The trend towards large, multi-megawatt wind turbines, particularly in offshore wind farms, has led to a change in the design of their bearings. Increasingly important is where the wind turbine rotor is supported only by a single, double row tapered roller bearing or ‘moment’ bearing, typically in a back-to-back arrangement that supports all forces and moments.
Not only do single bearings result in more compact designs, but preloaded tapered roller bearings can be utilised, which prevent axial clearance and small axial misalignments. This controlled guidance of the rotor shaft means that fewer movements act on the system, reducing the negative effects on the gearbox and generator.
The Schaeffler Group has developed a single bearing design concept for multi-megawatt wind turbine rotor shafts, which not only improves the energy efficiency and reliability of the turbine, but also eliminates drive train components, helping to reduce the overall weight of the turbine. By using its in-house advanced rolling bearing calculation software BEARINX, in combination with Finite Element Analysis tools and multi-body simulation (MBS) models, Schaeffler’s engineers can assist customers during the initial stages of wind turbine design.
This software enables the company to evaluate various load conditions and to accurately assess all relevant, critical load conditions. The use of ‘moment’ bearings in single bearing designs enables a high level of system integration, resulting in extremely compact, less complex wind turbine designs. The preloaded bearing also prevents the transfer of negative axial loads to the wind turbine drive train. The company has already implemented numerous single bearing solutions for customers, including 5MW offshore wind turbines, and has expanded BEARINX to include elasticity effects, which are calculated using Finite Element Methods (FEM), enabling it to analyse bearings including the influences of housings.
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