Durability increase of wind turbine main shaft
Increasing sizes of the wind turbine components due the demand for higher performance and power output yield tougher design constraints and more challenging regulations in the certificates. Thus, the development cycles of the wind turbine components are more complex. The present main shaft is subjected to an oscillating bending loading over its lifetime but still has to be resistant extreme loads. Therefore, the main shaft has to be designed for a high durability and high reliability for guarantying a 20 years life time of the shaft.
Our solution: shape optimization with Tosca Structure
Traditionally, several different critical stress hotspot areas of the main shaft in the drive train systems are considered when applying Tosca Structure.shape for stress minimization. These critical stress hotspot areas of the main shaft are the notches in between the bearings, curvature differences on shaft for attaching shaft to hub, inner surfaces for hollow shaft and contacts areas in interfaces. For the present application Tosca Structure.shape modifies the surface of the front notch for minimizing the highest first principal stresses. The present application is mainly loaded in bending. Consequently, the 1st principal stress is directly related to the fatigue and lifetime of the shaft. During the automated optimization the notch is changed from its original radius to a conceptual different curvature. Furthermore, different manufacturing restrictions are considered during the optimization for the design area like turning and locking of the side notch interfaces towards the bearings. Thereby, the new shape designed shaft is directly applied in the existing manufacturing process.
Benefit for the customer
The maximum stress was reduced from 300 to 200 MPa using 10 iterations in the automated optimization process. Additionally, the shape design changes of the surface for the component are small but essential leading to significant stress reductions of the hotspot. Consequently, minor changes are required in the manufacturing process as the design shape changes are small. The new design allows a higher power output and loading of the entire system as the new shape designed main shaft can be applied to higher extreme and operational loads and still gain significantly enhancement in both reliability and lifetime, respectively.