Study On Key Problems In Airfoil Icing Simulation

When aircraft flying through low temperatures clouds at high altitudes, ice accretion may occur on the exposed surfaces due to the impingement of supercooled droplets, such as wing leading edges, Engine Inlet. The ice accreted on aircraft will affect the flight safety of aircraft. For example, the ice may degrade the aerodynamic performance by a sharp rise in drag and a reduction in the maximum lift coefficient due to the changed geometry and the increased surface roughness. Research on aircraft icing should provide insight into ice freezing mechanism and the icing effect on aerodynamic performance. It could provide a basis to design and optimize aircraft anti-icing system.This paper has studied several key problems about airfoil icing simulation. The main works in present thesis are as follow:(1) This paper introduces the reason for aircraft icing, typical icing component and ice accretion effects on aircraft performance. The ice accretion type and its feature were described, and the harms to aircraft of different types of iceshape were compared. Major research subjects and some important methods were pointed out, and the merits and demerits of each analytic method are analyzed and compared. Latest progress and research status of aircraft icing was summarized. The major work and researching significance were indicated.(2) The operating principle and system structure of icing wind tunnel at home and abroad were studied, and common calibration methods of atmospheric parameter were investigated. Small injection driven icing tunnel was designed and built using existing technologies and devices for ice accretion research. Standard icing blade technique was used to measure liquid water content in the icing tunnel test section. The uniformity of liquid water content was assessed by accreting ices on aluminum cylinder bars. Mean volumetric diameter of the spray cloud was determined by soot-coated slide.(3) Experimental technique and method were presented, including design approach of the test model, iceshape acquisition and testing procedure. Cylinder model was used to conduct an icing test and iceshape repeatability results of the different tests, iceshape repeatability results of the same test and iceshape results advanced with time were obtained. The experiments verify the feasibility and effectiveness of the present icing tunnel and test technique. Numerical prediction results under rime and glaze icing condition were compared with the experimental data measured in present icing tunnel. It is indicated that good overall agreement is achieved in both icing shape and impingement limit. The results has indicated that the icing tunnel system work well and test results are accurate and reliable.(4) Research background and significance of the icing similarity methods were introduced and mathematical equations of icing similarity theory were analyzed in terms of geometry, air flowfield, droplet trajectory, water catch, energy balance, water film dynamics. Icing similarity methods for rime and glaze ice were described and verified by ice accretion tests in the present icing wind tunnel. Icing similarity results improve the credibility of the test system and methods. It will lay the foundations for future icing and anti-ice research. Simultaneously it also confirmed that the scaling methods can extend the ability of test model size and icing atmospheric condition.(5) The flow characteristic of surface runback water was studied experimentally in wet anti-icing conditions and the results have shown that the collected water exists and moves in the form of water drop instead of water film. Mathematical model was built to describe the runback water drop motion and a method was introduced to calculate the geometry parameters and force in the model. Experimental systems were designed and built to calibrate the contact angle and correlation coefficients used in the calculation of surface retention force, the viscous drag and the aerodynamic force. The critical diameter of drop movement was given for different wind speed. Water drop movement on heating surface was simulated numerically by introducing the coefficients obtained from experiments into the motion model. The results show that the computation results are fit well with the test results. It is concluded that the present method can simulate the time history of water drop size and location on the heating surface accurately.(6) Some conclusions arising for present study are given and some ideas of the further work are depicted.