The Formation And Distribution Of Bubbles In Refining Process By Pulse Gas Injection With Rotation

Aluminum alloy has been widely used in aerospace, manufacture and other feldsdue to the properties of low density, high specific strength, corrosion resistance andother perfect properties. However, gases and inclusions in the molten aluminum weredifficulty to remove during refining process. So the quality of the early products ofaluminum was greatly reduced. Purification methods commonly used in industrialwere degass and impeller method and flux method. The bubbles in the moltenaluminum were break by rotor during the purification process when the rotator rotary,so the bubbles were small and less gas and inclusions in the molten aluminum.However, the stirring of the melt was very serious, making the rise bubble withabsorbed gas and the adsorption of a mixture to the melt surface re-involved in themelt, which was not conducive to the purification process. Flux method can produceuniform small bubbles in the melt, but pollute the melt, and not conducive toenvironmental protection. Goals of aluminum alloy refining are environmentalprotection, static purification methods. Study the bubbles’ formation and distributionin static degassing process is particularly important.By combining the advantages of degass and impeller method and pulse gasmethod, self-designed and machined aluminum alloy cleaning device. The device wasmainly to achieve the purpose of the pulse gas into the alloy by the relative motion ofthe stator and rotor. Gases went into the device through the hole in the center of therotor pole and then went through the six air slot opening in the rotor. A certain sizeand a number of small holes were uniformly distribution on the stator. When the gastank turned to the location of the orifices, the gas went through the holes on the statorinto the melt to form bubbles; when the gas tank turned away from the orifices, no gaswould get into the melt. Rotation of the rotor had a cutting action on the gas in orderto achieve a pulse gas intake process and the availability of small bubbles.High-speed photography was used to capture the movement of bubbles in thewater-co2and polyvinyl alcohol-co2water simulation experiment to study the liquidproperties, the gas flow rate, rotor speed, orifice diameter, and distance betweenorifices and other parameters on the bubble departure and rising. Vof model of fluentwas used to the bubble departure and the rise of the process, in contrast to watersimulation to verify the correctness of the numerical simulation. By changing theexperimental parameters, the morphology changes of a single bubble, as well ashorizontal double bubble and vertical pairs of bubbles rising in water and theformation process of the trajectory as well as nitrogen bubbles in the aluminum alloy liquid. To bubble rising in the liquid, the results showed that: to the rising of a singlebubble, big bubbles were more easily deformed or even broken. Bubbles’ risingslowed down with the increase of viscosity, but due to the impact of the bubblehorizontal swing, vertical center of mass velocity presented a different regularity asthe viscosity changed. The greater the surface tension, the bubble is more difficult todeform. The horizontal double bubbles’ rising trajectories were symmetry, as thedistance increases, the interaction between the bubbles was weak. So the doublebubbles could be seen as two single bubbles independent increase in the liquid. Theinfluence of liquid physical parameters on the horizontal double bubbles was similarto the law of motion of a single bubble. Surface tension had large effect on the twobubbles in vertical line, the bubbles got closer with each other to form a unstablebubble then break with smaller surface tension. To the bubble formation anddetachment process, the results showed that: the time for the bubble detaching fromthe orifice and the size of the bubble become larger when the orifice were large. Andso was the large gas velocity. The number of bubbles formed in united time wasincreased with large gas velocity, but decreased with large orifice diameter. Thebubbles size detaching from the orifice increased with the climbing of the liquidviscous and surface tension, the number decreased. The size of bubbles and thenumber of bubbles increased with larger density. Low gas flow rate better to combinewith big pulse time which with corresponding to slower speed and high gas flow ratebetter to combine with small pulse time. Pulse obvious impulsive phenomena of lowflow and high flow remains continuous bubble phenomenon, but the bubble volumedecreases, the aggregate situation improved significantly.