Strength in Flexibility; Research into Innovative Flexible Bearing Designs for Wave Convertor Permanent Magnet Generators

Bedford, Adam (2011) Strength in Flexibility; Research into Innovative Flexible Bearing Designs for Wave Convertor Permanent Magnet Generators. Doctoral thesis, Lancaster University.

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Originally this research was to investigate the use of hydrostatic bearings in large linear machines, such as linear generators, and determine their viability in a power generation context. It quickly became clear that it was possible to make hydro-static bearings viable, however the methods employed to do so gave rise to new possibilities which altered the scope of the research. The overall aim of the research has become to look at flexible construction, using modular generation units, as a means of creating more reliable and cost effective generators.

The methods employed to do this involved modularising the generator's structure. Each module then acts as a generator in its own right transferring its power to the parent machine. The potential for each module design was assessed based on its losses, due to the bearings, and its economic potential, such as how it impacted the operation and maintenance costs or transport costs and consideration of how each design affected the power density of the parent machine.

The basic structural analysis showed that, of the arrangements tried, there was a distinct advantage to restricting the number of bearings because it reduces energy losses. This is particularly true of designs that take advantage of the MMA concepts. The magnitude of the forces within the generators, during operation, lead to the creation 2-stage bearing and MMA concepts. The key reasons for them being to reducing dynamic forces within the generator and increase tolerance to design flaws and damage. Reducing the dynamic forces reduces losses in all types of bearings improving overall efficiency. Not all the concepts present in this document show commercial promise, however from the basic principles used to understand their working, there are some whose potential is clear. In general the modules have reduced the weight necessary to operate a successful generator and reduced the bearing losses no matter the type of bearing being used. Predicted force reductions mean that less strength critical and more cost effective materials can be used in the machines construction.

Given that the original scope of the research was to assess a single type of bearing
it has come a long way to incorporate construction methods that will reduce operation and transport costs, as well as being more efficient on some of the construction materials. The final module designs show great promise to increase the power density of generators whilst making them easy to maintain. Although hydrostatic bearings provide excellent lubrication the basic analysis performed herein shows that their energy consumption exceeds the energy loss of normal roller bearings reducing overall generator efficiency. The modular constructions presented may not provide a great jump in efficiency over previous designs however they do show a way to simplify operation and maintenance costs improving overall commercial viability.

All 3D/CAD models contained herein were created by the author for this work unless otherwise stated/referenced.

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