【作者】 雷向阳；

【导师】 李晓红；

【作者基本信息】 重庆大学 ， 安全技术及工程， 2003， 硕士

【摘要】 高压水射流作为目前唯一的一种冷切割加工方式在各行各业得到了日益广泛的应用，前混合磨料射流可以切割材质的种类相当多。随着海洋开发力度的加大，水下切割作为一门新型水下成形加工技术开始得到研究和发展。然而，前混合磨料射流在高围压下的实验和理论研究甚少，针对这一情况，进行了该项研究。本文主要围绕如何优化高围压下前混合磨料射流各切割参数，从而提高前混合磨料射流在高围压下的切割性能和工作效率，研究的内容包括：高围压下前混合磨料射流的穿透特性、切割及冲蚀机理研究，高围压模拟实验装置设计和高围压下前混合磨料射流的切割实验研究。通过理论分析和实验研究，得出的主要结论如下：① 在围压下，随着围压的增加，环境介质密度随之增加，空化效果减弱；随着的增加，衰减系数增加，环境介质对射流的阻力增强，导致射流轴线速度呈指数衰减，降低了围压下射流轴心动压，减小了射流核长度，降低了射流的切割和冲蚀性能。② 前混合磨料射流在围压3.3MPa、5.3MPa和8.6MPa下的有效靶距喷嘴直径比Sv/d为8.3、5和3.3。随着围压Pw的增加，有效靶距与喷嘴直径比Sv/d呈指数衰减。③ 前混合磨料射流在高围压下切割时，对于切割一定的深度，开始的几次（4～8次）切割起主要作用，这与在空气中切割的情况类似。④ 在高围压下前混合磨料射流的切割深度随喷嘴横移速度的增加呈幂指数衰减，最佳横移速度为4～6mm/s。 ⑤ 随着围压的增加，切割深度衰减较快，切割性能有非线性减小的趋势，对于不同靶距其衰减规律类似。本文在研究高围压下（围压达10MPa）前混合磨料射流的切割性能方面有所创新，丰富了前混合磨料射流的切割冲蚀机理，对拓宽水射流的应用领域具有重要意义，同时为前混合磨料射流在水下营救和打捞作业、水下修理、水下岩石取样、石油钻井、海上平台的拆卸、航船的水下作业和海洋工程等方面的深入应用奠定一定的理论和实验基础。更多还原

【Abstract】 The AWJ cutting technique is currently used in a wide variety of in-air industrial cutting applications. An AWJ can cut virtually any material and, since the process is a cold cutting process, it does not create a heat-affected zone. With the development of ocean exploitation, AWJ cutting in underwater begin to be studied as a new way of process under the water. However, pre-mixed AWJ cutting technique in deep ocean (high ambient pressure) is virtually not investigated in our country. Owing to it, this thesis is conducted in pre-mixed AWJ cutting applications in high ambient pressure.For optimizing the parameters of pre-mixed AWJ cutting in high ambient pressure, the content of research in this thesis includes the mechanism of pre-mixed AWJ cutting in high ambient pressure, the design of experimental devices simulated the high ambient pressure and experimental investigation of pre-mixed AWJ cutting in high ambient pressure.Some important results are listed as follow:1. Owing to the attenuation coefficient () of jet caused by resistance of the medium between nozzle and material in high ambient pressure, jet velocity on the axis is supposed exponential attenuation. With the increase of ambient pressure, the density of medium () increases and cavitations effects reduce. Meanwhile, jet velocity on axis decreases resulting on decrease of jet axial pressure and shortened jet core which finally reduce the jet cutting and erosion ability. 2. The ratio of valid stand-off distance to diameter of nozzle (Sv/d) is 8.33, 5 and 3.3 as the variation of ambient pressure as 3.3MPa, 5.3MPa and 8.6MPa. With the increase of ambient pressure, the valid stand-off distance (Sv) is exponential attenuation.3. For a definite kerf on sample in ambient pressure, the firstly several cutting times (4~8 times) are predominate, which is similar to pre-mixed AWJ working in air.4. With the increase of ambient pressure, the traverse rate is<WP=6>attenuated in exponent sign.5. It is found from experiments that the kerfs depth quickly falls with increasing of ambient pressure.These results demonstrate that pre-mixed AWJ holds great promise as safe and effective tools in rescue salvage operations, repair, offshore platform removal and deep ocean operations.更多还原