The operational flexibility of steam power plant is becoming more important as power generation becomes increasingly decentralized, with a growing contribution from renewable energy sources. In a power plant the control valve is a key component to guarantee the control of the plant of which is increasingly demanded to extend the operational capability. At specific operating conditions, the control valve could experience vibrations. In this paper, the physical phenomena of the unsteady aerodynamic excitation force have been investigated by means of CFD techniques. An in-house code was used to simulate the flow-induced vibration. Unsteady transonic 3D simulation generally requires huge computational effort. A novel unsteady quasi-3D approach has been developed and applied as pre-design tool to establish the qualitatively operational map of the valve and to detect the critical operational range, to reduce the number of detailed 3D simulations. The numerical results are compared with experimental test undertaken in the Central Research Institute of Electric Power Industry and full 3D simulation performed with the commercial tool CFX, using the Scale-Adaptive Simulation (SaS) turbulence model. Different pressure drops at certain lift have been selected from the operational map and reproduced numerically. Different modes have been identified, from stochastic behavior with wide width of frequency to periodic flow with one dominant frequency. Results indicate good agreement between the predicted frequency and amplitude and benchmark experiments. The quasi-3D simulation is able to reproduce the principle behavior of the flow field for different drop of pressure and capture the different operational mode. Similar behaviour has been detected also for the selected operating condition in the full 3D analysis. In addition, flutter calculation of the downstream pipe is carried out. It has demonstrated that the implementation of oscillating discharge piping influences the amplitudes and frequency of the upstream flow region.
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