The Structural Analyses Of Spiral Case Using Cushion Layer With High HD Value

The structure of spiral case is the important part of hydropower station. With the HD value of hydropower station hightening sharply,the design optimum and structure safety seem more important. To spiral case with high HD value,the preloading filling spiral case structure is always used.But the embedding manner using cushion layer also has distinct excellencies.Therefore this paper does some studies as below on spiral case using cushion layer based on finite element method ANSYS.(1)Take a sector embodied a fixed guide vane and then the border condition of cyclic symmetry is applied as well as contact among cushion layer, penstock and concrete. The analyses are carried out by two spiral case structures in hydropower station with different HD values. The effects of elastic modulus, thickness and placement extent of cushion layer on intensity and distortion of spiral case are studied. Some fundamental characteristics are realized for the optimizing analysis of spiral case structure using cushion layer in hydropower station, incidentally the best mode for the spiral case below high HD value comes out.(2)Consulting the conclusion through optimizing cushion layer,take the mode a sector of spiral case with high HD value to further simulate the effect on structure stress and cracks with different reinforcement ratio and arrangement,and then select the best reinforcement ratio and arrangement.(3)Based on the selected reinforcement ratio,establish the whole 3D spiral case model using cushion layer.Taking care of concrete crack,structure intensity , distortion , crack width and crack distribution of reinforced concrete are studied under static load.(4)Through computing natural frequency of spiral case one of the structures in hydropower station and analysis vibrancy source of hydraulic turbine set, estimate the possibility of resonance between spiral case and turbine set .So as to make sure the feasibility of spiral case using cushion layer with high HD value.During the modeling and calculating,the simulation of structure is as accurate as possible to reflect the characteristic of real engineering.As a result,some useful conclusions are drawn and can be referred to other similar projects.