Testing and modelling of a 2.5 MW wind turbine gearbox: Influence of lubricant formulation

Abstract

This study aimed to evaluate the efficiency of different ISO VG 320 oil formulations used in a 2.5 MW wind turbine gearbox. Two commercially available lubricants, a mineral oil and a polyalphaolefin (PAO) lubricant, were tested under realistic operating conditions using a customized test rig. Measurements showed that the overall efficiency of the mineral lubricant was higher than that of the PAO lubricant, but the difference was only 0.1% in degree of efficiency. Detailed oil analysis revealed that the mineral lubricant generated more wear particles. A power loss model was also implemented to predict the efficiency of the gearbox, and the results of the model were found to be in agreement with the experimental results. The study concluded that the mineral oil presented higher efficiency than the PAO oil due to its lower viscosity within the narrow operating temperature range imposed on the gearbox. Nevertheless, it is important to note that the observed differences in efficiency may be attributed, in part, to measurement uncertainties and the fact that the mineral lubricant has 10% lower viscosity at the operating temperature compared to the PAO lubricant.