Rock breaking performance of the newly proposed unsubmerged cavitating abrasive waterjet

Abstract

To improve the rock breaking ability, cavitating waterjet and abrasive waterjet are combined by using a coaxial low-speed waterjet generated around the periphery of a high-speed abrasive waterjet, and a new type of waterjet called unsubmerged cavitating abrasive waterjet (UCAWJ) is thus produced. The rock breaking performance of UCAWJ was compared with submerged cavitating abrasive waterjet (SCAWJ) and unsubmerged abrasive waterjet (UAWJ) by impinging sandstone specimens. Moreover, the effects of jet pressure, standoff distance, abrasive flow rate and concentration were studied by evaluating the specific energy consumption, and the area, depth, and mass loss of the eroded specimen. The results show that the artificially generated submerged environment in UCAWJ is able to enhance the rock breaking performance under the same operating parameters. Furthermore, the rock breaking performance of UCAWJ is much better at higher jet pressures and smaller standoff distances when compared with UAWJ. The greatest rock breaking ability of UCAWJ appears at jet pressure of 50 MPa and standoff distance of 32 mm, with the mass loss of sandstone increased by 370.6% and the energy dissipation decreased by 75.8%. In addition, under the experimental conditions the optimal abrasive flow rate and concentration are 76.5 mL/min and 3%, respectively.

Keywords

• Rock breaking
• Abrasive waterjet
• Unsubmerged cavitation
• Erosion
• Specific energy consumption