| 摘要 |
PURPOSE:To keep off any drop in propulsive capacity, by installing plural flaps in a rear end of a nozzle in a row over the whole circumference of the nozzle, while making a discharge port of the nozzle expandable or chokeable. CONSTITUTION:A nozzle 2 is formed in a polygonal square cylindrical form in its sectional form, while an inner circumferential surface of the nozzle 2 expands in almost parallel with a propeller shaft 11 and is made up in such a form as being somewhat extended wide at its front end. On the other hand, flaps 3 expanding rearward are rotatably installed in a rear end of a nozzle element 21, and when each of these flaps 3 is turned round, a discharge port of the nozzle 2 is so designed as to be expanded or choked. In the case where a flow of water is separated from a front end outer circumferential part of the nozzle 2 and thereby a cavitation occurs, if each flap 3 is operated outward and the discharge port is expended wide, the cavitation is prevented from occuring, thus any drop in propulsive capacity can be kept back.
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