Research On Lifting Mechanism And Performance Of Soft Plunger Pump

At present,many oil fields in China have entered the stage of tertiary production,and the asp flooding technology has been widely used as the most effective flooding technology in tertiary oil recovery.Although asp flooding can greatly improve oil recovery,it also leads to a large amount of scaling of oil well string,especially the phenomenon of stuck pump and even the rod breaking after scaling of conventional pump,which seriously affects the normal production of oil field.Aiming at this problem,a new type of soft plunger pump is developed in this paper.Non-metal material is used as the sealing material of plunger to avoid the scale-forming stuck pump of the pump.Starting from the lifting theory of the pump and referring to the structure and principle of the conventional pump,the working principle and structure of the soft-plunger pump are analyzed and designed.The hydraulic self-sealing soft plunger is used to replace the metal plunger in the conventional plunger pump,which increases the gap between the rubber barrel and the pump barrel and makes the gap leakage of the rubber barrel almost zero.In order to make the internal force of the soft plunger rubber barrel more uniform,the optimized design of the improved plunger skeleton structure was carried out by the finite element method.The results show that increasing the number of oil outlets as much as possible under the premise of ensuring safety can make the opening area of the plunger skeleton larger and the force of the soft plunger rubber barrel more uniform.The material of the rubber cylinder has a great influence on the performance of the rubber cylinder,mainly on the service life and performance of the new type of soft plunger pump.In this paper,the research object is NBR,which has the characteristics of fatigue resistance and low cost.The constitutive equation of NBR adopts Mooney Rivlin model.In the actual calculation process,the constitutive equation is set through the reserved interface of ANSYS Workbench.In this paper,two methods of experiment and numerical analysis are used to discuss the coefficient of the constitutive equation of NBR,which are verified by both methods The model constant of Mooney Rivlin model is determined by uniaxial tensile test,which provides necessary parameters for the finite element simulation of soft plunger rubber cylinder.The choice of rubber barrel material has a great influence on the performance and life of the new type of soft plunger pump.Mooney--Rivlin model was used as the constitutive model of the soft plunger rubber barrel.The model constants of the Mooney--Rivlin model were determined by uniaxial tensile test,which provided the necessary parameters for thefinite element simulation of the soft plunger rubber barrel.The finite element analysis of the soft plunger rubber barrel was carried out by the finite element simulation software.The two-dimensional and three-dimensional models of the soft plunger rubber barrel were established,and the deformation,equivalent stress and contact stress of the soft plunger rubber barrel were calculated and analyzed.The results showed that the two-dimensional simulation results of the soft plunger rubber barrel were very close to the three-dimensional simulation results.Based on the finite element analysis of the two-dimensional soft plunger rubber barrel model,the gap between the soft plunger and the pump barrel,the influence of the length,thickness and the included Angle of the shoulder on the sealing performance of the soft plunger pump was studied by calculating the contact stress,equivalent stress and displacement of the rubber barrel,and the design principle of the structural parameters of the soft plunger rubber barrel was proposed.The results showed that:the larger the gap,the greater the contact stress,but the more obvious the stress mutation caused by "shoulder process".The greater the contact length,the better the sealing effect;The greater the thickness,the greater the stress and strain;The greater the Angle of the shoulder,the greater the stress at both ends of the rubber barrel.The pump efficiency of the new type of soft plunger pump is calculated by theoretical method,and the main parameters that affect the pump efficiency are the filling coefficient and the stroke loss coefficient.At the same time,compared with conventional metal plunger pump pump efficiency under the same working condition,since there is no clearance leakage in the soft plunger pump,the pump efficiency can be improved by about 1.1% compared with the level 1 conventional metal plunger pump pump efficiency.