Static And Dynamic Characteristics Analysis For Hydroelectric Spiral Case With Cushion Layer

In the 50s of 20th century, cushion spiral structure type was commonly used in the design of small and medium power stations, with requirements of accelerating the spiral case construction schedule, in recent years our country started to build hydropower station with cushion volute level in the unit capacity of 700MW. With the increasing spiral size and water pressure, many new issues and problems have been proposed, many new issues and problems have been proposed and need further study, such as cushion spiral case compared with other types of spiral case, cushion parameters in different stress state are unique, distribution between the components of the uneven spiral hydraulic thrust power cause by asymmetric shape of spiral case, the quantitative differences of the vibration and dynamic response, the reasonable selection of package scope and parameters of cushion layer, some important technical problem is not resolved such as the design method spiral case with cushion layer and the availability of cushion materials, the conclusions of spiral case cushion impact on the unit level and stable operation cause by have not been convinced. Finite element method, ANSYS software application platform was used in this paper, to solve the above problems, through the establishment of the finite element model of spiral case with cushion, the static and dynamic characteristics were calculated and analyzed, discussed the following aspects that achieved significant research results:(1) Established the three-dimensional finite element model of the spiral case with cushion layer, combed with axial symmetric theory and two-dimensional axial symmetric model in existing research, three different two-dimensional plane axial symmetric model were established in quantitative analysis of the steel liner and concrete stress and displacement, to provide reference for the simplified three-dimensional model in the future.(2) Using numerical simulation method with the calculation example of a practical project, the three-dimensional finite element model of cushion layer spiral case has been established, and a detailed study of cushion layer spiral case under the role of water pressure has been done, including the change of the cushion thickness, flat wrap angle, radial wrap angle and the elastic modulus on the impact of ring shear suffered, and influence of the ring shear in case of the failure of cushion layer was carried out,to explore and study from the ring shear properties in cushion layer spiral case, in order to be referred to the theoretical basis and optimization design.(3) To study the dynamic characteristics of the spiral case with cushion layer and the overall structure of the plant, the finite element model of intermediate units section and the edge units section were established. Based on the existing results, consider the impact of the boundary conditions, cushion layer parameters, especially the cushion layer thickness on the spiral itself, plant structure and the lower part of the overall structure of plants, carried out detailed calculations and analysis of spiral structure of the plant as a complement of the dynamic properties for cushion layer spiral case.