| 摘要 |
Vanes (73) are provided on the outer peripheries of both surfaces of an impeller in a circumferential direction, and vane grooves (72) are provided between the vanes. The vane grooves are formed to be curvilinear as viewed from a radial cross section. Also, connections of the vane grooves (72) with end surfaces (74) of the vanes are formed to be curvilinear as viewed from a circumferential cross section, and portions which extend from a forward side of a direction of rotation toward the connections are formed to be curvilinear. Communication holes (76) are formed forwardly or rearwardly of the vane grooves in the direction of rotation to allow communication between the vane grooves on both surfaces. An opening of the vane grooves is formed into various shapes, for example, straight in a radial direction, curved in the direction of rotation, or inclined in the direction of rotation.
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