An experimental characterization of the friction coefficient of a wind turbine gearbox lubricant

Abstract

In this study, a method to predict the contact friction coefficients at the rolling‐sliding contacts of isotropic superfinished and axially ground gear and bearing surfaces in wind turbine gearboxes is proposed. A two‐disc test rig was used to measure friction coefficient values within a slide‐to‐roll ratio range of −0.8 to 0.8, rolling velocities of 2 to 12 m/s, at oil temperatures of 50°C, 70°C, and 100°C and Hertzian contact pressures of 1.2, 1.6, and 2.0 GPa. A polyalphaolefin (PAO) International Standards Organization (ISO) viscosity grade (VG) 320 was the lubricant. Data from 90 individual friction coefficient tests were combined to develop two closed‐form friction coefficient formulae. A multivariable linear regression analysis was used to derive the regressed formulae. Using the developed regressed formulae, the predicted friction values follow the trend of measured values at all of the operating conditions. The results show that the regressed formulae are close to experimental friction coefficient values. The friction coefficient predictions confirm that the regressed formulae are capable of simulating contact friction values for the lubricated contact conditions considered.

Description of an HAWT hub enabling teetering about two out‐of‐plane axes with modeling showing significant reductions in cyclic behavior and fatigue due to turbulence and wind shear

“…With blades, some other factors include delamination, 22 driving rain causing leading edge erosion 23,24 lightning, ice, hail, and sand. With bearings, other factors include poor lubrication, 25 metal defects, 26 misalignment, 27 and rotor imbalances due to snow and ice on blades.…”

Minimum Friction Losses in Planetary Stages of Wind Turbine Gearboxes

“…e instantaneous friction coefficient between gear teeth is not uniform along the path of contact [39,40], but for evaluating the friction power losses an average friction coefficient as given by ( 7) is sufficient. e variation of the instantaneous friction losses along the path of contact cannot be properly defined with such a constant friction coefficient, but it is evident that these variations have no influence on the power of the cooling system, whose reduction is the objective of this analysis.…”

Enhanced tribological properties of wind turbine engine oil formulated with flower-shaped MoS2 nano-additives

“…In particular, frequent critical failures and extensive maintenance work in wind turbines, mainly on gearboxes and bearing components, account for about 13% of total maintenance costs [4,5]. The origin of these failures is related to severe and unstable operating conditions such as high loads, extreme temperature, etc., which cause irreversible cumulative damage to mechanical components (micro-pitting, cracking, false brinelling and fretting corrosion, gear scuffing, …) and thus increase energy losses through heat generation [6]. Therefore, one of the most suitable and effective ways to overcome these failures and increase both economic and long-term benefits is the development of a new generation of lubricants that can ensure a long life and high efficiency of machine components and, consequently, a reduced maintenance time.…”