The Research On Numerical Simulation About Spiral Case Of Cushion Layer In Hydroelectric Power Station

Spiral case, a concernful diversion-component of reaction turbine, is commonly given significant consideration on hydroelectric power station design for structurally vital reasons. Meanwhile, the far-ranging application of spiral case of cushion layer is the requirement of development in Chinese hydroelectric power station construction. Since the complex configuration of spiral case of cushion layer and its non-liner properties on working, it is generally difficult to control the transfer ratio of internal water pressure. With the increase of working head, unit capacity and dimensions of structures, the safety of structures requires optimum design on spiral case of cushion layer with perplexing load, which directly leads to advanced analysis on such important component. The FEA modeling of spiral case of cushion layer, along with the selection of its materials and the entire simulation process, are still an issue without reasonable solution.The studies, focusing systematically on material of cushion layer, revealed that deformation of cushion layer would be related to the changes of parameters concerning both cushion layer and structures, and the non-liner properties of materials was considered on this analysis, as well as the contact effect between concrete and steel plate. The conclusions are as follows:1. With the plane axisymmetric FEM model of the actual structures in La-xi- wa hydroelectric power station plant, it is clarified that cushion layer's Elastic modulus ,Poisson Ratio and its width would affect the ratio of internal-press bearing by steel plate and outside-concrete regularly. Also the optimization of these parameters and their valid references were stated.2. The stress study of spiral case of cushion layer in different cushion layer range, in result, took into account the deformation regularity and stress in crucial part of spiral case and outside-concrete with various cushion layer sphere. By investigating the stress distribution of cushion layer under different load style, the directions for design were formulated.3. The non-linear properties of cushion layer material would post regular influence on spiral case, which has been tested via analysis with spring-gap element in this paper. Another influence, that coefficient of friction impose on stress locating on spiral case, was also discussed with the regards of the effect of contact ,slide and friction on cushion layer—steel—concrete. Furthermore, the comparison between contact model and common model, which was used to research the stress and deformation of steel plate and outside-concrete, gave strong proof of validity and feasibility of the contact model.To sum up, the comparison and analysis of force-transfer spiral case of cushion layer under static status would benefit the design of spiral case for its fine theory and cozy results.