft 10 more than an opening 81a of the impeller inlet 8a side, and a recessed part communicated with the fluid circulating hole 81 is formed on an inner circumferential surface of the shroud end part 80. Accordingly, reverse flow generated at the impeller inlet 8a flows into the fluid circulating hole 81, and is led to the spurn blade 12, and it collides with the spurn blade 12. It is thus possible to eliminate turning component from reverse flow.
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