Study On The Load And Vibration Characteristics Of Umbrella Wind Turbines Under Different Shrinkage Angles

With the increasing proportion of distributed wind power in renewable energy,diversified distributed wind power projects have put forward higher requirements for the reliability and safety of the generating units.Therefore,the research group proposed an umbrella wind turbine that actively adjusts its output power.The wind turbine can stabilize the output power and protect the wind turbine by adjusting the shrinkage angle under super-rated wind speed conditions.However,in the actual operation process,the umbrella adjustment mechanism is subjected to very complex alternating loads.In order to avoid mechanical damage to the key parts of the adjustment mechanism and ensure the safe and reliable operation of the umbrella wind turbine,different shrinkage angles are performed on it.The study of load and vibration characteristics under conditions is of great significance.Use the finite element simulation software ANSYS to perform static analysis on umbrella wind turbines under different shrinkage angles and speeds,and check the strength of key components according to the results;based on the numerical simulation results,the load characteristics of the key components of the umbrella wind turbine and the vibration characteristics of the whole machine under different shrinkage angle are tested through wind tunnel tests.The main conclusions are as follows:(1)The static characteristics of the key components of umbrella wind turbines,blades,blade supports,links,big wheels and small wheels are studied.The results show that the stress values of blades,blade supports,links and small wheels under different speed conditions all reach their peaks at the shrinkage angle of 45°.When the shrinkage angle increases to 60°,the stress values all show a downward trend,played the purpose of protecting the wind turbine under strong wind conditions.Under different speed conditions,the stress value of the big wheels is at its peak when the contraction angle is 0°.As the contraction angle increases,the stress value of the big wheels begins to decrease.When the contraction angle reaches 60°,the stress value of the big wheels is the smallest.According to the numerical simulation results,the strength of the key components of the adjusting mechanism is checked.The results show that the adjusting mechanism can satisfy the stable and reliable operation of the umbrella wind turbine.(2)Based on the numerical simulation results,strain gauges are arranged in the stress concentration areas of key components and the load characteristics are tested.The results show that the bending moment of bending moment of blade root vibration reaches the peak value at 45° shrinkage angle under different speed conditions,while the swing bending moment shows a trend of decreasing with the increase of shrinkage angle,and the swing bending moment reaches the minimum value at 60° shrinkage angle.The stress values of blade support,links and small wheels under different rotation speeds have basically the same trend with the shrinkage angle,and the stress values of the measuring points all reach the peak value at the shrinkage angle of 45°.Under different speed conditions,the stress value of the big wheels decreases with the increase of the shrinkage angle,and the stress value of the big wheels is the smallest when the shrinkage angle reaches 60°.(3)The pitch and side bending moments at the top and bottom of the tower at different speeds all decrease with the increase of the shrinkage angle.Due to the different arm lengths,the peak bending moment at the bottom of the tower is larger than the peak bending moment at the top,which is consistent with the tower load distribution during the actual operation of the umbrella wind turbine.It also verifies that the umbrella adjustment method has good wind shelter performance.(4)In the range of the shrinkage angle from 0° to 35°,the amplitude of the vertical radial measurement points at different heights of the tower increases with the increase of wind speed.At 45° and 60° shrinkage angles,when the incoming wind speed is 5m/s-7m/s,the amplitude of the measuring points at different heights of the tower increases suddenly,but as the wind speed increases,the blades are stiffened due to their own centrifugal force.,the amplitude of measuring points at different heights of the tower has decreased.The vertical and radial directions of the maximum vibration acceleration and the characteristic frequency of the tower at different heights are basically the same with the shrinkage angle.(5)There is no significant fluctuation in the amplitude of the measuring point at different heights of the tower tube horizontal and radial under different shrinkage angles with the wind speed.In each wind speed section under the same shrinkage angle,the maximum amplitude of the measuring point decreases as the height decreases.For the measuring point at the same height,as the shrinkage angle increases,the maximum horizontal radial amplitude of the tower increases.The change trend of the maximum vibration acceleration amplitude at different heights of the tower in the horizontal and radial directions with the shrinkage angle is basically the same,and both reach the peak value at the shrinkage angle of 45°.Under the same shrinkage angle,the maximum vibration acceleration amplitude of the horizontal radial measuring point of the tower tube decreases from high to low along the tower tube,and its main vibration mode is bending vibration.(6)Under the shrinkage angles of 0°,15°,25°,35°,the vertical radial amplitude of the generator increases first,then decreases and then increases with the change of wind speed,especially when the incoming wind speed is 9m/s,the amplitude increases significantly.As the incoming wind speed reaches the rated wind speed of llm/s,the wind turbine gradually tends to operate in a stable state,and the vertical radial amplitude of the generator decreases.The vertical radial amplitude has a clear upward trend.However,at 45° and 60° shrinkage angles,the vertical radial amplitude of the generator did not change significantly with wind speed.Through a combination of numerical simulation and experiment,the load and vibration characteristics of umbrella wind turbines under different shrinkage angles are studied,and the operational reliability and safety of umbrella wind turbines are verified.It has certain aspects in the optimization of umbrella wind turbine structure and control strategy guiding significance.