双面回油型液压凿岩机空穴及气蚀机理

具有双面回油型冲击机构的液压凿岩机,其能量利用率高,但活塞回程制动阶段的前腔负压常常造成活塞和前导向套的严重气蚀,影响了凿岩机的正常使用。阐明了双面回油型冲击机构的工作原理,考虑油液压缩、油液泄漏和活塞的撞击回弹等因素,建立了冲击机构的数学模型,并进行数值仿真。通过凿岩机机理实验,测试了活塞前、后腔压力和冲击频率,得到了活塞的冲程末速度。比较实验与仿真结果,验证数学模型的正确性。在此基础上,通过仿真获得了阀芯与活塞的位移曲线和速度曲线,确定了阀芯开始换向、经历负开口区间以及换向完成的准确时间点。给出了活塞前、后腔和左、右阀腔的压力变化规律,揭示了前腔空穴的产生机理。为此设计并加装了回油蓄能器,分析了不同的充气压力对前腔空穴的影响。仿真结果表明,回油蓄能器能够在一定程度上改善前腔负压问题,且在0 MPa的充气压力下,效果最佳,负压的持续时间将减半。

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.