Investigating Behavior of Hydrogen Bubbles in Electro-Chemical Machining

Electro-Chemical Machining (ECM) is an advanced machining technology and has been applied to highly specialized fields, such as aerospace, aeronautics, and medical industries. However, some problems remain to be solved. The efficient tool-design, electrolyte processing, and disposal of metal hydroxide sludge are typical problems. To solve such problems, CFD is thought to have potential as a powerful tool. However, a numerical method that can satisfactorily predict the ECM process has not been established because of the complex flow natures. In a previous study, we presented a new model to simulate the flow fields in an ECM process. This model is based on a two-way coupling method, taking the interaction between gas and liquid phases into account. In this coupling method, we assumed that electrolyte and generated hydrogen bubbles over a cathode surface have the same velocity. Therefore, we could simplify the governing equations. Since the flow field had a non-uniform density distribution due to hydrogen bubbles, a low Mach number approximation was applied to solve the pressure Poisson equation. In the present study, we calculate hydrogen bubble trajectories and investigate the distribution and a behavior of hydrogen bubbles. Since hydrogen bubbles follow fluid well, they travel along the stream line. This is because hydrogen bubbles have small density. In the results, around the low velocity region, hydrogen bubbles remain there with making the spiral structure. Hydrogen particles remain more in the suction side than that in the pressure side of the blade.