Study on transient characteristics during closing process of large ball valve in pumped storage power station

The 1D MOC and 3D hydraulic transient are proposed respectively to investigate transient flow characteristics inside a ball valve, as well as the UFSI models for its relevant dynamic structural responses during ball-valve closing and load rejection in a pumped storage power station. The historical transient-pressure evolution is in good agreement with the experimental data with the corresponding relative errors of 0.37 % and 7.36 % respectively. Based on 3D standard k-ε and sliding-grid technology, there are six vortices in the Y = 0 m plane and two anticlockwise vortices in the X = 0 m plane, and the predicted steady-resistance coefficients are closer to the experimental data compared with the predicted unsteady ones. The predicted pressure evolutions are both consistent with the results by 1D MOC and the experimental data, but pressure fluctuations can be captured, compared to the experimental data, the corresponding relative errors are 0.23 % and 0.37 % respectively. Based on dynamically applied pressure load along with sliding-grid technology and the USFI, compared to the experimental data, all these predicted maximum relative errors including circumferential dynamic stress, axial dynamic stress, axial displacement, vertical displacement, the accelerations at two monitoring points are 35.7 %, 17.3 %, 29.42 %, 8.82 %, 38.46 % and 4.45 % respectively, which are within the allowable safe range.