Application of CFD and vapor bubble dynamics for an efficient electro-thermal simulation of EDM: an integrated approach

Abstract

Micro-chip removal and heat dissipation are two important and essential utilities of dielectric medium along with its vital contribution in plasma channel formation, which has a significant influence in metal removal, tool wear, and surface integrity. The vapor bubbles, which are formed after every progressive spark, expand and collapse in the electric field and finally condensed inside the dielectric medium. As the localized heat and excess temperature of the eroded spot increases, the dynamic properties of the bubbles accelerate and develop a lower pressure region, which is responsible for dielectric flushing. In this paper, the integrated approach of vapor bubble dynamics and computational fluid dynamics is used to study the dynamic behavior and heat dissipation of dielectric fluid through the plasma channel. At the very beginning of machining, the excess temperature is comparatively low; so, the detached bubbles are condensed inside the fluid medium and are not able to move above the free surface. However, as the temperature of the machined zone rises, excess temperature also increases and bubbles are able to carry the heat up to the free surface of the dielectric medium and finally condense. This phenomenon is very much analogous to the boiling process. Earlier, many simulation processes are used by researchers to investigate heat flux and heat dissipation rate of the dielectric fluid, but, here, vapor bubble dynamics and periodic heating are introduced to consider heat absorption by vapor bubbles, which gives more accurate heat transfer analysis of electric discharge machining. It is observed that the adopted model has the accuracy level of more than 95% with 4.5–4.6% of average prediction error and 1.5–2% more efficient than the existing models.