Parameter Optimization of the MQL Nozzle by the Computational Fluid Dynamics

Minimum quantity lubrication (MQL) has achieved excellent results in precision machining. The geometric parameters of the nozzle play a crucial role in determining the performance of MQL. In this study, the orthogonal experimental method was employed to improve and optimize the performance of MQL. Computational fluid dynamics (CFD) simulation using ANSYS Fluent software was conducted, and the simulation data were statistically analyzed. The effects of six influencing factors, namely, the width of the gas-phase narrow flow region, the taper, the output tube length, the length of the gas-phase narrow flow region, the output aperture, and the pressure, on the performance of MQL were investigated. The results revealed that the order of importance for the six influencing factors differed depending on the evaluation criteria used. The parameter that had the greatest impact on the composite index was the absolute gas velocity at a distance of 0.1 m from the outlet. The optimum combination of geometric parameters for the nozzle was an output aperture of 2 mm, a taper of 40°, a length of the gas-phase narrow flow region of 1.5 mm, a width of the gas-phase narrow flow region of 0.3 mm, an output tube length of 15.5 mm, and a pressure of 5 bar.