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

Abstract

Abstract A three‐bladed, dual‐axis teetering hub (3T) has been developed and compared to a three‐bladed rigid hub (3R) using computer modeling. Both hubs were fitted to a hypothetical 5‐MW offshore wind turbine mounted on an offshore floating platform. Cyclic analysis showed the 3T hub significantly reduced the impact of wind shear on the blades and virtually eliminated the impact of both turbulence and wind shear on the main shaft bearing and yaw bearing. Lifetime fatigue studies for the two hubs were performed using a rainflow‐counting program at various levels of turbulence and wind shear. Studies showed the significant reductions in cyclic variation provided by the 3T hub resulted in significant reductions in lifetime fatigue in comparison to the 3R hub. Simulations with the 3T hub showed an increase in turbulence caused a very small increase in blade fatigue but no increase in fatigue for the main shaft bearing and yaw bearing. In contrast, fatigue studies with the 3R hub showed an increase in turbulence caused significant damage to the blades and a combined increase in turbulence and wind shear caused extremely significant damage to the blades. This paper introduces a recently patented hub design that is superior to the ball‐and‐socket design described in a prior paper by this author.

Keywords

• 5‐MW offshore floating wind turbine
• blade fatigue
• cyclic analysis
• dual axis teetering
• lifetime fatigue study
• three bladed teetering hub