a

4'

NASA Contractor Report 172427

ACOUSTIC TESTS OF THE MOD-O/5A WIND TURBINE ROTOR WITH TWO DIFFERENT AILERONS

Kev in P. Shepherd and Harvey H. Hubbard

THE BIONETICS CORPORATION Hampton, V i r g i n i a

and

THE COLLEGE OF WILLIAM AND MARY V i r g i n i a Assoc ia ted Research Campus Newport News, V i r g i n i a

C o n t r a c t NAS1-16978 Grant NAG1-166 August 1984

National Aeronautics and Space Administration

Langley Research Center Hampton, Virginia 23665

https://ntrs.nasa.gov/search.jsp?R=19840024050 2018-07-08T22:09:09+00:00Z

INTRODUCTION

D

Y

P a r t i a l span a i l e r o n s have been proposed f o r a l a r g e h o r i z o n t a l a x i s

wind t u r b i n e (MOD-5A) as an a l t e r n a t i v e t o f u l l or p a r t i a l span b lade p i t c h

t o c o n t r o l l i f t and drag a t above r a t e d output power. Two conf igura-

t i o n s o f a i l e r o n s be ing considered f o r a p p l i c a t i o n t o t h e proposed MOD-SA

wind t u r b i n e generator were ava i l ab le a t reduced sca le f o r t e s t i n g on the

MOD-0 machine a t t he NASA Plumbrook t e s t s i t e . This paper presents some

bas ic parametr ic acous t ic data f o r these two a i l e r o n con f igu ra t i ons and

shows appropr ia te comparisons.

This e f f o r t i s p a r t o f t he Department o f Energy wind energy program

which i s managed by the NASA Lewis Research Center. The r o t o r blades

which were tes ted on the MOD-0 machine c l o s e l y model those proposed f o r

t h e l a r g e r MOD-SA machine and were designed and fu rn ished by the General

E l e c t r i c Company.

APPARATUS AND METHODS

Descr ip t ion o f S i t e

The wind t u r b i n e s i t e a t which no ise measurements were made i s a t the

NASA Plumbrook f a c i l i t y l oca ted near Sandusky, Ohio (F igure 1). The t e r r a i n

i n the measurement area i s e s s e n t i a l l y f l a t , and devoid o f t r e e s and bushes.

The ground sur face was covered with approximately s i x inches o f snow f o r

t h e f i r s t a i l e r o n t e s t and was grass covered f o r t h e second t e s t . I n bo th

ins tances background no ise l e v e l s were very low except f o r t he occasional

passage o f automobiles and a i r c r a f t .

Desc r ip t i on o f Wind Turbine

The MOD-0 wind t u r b i n e has a two bladed 39 m (128 f t ) diameter r o t o r

mounted on a 36.6 (120 f t ) h igh tower w i t h a twelve s ided cross sect ion.

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The d is tance across the tower, between f l a t s , i s 2.1 m ( 7 f t ) a t t h e base

and tapers t o 1.5 m (5 f t ) a t t h e top.

o f t he suppor t ing tower, operates a t 40 rpm and i s nomina l l y r a t e d a t 200 kW.

I n an attempt t o s imu la te t h e proposed MOD-5A (upwind design) angles of

a t tack , the MOD-0 machine was operated a t 20 rpm and power was l i m i t e d t o

35 kW which i s achieved a t a wind speed o f 4.5 m/s (10 mph).

The r o t o r of t h e MOD-0 i s downwind

Two d i f f e r e n t p a r t i a l span a i l e r o n c o n f i g u r a t i o n s (F igu re 2 ) were

tes ted .

a i l e r o n a lso p i v o t s a t 38% o f t h e chord, but extends t o about 50% o f t h e

chord on the h i g h pressure s ide o f t he blade.

were f i t t e d t o t h e ou te r 6.6 m (21.6 f t ) o f each blade. Blades tapered i n

chord from about 1.22 m ( 6 f t ) a t t he inboard a i l e r o n s t a t i o n (NACA 64624

a i r f o i l ) t o about 0.65 m (2.1 f t ) a t t h e t i p a i l e r o n s t a t i o n (NACA 64615)

and l i k e w i s e t h e t w i s t v a r i e d from 3 O t o lo. The r o t o r blades have a

t o t a l area o f about 26.8 m' (288 f t ' ) , and have roughness s t r i p s extending

from t h e nose o f t h e a i r f o i l t o about 5% chord on bo th surfaces. Data

were taken a t a r o t a t i o n a l speed o f 20 rpm f o r b o t h a i l e r o n c o n f i g u r a t i o n s

and a l s o a t 13.8 rpm for t h e p l a i n a i l e r o n .

The p l a i n a i l e r o n p i v o t s a t 38% o f t h e b lade chord. The balanced

I n b o t h cases t h e a i l e r o n s

Wind Turbine Operat ing Condi t ions

Data f o r t h e p l a i n a i l e r o n were recorded on 17 and 19 January 1984

The temperature range was -12 t o -5OC and between 0900 and 1600 hours.

t h e mean wind v e l o c i t y , V , ranged from about 3 t o 6 m/s (7 t o 13 mph).

Data fo r the balanced a i l e r o n were recorded 11-13 June 1984, t h e tempera-

t u r e range was 2 1 t 0 2 9 ~ C and the mean wind v e l o c i t y ranged from 2 t o 5 m/s

( 5 t o 12 mph).

Wind v e l o c i t y and d i r e c t i o n were monitored and cont inuously recorded

from meteoro log ica l instruments l o c a t e d a t t h e h e i g h t o f t he r o t o r hub and

60 m upwind o f t h e machine. Example t ime h i s t o r i e s o f wind v e l o c i t y and

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c

t

d i r e c t i o n and elect.rica1 power nut.put a r e shown i n F i q u r e 3. The var ia -

t i o n s i n d i c a t e d i n F iqure 3 are representa t ive o f those e x i s t i n g a t t h e

t imes o f t h e t e s t s fo r which data a r e repor ted here in.

Noise Measurements

A l l no ise measurements were made w i t h commercial ly a v a i l a b l e b a t t e r y

powered inst rumentat ion. One-half inch diameter condenser microphones

w i t h a usable frequency range o f 3-20,000 Hz were used w i t h an FM four

channel recorder which prov ides a dynamic range o f about 40 dB i n t h e f r e -

quency range of 0 Hz t o 15,000 Hz.

s i g n a l s were C-weighted i n an attempt t o more e f f e c t i v e l y use the a v a i l a b l e

dynamic ranqe.

For some record inqs t h e microphone

The measurement l o c a t i o n s f o r these t e s t s a re shown i n F igure 4.

Data were obta ined a t a distance, r , o f 57 m (191 f t ) and a t var ious a z i -

muth anqles: O o (on-axis upwind), 90° (crosswind r i g h t ) , 180° (on-axis

downwind) and 27U0(cross i~ ind l e f t ) . Spec t ra l data were obta ined w i t h t h e

a i d of convent ional one- th i rd octave band and narrow band analyzers.

To minimize t h e de t r imenta l e f f e c t s o f wind noise, polyurethane foam I

microphone wind screens were used and microphones were p laced a t t h e

qround surface, where wind v e l o c i t i e s were r e l a t i v e l y low.

While acous t ic s i g n a l s were being recorded on two tape recorder

channels, simultaneous record ings o f t ime code and r o t o r b lade p o s i t i o n

were made on t h e other two tape recorded channels. These l a t t e r data

were used as an a i d i n acous t ic data analyses.

Acoust ic data a re presented f i r s t f o r t h e p l a i n a i l e r o n and then

f o r the balanced a i l e r o n . E f fec ts t h a t are examined i n c l u d e power out -

put, d i r e c t i v i t y and a i l e r o n d e f l e c t i o n angle.

P l a i n A i l e r o n

E f f e c t s o f Power Output - The e f f e c t s of output power, P, on qenerated

no ise a r e shown i n F igures 5 and 6.

t h e upwind measurina s t a t i o n and an a i l e r o n d e f l e c t i o n angle o f 5O.

s o l i d and dot ted curves correspond t o output power c o n d i t i o n s o f 35 KW and

3 KW respec t ive ly . F igure 5 i n d i c a t e s t h a t a t low frequencies t h e h igher

no ise l e v e l s are associated w i t h t h e h igher output power cond i t ion . The

h igher f requencies (F igure 6 ) are associated w i t h t h e b lade boundary l a y e r s

and t r a i l i n g edge f lows and are apparent ly n o t s t r o n g l y a f f e c t e d by an in-

crease i n output power. The spect ra a re l a r g e l y random i n nature w i t h a

few i d e n t i f i a b l e d i s c r e t e frequency components. Those a t 30, 60 and 90 Hz

are associated w i t h t h e e l e c t r i c a l generator and t h e c l o s e l y spaced harmonics

below 30 Hz are apparent ly due t o hlade/tower wake i n t e r a c t i o n s .

Narrowband spect ra a r e presented f o r

The

E f f e c t s o f Tower Wake - It i s known from measurements made on o ther

downwind machines t h a t t h e wake from t h e tower a f f e c t s t h e generated noise.

Ry us ing t h e blade p o s i t i o n i n d i c a t o r as a t r i g g e r s i g n a l i t was p o s s i b l e

t o analyze acoust ic date f o r those t imes when t h e r o t o r blades were approxi-

mately h o r i z o n t a l , thus removing t h e e f f e c t o f t h e tower wake. I t was con-

c luded from comparisons o f these data w i t h those presented i n F igures 5 and

6 t h a t t h e tower wake was responsib le f o r t h e harmonics v i s i b l e below about

30 Hz. The remainder o f t h e spectrum was apparent ly unaf fected.

D i r e c t i v i t y E f fec ts - Comparisons o f t h e measured spect ra a t th ree

d i f f e r e n t l o c a t i o n s are shown i n F igures 7 and 8, i n t h e form o f narrow

band and one- th i rd octave spect ra r e s p e c t i v e l y . The main d i f f e r e n c e s are

noted i n t h e frequency range 400 t o 1600 Hz. Downwind and crosswind l e v e l s

are g e n e r a l l y h igher than upwind l e v e l s .

E f fec ts o f A i l e r o n Angle - Spectra corresponding t o d i f f e r e n t a i l e r o n

angles, a, are shown i n F igures 9 , 10 and 11. F i g u r e 9 i l l u s t r a t e s the

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.

change i n t h e upwind no ise spectrum as t h e a i l e r o n angle changes from

Oo t o 15O. Note t h a t broad peaks develop i n t h e frequency range 400-800 Hz

and t h e peak no ise l e v e l s increase as a i l e r o n angle increases up t o a maxi-

mum of 1 2 O .

l e v e l s decrease.

As t h e a i l e r o n angle i s f u r t h e r increased t h e peak no ise

These peaks have been analyzed i n d e t a i l and a r e determined t o be o f

aerodynamic o r i g i n .

spect ra a re i l l u s t r a t e d i n the narrow band data o f F igures 10 and 11.

For t h e c o n d i t i o n s where resonant peaks e x i s t i n t h e spect ra a howl ing

The na ture o f these peaks and o ther d e t a i l s o f t h e

noise i s observed which dominates t h e o ther no ises from t h i s machine. As

a i l e r o n angle increases there i s a r e d u c t i o n i n t h e frequency o f t h e howl ing

(see F igure 9). This behavior sugqests t h a t t h e source mechanism may be an

edge tone phenomenon i n v o l v i n g some combinations o f upstream and downstream

edges o f the blades, a i le rons , and/or c a v i t i e s associated with the counter-

weiqht mechanisms.

The noise peaks probably r e s u l t from resonat ing c a v i t i e s i n t h e blade,

d r i v e n by edge tones.

n o t necessar i l y be a c t i v a t e d a t other v e l o c i t i e s .

n o t e x i s t a t a lower r o t a t i o n a l speed nor was i t ev ident i n wind t u n n e l

t e s t s o f t h e non- ro ta t ing b lade a t lower s e c t i o n speeds.

Such a mechanism i s v e l o c i t y s e n s i t i v e and would

Note t h a t howl inq d i d

The d i r e c t i o n a l p r o p e r t i e s o f t h e howl ing noise are i n d i c a t e d i n

F i g u r e 1 1 which g ives comparable spectra a t two a i l e r o n angles for upwind,

downwind, and crosswind loca t ions . Noise l e v e l increases are seen t o be

t h e smal lest i n t h e downwind d i r e c t i o n . This r e s u l t i s probably due t o

t h e f a c t ' t h a t t h e d is turbance c r e a t i n g t h e increased noise i s on t h e

upwind s i d e o f t h e b lade and i s thus sh ie lded i n t h e downwind d i r e c t i o n .

The howl ing noise encountered on t h i s a i l e r o n i s be l ieved t o be con-

f i g u r a t i o n s e n s i t i v e and thus rniqht n o t occur f o r o t h e r a i l e r o n designs.

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The edqe tone noise components might however be present on any conf igura-

t i o n hav ing an open spanwise s l o t due t o a i l e r o n deployment.

E f f e c t s o f Rota t iona l Speed - For a l i m i t e d number o f t e s t runs t h e

r o t a t i o n a l speed o f t h e machine was reduced from 20 t o 13.8 rpm.

data a re shown i n F igure 12.

s u l t s i n a general reduc t ion i n t h e noise l e v e l s o f about 8 dB f o r the

same power output.

broadband noise due t o t h e reduced t i p speed.

can be seen i n t h e frequency range 400-500 Hz.

t h e low speed spectrum a t f requencies between 800 and 1600 Hz are noises

o f mechanical o r i g i n and may n o t be associated w i t h t h e wind tu rb ine .

Example

I t can be seen t h a t a r e d u c t i o n i n rpm re-

This r e d u c t i o n i s cons is ten t w i t h t h a t p r e d i c t e d f o r

A t 13.8 rpm no resonances

Note t h a t t h e peaks i n

Balanced A i l e r o n

E f f e c t s o f A i l e r o n Angle - Measured spect ra f o r a range o f a i l e r o n

d e f l e c t i o n angles and power values are shown i n F igures 13 and 14.

On-axis data are shown i n b o t h narrow band and one- th i rd octave band

form. The narrow band spect ra o f F igure 13 are inc luded t o show t h e

character o f t h e r a d i a t e d noise.

g e n e r a l l y random i n na ture wi th o n l y a few r e l a t i v e l y weak d i s c r e t e f re -

quencies present.

o n e - t h i r d octave band form.

Note t h a t t h e s p e c t r a l components a re

The remaining data are presented f o r convenience i n

F i g u r e 14 conta ins spect ra f o r t e s t s i n which the rpm was h e l d

constant and the a i l e r o n d e f l e c t i o n angle was s y s t e m a t i c a l l y var ied.

I t should be noted t h a t under some c o n d i t i o n s t h e wind t u r b i n e was n o t

generat ing power ( d e f l e c t i o n angles o f 6 O and 8O i n F igure 14 b) .

a u x i l i a r y power was supp l ied i n order t o ma in ta in t h e r o t o r speed.

t h e upwind d i r e c t i o n there i s a t r e n d toward h igher no ise l e v e l s a t h igher

d e f l e c t i o n angles, p a r t i c u l a r l y i n t h e frequency range 200-800 Hz. I n

t h e downwind d i r e c t i o n there i s very l i t t l e e f f e c t o f d e f l e c t i o n angle

Thus

In

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J

except a t f requencies below about 125 Hz. I n o ther s i m i l a r t e s t s a t

h igher d e f l e c t i o n angles s i m i l a r r e s u l t s were obtained.

E f f e c t s o f Power - Measurements were made a t f i x e d a i l e r o n d e f l e c t i o n

angles f o r ranges o f wind speed and output power.

p l a i n a i l e r o n i t was concluded t h a t t h e noise l e v e l s o f t h e low frequency

components increased as power increased. The l e v e l s a t h i g h f requencies

a r e r e l a t i v e l y i n s e n s i t i v e t o power changes.

As i n t h e case o f t h e

D i r e c t i v i t y - F igure 15 presents one- th i rd octave band spect ra f o r

measurements made i n t h e upwind, downwind and crosswind d i r e c t i o n s . A t

f requencies below about 500 Hz the noise l e v e l s i n t h e crosswind d i r e c -

t i o n are lower than those on axis, whereas a t h igher f requencies no con-

s i s t e n t d i f f e r e n c e s are d iscern ib le .

i s due t o b lade load ing f l u c t u a t i o n s r e s u l t i n g from i n f l o w turbulence.

This no ise component i s expected t o e x h i b i t a d i p o l e r a d i a t i o n p a t t e r n

with i t s maximum on the a x i s o f r o t a t i o n .

w i t h t h e above observat ion.

The dominant no ise a t low frequencies

Such a p a t t e r n i s cons is ten t

COMPARISONS OF AILERON DATA

D i r e c t comparisons o f t h e data obta ined f o r t h e p l a i n and balanced

a i l e r o n s are g iven i n F igures 16 and 17. F igure 16 presents measurements

made i n b o t h t h e upwind and downwind d i r e c t i o n s , f o r comparable opera t ing

cond i t ions .

h igher no ise l e v e l s than t h e p l a i n a i l e r o n , p a r t i c u l a r l y a t f reqencies

below about 250 Hz.

g u r a t i o n s are nominal ly t h e same a t W O O except f o r smal l d i f f e r e n c e s i n

t h e way t h e a i l e r o n s f a i r i n t o the blade.

t o be responsib le f o r t h e h igher frequency (above 400 Hz) sound l e v e l s

be ing grea ter f o r t h e balanced a i l e r o n i n the upwind d i r e c t i o n .

downwind ( low pressure) s i d e o f the b lade i s i d e n t i c a l f o r b o t h a i l e r o n s

There i s a c l e a r t rend f o r t h e balanced a i l e r o n t o produce

The above r e s u l t i s s u r p r i s i n g because b o t h c o n f i -

These d i f f e r e n c e s are presumed

The

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and t h e h i g h frequency sound l e v e l s show good agreement f o r t h e two con-

f i g u r a t i o n s .

400 Hz i n t h e upwind and downwind d i r e c t i o n s are considerable.

d i f f e r e n c e does n o t e x i s t i n t h e crosswind d i r e c t i o n (F igures 8 and 15).

I t i s expected t h a t t h e dominant no ise source i n t h i s frequency range

i s due t o i n f l o w turbulence, e x h i b i t i n g a d i p o l e r a d i a t i o n p a t t e r n ,

t h e h ighes t noise l e v e l s be ing i n t h e d i r e c t i o n perpendicu lar t o t h e

r o t o r plane.

n o t f o r t h e p l a i n a i l e r o n (F igure 8) .

a i l e r o n t e s t , no ise due t o i n f l o w turbulence was a t a lower l e v e l .

Although atmospheric turbulence was n o t measured, t h e two t e s t s were

conducted under d i f f e r e n t weather cond i t ions , and thus i t can be in-

f e r r e d t h a t the turbulence l e v e l s were h igher f o r t h e balanced a i l e r o n

t e s t .

The d i f f e r e n c e s i n t h e noise l e v e l s a t f requencies below

Such a

This was observed f o r t h e balanced a i l e r o n (F igure 151, b u t

This i m p l i e s t h a t f o r t h e p l a i n

Comparisons o f measured and p r e d i c t e d spect ra f o r b o t h t h e MOD-OA

(40 rpm) and the MOD-O/5A (20 rpm) r o t o r s a r e presented i n F i g u r e 17.

F igure 17(a) shows t h e measured MOD-OA data from Reference 1 compared

t o p r e d i c t i o n s by t h e method o f Reference 2, which incorpora tes empi-

r i c a l c o e f f i c i e n t s based on d e t a i l e d data from one l a r g e machine (MOD-2).

This p r e d i c t i o n model inc ludes c o n t r i b u t i o n s from t h e i n f l o w turbulence,

t h e t u r b u l e n t boundary l a y e r s i n t e r a c t i n g w i t h t h e t r a i l i n g edges and

the wakes due t o t r a i l i n g edge bluntness.

general agreement regard ing bo th t h e s lope as a f u n c t i o n o f frequency

and t h e leve ls . S i m i l a r comparisons f o r t h e slower t u r n i n g MOD-O/5A

r o t o r i n Figure 17(b) show t h e p r e d i c t e d l e v e l s t o be lower than t h e

measured values and furthermore t h e slopes o f t h e measured and p r e d i c t e d

curves do n o t agree. These data suggest t h a t t h e e m p i r i c a l b a s i s f o r

p r e d i c t i n g blade noise may no t be a p p l i c a b l e t o b lades wi th a i l e r o n s , or

Pred ic ted values are i n

. e

L

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t o blades opera t ing a t t i p speeds markedly below approximately 80 m/sec

or both.

CONCLUSIONS

Measurements of no ise from a MOD-0 wind t u r b i n e equipped w i t h two

c o n f i g u r a t i o n s of p a r t i a l span a i lerons, y i e l d e d t h e f o l l o w i n g conclusions:

1. Low frequency (below 100 Hz) no ise l e v e l s increase w i t h in-

creas ing power.

2 . The i n t e r a c t i o n s between t h e wind t u r b i n e b lade and t h e tower

wake produces d i s c r e t e low frequency (below 30 Hz) no ise com-

ponents, b u t does n o t a f f e c t no ise l e v e l s a t o ther frequencies.

The d e f l e c t i o n o f t h e p l a i n a i l e r o n r e s u l t s i n g r e a t l y enhanced

no ise l e v e l s a t 400-800 Hz, reaching a maximum a t 1 2 O a i l e r o n

d e f l e c t i o n . This increased no ise i s apparent ly due t o f l o w

induced resonances o f c a v i t i e s i n t h e blade.

3.

4 . The d e f l e c t i o n o f t h e balanced a i l e r o n r e s u l t e d i n smal ler

increases i n noise l e v e l r e l a t i v e t o those f o r t h e p l a i n

a i l e r o n .

Enhanced no ise l e v e l s due t o a i l e r o n deployment a r e g r e a t e r

i n t h e upwind than i n the downwind d i r e c t i o n .

A t f requencies below about 400 Hz t h e no ise l e v e l s assoc iated

w i t h t h e balanced a i l e r o n are s i g n i f i c a n t l y h igher than those

f o r t h e p l a i n a i le ron .

t h e s t r u c t u r e of t h e atmospheric turbulence f o r t h e two t e s t s

r a t h e r than i n t r i n s i c p r o p e r t i e s o f t h e a i le rons .

5.

6 .

This i s b e l i e v e d due t o d i f f e r e n c e s i n

REFERENCES

- 1. Shepherd, Kevin P. and Hubbard, Harvey H.: Sound Measurements and

Observations o f the MOD-OA Wind Turbine Generator NASA CR 165856,

February 1982.

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- 2. Grosveld, F. W . , Shepherd, K. P. and Hubbard, H. H.: Measurement and

Prediction of Broadband Noise from Large Horizontal Axis Wind Tur-

bine Generators.

Workshop, Cleveland, OH, May 8-10, 1984. (Proposed NASA CP).

Proceedings o f DOE/NASA Wind Turbine Technology

'1

f

-10-

Fiatire 1. General Location o f Test S i t e with Inset Phntoqraphs Showing ElOD-0 ttrind Turbine Generator and rlf.lD-O/',A Model Rotor w i t h Aileron

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r

U- t

i c (b ) Downwind 1

30 k i t I 1 1 I 1 1 ' I ' I I 31 63 125 250 580 1080 2000 4000

-6 -15

ONE-THIRD OCTAVE BRND CENTER FREQUENCY ,HZ

Figure 14. On-axis noise measurements for the MOD-O/5A r o t o r w i th balanced a i l e r o n over a range o f a i l e r o n d e f l e c t i o n angles. r=57 m.

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31 63 125 250 500 1000 2000 4880

ONE-THIRD OCTRVE BRND CENTER FREQUENCY ,Ht

( b ) Downwind b

31 63 125 250 580 1000 2000 4000

ONE-THIRD OCTRVE BRND CENTER FREQUENCY .Hr

F i g u r e 16. Comparisons of on-ax is n o i s e measurements for t h e MOD-O/5A r o t o r w i t h p l a i n and balanced a i l e r o n s . a=O0, V=4-4.5 m/s, P=9-15 kW, r=57 m.

~~ ~~ ~~

0 measured - MOD-OA 0 11

I 1 - Balanced A i l e r o n - P l a i n A i l e r o n - 0 pred ic ted - (Ref. 2 )

t 1 l(a,) :OD-OA Rotor

30 t l l l l l l t l l l I t l l l

31 63 125 250 500 1000 2000 4000

ONE-THIRD OCTRVE BRND CENTER FREQUENCY Hz

\ MOD-0/5A Rotor

31 63 125 250 500 1800 2000 4800

ONE-THIRD OCTFlVE BAND CENTER FREQUENCY HZ

F igu re 17 . Comparisons of measured and p red ic ted one- th i rd octave band spec t ra f o r t he MOD-OA and MOD-O/5A r o t o r s

1. Report No. 2. Government Accession No. 3. Recipient's Gtaicg No.

17. Key WWdr (Suggested by Author(s)) Wind Turbine Generator Noi se Acoust ic Tests A i 1 erons

NASA CR-172427 I I 4. Title and Subtitle I 5. Report Date

' 18. Distribution Statement

Unc lass i f i ed - Un l im i ted

Sub jec t Category - 71

Acoust ic Tests o f the MOD-O/5A Wind Turbine Rotor Wi th Two D i f f e r e n t A i le rons

19. Sacurity aaSSif. (of this report)

Uncl a s s i f i e d

7. Author(r1

20. Security Clauif. (of this pap) 21. No. of Pages 22. Price

Uncl a s s i f i e d 30 A0 3

I 8. Performing Organization Report No.

Kevin P. Shepherd* and Harvey H. Hubbard** , 10. Work Unit No.

9. Performing Organization Name and Address **The Col lege of M i l l i a m & Mary

11. Contract or Grant No. NASl -1 6978/NAG-1-166

*The Bionetics VA Assoc. Research Campus 18 Research Drive , 12970 Je f fe rson Ave.

, 13. Type of Report and Pwiod Covered 23666 Newport News, VA 23606

12. Sponsoring Agency Name and Address Contractor Report

Nat ional Aeronuatics and Space Admin i s t ra t i on 14. Sponsoring Agency && Was h i ng ton, DC 20546 776-33-41 -02

15. Supplemntary Notes This r e p o r t has been prepared j o i n t l y by Kevin P. Shepherd o f the B ione t i cs Corp. under c o n t r a c t NAS1-16978 and Harvey H. Hubbard o f VARC under g ran t NAG-1-166. Langley technica l mon i to r : D. G. Stephens

~~

16. Abstract

Measurements o f no ise have been made f o r a MOD-0 wind t u r b i n e generator r o t o r

equipped w i t h p l a i n and balanced p a r t i a l span a i l e r o n s f o r l i f t and drag c o n t r o l .

Data were obtained f o r a wide range o f a i l e r o n d e f l e c t i o n angles and f o r l i m i t e d

ranges o f wind v e l o c i t y and power ou tpu t .

angles increased and were h igher i n the upwind than i n the downwind d i r e c t i o n .

The p l a i n a i l e r o n e x h i b i t e d a howl ing noise i n the frequency range 400-800 Hz

a t d e f l e c t i o n angles f o r which f l o w induced c a v i t y resonances were s i g n i f i c a n t .

Noise l e v e l s increased as d e f l e c t i o n