| 摘要 |
PROBLEM TO BE SOLVED: To prevent leakage of a discharge current to the side of an impeller by providing a shroud on an outer periphery of the impeller, making lenth of an impeller liner larger than the same as length of the shroud and forming a circumferential groove on an outer peripheral surface of the shroud. SOLUTION: A shroud 17 is installed on an inner periphery of an impeller 6. An inner surface of the shroud 17 makes an arc shape continued to an inner surface 16a of an intake wall, and it is continued to an inner surface of a diffuser 8. An outer peripheral surface of the shroud 17 and an inner periphery of an impeller liner 16 face against each other with an extremely small clearance o. Length (a) of the impeller liner 16 is made the same as length (b) of the shroud 17 or larger than it. Additionally, some of circumferential grooves are formed in the vertical direction on a surface of an outer periphery of the shroud 17. Consequently, it becomes hard to leak water discharged in a direction of the diffuser 8 to the inlet side (intake side) of the impeller 6 through the clearance. Additionally, as high pressure on the outlet side of the impeller 6 is gradually decompressed by the circumferential grooves, flowing water leaking to the inlet side of the impeller 6 is further reduced.
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