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油滴与高温固体壁面碰撞的动态铺展与传热

陈薄1,贾飞2,马兴裕1   

  1. 1. 西南科技大学
    2. 哈尔滨工业大学
  • 收稿日期:2022-11-24 修回日期:2023-02-15 出版日期:2023-02-17 发布日期:2023-02-17
  • 通讯作者: 陈薄
  • 基金资助:
    “空气/油滴/油膜”共存状态下轴承腔润滑与换热及模化方法研究

Dynamic spreading and heat transfer of oil droplet impacting on a heated wall

  • Received:2022-11-24 Revised:2023-02-15 Online:2023-02-17 Published:2023-02-17
  • Contact: Bo CHEN

摘要: 机械零部件的喷油和滴油润滑方式下,油滴与零件表面碰撞后形成的附着油膜的流动与传热特性极大的影响着零件的润滑与散热状态。考虑油滴热力学特征参数受温度影响,采用VOF(Volume of fluid)方法建立了油滴与高温固体壁面碰撞的流动与传热三维数值分析模型,分析了油滴与高温固体壁面碰撞后的形貌演化与油膜/壁面间的热量传递等动力学和热力学行为,通过试验验证了数值分析模型的正确性,探讨了碰撞速度、壁面温度和油液温度对油膜动态铺展和传热的影响。结果表明,油滴与高温固体壁面碰撞后,少量 “卷吸”空气滞留于铺展油膜中心形成气泡,气泡上浮至油膜表面后发生“溃灭”;最大铺展直径的油膜呈中心平直、边缘凸起的圆盘状;油膜、空气和高温壁面三相接触线附近热交换较为剧烈,油膜边缘局部热流密度明显高于其它位置,且随着铺展进程而变得更加显著;无量纲铺展因子随着碰撞速度和油液温度的增大而增大,受壁面温度的影响却不明显;提高碰撞速度和壁面温度有利于油膜与高温壁面的换热,壁面平均热流密度增大;最大铺展直径时,随着碰撞速度、壁面温度和油液温度的增大,油膜径向热流密度是增大的。

关键词: 油滴, 高温固体壁面, 油膜, 动态铺展, 传热特性

Abstract: The lubrication and cooling states of mechanical parts under spray and drip lubrication conditions are dramatically influenced by the flow and heat transfer characteristics of the film formed by the impingement of oil droplet with parts surface. A three-dimensional numerical calculation model of the flow and heat transfer concerning a droplet impacting on a heated solid wall with the consideration of the correlation between the thermodynamic feature parameters of oil droplet and temperature is proposed using VOF(Volume of Fluid) method to predict numerically the droplet mor-phology evolution and the heat transfer between film and heated surface. The correctness of the presented model is demonstrated by comparison of the numerical results with experimental data. The effects of incident velocity, wall temperature and droplet temperature are discussed in detailed. The results show that inside the center of the spreading film a lone bubble is formed by air entrapment between droplet and solid wall during the initial stages of impact, and then the bubble collapses and escapes into the air when it floats upward to the film surface. The film at maximum spreading diameter appears to be a plate with a flat center region and a protruding rim. The drastic heat exchange occurs in the vicinity of three-phase contact line of film, air and heated wall, so that local heat flux near the film rim is significantly greater than that of other region inside the spreading film, as well as the phenomenon becomes more remarkably with the spreading process. The dimensionless spreading factor increases with increasing of the incident velocity and the droplet temperature, and seems to affect insignificantly by the wall temperature. The in-creased incident velocity and wall temperature contribute to the heat transfer between film and heated wall, so the average heat flux at the solid surface increases obviously. The radial heat flux in the film at the maximum spreading diameter increases with the incident velocity and the wall temperature.

Key words: oil droplet, heated solid wall, oil film, dynamic spreading, heat transfer characteristic

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