高速冷气流夹带液滴沿程参数的变化及其对撞击结冰的影响

Icing wind tunnel test is of importance for aircraft icing, anti-icing and deicing research. It is also essential to aircraft airworthiness certification for flight in icing conditions. Simulation of icing clouds' parameters in icing wind tunnel are preconditions of test results correctness, and very important for confidence level of simulated icing conditions. Icing cloud is simulated by ejected droplets entrained in high speed cooled air flow in icing wind tunnel. In this research,droplet movement with high speed cooled air flow will be investigated.Significant parameters' variations along the way and their effects on impinging icing will be studied. Droplet movement coupled with momentum exchange, and heat and mass transfer between air flow and droplet will be modelled. Variations along the way of droplet parameters such as temperature, velocity, size, Liquid Water Content(LWC) and its distribution,which are significant for impinging and icing, will be studied quantitatively. Effects of various factors such as the speed and temperature of air flow, initial parameters of ejected droplet, etc. on the variations along the way will be also investigated theoretically and experimently. Research objectives are to master the mechanism of supercooled droplet generation and reveal the discipline of droplet movement under such conditions as well as its correlation to the test results in icing wind tunnel, explore the possible application of research achievements in test technology of icing wind tunnel and the area of aircraft icing ,anti-icing and deicing research. This project involves in the research of multi-disciplinary, across scales and multi-parameter. From this investigation, we would not only learn more about the law of droplet moving with high speed air, but also improve our comprehension of the multiphase flow theory. Achievements obtained from this research would be applied to the icing wing tunnels being established in domestic and evaluation of test results of icing wing tunnel. The investigation has important academic significance and practical application value.

飞机结冰严重影响飞行安全，大气中与飞机相对运动的过冷水滴撞击到温度低于冰点的飞机表面是飞机结冰的主要原因。冰风洞是研究飞机结冰和防除冰的专用设备，其特有的过冷水滴的模拟及其相关参数的确定是保障冰风洞试验结果置信度的重要条件。本项目以冰风洞中随高速冷气流运动的水滴为研究对象，研究其运动过程中重要参数的沿程变化及其对撞击结冰的影响。建立描述水滴与气流之间动量交换及热质传递的水滴运动数学模型，定量分析水滴在随高速冷气流运动过程中的传热传质以及温度、速度、尺度、液态水含量及其分布等与撞击结冰相关的重要参数的沿程变化，考察各种因素的影响，并进行实验验证，掌握过冷水滴的产生机理、运动规律及其与实验结果的相关性，探索研究成果在冰风洞试验技术及飞机结冰和防除冰领域的应用。本课题涉及多学科交叉，及跨尺度、多参数研究，对提高人们对多相流理论的认识和理解及对冰风洞试验结果的正确评估，具有重要的学术意义和应用价值

飞机结冰严重影响飞行安全，大气中与飞机相对运动的过冷水滴撞击到温度低于冰点的飞机表面是飞机结冰的主要原因。冰风洞是研究飞机结冰和防除冰的专用设备，其特有的过冷水滴的模拟及其相关参数的确定是保障冰风洞试验结果置信度的重要条件。本项目以冰风洞中随高速冷气流运动的水滴为研究对象，研究水滴沿程参数的变化及其对撞击结冰的影响。.针对水滴沿程参数变化，建立了水滴与冷气流之间动量，质量和热量交换的数学模型，并根据建立的模型开发了相应的计算程序，计算了不同直径水滴随气流运动中速度、运动轨迹、温度和直径的变化，讨论了空气及水滴初始参数对水滴沿程参数变化的影响。结果表明：小水滴相对于大水滴对空气流场具有更好的跟随性；蒸发作用导致水滴尺寸减小，提高空气相对湿度，降低喷嘴出口处水滴温度可有效抑制水滴蒸发，有利于保持水滴尺寸与含量的稳定性； 气流温度较低时，水滴会发生结冰，结冰位置和结冰时间随水滴尺寸发生变化。在单水滴沿程参数计算的基础上，加入随机游走模型及水滴碰撞与聚合模型，模拟了单喷嘴及多喷嘴下水滴簇平均参数的变化规律，对内混式空气助力雾化喷嘴水滴尺寸分布进行了实验研究，与仿真结果对比，验证了水滴质量双R分布模型的合理性。.针对水滴沿程参数变化对撞击结冰的影响，研究了水滴沿程速度及直径变化对撞击特性的影响。结果表明：水滴直径变化对撞击特性的影响很小，撞击特性主要受水滴速度沿程变化的影响，实际的局部收集系数大于理想实验条件下的局部收集系数；三维撞击特性的模拟结果表明：喷嘴的排布间距对试验段结冰云雾的均匀性有决定性影响，喷嘴间距越小，云雾分布越均匀；在撞击特性计算的基础上，进行了沿程参数对结冰影响的仿真，并开展了相关实验研究。仿真及实验结果表明：水滴沿程参数变化将导致仿真和冰风洞实验的结冰量增大。.本项目的研究结果对多相流理论的认识和理解及对冰风洞试验结果的正确评估，具有重要的学术意义和应用价值。