Cavitation mechanisms in the front chamber of a dual-chamber-controlled hydraulic rock drill

Abstract

The coupling between the high-frequency reciprocating motion of the impact piston and the transient internal flow field in a hydraulic rock drill constitutes the dynamic origin of cavitation in the system. To reveal the mechanism of cavitation evolution in the front chamber, this study focused on a dual-chamber-controlled hydraulic rock drill and developed a fluid-structure coupling numerical model integrating fluid dynamics and rigid-body kinematics. Numerical simulations were conducted using PumpLinx software to obtain the spatiotemporal evolution of the internal flow field of the impactor during operation. Results show that cavitation initiates in the braking phase at the end of the return stroke and continues into the acceleration phase at the beginning of the forward stroke. During the braking phase, cavitation nuclei originate and develop at two critical locations: first, at the right corner of the undercut groove in the main oil passage, where a sudden flow cross-section reduction generates a high-speed jet, and the adverse pressure gradient induces flow separation and vortex structures, leading to intense bubble evolution in this region; second, at the bottom of the annular cavity near the guide sleeve, where opposing directions of the main flow and the replenishment flow result in insufficient oil supply, yielding relatively gradual cavitation development. Upon entering the initial forward-stroke acceleration phase, the reversed piston motion rapidly pressurizes the guide-sleeve annular cavity, where bubbles collapse quickly as pressure recovers. In contrast, downstream of the undercut groove corner, persistent vortex motion significantly delays bubble collapse.