水电站厂房蜗壳进口边界条件对止推环作用的影响研究

Influence of inlet boundary conditions of spiral cases on the anti-thrust ring in hydropower station house

为了研究水电站厂房蜗壳进口边界条件对止推环作用的影响,采用ANSYS软件对某水电站地下厂房蜗壳结构进行三维有限元计算,研究了蜗壳进口不同边界条件和止推环对蜗壳结构受力特性的影响,提出了蜗壳进口边界条件的合理模拟方法。结果表明:设置伸缩节时,直埋蜗壳方案止推环只承担了不平衡水推力的5. 63%,低于垫层蜗壳方案时的29. 21%。而不设伸缩节时,考虑上游钢管和外包混凝土情况下,上游钢管承担的不平衡水推力相比不考虑上游钢管和外包混凝土的情况减小6%～19%。因此,无论上游钢管是否设置伸缩节,直埋蜗壳均不需设置止推环;对于垫层蜗壳,设置伸缩节时止推环可以起到较为明显的止推作用,但不设伸缩节时上游钢管或加劲环能够代替止推环的作用,可以考虑取消止推环。综合考虑蜗壳进口上游钢管对计算精度的影响、计算模型的复杂性以及计算工作量的增加程度,建议蜗壳计算模型中进口范围取至上游钢管中第一个加劲环,并施加轴向约束。

In order to study the influence of inlet boundary condition of spiral case on the function of anti-thrust ring,the three-dimensional finite element calculation of the spiral case structure of a certain underground hydropower station is carried out using ANSYS software.The influence of inlet boundary conditions and the anti-thrust ring on the mechanical characteristics of the spiral case structure is studied,and a reasonable simulation method for the inlet boundary conditions of the spiral case is proposed.The result shows that the anti-thrust ring of the spiral case with direct embedding scheme only bears 5.63%of the unbalanced hydraulic thrust when the expansion joint is set up,which is lower than 29.21%on the scheme of spiral case with cushion layer.However when the expansion joint is not set up,the unbalanced hydraulic thrust that the upstream penstock of spiral case bears considering the upstream penstock and the concrete outside spiral case is reduced by 6%~19%compared with without them.The anti-thrust ring is not necessary for the spiral case with direct embedding scheme whether the upstream penstock is provided with expansion joint.For the spiral case with cushion layer,the anti-thrust effect of the anti-thrust ring is obvious when the expansion joint is provided.Without the expansion joint,the upstream penstock or the stiffener ring can replace the effect of the anti-thrust ring,thus the anti-thrust ring could be removed.Considering the influence of the upstream penstock of spiral case on the calculation accuracy,the complexity of the calculation model and the increase in the calculation workload,the range of the inlet section of the spiral case calculation model is suggested to be taken to the first stiffening ring in the upstream penstock,where the axial restraint is applied.