Study On Multifield Coupling Characteristics Of Single Screw Pump For Oil Gas Mixed Transportation

As one of the five major modes of transportation pipeline transportation equipment,the single screw pump for oil and gas mixed transportation is widely used in the development of gas bearing,sand bearing and heavy oil wells in oil fields due to its structural characteristics.It is an efficient,green and energy-saving positive displacement artificial lift equipment.The research on the improvement of the performance and structural parameters of the single screw pump is of great significance for improving its oil transportation efficiency and reducing its transportation and investment costs.In previous studies on single screw pump of oil-gas multiphase transmission equipment,the influence of multi field coupling effect was seldom considered,and the boundary conditions were deviated from the reality.This study took GLB120-27 single screw pump of oil-gas multiphase transmission equipment as the research object,taking into account the influence of fluid structure thermal coupling effect,mainly based on the numerical simulation method,analyzed its multi field coupling performance under pure liquid condition and the flow field The temperature field and deformation characteristics have determined the optimal clearance fit value of the stator and rotor under the most unfavorable working conditions.The main research work and innovative achievements are as follows:(1)A rotor planetary motion program was written in the fluid domain,and the user defined function(UDF)in FLUENT was used to load the boundaries of the rotor.A dynamic mesh model was used to simulate the dynamic changes of the fluid domain with the rotation of the rotor,in order to achieve its planetary motion.It was found that the gas content has a significant impact on the distribution of temperature difference between the inlet and outlet of the fluid medium,leakage flow rate,and volumetric efficiency.Especially when the gas content is above 80%,the temperature difference between the inlet and outlet of the fluid medium and the leakage flow rate increase sharply,and the volumetric efficiency of the pump decreases sharply.(2)Using the viscoelastic hysteresis heat generation of the stator as an internal heat source,a corresponding ANSYS user subroutine was written using APDL language to extract the average node heat generation rate on the stator surface.The fluid solid thermal coupling calculation of screw pump was carried out by using ANSYS Workbench finite element analysis software.The results indicate that the stator deformation calculated through fluid solid thermal coupling under pure liquid operating conditions is caused by compression and gradually increases from inlet to outlet.(3)The influence of different void fraction on temperature,pressure,deformation,leakage and volumetric efficiency of screw pump was studied by using the fluid thermal solid coupling method.Research has found that when the gas content is below 87%,the lagging heat generation of the viscoelastic rubber stator is the main heat source causing the temperature rise of the pump liner.When the air content exceeds 80%,the comprehensive temperature rise of the rubber stator increases sharply under the influence of multiple fields.The comprehensive deformation value of the rotor gradually increases with the increase of gas content.The comprehensive deformation value of the stator gradually decreases and then sharply increases with the increase of air content.(4)In order to improve the volumetric efficiency of screw pump and prevent the stator from being stuck due to large deformation,based on the results of multi field coupling calculation,an optimization scheme for the clearance fit between the stator and the rotor is given,and the calculation results of pure liquid working condition are verified through the volumetric efficiency experiment.The average deviation is less than 7%,indicating that the calculation scheme used in this study for fluid solid thermal multi field coupling has high accuracy and reliability.The research results provide theoretical basis and project reference for the optimal design of structural parameters of oil transfer screw pump and how to ensure the normal operation of oil transfer screw pump under high gas content.