Experimental study on rock breaking parameters of dual-jet

Key words:  swirling jet  nozzle  dual-jet  rock breaking  drilling  experimental study

Abstract:

Dual-jet is a new kind of high efficient jet, which is formed by combining round straight jet with circular conical swirling jet. And the dual-jet can overcome the limits of high threshold pressure and high rock breaking energy. The effects of parameters including nozzle cone angle, swirling path angle, nozzle diameter, sandoff distance and pressure on rock breaking efficiency of dual-jet were researched by rock breaking experiment. The results show that the dual-jet nozzle with a cone angle of 60° and a swirling path angle of 18° can produce the largest rock breaking volume. And while keeping the equivalent nozzle diameter, the nozzle with larger internal nozzle diameter can produce larger breaking depth and smaller cutting volume. The optimal sandoff distance ranges from 10 to 20 mm, and the optimal threshold pressure ranges from 20 to 25 MPa. The cutting volume increases with the jet pressure increasing.