| Soft plunger pump is a new type of lifting device used in oil field.It has the characteristics of scale prevention,simple structure,convenient maintenance.And it has a good adaptability to the well condition using Alkaline-Surfactant-Polymer(ASP)flooding technology,which has been paid much attention by domestic and overseas oilfields.The short pump detection period of soft plunger pump exposed in the production is the bottleneck problem of restricting its area popularization and application.Therefore,it is of great significance to study the graded pressure characteristics of multistage soft plunger for pump and the structure design and parameter optimization of the soft plunger for prolonging the service life of the soft plunger pump and reducing the cost of crude oil production.The multistage soft plunger for pump was studied in this paper,and the uniaxial tension,uniaxial compression and compression relaxation tests of polyurethane and Polyether ether ketone(PEEK)specimens were carried out with the strain rates as the parameter.After evaluating the stress-strain through a variety of models,the Ogden(N=3)model with strong characterization ability was selected as the constitutive model of polyurethane.At the same time,the tension and compression deformation behaviors of PEEK specimens under different loading speeds were analyzed in the paper,and the flow characteristic precision of PEEK material was measured by using correlated coefficient index,and the JC model was determined to be the constitutive model of PEEK.In order to do the finite element analysis of the soft plunger of polyurethane,polyether ether ketone and nitrile butadiene rubber and to determine the experimental parameters of the wear characteristics of the soft plunger,we carry out the friction and wear simulation test of soft plunger and pump barrel.By analyzing the wear morphologies of different soft plunger materials through scanning electron microscope,it was determined that the major wear form of polyether ether ketone was fatigue wear and adhesive wearand polyurethane and nitrile butadiene rubber was fatigue wear and abrasive wear.By exploring the variation of friction coefficient,wear loss and wear rate with normal load and running speed,the polyether ether ketone with excellent comprehensive performance wasselected as soft plunger material.Two-way fluid-solid coupling method was used to construct the vertical ring gap flow model of multistage soft plunger and pump barrel,and the Lagrange-Euler description was used to describe fluid and solid interface displacement problem.The iterative way was used to solve the deformation and stress of soft plunger,and the graded pressure characteristics were concluded after exploring the multistage soft plunger for pump pressure distribution.Based on the fluid mechanics and the law of conservation of mass,the relevant factors(including length,thickness,initial clearance of the soft plunger-pump pair,pressure difference,etc.)affecting the leakage amount were analyzed,and their influence laws on the leakage amount were explored by combining theoretical analysis and numerical simulation.By using the optimization scheme of changing soft plunger length and outer diameter parameters,the structure design and parameter optimization method of multistage soft plunger pump was put forward.In this paper,a simulation test device of multistage soft plunger pump was developed,and the pressure distribution law of multistage soft plunger was revealed by testing the outlet pressure of the pump when grades were increased,so as to verify the correctness of the graded pressure characteristics by using the test results of prediction experiment model.The mass flow rate at the outlet of the pump was measured by weighing method,and the volumetric efficiency of multistage soft plunger pump was calculated under different structural parameters and operating parameters.The error range between the test volumetric efficiency and the numerical simulation volumetric efficiency was tested and the reliability of the calculation model and physical model of multistage soft plunger for pump was verified.By means of theoretical analysis and experimental research,the graded pressure characteristics of multistage soft plunger for pump was revealed in the paper and a theoretical and scientific basis for the popularization and application of multistage soft plunger pump was provided by the research results. |
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