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Research Papers: Gas Turbines: Turbomachinery

Experimental Investigation on the Wake Characteristics and Aeromechanics of Dual-Rotor Wind Turbines

[+] Author and Article Information
Ahmet Ozbay

Department of Aerospace Engineering,
Iowa State University,
2271 Howe Hall, Room 1200,
Ames, IA 50011-2271

Wei Tian

Department of Aerospace Engineering,
Iowa State University,
2271 Howe Hall, Room 1200,
Ames, IA 50011-2271
e-mail: tianwei@sjtu.edu.cn

Hui Hu

Department of Aerospace Engineering,
Iowa State University,
2271 Howe Hall, Room 1200,
Ames, IA 50011-2271
e-mail: huhui@iastate.edu

1Corresponding author.

Contributed by the Turbomachinery Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received July 15, 2015; final manuscript received August 10, 2015; published online October 13, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 138(4), 042602 (Oct 13, 2015) (15 pages) Paper No: GTP-15-1310; doi: 10.1115/1.4031476 History: Received July 15, 2015; Revised August 10, 2015

An experimental study was carried out to investigate the aeromechanics and wake characteristics of dual-rotor wind turbines (DRWTs) in either co-rotating or counter-rotating configuration, in comparison to those of a conventional single-rotor wind turbine (SRWT). The experiments were performed in a large-scale aerodynamic/atmospheric boundary layer (AABL) wind tunnel, available at Iowa State University with the oncoming atmospheric boundary-layer (ABL) airflows under neutral stability conditions. In addition to measuring the power output performance of DRWT and SRWT models, static and dynamic wind loads acting on those turbine models were also investigated. Furthermore, a high-resolution digital particle image velocimetry (PIV) system was used to quantify the flow characteristics in the near wakes of the DRWT and SRWT models. The detailed wake-flow measurements were correlated with the power outputs and wind-load measurement results of the wind-turbine models to elucidate the underlying physics to explore/optimize design of wind turbines for higher power yield and better durability.

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Figures

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Fig. 1

Test section of the AABL wind tunnel

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Fig. 2

Measured flow characteristics of the oncoming flow for the present study: (a) mean streamwise flow velocity and (b) turbulence intensity

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Fig. 3

Schematic of the SRWT model used in the present study

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Fig. 4

Schematic of the DRWT models used in the present study: (a) co-rotating DRWT and (b) counter-rotating DRWT

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Fig. 5

Experimental setup used for PIV measurements

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Fig. 6

Variations of the normalized power outputs of the turbine models as a function of the applied electric load

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Fig. 7

Ratios of the downwind (back) rotor and overall power outputs of the counter-rotating DRWT model to those of the co-rotating DRWT model

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Fig. 8

Measured azimuthal (swirling) velocity profiles in the wake flows behind the SRWT and DRWT models at the downstream location of X/D = 0.5 and X/D = 2.0

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Fig. 9

Ensemble-averaged velocity, U/Uhub, and velocity deficit, ΔU/Uhub, distributions in the wakes behind the SRWT and DRWT models: (a) U/Uhub, SRWT, (b) ΔU/Uhub, SRWT, (c) U/Uhub, co-rotating DRWT, (d) ΔU/Uhub, co-rotating DRWT, (e) U/Uhub, counter-rotating DRWT, and (f) ΔU/Uhub, counter-rotating DRWT

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Fig. 10

Wake-induced TKE distributions (ΔTKE/U2hub) in the wakes behind the SRWT and DRWT models: (a) SRWT, (b) co-rotating DRWT, and (c) counter-rotating DRWT

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Fig. 11

Reynolds shear stress, Ruv/U2hub, distributions in the wakes behind the SRWT and DRWT models: (a) SRWT, (b) co-rotating DRWT, and (c) counter-rotating DRWT

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Fig. 12

Phase-locked PIV measurement results of the wake flow behind the SRWT model: normalized streamwise velocity deficit (left), vorticity (middle), and swirling strength (right): (a) at the phase angle of ϕ = 0.0 deg, (b) at the phase angle of ϕ = 30.0 deg, (c) at the phase angle of ϕ = 60.0 deg, and (d) at the phase angle of ϕ = 90.0 deg

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Fig. 13

The phase-locked PIV measurement results of the wake flow behind the co-rotating DRWT model: normalized streamwise velocity deficit (left), vorticity (middle), and swirling strength (right): (a) at the phase angle of ϕ = 0.0 deg, (b) at the phase angle of ϕ = 30.0 deg, (c) at the phase angle of ϕ = 60.0 deg, and (d) at the phase angle of ϕ = 90.0 deg

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Fig. 14

The phase-locked PIV measurement results of the wake flow behind the counter-rotating DRWT model: normalized streamwise velocity deficit (left), vorticity (middle), and swirling strength (right): (a) at the phase angle of ϕ = 0.0 deg, (b) at the phase angle of ϕ = 30.0 deg, (c) at the phase angle of ϕ = 60.0 deg, and (d) at the phase angle of ϕ = 90.0 deg

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Fig. 15

The relative velocity vectors in the vicinity of vortices in the wake of the SRWT model: (a) tip vortex, and (b) root vortex

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