Research Papers: Gas Turbines: Turbomachinery

Effect of Flow Inclination on Wind Turbine Performance

[+] Author and Article Information
Christina Tsalicoglou

e-mail: ctsalico@student.ethz.ch

Sarah Barber

e-mail: barbers@lec.mavt.ethz.ch

Ndaona Chokani

e-mail: chokani@lec.mavt.ethz.ch

Reza S. Abhari

e-mail: abhari@lec.mavt.ethz.ch
Laboratory for Energy Conversion,
Department of Mechanical and Process Engineering,
ETH Zurich,
8092 Zurich, Switzerland

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received June 18, 2012; final manuscript received June 29, 2012; published online October 11, 2012. Editor: Dilip R. Ballal.

J. Eng. Gas Turbines Power 134(12), 122601 (Oct 11, 2012) (8 pages) doi:10.1115/1.4007323 History: Received June 18, 2012; Revised June 29, 2012

This work examines the effect of flow inclination on the performance of a stand-alone wind turbine and of wind turbines operating in the wakes of upstream turbines. The experimental portion of this work, which includes performance and flowfield measurements, is conducted in the ETH dynamically-scaled wind turbine test facility, with a wind turbine model that can be inclined relative to the incoming flow. The performance of the wind turbine is measured with an in-line torquemeter, and a 5-hole steady-state probe is used to detail the inflow and wake flow of the turbine. Measurements show that over a range of tip-speed ratios of 4–7.5, the power coefficient of a wind turbine with an incoming flow of 15 deg inclination decreases on average by 7% relative to the power coefficient of a wind turbine with a noninclined incoming flow. Flowfield measurements show that the wake of a turbine with an inclined incoming flow is deflected; the deflection angle is approximately 6 deg for an incoming flow with 15 deg inclination. The measured wake profiles are used as inflow profiles for a blade element momentum code in order to quantify the impact of flow inclination on the performance of downstream wind turbines. In comparison to the case without inclination in the incoming flow, the combined power output of two aligned turbines with incoming inclined flow decreases by 1%, showing that flow inclination in complex terrain does not significantly reduce the energy production.

Copyright © 2012 by ASME
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Fig. 1

Setup of the subscaled wind turbine test facility

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Fig. 2

Geometry of the two turbines at LEC’s dynamically scaled wind turbine test facility (a) DT, used for performance measurements and (b) UT, used for flowfield measurements

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Fig. 3

Five-hole steady-state probe and coordinate system used for the flowfield measurements. Probe diameter 5 mm.

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Fig. 4

Measurement points for the full plane steady-state flowfield measurements, shown as filled circles over the rotor plane

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Fig. 5

Two-turbine configuration in inclined flow. Either a turbine or the probe can be mounted at the position of the downstream turbine.

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Fig. 6

cp versus tip-speed ratio curve for (a) turbulence intensity TI=0% and (b) turbulence intensity TI=2.5%

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Fig. 7

Comparison of the power yield in yaw and in inclination

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Fig. 8

Velocities at the centerline downstream of the DT as a function of x/D, for γ=0 deg and 15 deg

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Fig. 9

Side view schematic of the wake expansion and the deflection due to flow inclination at angle γ. The rotor and tower are shown to be at x/D=0.

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Fig. 10

Contours of axial velocities downstream of the turbine (flow inclination γ=15 deg) at (a) x=3D and (b) x=6D. The velocities are normalized with respect to the freestream axial velocity.

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Fig. 11

Contours of yaw angles (flow inclination γ=15 deg) at (a) x=3D and (b) x=6D

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Fig. 12

In-plane velocity vectors superimposed on contours of the in-plane velocity. The freestream flow inclination angle (γ=15 deg) is subtracted in the determination of the in-plane velocity vectors. The contours of the in-plane velocities are normalized magnitudes, |uin-plane|/uref.

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Fig. 13

In-plane velocity vectors superimposed on contours of in-plane velocity at x=6.5D. The in-plane velocities are normalized magnitudes |uin-plane|/uref. The flow inclination is zero degrees (γ=0 deg).

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Fig. 14

Power yield versus inclination angle γ

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Fig. 15

Power loss components for one turbine in different cases, termed as in Table 3

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Fig. 16

Estimated combined power yield of n aligned wind turbines on 0 deg and 15 deg slopes




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