High-viscous vegetable based oils as substitutes of mineral oils for their use in wind turbines


X. Paredes1, M. Comunas1, A. Pensado1 and J. Fernandez1

1University of Santiago de Compostela, Spain

Keywords: pressure
property: viscosity
material: vegetable oils

The main objective of this work was to study the viscous behavior of new environmentally friendly lubricants based on high oleic sunflower oils for their use as lubricants for gearboxes in wind turbines. Apart from their biodegradability, the advantages of vegetable oil-based fluids are their low toxicity, low volatility, high shear stability, high flash point and viscosity index, as well as low health and safety risks. Furthermore, their polar ester groups are able to adhere to metal surfaces and, therefore, possess good boundary lubrication properties. However nowadays, besides their higher cost, vegetable oils present some disadvantages such as their poor low-temperature properties, reduced operating temperature ranges, moderate oxidative stability and their availability in limited viscosity ranges making necessary the development of additives to overcome these problems. In wind turbine gearboxes, the operating temperature is around 343.15 K and pressures up to 2 GPa. The suitable viscosity of the gear oils for this application is around 300 mPa·s at 313.15K and 0.1MPa. The main problem in measuring the viscosity of such oils at high pressure is the lack of viscosity standards, for these pressure-viscosity conditions. This issue is also critical in the measurements at deepwater conditions in the new oil reservoirs of Mexican Gulf. In this work, a falling body viscometer has been used to perform the viscosity measurements for three formulated vegetable oils and a biodegradable lubricant at 313.15, 343.15 K and 363.15 up to 250 MPa. Dipentaerythritol hexaisononanoate (DiPEiC9) has been used as standard fluid. The results show that for the vegetable oils the viscosity increases with the pressure with a slope more smooth than those of the reference mineral oils that are being used in the gearboxes. This fact leads to a diminution of film thickness, of the energy losses and likely to an increase of the gears’ life due to lower sub-surface stress and spikes pressure.

We express our gratitude to Dr. K.N. Harris (University of New South Wales, Australia) for providing us unpublished DiPEiC9 viscosity values. This work is being supported by Spanish Ministry of Science and Innovation and the UE Feder Program under PSE-420000-2008-4 project. We are very grateful with the partners of this project for providing the lubricants.


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