Studies Of Frost Formation And Icing Simulation Of Wind Turbine Blade

Frosting does much harm in industries of cooling systems, aerospace, and windpower generation. Much research has been conducted on frosting. In the recent years,the research has been deepened into the internal details of frost layer and dynamicstructure characteristic. However, there is not enough research on the frost layer andwet air parameters during frosting process. The research on ice formation on thesurface of wind turbine blade is also insufficient. This paper studied the influence ofthe environment parameters and cold surface temperature on the super-cooled waterbead and ice volume fraction through experiment. Then studied the rule of frost layerand wet air parameters in process of frost growing, and the influence of attack angleand velocity for icing on wind turbine.Through vision research on initial frost formation, this paper finds that theformation of super-cooled water droplet and freezing is influenced by environmentalcondition. Before the frost crystal appearing, there are drops generation,polymerization, and freezing on the cold surface, but the appearing moment andfreezing time is influenced by environment. When the velocity is faster, thetemperature of cold surface and environment is lower, the super-cooled water dropletwill appear earlier and the freezing time is shorter. The volume fraction of ice crystalwill decrease with the cold surface temperature decreasing, the velocity increasing andthe ambient temperature increasing. This paper improved the quality transmissioncriterion and model for the traditional frost model, simulated the growth process offrost layer, examined the changing rule for the frost layer and wet air parameters withspace, time, environmental temperature, relative humidity, wind speed and cold surfacetemperature, found that the simulated results is conform to experimental results, andthe greater the velocity, the more uniform the ice phase volume fraction along the airflow distribution. The ice volume fraction inside frost layer is bigger when time islonger and height is small, and reduces gradually along the air flow, with highlydecreasing near the inlet and a small rise near the export.On the basis of the frost model under cool surface, an ice accretion model on windturbine surface is established with turbulence model and the new mass transfer model, and the icing procedure on the wind turbine is simulated when the air which containssuper-cooled water droplet flows through the blade. Then find that: Firstly, the freezingoccurred in the windward side generally, because there is little impact of air flow onthe super-cooled water droplet; Secondly, the blade surface icing morphology changeswith the attack angle. With the attack angle increasing, the icing area and icing are alsoincreasing; Thirdly, the air flow strikes to the stagnation point vertically, so the areanearby of the stagnation point has more ice; Finally, when the velocity increases, thesuper-cooled water droplet number which strikes the blade also increases in unit time,and then makes the ice quantity on the blade surface increased significantly.