| 摘要 |
Provided is a quiet propeller (1) including a propeller blade having such a pitch angle not at its root portion but at its blade end edge portion with respect to a relative flow in the rotational direction, as to raise the internal pressure of a liquid thereby to eliminate a cavity, a water bubble or a cavitation at the blade root portion at the time of a high-speed rotation so that the propeller is rotated at a high speed by a small prime mover and by a prime mover capable of moving much fluid backward. In the quiet propeller (1), a propeller blade (3) is curved backward at its leading end portion to form a slope portion 3(d), and a rotational front side end portion (3a) in the slope portion (3d) is formed into an arcuate shape in the side view whereas a rotational rear side end portion (3b) is so gradually extended backward from the rotational front side end portion (3a) as to become straight from the blade root to the blade end, thereby to form a deflecting slope face (3e). At the rotating time, the fluid is pushed toward the back axis from the deflecting slope face (3e) in the slope portion.
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