Structural Analysis Of The Giant Spiral Case With Different Embedding Manners

With the development of the hydroelectric industry in our country, the unit capacity of the power station under construction and building is larger and larger. The HD values of the spiral case also the sharp play growth. The choice of embedding manners is one of the key problems that guarantee the safe stability of the hydro generator. To a giant hydraulic structure with very high HD value, the preloading filling spiral case structure is always used. Whether the other of manners could still be used is in dispute. Therefore, this paper is focused on the above questions. Based on Three Gorges Project, the following aspects about the three typical embedding manners are studied:(1) The border condition of cyclic symmetry is applied to the finite element models with contact among cushion layer, penstock and concrete. The effects of elastic modulus, thickness and placement extent of cushion layer on the stress of its around concrete are analyzed. It is suggested that the ratio of thickness to elastic modulus can be used as an important parameter in the design of cushion layer.(2) Comparing with the spiral case with cushion layer, inner-pressure-holding embedment and directly embedding spiral case, the stress and deformation of the spiral case structure are showed. They could be applied to the design of hydraulic structure.(3) The effect of the expansion and the anti-thrust ring on the stress and deformation of the spiral case structure are analyzed respectively. It is found that the presence of expansion reduces in large extent the stiffness of the spiral case as a supporting structure of the turbine. It affects the safe stability of the hydro generator. And it must be considered in design.(4) On the basis of finite element theory of reinforced concrete, the directly embedding spiral case structure is studied. On the condition of the pressure of inner water, the crack development, distribution and width, the stress and deformation of the penstock and rebar are analyzed respectively.In the paper, the stress distribution of the spiral case structure of three typical embedding manners is studied. It is expected that the valuable suggestions could provide the reference for solving the choice of the embedding manners in giant project.