The Variation Of The Diameter Of Supercooled Large Droplets Along The Path And The Icing Similarity Criterion Of The Breakup Of Supercooled Large Droplets

The latest FAR icing regulations are considered,and it is found that the focus of airworthiness is to transfer to supercooled large droplets,and the icing wind tunnel test is a effective means to verify the compliance of supercooled water droplets.In this paper,the variation of the diameter of supercooled large droplets along the path and the icing similarity criterion of broken supercooled large droplets are explored.The specific work and conclusions are as follows:(1)The author of this paper systematically analyse the regulations and Advisory Airculars on icing,summarize the differences between European and American airworthiness regulations on icing,summarize the airworthiness requirements of icing detection system,aircraft protective surface components,aircraft non-protective surface components and engine inlet,and the process of compliance verification is introduced.(2)The research on the diameter variation of supercooled large droplets along icing wind tunnel is carried out.After the establishment of control equations and numerical model,the influence of velocity,temperature and humidity on the diameter variation is studied.Under the condition of this paper,different air velocity and water droplet velocity have the same critical breaking We.When We of stable section is greater than 12.49,the droplet will break in bag shape in the stable section of wind tunnel.If We of contraction section is greater than 4.38,the droplet will break in oscillation obviously in the contraction section.The influence of different air temperature and water droplet temperature is that the degree of fragmentation of supercooled large droplet increases with the increase of temperature.However,different relative humidity has little effect on droplet breakage.(3)After researching the breaking law of super cold droplets in ice tunnel,the icing similarity criterion of the broken supercooled large droplets is researched in order to guide the wind tunnel test.Based on Ruff method recommended by the Advisory Circulars,integrateded with the breakup similar dimensionless parameter B,and the speed selection considering the crushing is added.In order to achieve the rapid completion of the freezing conditions,the icing computation procedure is developed.The icing simulation results of the typical ice conditions of supercooled large droplets are compared with the results of the laboratory ice,and the correctness of the icing similarity criterion and the scaling program is verified.