A Novel Multi-Point Excitation Fatigue Testing Method for Wind Turbine Rotor Blades

Abstract

Wind turbine blades have to withstand the rigorous test of 20-25 years of service. Fatigue testing is an accurate method used to verify blade reliability. Multi-point excitation could better fit the fatigue damage distribution, which reduces the power output of a single exciter and saves testing energy consumption. The amplitude, phase, and frequency characteristics of the fatigue test system and, moreover, the relationship between the excitation force, damping, and the amplitude variation of the blade, are analyzed by the Lagrangian equation and the finite element simulation method. The full-scale fatigue test of an equivalent full cycle life in the flapwise direction is carried out by multi-excitation. When the frequency and phase of the multi-point exciters are consistent, the maximum vibration effect can be exerted. When the phase difference of the dual exciters is 180 • , the vibration effect produced by the dual exciters can be equivalent to each other. The blade amplitude is proportional to excitation forces, while inversely proportional to the damping ratio. The bending moment deviation of the blade is controlled within 9.2%; moreover, the energy consumption is 40% lower than that of the single-point excitation. The use of multi-point excitation allows loading the blade with high precision, stable operation, and low cost, which provides the theoretical and experimental basis for the fatigue test of large wind turbine blades.Keywords: fatigue test; wind turbine blade; multi-point excitation; damage distribution; the equivalent fatigue life cycle Highlights: (1) The multi-point excitation fatigue testing method renders an equal fatigue damage distribution with a higher degree of fidelity; (2) The program fits the fatigue damage distribution by adjusting the parameters of multi-point exciters rather than tuning masses, which could reduce each exciter power and save energy; (3) The multi-point excitation has the characteristics of high loading accuracy and stable operation, which are able to meet the large blade fatigue test requirements by adding exciters.

Joint excitation synchronization characteristics of fatigue test for offshore wind turbine blade

“…Kong Xiaojia et al 15 aimed at the synchronization problem of two excitation sources of wind turbine blade, studied the action law of two loading sources of flexible connection and non-coplanar wind turbine blades. Pan Zujin et al 16 analyze the relationship between the excitation force, damping, and the amplitude variation of the blade by the Lagrange equation the finite element simulation method, and proved that multi-point excitation could better fit the fatigue damage distribution.…”