Fatigue life estimation of hydrokinetic turbine blades

Abstract

Fatigue analysis of hydrokinetic blades is essential as they are subjected to dynamic loads during their operation. This makes fatigue life estimation very important during turbine design. Therefore, this work investigates fatigue life of hydrokinetic turbine blades placed downstream of a hydroelectric power plant. The adopted methodology requires that variations in velocity, load, and stress need to be well established. Historical data of the river at the site are used as reference for variation in flow velocity. The blade element theory is implemented to calculate loads, while stresses are estimated from a finite element model. The S-N method, the rainflow count, and the Palmgren–Miner rule are used to calculate fatigue. This whole process is facilitated by the creation of computational tools to automate different steps. As a result, a life of approximately 20 years is predicted for the blade, neglecting the turbulence that occurs in the speed of the river. When considering a turbulence of 5%, the estimation is reduced to 17 years, indicating a reduction of 15% in life. The complete codes can be downloaded from https://github.com/engsergiocustodio/fatigueblades.