考虑水膜破裂的机翼热气防冰系统传热耦合特性研究

Aircraft anti-icing is a complex multiphysics field coupling phenomena including mechanics and thermoldynamics. On the one hand, the hot air anti-icing surface suffers the external air flow, droplet impingement and the water evaporation. On the other hand, the internal surface is heated due to the complex three-dimensional hot air injection flow inside the anti-icing cavity. Thus, the external and internal coupled heat transfer characteristics of a hot air anti-icing system is very complicated. At the moment, there is not deep understanding of the coupled heat transfer characteristics of hot air anti-icing system, for which the numerical method especially in three-dimensional is immature. In addition, the mobility patterns of the runback water on heated surface are influced by aerodynamic force, surface tension, surface wettability and other various factors. The change of the pattern of runback water leads to different surface wetting factors,which causes a great impact on the coupled heat transfer characteristics on anti-icing surface. In this project, the coupled heat transfer characteristics of a wing hot air anti-icing system considering water film breakup into rivulets, containing heat transfers between internal hot air and solid skin, between runback water and solid skin, between external air and water or solid skin, will be studied through theoretical analysis and numerical calculation. The dynamic properties of the water film, the critical conditions of the water film breakup into rivulets, the dynamic and thermodynamic properties of the rivulets on the three-dimensional anti-icing surface will be investigated in depth. The prediction models and tight coupling numerical simulation methods for the runback water and anti-icing surface temperature will be established in this project. Through the study of this project, the movement of the runback water, the characteristics of the breakup of water film on heated surface and the impact on the anti-icing coupled heat transfer characteristics will be better understood, which is to the benefit of the design and optimization of the anti-icing system.

飞机防冰是一个复杂的热力学多场耦合物理现象。热气防冰表面一方面受到外部气流、水滴撞击和蒸发的影响；另一方面防冰腔内部热气喷射的复杂三维流动对表面加热，使得热气防冰系统的内外传热耦合特性较复杂。目前对于三维热气防冰系统内外传热耦合特性的认识不深，计算方法不成熟。此外，防冰表面溢流水的流动形态变化受气动力、表面张力、表面浸润性等多方面因素的影响，从水膜过渡到溪状流，表面润湿系数不同，这对防冰表面传热耦合特性影响较大。项目通过理论分析和数值计算，对考虑溢流水破裂现象的机翼热气防冰系统内部热气、蒙皮、溢流水、外部空气多相传热耦合特性进行研究。深入地认识三维防冰加热表面水膜运动及破裂的临界条件、溪状流的动力学和热力学特性；建立内外传热耦合计算表面温度的预测模型和强固耦合数值模拟方法。通过本项目的研究，可更好地掌握三维防冰表面溢流水流动破裂特性及对防冰传热耦合特性的影响，有利于防冰系统的设计与优化。

飞机防冰是一个复杂的热力学多场耦合物理现象。热气防冰表面一方面受外部气流、水滴撞击和蒸发的影响；另一方面防冰腔内部热气喷射的复杂三维流动对表面加热，使得热气防冰系统的内外传热耦合特性较复杂。由于申请本项目时国内对于三维热气防冰系统内外传热耦合特性的认识不深，计算方法不成熟。此外，防冰表面溢流水的流动形态变化从水膜过渡到溪状流，表面润湿系数不同，这对防冰表面传热耦合特性影响较大。因此，本项目对考虑溢流水破裂现象的机翼热气防冰系统内部热气、蒙皮、溢流水、外部空气多相传热耦合特性进行研究。研究中认识到防冰腔内部射流冲击换热特性对防冰系统热力耦合有较大影响，因此对此也开展了研究。主要研究内容包括：（1）三维后掠翼防冰表面的水膜运动特性研究；（2）机翼防冰表面水膜破裂运动机理研究；（3）考虑溢流水破裂的三维后掠翼热气防冰系统多相传热耦合特性研究；（4）防冰系统内部复杂流动换热特性研究。经过上述研究，本项目建立了三维表面溢流水水膜流动模型和溢流水量计算数值模拟方法；建立了防冰表面水膜破裂运动模型和数值求解方法；建立了热气防冰系统内外强固耦合方法预测壁面温度模型和数值模拟方法；获得了管壁距、喷口雷诺数、入射角度等因素对防冰系统内部换热特性的影响规律。研究结果表明：（1）在空气剪切力作用下的防冰表面水膜的流动受剪切力的方向和大小决定，在驻点处溢流水量存在极大值。所开发的水膜流动程序不仅能够应用于三维后掠翼表面水膜计算，还能用于三维发动机进气道唇口的计算；（2）在连续最大的结冰条件下，水膜破裂一般发生在撞击极限位置。无量纲临界水膜厚度受表面接触角的影响较大，且随着接触角的增大临界水膜厚度增大。某给定的结冰条件下，引入破裂模型后，溢流水的溢流范围在两个不同工况下分别增大了33%和17%，这会很大程度影响防冰热载荷的分布；（3）开发了三维防冰系统内外传热耦合计算程序，结果显示水膜破裂后，表面润湿因子减小，溢流水蒸发量减小，导致防冰热载荷减小，而防冰系统提供的过多的加热热流使壁面温度升高；（4）喷口雷诺数Rej越大，射流冲击换热性能越好；弦向3孔射流壁面换热特性呈单峰；在实验范围内，单孔垂直射流防冰系统表面，相对孔壁距H/d = 4.5时能够使冲击壁面的驻点换热性能达到最好。通过本项目的研究，较好地掌握了三维防冰表面溢流水流动破裂特性及对防冰传热耦合特性的影响，有利于防冰系统的设计与优化。