Study On Dynamic Characteristics Of The Beam Pumping Unit System

Rod pumping has a sizable proportion of mechanical oil production, the beam pumping unit is the most important ground part of rod pumping system. The dynamic characteristics prediction of the beam pumping unit is a basis for system's efficiency analysis and optimal design. In this thesis, the theoretical analysis and numerical calculation are deeply conducted for the beam pumping unit system. The main content is as follows:The kinematic analysis for the mechanism of the beam pumping unit is accomplished, displacement, velocity, acceleration of every component of the pumping unit are obtained in one motion period.Three order spline interpolation is applied to simulating sucker rod string axis. The problem of discontinuous interpolation caused by azimuth angle periodicity is solved.According to the D'Alembert's principle of particle system, a more accurate dynamic model for the beam pumping unit is established and system nonlinear dynamic equations are obtained taking joint friction into account. They are simplified into linear equations by using iterated method.Based upon the more accurate dynamic mode established in this thesis, the torque of crank and efficiency of rod pumping system are calculated. The model used in this paper is more close to reality by compared with the measured results. Influence on dynamic characteristics of the beam pumping unit by position of the counterbalance is analyzed and dynamic characteristics of the variant type beam pumping unit is also analyzed.Taking account of motor rotating speed fluctuations, a system equivalent mechanical model is established. High-degree coupling relation between the equivalent mechanical model and the model describing the vibration of sucker rod string is analyzed. The stepwise method is applied to solving this problem.