INVESTIGATION OF COOLING EFFICIENCY AND STRUCTURAL CHARACTERISTICS OF SUPERCRITICAL CO2 JETS FOR MACHINING ASSISTANCE

In a context of safer, more cost-effective, and environmentally friendly machining processes, supercritical carbon dioxide (sCO2) emerges as a promising alternative to conventional cutting fluids. However, a consolidated understanding of the optimal sCO2 jet parameters for machining and its impact on the tool and the material remains unavailable. This work intends to address the behavior of a free and impinged sCO2 jet structure and its geometrical evolution in function of the upstream jet conditions. The supersonic structure and parameters were analyzed under varying initial pressures and temperatures in both near and far fields. The obtained images showed the detailed jet structure and highlighted the presence of three different zones within the flow: laminar, transitional then turbulent. To investigate this behavior and to better understand the jet’s cooling ability in these different zones, an in-depth analysis of the jet’s complex structure was carried out using high-speed imaging combined with an optical imaging known as Schlieren.