Patent ID: 7604458

Claim:
An axial flow pump comprising: a plurality of impeller blades and a plurality of guide vanes which are fixed to a shroud and set downstream of said impeller blades, wherein said plurality of guide vanes has plural kinds of guide vanes of which one kind of said guide vanes has a different shape from the other kind/kinds of said guide vanes, said plurality of guide vanes being regularly located in a circumferential direction of said shroud such that leading edges of said one kind of guide vanes are set further downstream than leading edges of the other kind/kinds of said guide vanes so as to reduce generation of separation vortexes due to variation in a flow rate, said plurality of guide vanes includes two kinds of guide vanes being a first kind of guide vanes and a second kind of guide vanes such that said second kind of guide vanes are shorter than said first kind of guide vanes with respect to a said direction of a pump rotation axis and leading edges of said second kind of guide vanes are set further downstream than leading edges of said first kind of guide vanes, and said second kind of guide vanes have a shorter length in a region close to said pump rotation axis than a length in a region farther from said pump rotation axis, said lengths being with respect to said direction of said pump rotation axis, and said second kind of guide vanes have a shorter length than said first kind of guide vanes in a region close to said pump rotation axis, said length being with respect to said direction of said pump rotation axis.