First assessment of the magnetic-hydrostatic main bearing proposed for the duck wave-energy converter

A preliminary assessment is made of the novel large-scale bearing proposed for the 'duck wave energy converter. The bearing is designed to work by combining the principles of self-pressurised fluid lubrication, and passive permanent magnet repulsion, and these two topics are dealt with in approximately equal measure. Following a description of the specification and design of the bearing, a performance analysis is made, based on standard lubrication theory assumptions. Although over-simplified, this predicts favourable characteristics, including high load capacity, low fluid pressures, and low friction. The analytical assumptions are then reassessed, and those characteristics of bearing performance not predicted from lubrication theory, namely turbulence and fluid inertia, are examined. Both are found to enhance load capacity, with the most significant effect arising as an indirect consequence of fluid inertia. The indirect influence of fluid inertia is described, and experimental evidence presented of its magnitude, and its asymmetric characteristic: the experimental model used is that of converging/diverging radial flow between plane parallel discs. The permanent magnet repulsion system, and the topic of magnet geometry optimisation are discussed. After examining the correct analytical models and optimisation procedures, several mathematical analyses are detailed. The results of these include theoretical results for the maximum force, force/unit volume, and stiffness/unit volume which can be exerted by two-dimensional rectangular magnets, and the maximum force and force/unit volume for three-dimensional magnets. Experimental results are included which verify the theoretical predictions. The thesis concludes with a short discussion on the overall feasibility of the proposed bearing.