Theme group 3: Mechanical Systems and Structures

​The focus of thematic group 3 is in two main topics. Within the first main topic the focus is on the drivetrain, i.e. the mechanical system of a wind turbine that transmits power from the rotor's hub to the power electronics (generator) and can be described as a complex controlled electro-mechanical multi-body system subjected to a random load. The components of the drive train, such as bearings, shafts, gearboxes, brakes, clutch, and generator are mounted inside a nacelle on top of a flexible tower. With the design the random winds and external circumstances that give widely varying loads with large axial forces and bending moments in the main shaft have to be taken into account. The tower's flexibility and foundation and changes in load due to events in the power electronics (e.g. short circuit) need to be considered. Internal factors are the high gear ratio (for indirectly driven turbines) that set high demands for components and lubricants, manufacturing quality and low noise emissions. From a design perspective, the big engineering challenge is to ensure the reliability of the system and its functional components over the 20-year expected service life.
 
Within the second main topic the focus is on bearing structure which in this context includes all mechanical subsystems that interact, among other things, to bear the wind load on the generator and the tower down to the wind turbine foundations. In Stage 1 of the Centre's activities, the main part of the activities focuses on rotor blades, which themselves bear the wind load onto the rotor hub, but also the larger part of the wind turbine system as part of an optimisation study. Of key interest for the supporting structure is the choice of technical solution, material selection, dimensioning and performance.
 
Issues within Mechanical Systems and Structures are:
  • To which loads and movements is a drivetrain exposed under different operating conditions?
  • Which phenomenon is critical for drivetrain component service life? Does current knowledge about individual drivetrain components' lifetime suffice and to what degree of complexity must mathematical and computational models be developed to predict the service life of the components? Which level of detail is required for a model to be used successfully and effectively for different dynamic processes?
  • How important is the interaction between the internal dynamics of the various subsystems of a wind turbine? What motion in the nacelle is the result of the different aerodynamic loads and how does this proposal affect the drivetrain's dynamic environment? Is it necessary to include the tower and generator dynamics in the calculations for the study and analysis of bearings, fittings, axles and gearbox? 
  • How can specific problems with unexpected bearing and gear damage be explained? 
  • How detailed should a model of the drivetrain be to evaluate algorithms for “automatic” commissioning of control systems for wind turbines?
  • What can modern methods of model validation and model calibration of wind turbines contribute in gaining physical understanding and could this lead to modelling guidelines based on sound physical principles?
  • In the wind turbine the choice of technology solutions for components influences the mechanical environment for other components. How does this impact occur and how can the whole system be optimised overall and analysed by synthesis and simulation. How should the optimisation tool be designed to best support the development of wind turbines?
  • Are modern OMA methods sufficiently reliable to be used in monitoring the turbine's state of health?
  • What can be gained by introducing a probabilistic approach towards wind turbine dimensioning?
  • Can lignin-based composite replace or supplement fibreglass and/or carbon fibre composite and how can material combinations in the blades be used to enhance the damping properties?
  • How does the balance between maximising the annual energy production, system security, minimising peak weight, system maintenance costs and restrictions on noise vibration take place?
The following projects within the Centre fall under Theme group 3:

Published: Mon 01 Feb 2016. Modified: Mon 14 Mar 2016