Numerical and experimental analysis for the effect of oil mist flow characteristics on the penetration and lubrication performance in MQL milling

The penetration of oil mist and its lubrication capabilities in Minimum Quantity Lubrication (MQL) are closely related to the flow field characteristics. However, due to the lack of comprehensive studies on the nozzle atomization performance and the distribution characteristics of the flow field in the cutting zone, an in-depth understanding of the lubrication mechanism of MQL remains a challenge. This study simulated the single-nozzle atomized flow field and flow field distribution characteristics of the dual-nozzle MQL milling using the computational fluid dynamics (CFD) technique. The effects of air pressure and flow rate on the flow field characteristics, such as droplet diameter, number of droplets, flow velocity, and volume fraction, were analyzed. Additionally, the effects of nozzle distance and incidence angle on the flow field distribution characteristics around the milling cutter were also examined. By combining laser particle size analysis with MQL milling experiments, the optimal conditions for lubricant penetration into the cutting zone were identified, revealing the low-pressure vortex lubrication mechanism of MQL. The results indicate that the optimal conditions for oil mist delivery are air pressure of 0.4–0.5 MPa, flow rate of 40 mL/h, and droplet diameter of 5–9 μm. Furthermore, the cutting performance of MQL reaches its best when the nozzle distance and incidence angle are 35 mm and 30°, respectively. The findings of this study are significant for understanding the lubrication mechanism and enhancing the cutting performance of MQL.