Helical vortex theory and blade element analysis of multi‐bladed windmills

John, Itoje H.; Wood, David Murakami; Vaz, Jerson Rogério Pinheiro

doi:10.1002/we.2796

Cited by 5 publications

(4 citation statements)

References 28 publications

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“…Since modern turbines have λ opt ∼ 7 − 9, the highthrust region normally spans high values of λ: as a rule of thumb λ R ≈ 2λ opt . This approximate relation holds for multiblade windmills where λ opt ∼ 1, as shown in Figure 5 of John et al (2023), and the experiments of Krogstad and Adaramola (2012) and Krogstad and Eriksen (2013) that we consider below, for which λ opt ∼ 6. Furthermore, it is normal for C T to increase monotonically in this region when λ opt is large.…”

Section: Introductionmentioning

confidence: 64%

“…Our revisions to BEMT apply at all values of λ including zero, but we concentrate on the high-thrust region, where BEMT is most challenged. It is further noted that John et al (2023) found conventional BEMT accurately predicted λ R for a model of a lowspeed, multi-bladed water pumping windmill where λ R ≈ 2 and the runaway C TR increased from 0.1 to 0.5 as N increased from 3 to 24. The implication is that the present revisions are not critical at low λ.…”

Section: Introductionmentioning

confidence: 82%

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A revision of blade element/momentum theory for wind turbines in their high-thrust region

Wood,

Golmirzaee

2023

Front. Energy Res.

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Modern horizontal-axis wind turbines produce maximum power at an optimal tip speed ratio, λopt, of around 7. This is also the approximate start of the high-thrust region, which extends to runaway at λR ≈ 2λopt where no power is produced and the thrust is maximized. The runaway thrust coefficient often exceeds unity. It is well known that the conventional axial momentum equation must be modified whenever the thrust coefficient approaches unity, but most past modifications have no sound physical basis. Our main revision is to include the “wake vorticity” term in the axial momentum balance. This term is related to blade element drag and acts to decouple the thrust from the induced axial velocity when it becomes large near the edge of the rotor as the runaway is approached. The wake vorticity term dominates the axial momentum equation in these conditions and leads to estimates of power and thrust that are consistent with the limited amount of high-quality experimental data in the high-thrust region.

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Section: Introductionmentioning

confidence: 64%

Section: Introductionmentioning

confidence: 82%

A revision of blade element/momentum theory for wind turbines in their high-thrust region

Wood,

Golmirzaee

2023

Front. Energy Res.

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“…As the rotor extracts kinetic energy from the flow, the stream velocity heavily decreases along the rotor center line due to the blockage effect imposed by the rotor on the diffuser-confined flow. According to [30], the blockage effect can significantly impact the rotor performance as it alters the flow around the blades, and it is a function of the number of blades [31]. The calculated turbulent kinetic energy (TKE) is shown in Figure 12 on a logarithmic scale.…”

Section: Performance Of the Diffuser-augmented Hydro Turbinementioning

confidence: 99%

Assessment of a Diffuser-Augmented Hydrokinetic Turbine Designed for Harnessing the Flow Energy Downstream of Dams

2023

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Harnessing the remaining energy downstream of dams has recently gained significant attention as the kinetic energy available in the water current is considerable. This work developed a novel study to quantify the energy gain downstream of dams using a horizontal-axis hydrokinetic turbine with a diffuser. The present assessment uses field data from the Tucuruí Dam, where a stream velocity of 2.35 m/s is the velocity at which the highest energy extraction can occur. In this case, a 3-bladed hydrokinetic turbine with a 10 m diameter, shrouded by a flanged conical diffuser, was simulated. Numerical modeling using computational fluid dynamics was carried out using the Reynolds averaged Navier–Stokes formulation with the κ – ω shear stress transport as the turbulence model. The results yield good agreement with experimental and theoretical data available in the literature. Moreover, the turbine power coefficient under the diffuser effect could increase by about 55% for a tip speed ratio of 5.4, and the power output increased by about 1.5 times when compared to the same turbine without a diffuser. Additionally, as there are no hydrokinetic turbines installed downstream of dams in the Amazon region, the present study is relevant as it explores the use of hydrokinetic turbines as an alternative for harnessing the turbined and verted flow from dams. This alternative may help avoid further environmental impacts caused by the need for structural extensions.

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“…Although there are several publications on the design and performance analysis of small horizontal-axis wind turbines [16,17], further investigation is required to examine the effects of swept blades on the starting and operational performance of small horizontal-axis wind turbines. The authors are unaware of any study on this regard.…”

Section: Introductionmentioning

confidence: 99%

Quasi-Steady Analysis of a Small Wind Rotor with Swept Blades

et al. 2023

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It is well known that wind power generation addresses the energy needs of small and remote populations as one of the alternatives to petroleum-based energy’s greenhouse effect. Although there are several publications on rotor design and performance analysis, more should be written about the starting of wind turbines, mainly the small ones, where starting can be a big issue. The present paper evaluates the impact of the swept blade angle on the aerodynamic torque, thrust force, and minimal wind speed required to start the operation of a compact horizontal-axis wind turbine. It presents a novel investigation of the influence of swept rotor blades on the starting performance of a turbine drivetrain. The methodology uses the blade element moment theory coupled to Newton’s second law, in which Palmgren’s extended approach is employed. When the proposed methodology is compared to the experimental data available in the literature, it exhibits good agreement. However, when the wind turbine starts to run, the results show that swept blades do not always enhance the torque coefficient or reduce the thrust force as indicated in some scientific papers. For backward-swept blades, the maximum value decreases 4.0%. Similar behavior is found in thrust force for forward-swept blades. Therefore, more study is required to evaluate many blade foils in several operational environments to confirm this statement.

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Helical vortex theory and blade element analysis of multi‐bladed windmills

Cited by 5 publications

References 28 publications

A revision of blade element/momentum theory for wind turbines in their high-thrust region

A revision of blade element/momentum theory for wind turbines in their high-thrust region

Assessment of a Diffuser-Augmented Hydrokinetic Turbine Designed for Harnessing the Flow Energy Downstream of Dams

Quasi-Steady Analysis of a Small Wind Rotor with Swept Blades

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