Abstract
We experimentally explored the impact of a wind turbine with truncated blades on the power output and wake recovery, and its effects within 2 × 3 arrays of standard units. The blades of the truncated turbine covered a fraction of the outer region of the rotor span and replaced with a zero-lift structure around the hub, where aerodynamic torque is comparatively low. This way, the incoming flow around the hub may be used as a mixing enhancement mechanism and, consequently, to reduce the flow deficit in the wake. Particle image velocimetry was used to characterize the incoming flow and wake of various truncated turbines with a variety of blade length ratios L / R = 0.6 , 0.7, and 1, where L is the length of the working section of the blade of radius R. Power output was obtained at high frequency in each of the truncated turbines, and also at downwind units within 2 × 3 arrays with streamwise spacing of Δ x / d T = 4 , 5, and 6, with d T being the turbine diameter. Results show that the enhanced flow around the axis of the rotor induced large-scale instability and mixing that led to substantial power enhancement of wind turbines placed 4 d T downwind of the L / R = 0.6 truncated units; this additional power is still relevant at 6 d T . Overall, the competing factors defined by the expected power reduction of truncated turbines due to the decrease in the effective blade length, the need for reduced components of the truncated units, and enhanced power output of downwind standard turbines suggest a techno-economic optimization study for potential implementation.
Highlights
Wind energy has received substantial attention in the past few decades due to its potential as a renewable energy resource
The particular wake dynamics induced by the blade length ratio, L/R, resulted in faster flow recovery in the wake to the standard turbine
It is worth noting that the impact of the momentum injection in the L/R = 0.6 case is still noticeable at the intermediate wake (Figure 5c)
Summary
Wind energy has received substantial attention in the past few decades due to its potential as a renewable energy resource. It has multiplied worldwide; in the US, wind energy increased from less than 1% to more than 6% in the last decade [1]. Particular attention has been placed on improving turbine rotors of full-scale units; investigations have ranged from the use of new materials and composites to the application of flow control strategies aimed at reducing the unsteady loading and increasing their performance. The use of winglets, pitch, and yaw controls have been widely explored as strategies to alter the turbine blade aerodynamic characteristics. Recent work by Khaled et al [5]
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