Sheathed Abrasive Water Suspension Jet Nozzle for Submerged Application

磨料水悬浮射流(AWSJ)在水下条件下的钻井能力随着钻井距离的增大而急剧下降，钻井和切割的有效工作距离限制在较小的钻井和切割距离范围内。当距离较小时，喷管可能会受到反射射流的破坏。在狭窄的环境中，喷嘴有时不能设置得更靠近工件。因此，我们需要一些方法来延长水下AWSJ的有效工作距离。在这项研究中，提出了一种用于AWSJ的护套喷管，作为一种延长水下环境中有效工作距离的手段。在12 Mpa的喷射压力下，用不锈钢试件对这种带护套的AWSJ喷嘴喷出的射流进行了实验研究。发现鞘内的体积主要充满了水蒸气。有护套的AWSJ喷嘴有助于延长喷嘴和工件之间的有效工作距离，而不会显著降低钻井能力。一种能在气体环境中形成致密AWSJ的喷嘴适合作为水下环境中的护套喷嘴。在没有添加磨料的情况下，还进行了有护套喷嘴喷出的空化射流的观测和冲蚀试验。冲刷试验表明，冲击中心在护套出口下游区域受到强烈冲刷。射流独特的冲蚀特性为套筒喷嘴喷出的空化射流提供了潜在的应用前景。还提出了一种带通风的护套喷嘴，以进一步保持ASWJ在水下条件下的钻井和切割能力。

The drilling capability of abrasive water suspension jets (AWSJs) under a submerged condition decreases steeply with the increase of the standoff distance, and the effective working distance for drilling and cutting is restricted in a small standoff distance region. When the standoff distance is small, the nozzle may be damaged by the reflected jet. In narrow environments, the nozzle sometimes cannot be set closer to the work-piece. Accordingly, we need methods that extend the effective working distance for submerged AWSJs. In this research, a sheathed nozzle for AWSJs is proposed as a means of extending the effective working distance in submerged environments. Experiments are conducted to clarify the drilling capability of the jet issuing from this sheathed AWSJ nozzle using specimens of stainless steel at an injection pressure of 12 MPa. It is found that the volume in the sheath is predominantly filled with vapor. A sheathed AWSJ nozzle is useful for extending the effective working distance between the nozzle and the work-piece without a dramatic reduction in drilling capability. A nozzle which can make a compact AWSJ in gaseous environment is suitable as a sheathed nozzle in submerged environments. Observations and erosion tests of cavitating jets issuing from a sheathed nozzle are also conducted without addition of abrasive. The erosion tests show that the center of the impingement is eroded intensively in the region just downstream of the sheath exit. The singular erosive characteristics of the jet offer potential applications of the cavitating jet issuing from the sheathed nozzle. A sheathed nozzle with ventilation is also proposed to further preserve the drilling and cutting capability of ASWJs under a submerged condition.