Simulation Of Aluminum Melt Foaming Process

Through water simulation experiment combine with aluminum foaming experiment, the foaming process of aluminum melt was studied. Using high speed photography technology recorded the bubble formation and ascension in the PVA solution. Analyze bubble shape, size and velocity variation. Study the bubble trajectory distribution with different gas flow rate, orifice diameter and stir speed. Combining with aluminum foaming experiment, the influence of bubble size on different processing parameter was studied. The influence of pressure decrease on surface bubble diameter was studied. Through force analysis on the bubble, the bubble size prediction model was derived.The experiment results indicate that the bubble is the ellipse spheroid during the process of expanding. When the bubbles completely out of orifice, their shape change into flat sphere. The limit speed of bubble during ascent in the PVA is 382 mm/s. In the static flow field, the rising trajectory of a single bubble is a spiral curve with increasing period and amplitude. when the single hole incidence airflow discharge(0.025~075 L/min), the immersion depth increase from 160 to 330 mm and the orifice diameter changing from 0.3 to 0.2 mm, the bubble oscillation amplitude increased. In the dynamic flow field, the bubbles were sinusoidal distribution in the foaming room, and increase the velocity of air tube can improve the uniformity of bubbles.When the biggest linear velocity of air tube is increase from 0 to 366 mm/s, the bubble diameter of water simulation is reduced from 3.38 to 2.65 mm and the bubble diameter of aluminum reduced from 10.44 to 2.95 mm. The relative error of simulation and experiment is 10.17% with the velocity of air tube is 366 mm/s. When the air flow is increase from 0.025 to 0.075 L/min, the bubble diameter of water simulation is increased from 2.48 to 2.93 mm and the bubble diameter of aluminum increased from 2.62 to 3.61 mm. The water experiment results indicate that when the liquid viscosity changing from 2.27 to 16 mPa.s, the bubble diameter increases from 2.33 to 2.48 mm. When the immersion depth of the orifice increase from 150 to 330 mm, the bubble diameter of water simulation is increase from 2.25 to 2.57 mm, and the bubble diameter of aluminum is 2.732 mm, Consider the static pressure, The relative error of experiment and simulation reduced from 15.45 to 3.22%. The bubble generated from the first size of air tube is bigger than the other side (2.72~6.24%). Increase the air flow and the length of air tube or reduce the pipe diameter, the inconsistent of bubble size is greater.