Study On The Behavior Of Bubbles Produced In Electrochemical Finishing

The cathode surface will precipitate hydrogen gas while REDOX reaction isoccurred under the action of electric field during electrochemical finishing. So theelectrolyte between the electrodes can be actually seen as a gas-liquid-solid threephase flow. For the electrolytic liquid viscosity coefficient is not a constant, theinterelectrode electrolyte can be seen as non-Newtonian fluid. During actuallymachining process, bubbles in the electrolyte are in state of movement, which wouldaffect the exchange of quality、heat and momentum, it also has a great difference onthe interelectrode flow field、concentration field and velocity field. This have madethe environment of flow field inside the gap more complex while machining, so it isvery necessary to study on mass transfer process in the gas-liquid phase and the flowfield distribution around the moving bubbles. So far, for the complexity of thebubbles’ movement in a fluid, theoretical research about momentum and mass transferprocess of non-Newtonian fluid is not thorough. This paper tries to investigate on thisissue with a numerical simulation method.Bubble behavior in non-Newtonian (NaNO3solutions) was simulated using aHigh-speed camera according to the similar principle. Bubble growth process wasrecorded by the PC in real time, correctness of the similar model is verified whilecompared with theoretical results of ZhuChunying. Moreover, Flow field、concentration field and velocity field around bubbles in non-Newtonian fluids(NaNO3solutions) were studied and processed by a digital image processingsoftware-COMSOL, results have show that the bubbles aren’t rising in a straight line,bubble shape is spherical at the beginning, but gradually become a “cone” soon. Asthe mass concentration of NaNO3increases, the liquid viscosity and elasticityincreases. The increase of the solution viscosity is not conducive to the mass transferprocess, however, the increase of elasticity can, on the other hand, promote mass transfer. Considering the two factors, with the percentage of NaNO3solutions increase,concentration of gas-liquid intersecting interface is on the decline in general, but thedeclining extent becomes mild gradually.In addition, experimental result also shows that in NaNO3solution, viscosityrestrains the formation of eddy in the vicinity of bubble. Finally, with the increase ofgas flow, bubble rising velocity increases obviously; eddy also increases in the flowfield as the flow of the chaos caused by bubbles have become more serious.