Low maintenance reliable transmissions for large wind turbines

Project Description:

This Research Project is part of the Aura CDT’s Low maintenance reliable transmissions for large wind turbines Cluster.

Almost all the bearings in wind turbine transmissions are rolling element type. That includes slow and high-speed shafts, gearbox, blade pitch bearings, and the main bearing that supports the rotor. Wind loading is highly variable and so bearings can operate at changeable speed, high and very variable loading. This is a bad place for bearings and there are lots of wear and fatigue failures – design life is 20 years but bearings rarely last that long. As machines have got larger, this state has worsened. Manufacturing very large bearings (up to 5m diameter) is expensive and repairing or replacing them very difficult. For example, to replace the main bearing requires the removal of the whole rotor and blades – imagine doing that at sea from a ship mounted crane. 

In other large scale machines (e.g. hydro-electric power stations, ships propeller bearing) sliding type or ‘hydrodynamic’ bearings are much more common (e.g. read about Waukesha’s Maxalign bearing). 

There is increasing interest from industry to come up with new designs for these kinds of bearing for wind turbine applications. There is believed to be a prototype turbine in China that has operated successfully for a year. Other bearing companies are interested and embarking on similar technologies; this video nicely explains their concepts.  

Some of the challenges will be around finding bearing design, materials, and lubricants that will withstand the high loads and start-stop nature of operation. This project is about supporting those developments. Some questions that will need to be addressed: will conventional bearing facing materials survive the extreme conditions, how will lubricant be supplied to the bearing faces in such a large assembly, will greases be adequate, the effect of saltwater contamination, and how will the oil film formation and performance be monitored? 

We have industrial support from Victrex (the world leader with 75% market share in PEEK tribological polymer, who will supply test samples), ORE Catapult (will supply wind loading data, and the potential for field trials), Kluber (lubricant manufacturer who will supply WT greases), Waukesha Dover Precision (major bearing manufacturer, who will guide design process and provide samples).  

You would be joining the Leonardo Centre for Tribology which is an active and friendly group. There are ~25 PhD students working on machine elements, tribology, lubrication, and sensor systems for wind, auto, rail and energy applications. The group has well equipped labs and its own office space for the PhD students.