Numerical analysis of the impact of the ECM inlet geometry on the electrolyte flow and its interaction with a thin-walled workpiece

The numerical simulation of the (precise) electrochemical machining (P)ECM process faces many challenges due to the interaction of the various physical effects involved, the wide range of spatial and temporal time scales, and the limited experimental access to the process for the validation of numerical methods. The material removal in the working gap is largely determined by the electrical field and the multiphase flow of the electrolyte. Due to limited optical access into the working gap, not much is known about the details. However, an accurate numerical simulation of the machining process needs information about gas bubble sizes, local bubble concentration and the fluid structure interaction. This paper presents advanced simulations of electrolyte flow in the ECM process applied to thin-walled turbomachinery blades, incorporating process gas transport. To the best of the authors’ knowledge, turbulent electrolyte flow is predicted using a large-eddy simulation (LES) approach for the first time in ECM research. To address the high computational cost of LES, two reduced model configurations are also evaluated. The results are compared in terms of the electrolyte flow field, the transport of the process gases, and the forces that the electrolyte exerts on the workpiece. The results reveal that the conditions upstream of the working gap have a non-negligible influence on the flow field in the gap and have to be carefully chosen depending on the focus of the simulations. Furthermore, the simulation effort could be reduced by 16% and 31% using shortened inlet configurations, which were still able to reproduce most of the physical effects captured in the full simulation.