Study Of Numerical Simulation Of Rime Icing Of Wind Turbine Blade And Natural Icing Verification

In recent years,clean energy including wind energy has developed rapidly.However,in some high-latitude areas and low-latitude inland mountains,wind turbines are susceptible to the impact of icing.It will destroy aerodynamic performance,reduce power output and even lead to shut down.Icing is a complex physical process involving fluid mechanics,aerodynamics,and thermodynamics,it is difficult to simulate and test.The establishment of wind turbine blade icing numerical model and prediction of ice shape are of great significance for guiding the safe operation of wind turbines during icing period,and anti-icing design of airfoils.Starting from the basic physical process of blade icing,this paper uses the method of combining natural icing observation,icing model establishment and simulation analysis to study the accretion of blade rime icing.First,distribution characteristics of icing were analyzed by icing observation under different natural conditions.Then,the external airflow field of wind turbine blades,the trajectory of water droplets and the collision process are studied.Third,the freezing characteristics of the water droplet on the surface of wind turbine blade are studied,and a numerical model for rime icing of wind turbine blade is constructed.In this paper:Icing observations were made on 300 k W wind power equipment at Xuefeng Mountain Scientific Observation and Research Station.The results showed that leading edge and windward side of the blade are the main areas covered by ice,and ice thickness gradually increase from root to the tip of blade.As the temperature decreases,the type of icing will develop from glaze ice to rime ice,and as the wind speed increases,the uneven degree of icing shape increases.Based on the special structure and operation mode of wind turbine blades,the three-dimensional blade are cut into several sections in the span direction,the three-dimensional objects are transformed into two-dimensional sections for icing simulation.This paper changed the tradition method,which names Finite Element Method,for external flow field calculation,and established a calculation model of the external flow field of wind turbine blade based on Boundary Element Method.The two-dimensional model has been reduced in dimension again,which greatly improves the calculation efficiency.The water droplet trajectory model was established based on Lagrangian method,and the water droplet collision model was established by the vector cross product theorem.The collision characteristics of the water droplets were analyzed.Results showed that leading edge and windward side is the mainly collision area.As the wind speed,medium volume diameter of the water droplet and the airfoil size increase,the local collision efficiency of water droplet will increase to varying degrees.This paper established a critical analysis model of dry-wet growth icing through heat and mass transfer theorem,and analyzed local freezing characteristics of blade surface.Results showed that within the scope of this paper,as the water droplet’s medium volume diameter and liquid water content increase,icing develops from rime ice to glaze ice.With the increase of wind speed,icing changes from glaze ice to rime ice.Through the integration of external flow field model,water droplet collision model and dry-wet growth icing model established in this paper,the two-dimensional icing results of several sections are finally synthesized into a three-dimensional icing image.A wind turbine rime icing calculation model is established.The model analyzes three-dimensional rime icing distribution characteristics of wind turbines and the influence of different environmental factors on rime icing.Results show the distribution characteristics consistent with observation results.Icing accumulates on the leading edge and windward side.Ice thickness increases gradually along the blade.The increase in medium volume diameter of water droplets,liquid water content and wind speed will all lead to the increase of ice thickness of the blade.The experimental results of natural rime icing on Xuefeng Mountain are used to verify the model in this paper.After comparing the simulation results with the observation results,the agreement between the two is relatively high,icing distribution characteristics are relatively similar,and the relative error of icing thickness at blade tip is within 13%.