The application of minimal quantity lubrication (MQL) with inline-mixed multi-component cutting fluids enables effective lubrication and cooling in machining processes through oil-on-water (OoW) droplet generation

which necessitates an optimized mixing system. This study developed a precision inline mixing MQL system with optimized structural configurations to enhance heterogeneous cutting fluid droplet fusion. The research methodology comprised numerical simulations assessing droplet distribution uniformity across various mixer designs

complemented by experimental validation through spray pattern analysis and deposition characterization. Results indicate that the DPM (Discrete phase model) model can be applied to numerically simulate the migration movement of the heterogeneous pre-atomized cutting fluid droplets in the mixer

and the area-weighted uniformity index (γα) can be applied to extract and analyze the distribution characteristics of the droplets at the outlet section of the mixer

which can effectively measure the inline mixing efficacy of the mixer. The nozzle diameter dn and the number of injection ports n have significant effects on the distribution uniformity of water droplets in the end section of the mixer

while the area ratio m and the diverter length Lnt have no clear effects. Moreover

only the Lnt has no significant effects on the uniformity of the oil droplet distribution in the detection section. The optimal parameters of the mixer determined by numerical simulation are no (Number of oil jet inlets) = 2

nw (Number of water jet inlets) = 3

dn = 2 mm

Lnt = 7 mm

m = 1∶2. The physical spraying tests indicate that the spray deposition CV (Coefficient of variation) value of oil-based and water-based cutting fluid is as low as 0.2050 and 0.3183

and the corresponding γim (Deposition uniformity index) is as high as 0.9165 and 0.8888

respectively. The spraying deposition uniformity for the mixer with optimal structural parameters is better than that for other mixers. The optimized mixer configuration achieves superior deposition uniformity compared to alternative designs. Enhanced main and pre-atomization airflow parameters significantly improve deposition uniformity while reducing droplet diameter for both oil-based and water-based cutting fluids. The optimized system effectively ensures heterogeneous droplet fusion

eliminating single-phase droplet formation and meeting practical application requirements.