Investigation of superheated liquid carbon dioxide jets for cutting applications

Water jet cutting is of increasing interest in manufacturing technology. By using carbon dioxide (CO2) instead of water, a dry processing becomes possible. To realize cutting results comparable to water, liquid and coherent CO2-jets with high specific energy have to be formed. However, CO2 does not exist as a liquid in thermodynamic equilibrium at atmospheric pressure. During the expansion through a nozzle from a liquid state to atmospheric pressure the saturation curve is crossed and a spray consisting of a gaseous and solid phase is generated. We show that with sufficiently low injection temperatures the phase change is delayed and liquid jets emanate from the nozzle even at atmospheric pressure. These jets disintegrate closer to the nozzle than water jets at same pressure and nozzle conditions. The shorter jet length results in lower kerf depths. But the kerf width is smaller with CO2 and a more precise cutting is possible.