Cavitation mechanism for hydraulic rock drill with no constant-pressurized chamber

The hydraulic rock drill with no constant-pressurized chamber impact mechanism has an advantage of high energy utilization.However, the ante-chamber's cavitation may lead to the erosion of its piston and front bush.It can severely impact the rock drill's normal operation.In this study, the operating principle of the impact mechanism was introduced.Considering the compressibility and the leakage of hydraulic oil and piston's springback, a mathematical model was built.Then the numerical simulations were performed.The mechanism experiment was conducted, therefore, the pressure curves of the piston chamber and impact frequency of the rock drill were obtained.The velocity of the piston was worked out by the testing data.The simulation model's validity was verified by comparing the experimental and simulation results.The time when the valve began to reverse, pass through the overlapped interval and complete the reverse could be confirmed by analyzing the displacement and velocity curves of the piston and valve.The cavitation mechanism of the ante-chamber of the piston was studied via the pressure curves of the chamber, the velocity and displacement curves of the piston and spool.The accumulator for the return oil was installed.The influence on the ante-chamber cavitation of accumulator's pre-charge pressure was researched.Simulation results demonstrated that the accumulator for the return oil could improve the problem to some degree.The time of the cavitation would be reduced in half while the pre-charge pressure was 0 MPa.