中文摘要：

在超高压水射流切割过程中，射流结构是设备工作效率及损耗程度的决定性因素，本文针对400MPa范围内超高压水射流结构进行了数值模拟及实验研究，得到了相关因素对其具体影响。结果表明：超高压水射流的流柬可分为几个特征各不相同的区域；射流的发散程度随着压力和宝石孔径的增大而增大；喷嘴形状对射流结构具有显著的影响，渐扩的锥形出口及倾斜的出口端面有助于增强射流的集束性；宝石孔内的空化直接影响了射流的形成；空化加剧了宝石的磨损，随着宝石孔入口的磨损程度提高，水射流趋于发散。

英文摘要：

The jet structure in the ultra-high pressure water jet machining has a crucial effect on the working efficiency and processing cost. In this research, the water jet at pressure within 400 MPa is simulated and is investigated by experiment. The influences of key factors on the jet structure are discussed. It is found that the jet stream can be divided into several zones with different flow characteristics; the jet leads a faster dissipation when the operating pressure is enhanced or the orifice diameter of jewel nozzle is enlarged; the structure of the jewel nozzle impact jet obviously, the jewel holder with a cone-down outlet or a cone-down seal can improve the jet coherency; cavitation in the orifice has a distinct effect on the jet formation and it increase the wear of the jewel orifice; the jet is more dissipated as the erosion in the inlet of orifice increases.