The Simulation Research On The Flow Characteristics Of Gap Flow And Valve Gap Flow Of The Oil Well Pump

The oil well pump is an important part of sucker rod pumping system, the main reason of low efficiency of the sucker rod pumping system is the low efficiency of the oil pump. The reason for the low efficiency of the pump in addition to the stroke loss of the pump, the effect of the gas, the full extent of the pump, is the effect of the pump leakage. The leakage of the oil well pump is mainly divided into two parts, one part is the annular space leakage between the pump plunger and pump cylinder; another part is the valve gap leakage that caused by the valve ball retarded closing of the oil well pump. The article mainly dose one study on the gap flow between the plunger and the pump barrel of the oil well pump, the fluid through the fixed valve and the flow characteristics in the oil well pump. To analyze the influence of key factors on the gap leakage rate, and to explore the flow characteristics of the valve gap flow.The paper uses the combined method of theoretical analysis and numerical simulation based on Computational Fluid Dynamics theory, conducts the simulation research on the flow characteristics of the gap flow and the valve gap flow. The laws of the leakage caused by pressure difference and shearing motion between the plunger and the pump cylinder is analyzed theoretically, and a kind of gap seal structure with rectangular groove is presented,and the resistance mechanism of reducing the leakage is analyzed theoretically, through the theoretical calculation, the flow formula and the velocity distribution of the gap flow field among the concentric and eccentric parallel plate gap and annular gap are analyzed; A theoretical study on the process of the fluid intake the oil well pump is carried out, and an expression is established for the space volume that the fluid through the fixed valve and the valve seat, introduction the opening degree of the fixed valve related to the valve gap flow area and the area of the valve orifice to associate.The paper is based on the CFD technology, the numerical simulation is conducted between the gap flow and the valve gap flow of the oil well, and the calculation results are visualized, the influence of key factors on the leakage rate is analyzed, such as the length of stroke, the times of stroke, the gap width, the pressure difference and the eccentricity, and the flow resistance mechanism of the gap sealing structure with rectangular groove is revealed;The effect of different opening degree on the flow regularity of the valve gap flow is analyzed,the influence of fluid parameters and valve flow rate on the local resistance loss of the fluid under different fixed valve opening degree is established.The simulation results show that: The greater the times of stroke, the higher the average gap leakage rate; The longer the length of stroke, the more obvious rate of the average leakage growth; The average leakage rate increased with the increase of gap width, they do not show a linear relationship, but with the increase of the gap width, the average leakage rate curve shows the trend of accelerating growth; The average leakage rate increases with the increase of the pressure difference, and it shows a linear distribution; But the average leakage rate is more sensitive to the eccentricity, that is, the eccentricity ratio is a key factor affecting theleakage rate; The gap sealing structure with the rectangular balance slot plays a role of blocking effect to the fluid in the gap, the pressure is equal everywhere in the rectangular equilibrium groove. When the opening degree is certain, the loss of local resistance of the fluid over the valve increases with the increasing of the flow rate, viscosity and density; When the opening degree of the fixed valve is increased, the flow area of the fluid is increased, and the local resistance loss of the fluid over the fixed valve is reduced. This paper palys a role of enriching and developing for the improvement of the oil well pump leakage theoretical research, it provides a feasible theoretical basis for the improvement and selection of the oil well pump, the reasonable choice of the length of stroke, the times of stroke, the gap seal form.