Research On Rack Pumping Unit With Small Tooth Difference Gear Reducer

As the exploitation of low permeability oil and gas fields has been paid more and more attention,it is difficult for conventional beam pumping unit equipped with two-stage reducer to realize low stroke exploitation.Aiming at the mining requirements of low stroke,this paper proposes a rack pumping unit with less tooth difference gear reducer,and puts forward three design schemes for the pumping unit.After comparing and analyzing the advantages and disadvantages of the three schemes,The paper determines the best scheme and the whole machine structure of the rack pumping unit with less tooth difference gear reducer,and then designs and analyzes the selected best scheme.The main work of the paper includes the following four parts:（1）The optimal design scheme of rack pumping unit with less tooth difference gear reducer is determined to be ring-rack pumping unit.A suspension point motion model of the ring-rack pumping unit is established and the motion characteristics and influencing factors of the ring-rack pumping unit are analyzed.Then,the digital virtual prototype of ring rack pumping unit is established in Adams software to simulate and verify the motion characteristics of the pumping unit.The results show that the ring-rack pumping unit runs smoothly in up-and-down stroke,and the speed changes only when starting and reversing.（2）Optimize the parameters of the reversing mechanism of the ring-rack pumping unit with the objective function of minimizing the maximum acceleration of the suspension point.The optimization results show that the maximum acceleration of the pumping unit before optimization is 0.043m/s²,and the acceleration decreases to0.033m/s² after optimization,which is 23.3%lower than that before optimization.so that the impact of the pumping unit during reversing is reduced.The time of uniform movement of pumping unit is reduced from 44.1s to 38.9s,which decreases by 11.8%.（3）Design a special high transmission ratio reducer for the pumping unit with a transmission ratio of 125,so that the pumping unit can achieve a minimum stroke of1min^-1,meeting the mining needs of low permeability oil wells.Optimize the gear pair parameters of the reducer,and the transmission efficiency of the optimized reducer is increased by about 3.3%,while the volume is reduced by about 9.1%.The transmission efficiency of the rack pumping unit equipped with a gear reducer with less tooth difference is about 13.4%higher than that of the conventional beam pumping unit.By establishing a virtual prototype simulation of the reducer.The simulation results indicate that an error of 0.58%was obtained between the actual transmission ratio and the theoretical transmission ratio,verifying the rationality of the reducer structure.（4）Theoretical strength calculation and finite element simulation were conducted on the key components of the ring-rack pumping unit.The results show that the maximum contact stress and bending stress at the contact point between gear and rack are 379MPa and 169MPa.The error is small compared with the theoretical calculation results,and the strength requirements are met.The theoretical and simulated bending fatigue strength of internal meshing gear pair in gear reducer with small tooth difference is less than the allowable bending stress,which meets the strength requirements.The modal analysis results show that there is no resonance between the box and the internal gear drive.In summary,rack pumping units with small tooth difference gear reducers have the advantages of stable motion performance and simple structure,and have broad prospects for promotion in low-permeability oil well exploitation.