Arash Golchin, PhD in machine elements at Luleå University of Technology. Photo: Ted Karlsson.

A step closer to oil-free systems in hydropower

Published: 22 May 2015

In a new doctoral thesis at Luleå University of Technology, Arash Golchin presents how polymer based bearing materials can be used for water-based lubrication in hydropower production.

The mineral and synthetic oils that are currently used for lubrication of bearings in hydropower plants introduce a risk of negative environmental impact if these lubricants leak into the water. The idea of using water as lubricant was therefore pursued to achieve oil-free systems in hydropower production.

Gives practical guidelines

– Development of an oil-free bearing system poses some challenges, such as the choice of the materials. My research was to investigate the tribological behavior (friction and wear) when polymers (plastics) are being used as bearing materials in hydropower plants, says Arash Golchin, PhD in Machine Elements at Luleå University of Technology.

– My results show practical guidelines for the industry and an analysis of the tribological performance of polymers and related mechanisms involved in the presence of lubricants.

– The results show that a low friction can be obtained with unfilled polymers which show a low wettability and solubility in water. It was also shown that using a smoother shaft can be very beneficial for reducing the dynamic friction of the polymer bearings; however, depending on the bearing material, this can result in significant increase in start-up friction which is a critical issue in some applications such as pumped-storage hydropower plants.

Stronger with carbon

– Further investigations also showed good potential of using short carbon fibers for enhancing the friction and wear behaviour of the polymer composites in water lubricated contacts. Overall, the materials’ friction and wear behavior is largely dependent on the system, so large-scale experiments in actual bearing configurations are needed to confirm my results.

The research has been sponsored by STandUp for Energy, the Swedish Energy Agency and the Swedish Agency for Economic and Regional Growth.