Structural Design And Dynamics Research Of High Wind Pressure Valveless Impactor

In recent years,due to the rapid development of human society,the consumption of mineral resources has increased day by day.Most of the open and shallow mines in shallow areas and easily accessible areas have been exhausted.The exploration and mining of mineral resources have gradually shifted to the development of deep mines and complex strata mines.Facing the new trend of mineral resources exploration and mining,the traditional drilling technology cannot meet the current technical requirements of mineral resources exploration and mining.Pneumatic impactors are highly valued by the domestic and foreign drilling industry for their advantages of high drilling efficiency,high hole-forming quality,low drilling weight and rotation speed required,clean slag discharge,long bit life and no environmental pollution.The pneumatic impactors used in the field showed unique advantages,but also exposed the deficiencies of low rig utilization rate,severe piston fracture and high drilling cost.In order to solve the shortcomings of the pneumatic impactor used in the field,a new type of high-pressure valveless impactor was studied.The main research contents and conclusions are as follows:(1)Scheme design of high wind pressure valveless pneumatic impactor:Refer to the pneumatic manual and the structural characteristics of the pneumatic impactor of the same size,combined with the application location and operation mode of the high wind pressure valveless impactor,complete the parameter design of the high wind pressure valveless impactor,thus establishing the main parts structure,This clarifies the overall structure of the tool.(2)Piston motion mathematical model establishment:According to the structural parameters and working principle of the designed high wind pressure valveless impactor,the piston return stroke and stroke movement are divided into five stages to describe the different states of the gas in each chamber during the entire movement of the piston.Combined with the gas flow theory,the equations of motion of the parallel pistons,the gas state equation of the gas chamber and the orifice flow equation,a mathematical model of nonlinear dynamics of the piston is established.(3)Research on the structure of the piston transition section:In order to reduce the fatigue failure phenomenon of the piston and extend the service life of the piston,the failure problem of the piston transition section often occurs.According to the collision characteristics and material properties of the piston and the drill head,a simulation model of the collision between the piston and the drill head is established,and the dynamic method of finite element display is used.The finite element analysis software Ansys conducts a dynamic simulation study on the piston impact drill head.The common connection types of the piston transition section are obtained:the influence of the structural parameters of the circular connection,the linear connection and the circular and linear connection on the safety factor,maximum stress and maximum strain of the piston transition section.The final study found that the connection structure type with an arc radius of 4mm and a diagonal angle of 11° is the optimal structure for an eight-inch impactor.The research content provides a method and design basis for the optimization of the piston structure.(4)Optimization of key parts structure:In order to get better working performance,on the basis of the existing structural dimensions,the relevant structural dimensions of the cylinder and piston rear end are optimized respectively.Under the two working conditions of minimum working wind pressure of 1MPa and maximum working wind pressure of 2.5MPa,the relevant performance structure size of the cylinder is studied through the performance calculation mathematical model.The final study found that when the working wind pressure is 1MPa,the cylinder structure is changed to make the rear air chamber intake length 7mm,the cylinder structure size is optimal;when the working wind pressure is 2.5MPa,the cylinder structure is changed to make the rear air chamber intake length 13 mm,The cylinder structure size is optimal.Similarly,the single-factor sensitivity analysis method is used to study the relevant structural dimensions of the rear end of the piston,and the impact law of impact energy,frequency and gas consumption under different structural dimensions is obtained through the performance calculation mathematical model.Then use multi-objective optimization method,with impact energy,frequency and gas consumption as the optimization goals,optimize the analysis of the relevant structure size of the rear end of the piston.The final optimized structure has an impact energy increase of 8.26% compared with the original structure.The gas volume changes slightly.The research content provides a theoretical basis for the structural design and optimization of the high wind pressure valveless impactor,and provides a reference for the design and optimization of other tools of the same type.