Research On Influence Of Air Density On Fatigue Life Of Large Wind Turbine Blades

There are significant differences in climate and air density between the north and the south of China.When wind turbines are applied to wind farms in different regions of China,the influence of air density is often neglected,leading to premature fatigue damage of wind turbine blades in some wind farms.Therefore,it is of great significance to study the influence of air density on fatigue life of wind turbine blades.This paper takes a 2MW large wind turbine blade as the research object to conduct climate investigation on seven wind farms in Xinjiang,Tibet,Heilongjiang,Hainan,Zhejiang,Shanxi and Hunan.The results show that the air density in Heilongjiang has the largest variation,with annual variation of 17.7%.The biggest difference between different regions is Heilongjiang and Tibet,and Heilongjiang air density is 1.74 times of that in Tibet.The influence of air density on power generation and thrust coefficient of the 2MW wind turbine is analyzed separately,and it is found that the power generation and coefficient are positively correlated with air density.Based on GH-Blade software to simulate the real wind conditions,the load of blades under standard air density and actual air density are calculated respectively,and then the load data of blades under different air density at rated wind speed are compared.The results show that with the increase of air density,the load on the 2MW wind turbine blades increases gradually,and the load in the oscillation direction increases most obviously.When the air density increases from 0.71kg/m3 to 1.27kg/m3,the force in the oscillation direction increases by 33.865 kN on average.Based on Profili software to process blade airfoil data,Solidworks software to build aerodynamic shell model of blade,Ansys Acp module to design blade layer structure,and 3D solid model of 2MW is obtained.Then according to GL standard,stress-strain analysis and static strength check are carried out on the blades.The results show that the stress.on the blade will increase with the increase of air density;the blades will not fail due to excessive stress;the maximum deformation at the 2MW blade tip is 1.4m,which is less than 50%of the distance between the blades and the tower,which meets the requirements of GL standard.Based on nCode software,the fatigue analysis process is established to calculate the damage of the blade under different wind speed condition,and blade life is calculated by effective time corresponding to wind speed and Miner cumulative damage theory.The fatigue life of blades under different air densities is calculated,and the damage cloud and life are compared.The results show that the fatigue life of blades is negatively correlated with air density.The higher the air density,the lower the fatigue life of blades.The 2MW blade fatigue life is 18.20 years when the air density is 1.27 kg/m3,and 32.05 years when the air density is 0.71 kg/m3.