鱼尾型差动坎免空蚀性能探讨

A Study on Cavitation-free Characteristics of Fish-tail Type Differential Bucket

柘溪溢流坝原为矩形差动式鼻坎,1962年发生严重空蚀。后改建成梯形差动坎,并经多年试用多种材料防护,仍未能免除空蚀。1979年局部改型,分别采用控制挑角差或增设鱼尾坎后,经十年溢流,未再发生空蚀。前者可应用于新建工程,后者则适用于已建而发生空蚀的差动坎。本文着重探讨鱼尾型差动坎的免空蚀性能,并给出坝高与鱼尾坎的免空蚀临界侧挑角关系曲线。

A differential bucket has its advantage in energy dissipation, but recently its application is highly limited, since cavitation damage was found severe on rectangular differential bucket of Zhexi spillway in 1962. Based on systematic experimental investigation and long-term prototype test, it is found that a rectangular differential bucket can be made free from cavitation damage as long as the angle difference is limited, or the outlet of a denticle is widened slightly (shaped as fish-tail). The cavita-tion-free characteristics of fish-tail type differential bucket was studied and the relation curves among critical side-jetted angle free from cavitation, head drop, and unit width discharge are given in present paper. For a constructed and damaged differential bucket, the fish-tail type is appropriate for eliminating cavitation and easy for reconstruction.