Kinetic model of hydrogen gas bubble evolution in magnesium melt

The kinetic property of hydrogen was analyzed in the process of hydrogen gas bubble evolution. According to the force analysis, a transient acceleration equation of hydrogen gas bubble in magnesium melt was established by the Newton's Second Law considering influential factors. Simultaneously, a kinetic model that described the changing relation of hydrogen gas bubble velocity, radius, rising height and time was obtained by in combination with three other equations and theoretical deduction. These equations were the boundary layer mass transfer equation, the gas state equation and the nature of stream function. Simplified model was verified by programming on MATLAB with Runge-Kutta. A relation graph of bubble transfer speed and time was obtained. Meanwhile, the relation graph of bubble radius change rate and time was also got. The results show that the bubble speed and radius grow with the rising height increasing in the hydrogen gas bubble evolution. And the acceleration increases firstly, and then decreases. While it rises to the surface, the bubble precipitates at a certain velocity and breaks. The model offers theoretical basis to the formation mechanism of hydrogen gas bubble in magnesium melt, which has great significance for controlling process of production in molten magnesium. © 2015, Central South University of Technology. All right reserved.