A three-dimensional numerical method is proposed on the basis of a bubbly flow model, in order to simulate the behavior of gas-oil two-phase flows in a rotodynamic pump impeller. In this model, the two-phase flow prediction technique is an iterative method composed of two parts: The first is the calculation of continuous-phase (liquid) velocity field assuming that the distribution of gas void fraction is given. For the 3D numerical solution of the liquid governing equations, a procedure called "steam-surface coordinate iteration" has been adopted. The second is the calculation of dispersed-phase (bubble) trajectories when the liquid flow field is known. Governing factors for the bubble motion are the force due to the pressure gradient, the drag force due to the flow resistance of the surrounding liquid, and the inertia force due to virtual mass of liquid. The equationof motion of gas bubbles are solved numerically to obtain the gas void fraction. These calculation are iterated to get a convergent solution. The method has been applied to multi-stage helico-axial booster-pump impellers. According to the calculation, it is found that trajectories of gas bubbles do not considerably deviate the path of liquid in blade-to-blade surfaces. In bub-to-shroud surfaces, however, almost all bubbles are finally shifted toward hub of impeller no matter where their initial positions are. It is expected that the model will enable us to predict some two-phase flow phenomena due to its simplicity and effectiveness, thus becoming an efficient design-tool for gas-liquid two-phase booster-pumps.
展开▼
