A Study On The Longitudinal Vibration Characteristics Of The Injector Head’s Chain Drive System Under The Action Of Coiled-Tubing

The injector head is a critical piece of equipment in coiled-tubing(CT)operations,with the chain drive system serving as its core mechanism.The chain,which includes clamping blocks,is responsible for gripping the CT and pulling it in or out.During field operations,the injector head can experience various issues,such as CT surface damage,slipping,chain roller and sleeve fracture,sprocket wear,and abnormal sounds during operation.These engineering problems are closely tied to the vibration characteristics of the injector head’s chain drive system,which can significantly impact its performance and efficiency.Therefore,in order to reveal the law of action between the CT and the chain drive system,and improve the transmission efficiency and performance of the injector head’s chain drive system,the vibration characteristics of the chain drive system under the action of the CT are studied in this paper.The main research contents are discussed below.(1)The longitudinal vibration model of the injector head’s chain drive system without clamping CT was established based on the theory of multi-degree-of-freedom system.Newton’s second law was used to establish the longitudinal vibration equation of the system.The vibration characteristics of the system were solved using MATLAB software.The longitudinal tensile stiffness of the chain was simulated using Workbench software,and the modal analysis of the injector head’s chain system was conducted in its modal module.The results indicate that the natural frequency error of the theoretical calculation and simulation solution is less than 15%,and the mode pattern is consistent,thereby verifying the accuracy of the theoretical research.(2)The composition and working principle of injector head were introduced.The force on the clamping section of the injector head’s chain dirve system was analyzed,which provides a theoretical basis for the calculation of the whole longitudinal equivalent tensile stiffness of the chain and CT in the clamping section.By using finite element software,the equivalent longitudinal tensile stiffness of the whole chain-CT in the gripper section was simulated and solved.The longitudinal tensile stiffness of the chain,CT and chain-CT in the gripper section was compared and analyzed.The results show that the equivalent longitudinal tensile stiffness of the whole chain and the CT is greater than that of the CT itself and the chain itself.(3)Theoretical analysis was performed on the impact of meshing between rollers and sprockets,and the effects of factors such as the number of teeth on the sprocket,the angular velocity of the driving sprocket,and the contact stiffness on the meshing impact between rollers and sprockets were analyzed.The results show that increasing the number of sprocket teeth,decreasing the angular velocity of the driving sprocket and decreasing the contact stiffness will reduce the impact of meshing.The injector head chain drive system works in low speed and heavy load condition,and the meshing impact of the chain drive system is very small.(4)The polygon effect of chain drive was analyzed,the chain linear velocity and driven sprocket angular velocity were studied from the kinematic perspective,and the factors influencing the polygon effect of the tight edge chain of the injector were analyzed,including the driving torque,the number of sprocket teeth and sprocket angular velocity.The results show that the transmission stability of the system can be improved by reducing the driving torque,increasing the number of sprocket teeth and reducing the angular speed(or rotational speed)of the sprocket.(5)The chain gripping the CT segment was assumed to be a whole.Based on the theory of multi-degree-of-freedom system,the longitudinal vibration model of the injector head’s chain drive system under the action of CT was established.Newton’s second law was used to establish the longitudinal free vibration equation and forced vibration equation of the injector head’s chain drive system,respectively.The natural frequency,principal mode and system response were solved by MATLAB software.The effects of CT excitation amplitude,CT excitation frequency and initial conditions on the forced vibration response of the system were analyzed.The purpose of this study is to improve the transmission performance of the injector head’s chain drive system and make a theoretical analysis,which provides some guidance and scientific basis for improving the structural design of the injector head’s chain drive system and avoiding the resonance of the chain drive system.