Positive Torque Modulation Method And Key Technology Of Beam Pumping Unit

The shortcomings of bad balance effect, low working efficiency and large energy consumption of the conventional beam pumping units are determined by its own structure. Large fluctuation and negative value of the torque on the reduction gearbox output shaft are the deciding factor. The number of conventional beam pumping units accounts for about eighty percent of all pumping units, these pumping units can’t be replaced all in a short period from the view of the resources utilization rate and economic cost. Therefore, it is the best choice to modulate the negative torque to the positive torque through reforming the conventional beam pumping units in a low cost. This research can effectively solves the problem of low efficiency, high energy consumption problem of the conventional beam pumping unit, otherwise, has the important practical significance for the oilfield development and the implementation of national energy-saving emission strategy to create a conservation society.The phased crank compound balance beam pumping unit CYJY10-4.2-53HF used most widely among the conventional beam pumping units was selected as the study object. On the basis of the fixed shaft twice balance principle of pumping unit, the positive torque modulation scheme of the conventional beam pumping unit was first suggested according to the following twice balance principle basing on the connection rod. The theory of plane kinematics of rigid body was employed for the derivation of the mathematical expressions of displacement, velocity, acceleration of the suspension center and angular velocity, angular acceleration of twice gearing-up mechanism. According to the motion characteristics of the reform pumping unit, the dynamics analysis of key motion components was carried out basing on the Darren Bell principle, the mathematical expression of the output shaft torque of gear box was derived out. An example of calculation showed that, the reduction gearbox output shaft torque can realize positive torque in the full cycle and the modulation scheme is feasible.The entity model of CYJY10-4.2-53HF positive torque beam pumping unit was established by using SolidWorks software. Time response rules of key parameters affecting twice balance result were systematically analysed by use of multi body dynamics analysis software ADAMS basing on the solid model. Simulation results of kinematics showed that the small crank rotated with non-uniform angular velocity, but the average angular velocity of the movement in the process was approximately double that of the big crank, so as to ensure the movement cycle could be repeated. Dynamic simulation results showed that the twice balance not only played the role of twice balance but also the first balance, different twice balance bias angle caused the variation of curve phase and amplitude,315° was better selection for twice balance bias angle. Torque synthesis curve on the gear box output shaft superimposed by the suspension center load, first balance load and twice balance load was derived from Simulation. The result showed that the twice balance torque curve could implement the role of ’cutting peak and filling valley’for the first balance torque to realize the goal of the full circle positive value for the reduction gearbox output shaft.The complex multidimensional nonlinear optimization method was adopted in the mathematical model of balances matching optimization. The RMS torque on the reduction gearbox output shaft representing energy consumption of pumping units was established as objective function. The barycenter position of first balance and the barycenter position, bias angle and mass of twice balance were set up as design variables. The balance matching optimization design for positive torque beam pumping unit was programmed with MATLAB software. The optimization results by example showed that the bias angle of twice balance was 313.56°, the optimized maximum value of the gear output shaft torque became smaller, the minimum value became larger, fluctuation rate reduced significantly, the RMS torque decreased from 20730.89N.m to 20382.07N.m, the optimization effect was obvious.The bearing capacity for the key components of twice speed-increasing mechanism was studied by using of ADAMS and SolidWorks joint simulation transforming the dynamic problem into static problem. The following conclusion was drawed:the connecting rod-increasing reduction gearbox beared the positive and negative reciprocating alternating bending moment because of the exist of twice balance, the original connection mode of I-beam could not meet the using life requirements. A new structure of connecting rod was designed, the simulation results showed that the new structure could meet the requirements of safety coefficient. The small gear shaft was under the action of the positive and negative reciprocating alternating torque, the end surface of spline connected with the small gear was the maximum stress position, the small gear structure of 40Cr could meet the safety requirements. The big gear shaft under the combined action of bending moment and torsion in large, the maximum stress position was on the surface of escape closing to the side connecting with the big crank in the axial direction and closed to the spline surface applied loads in the circumferential direction. The large gear structure of 35CrMo could meet the requirements of the minimum safety factor.The prototype of renovation part of positive torque beam pumping unit was developed and indoor and field test was completed. The test results showed that the positive torque beam pumping unit could realize positive torque entirely in the field working condition. The power saving rate reached up to 23.73%, the system efficiency was improved by 14.5%, the pumping unit reliability could meet the field application requirements.