Combined Effects of Steam Wetness and Pressure on Characteristics of Acoustic Resonance Amplitude in Closed Side Branch

Steam piping and components in many industrial applications such as power plants sometimes experience structural vibration and fatigue damage caused by flow-induced acoustic resonance in piping with closed side branches. The state of steam in the steam piping can be not only dry (superheated) steam but also wet steam (i.e., a two-phase flow comprising a mixture of saturated steam and saturated water). From our prior research on the general characteristics of acoustic resonance under wet steam flows, the maximum pressure amplitudes under low-pressure wet steam were significantly lower than those under dry steam, which is considered to be caused by the presence of a liquid phase. Here, we investigate how the steam wetness and steam pressure affect the maximum pressure amplitude since practical steam piping may be exposed to various conditions. Experiments on acoustic resonance in a single side branch were conducted under high-quality wet steam flows with a steam pressure of up to 0.8 MPa and a steam quality of 0.9 < x < 1.0 as parameters. For our experimental conditions, it was confirmed that the steam pressure and steam state had little impact on the critical Strouhal number, whereas the maximum amplitudes under wet steam were markedly lower than those under dry steam. Different dependences of the maximum amplitude on the Reynolds number were confirmed for dry steam and wet steam. Moreover, the reduction of the maximum pressure amplitude under wet steam was affected by both the void fraction and the density ratio.