Research And Analysis Of Rotary Percussive Drilling Tool Based On Positive Displacement Motor

In order to improve the penetration rate,solve the difficult problem of deep well drilling and reduce the drilling cost,a new type of mechanical axial rotary percussion drilling tool based on positive displacement motor tool is designed.It can be divided into bypass valve assembly,motor drive assembly,transmission shaft assembly and impact hammer assembly from top to bottom.The working principle of the tool is introduced,and the parts of the tool are designed in detail.According to the mechanical characteristics of the device,the static strength and fatigue strength of the flexible shaft are checked.The strength of the upper shaft,the bearing housing and the stator housing under different working conditions,such as vertical and inclined wells,drilling and non-drilling,is verified by ANSYS.The strength of the roller base under drilling condition is qualified.The rotary percussion drilling tools can meet the application requirements.In this paper,ANSYS is used to study the load distribution of each steel ball in the same stage of thrust bearing,which provides a basis for simplifying the model.Then the influence of the axial load on the bearing is analyzed.The stress distribution of the inner ring,the steel ball and the outer ring is obtained.The influence of the diameter of the steel ball on the bearing capacity is studied.It is determined that the diameter of the steel ball should be considered first as 26 mm.In order to make the bearing have a higher life,the upper seal group and the lower seal group are designed to seal the mud.Considering the actual processing conditions,the O-ring can meet the sealing requirements of 70 MPa at the condition of maximum and minimum compression rates calculated by ANSYS.The seal packing can meet the sealing requirements of 70 MPa at the condition of maximum and minimum clearance states.The force analysis of cam mechanism is carried out,and the calculation formulas of bit output force are deduced based on the mechanics of pipe string.The equation of displacement,velocity and acceleration of five-order polynomial motion law,cosine acceleration motion law,cycloid-linear-cycloid motion law and improved sinusoidal acceleration motion law are written respectively.Based on the above motion law,the relationship diagrams of roller axial displacement-cam rotation angle,roller axial velocity-cam rotation angle,roller axial acceleration-cam rotation angle are drawn when the rotation speed of the cam is 120r/min.Under the condition that the initial drilling pressure is 100 k N and the output torque of screw drill tool is 8000 N m,the output force of the bit and the consumption of the torque in one impact cycle are calculated.Through comparison,it is finally decided that the cosine acceleration motion law should be chosen in the push section and the cosine acceleration motion law should also be used in the return section.The dynamic simulation of cam mechanism is carried out by ADAMS.The simulation results are in good agreement with the theoretical calculation results.