| 摘要 |
PROBLEM TO BE SOLVED: To miniaturize a pump while controlling the creation of an unstable part of a pump head curve from separation and stall in a low flow quantity area without an increase in rotation speed of an impeller. SOLUTION: Plural shallow grooves 124 in a fluid pressure gradient direction are formed on an inner surface of a casing 121 opposing to the impeller 1 in a circumference direction. Pressurized fluid is made flow backward in the grooves 124 toward an upstream side and spout out to a part where re- circulation flow occurs under a low flow quantity condition by a blade 122. Outlet angles of the impeller blade 122 are set in a range between 30 and 90 degrees. Preferably, a pre-guide vane 11 set to direct absolute flow at an impeller outlet to a pump axial direction in a designed flow quantity is provided.
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