With the increase of oilfield exploitation depth, the weight of beam pumping unit rod pipe increases, and the inertial force increases, which seriously affects oilfield production efficiency.

Rodless reciprocating pump with submersible motor has fewer power conversion links and lower energy consumption

low and high system efficiency.

However, due to processing and assembly errors, there may be taper and eccentricity in the sealing section between the long plunger and the pump barrel of the reciprocating pump.

Under the action of high-pressure oil, the plunger will be affected by radial unbalanced hydraulic pressure, resulting in eccentric wear.

As a result, the leakage of the well pump increases and the volumetric efficiency decreases.

Deng Kang analyzed the relationship between gap flow and hydraulic clamping, studied the factors that hinder the movement between the valve core and valve seat in the hydraulic transmission system, and obtained the hydraulic clamping force calculation formula.

Experimental results show that applying axial or circumferential high-frequency and small-amplitude vibrations to the plunger sleeve can also reduce and eliminate hydraulic stagnation.

However, the application of the measures to reduce the clamping force to the oil well pump production system will cause

Production costs are high. Chen Hui and others analyzed how to improve the working efficiency of reciprocating pumps, and believed that the key lies in reducing the gap between the plunger and the pump barrel and reducing the eccentricity, but the processing accuracy is very high, including dimensional accuracy and shape accuracy, which is difficult to achieve in engineering .

Zhu Jing proposed to adopt methods such as long plunger, short pump barrel and installation of sand filter under the pump in order to improve the eccentric wear problem of the oil well pump. The test results show that this structure can only alleviate the problem of eccentric wear of the plunger, but the problem of eccentric wear still exists.

Considering that the theoretical calculation is very complicated, this paper adopts computational fluid dynamics (CFD) simulation method to simulate the radial force on the plunger surface under different eccentric states and different tapers, and obtain the influence on the radial force.

At the same time, the pressure equalizing groove structure is adopted to reduce the radial unbalanced hydraulic pressure of the plunger, which can avoid the eccentric wear of the plunger and the pump cylinder, and prolong the service life of the reciprocating pump.

The linear motor drives the plunger to reciprocate up and down.

During the upward movement of the plunger, the volume of the upper pump chamber decreases and the internal pressure increases.

After the crude oil is pressurized, the oil outlet valve opens under the action of the upper and lower pressure difference, and the oil passes through The valve port is discharged, and part of the oil flows to the ground along the oil pipe.

At the same time, the volume of the lower pump chamber increases and the pressure decreases. pump cavity.

During the downward movement of the plunger, the one-way valve located upstream of the plunger is closed under the action of high-pressure oil, the volume of the upper pump chamber increases and the pressure decreases, the one-way valve located on the plunger opens, and the oil passes through the inlet.

The oil screen, plunger chamber, and one-way valve enter the upper pump chamber to realize the oil absorption process. At the same time, the volume of the lower pump chamber decreases and the pressure increases.

The oil in the lower pump chamber is discharged to the oil pipe through the inlet of the lower pump chamber. connected to the sand settling pipe, and then discharged to the ground through the oil pipe face. In one reciprocating stroke, the double-acting oil well pump sucks oil and discharges oil twice.

When the plunger and the pump barrel are assembled concentrically, the radial forces generated by the high-pressure oil are symmetrically distributed and offset each other, and there will be no radial unbalanced force.

Under the same structural parameters and working pressure, the flow field fluid is laminar , the radial unbalanced force obtained by simulation is 5.3 N, which is too small to be ignored.

When the plunger has no taper and the assembly eccentricity is 0.05 mm, it can be seen from the above simulation results that when the plunger has eccentricity and no taper, the axial pressure change of the flow field has a linear relationship with the position, and the circumferential

The pressure distribution is uniform, the radial unbalanced force is small, and the problem of eccentric wear is not obvious. The change along the axial direction shows a nonlinear relationship, and the pressure gradually decreases from the large end to the small end of the plunger.

(1) There are two main factors affecting the eccentric wear force between the plunger pump barrels: the eccentricity of the plunger pump barrel and the taper of the plunger. The larger the eccentricity, the larger the taper, and the more serious the eccentric wear of the plunger.

(2) The depth and stroke times of the submersible reciprocating pump will also affect the radial eccentric wear force on the plunger. The greater the pressure difference between the two ends of the plunger and the movement speed of the plunger, the greater the eccentric wear force.

(3) The pressure equalizing grooves on the plunger will affect the eccentric wear force on the plunger. Secondly, the number of pressure equalizing grooves will also affect the magnitude of the eccentric wear force, but the more the number of pressure equalizing grooves, the more stable the eccentric wear force.

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