Liquid CO2 as a blasting media for cutting process

水射流切割采用磨料介质来提高切割性能。磨料的残留和对工件的润湿限制了其使用，特别是在切割医疗部件时。这促使了对新的切割工艺的研究。该项目的方法是使用液体二氧化碳喷射器进行切割操作。预试验表明，两相CO2射流可以用于切割不同的材料。该项目的目标是确定二氧化碳射流的产生和稳定原理，以及射流的识别和切割特性。为此，二氧化碳将被加压、回火，通过喷嘴进行引导，最终瞄准不同硬度的样品。在环境条件下，当处于热力学平衡时，二氧化碳只能存在于气相中。因此，了解相变过程中的亚稳态条件是至关重要的。因此，膨胀过程和自由喷流中的过程将通过成像系统进行研究。根据膨胀前后条件的不同，自由射流应该相对较长，最长可达几厘米。随着本项目的完成，我们了解了这一新的切割工艺的热力学和流体动力学原理，科学地确定了切割系统设计的边界条件。

Waterjet cutting uses abrasive media for improving the cutting performance. Residues of the abrasives and the wetting on the workpieces are limiting the usage, especially for cutting medical components. This motivates the investigation on new cutting processes. The approach of this project is the use of a liquid CO2 jet for cutting operations. Pre tests have shown that a two-phase CO2 jet can be used for cutting different materials. The goal of this project is to determine principles of the generation and stabilization of the CO2 jet as well as the identification of the jet and the cutting properties. For this purpose the CO2 will be pressurized, tempered, conducted through a nozzle and eventually aimed at a specimen with different hardness. Under ambient conditions CO2 can only exist in the gaseous phase, when in thermodynamic equilibrium. Hence, knowledge about metastable condition during the phase change is of vital importance. Therefore, the process during the expansion and in the free jet will be investigated by imaging systems. By variation of pre- and postexpansion conditions the free jet should be relatively long, up to several centimeters. With finishing this project the thermo- and fluiddynamically principles of this new cutting process are known and the boundary condition for the design of a cutting system are determined scientifically.