Publication: Elucidation of the rotor aerodynamics and performance of a self-starting darrieus turbine
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Date
2023-03-01
Authors
Selvarajoo, Shaza Rae
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Abstract
Global warming and over consumption of non-renewable energy sources are amongst the grand challenges facing humanity in the 21st century, where wind turbines provide an alternative source of power. However, wind flows in nature fluctuate greatly, which causes Darrieus turbines, a subset of vertical-axis turbines, to be in protracted transient modes that reduce their overall efficiency. The complex flow patterns surrounding these rotors, due to their interactions with multiple shed vortices, further exacerbate the reduced efficiency and complicate the elucidation of the rotor aerodynamics. In this work, a three-bladed H-Darrieus rotor was simulated numerically via a combination of the lifting line theory and vortex wake model, with their algorithms embedded in a software named QBlade. These algorithms model the entire self-starting process that consists of the linear and acceleration phases. Darrieus rotors face difficulty self-starting because of dead bands in the linear phase, where each dead band is a region when a net negative torque is generated over a single cycle due to a reverse dynamic stall. In the accelerated phase, significant torque is generated due to forward dynamic stalls, which then cause the rotor to enter the steady phase. The work herein elucidates the aerodynamics of a Darrieus rotor during self-start, via the use of a novel and newly developed in-house software named DRAFA. This software allows users to rapidly analyse Darrieus turbines, which significantly reduces the time taken to process raw data into insightful data. Its most significant aspect is the production of turbine vector diagrams which allow users to intuitively visualize the complex and spatio-temporally evolving inflow and force vectors on the turbine blades.