univ of brit report for savonius rotor system

8/12/2019 Univ of Brit Report for savonius rotor system

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J o u r n a l o f W i n d E n g i n e e r i n g a n d I n d u s t r i a l A e r o d y n a m i c s , 16 (198 4) 85--96 85Elsevier Science Publishers B.V., Ams terdam -- Printed in The Netherlands

O P T I M U M - C O N F I G U R A T I O N S T U D I E S A N D P R O T O T Y P E D E S I G N O FA W I N D - E N E R G Y - O P E R A T E D I R R I G A T I O N S Y S T E MV.J. MODI, N.J. ROTH and M.S.U.K. FERNANDOD e p a r t m e n t o f M e c h a n i c a l E n g i n ee r in g , U n i v e r s i ty o f B r i t is h C o l u m b i a , V a n c o u v e r ,B r i t i sh C o l u m b i a V 6 T 1 W 5 C a n a da )(Received May 16, 1983)

S u m m a r yThis paper describes the design approach to a four-stage Savonius-rotor-based irriga-tion system suitable for a small farm of ~ 5 acres. The rot or const ructi on is based on anoptimum configuration of the blade geometry and aspect ratio, as given by an extensivewind-tunnel test program. The essential features of the full-scale system, including themicroprocessor-based braking and load-matching procedures, are described. The proto-type, designed specifically for field tests, is provided with appropriate performance andmeteorological information-monitoring instrumentation to permit their correlation.Based on the wind- tunne l data, the wind turbine is expec ted to deliver 10 000 1 of waterper d ay to a head of 4 m in a 20 km h -1 wind.

N o t a t i o n

aAbDdhp , q , 0PrSVP69

b l a d e g a p s i z ea s p e c t r a t i o h 2 / S = h / d )b l a d e o v e r l a pp o w e r c o e f f i c ie n t P / 1 / 2 ) p V 3 S )s h a f t d i a m e t e rb l a d e d i a m e t e r 2 r )b l a d e h e i g h tp a r a m e t e r s d e f in i n g b l a d e g e o m e t r y F i g .5 )p o w e r o u t p u tb l a d e r a d i u sp r o j e c t e d b l a d e a r e a d h )w i n d s p e e da i r d e n s i t yr o t o r a n g u la r v e l o c i t y

n t r o d u c t i o n

A l t h o u g h t h e u t i li z a t io n o f w i n d e n e r g y h a s r e c e i v e d s o m e a t t e n t i o n inr e c e n t y e a r s , a c a r e f u l r e v i e w o f t h e l i t e r a t u r e b r in g s t o l i g ht a n i n t e r e s t in g0167 -610 5/84 / 03. 00 1984 Elsevier Science Publishers B.V.


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R e s e r v o i r ~ _ _ _

w o S t a g e S a v o n i u s R o t o r |

86

Fig.1. Schematic diagram of a wind energy operated irrigation system.a s p e c t . I n g e n e ra l , m o s t i n v e s t i g a t i o n s i n t h e a r e a m a y b e c la s s i fi e d i n t o t w ob r o a d c a t e g o r i e s [ 1 5 ] :

a ) l a b o r a t o r y sc a l e - m o d e l in v e s ti g a ti o n s, n o r m a l l y c o n d u c t e d a t a c a d e m i ci n s t i tu t i o n s b y t e c h n i c a l l y q u a l i f i e d p e r s o n n e l , w h i c h s e l d o m e v o l ve t o ap r o t o t y p e s t a g e f o r f ie l d t e s t s a n d p r o d u c t i o n ; a n d

b ) o p e r a t i o n a l d e v i c e s, p u t t o g e t h e r b y e n v i r o n m e n t e n t h u s i a s t s w i thl im i t e d t e c h n i c a l b a c k g r o u n d , w h i c h f u n c t i o n a s a n o v e l t y a t a n u n c e r t a i ne f f i c i e n c y ; b e in g i s o l a te d d e v ic e s , t h e s e a ls o fa i l t o r e a c h t h e p r o d u c t i o ns t ag e .

T h i s p a p e r d e s c r i b e s th e e v o l u t i o n o f a w i n d - e n e r g y - o p e r a t e d i rr ig a t i o ns y s t e m F i g . l ) , f r o m m o d e l te s t s in w i n d t u n n e l s f o r o p t i m i z a t i o n o f t h es y s t e m p a r a m e t e r s , t o a p r o t o t y p e p r e p a r e d f o r f ie l d t e s ts . T h e u l t i m a t e o b -j e c t iv e w a s to e m p h a s i z e s i m p l i c i ty o f d e s i g n a n d e a s e o f m a i n t e n a n c e u s in gi n f r a s t r u c t u r e r e a d i l y a v a i l a b le in ru r a l a r e a s o f d e v e l o p i n g c o u n t r i e s . I np a r t ic u l a r , t h e s y s t e m a t t e m p t s t o m e e t t h e i rr ig a t io n r e q u i r e m e n t s o f s m a llf a r m s ~ 4 - - 6 a c r e s i n s iz e ) i n I n d o n e s i a , a c o u n t r y o f a r o u n d 1 0 0 0 0 i s la n d sw i t h r e g u la r w i n d p a t t e r n s a n d w h i c h h a s s h o w n i n t e r e s t in t h e c o n c e p t .

T h e p r o j e c t a p p r o a c h e s t h e p r o b l e m in se v e ra l s ta g e s :i) a s c a l e - m o d e l s t u d y o f a S a v o n i u s r o t o r 0 . 1 2 m 2 p r o j e c t e d a r e a ) in aw i n d t u n n e l , w i t h s y s t e m a t i c v a r ia t i o n o f t h e b l a d e p r o f i le a n d g a p si z e a n d

o f o v e r l a p a n d a s p e c t r a t io , t o a rr iv e a t a n o p t i m u m c o n f i g u r a t i o n ;i i ) w i n d - t u n n e l t e s t s w i t h la r ge r tw o - s t a g e m o d e l s o f t h e S a v o n i u s r o t o r


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87using the op ti mu m configu ratio n arrived at in (i), togethe r with severaldesigns of commercia l pumps;

(iii) assessment of the blockage effect during the wind-tun nel tests;(iv) detailed design of a prototype and its construction using materialsreadily available in an advanced industrial society such as Canada;(v) instru menta tion of the prot otyp e for field tests to assess performanceand structural integrity (stages (iv) and (v) were added to the program dueto interest shown by farmers in Canada);

(vi) technol ogy-t ransf er phase, involving simplification of the design usingmaterials readily available in Indonesia;(vii) field tests in Indonesia to assess performance and establish main-tenan ce procedures (this will also provide an indicatio n as to the loss ofeffici ency due to the design simplification); and

(viii) pro duc tion of the two versions of the same design as indicated above,one for use in advanced-tech nology areas and the othe r in developing nations.This paper describes briefly the progress made so far in the first five stages.Model studies

The Savonius geome try was selected for the project because of its relativesimpl icity and low start ing wind speed. Several families of single- and two-stage models were used in the test program to assess the effects of bladeprofile and gap size and of overlap, aspect ratio and blockage. The modelswere tested under several smooth-flow conditions using two wind tunnels,of different cross-sectional areas, ideally suited for this class of studies.S i n g l e s t a g e r o t o r s

Preliminary experiments with four different blade configurations, includ-ing semicircular geometry , suggested the one similar to t ha t proposed byKhan [6] to be promising (Fig.2). Hence the blade gap size and overlap studywas confined to this geometry. A typical two-blade model had a projectedarea of 0.12 m 2. The blades, rolled into the desired shape, were con str uc tedfrom 16-gauge alumi num sheet and supported by two Plexiglas end-plates.No vibration problems were encountered even at rotational speeds as highas 1600 r.p.m.

The models were tested in a low-speed, low-turbulence, return-type windtunnel with a test-section of 0.91 X 0.68 m. The air speed could be variedin the range 1--50 m s-' with a turbulence level less tha n 0.1 . The roto rspeed was measured by a Strobotac. For each blade setting, the torque out-put was measured using a variation of the conventiona l Prony-brake ar-rang emen t. The sensitivity of the sys tem was 0.5 X 10 -3 N m.

Typical results for the variation of power o utp ut with rotor r.p.m, forvarious blade separations are given in Fig.3. The results show clearly that asthe separation a is increased, the maxi mum power for a given overlap dimin-ishes. The maximum power with near-zero separation between the blades


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8 8

~ 1 1 2 5 7 m m - - - - - . .

~a D

1 2 7 m m

F i g 2 T y p i c a l b l a d e c o n f i g u r a t i o n t e s t e d d u r i n g b l a d e g a p s i z e a n d o v e r l a p s t u d y

60

f r j1 6 0 0 1 4 0 0 1 2 00 I0 0 0 8 0 0 6 0 0 4 0 0

R P MF i g .3 . T y p i c a l p l o t s s h o w i n g i n f lu e n c e o f b l a d e g a p s i z e o n p o w e r o u t p u t a t g iv e n o v e r la pa n d w i n d s p e e d p r o j e c t e d a r ea o f m o d e l , 0.12 m2 .w a s f o u n d t o b e 5 0 . 7 W a t 8 8 5 r . p . m . I n g e n e r a l , a n in c r e a s e i n g a p s iz et e n d s t o c a u s e t h e m a x i m u m o u t p u t t o o c c u r a t a h ig h e r s h a f t s p e e d f o r ag i v e n w i n d v e l o c i t y .

T h e c o r r e s p o n d i n g e f f e c t o f t h e b l a d e o v er la p b o n t h e r o t o r o u t p u t i nt h e a b s e n c e o f a g a p is p r e s en t e d i n F i g . 4 , w h i c h s h o w s a si g n i f ic a n t r e d u c -t i o n in th e m a x i m u m p o w e r c o e f f ic i e n t b e y o n d b d > 2 2 . T h i s s u g g e s t sc l e a r ly t h a t t h e r e l a t iv e m a g n i t u d e o f t h e s tr a ig h t -l in e p o r t i o n o f t h e b l a d ew i t h r e s p e c t t o i ts r a d iu s o f c u r v a tu r e i s a n i m p o r t a n t p a r a m e t e r i n t h ed e s i g n o f a n e f f i c i e n t b l a d e g e o m e t r y .


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8 916

15

14

o~3E

01~OtO

~ ~ ~ ~= O ]

V = 1 7 9 m / s

i i i |

b/d ,F ig 4 V a r i a t i o n o f m a x i m u m p o w e r c o e f f i c i e n t w i t h o v e rl a p a t z e ro g a p si ze

P _ . ~ b

- o

F i g 5 A p r o c e d u r e f o r g e n e r a t i n g f a m i l i e s o f b l a d e p r o f i l e s fo r e v a l u a t i n g t h e i n f l u e n c eo f g e o m e t r i c p a r a m e t e r s

Based on the above observation, a simple procedure for obtaining familiesof blade profiles was evolved, as illustrated in Fig.5. Note that by systematicvariation of the major variables p /q O a and b, togethe r with the blade as-pect ratio h / d their optimum combination can be established through anelaborate wind-tunnel test program. The amount of information generatedthrough variation of even some of these parameters is rather enormous.For conciseness only some of the typical results useful in establishing trendsare recorded here. In this study 0 was held f ixed at 135 .The variation of power coefficient with tip speed ratio for the three valuesof p / q studied showed tha t a decrease in the flat portion of the blade in rela-tion to its radius of curvature improves the roto r output Fig.6). Fur thertests are in progress with zero as well as negative values of p / q to establish anoptimum blade configuration.


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9 00 .44 - a = b = O / ~ ~/0 . 4 ( A = 0 . 7 5 /

B l o c k a g e = 1 6 . 4 % > . . ~ ,0 .3 (

,, ,Y~ ' ~ . ~ l~;i, ~ / / / .0 . 3 2 / / / / / ' ' ~

~0. 28 /~ / 'C p o

0 .24 , .0 . 2 0 ~ P / q = 0 . 4

o / ~0 .16 ~ , 1 .00 . 1 2 1 ~0 . 0 8

0 . 0 4, = 7 ' ~ k - 0 . 2

0 0 . 4 0 . 8 1 . 2 1 . 6 2 . 0T i p S p e e d at io

F i g .6 . E f f e c t o f p q o n v a r ia t io n o f p o w e r c o e f f i c i e n t w i t h t i p s p e e d r a t io .0 . 2 4

0 2

O . 1 ( ~ \C p

l

0 . 0 4o - ~ - - - 0 . 9 1

n , , , 0 . 5 1 . 0 1 . 5Q rT i p s p e e d r a t i o - ~ -

F ig 7 P l o t s s h o w i n g e f f e c t o f a s p e c t r a ti o o n p o w e r c o e f f i c i e n t o f a s in g l e- s ta g e S a v o n i u sr o t o r n o t e t h a t a n a s p e c t r a t io o f 0 . 7 7 l e a d s t o a m a x i m u m C p o f 0 . 2 4 b l o c k a g e r a ti o16.4 )).


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9

0 4 0 t ] a = b = 00 0 J

o 3 2 ~ T w o S age . o o V f ~ ~ \0 . 2 8 ' \

0 20

O . 1 , f l B l o c k a g e 1 6 . 4 % }0 . 0 ~ /0 . 0 ~

0 0 0 . 4 0 . 8 1 . 2 1 . 6T i p S p e e d R a t io

Fig.8. Effect of blockage ratio on output of Savonius rotor.Of considerable interest is the effect of the aspect ratio h/d on the wind-turbine performance, as shown in Fig.7. The results suggest an optimum

value of ~ 0.77, which was used in the pr oto ty pe design.Wind-tunnel results presented by different investigators often do not

correlate, because of differing test conditions. One of the major parametersaffec ting such test da ta is blockage. To have some apprecia tion as to t hewall confinement effects, three single-stage and one two-stage rotor modelswith identical values of a, b, A and p/q but differing blockage ratios weretested in a wind tunnel with a large cross-section of 1.53 X 2.44 m. Theresults presented in Fig.8 show clearly a dramatic increase in Cpm~ dueprimarily to an increase in local velocity with blockage. No te t ha t an increasein wall con fin emen t fro m 5 to 20 can r a i s e emaxby ~ 70 , thus leadingto a highly optimistic performanc e estimate if the blockage effect is notcorrected.Two -stage rotors

Besides providing useful informa tion concerning the opti mum bladeconfiguration, the single-stage model study emphasized, as expected, thepresence of dead spots when the blades are aligned with the wind and therot or fails to start on its own. 'Thus, from self-starting consider ations, it wasnecessary to have at least a two-stage rotor , with blades in the individualstages oriented ortho gonally to one a nother. Further more, the results sug-gested tha t to generate even 100 W at a wind speed o f 25 km h -1 wou ldrequire a project ed area of ~ 3. 5 m 2. The requ iremen t tha t ease of cons truc tion


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92

b e a g u i d i n g c r i t e r i o n , p a r t i c u l a r l y i n a r u r a l e n v i r o n m e n t , s u g g e s t e d am u l t i s ta g e c o n s t r u c t i o n . I t w a s t h e r e f o r e d e c i d e d t o c o n d u c t t e s ts w i t hm o d e l s o f a tw o - s t a g e r o t o r t o a s s e ss i n t e r f e r e n c e e f f e c t s d u e t o s t ag in g .T o t hi s e n d , t w o s c a l e d m o d e l s w i t h p r o j e c t e d a r e a s o f 0 .6 a n d 1 . 1 2 m 2w e r e d e s ig n e d , u s in g t h e o p t i m i z e d p a r a m e t e r s e s t a b l is h e d e a rl ie r , a n d t e s t e di n t h e l a rg e r w i n d tu n n e l . T h e s t ra i n - g a u g e - b a s e d l o a d - m e a s u r i n g d e v i c e m e n -t i o n e d e a r li e r p r o v e d t o b e i n a d e q u a t e a t l ar ge r o u t p u t s . I t w a s t h e r e f o r em o d i f i e d i n to a b i gg e r d y n a m o m e t e r u s i ng t w o c o n c e n t r ic c y l i n de r s , o n eo f th e m f re e to u n d e r g o r o t a t i o n a l d i s p l a c e m e n t u n d e r t h e a c t io n o f th et o r q u e t r a n s m i t t e d t h r o u g h h i g h -v i s c os i ty oi l i n t h e g ap . T h e t o r q u e - d e p e n d e n td i s p l a c e m e n t w a s m e a s u r e d t h r o u g h c a n t i l e v e r - m o u n t e d s tr a in g a u g e s a sb e f o r e . T h e d e t a il s o f t h e a r r a n g e m e n t h a v e b e e n d e s c r i b e d i n r e f. 7 .

T y p i c a l p o w e r p l o t s a t s e v er a l w i n d s p e e d s a r e s h o w n i n F i g . 9 f o r t h es m a l l e r t w o - s t a g e r o t o r w i t h a b l o c k a g e r a t io o f 1 6 .4 . I n g e n e r a l , t h ev a r ia t io n o f p o w e r c o e f f i c i e n t w i th t i p s p e e d r at io w o u l d b e e x p e c t e d t ob e in d e p e n d e n t o f w i n d s p e ed . H o w e v e r , in t h e p r e s e n t c a s e t h e p o w e rc o e f f i c i e n t s h o w e d a s li gh t in c r e a s e a t h ig h e r w i n d s p e e d s . T h i s m a y b ea t t r i b u t e d t o fr i c ti o n a l b ea r in g - lo s s es in t h e d y n a m o m e t e r w h i c h d e p e n d o nt h e r o t o r s p e e d a n d d i m i n i s h w i t h a n i n c r e a s e i n cv i n t h e r a n g e o f i n t e r e s th e r e .I t w a s t h o u g h t m o r e a p p r o p r i a t e t o e v a l u a t e t h e p o t e n t i a l o f t h e w i n dt u r b i n e i n t e r m s o f i ts p u m p i n g c a p a b i l i t y , p a r t ic u l a r l y g i v en t h e p r e s e n ti r ri g a t io n - o r i e n te d a p p l i c a t io n . H e n c e t e s t s w e r e c a r ri e d o u t in c o n j u n c t i o nw i t h t h e l a rg e r tw o - s t a g e m o d e l d r iv i ng a v a r i e t y o f p u m p s t o e s t a b l is h t h e irs u i t a b i l i t y f o r th e i n t e n d e d p u r p o s e . A t y p i c a l s e t o f r e su l ts i s p r e s e n t e d i n

0 . 2 5

0 . 2 0

C p 0 . 1 5

0 . 1 0

0 . 0 5a = b = OA = 0 . 7 5p / q = 1

m m ~m

~ - ~ ~ ' a , ~24 km/hr/~ % ~ ~ 2 0 k m / h r

.~16 km/hrd ow

o o o0 . 1 0 . 2 3 0 . 4 5 0 . 6 7 0 . 8 0 . 9 1 . 0

ip s p e e d r a t i o ,

Fig.9. Typical plots showin g ef fect of wind s p e e d o n o u t p u t f o r a two stage a v o n i u sr o t o r with a p r o j e c t e d a r e a o f 0. 6 m 2.


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93

Er--i i- r

Wind Speed km/ h: 22 4 256 28 8

P e r f o r m a n c e o f a ro t a r y p u m p Ii i i J iO 0 2 5 4 . 5 6 7 8 9 I 0 I I

FLOW RATE L/ ra inF i g .1 0 . V a r i a t io n o f f l o w ra t e w i t h h e a d a n d w i n d s p e e d f o r a m o d e l o f a t w o - s t a g eS a v o n i u s r o t o r ( S = 1 . 2 m 2, p /q = 1 a = b = O A = 0 . 6 6 , b l o c k a g e 2 7 .4 ) .Fig.10. The tests show th at even a small Savonius roto r of 1.12 m 2 project edarea with the optimiz ed parameters can deliver ~ 400 1 of water per hou rto a head o f 5 m at a wind speed of ~ 22 km h -1.Prototype design

With the optim um blade geometry aspect ratio rotor staging and pump-ing charac teristics in hand design of a full-scale wind-turbine sys tem wasinitiated. As stat ed before the initial objective was to design a system foruse in rural farming commun itie s in Indonesia. Accordingly the guidingcriteria which shaped the design were simplicity of constru ctio n opera tionand mainte nanc e utilizati on of locally available material and use of tech-nology compatible with the rural environment.

However as the design progressed interest expressed by farmers inNewf ound land Quebec and British Columbia suggested th at the re was asignificant local dem and for the device. It was ther efor e decided to design apro toty pe keeping in mind its ultimate application in a rural society butusing relatively sophisticated materials readily available in an advanced in-dustrial co un tr y such as Canada. Thus with a tech nology -tran sfer phaseessentially the same basic design may serve the needs of farmers in Canadaas well as in techn ological ly developing nations.ystem assembly

The prot oty pe described here which has been constructe d and installedwas designed specifically for field tests. Essentially the system consists offou r stages with each stage 1.2 m in diame ter and 0.915 m high thus giving aprojec ted area o f 4.45 m 2. The ro tor is built on a sleeve and suppo rted bytwo ball-bearings fixed to a mast 11.6 m tall. The mas t is held in pos ition


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94~ % , - - - - m a s t c a p

} - - ~ ' ~ - t o p b e a r i n g h o u s i n g3 . 6 6 m ; ' ~ -ro to r - ,= fi i , ~ ,

11 6 m ~ . "b r a ke d r u m / ' ~ , ~ / . ." g u y w r e " L ....~ I~ ,], ~ - ~ - ~ b o t to m b ea rin g h ou sin gx 'C - '- ~ /" b r a k e p l a te , - l ~ r ~ , t " . ~ , . .1 6 6 0 m ~ ' < to p t a n k ~ , / ~ 1 1 ' ~ =~ ~ d rive s h a f t " an {] pu lleys w ri . . . . . . / I I 1 1 ' \ _ ~ o ~ ei . . . . z / 11 44 ~- \--y m as t . .. .. .. ~ f

- w a t e r n e s < L j I I : . I jJ~ / , ' I I I I ', , pum ps and "-. ,_ " I I N " , , / b o t t o m t a n k ' - -

i ~ m a s t b a s e p la t e ~ / ' ~ ' ~ L r r o o f a n c h ~x , \ . \X , , , . / ,77 -~ ~ ~ q ~ : ~ . . . . . T ~ / ~ ; . T ~ C ~ X - I . I L ~ x \ ; . \ ~ 4 / i .3 1 1 . 6 m ~ - 1 1 . 6 m -

Fig.11. A four-stage Savonius-rotor-based w ind-energy-operated irrigation sys tem pro ject-ed a r e a 4 . 4 5 m 2 during field tests, indicating major subassemblies including the e m e r g e n -c y b r a k e , d r iv e s h a f t, p u m p i n g u n i t a n d a n c h o r i n g a r r a n g e m e n t , M e t e o r o l o g i c a l t o w e r a n dassociated instrumentat ion are shown elsewhere.b y e i g h t gu y - w i re s . A s e t o f p u l l e y s a t t h e b o t t o m o f t h e r o t o r t r a n s m i tp o w e r t h r o u g h a dr iv e s h a ft t o a s y s t e m o f p u m p s , l o c a t e d a t th e m a s t b a s et o fa c i li ta t e in s t a ll a t i o n a n d s e r v ic i ng F i g . l l ) . T w o w a t e r li ne s r u n b e t w e e nt h e s u p p l y a n d r e ce iv in g w a t e r ta n k s , t h e f o r m e r l o c a t e d a t t h e b o t t o m a n dt h e l a tt e r s u p p o r t e d o n t h e m a s t a t t h e h e i g h t d e s ir e d t o p r o v i d e t h e r e q u i r e dh e a d .

I n t h e a c t u a l a p p l i c a t i o n i) t h e m a s t a n d t h e g u y - w i r e s w il l b e re p l a c e db y a l o c a ll y c o n s t r u c t e d s u p p o r t f r a m e , i i ) t h e p u m p w il l b e c o n n e c t e dd i r e c t l y t o t h e r o t o r s le e v e , a n d iii ) t h e b o t t o m t a n k w i ll b e a n ir r ig a t i o nd i t c h , w e l l o r ri ve r, a n d t h e t o p t a n k a s e p a r a t e l y c o n s t r u c t e d r e s e r v o ir a ss h o w n i n F i g . 1 .Braking and load matching systems

T h e S a v o n i us r o t o r s y s t e m i s p r o v i d e d w i t h a n e m e r g e n c y b r a k in g s y s t e mt o g u a r d a g a i n s t p o s s i b l e s t r u c t u r a l f a i l u r e a t h i g h w i n d s p e e d s > 7 0 k m h - l ).E s s e n t ia l ly i t r e s e m b l e s t h e c o n v e n t i o n a l a u t o m o b i l e b r a k e , c o n s i s t i n g o f ad r u m w i t h s p r i n g - a c t i v a te d c a l l ip e r s c a r r y i n g a s b e s t o s p a d s . T h e b r a k i n go p e r a t i o n is g o v e r n e d p n e u m a t i c a l ly .

A c o m m e n t c o n c e rn i n g t he p u m p s a n d t h e l o a d m a t c h i n g p r o c e d u r e isa p p r o p r i a t e . F o r a p o s i t i v e < l i s p la c e m e n t p u m p , t h e f l o w ra t e v ar ie s l in e a r lyw i t h r .p . m . ; h o w e v e r , t h e w i n d - t u r b i n e o u t p u t v a r ie s as V 3. T h u s f o r e f f i c i e n to p e r a t i o n a l o a d - m a t c h i n g p r o c e d u r e is n e c e s s a r y . I n t h e p r e s e n t c a s e th i s isa c c o m p l i s h e d b y t h r e e p u m p s r a t e d a t 9 , 2 2 a n d 4 4 1 m i n -1 a t 1 7 5 O r ,p ~ m .E a c h o f t h e p u m p s is p r o v i d e d w i t h a m a g n e t ic c l u t c h o p e r a t e d b y a 1 2 0V A C s u p p l y , w h i c h i s s w i t c h e d o n t h r o u g h a m i c r o p r o c e s s o r c ir C u it a t a p re -d e t e r m i n e d w i n d sp e e d .


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95on i t or ing ins t rum ent at ion and cont ro ll e rA l i t e r a t u r e r e v i e w s u g g e s ts t h a t , i n g e n e r a l , f i e l d - te s t r e su l t s w i t h p r o t o -t y p e w i n d t u r b i n e s a n d t h e i r c o r re l a ti o n w i t h m o d e l w i n d - t u n n e l d a t a a r e

i n d e e d q u i t e s c a r c e . T h i s i s p a r t i c u l a r l y t r u e f o r t h e S a v o n i u s c o n f i g u r a t i o n .T h e p r e s e n t s t u d y p r o m i s e s t o p r o v id e t h is v it al i n f o r m a t i o n . I t is i n t e n d e d t ou s e t h e f a c i li t y t o c o r r e l a t e r o t o r r . p .m . , i n s t a n t a n e o u s a n d i n t e g r a t e dd i s ch a r g e r a t e s, w i n d v e l o c i t y a n d d i r e c t io n , a n d t u r b u l e n c e i n t e n s it y .T h i s w i ll a s si st in a s se s si ng t h e e f f e c t i v e n e s s o f b l a d e g e o m e t r y , p u m p c o n -f i g u r a t i o n s , a n d s e v e r a l l o a d - m a t c h i n g t e c h n i q u e s .T h e s y s t e m is p r o v i d e d w i t h a d ig i ta l r . p .m , m e t e r , t w o p a d d l e - w h e e l - t y p e

f i o w m e t e r s w i t h i n s t a n t a n e o u s a n d i n t e g r a t e d d i sc h a r g e d a t a o u t p u t s , a n d aw e l l -p r o v e n G ill a n e m o m e t e r , all c o n n e c t e d t o a m u l t i c h a n n e l d a t a - lo g g e rw i t h v a r i a b le d a t a - s a m p l i n g c a p a b i l i t y . D a t a c o n c e r n i n g w i n d s p e e d , d ir e c -t i o n , f l o w r a t e , e t c ., s a m p l e d a t s e ve r al p r e p r o g r a m m e d r a te s , a r e r e c o r d e do n m a g n e t i c t a p e f o r s ta t i st i c a l a n d c o r r e l a t i o n a n a l y s is .

I t w a s c o n s i d e r e d e s se n ti a l t o i n c o r p o r a t e a m i c r o p r o c e s s o r - b a s e d c o n -t r o l l e r t o :i) a p p l y t h e b r a k e a u t o m a t i c a l l y a t a d e s i re d p r e s e t w i n d s p e e d , toa s su r e s a f e t y o f t h e s t r u c t u r e ; a n d

ii) p e r m i t l o a d - m a t c h i n g b y a c t u a t i n g t h e m a g n e t i c c l u t c h e s c o n n e c t i n go r d i s c o n n e c t i n g th e p u m p s a c c o r d i n g t o t h e w i n d s p e e d .F i g u r e 1 2 i n d i c a t e s t h e f l o w o f si gn a ls t o a n d f r o m t h e d a t a - l o g g e r a n d

s i g n a l p r o c e s s o r a c t i v a t i n g t h e b r a k e s o l e n o i d a n d m a g n e t i c c l u t c h e s t oa c h i e v e t h e a b o v e o b j e c t iv e s .

~ l e \ \ \ \ ~ i /~ \\\\\~ /I/~ , ~ ~ ~ / , , i , / / ~ , ~ -~S- ,',,', ,~, ' i~

1 - J = g = =Fig.12. Field-test configurati on of rotor showing relative positio n of meteorologicalmast and a s s o c ia t e d i n s t r u m e n t a t i o n Directions of c o n t r o l s i g n a l s are also i n d i c a t e d


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9

C o n c l u d i n g remarksB a s e d o n t h e r e s u lt s o b t a i n e d , t h e f o l l o w i n g g e n e r a l c o n c l u s i o n s c a n b ed r a w n .i) T h e s t u d y w i t h f a m i l i e s o f sin g le - a n d t w o - s t a g e m o d e l s s u g g e s te ds u b s ta n t ia l e f f e c t s o f a s p e c t r a t i o a n d b l o c ka g e . T h e o p t i m u m v a lu e o f A

w a s f o u n d t o b e 0 . 7 7 . A b s e n c e o f a g a p b e t w e e n t h e b l a d e s r e s u l t e d i n m a x i -m u m o u t p u t , w h i le t h e i n f lu e n c e o f o v e rl a p w a s p a r t i c u la r ly n o t i c e a b l eo n l y f o r b d> 0 . 22 , R e d u c t i o n i n p q o v e r t h e r a n g e o f 1 . 6 - - 0 . 4 t e s t e d r e-s u i t e d i n a n i m p r o v e d p e r f o r m a n c e . E x p e r i m e n t s a r e i n p r o g r e s s t o e s t a b l i s ht h e o p t i m u m v a l u e .

i i) T h e w i n d t u n n e l t e s t s su g g e s t e d a p r o j e c t e d a r e a o f ~ 4 m 2 t o m e e tt h e i r ri g a ti o n r e q u i r e m e n t s o f a 4 - - 6 - a c re f a r m .i i i) B a s e d o n th e w i n d - t u n n e l d a t a , t h e p r o t o t y p e w i t h a p r o j e c t e d a r e a

o f 4 . 4 5 m 2 is a n t ic i p a t e d t o d e l iv e r a t l e a s t 1 0 0 0 0 1 o f w a t e r p e r d a y t o ah e a d o f 4 m i n a 2 0 k m h -~ w i n d .iv ) T h e r e is c o n s i d e ra b l e d e m a n d f o r w i n d t u r b i n e s w i th a p o w e r o u t p u t

in th e ra n g e 5 - - 1 0 k W , p a r t i c u la r l y i n r u ra l c o m m u n i t i e s . U n f o r t u n a t e l y ,r o t o r s i n t h i s c a t e g o r y h a v e r e c e i v e d r e l a t iv e l y l it t le a t t e n t i o n . T h e S a v o n i u s -r o t o r - b a s e d i r ri g a ti o n s y s t e m o f m o d e r a t e c a p a b i l i t y d e s c r i b e d h e r e re p r e -s e n t s o n l y a s m a l l s t e p in t h e e v o l u t i o n o f s u c h a d e s i g n . T h e p l a n n e d f i e ldt e s t s w i t h t h e p r o t o t y p e w i l l p r o v i d e p e r f o r m a n c e i n f o r m a t i o n h e l p f u l ina c h i e v i n g t h i s g o a l .c k n o w l e d g m e n t s

T h e i n v e s t ig a t io n r e p o r t e d h e r e i n w a s s u p p o r t e d b y t h e N a t u r a l S c i e n c e sa n d E n g i n e e r in g R e s e a r c h C o u n c i l o f C a n a d a G r a n t N o . A - 2 1 8 1 ) . T h e a s-s i s ta n c e o f M r . F . K n o w l e s a n d M r . J . W i e b e , S e n i o r E n g i n e e r in g T e c h n i -c ia n s, M e c h a n i ca l E n g i n e e ri n g S h o p , in th e d e s i g n a n d c o n s t r u c t i o n o f t h ew i n d t u r b i n e is g r a t e f u l ly a c k n o w l e d g e d .

eferences1 F.R. Eldridge, in d Machines, National Science Foundation, U.S. Go ve rn me nt

Printing Office, Washington, DC , 1975.2 U . S . D e p a r t m e n t of E n e r g y / N A S A , W i n d T u r b i n e S tr uc tu ra l y n a m i c s , N A S A C o nf .

Publ. 2034, N A S A Lewis Research Center, Cleveland, Ohio, 1977.3 I.D. F an to m (Ed.), roc. 2nd Int. Syrup. on Wi nd Ener gy Systems, Vols. I. an d If,

Br. Hy dr od yn . Re s. Assoc., Cranfield, t. Britain, 978.4 P r o c . I A A / S E R I W i n d E n e r g y C o nf e r en c e, A m . In st . e r o na u t. A s tr o na u t. , N e w

York, 1980.5 Proc. 16th Intersociety nerg y Conversion Conference, Am . Soc. Mech . Eng., N e w

Y o r k , 1 9 8 1 .6 H. M. Kha n, M od el an d prototype perfor manc e characteristics f Savonius rotor

windmill, Wi nd Eng., 2 (19 78) 75--85.7 V.J . odi , N.J. Ro th an d M.S.U .K. Fernando, A Savonius rotor based irrigation

sys tem for small farms in Indonesia, Dept. Me ch . Eng., University f British olumbia,R e p . M E - 8 2 - 2 ( 1 98 2 ) .

univ of brit report for savonius rotor system

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