大型水电站蜗壳埋设方式对厂房振动的影响分析

Analysis on powerhouse vibrations with spiral cases in different embedding manners for large-scale hydropower station

如何选取水轮机蜗壳的埋设方式,是我国大型水电站厂房设计和研究的重点和难点之一。本文以三峡水电站厂房为背景,采用双结点接触非线性模型,计算三种不同蜗壳埋设方式下厂房结构的振动响应。计算结果表明:对于混凝土结构而言,保压方案的振动响应最小,垫层方案明显大于充水保压方案,直埋方案的振动响应最大;对于蜗壳等金属构件而言,保压方案的振动响应最大,而直埋方案最小,这说明直埋方案对金属构件的振动有利。为了检验计算模型与计算结果,开展了145m水位下三种不同埋设方式蜗壳的厂房振动现场测试。测试结果表明,对于混凝土结构而言,直埋方案的振动响应最大,保压方案最小,垫层方案略大于充水保压方案;而对于水轮机顶盖的振动而言,直埋方案振动最小,保压方案最大,垫层方案略小于充水保压方案。这说明测试结果与计算结果的振动响应规律基本一致。测试结果中垫层方案与保压方案基本一致的主要原因在于,在低水位下实际厂房的混凝土结构与垫层以及蜗壳之间存在缝隙,导致蜗壳的部分振动传递不到混凝土。

How to select the embedded manner of turbine spiral case is important but difficult to the design and development of powerhouse of the large-scale hydropower stations in west China. In combination with the Three Gorges powerhouse design, the paper adopts a nonlinear model of double-nodes contact element to simulate the vibration responses of powerhouse with spiral ease embedded in different manners, focusing on three structures, i.e. interface among concrete, cushion layer and spiral case. The results are summarized as follow. 1 ） In terms of concrete structure vibrations, the minimum responses＂ occurs in the spiral case embedded in concrete holding a certain water head inside （MHWH） , while the maximum responses in the manner of direct embedding in concrete （MD）. The responses in the spiral case embedded in concrete with cushion layer （MCL） are obviously greater than that of MHWH. 2） In terms of vibrations in spiral case and other metal components, the responses of MHWH, MCL and MD are in a decreasing order and MD is the most favorable to the metal components. To verify the model and the results, an in-situ test of powerhouse vibrations was conducted for the Three Gorges station under the water level of 145m, and it shows results quite similar to the model predictions. The only difference is that the responses of MCL in the test is close to that of MHWH. An explanation for this is that in the test case of MCL, there existed gaps between the spiral case and the concrete or cushion layer, which damped the transmission of vibration from spiral to its surrounding concrete.