Sheathed Abrasive Water Suspension Jet Nozzle for Submerged Application

磨料水悬浮射流在淹没条件下的钻削能力随着喷距的增大而急剧下降，有效钻削工作距离仅限于小喷距区域。当喷距较小时，喷嘴可能被反射射流损坏。在狭窄的环境中，喷嘴有时不能设置得更靠近工件。因此，我们需要延长水下AWSJ有效工作距离的方法。在这项研究中，提出了一种用于AWSJ的护套喷嘴，作为在淹没环境中延长有效工作距离的手段。在12 MPa的喷射压力下，使用不锈钢试样进行了实验，以澄清从这种护套AWSJ喷嘴发出的射流的钻孔能力。结果表明，在鞘层中的体积主要充满蒸汽。带护套的AWSJ喷嘴可用于延长喷嘴和工件之间的有效工作距离，而不会显著降低钻孔能力。一种能在气体环境中形成紧凑型AWSJ的喷管适合作为淹没环境中的护套喷管。在不加磨料的情况下，对套管喷嘴的空化射流进行了观察和冲蚀试验。冲蚀试验表明，冲击中心的冲蚀集中在鞘管出口的下游区域。射流独特的冲蚀特性为套管式喷嘴空化射流的应用提供了可能。还提出了一种带通风的护套喷嘴，以进一步保持ASWJ在浸没条件下的钻孔和切割能力。

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.