三峡水电站水轮机蜗壳结构形式选择

目前国内外大型水轮机蜗壳结构主要有垫层蜗悫，充水加压蜗壳和安全联合承载蜗壳第三种形式。三峡水电站单机容量７００ＭＷ，蜗壳进口直径达１２．４ｍＨＤ值１７００ｍ＾２；机组台数多，且较长时间在低水头下运行，结合国外的经验，宜采用充水加压蜗壳，以确保机组安全运用。至于充水另压蜗壳可能存在的一些缺陷，经采取一些技术措施后也是可以解决的。

Structural Type of Spiral Case

There are now primarily three types of the spiral case structure for large turbines at home and abroad,such as spiral case with cushion coat,spiral case with loading by water filling and complete bearing spiral case.For the Three Gorges Project,the unit has a capacity of 700 MW,with a ratio of HD of 1 700 m2 and a spiral case diameter of 12.4m.The Three Gorges Hydropower Station will have so many units operating under lower water head conditions for long time.In light of the foreign experience,it is reasonable to use the spiral case with loading by water filling so as to ensure the safe operation.As for the faults that may exist in the spiral case can be eliminated by technical measures.