In order to study the influence of the upper crown cavity on the hydraulic performance and structural characteristics of the hydraulic turbine, a geometric model of the whole passage of the hydraulic turbine including the clearance passage and the upper crown cavity is established. Based on the SST Turbulence model, the numerical simulation is carried out for the two kinds of runner with and without the clearance and cavity, and the one-way fluid solid coupling calculation is carried out. It is found that the upper part reduces the negative pressure at the discharge cone and reduces the backflow caused by the negative pressure in the runner. The fluid structure coupling calculation is carried out for the turbine with three flow rates of 0.8Qd, Qd and 1.2Qd. The stress-strain characteristics of the runner structure under three flow conditions are compared and studied. It is found that the equivalent stress and deformation of the runner structure are reduced when the upper crown clearance and cavity are considered. Under the flow rate of 0.8 Qd, the equivalent stress and strain of the runner structure are small, and the maximum deformation point is near the ring. Under Qd and 1.2 Qd flow conditions, the equivalent stress and strain of runner are large, and the maximum deformation point is near the upper crown of blade. The pre stress modal analysis of runner with and without upper crown cavity and clearance is carried out, and the results show that the influence of upper crown cavity and clearance on runner modal is very small. The research content of this paper can provide some reference for the design of turbine clearance in numerical simulation, the application and improvement of turbine crown cavity structure. © 2020, China Water Power Press. All right reserved.
