Supercooled large droplet icing accretion and its unsteady aerodynamic characteristics on high-lift devices

摘要

Given the importance of understanding new FAR25, Appendix O certification, supercooled large droplet icing characteristics and its damages should be specified because of its serious hazard to in-flight safety and aircraft engineering. This study compares the icing feature and aerodynamic degradation of high-lift devices under different diameter conditions using a verified numerical method SJTUICE (a ice accretion simulating code by Shanghai Jiao Tong Univeristy). With two different flow and freezing time-steps T-f and T-s, the accuracies on fluid dynamic and icing predictions over a long period of time can be both controlled within an acceptable range. The comparisons between supercooled large droplet and non-supercooled large droplet conditions reflect that larger diameters induce more intense icing characteristics on the suction-side of each airfoil, in which the leading edge of flap is the most sensitive one to drop size. The second-accelerated flow near the gap is adverse to smaller droplet collection but benefit for impact thermodynamic enhancement of those larger collected droplets. The ice-caused gap narrowing makes flow separation earlier, which finally leads to the degradation of global high-lift performance worsen. Lift coefficient comparison also indicates the performance of high-lift devices decays more quickly under supercooled large droplet conditions. Results of this paper highlight the supercooled large droplet icing effects with respect to smaller diameter conditions.