Computer fluid dynamics analysis for efficient spraying of oil mist in finish-turning of Inconel 718

A compressible turbulence analysis of the flow of oil mist in MQL finish-turning of Inconel 718 was conducted using a finite volume method for optimizing the spraying conditions of oil mist and reducing the oil consumption. First, a domain of the analysis including a rotating workpiece and a single point cutting tool with a spraying nozzle was discretized, and then, changes in the velocity, pressure and vorticity of compressed air, and mass flow rate of oil mist near the cutting edge were calculated for three types of spraying nozzles. It was found that when the distance from the outlet of a nozzle to the tool tip was decreased using cover-type nozzles, mass flow rate of oil mist to near the cutting edge increased drastically. Among the three types of nozzles, the mass flow rate was the largest for a cover-type nozzle for oblique spraying. These results were consistent with the performance of the nozzles in cutting experiments. Finally, the flight of an oil droplet and the lubrication mechanism in MQL machining were investigated using analysis results.