Research On Ultrasonic-based De-icing Method For Wind Turbine Blades

Wind power and photovoltaics are known as the "twin stars" of the new energy sector.80% of China’s wind energy resources are concentrated in the three northern regions(Northwest,Northeast and North China).Due to the high altitude,high latitude and cold climate in these regions,wind turbine blades are prone to icing.At present,the mainstream wind turbine blade de-icing methods include mechanical de-icing method,colored blade de-icing method,electrically heated de-icing method,etc.,but these methods have high energy consumption,low efficiency and environmental pollution and other problems,limiting the development of blade de-icing technology.This thesis takes the 600 W small wind turbine blade as the research object,divides the blade into three parts: the root,the middle and the tip of the blade,and proposes a research method of dividing the blade section into windward and leeward sides along the maximum chord length of the blade airfoil direction,and carries out the research of ultrasonic de-icing method on the blade through the combination of simulation and experiment.The main research elements include:First,using ANSYS Workbench simulation software,the effect of different numbers of piezoelectric sheets and installation distance on ultrasonic de-icing frequency and de-icing area is analyzed.The results show that the best de-icing effect is achieved by the shear stress distribution of ultrasonic waves excited on the blades when three piezoelectric transducers are installed with a 60 mm installation distance.An increase in the number of piezoelectric transducers leads to a decrease in the frequency of ultrasonic de-icing.Second,ultrasonic de-icing simulations were carried out for different ice thicknesses on the windward side of the blade.The results show that as the ice thickness increases,the ultrasonic de-icing frequency on the windward side of the blade decreases and then increases,and the de-icing frequency on the windward side of the blade is higher than that on the root and tip of the blade.Third,ultrasonic de-icing simulations were carried out for ice cover at different radii of curvature of the blade.The results show that along the airfoil direction,the ultrasonic de-icing frequency at the leading edge is higher than that at the windward and leeward sides.Along the blade spreading direction,the ultrasonic de-icing frequency shows an increasing and then decreasing trend along the blade spreading direction due to the greater thickness and twist in the blade.Fourth,the effect of piezoelectric transducer installation spacing on the ultrasonic de-icing effect was analyzed for the windward side of the blade.When the installation spacing of piezoelectric transducer is 60 mm and 120 mm,the ultrasonic de-icing frequency can be reduced through stress superposition to achieve the purpose of de-icing.Fifth,the simulation analysis of different excitation voltages in the windward side of the blade shows that the ultrasonic shear stress increases linearly with increasing excitation voltage,but does not change the de-icing frequency and the distribution of shear stress between the ice layer and the blade.This can be achieved by adjusting the excitation voltage and thus changing the ultrasonic de-icing power to achieve de-icing at a lower de-icing power.Sixth,on the basis of theoretical research and simulation analysis,an ultrasonic de-icing test system was designed and built to conduct de-icing tests on the middle part of the blade.The results show that the de-icing frequency decreases as the number of piezoelectric transducers increases.An increase in the thickness of the ice layer leads to a decrease and then an increase in the de-icing frequency.Ultrasonic de-icing frequencies at different radii of curvature of the blade gradually increase as the radius of curvature decreases,and the de-icing frequencies in the leading edge region are higher than those in the windward and leeward sides.Due to the cavitation and thermal effects of ultrasound,the percentage of de-icing area obtained from the test is greater than that obtained from the simulation analysis.