OWT Drivetrain & Gearbox Simulation and Testing
As wind turbines continue to grow in size and offshore installations become more and more attractive for investors, the design of reliable drivetrains and gearboxes is becoming very critical. One key element is represented by the challenging environmental conditions, which are significantly different and harsher than those experienced by onshore machines. Additionally, a deeper understanding of the operational loads and the effects of combined aero—and hydrodynamic forces on the drivetrain is essential to ensure the wind turbines can be guaranteed for the expected lifetime. These problems result in increased research efforts towards improving the capabilities and the use of simulation tools to better understand the complex drivetrain dynamic behavior. In parallel, advances in experimental techniques are also sought, as a way of deriving reliable information for model verification and validation, and to get a deeper insight in the structure operational response.
KeywordsWind Turbine Gear Pair Planet Carrier Model Order Reduction Technique Wind Turbine Design
8.1 Simulation and Testing in Drivetrain and Gearbox Design
Gearboxes typically have the advantage of requiring smaller initial investments, but because of the number of rotating parts, gear pairs and bearings, reliability is typically an issue. On the other hand, direct-drive machines require a bigger investment related to the development and construction of big permanent magnet generators but have typically lower operation and maintenance costs. To guarantee the effectiveness and competitiveness of the gearbox solution, significant improvements in the design phase are required to better understand the mechanisms leading to gearbox failures. This can only be achieved by developing more accurate, reliable and efficient numerical models, able to replicate not only the global load transfer paths across the driveline but also the local load transfer mechanisms.
The conclusion of Peeters (2006) paved the way for further developments and optimization in the modelling strategies of gearboxes. In the work of Helsen (2012) efficient simulation strategies have been investigated to understand the interaction of the turbine transients with the dynamic excitation within the drivetrain originating from the meshing gears and the full drivetrain structural behavior. The importance of modelling dynamic flexibility of internal gearbox components such as the ring wheel and the planet carrier(s) has also been investigated. Advanced model order reduction techniques based on static mode switching (Tamarozzi et al.2013) have been applied to accurately simulate a 3D gear contact problem. The results show that the method is able to keep the same level of accuracy of fully non-linear simulation models while drastically reducing the computational resources. Finally, the recent work of Vanhollebeke (2015) demonstrated the possibility to use very accurate flexible MBS models of gearbox and to integrate them in the design phase not only to accurately predict loads but also to efficiently analyze possible NVH problems such as tonalities and vibrations.
Within the MAREWINT project, specific activities were conducted to follow up on these findings and complement the existing work with focus on two specific aspects. Chapter 9 focuses on a review of advanced modelling techniques for bearing and the optimal integration of these models in a flexible multibody simulation environment. In Chap. 10, recent advances on the experimental characterization of gearboxes in operations are presented. Being able to identify an operational model of the gearbox under different loading conditions will provide valuable inputs for validation of global gearbox models and verification of design assumptions.
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