1916 Cavitating Jet Issuing from a Sheathed ASJ Nozzle

Abstract

An abrasive suspension jet (ASJ) has a greater capacity for drilling and cutting than a conventional abrasive injection jet (AIJ). However, the drilling capability of the ASJ under submerged condition decreases steeply with the increase of the standoff distance. In order to expand the effective standoff distance of the ASJ under submerged condition, a sheathed ASJ nozzle was proposed in the previous paper. In the present paper, observations of the jet issuing from the sheathed nozzle are observed without any abrasive. The injection pressure is set to 5 MPa and the cavitation number is in the range from 0.02 to 0.05. A sheath made of transparent acrylic resin pipe is used and flows in the sheath are observed with high-speed video camera. The results show that a cavity full of vapor is formed in the root part of the sheath. The jet expands fully out to the sheath inner diameter in the region near the sheath exit and a bubbly mixture zone is formed. A cavitation cloud extends from the bubbly mixture zone until to a certain distance of the sheath exit and then break lumps of cavitation bubbles. The bubbly mixture zone in the sheath fluctuates with time and its frequency depends on the cavitation number.