Numerical Analysis Of Bubble Moving And Mass Transfer In Melt Aluminum Under Rotating And Ultrasonic Compound Field

Aluminum and its alloy castings have a wide range of applications in mechanical manufacturing,aerospace,daily life and other aspects,therefore,it is particularly important to improve the technological properties of the aluminum alloy castings.The hydrogen in aluminum melt,as porosity,aluminum and its alloy castings in white,etc.the main reason of the hydrogen cracking defect,limiting the mechanical properties of aluminum alloy castings and improve,reduce the service life and so on,and the removal of aluminum melt was studied and the mechanism of gas purification technology will be improved very much important.In this paper,based on the existing degassing method,a combined purification method is proposed,which combines the rotating blow cleaning method with the power ultrasonic purification method.This method mainly uses hydrogen concentration difference between inert bubble and liquid phase melt,so that hydrogen diffusion in melt can be transferred into inert bubbles and discharged by bubbles.Ultrasonic action can accelerate the process and improve purification rate.In order to determine the influence of the process parameters on the purification process of aluminum and its melt clearly,the process parameters in favor of the purification process are obtained.The movement process and the diffusion process of the purge bubble in the process are analyzed,and the coupling equations of the transient motion and mass transfer about the purification bubble are obtained.And using the numerical analysis method of the analytic equations,purify the bubble movement path,the bubble radius and the bubble mass transfer rate in different process parameters(rotation rate,the incident gas flow rate,ultrasonic frequency and ultrasonic pressure amplitude)curve with time changing under the influence,to help us get the optimal process parameters.According to the theoretical analysis,it can be obtained that ultrasound has less influence on the trajectory of the purge bubble,When the ultrasonic frequency is in the range of 20 k Hz ~50 k Hz,and the amplitude of ultrasonic pressure varies at 100 k Pa~160 k Pa,it is possible to determine the ultrasonic field frequency of 50 k Hz for the purification process of aluminum and its alloy melt,and the ultrasonic pressure amplitude is 100 k Pa.According to the theoretical analysis,the motion trajectory of the purge bubble can be affected mainly by the rotation effect,but the change trend of the mass transfer rate radius of the purge bubble is not much affected.When the rotational speed range is at 450 r/min~600 r/min,the rotation speed of the purification process is 450 r/min,which is most beneficial to the purification process.According to the theoretical analysis,the incident flow rate of the purified gas can be mainly affected by the change of the radius of the purge bubble and the change of the mass transfer rate of the purge bubble;When the flow rate of incident gas is in the range of 500 ml/min~800 ml/min,600 ml/min can be determined as the optimal flow rate of gas.According to the similarity principle,we can use the water simulation experiment to simulate the process,to verify the results of the analysis.The experimental results are basically the same as the numerical analysis results,which proves the practicability and reliability of the coupled equations of the transient motion and mass transfer of the purification bubbles in this paper.