Effect of aspect ratio on cross-flow turbine performance

Hunt, Aidan; Stringer, Carl; Polagye, Brian

doi:10.1063/5.0016753

Cited by 20 publications

(10 citation statements)

References 39 publications

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“…The outcome of this study is that with increasing ratio of diameter and blade span length (H/D) there is an increase in turbine power coefficient (C P ) and this was attributed to lower tip losses with growing H/D ratio and decreased circulation amount ratio for a wide range of blade span for small values of H/D. Hunt et al (2020) experimentally examined the performance of H-type VAWTs with blade end struts by varying the aspect ratio in the range of (0.95 to 1.63) and keeping all the other parameters constant. By keeping other non-dimensional parameters constant they were able to isolate the effect of aspect ratio on turbine performance.…”

Section: Case 3: Impact Of Aspect Ratiomentioning

confidence: 87%

Parked and Operating Loads Analysis in the Aerodynamic Design of Multi-megawatt-scale Floating Vertical Axis Wind Turbines

Sakib

Griffith

2021

Preprint

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Abstract. A good understanding of aerodynamic loading is essential in the design of vertical axis wind turbines (VAWTs) to properly capture design loads and to estimate the power production. This paper presents a comprehensive aerodynamic design study for a 5 MW Darrieus offshore VAWT in the context of multi-megawatt floating VAWTs. This study systematically analyzes the effect of different, important design variables including the number of blades (N), aspect ratio (AR) and blade tapering in a comprehensive loads analysis of both the parked and operating aerodynamic loads including turbine power performance analysis. Number of blades (N) is studied for 2- and 3-bladed turbines, aspect ratio is defined as ratio of rotor height (H) and rotor diameter (D) and studied for values from 0.5 to 1.5, and blade tapering is applied by means of adding solidity to the blades towards blade root ends, which affects aerodynamic and structural performance. Analyses were carried out using a three-dimensional vortex model named CACTUS (Code for Axial and Crossflow TUrbine Simulation) to evaluate both instantaneous azimuthal parameters as well as integral parameters, such as loads (thrust force, lateral force, and torque loading) and power. Parked loading is a major concern for VAWTs, thus this work presents a broad evaluation of parked loads for the design variables noted above. This study also illustrates that during the operation of a turbine, lateral loads are on par with thrust loads, which will significantly affect the structural sizing of rotor and platform & mooring components.

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Section: Case 3: Impact Of Aspect Ratiomentioning

confidence: 87%

Parked and Operating Loads Analysis in the Aerodynamic Design of Multi-megawatt-scale Floating Vertical Axis Wind Turbines

Sakib

Griffith

2021

Preprint

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“…Each turbine had a height of H = 0.23 m, diameter of D = 0.172 m, chord length of c = 0.04 m, and symmetric NACA0018 blade profile. This turbine geometry has been used in past work [42,45,35,27]. Due to the limited number of strut endplates, one turbine had struts with a NACA0008 profile, while the other used a NACA0016 profile.…”

Section: Methodsmentioning

confidence: 99%

Geometric and Control Optimization of a Two Cross-Flow Turbine Array

Scherl¹,

Strom²,

Brunton³

et al. 2020

Preprint

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Cross-flow turbines, also known as vertical-axis turbines, convert the kinetic energy in moving fluid to mechanical energy using blades that rotate about an axis perpendicular to the incoming flow. In this work, the performance of a two-turbine array in a recirculating water channel was experimentally optimized across sixty-four unique array configurations. For each configuration, turbine performance was optimized using tip-speed ratio control, where the rotation rate for each turbine is optimized individually, and using coordinated control, where the turbines are optimized to operate at synchronous rotation rates, but with a phase difference. For each configuration and control strategy, the consequences of coand counter-rotation were also evaluated. We hypothesize how array configurations and control cases influence interactions between turbines and impact array performance.

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“…VAT rotors are rectangular with a given height-to-diameter aspect ratio that can be modified, unlike HAT rotors that are circular, to provide two positive effects: at devices scale, it decreases the negative impact in performance from supporting structural elements (Hunt et al 2020); and, at array scale, the wake effects diminish as the kinetic energy removed in the horizontal plane reduces, increasing wake recovery (Boudreau and Dumas 2017;Ouro and Lazennec 2021). Furthermore, irrespective of the standalone turbine efficiency, the rectangular cross-section of VAT rotors allows to deploy two devices close to one another which induces a flow acceleration between them Posa (2019) that can increase the individual performance up to 5% (Hezaveh et al 2018).…”

Section: Introductionmentioning

confidence: 99%

Power density capacity of tidal stream turbine arrays with horizontal and vertical axis turbines

Ouro

Dené

Garcia-Novo³

et al. 2022

J. Ocean Eng. Mar. Energy

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Tidal and wind energy projects almost exclusively adopt horizontal axis turbines (HATs) due to their maturity. In contrast, vertical axis turbines (VATs) have received limited consideration for large-scale deployment, partly because of their earlier technology readiness level. This paper analyses the power density of turbine arrays comprising aligned and staggered configurations with decreasing turbine spacing of HATs and VATs with height-to-diameter aspect ratios from one to four at three real tidal sites. The VAT rotor has vertical blades extending over a portion of the water depth on a circular frame. Equivalent diameter is defined as $$D_0$$ D 0 = $$\sqrt{A}$$ A based on the projected rotor area for both VATs and HATs. The three-dimensional velocity field is computed using analytical wake models that capture cumulative wake effects. At highly energetic sites, e.g. Ramsey Sound (UK), HATs are the most suitable technology attaining power densities beyond 100 W m$$^{-2}$$ - 2 , whilst VATs provide higher power densities than HATs at those sites with low-to-medium velocities, e.g. Ría de Vigo (Spain) and Kobe Strait (Japan). At the latter site, VATs provided up to 35% larger energy yield than HATs over a 14-day tidal cycle. Our results show that VATs with height-to-diameter aspect ratios larger than three notably reduce wake effects even when deployed with a normalised turbine spacing of two $$D_0$$ D 0 , reaching an average power density capacity of 40.7 W m$$^{-2}$$ - 2 compared to HATs that attain 49.3 W m$$^{-2}$$ - 2 . This study outlines the higher efficiency of tidal stream energy compared to other renewable energy resources, e.g. offshore wind farms, reaching power densities at least one order of magnitude larger, and that VATs counterbalance their smaller individual performance with improved array synergy as wake effects are limited.

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Effect of aspect ratio on cross-flow turbine performance

Cited by 20 publications

References 39 publications

Parked and Operating Loads Analysis in the Aerodynamic Design of Multi-megawatt-scale Floating Vertical Axis Wind Turbines

Parked and Operating Loads Analysis in the Aerodynamic Design of Multi-megawatt-scale Floating Vertical Axis Wind Turbines

Geometric and Control Optimization of a Two Cross-Flow Turbine Array

Power density capacity of tidal stream turbine arrays with horizontal and vertical axis turbines

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