| Hydraulic percussion and rotary drilling is an advanced,efficient and economical drilling technology.Especially when used to drill hard and slipped bedrock,it can be regarded as a "sharp knife".In recent years,the rapid development of China's economy and widely construction of urban traffic roads,have led to accelerated consumption of resources.Hydraulic impactor has become a necessary tool in resource exploration,pile foundation and anchor downhole drilling which has produced enormous economic and social benefits.In order to improve the drilling efficiency in hard and slipped bedrock,a valve-type hydraulic impactor was designed,which could form differential circuit during percussion stage.The mud pump is paralleled with an accumulator to improve the impacting velocity and energy utilization rate.Water is used as the driving circulation medium,so the drilling cost is lower,and it is also environmental friendly.This water-powered impactor controls the flow distribution of the upper and lower cavity of the actuator by the reciprocating motion of the slide valve to control the motion of piston.At the same time,the piston moves to different location,and its lower bench controls the pressure of lower cavity of slide valve,so as to control the reciprocating movement of spool.To determine the structure dimension,dynamic characteristics and position feedback mechanism of the impactor,first of all,STAR-CCM+ is used to do the steady-state CFD analysis of the slide valve when the spool is at the upper and lower position to study the force of the piston.The dynamic simulation model of the slide valve is established with AMESim to study the dynamic characteristics and the switching time of the spool under different flow rate and different sizes.The orthogonal test analysis are done to determine the optimal combination parameters of the slide valve at the shortest switch time,and the priority of the influencing factors on the switch time of valve element.Besides,the system simulation model is established based on the working principle of the water-powered hammer,and the solver parameters are set depend on the identified structure size and location dimension.According to the analysis of the impact system,the change regulation of velocity and displacement with time of spool and piston could be determined,and change regulation of the cavity pressure and flow rate of slide valve and actuator with the position of the piston also could be obtained.At last,the quality of the piston,the amount of the pump,the diameter of the piston rod and the spacing between the F and E channels in the simulation model of the system are adjusted,to research the change regulations of impact velocity and impact frequency of the water-powered hammer.The spool can stabilize at the upper and lower point of slide valve based on the CFD analysis when the export pressure is 1Bar.According to the dynamic simulation analysis of the up and down switch of spool in certain range of parameters,the upper rod diameter of the spool has the greatest effect on the upward switch time of spool,and the mass of the spool has minimum effect on the upward switch time of spool.The spool stroke has the greatest effect on the downward switch time of spool,the upper spool diameter has minimum effect on the downward switch time of spool.Besides,the optimal combination parameters of slide valve under the shortest time slide have been determined.In addition,the change regulation of the upper and lower switch time of the slide valve is obtained with the change of the pump volume,the export pressure,the upper spool rod diameter,the spool mass,the diameter of the damping hole marked “g” and the spool stroke.The velocity,displacement of the piston and the pressure and flow rate change regulation of the control chamber was determined based on the dynamic simulation analysis of impact system.In addition,the change regulation of impact velocity,impact power,impact frequency and impact stroke with the flow rate,piston mass,upper-piston rod diameter and the spacing between E and F control channel has determined by adapting single factor analysis. |
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