Three-Dimensional Calculation of Air-Water Two-Phase Flows in a Centrifugal Pump Based on a Bubbly Flow Model with Fixed Cavity.

Abstract

Three-dimensional two-phase flows in a centrifugal pump have been analyzed numerically by the authors on the basis of a so-called bubbly flow model. The local void fractions obtained, however, seem to amount to somewhat higher values than the applicable range of the model. In this paper, a revised model is proposed to extend the applicability under the assumptions that the bubbles in high void fraction regions adhere to the impeller walls just as in a fixed cavity, and this model is applied to the analyses for a radial-flow pump. When the inlet void fraction exceeds a critical one, the fixed cavity obtained expands rapidly from the shroud to the hub in the section just after the impeller inlet and fills the section. When the pump is operated under a two-phase flow condition, it loses its function at nearly the same inlet void fraction due to the blockade of the entrained air. This model is thus applicable to the prediction of the limit of pumping activity.