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Research Papers: Alternative Energy Sources

Blade Element Momentum Study of Rotor Aerodynamic Performance and Loading for Active and Passive Microjet Systems

[+] Author and Article Information
Owen F. Hurley

Mechanical and Aerospace Engineering,
University of California, Davis,
One Shields Avenue,
Davis, CA 95616

Raymond Chow

Mechanical and Aerospace Engineering,
University of California, Davis,
One Shields Avenue,
Davis, CA 95616

Myra L. Blaylock

Mechanical and Aerospace Engineering,
University of California, Davis,
One Shields Avenue,
Davis, CA 95616
e-mail: mlblayl@sandia.gov

Aubryn M. Cooperman

Mechanical and Aerospace Engineering,
University of California, Davis,
One Shields Avenue,
Davis, CA 95616
e-mail: amcooperman@ucdavis.edu

C. P. van Dam

Mechanical and Aerospace Engineering,
University of California, Davis,
One Shields Avenue,
Davis, CA 95616
e-mail: cpvandam@ucdavis.edu

1Present address: Bay Area Rapid Transit, Oakland, CA 94612.

2Present address: Rescale, San Francisco, CA 94105.

3Present address: Sandia National Laboratories, Livermore, CA 94550.

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received May 31, 2018; final manuscript received March 13, 2019; published online April 10, 2019. Assoc. Editor: Ryo Amano.

J. Energy Resour. Technol 141(5), 051213 (Apr 10, 2019) (8 pages) Paper No: JERT-18-1399; doi: 10.1115/1.4043326 History: Received May 31, 2018; Revised March 13, 2019

This study investigates the performance of microjets for load reduction on the NREL-5 MW wind turbine and identifies optimal system parameters. Microjets provide blowing normal to the blade surface and can rapidly increase or decrease lift on a blade section, enabling a wind turbine to respond to local, short-term changes in wind condition. As wind turbine rotors become larger, control methods that act on a single blade or blade section are increasingly necessary to reduce critical fatigue and extreme loads. However, microjets require power to operate, and thus, it is crucial that the fatigue reduction justifies any energy input to the system. To examine the potential for fatigue reduction of a range of potential microjet system configurations, a blade element momentum (BEM) code and a flow energy solver were used to estimate the energy input and the change in primary fatigue metrics. A parametric analysis was conducted to identify the optimal spanwise position and length of the microjets over a range of air mass flow rates. Both active and passive air supply methods were considered. A passive microjet system applied to the NREL 5-MW rotor produced a 3.7% reduction in the maximum flapwise root bending moment (FRBM). The reduction in the peak bending moment increased to 6.0% with a 5 kPa blower that consumes approximately 0.1% of the turbine output power. The most effective configurations placed microjets between the blade midspan to three-quarters span. Load reduction was achieved for both active and passive modes of air supply to the microjet system.

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Figures

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Fig. 1

Nominal effect of AALC activation on baseline lift curves: (a) flow separation control and (b) lift control devices

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Fig. 2

Velocity field and streamlines of trailing end of the NACA 0018 airfoil with microjet activated. OVERFLOW 2D simulation (hjet = 0.006c, x/c =0.90, Re = 6.6 × 105, Ma = 0.176, Cμ = 0.012) [17].

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Fig. 3

Effect of microjets on CL for NACA 0018 airfoil (Ma = 0.176, Re = 6.6 × 105, hjet= 0.006c): (a) CL versus Cμ at α = 0 deg and (b) CL versus α for unmodified airfoil and with microjets, Cμ = 0.012 [17]

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Fig. 4

Schematic layout of microjet system: (a) wind turbine rotor with air supply flow path (blue) and microjet location (red) defined by ljet and rjet and (b) partial blade cross section with internal microjet supply area shaded for NACA 643-618 (wall thickness = 0.01c)

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Fig. 5

FRBM reduction for passive microjet system (U = 11 m/s, 12.1 rpm, β = 4.9 deg, rjet = 20 – 50 m, ljet = 10−30 m) 3D and 2D contour plots

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Fig. 6

FRBM for passive microjet system (rjet = 30 m, ljet = 14 m) compared to the baseline NREL 5-MW rotor

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Fig. 7

Reduction in FRBM for passive microjet system with jet outlet on suction surface (rjet = 30 m, ljet = 14 m) compared to the baseline NREL 5-MW rotor

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Fig. 8

Increase in FRBM for passive microjet system with jet outlet on pressure surface (rjet = 32 m, ljet = 12 m) compared to the baseline NREL 5-MW rotor

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Fig. 9

Reduction in FRBM with active blowing and passive microjet systems compared to baseline NREL 5-MW rotor (rjet and ljet for each configuration are listed in Table 1)

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Fig. 10

Microjet power consumption versus wind speed, passive, and active systems. Microjet positions are those listed in Table 1, on suction surface (SS) for load reduction and pressure surface (PS) for load augmentation.

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Fig. 11

Power consumption as a percentage of turbine output versus wind speed, passive, and active systems. Microjet positions are those listed in Table 1, on suction surface (SS) forload reduction and pressure surface (PS) for load augmentation.

Tables

Errata

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