Sheathed Abrasive Water Suspension Jet Nozzle for Submerged Application

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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.