Dy-Rex: Dynamic control of axial load superposition in roller bearings in drive trains of wind turbines

At a glance

• The bearings in the gearboxes of wind turbines are subject to extreme loads and often fail before the end of the calculated service life of the turbine.
• This is due to volatile operating conditions which impede continuous and optimal lubrication of the bearings and thus provoke damage.
• Within the scope of the Dy-Rex research project, Fraunhofer IWES is developing dynamic control strategies which aim to prevent operating states which provoke damage using superload positions.

The challenge

The bearings in wind turbine gearboxes are subject to tough operating conditions. Rapid load and speed changes caused by varying wind conditions as well as starting and stopping have an impact on the slippage behavior of the rolling elements and the lubrication film which separates these elements. Damage such as white etching cracks can result, which, in turn, lead to the bearings often failing before the end of the calculated service life. For wind farm operators, this translates to downtimes and expensive repairs.

The solution

Fraunhofer IWES’ Dy-Rex research project is addressing this problem and investigating how better operating conditions can be created for bearings. As the speed of the gearbox depends on the wind conditions and cannot be influenced, Dy-Rex focuses primarily on the load. Given that the external load is also wind-dependent, the researchers are taking the approach of applying an additional load, a load superposition, with the help of an actuator. Reducing or increasing the preload can have a positive influence on the lubrication conditions in the bearing and thereby prevent damage-inducing operating states.

The added value

The aim is to use multi-body simulations and tests on the institute’s own test bench in order to establish the basic principles required for damage-reducing, dynamic control of a load superposition for bearings in wind turbine gearboxes. On the basis of these principles, it will then be possible to develop control strategies which can prevent damage to the bearings.