Fatigue Analysis of a Diffuser-Augmented Fiber-Composite Tidal Turbine

This study investigates the structural performance of the diffuser-augmented horizontal axis tidal turbine (DATT) by examining the fatigue performance of its blades on different hydrofoil diffuser design parameters. While the diffuser augmentation relieves the issue of requiring a larger turbine to produce the same amount of power, it also increases the structural load on the turbine blades due to increased power performance. Currently, there is little literature on the structural response to increased load in DATT systems. Hence, this study examines the diffuser hydrofoil design parameters, namely, camber and orientation angle, for the fatigue performance of the turbine blades. In the first phase, the Finite Element (FE) model is created and verified, and the spectrum load cases are generated to simulate dynamic loading. Secondly, the FE model undergoes a static test, and various load spectra are applied for fatigue analysis. Glass Fiber Reinforced Polymer (GFRP) and Carbon Fiber Reinforced Polymer (CFRP) composite materials show satisfactory fatigue performance. Lastly, the third phase determines the level of sensitivity of the angle diffuser and camber to the fatigue performance, wherein the former results in a Sobol index of around 0.95, indicating a high significance level, while the latter parameter results in around 0.05, indicating non-significance. This study concludes that using fiber-reinforced polymer materials is satisfactory in tidal fatigue load application. The understanding of the fatigue behavior of DATT enables the development of better designs and saves on the cost of prototype development. Future work on more design parameters is recommended for optimization and sensitivity studies investigation.