抄録
Flow-induced acoustic resonances in piping with closed side branches are one of the phenomena causing severe structural vibration and fatigue damage of piping and components in many engineering applications such as power plants. In the United States, the steam dryer of the boiling water reactor was damaged by high-cycle fatigue due to acousticinduced vibration under a power uprating condition. Practical piping systems of power plants often have a steam flow, and moreover, the steam state can be not only dry steam but also wet steam, including nearly saturated conditions. Although many researchers have investigated acoustic resonances at side branches, the acoustic resonances under a wet steam flow have not yet been clarified since previous studies were mainly conducted under an air flow, and there have been few previous experiments performed under a steam flow, particularly a wet steam flow. From our previous experiments under low-pressure dry and wet steam flows using side branches with single-, tandem-, and coaxial-type arrangements, higher acoustical damping was confirmed under wet steam than that under dry steam, which is considered to be caused by the existing liquid phase. Although the static pressure in practical steam piping is often higher than that in our previous experiments, the effects of the static pressure on acoustical damping under a wet steam flow have not been clarified. In this paper, we give experimental results under higher-pressure dry and wet steam flows than those in our previous studies and discuss the influence of the static pressure on the pressure fluctuation of acoustic resonances under a wet steam flow.
