GB2530162A - Wind power generating apparatus and axial flow type blade - Google Patents

Abstract

A wind power generating apparatus including a rotor 1 configured by a hub 43 (fig 4), the hub including a pitch bearing 41 (fig 4) for controlling the angle of fixing each of the blades, each of the blades being connected to the hub via the bearing, the cross sectional area of the blade is gradually decreased from the vicinity of a connecting portion 10 with the pitch bearing toward the tip end portion 11 of the blade. The rotor may be of an axial flow type blade. A pitch bearing drive may feature as part of the pitch bearing assembly. The cross section of the connecting root portion 10 of the blade to the hub may be cylindrical.

Description

WIND DOWER GWNPJTiTNG kPPkRATUS AND 4XIAL PLOW TE RLADE The present invention relates to an axial flow type blade and a wind power generating apparatus in which the axial flow type blade is used.

BACKGROUND ART

In recent years there has been a focus in view of environmental preservation on wind power generation in which the energy of wind is extractedaspower. Awindpower generating apparatus converts the kinetic energyof wind into the rotational energy of a blade and converts the rotational energy into electric energy with one or more generators.

The tower generated by thew md power generating apparatus is calculated by multiplying the energy that wind has (the density of air x the cube of the speed of air / 2) by an efficiency of conversion from the energy of wind into the rotational energy of the blade (apower coefficient referred to as cherexnafter) an efficiency of conversion from the rotational energy into electrical energy, and the swept area of the blade (it x the square of Dblade / 4, where Dblade is the diameter of the blade tip) Accordingly, possible measures to increase the amount of extracted power with the blade are to increase C> and to £ itiaase Dblade.

The maximum C value ts 59.3% acctrtiw to etzs 1 arJextraeting power Üt;an e tic4qy ca i not expected. In genen., the actual efficiency it approximately 50% due to tnutt1S ih aS the fbt th;t áttd tht frMtiOna1 dng the blade and wake rortioes caused by ottaai of thebl&dt. Taking adeitiation frun the ideal state iso acns1deratScn as a 1GSS, the loss is approximately Mr at the energy that wind ha.sf. ten j±: sa earL be diareased by Qt tbe ai't qf iea U3 P fl Lhan 14. From this act, it S 4fliç It to increase the ë*traotèd ê±" bi inoreas ins Cp.

in ött±ãEttO ittd±eairt c, theaing Dbladev ttibtAtee dite:ttIy t& incteastn9 power. FDTfl this fact, the :opan of the bade of fle win4 power generaDi* appara us S used in caumerdal poergeneration is beirg inqrea4 every year, in a case o leagt:heSng 1ie btack,, it isprticu1a1y the ki4e to yea structure thAt iSiSt received from wind due to te flitreased area a the blade and a bthdi4flOñfett uue to lilt which otoirs tt the ratat ng bLade f and a large amount of material is required in order to secure Stteflgthf act the b)ade. As a resultr the wetj tue bThdE may; be: £ncreaaed,, aM the cast f mania tjaflng the ba may incrse4, the çve 1:ct a technclggy f& hö# t& DbladS withOut. Sntreasizt9 the fbtbe receic!ed from wind is reqzize4 i.n order c eMèient1y ingreas t, amoS i ctraced by Sjifwifl4 p,r gexaUrg apparatus:wfth the blade and, to peyaat an ncxease in the matacturing cost.

It is natural to put a rèquést Zó iit a biádë 4dth hih C. fint hefre Thneaaiag Dbiade However, for example, ttda td athie*re the maximum C niue as disclosed, in Tony aurttn, wind Energy Handboek, Second Edition, p. 71, kIter, 2Q11 Increases t]e ëhord length di an i'i: use4 in the crc set&on of the a4c. tcwi. 1eNa4e flec,: tQ as the roQt he4naftexl.

fl area of the bládè it"téáéE *h&i the h"td l"h i* tteäEtd, and the ittd tt the blade also inreasee F±'the"t1't, tue. w"lflt oi the b1a'e: a1S increases:, and hiw incteases the cost of the".ade. In additipn, it is necessary Sui14 a hig1t-Srengh supportLigps (eierre4tç as a tpp hereiEter) in 4er to saey ctne the heavyweight bládê w in a direction from thi UStxi": tôwãrd the downstream of wind (a thrust dinctio load referred ton a tthUEt lttd hete'4MftAt) i'rpartiatasflygreat This increases tht cost ci other atructurea in addition te the 1rade.

mere are s*;as those4isct2s'e4 in US Patent No., 7883324 and Uflo49JØflfl5 tbe t4t the present tec}uo1ogy. the s*ject matter disclosed in US StSt N:9 1891:3 ts a blade fér wind powet and this blade has a different cross section depending on the position in the blade. In addition, the subject matter disclosedinus2009/O263252Aisabladeforwindpowergeneration, ano this b ade has a nai] 1 nq cdg-of hich ti-ic shape t W fferent from that of a trailing edge in the related, art.

In the disclosure of US Patent No. 7883324 and

US2009/0263252i, an airfoil that is shaped as if the trailing edge of the blade is cut is used as one that is used in the cross section of the blade near the blade root. in order not to increase the area or the weight of the blade while designing Op as high as possible.

There is also used a method of securing the amount of generated power by increasing ljblade while Op is high, hut such a blade is basically intended to obtain a large amount of generated power in an area where the speed of wind is low. This method is w:i.delyus ed in a case of, for example) obtaining the same oragreater amount of generatedpowerwxth Class ±1 (extreme value of a 10--minute average wind speed with a return period of 50 years is 42.5 m/s) windmills than the amount of power generated by Class I (extreme value of a 10-minute average wind speed. with a return period of 50 years is 50 m/s) windmills in lEG 51400-I that is an international standard standardized on the basis of values which are observed in Europe where wind power generationS is largely used.

The above rcetcd s found in w:n&r ls that -evIoped 4.

th Eth:e t±t, the tene iirid speEd is athpantsnly:Lb; aid steady windhwu year-round. Cnnraeiy, a special state 4t wind suth as a typhon occurs frequentiy in Asia ±nciu4iri ap:an or i±s areas ciose ta the equator. Such aaa.s nquAxe a windmill design that a.s called Class S other than the IEC ds described prevSoasly. In Class B, a rtertatt wind Epeed that i the étte*té :taiue o & 1:0 t±tEL ai:ngt win seed with a tétth peiad Of 50 years:j:s apprOximately 70 rn/s.

flmsablade far tbonareaa is regvired to havetigher strength than a blade that tis±:ies the Class I flndard s#hidi is aa4 n the values observed in *jrope, and cs.ch ac kla4e iteavy an4: reires high manuacturiag cost.

In addition, when wind power eñEfltJAt; à±AthkiBéS ttt ith:o1edfad d8ta of tité sot:t of tttntea. power iS :cllected toa certain extent., there may be a wind pokier setating apparatus ot which the amount of genente4 power is: less, tth' tS expectat Son othe amount of gáiratet ppwn that is assume4 ±his:aibt a e pt tnct4a or a wind PWE apparatus that is desired to be bbflfld to produce a further ia±'è áihOtEt èf etC'E±áted poet. These 3fl totxsideted to be tespnded by: petThruing a xepair auth as ±eftMUtatiai aria r"powsriag that ate performed tot therm& pQwer eeratiortandtheiike. In this case, it is:pc:ssibietoizwrease the anun; of generated power without: requiring, a investment pro4Ød th t remaSning life of strwures sudh

I

M a béi IS Ufftté±tt, aad a biadE pthcin a]Sflt amount f genente&pown with a load tthSn the esteit et assessment at the remaIning ilie can be provUe4.

& preferred aim of th i reset nvertiati is to pro?idef a biàdê in *hidha ttàdi-btf bet*ei th diatttt at the: biad tfl fl]j and Cp is madL diffetei:tls ftarn;ozie that is designed to have themaximwn C va],ue and te atnc>tmt;ot extracted ppwr can increased w14ite:t:he thrus Ipad wliiqh pcs frpi Made toward sttctwree avch as a tower j Accord &ng to an aspect o the present iflttióñ thétE is provided a. wiEld ôEè± EñeSti àjáàbtS thite St Ludas ±ótO ohtj:red v: a htth aidtpilflhtty fb.ladt a. cOnhzetta wind nta: eIetSal energ with the ctor, in wtiich the hub a fltch bea1.ng drive dev±ce aSf a pitch ear4ng t4 tontrois the angte o:t Tixiüg S eath of thi biad*s dth respect S the 1nt eactt of the blades S czate4 tq the hub via the p4.1* the cross-sectional area Of the blade gray ally, decreased f±óffithé V±Thfly;et a a::ettit portion with th& pitch beating toward the t±t ers pQ3io at the blade to anc her aspeat at time peaent Irnceution, theta is provided an axial flew type biadé al a idad power generating apparatun that Inc lu4es a qp igit4 by a and a pturøZty of 1 4ø4!4 cr t into eaectria1 energy with the rotor, in which each of the axial flow type blades is connected to the hub via a pitch bearing, and the cross--sectional area of the axial flow type blade is gradually decreased. from the vicinity of a connecting portion with the pitch bearing toward the tip end portion of the blade.

According to the present invention, there can he provided a blade in which a trade-off is made between the diameter of the blade tip Dhlade and. the power coefficient Cp, and the amount of extracted power can be increased while a thrust load caused by the blade on structtres such as a tower is suppressed.

Other problems, configurations, and effects other than the cne, cescnhcci uhove wnl bec3ne apparent from escriptaon of an embodiment below.

in the drawings: F:g I i a diaqram illustrating a blade thar ±5 in accordance with an embodiment of the present invention, Fig. 2 is a diagram illustrating the cross section of the blade that; i.s i.n accordance with the embodiment of the present invention.

Fig. 3 is a diagram illustrating the blade that is in accordance with the embodiment of the present invention.

Fig. 4 is a diagram illustrating a huh and a blade root portion of a wind power generating apparatus that is in accordance with the emhodient of the present invention.

Fig. 5 is a diagram describing the actuator disk theory.

Fig. 6 is a graph illustrating a relationship between an induced velocity coefficient, a power coefficient, and a thrust coefficient.

Fig. 7 is a graph iflustrat.ing a relationship between the power coefficient and the thrust coefficient.

Fig. 8 is a diagram iJ.lustrati.ng a reference blade.

Fig. 9 is a diagram illustrating the cross section of the reference blade -Fig. 10 is a diagram illustrating the cross section of the blade thac is in accordance with the embodiment of the present invent.1 on.

Hereinafter, an embodiment of the present invention will be described by using the drawings.

First Embodiment Fig. 1 is a perspective view of a blade 1 in the present embodiment, In a windmill tha.t is a target of the present embodiment, a blade 40 is fastened to a pitch bearing 41 as illustrated in Fig. 4, and the pitch angle of the blade is controlled by rotating the pitch bearing 41 with a pitch bearing drive motor 42.

The pitchbearing 41 is fixed toahub 43 that is connected to a rotor shaft such. as a speed in.c reaser and a generator.

A N.adë toot ot:tibn. 44 (: bltde tadt p&tti*tk to in Fig. l is fomed into a athetauttafly yUndriëa1 siti. tt o$r 1ç be connected1 to the pitab bearing 41, an4 the cross-sectional area o:f the btade root p:ottion 44 i:s 4ecnase4 tçward a b]Sde fp pprflp a.

The cross section ot the blade root portion 10 and eac1 A Sétft±t:f the bi3dE I at blade cross section pcsitions 12 l3k thd 14 in i* I are illustrated as; a b1ade root, portion ann section 20 and ba4e cn aed4ens 2ã a1 Fig. 2.

The blade I LWSrate4 in F$g. 1 is stiapid in a in *ic ° t S 40th & the biad 3. tht art ppsttiqne further towsd the biàdet4 Ed (::efed to as a tip hersiüáftéf tI: the?±tatportion ani5nciu&ed in a suate thst in1udes the suhstaztUafly:cyi.indflcal cross see di bhWct portion.

The techn±cal background of tcse apaswill bedesttthëd as follon,. Th the %,flt thcn, the perfótM±të at a blade Is represented by using the fundaTnefital equation of a model &n which the flow of air Eitü±id a. wiid iii is sSm$iliet, an4 it energy is eictratted when the speed of air is decreased in 3e axiAl;difEttt of tht mis moaei is afundarnental theorySta winmU:14sflc,sed in 1919 by efl Betz in Germany (Aber, Bfl Introductiöft tQ the 42ery of F1OWtdac]ne a, órd, 196j And iS obtairet front the axial thórSntthü theoi: thát telteS tU tbAt±bhSahtd at and behind theplane at rotation of a btade of a wio8mnl.

mete ate asstunptiozis fr the model that tiie plane p rot ion o± the.. :E4e is aranged perpendicular S bti,e flow of a4x, the fliiid j in preqsThe, fal drag does not exist, the number of blades is infinite, the flow of air is steady the rotational flow Of air tai tea t:; ±otajon of the taae does tot oot, a stti tsite tarxataxt at infinity from the? blade?. fljss model COXre$p0nd4 to a model that finds hç ear a unid'xettionaZ flow that passes throxgh a q tai tan be decreased in speed. This modàt shows a tini va:e from ii tM of energy.

The ?cqceptw1 diagram of the átttàtt* disk thtfl (içt*ater disk thOdél) is iiitst±:ated ii Fñ4 s. me sq.iation ot the actuator disk tkeary is represented by tsing the Bi:gns iiiuat±t.ted in ?Ww 51 A 4Lfterena in momentar dt a differttiaLradius dr in a po:sidion o a atreaut tubeo a r4t'w r ahea ot and eMn4an aç;uaqr d$lc: is i by EqaAt ion T=L(p*rdrU)-U4(p2,zr&U)4 ke p is t) 4flty of air, U iE the speed ot i* the ada. ditecticri of the stream She, and the ssria I to 4 of U respecu.,Sy denote a ZPca ioP P tpstttant si4e of t1e ±lqw1 a t:pcatiqi immediately a1ead of the actuator dlSki a location immediately behind the actuator disk, and a location on the downstream side of the flow.5 moe the mass of air that passes through the differential stream tube is conserved by conservation of mass, Equation 1 becomes Equation 2, drn = (p2-drU)1 = (p2drU) (2) dT=dm(U1 -U4) From the assumptions that pressure is equal at infinity, and the speed of air passing through the actuator disk is represented by the avera e. value of th infinite upstream speed arid the infinite downstream speed of air since the speed of airpassng t"roLicjrathe actutnro sk s srnpllfledtcDe eqal, Equation 2 becomes Equation 3 with an axial induced speed coefficient a.

dT = 4izr p01 aO a)dr (1 (Ia)bT. (3) The power output is the product of the difference in axial momentum and the speed. Thus, a power output dP in the differential stream tube is represented by Equation 4.

dP=4irrpUa(1-afdr (4) T power coefficient Cp (a ratio of power that can be extracted) t'nat is obtained by making power of the inflowing áfrfló* di Sh&ftS s it Sêd aS4 index. tls represexits pe:t outptit eharacter±st4a of the windin%U. Eqpation$ npnSenta the powei coetftcSent c Th the 41ffereSial flrw tube *,, (5) A th±uSt óiffidjent c thatis bbtairttd by makix the: kthEti& e:; of dimensionless Is used tcr thtf axial force (4U terene in momentum). Eua±oa $ ttepresetts the thnxst coetticientCt j:j dif: it1,4Z stcii dC7=4a(1-a) (6) AS iS apparent from Equatiøn 5, the powr coeffii4efl is a ubii é4tSfl±flfM the axiaJ. ind.ice4 eã coeffIcient and: bett wëS a m imum of 1627 at a i/ O tflsIflte4 in Fig. 6. The thruit çp jqj at ia: tLrne is tt9. ThiS is the upper uS of ppz extraeted from th airf 104i,. and the upper limit is known as Detzs law Although Eqttions 5 and are cotxMdere with the diftêitit1 fldiUS the nites c EquatSons 5 and 6 become 9: thtfliffli when the condition of a. 1(3 Is StäbXishe4 acx:ss the WLade span 4teflioa. In adfltoion, :be a4Pa. o!qe fl the bade c is decrease4 by BS since EquatiOnS S áId 6 öôñ6itñi of thE iMhtedspeed otftScitts1s apparent from the f on ot the equatiens, azfl influences s3ASt, as fertoxmance of the airtotl us4 i tie eras section of S blade are excbide:d.

tSign of the blade with the NACA airfófli Of. *hiëh tte rfonncets disclosed isper:rsd mtiItipletirnes4na manner in which dthdi tidE of the M ütll nine and the mjrxLmum Cr táliE ail satif ted by using the blade element w method reZerre to as a BEM heeinaer (ry, iS1 sxteq, Han4book, second Ediip, p. Il, $fley, 20flJ thet is used Lna&e design, and te t,4ts 1:re arranged in Fi. 7.? k set tS cf white efreles is a St 6f déEifl st1a k sclid line plots Bàti eóMoh tth spt b Cp axid C5.

That i the Sdlid 2ié 72 iliflsttateE Betz'a: law, flttough it: is difficult to obtain a hSgh C# auth as the one tn z, iaw esrene in a aee of the same C when the i4e is designed by uaingactual aCr?oft perfn e ttLsw4etQo&that théit is a tendénçy h set, 4eatgn s4utioné to öhhè E: in Betz s law, in a manner in which the rate f change of Ct jncireang as j incitS.

Prom sutbh & tendettey., tht amount of change of Ct can g±èátét tháfl uteatiet of thange t c, tq selecting a d±gn s&lutiott With sniall Cp in blade desIgn, not wdSigz2 acluttcn with the rnazitrnm Cp value.

The design rpu1s $ uflrfle4 i 7 inustate 1.3 etSlE. in With the tiaae with tht ffiaximum Cp, taRts Is set as a reterence. the]agtlt Gf the blae La inazased by ió% an&294 f that at the neene, and Cy is designed in a manner in whib. hrnV 1:o:a4s aze equ..

F&rst, the shape of the rSfirehtë blade is i1iuSt±'ttt in Fig. 8. This b]sde trreeponds? t a design result 73 in Fi. 7 The th±t at oeffiiat i. 8, aftd the power cAefient IS G.49. The detign teaiit 73 is a poInt of detgn with the; inazimum C value in FIg. 7. 8 Fig. 9 itjstntes oeflp g the oos efljon of th-ade in anarbitra.y span4zcflona1 croe* àibtlOñ thEt isviewedtathetrectionof the bládé tip Fi4:+ flflust±attS a blade rot po±tibñ drósä ttit 9O Off a blade ro*t pørtio so in p5. 8,, a bidettiaum chot3 cro:ss s:et a 91 at the position. of the maximum thor ta iength ron tht ieaØtng edge to the traiflng edge t eheainqiZL th* is, a b3a! !*!L cherd erosa section posiUon fl, a Wa4e t pQrtion a±bES sect ipn * of a a4:tp 8Z. d a square that i*1udéE root portion 80 (blade root pottThn cross section jçlt4.flg sqpate 93).

mis blade is in which p is pxioxSiLzed in deØign thtflt rêiñdfafl aAd is t a ta;get;Gf the premt inveM4on betase there is a;crosa section of the}raae tht exten4s: t1e span dire pn ot the ba4e 4 i to be included in the square tt*t I 44 root portion &flillit±Attd P. 9 Next, Eig. 3, itbwtrates a design in whidh ti1⁄4, lengi'h Gf the blat is ±ncre4sed by approximately itV from that of the reference bta4e. This b.ade qorrespn,frtoa4sSgn result 14 in ?ig 1 The thrust coetficient is 0 61, arid the power cocint i. 47. ra design the? blade' with a low thrust: cteflciéiit the höE,d lel' tb of kh' aidan ot the blade erst j:j". g de Si"tttd t be ama]. The desIgn result 74 is a point of design or the exampae dèscribe,' in the' present eflodtnent flg. to filitwtnes qyr lapping of the d±ta stiote': $ k'S blade &n an aEbitrary ftftrdi±édt'iö"l töss statiot" that i ed front the di±ettiS' of tb" bitt tip. Fig' G' illustrateS 4 blade tt"5t po±'tibn "rOSe sett.ion 100' of a blade "toot poflion 30 in Eig. 3, "a blade niazimum dhqr,,' crass sesioxi: ioi at the'' position ot the maxithum d$or4' (a eng 4, e leadiztg edge to the trailing edge Qthe a4aztoi. ), that iE, a Wade cross s,,,,ct&pn pc,U; "3',,:, a blade tip pértid" ±i"It: se"4an i0 ci a bLade tip portion 32 and a a'"e that,includea bia4e root portion 30 (bl'é tbbt nfstn ez*ss sstUn iludin sqfl'e lea').

Th'Th; blade is fa tazet o the present invent"on because the" drass sectSen of the blade at an arbitrary pqsiflqn cn Se span at the blase is included in the square that includes the blade root port4i as illustrated Sn Vig. 10. POt tSLS bia"Ie the Wét of the b]4d is ifttened y 19%. ea though C is decreasedby an amount correapcn6ing to the increase in the swept area, Ce Is dereased y approximately Z%. the amount at generated fpower?is expectad t.Q ke tncze:ase4 y t%..

tat, ig 1 tMes a design in whih tPIEI 1èftth of the 4e i increased by ati1ttatly 2O froift that t th4 éfétt ë bládè Thiâ bládi db:espthds to e5jgn: result 75f in Pi4; 7: me thni:t cttfic±ent IS O.5, and the power coeUtcient is 0 42, To design the $1ae with a low thrufl 8 osUi.aient, the cthord length o2 the aizfqil of a4e ccn aecztion is es?igd t be small The 4esign restift tS is a poInt of design tot the example dés&1bèd iii thè p±settt enthoditnent Thtg baadE isisa a. t*±Et of the present seause the cross sect:Saof the bI:ade at an aflitrarypqsjtgn on te apt t the blade is Included in the cross sect9 of: the blade: root pGrtion as descrTh in Ftg. S or: tts bladë, he swept area a 1]4é $s, tne'easfl by 441. tVen thóttgh r is ca by an amount correspondil to the in.trease in tb.e swept area, c &i dè&eaEEd i: app awmteiy iat muss the amount of etìtrated power is expected to be increased by 2 o;t.

As suth, by achieving an increase in the ampxi of generate4 power with the ±engt of a. Cp, and usIng a bThde In ihith an inercase tn the load on the bládë * IS ptS Sd, thé±t dth be pottde5a Wind po*.isr geitent±rtg açparattta that produces Wa large etztput whUepzentirzga1oad on stxutures such as a tower ron being iriaeased From a ditttent perspectct've, the ej14te caa represented as a blade &n whSch the chord length of the airféll in eaöh cross sect&on f the blade is SEt i Otder to reduce a lbd the biädé iii iáthiet in *hid the tiVSS Sectiort ot tht biiade at an anattatt:; pnitin in the tip direction is Sncaude in the sqaz'e that Inclzdes t pitch bet4zgtasing pextlan itt the btade rpt *t4,n,, a case of a l4i;; and the lilce that rare manufactured ugh pre-bendtig in which a. blade is bent in ãdithöè at the time ot manufacturing the bAdt j: Of détófltioii and the like Ot the bl it is nsa pn±ble to perfoxm ident:ificationo:fwbether the cross s:ect ion of theb2a4e at an arbitrary positiøn on the span t the blade is i]iuded in, the sgt are St inc1kzee the blade ro:ot pgrt$ou,, the cross section of the bladà at i 4:4n' poaition on the span Of the baade is included in the cross sectii at the blade root portion after the ábSdl.tttè ö itiOfi of te araersetton Of the blade at an arbitrary pas±tioxk on: the span of the biade s Fustbennore1 it is possible to assume that the lexz, of the: edge of the sare that ixcludes:he blade çot pç4 is fScj eased by approxirnatei 10* with ccsdderation of etitS in the shape of the blade that occur in manufacturing due to resins and the like which have manufacturing errors greater than or equal to the accuracy of machining.

The present invention is not limited to the above embodiment and includes various modification examples. For example, the above embodiment is described in detail in order to facilitate understanciinq of the nresent invention, and not all of the described configurations are necessarily included in art embocament ot tn.e present inventioia. In aadtkon, Lt is possible to replace a part of configurations in an embodiment with configurations in another embodiment, and it is also possible to add configurations in another embodiment to configurations in an embodiment. In addition, a part of configurations of each embodiment Carl be removed or replaced with another configuration, or another configuration can be added thereto.

The shape of the blade that is in accordance with the present invention makes reduction of a load on structures and the maximum amount of energy obtained from wind compatible with each other. This shape of the blade extracts energy from a moving fluid and reduces a load that is received from a moving fluid in any apparatus-es besides a wind power generating apparatus. Thus, the application of the shape of the blade is not limited toawindpowergeneratingapparatus. For example, the shape of the blade canbe applied to an apparatus that extracts energy from a flow of liquid (water, sea water, and the like) -