Abstract
Transonic flow vibrations in a main flow control valve for nuclear and thermal power plants are investigated. In the steam control valve, flow becomes supersonic around the valve head. Shock waves appears and cause flow separations. As a result, serious pressure fluctuations appear. In the present study, experimental and numerical simulations are carried out in order to clarify the cause of a flow induced vibration of the valve head. Unsteady fluid forces are examined with exciting the valve head. Results show that the unsteady fluid force acts as a negative damping force at certain operating conditions and a self-excited oscillation with large amplitude appears.
