Research on the spiral case and external concrete structural response under limit operation state

Abstract

Abstract As the key component of hydroelectric generating units, the spiral case is primarily responsible to make the fluid flow out in a uniform and axisymmetric way. The structural response of the spiral case and external concrete under hydraulic pressure will have an effect on the operational security and power generation efficiency of the whole unit. In this paper, a three-dimensional fluid-structure coupling model of the spiral case and concrete under limit operation state is established. Based on the computational fluid mechanics theory, the flow domain inside the spiral case is simulated to study the stress and deformation structural response of the spiral case and external concrete under the action of maximum inner hydraulic pressure. The value and position of the maximum stress and deformation are determined. The fluid-structure coupling simulation shows that severe turbulence occurs in the middle of the flow channel. The maximum equivalent stress of the spiral case is located near its tongue and there would possibly be a risk of local structural damage. The external concrete can effectively share part of the load from the spiral case, so as to keep the strength and stiffness of the overall structure being within safe levels under the limit state. The results can provide support to the structural optimization and construction of the spiral case, which is helpful for the safety and stability of station operation.