Performance of supercritical carbon dioxide sprays as coolants and lubricants in representative metalworking operations |
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Authors: | SD Supekar AF Clarens DA Stephenson SJ Skerlos |
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Affiliation: | 1. Department of Mechanical Engineering, The University of Michigan at Ann Arbor, Ann Arbor, MI 48109-2125, USA;2. Department of Civil and Environmental Engineering, The University of Virginia, Charlottesville, VA 22904-1000, USA |
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Abstract: | This paper investigates the cooling and lubrication properties of supercritical carbon dioxide (scCO2) sprays as potential substitutes for aqueous emulsions and straight oils used in the metalworking industry today. Sprays of rapidly expanding scCO2 act to cool and lubricate machining and forming processes by delivering a mixture of dry ice and lubricant deep into the cutting/forming zone. In this work, experiments with turning, milling, drilling, thread cutting, and thread forming were performed with scCO2 and other metalworking fluids (MWFs) to evaluate their relative performance with respect to tool wear and machining torque. Observations reveal that scCO2–MWFs are more effective in removing heat from the tool-workpiece interface than conventionally delivered (flood) aqueous MWFs as well as other gas-based MWF sprays. In addition, scCO2–MWFs delivered in lubricant-expanded phase, where scCO2 is used to increase volume of lubricant in the spray field, are shown to provide better lubricity than straight oils and oil-in-air minimum quantity lubrication (MQL) sprays. As a result, scCO2–MWFs can reduce tool wear and improve machining productivity in a wide range of manufacturing operations leading to appreciable improvements in the economics of manufacturing. Also given that CO2 is a recovered waste gas that is non-toxic, scCO2–MWFs can improve the environmental and worker health performance of manufacturing operations. |
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Keywords: | MWF metalworking fluid scCO2 supercritical carbon dioxide NDL no dissolved lubricant DL dissolved lubricant XL expanded lubricant HRP heat removal potential HRE heat removal efficacy LE lubrication efficacy |
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