Open Journal of Fluid Dynamics, 2012, 2, doi: /ojfd Published Online December 2012 (

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1 Open Jounal o Fluid Dynamics, 01,, 15-1 doi:10.436/ojd Published Online Decembe 01 ( Expeimental Investigation o Peomance o the Wind Tubine ith the Flanged-Diuse Shoud in Sinusoidally Oscillating and Fluctuating Velocity Flos Kazuhiko Toshimitsu 1, Hionoi Kikugaa 1, Kohei Sato, Takuya Sato 1 1 Depatment o Mechanical Engineeing, Oita National College o Technology, Oita, Japan Depatment o Mechanical Engineeing, Kyushu Univesity, Fukuoka, Japan tosimitu@oita-ct.ac.jp Received Septembe 9, 01; evised Octobe 15, 01; accepted Octobe 6, 01 ABSTRACT The ind tubine ith a langed-diuse shoud so called ind-lens tubine is developed as one o high peomance ind tubines by Ohya et al. In this pape, the ind tubine peomance is investigated o both steady and unsteady inds. The compact-type ind lens tubine shos highe eiciency than the only oto ind tubine. Also, the lo stuctue aound the compact-type ind tubine is made clea by CFD and PIV in steady ind. Futhemoe, the peomances o the only oto and the compact-type ind-lens tubines o unsteady ind ae expeimentally and numeically investigated. Expeimental and numeical esults ae pesented to demonstate the dependence o equency o the hamonic oscillating velocity ind on poe coeicient. Consequently, the compact-type ind-lens tubine sho bette peomance than the only oto one in sinusoidally oscillating velocity ind. Futhemoe, the numeical estimation can pedict the poe coeicient in the oscillating los to an accuacy o 94% to 10%. In addition, the dependence o the tubine peomance on tubulent intensity and votex scale o natual luctuating ind is pesented. Keyods: Wind Tubine; Unsteady Flo; Wind Enegy; Poe Coeicients; Flanged Diuse; Natual Wind 1. Intoduction It is impotant issue that a ind poe geneation is impoved to aise the eiciency as one o natual enegy souces in ode to pomote the usage o sustainable enegy. Accoding to the backgound, the ind tubine ith a langed-diuse shoud-so called ind-lens tubine - is developed as one o high peomance ind tubines by Ohya et al. [1]. In paticula, the ind-lens tubine can geneate electic poe even in lo velocity ind since the langed-diuse shoud inceases the ind velocity at oto. Fo the long and compact type ind lens tubines, e studied the detail lo stuctue aound the ind tubine ith a paticle image velocimety in authos pevious ok []. Recently, eseach subjects o ind tubines in unsteady los become impotant, hich ae the eects o luctuating ind velocity and lo diection, non-uniom inlo, tubulence and othe actos. They inluence the peomance and atigue poblem. In paticula, ind in Japan is moe unstable than esten county, namely ind velocity and lo diection ae easy to luctuate. Thus it is impotant that the chaacteistics o the tubines in unsteady ind should be made clea. In pevious concened oks, the numeical peomance estimation o the oscillating ind velocity is poposed by Kaasudani et al. [3-5]. In this pape, e ill ocus on the eect o the luctuating ind velocity upon the ind tubine peomance. The peomances o the odinay oto ind tubine and the compact-type ind-lens tubine in hamonic oscillating velocity ind ae expeimentally and numeically investigated. In paticula, expeimental and numeical esults ae pesented to demonstate the dependence o the ind velocity equency on poe coeicient o the ind tubines. Futhemoe, the eects o the tubulent intensity and votex scale in natual luctuating velocity ind on the tubines peomance ae studied.. Expeimental Appaatus.1. Wind Tubine Model The schematic designs and photogaphs o the compacttype ind-lens tubine ae shon in Figue 1. The optimum diuse poile and the lange height ae detemined by Ohya et al. [1]. The otos ae designed o the to tip-speed atios, D = 3.7 and 5.0. Hee the basic blade poile o D = 5.0 is designed by Fuukaa et al. [6]. The blade coss section poile is changed om Copyight 01 SciRes.

2 16 K. TOSHIMITSU ET AL. NACA6318 at oot to NACA631 at tip along a span. The speciic dimensions o the diuses and the oto ae listed in Tables 1 and espectively... Measuement System o the Wind Tubine Peomance The toque and otational speed o the oto ae measued by the expeimental appaatus as shon in Figue. The ind tubines ae set up at the cente o coss section o the ind tunnel. The ind tubine poe measuement system is consisted o the toque detecto, the otational speed senso, the toque convete, the DC moto and the DC poe supply. The DC moto and the DC poe supply ok as a poe geneato, hich contol the oto load and the otational speed. Hee the geneated ai lo is actively contolled by the 66 ans o the multi-an ind tunnel in ONCT. 3. Wind Tubines Peomance in Steady Flo 3.1. Poe Coeicients o the Wind Tubines in Steady Flo The poe coeicients o ind tubine ae deined by P C, (1) AU 3 hee P,, A and A denote geneated poe o a ind tubine, luid density, ind eceiving aea and the upsteam ind velocity, espectively. The poe coeicients o the only oto and the compact-type ind tu- bines ae nomalized by the oto sept aea AπD 4 m.9610 and the lange cicula aea AπD m, espectively. It is ound that the maximum poe coeicients C o the compact-type ind tubines ae 1.5 times as lage as the only oto in Figue 3. It means that the ind-lens tubine clealy shos highe eiciency than the conventional ind tubine. 3.. Flo Stuctues aound the Wind-Lens Tubines in Steady Flo The impotance o the lo stuctues behind the indlens tubines as pointed out to incease the velocity at oto in the pevious papes [1,]. In ode to investigate the mechanism o the inceasing lo velocity at the oto, φ06 7 L=45 D h =40 h t =3 D=00 φ6 D F =φ66 h=0 Figue 1. Schematics and photogaph o the compact-type ind tubine ith the langed-diuse shoud. Table 1. Dimensions o the ind tubine ith the langeddiuse shoud. Tip cleaance, ht 3 mm ( h t D = 1.5%) Diuse length, L D 0.5 Flange height, hd 0.1 Table. Dimensions o the oto blades. Roto diamete D (= ) 194 mm Hub to tip atio D D h 0. Design tip-speed atio U D 3.7, 5.0 Blade poiles NACA6318 (oot) ~ NACA631 (tip) Pitot Tube Roto Flanged-Diuse Toque Detecto (ONOSOKKI SS-005) DC Moto (Maxon RE5) Steady Flo and Unsteady Flo z x Wind Tunnel Toque Convete (ONOSOKKI TS-300A) Vaiable Resisto PC DC Poe Supply Figue. Schematics o measuing system o ind tubine peomance. Copyight 01 SciRes.

3 K. TOSHIMITSU ET AL. 17 heeith e pesent an expeimental and numeical timeaveage steamlines aound the compact-type ind tubine at the tip-speed atio = 3.9 and mean velocity U = 7 m/s. The expeimental steamline by PIV measuement is shon in Figue 4. Also the CFD analysis ith the commecial sotae ANSYS CFX 1 is pesented in Figue 5. The numeical analysis is based on the nd ode upind implicit scheme o the consevation equation and k tubulence model. Figue 6 shos the multi-block 3-D mesh o the numeical analysis, hich is consisted o 6.4 million nodes. The oto mesh block otates at 700 pm. The bounday conditions ae identiied as the inlo conditions o U = 7 m/s, the exit pessue o kpa, slip los on the outside alls and nonslip los on the igid object suaces. The votex stuctue behind the lange o both PIV and CFD esults qualitatively agee ith. Tin votices ae ound behind the lange. Accoding to the esults, the lo stuctue is illustated in Figue 7. The votex A behind the lange mainly caused the lo pessue egion. Thus it inceases the ind velocity at oto. The maximum velocity at oto suace is calculated 9.5 m/s as velocity ising. 4. Peomance in Sinusoidally Oscillating Velocity Flo In this chapte, e expeimentally and numeically discuss the peomance o the ind tubine in sinusoidally oscillating velocity ind. Figue 4. Time aveage meidional steamlines by PIV. Figue 5. Time aveage meidional steamlines by the pesent CFD. 10D 4.1. Expeimental Conditions o Sinusoidally Oscillating Flo to Investigate the Wind Tubine Peomance The upsteam ind velocity o the ind tubine is undegoing identical hamonic oscillation as ollo, U t U u sin πt. () D.5D 7.5D 10D Figue 6. Multi-blocks unstuctued mesh o calculation. Geneated votex B by the lange Flo Votex A causes the lo-pessue egion Hub Figue 3. Relationship o poe coeicients and tip-speed atio in the steady ind velocity 5 m/s. Inlet egion Thoat Diuse Roto Flange Figue 7. Schematic lo stuctues aound the ind-lens tubine in steady ind. Copyight 01 SciRes.

4 18 K. TOSHIMITSU ET AL. The peomances o the ind tubines ae investigated as the upsteam mean velocities U = 5 m/s ith oscillating amplitudes u = 1.0 m/s. The ind velocity oscillates at equencies = 0.033, 0.05, and 0.5 Hz. Detail data ae listed in Table 3. The time histoies o the oscillating ind velocities at U = 5 m/s and u = 1.0 m/s ith = 0.5 and Hz ae shon in Figue 8, hich ae measued at 1.4 m upsteam location om the ind tubine ont by a L-type Pitot tube. It is ound that the expeimental ind coectly oscillates ith the speciic conditions. The chaacteistic equency o the oscillating ind based on the tubine oto dynamic esponse and the poe coeicient in steady ind is poposed by Kaasudani et al. [4] as ollo, 4 C I 3π U, (3) hee,, I, and C mean luid density, oto adius, moment o oto inetia, the tip-speed atio at the maximum poe coeicient and the estimated poe coeicient integated the poe coeicients in the steady lo, espectively. (The details o the numeical teatment ae descibed in the late section 4.3.) The moment o inetia o the oto is I = kgm. Equation (3) has the basic assumptions hich the Table 3. Conditions o oscillating inds and tubine chaactes. U [m/s] u [m/s] uu% Oscillation Fequency, [Hz] (Oscillation Peiod, T = 1/ [s]) (0%) 0.5 (4) (1) 0.05 (0) (30) Wind tubines 1 D Only Roto (0.) 0.64 (0.1) Compact (0.34) 0.87 (0.9) Figue 8. Compaison o expeimental and theoetical oscillating ind velocities in the ind tunnel. oto esponse is the quasi-steady state and tubine oto toque is depended only on tip-speed atio [3,4]. In othe ods, the lo tansient time hich the lo ield aound the oto coesponds ith the oscillation ind is suiciently small, thus the quasi-steady state is satisied. It means that the tubine oto can esponsively otates to the luctuating ind velocity o. Hee, e should mention that Kaasudani et al. insist that the eal only oto tubine does espond o 3 by numeical simulation [4]. We ae going to examine hethe the quasi-steady esponse can be applied to this equipment. Let the oto speed be 3000 pm, i.e. the time o one otation be t =0.0 seconds. I the inlo velocity deceases to 1 m/s, the lo pass at the oto tip o the thickness mm o tbp = 10 3 seconds. Since the time t bp is suiciently smalle than t, thus the lo ield aound the oto can enough changed duing one otation. Futhemoe the oto blade passing time t p o the ind should be suiciently smalle than the ind oscillating peiod. Since the axial length o the oto equals about 4cm, the oto blade passing time t p equals 0.04 seconds. Hence t p is much smalle than the ind oscillating peiod (4 seconds at = 0.5 Hz). Consequently, the los aound the oto can be egaded as the quasi-steady state o this expeiment. The expeimental values λ and ae shon in Table Poe Coeicients o the Wind Tubines in Oscillating Velocity Flo In this section, e pesent the example esults o the mean lo U = 5 m/s and u = 1.0 m/s (i.e. uu = 0%) in the conditions o Table 3. The eects o the ind equencies upon the poe coeicients C as the unction o the mean tip-speed atio λ o the only oto and compact-type ind tubines ith the designed oto tip speed atio λ D = 5.0 ae shon in Figues 9 and 10. The maximum coeicients ae pesented at.7 and 3.5 o the only oto and the compact-type ind tubines espectively. The poe coeicient inceases ith deceasing the equency. Let discuss the dependence o the ind equency on the ind tubine types. The poe coeicients in the steady ind ae smalle than ones o the oscillating inds o = 0.033, 0.05 and Hz o the only oto. While, the case o = 0.5 Hz is smalle than one o steady ind o λ = 1.6 to.8. It is indicated that the oto do not espond the oscillating ind at = 0.5 Hz o the tip ange o speed atio. On the othe hand, the poe coeicients o the compact-type ind-lens tubine o all equencies ae lage than one o steady lo. It is made clea that the compact ind-lens tubine ok ell o Copyight 01 SciRes.

5 K. TOSHIMITSU ET AL. 19 Figue 9. Eect o the ind equencies on the time aveaged poe coeicients C o the only oto ith U = 5 m/s, u = 1.0 m/s ( u U = 0%) and = 5.0. Figue 10. Eect o the ind equencies on the time aveaged poe coeicients C o the compact-type ith U = 5 m/s, u = 1.0 m/s ( u U = 0%) and = 5.0. the highe oscillating ind equency. Theeoe, the compact-type ind-lens tubine is suitable o the oscillating velocity ind than the only oto one. In ode to make clea the dependence o the tubine type on peomance in the oscillating lo, e deine the inceasing atio o the maximum poe coeicient on the basis o steady ind as ollo, C C λ D λ D, (4) C hee C and C ae maximum poe coeicients in unsteady and steady inds espectively. Figue 11 pesents the inceasing atio o the only oto and the compact-type ith λ D = 5.0. As you see, the compacttype tubine is bette than the only oto Numeical Estimation o the Poe Coeicient o the Wind Tubines in Oscillating Flo Kaasudani et al. suggest that the numeical estimation o Figue 11. Inceasing atio o maximum poe coeicient o oscillating ind on the basis o one o steady ind. tubine peomances o the oscillating ind [4]. Hee it is assumed that the oscillating ind velocity Ut consists o the linea ut he unsteady component ut does not coelate to the unsteady poe coeicient o a ind tubine. The time aveaged poe coeicient C o the oto is detemined though the steady poe coe- A icient as the olloing Equations (5) to (1), C C A C C A 1 3, (5) 1 g d C, (6) g h, (7), (8), (9) 1 T u t 1u t dt T, (10) 0 U U exp 7.49 g exp h, (11). (1) Hee it is mention that the appoximated tems o g and h ae independent o moment o inetia, oto adius, poe coeicient and contol time. The poe coeicient in unsteady ind is 3 lage than one in the steady ind. The poe coeicient atio is deined to compae the expeiment esult C E and numeical estimation, C T CE CE A C C 1 3. (13) T Copyight 01 SciRes.

6 0 K. TOSHIMITSU ET AL. Figue 1 summaizes o all cases. The only oto and compact-type tubines ae illustated om let to light o each equency, the same patten o ba gaph pesents also the ind tubine type. As you see, the numeical estimation can pedict the poe coeicients in the oscillating los to an accuacy o 94% to 10%. 5. Peomance in Natual Fluctuating Velocity The natual luctuating ind is geneated by the active contolled multi-an ind tunnel on the basis o Kaman s poe spectal equation as ollos: 1 Su 4It LU v, (14) Lv U I t. (15) U Hee, I t and L v mean tubulent intensity and votex scale espectively. We examine the eect o the main actos o the natual ind on poe coeicients o the only oto and the compact-type ind tubines o mean ind velocity 5 m/s. Expeimental condition and the eect o tubulent intensity on poe coeicient ae shon in Table 4 and Figue 13 espectively. Accoding to expeimental esults, both I t and L v incease ith inceasing C o both only oto and compact-type ind tubines. 6. Conclusions This pape pesented ind peomances o the only oto tubine and langed diuse shoud hich ae so called the compact-type ind-lens tubine in steady and unsteady inds. The lo stuctue aound the ind lens tubine is made clea by CFD and PIV in steady ind. Also, it is shon that the compact ind-lens tubine oks lage Figue 1. Compaisons o the expeimental and numeical maximum poe coeicients o the ind tubines. Figue 13. Eect o the tubulent intensity on poe coeicient o the natual luctuating ind o time aveage ind velocity 5 m/s and votex scale 3 m. Table 4. Natual luctuating ind conditions at U = 5 m/s. Case 1 Case I t L v 5% 10% 15% 3 m L v 1 m 3 m 6 m 10% poe geneato than the only oto ind tubine. The peomance o the ind tubines is investigated in the hamonic oscillating velocity ind o the upsteam mean velocities U = 5 m/s ith oscillating amplitude u = 1.0 m/s at equencies = 0.033, 0.05, and 0.5 Hz. The expeimental and numeical esults ae pesented to make clea the dependence o the ind velocity equency on poe coeicient o the ind tubines in sinusoidally oscillating velocity ind. Consequently, the compact-type ind-lens tubine indicates the highe peomance than an only oto one in both steady and unsteady ind. In paticula using the pesent design oto, the ind-lens tubine is suitable o the oscillating velocity ind. The chaacteistic equency poposed by Kaasudani can be one o index to estimate tubine peomance in the oscillating ind. In the expeiment, the numeical estimation can pedict the poe coeicients ithin 94% to 10% accuacy in the hamonic oscillating ind. Futhemoe, peomance dependence on tubulent intensity and votex scale o natual luctuating velocity ind is investigated. Both actos ae incease ith inceasing poe coeicient o the only oto and compact-type ind lens tubines. 7. Acknoledgements The ok as suppoted in pat by the Gant-in-Aid o Scientiic Reseach though gant numbe om the Ministy o Education, Science, and Cultue o I t Copyight 01 SciRes.

7 K. TOSHIMITSU ET AL. 1 Japan, and the Collaboative Reseach Pogam o Reseach Institute o Applied Mechanics, Kyushu Univesity. The authos gateully acknoledge the suppot o Po. Yuji Ohya, Po Takashi Kaasudani and Po. Masato Fuukaa o Kyushu Univesity, to this investigation. REFERENCES [1] Y. Ohya and T. Kaasudani, A Shouded Wind Tubine Geneating High Output Poe ith Wind-Lens Technology, Jounal o Enegies, Vol. 3, No. 4, 010, pp [] K. Toshimitsu, K. Nishikaa, W. Hauki, S. Oono, M. Takao and Y. Ohya, PIV Measuement o Flos aound the Wind Tubines ith a Flanged-Diuse Shoud, Jounal o Themal Science, Vol. 17, No. 4, 008, pp [3] T. Kaasudani, Y. Ohya and K. Watanabe, On the Response o Small Wind Tubine to Changes o Wind Speed and Load, Jounal o Japan Wind Enegy Association, Vol. 31, No., 007, pp (in Japanese) [4] T. Kaasudani, Y. Ohya and K. Watanabe, On the Poe o a Wind Tubine ith Fixed-Pitch Angle Wings o Sinusoidally Changing Wind Speed, Jounal o Japan Wind Enegy Association, Vol. 3, No. 1, 008, pp (in Japanese) [5] M. Okino, S. Iba, T. Kaasudani, Y. Ohya and K. Watanabe, Eect o Atmospheic Tubulence on Wind Tubine Peomance, Poceedings o the 9th Symposium o Wind Enegy Utilization, Tokyo, 007, pp (in Japanese) [6] Y. Sugita, M. Ueda and M. Fuukaa, Flo Stuctue aound a Wind Tubine Shouded by Compact-Type Bimmed Diuse, Poceedings o JSME Fluid Engineeing Coneence 005 (CD-ROM ISSN ), Kanazaa, 005, Pape No (in Japanese) Copyight 01 SciRes.