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中文核心期刊

微量润滑油滴冲击倾斜壁面黏附颗粒的实验研究

EXPERIMENTAL STUDY OF MICRO LUBRICATING OIL DROPLETS IMPACTING ADHERENT PARTICLES ON INCLINED WALL SURFACES

  • 摘要: 微量润滑油滴与金属壁面冲击黏附成膜过程中, 壁面附着颗粒物的存在对润滑油膜的形成质量和摩擦副的散热效果影响显著. 通过高速摄像实验对油滴与倾斜壁面黏附颗粒的冲击过程进行观测分析, 考察油滴冲击速度、壁面倾斜角度等因素对油滴冲击颗粒后的形态演变和铺展特性的影响, 以及黏附颗粒在冲击作用下的动态特性. 研究结果表明: 油滴冲击铺展过程中的形态演变受壁面倾斜角和冲击速度影响, 会出现不对称沉积铺展、单侧颈部射流破碎, 或者包裹颗粒滑移铺展等现象; 颗粒在油滴冲击作用下沿斜面方向未产生明显滑移时, 倾斜角增大对冲击油滴前铺展有促进作用, 更容易在前缘三相接触线附近产生单侧颈部射流破碎现象; 颗粒产生滑移时, 颗粒滑移速度随壁面倾斜角的增大而增大, 使前端液膜长度变短而抑制射流现象的生成, 产生微油滴包裹颗粒滑移铺展现象; 冲击速度对后铺展过程中的铺展因子变化影响较小, 前铺展过程中的最大铺展因子随着冲击速度的增加而逐渐增大; 壁面附着颗粒的运动受冲击速度和倾斜角大小影响明显, 冲击速度或倾斜角度的增大均能够促进冲击油滴包裹颗粒沿壁面滑动.

     

    Abstract: The presence of adherent particles on the metal wall during the impact adhesion process between trace lubricating oil droplets and the metal wall has a significant impact on the quality of lubricating oil film formation and the heat dissipation effect of the friction pair. The impact process of oil droplets and adherent particles on the inclined wall is observed and analyzed by high-speed camera experiments. The aim is to investigate the effects that oil droplet impact velocity, wall inclination angle and other factors have on the morphology evolution and spreading characteristics of oil droplets, as well as the dynamic characteristics of the adherent particles under the impact. The results reveal that the morphological evolution of oil droplets during impact spreading is jointly affected by factors such as wall inclination and impact velocity. Asymmetric spreading, unilateral neck jet fragmentation, or sliding spreading of wrapped particles may occur. When the particles don’t show significant slip along the inclined plane under the impact of oil droplets, an increase in the inclination angle promotes the spreading of the oil droplets forward, making it easier for a unilateral neck jet to break near the three-phase contact line at the leading edge. When particles slip, the slip velocity of particles increases with the increase of wall inclination angle, which shortens the length of the liquid film at the front end and suppresses the generation of jet phenomenon, resulting in the phenomenon of wrapped particles sliding and spreading. The impact speed has little effect on the variation of spreading factor during the post spreading process, while the maximum spreading factor during the pre-spreading process gradually increases with the increase of impact speed. The movement of particles attached to the wall is significantly affected by the impact velocity and inclination angle. An increase in the impact velocity or inclination angle can promote the sliding of particles wrapped in the impact oil droplets along the wall.

     

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