Research On Motion And Meshing Dynamic Characteristics Of Single Screw Drill

The screw drill is a kind of downhole dynamic drilling tool,and now it has been widely used in oil field drilling engineering.The screw motor consisting of the stator and the rotor is the core component of the screw drill,the drilling fluid moves the rotor through the seal cavity between the stator and the rotor,and transfers the power to the drill to complete the drilling during working.Because of the special structure of the screw drill tool and the complicated working environment,the failure forms such as the wear of the stator bushing and the leakage of the drilling tools are caused.Therefore,it is necessary to study the drilling tool line and the meshing force of stator and rotor.In this paper,a wall thickness screw drilling tool with an outer diameter of 172 mm is used as the object,the following research has been carried out.Firstly,the B spline curve fitting algorithm is applied to the design of the profile curve of screw drill,and the profile curve of the rotor is obtained,the curvature of the curve is obtained by the reduced order method,thus the tip points of the concave and convex transition can be found.Combining the profile and data characteristics of the cross section,a genetic algorithm which takes the change amount of the coordinate value of the control point as the optimal variable is proposed.Through this method,the cross section profile of the screw drill can be optimized,the feasibility and effectiveness of the proposed algorithm are verified by the change of the length of the meshing line.Secondly,the paper analyzes the motion mechanism of the screw drilling tool rotor,building the solid model of screw drill tool by three-dimensional software and check the static and dynamic interference of the drill tool.Then,the paper study the motion law of screw drill rotors in bushing,the trajectories and variations of the velocity and acceleration are obtained from the selected points on the rotor section.The calculation formula of the relative sliding velocity between the stator and the rotor is derived and the change of the relative sliding velocity is studied by the simulation experiment.Finally,the paper analyzes the mechanical characteristics of the screw drilling tool during work combine the mechanical principle and the contact situation.Deformation law of the rotor in the sealing cavity of the screw drilling tool under the action of pressure is studied.The paper establishes the contact mechanics model between the stator bushing and the rotor and then uses finite element software to achieve the analysis of stress and strain of rotor and thick stator bushing under uniform pressure.After that,the mechanical characteristics of the screw drilling tool rotor and the stator are studied under the actual working conditions,the position of stress concentration can be found,it provides a theoretical basis for the structural optimization of screw drill tools.In this paper,the optimization of the profile of the rotor and the mechanical characteristics of the meshing of the rotor and the stator are analyzed,the purpose is to reduce the leakage and wear of the drilling tools,and to improve the service life of the drilling tools.