Study On Surface Texturing Flow Field Characteristics And Anti-friction Performance Of Screw Pumped NBR

Stator and rotor in the screw pump as an important mechanical component.In view of the current high water content and high sand content of oilfield production fluids,the friction and wear of the stator and rotor under high water content and sand content are aggravated,resulting in leakage,sand jams,short service life and low work efficiency.This thesis studies the friction properties of the stator rubber components of screw pumps.It is proposed to prepare surface textures on the stator rubber surface to improve its friction characteristics,so as to achieve the purpose of reducing friction,prolonging service life and improving work efficiency.First,in order to explore the surface texture range that can reduce friction on the surface of NBR,42 Cr Mo alloy steel thrust ring and NBR test ring surface contact sliding friction pair were selected as the experimental friction pair,the effects of these two surface textures on friction properties were investigated by comparing the micron texture and millimeter texture.Studies have shown that the micron texture can reduce friction on the surface of NBR.Based on this research conclusion,continue to explore the influence and mechanism of different geometric shapes,sizes and operating parameters on the tribological properties of micron texture.Using CFD method,the fluid domain models of non-textured,circular pit surface texture,spherical pit surface texture and V-shaped pit surface texture were established respectively.Under water lubrication,the internal flow field characteristics of surface texture with different shapes were explored,and its velocity distribution,pressure distribution and streamline distribution were analyzed,the results show that the geometry shape has a direct effect on the tribological characteristics of the friction pair,and the surface textures of the three shapes all improved the fluid loading capacity,but the circular pit surface texture had the strongest hydrodynamic pressure effect.On the basis of the circular pit surface texture,the effects of texture diameter,depth and Reynolds number on the internal flow field performance and dynamic pressure loading capacity of the surface texture was continued,and the vortex phenomenon in the internal flow field was analyzed,the results showed that when the Reynolds number and depth were large,the vortex phenomenon occured in the internal flow field of the surface texture,and the vortex region occupied the bottom of the pit,which increases as the Reynolds number increases.On the other hand,combined with the vortex phenomenon,the internal flow field characteristics of surface texture and the loading capacity of lubricating film can be analyzed and explained,which provided theoretical support for the design of surface texture of NBR.According to the complex lubrication conditions such as water lubrication,oil lubrication and oil-water mixed lubrication of the stator and rotor under actual working conditions,different circular pit surface texture diameter,depth and area density under water lubrication,oil lubrication and 1:1 oil-water lubrication conditions and different loads were carried out.The tribological properties and influence rules under different conditions are discussed in detail,and the friction coefficient,wear amount and surface wear of textured NBR surface were evaluated compared with that of non-textured texture,and the rationality of theoretical calculation model was verified,the results show that the lubrication conditions have a significant effect on the tribological properties of the NBR textured surface,and the textured surfaces with the same geometric parameters exhibit completely different friction properties under the three fluid lubrication conditions;Under the same fluid lubrication conditions the friction coefficient of NBR surface is changed in a certain range under different loads;Under the three lubrication conditions,the smaller loads,the more significant the anti-friction effect,and the larger loads,the worse the anti-friction effect;The surface texture of NBR under water lubrication is the most significant.When the load is 20 N,50N,100 N,and150N,the maximum friction reduction rate can reach 61.7%,47.2%,24.2%,and 24.3%,respectively.The effectiveness of the theory and design method of surface texture of NBR is verified by experiments,which can effectively improve the friction characteristics of stator and rotor friction pairs.