Supersonic particle deposition coatings for improved Tribological performance of offshore wind turbine gears

Abstract

Tribology of renewable energy systems such as for wind turbines is a relatively new field and the study of which has a potential to reduce turbine component failures and turbine downtime. In this paper we focus on offshore wind turbines tribological issues in comparison to on-shore counterparts and address a coating deposition method which has potential to be used in wind turbine industry. In this paper we look into the turbine drivetrain parts such as gears. To prove the effect of severe offshore conditions a simulation of wind turbine gear loads using a FAST analysis of an NREL 5MW reference wind turbine has been shown. In this simulation a time varying torque is used to simulate the hertzian stresses at the planet and sun gear mesh of the 1st planetary gear stage. Results show increase in the contact stresses when compared to onshore counterparts, due to the additional hydrodynamic loading in the offshore wind turbines. This means that the gears would undergo accelerated failure when compared to gears used in onshore type turbines. In addition to that, inaccessibility of the turbine for maintenance will increase the cost of energy. To mitigate these effects tribological coatings can be a solution to reduce gearbox failures and thus reduce turbine downtime. The selection of such technologies not only depend on coating material but the coating process itself which dictates the coating properties and thus the performance of the mating surfaces. In this paper we are going to discuss about supersonic particle deposition which is otherwise called cold spray coating. The principle, advantages and suitability of this technology to large wind turbine gears will be discussed in detail.