Effect of pressure gradient along axial direction of vortex-core on gas entrainment flow rate

Torikawa, Tomoaki*; Odaira, Naoya*; Ito, Daisuke*; Ito, Kei*; Saito, Yasushi*; Matsushita, Kentaro ; Ezure, Toshiki ; Tanaka, Masaaki  

On free surface of a sodium cooled fast reactor, gas entrainment can be caused by free surface vortices, which may result in disturbance in core power. It is important to develop an evaluation model to predict accurately entrained gas flow rate. In this study, the effect of pressure gradient in vortex axis direction on the gas entrainment flow rate is investigated in a simple gas experimental apparatus, in which upper and lower tanks are connected by a suction pipe. As a result, it was observed that there are two flow regime: swirling annular flow regime shows the tendency that only the gas entrainment flow rate increases with almost constant pressure gradient, then, when liquid plug is induced by the development of free surface disturbance, the gas entrainment flow rate increases as the pressure gradient increases. In addition, it was confirmed that the transformation of those two flow regimes is advanced by higher liquid level in the upper tank.