Momentum theory of diffuser augmented wind turbine.

Nagai, Minoru; Irabu, Kunio

doi:10.1299/kikaib.53.1543

Cited by 15 publications

(15 citation statements)

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“…Dick concluded this is a further confirmation to the applicability of the Betz limit to shrouded turbines when the shroud exit area is used to calculate the performance coefficient. Nagai and Irabu (1987) carried out a theoretical study on diffuser augmented wind turbines using the momentum theory. Utilizing the Bernoulli's and continuity equations along with the actuator disk model, they derived the power coefficient of a turbine as a function of the turbine load factor, diffuser area ratio, and diffuser efficiency.…”

Section: Diffuser Augmented Wind Turbinesmentioning

confidence: 99%

Effect of shroud on the performance of horizontal axis hydrokinetic turbines

2015

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Section: Diffuser Augmented Wind Turbinesmentioning

confidence: 99%

Effect of shroud on the performance of horizontal axis hydrokinetic turbines

2015

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“…If we can increase the wind speed by utilizing the fluid dynamic nature around a structure or topography, namely if we can concentrate the wind energy locally, the power output of a wind turbine can be increased substantially. Although there have been several studies of collecting wind energy for wind turbines reported so far, [1][2][3][4] it has not been an attractive research subject conventionally. Unique research that was carried out intensively in the past was the examination of a diffuser-augmented wind turbine by Gilbert et al, 1) Gilbert and Foreman, 2) and others around 1980.…”

Section: Introductionmentioning

confidence: 99%

Development of a High-Performance Wind Turbine Equipped with a Brimmed Diffuser Shroud

Ohya

Karasudani

Sakurai

et al. 2006

Trans. Japan Soc. Aero. S Sci.

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We have developed a new wind turbine system that consists of a diffuser shroud with a broad-ring brim at the exit periphery and a wind turbine inside it. The brimmed-diffuser shroud plays the role of a device for collecting and accelerating the approaching wind. Emphasis is placed on positioning the brim at the exit of the diffuser shroud. Namely, the brim generates a very low-pressure region in the exit neighborhood of the diffuser by strong vortex formation and draws more mass flow to the wind turbine inside the diffuser shroud. To obtain a higher power output of the shrouded wind turbine, we have examined the optimal form for the brimmed diffuser, such as the diffuser open angle, brim height, hub ratio, centerbody length, inlet shroud shape and so on. As a result, a shrouded wind turbine equipped with a brimmed diffuser has been developed, and demonstrated power augmentation for a given turbine diameter and wind speed by a factor of about five compared to a standard (bare) wind turbine.

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“…The tested parameter ranges are as follows: Re = 2.0×10 3 -1.3×10 4 , d/t = 4.0 -10.0 and l/t = 1.0 -10.0.…”

Section: Resultsmentioning

confidence: 99%

“…Consdering the independence of C pb from Re as shown in Subsection 3.2, we can regard C pb as a function of not Re, but both d/t and l/t. The function is given by (25) 2D prism (d/t = ∞), Re = 2.0×10 4 − 6.0×10 4 Okajima et al (1984) (26) , (1990) (27) 2D prism (d/t = ∞), Re = 5.0×10 3 Higuchi et al (2008) (24) Rod (d/t = 1.0), Re = 5.0×10 4 which is described by solid lines in Fig. 5.…”

Section: Base-suction Coefficientmentioning

confidence: 98%

“…1.3×10 4 , d/t = 4.0 -10.0 and l/t = 1.0 -10.0, where Re, d, t and l are the Reynolds number, mean diameter, thickness and length of the pipe, respectively. Then, we conduct (1) base-pressure measurements, (2) velocity-fluctuation measurements using a hot-wire anemometer and (3) flow visualisations by a smoke-wire method with PIV analyses, where we take consecutive picutures using a high-speed camcorder to obtain quantitative flow-field information such as velocity vector and vorticity.…”

Section: Introductionmentioning

confidence: 99%

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High-Reynolds-Number Flow past a Pipe

Hirata

Sakata

Yajima

et al. 2013

JFST

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The present aim is to reveal the flow past a pipe which is immersed parallel to the mainstream at high Reynolds numbers. In a wind tunnel, we carry out (1) base-pressure measurements, (2) velocity-fluctuation measurements using a hot-wire anemometer and (3) flow visualisations by a smoke-wire method with PIV analyses, where we take consecutive picutures using a high-speed camcorder to obtain quantitative flow-field information such as velocity vector and vorticity. The tested parameter ranges are as follows: Re = 2.0×10 3 -1.3×10 4, d/t = 4.0 -10.0 and l/t = 1.0 -10.0, where Re, d, t and l are the Reynolds number, mean diameter, thickness and length of the pipe, respectively. As a result, the Re effects are negligible. The base-suction coefficient C pb monotonically decreases with decreasing d/t, or with increasing l/t. We propose a unified formula to predict C pb , which are consistent with both a two-dimensional prism and a rod for l/t < 4.0 in addition to a ring. In contrast, the Strouhal number St almost coincides with that for a two-dimensional prism at any l/t, if we can detected any dominant frequencies. In addition, we conduct flow visualisations, and reveal the effects upon axisymmetry of wake. Finally, we classify the flow into three modes based on both periodicity and axisymmetry. Such a modal classification reveals that the enhancement of flow's irregularity corresponds to the decrease of C pb .Key Words: IntroductionWhile the flow past a bluff body at higher Reynolds numbers often becomes important in many practical aspects, it is one of rather later topics in the long history of fluid mechanics. Among such bluff-body-flow problems, there have been less researches concerning three-dimensional bluff bodies, in comparison with well-researched two-dimensional ones such as a circular cylinder which has advantages in some compatibilities with analytical, experimental and numerical approaches.As basic three-dimensional bluff bodies, it seems natural to consider axisymmetrical bodies with simple geometries like a sphere and a disc, whose knowledge is useful in the analyses of flying or suspended objects. But, even the flow past such a simple axisymmetrical body has not been revealed enough, despite of the wide ranges of its engineering applicabilities, in comparison with a circular cylinder.The present study concerns the flow past another simple axisymmetrical bluff body, a pipe or a tube, which is immersed parallel to the mainstream at high Reynolds numbers. The researches on the flow have been still less active than a sphere or a disc, although the knowledge is useful in many industrial fields, such as the designs for combustors, ventilator (2) − (8)

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Momentum theory of diffuser augmented wind turbine.

Cited by 15 publications

References 0 publications

Effect of shroud on the performance of horizontal axis hydrokinetic turbines

Effect of shroud on the performance of horizontal axis hydrokinetic turbines

Development of a High-Performance Wind Turbine Equipped with a Brimmed Diffuser Shroud

High-Reynolds-Number Flow past a Pipe

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