Vibration Experiments and Numerical Simulations of Pulsation Behavior in Actual Size Mock-Up Piping

Vibration experiments for pressure pulsation behavior were made using actual size mock-up piping of nuclear power facilities. The mock-up was a closed loop consisting of a three-strand plunger pump, tanks, piping and valves. It was 40 m long to allow interaction of the acoustic resonance frequency of fluid inside with the mechanical natural frequency of the piping. The influence of valve closing and opening operations to change inner pressure during pump operations on the pulsation boundary condition was investigated in this study. A drastic change in the boundary condition of the acoustic resonance behavior by using a slightly different valve opening ratio to set a different inner pressure was shown in the experimental results. The phenomenon was numerically simulated by using the method of characteristics. The simulation results showed that the boundary condition of the acoustic resonance changed from the closing-opening condition to the closing-closing condition when the valve opening ratio was changed slightly from 10% to 15%. This indicated that the boundary condition of the acoustic resonance had a pulsed change. Therefore, the boundary condition of the acoustic resonance was sensitive to a slight change of the valve opening ratio.