摘要
油-气润滑过程中润滑油液滴受高速气流扰动易形成含气泡油滴,微气泡将对油滴撞击壁面时的运动过程以及壁面油膜层的形成质量产生重要影响.基于耦合的水平集-体积分数方法,对含气泡油滴撞击油膜壁面行为进行数值模拟研究,考察含气泡油滴撞击油膜壁面时气泡的变形运动过程,探讨气泡破裂的动力学机制,分析气泡大小、碰撞速度和液体黏度等因素对含气泡油滴撞壁过程中气泡变形特征参数的影响规律.研究表明:含气泡油滴撞击油膜壁面后气泡会发生变形,并破裂形成膜液滴;气泡随同液滴运动过程中,气泡内外压力和速度梯度变化是使气泡发生破裂的主要诱因.气泡大小对气泡破裂方式影响较大,气泡较小时发生单点破裂,而气泡较大时更容易发生多处破裂.不同大小气泡受力差异较大,气泡大小与破裂发生时刻没有明显相关性.碰撞速度和液体黏度对气泡的变形、破裂和破裂发生时刻都具有一定的影响.碰撞速度越大,油滴动能越大,更容易产生气泡变形和破裂现象.液体黏度增大,在油滴撞壁运动前期促进气泡变形,而在运动后期可以阻延气泡破裂行为发生.
Hollow oil droplets are easily formed by the high velocity air turbulence in the process of oil-gas lubrication.The micro bubble has an important influence on the movement process and oil film formation quality when an oil droplet impacting on the wall.The coupled level set and volume of fluid(CLSVOF)method is adopted to simulate the impact of a hollow droplet on the oil film wall.The dynamic mechanism of bubble rupture is investigated by investigating the deformation and movement of bubbles when the hollow droplets are impacted on the wall of the oil film.And the influence of bubble size,collision velocity and liquid viscosity on the characteristic parameters of bubble deformation in the process ofbubble wall collision is also analyzed.The results reveal that the bubbles will deform and break up to form film droplet after the hollow droplets impact the wall of the oil film.The change of pressure and velocity gradient inside and outside the bubble is the main cause of bubble rupture.The bubble size has a great influence on the bubble rupture mode,single-point rupture occurs when the bubble is small,larger bubbles are more likely to cause multiple ruptures.The difference of force between different sizes ofbubbles is larger,and there is no obvious correlation between the size of the bubble and the moment of rupture.The velocity of the collision and the viscosity of the liquid have a certain influence on the deformation,rupture and rupture time of the bubble.The larger the collision velocity,the greater the kinetic energy of the oils droplet,and the more likely the bubble deformation and rupture.When the viscosity of the liquid increases,the bubble deformation is promoted at the early stage of the movement of the oil droplet,and the rupture behavior of the bubble can be delayed in the later period of the movement.
作者
周剑宏
童宝宏
王伟
苏家磊
Zhou Jianhong;Tong Baohong;Wang Wei;Su Jialei(School of Mechanical Engineering,Anhui University of Technology,Maanshan 243032,Anhui,China;Institute of Tribology,Hefei University of Technology,Heifei 230009,China)
出处
《力学学报》
EI
CSCD
北大核心
2018年第2期427-437,共11页
Chinese Journal of Theoretical and Applied Mechanics
基金
国家自然科学基金(51475135)
清华大学摩擦学国家重点实验室开放基金(SKLTKF17B01)
安徽工业大学研究生创新基金(2015040)资助项目
关键词
油滴
气泡
油膜壁面
气泡破裂
数值模拟
droplet
bubble
oil film
bubblerupture
numericalsimulation
