油滴与铝合金壁面的碰撞试验

机械零部件喷油或滴油润滑方式下油滴与零件表面碰撞后形成的沉积油膜流动特性决定着零件表面润滑油膜的分布特征和零件的润滑状态，对于这一润滑现象的深入理解需要对油滴与金属固体壁面碰撞及其后沉积油膜的流动铺展行为进行研究。建立了油滴与铝合金壁面碰撞的试验装置，采用高速相机拍摄了油滴与铝合金壁面碰撞及其后沉积油膜的流动铺展与形貌演化过程，分析了碰撞油滴的变形及沉积油膜的铺展与回缩历程，探讨了碰撞条件和润滑油黏度对沉积油膜流动铺展特性的影响。结果表明:与铝合金壁面碰撞后形成的沉积油膜铺展较快而回缩较为缓慢，没有明显的整体回缩现象和振荡过程。较小碰撞角度下，铺展初期油滴与壁面之间存在轻微滑移现象，受重力和铺展能量的作用，铺展后期油膜发生断裂并溅射离开壁面，但没有二次油滴生成。前铺展因子随着碰撞角度的减小和碰撞速度的增加而增大，后铺展因子则随着两者的增大而增大。油滴直径对前、后铺展因子的影响不太明显。 

Experiment of oil droplet impacting on aluminium alloy surface

The lubrication oil film on the surface of mechanical parts under spray or drip lubrication condition was influenced by the deposited film resulted from the impact of oil droplet with part surface.To understand the complex lubrication phenomena,it is necessary to study the impact behavior of oil droplet with metal solid substrate and the spreading process of deposited film.Therefore,an experimental apparatus was built to investigate the impact outcome of single oil droplet with aluminum alloy surface.High-speed photography was used to capture the oil droplet dynamical morphology and the spreading process of the subsequent film.The oil droplet deformation and the histories of spreading and recoiling of the film were analyzed qualitatively,and the effects of experimental condition and oil viscosity were discussed quantitatively.The experimental results showed that the deposited film spread outwards quickly, recoiled inwards very slowly, and reached eventually steady state.The whole film retraction and oscillation were not observed in the recoiling process.At lower impact angle,the slight slip between oil droplet and surface was found in the initial spreading stage, and due to the effects of gravity and spreading energy,finally,the film disintegrated without ejection of secondary oil droplets.The front spread factor increased with increasing impact velocity and decreasing impact angle,and the back spread factor increased with the increase of impact velocity and impact angle.The effect of oil droplet diameter on the front and back spread factors was insignificant.