design and blade optimization of contra rotation double rotor

International Journal of Mechanical & Mechatronics Engineering IJMME-IJENS Vol: 11 No: 01 17

115301-7474 IJMME-IJENS © February 2011 IJENS I J E N S

Design and Blade Optimization of Contra Rotation Double Rotor Wind Turbine

Priyono Sutikno

1, Deny Bayu Saepudin

2

1Institut Teknologi Bandung, Bandung, Indonesia, [email protected]

2Institut Teknologi Bandung, Bandung, Indonesia, [email protected]

Abstract-- The Intelligent Wind turbine (IWT) has two stages

blades contra rotation. This kind of wind turbine has

characteristic self regulated on the speed due to the difference torque between two stages horizontal axis wind turbine, than

no need the pitch controller to control the speed and cut off the

wind turbine due to the high wind speed.

The research of IWT is designed first by optimize several

important design parameters, as a blade section profile and the multiplier factor of the angle of attack. The design parameter

results are the NACA 6412 is selected as the optimum blade

section profile and the optimum value of angle of attack

multiplier factor is 0.5. The designed IWT has 3 blades for

each front and rear rotor. The research intelligent wind turbine has 600 mm front diameter and 600 mm rear blade

diameter. The characteristics of IWT were simulated by using

Computational Fluid Dynamic (CFD) software, demonstrated

the non entrainment of the contra rotation, each blades should

have the same produced torque.

Index Term-– Intelligent Wind Turbine, Numerical

S imulation, Contra rotation Wind Turbine

I. INTRODUCTION

The conventional wind turbines with large sized wind

rotor generate high output in the moderately strong wind.

The output of the small sized wind rotor is low such a wind

rotor is suitable for weak wind. That is, the size of the wind

rotor must be appropriately selected in conformity with

potential wind circumstances. Besides, in general the wind

turbines are equipped with the brake and or the pitch control

mechanis ms, to control the speed due to the abnormal

rotation and the overload generated at the stronger wind, and

to keep the rotation of generator. In that sense, some studies

present a good review of various invented the superior wind

turbine generator, T. Kanemoto [1] has invented Intelligent

Wind Turbine Generator (IWTG) composed of the large

sized front wind rotor, the small sized rear wind rotor and

the peculiar generator with inner and the outer rotational

armatures, as the rotational speeds of the tandem wind rotor

are adjusted pretty well in cooperation with the two

armatures of the generator in response to the wind speed.

The IWTG model is composed of tandem wind rotor using

the flat b lades, and demonstrated the fundamentally superior

operation of the tandem wind rotor. In this paper, the effect

of the blade profiles using NACA profiles on the turbine

using numerical simulation on the turbine performances are

investigated to optimized the rotor profiles.

Nomenclature

A Area

a Axial induction factor

a’ Radial Induction factor

B Number of blade

CD Drag coefficient

CL Lift coefficient

c Chord length

Cp Power Coefficient

D Diameter

Fx Axial Force

g Acceleration of gravity

L Lift force

P Power

p pressure

Q correction factor

r local radius element rotor

Re Reynolds number

R Radius

T Torsi

T Thrust

Vo Absolute Velocity

w Relative velocity

u Tangential velocity

x Local speed ratio

α angle of attack (AOA)

β stagger angle

e Ratio coefficient Lift and Drag

γ pitch angel

η Efficiency

λ Tip speed ratio

ρ density

angle of attack relative

σ Solidity

Ω Angular velocity

II. OPERATION OF TANDEM WIND ROTORS

In the IWTG both wind rotors start to rotate at low wind

speed, namely cut in wind speed, but the rear wind rotor

counter rotates against the front wind rotor. The increase of

the wind speed make the both rotational speeds increase,

and the rotational speed of rear wind rotor becomes faster

than that of the front wind rotor because of its small size.

The rear wind rotor reaches the maximum rotational speed

at rated wind speed. With more increment of the wind

speed, the rear wind rotor decelerates gradually and begins

to rotate at the same direction of the front wind rotor so as to

coincide with larger rotational torque of front wind rotor.

Such behaviour of rear wind rotor is induced from the

reason why the small sizes wind rotor must work as the

blowing mode against the attacking wind because the wind

rotor turbine mode can \not generate adequately the

rotational torque corresponding to the front wind rotor. The



behaviour of the front and rear wind rotors also depends on

the blade profiles and flow condition between both rotors,

and will be d iscussed. The rotational direction and speed of

the rotors are adjusted in response to the wind circumstance

(see fig. 2)

Fig. 1. Drawing IWTG [1]

Fig. 2. Operation of IWTG [1]

The authors has proposed the optimized blades with adopted

the NACA Air foils for rear and front blades of the contra

rotation wind turb ine. It is d ifficult, however to know the

rotational torque but also to get optimized b lades profiles,

using the contra rotation model. In order to elaborate and to

get the optimized blades, the model was separated from

tandem to single isolated wind turbine, however the rear

turbine has the velocity data’s from the front wind turbine

blade simulation.

III. AIR FOIL AND ROTOR PERFORMANCE ANALYSIS

Airfo il has made rotor possible to rotate in high speed

and load, early aerodynamics of wind turbine has based on

theory of air p lane wings. However, aerodynamics of wind

turbine has been required different idea, the accuracy of

rotor performance analysis depend mainly on the treatment

of the wake effect, because the wake of propeller type wind

turbine is induced a large velocity in rotor plane. For

Horizontal Axis Wind Turb ine blades the aviation airfoils

such as NACA series have been widely used. But these air

foils have been recognized to be insufficient for

requirements, such reduction of rapid stall characteristics,

in-sensitivity to wide Reynolds number the range of

between 5.105

to 2.106. Rotor performance analysis has been

performed using several methods. The Blade Element

Momentum (BEM) method is mainly employed as a tool of

performance analysis because of their simplicity and readily

implementation. Vortex wake methods can adequately treat

the effect of wake vortices and have some advantages over

BEM.

3.1 Blade Element Momentum Method

Most wind turbine design codes are based on Blade

Element Momentum (BEM) method [7]. The basic BEM

method assumes the blade can be analyzed as a number of

independent elements in span wise direction. The induced

velocity at each element is determined by performing the

momentum balance for an annular control volume

containing the blade element. The aerodynamic fo rces on

the element are calculated using lift and drag coefficient

from empirical two dimensional wind tunnel test data at the

geometric angle of attack (AOA) of the blade element

relative to the local flow velocity.

BEM method have aspect by reasonable tool for designer,

but are not suitable for accurate estimation of effect of wake,

complex flow such as three dimensional flow or dynamic

stall because of their assumption.

3.2 Vortex Wake Method

The induced velocity in the rotor plane of Horizontal

Axis Wind Turbine (HAWT) is largely increased in heavy

loading condition and the wake vortices of HAWT develop

to the downstream constructing highly skewed vortex sheet

in largely decelerated axial flow near rotor plane. Thus

determination of the velocity induced by wake and wake

geometry is one of the most important aspects in the rotor

performance analysis.

Vortex wake method directly calculates the induced

velocity from the bound vortices of blades and the trailing

vortex in wake which are represented by lifting line or

lifting surface model [4]. The treatment of wake geometry

can be classified roughly into two type, as a prescribed wake

model and free wake model. In the former model the wake

represented by a line a vortex or spiral vortices with fixed

pitch. In later one a fractional step scheme is adopted and

the configurations of the wake are calcu lated at every t ime

step using local velocity including the components induced

by wake and bound vortices. The free wake model is

generally tackled with vortex lattice method which can fit on

arbitrary blade shape with camber, taper and twist.

Another method of the vortex wake methods is use of an

asymptotic acceleration potential. Accelerat ion potential

method is basis on the Laplace equation of pressure

perturbation. The rotor b lades are represented in the model

as discrete surfaces on which a pressure discontinuity is

present. The model implies the presence of span wise and

chord wise pressure distributions, which are composed of

analytical asymptotic solution for Laplace equation. More

elaborate model makes it possible to calculate the dynamics

load caused by dynamic inflow and yawed inflow situation

[5].

3,3 Computational Fluid Dynamic

Recent development of the computational fluid dynamics

(CFD) allows us to simulate overall flow around HAWT

including tower and nacelle. In 1999 Duque et al. [6]



calculated aerodynamics of HAWT using RANS model and

overset grids to facilitate the simulation of flow about

complex configuration. Recently, some CFD’s codes

actively are developed of CFD analysis of rotor flow by

three dimensional Navier Stokes code.

Though the state of the art CFD is needed considerable

computer power and validation for Navier Stokes model,

CFD has potential advantage for detailed understanding of

aerodynamic of the HAWT.

IV. OPTIMAL ROTOR BLADE

4.1 The NACA series air foil

The design model, which is composed of tandem wind

rotor, designed based on Blade Element Momentum (BEM)

method. The design is used the 4 (four) d igit NACA airfoil

and to be chosen among 7 (seventh) airfoil profile as shown

at fig. 3.

A : 1st

digit is the percent of chord

B : 2nd

digit is the ten percent of the chord

C : 3rd

and 4th

digit is the percent of chord

Fig. 3. Airfoil Profile of 4 digit s NACA XXXX

The criteria of NACA airfoil to be implemented to the front

rotor and rear rotor, the XFOIL software is used to

simulated the Lift and Drag Coefficient at function of AOA,

the criteria’s are

a. The airfoil has a good performance, should have as

bigger as possible the ratio of the ratio the Lift and

Drag coefficients as shown at Table I.

b. The section of the airfoil has simple fo rm possible,

which has a flat suction in order to simply the

blades manufacturing, see Fig. 3.

T ABLE I

T HE MAXIMUM LIFT AND DRAG RATIO OF NACA 5 AND 6 SERIES

Beside the Lift and Drag Rat io, the camber to chord ratio

can be influenced the Lift to Drag Ratio, and as shown at

fig. 4. The NACA airfo il has been chosen, have a certain

AOA at the maximum Lift to Drag Ratio.

The number of blades at the front and rear rotor depend on

the velocity to tip rat io as shown at table II [5]. The rotation

of the front and rear rotor depend on the tip speed ratio, for

tip speed ratio between three and more than four, the

number of rotor is three.

T ABLE II T HE NUMBER OF BLADE DEPEND ON SPEED TIP RATIO Λ

λ B [number of blade]

1 8 – 24

2 6 – 12

3 3 – 6

4 3 – 4

More than 4 1 – 3

The rotor performance analysis of IWT has been calculated

by the model Actuator Disc and Blade Element Momentum.

This method has been modelled and developed by Glauert

(Ingram, 2005), the inflow near the rotational b lade or disc

as the induced velocity in the rotor plane is largely increased

and represent by rotational inflow factor.

The aerodynamic forces on element are calcu lated using the

lift and drag coefficient from XFOIL software.

Fig. 4. The Lift to Drag ratio of the NACA XXXX series

The optimum blade can be concluded by comparing the data

on table I and performance of b lade in the fig. 1 and 4 with

respect to the criterion above, the chosen blade has thickness

to chord ratio of 12%, the camber to chord ratio is 6% and

the air foil NACA 6412 is chosen as airfoil for front and rear

rotor.

4.2 Optimal rotor blade using GLAUERT-PRANDTL-

XU model.

The calculat ion is based on the Blade Element

Momentum (BEM) method, this method is suitable for

engineering development and there are two kinds of

categories: fixed pitch and variables pitch rotor blade. The

blade length is divided into several small elements for which

the two dimensional airfoil theory can be applied. The

dimensionless coefficient, CL and CD, the net force, power

and torque caused by B blades, each of local chord c, are as

follow [6]:



For torque:

BcΔccosD

CsinL

Cr2ρW21ΔQ (1)

For power:

rBccosD

CsinL

Cr2W21QP (2)

For thrust:

rBcsinD

CcosL

C2W21T (3)

where sin

uW =

cos

wr

Fig. 5. Local element velocities and flow angles [8]

Based on actuator disc theory and Using dimensionless axial

and radial induction factor,

0

0

V

uVa

and

r

w'a

and

solidity,R

Bc

we find equation above became

Fig. 6. Local elemental forces [8]

2

DL

sin

sinCcosC

r8

R

a1

a (4)

cossin

cosCsinC

r8

R

'a1

'a DL (5)

Also we have

wr

utan

'a1r

a1V0

'a1x

a1

(6)

where, x =

0V

r, is local speed ratio. At the end of the

blades, r become R, and we find the most important

parameter for wind turbine rotors, the tip-speed-ratio,

or

0V

RX

, using X , we can

write,

'a1

a1

rX

Rtan , the two dimensional lift and

drag coefficients CL and CD are both function of angle of

attack

L

D

C

C , Instead of using the average

solidity, it’s define a symbol called the blade loading

coefficient,r.8

Bccl

, using and

sin

cot

a1

a (7)

And

sin

tan

'a1

'a (8)

To obtain a single point optimum including the effect of

drag, deriving a local power coefficient [6],

3

0

DL

2

3

02

1

'

PV2

)cosCsinC(BcW

AV

PC

(9)

where,

drBccosCsinCΩrρVΩdQdPDL

2

total2

1

and dA =2 π dr by using :

222222

totala1ra1UV

and equation 6, then

equation 9 can be write

cosεφsinxλ4cot1a1C 22

p

(10)

Then, eliminating λ using equation 7 and expanding 1/(cot

+ ε) in a Taylor’s series of two terms, there results

tan1tana1xa4Cp

(11)

Since the optimum value of a is founded to be quite

insensitive to changes in ε, this implies that pC decreases

monotonically as ε increases. By defining a local Froude

efficiency (Eq. 12), we can relate the performance of each

blade element to the ideal value of unity [6].

pFC

16

27

(12)

The correction factor for total losses can actually be quite

well represented by Prandtl and Xu represent the tip losses

and hub losses, the equation is quite simple but can give the



good matched on HWAT (Horizontal Axis Wind Turbine)

[10], the Prandtl tip correction factor is

12cos exp 7tip tip tipQ f if f

1 7tip tipQ if f (13)

2 sin

tip

B R rf

r

And for hub correction factor can be written as

12cos exp 7hub hub hubQ f if f

1 7hub hubQ if f (14)

2 sin

hub

hub

hub

B r Rf

R

Early 2001, Xu proposed the correction factor on hub losses

by using the Prandtl correction factor as written above and

the Xu correction factor for hub can be written as

0,85

0,5 0,5 0,7 1new

tip tiprQ Q if

R

(15)

/ 0,71

1 0.70,7

tip r Rnew

tip

r QrQ if

RR

Flowchart in fig. 7 exp lained the complete procedures of

rotor turbine design. This flow chart refers to optimum

design procedure of rotor blade and the source program is

written in FORTRAN code, while XFOIL is used to obtain

the Lift coefficient and Drag coefficient of airfo il data which

is chosen for blade design. After obtaining the Lift and Drag

Coefficients an interpolation is performed to justify

Reynolds number and angle of attack (AOA) on calculat ion

XFOIL or two dimensional flow over the airfoil by Fluent.

Fig. 7. Flowchart to calculate forces and power at the optimum

performance

Wind turbine rotor with three blade formed by several airfoil

profile with s maller chord length from hub to tip every blade

along the span. Fig. 8 displayed graphic of



Fig. 8. Graphic of distribution of chord length and twist angle at rotor span

chord length and stagger angle in function of angle of attack

(AOA).

Fig. 9 shown graphic of the torque and the efficiency curve

versus the rotational speed and the fig. 10 shown graphic of

the torque and efficiency versus rotational velocity results of

the numerical simulation using the FLUENT software. Fig.

11 shown graphic of the efficiency as functions of the

velocity source calculated manually and simulated three

dimensional numerically using the FLUENT.

Fig. 9. Graphic of torque versus rotational speed calculated and simulated

numerically

Fig. 8 to 9 shown the graphics of chord length versus span

length of rotor, the torque versus rotational speed and the

efficiency versus rotational speed respectively, these results

has been calculated by PRANDTL-XU correction equation

and simulated numerically using the FLUENT 6.3.26. We

can concluded the optimum performance is used the angle of

attack with 6,0 to be chosen with regard of

The Maximum efficiency is near of the working or

design point at the rated rotation

The produced torque has relatively high

The values of the efficiency of the wind speed

region (2 until 12 m/s) are always relatively h igh

and stable as shown at fig. 11.

Fig. 10. Simulation result using the Blade Element Momentum and

Prandtl_Xu correction factor on efficiency versus rotational speed

The optimum blade is NACA 6412, blade has thickness to

chord ratio of 12%, the camber to chord ratio is 6% and the

angle of attack is 6,0 multiplier.



Fig. 11. The efficiency versus wind speed

V. DESIGN AND SIMULATION OF THE IWT

5.1 Design Procedures for Wind Turbine Rotor

Flowchart in fig. 7 explained the complete procedures of

rotor turbine design. This flowchart refers to optimum

design procedure of rotor b lade, and the source program is

written in EXCELL code, while the XFOIL or FLUENT

software is used to obtain lift coefficient (CL) and drag

coefficient (CD) of airfo il data which is chosen for the blade

design. After obtaining the lift coefficient (CL) and drag

coefficient (CD), an interpolation is performed to justify

Reynolds number and angle of attack on calculation.

5.2 Simulation Procedures for Intelligent Wind Turbine

Front and Rear Rotors

The simulation of Intelligent Wind Turbine front and

rear rotors are using computational flu id dynamic (CFD)

method through Fluent software. The simulation process

consists in two parts, the two dimension model and three

dimension models. Two dimension model is using FLUENT

DDP to calculate lift coefficient (CL), drag coefficient (CD),

pressure coefficient and flow characteristic through airfoil

profile in two d imension, while Fluent 3D is used to

calculate force components which rotor produced and flow

characteristic in three dimension, especially flow behind the

rotor which shown velocity decrease and wind energy,

turbulence, and wake.

The two d imension simulat ion proposed to obtain airfoil

characteristics which will be used in b lade design with angle

of attack variation and Reynolds number variat ions, then

served as an input on blade design by using interpolation.

The airfoil profile has been calculated and simulated at

section 4.

Two dimension simulat ion process is completed by Gambit

meshing around 66.000 cells and iterat ion using FLUENT

2DDP with assumption of compressible flow and coupled

solver was used including energy calculation using absolute

velocity formulation in steady condition. These assumptions

are requisite in order to obtain accurate current model on

airfoil surface by showing turbulence phenomenon, flow

separation, boundary layer, and reversed flow. This flow

phenomenon is their natural flow characteristic, where the

decreasing of whole airfo il performance and rotor efficiency

in extreme situation [9].

The result of calculat ion for the front and rear rotor can

be shown as bellows:

Fig. 12. Result of distribution of chord length (c) of the front and rear rotor span of IWT

Fig. 13. Result of distribution of pitch angle of the front and rear rotor span

of IWT



Fig. 14. The front at the left fig. and rear rotor at the right

5.3 The three Dimensional Model Simulation of the IWT

front and rear rotor.

The analyzed aerodynamic problem is flow detriment

including wake around rotor, distribution of velocity and

pressure decrease in axial direction. The first simulat ion is

made to a front rotor with 60 cm diameter which placed in a

cylinder wind tunnel with 150 cm diameter and 300 cm

length. Flow condition is steady, front rotor speed constantly

at 600 rpm and t ip speed ratio of 3.142 wind condition for

rear rotor can show at fig. 15.

Fig. 15. Position of the pickup velocities and pressures from the front rotor

blade

directions are assumed uniform velocity input before hits the

rotor. The second simulation is made a rear rotor with 60 cm

diameter, the boundary condition of the input rear blade are

the velocity vectors output from the first simulation of the

front blade. The pickup boundary

Three dimension wind turbine rotor is produced using

3D Inventor modeling program (Inventor 2008) version.

Blade is made of several airfoil profiles along the span using

blend method to form blade with twist pattern, previously

these airfo il profiles were kept in *.sec format. Afterwards,

the blade making result that produced by Inventor 2008 are

exported to Gambit in *.igs format.

Fig. 16. Intelligent Wind Turbine, the front and rear blades in isometric and

front view

Front rotor

Axis of rotor

Rotor axis

Blade 3

Blade 2

Blade 1



Modeling process in Gambit is making meshing around

6.0 million cells (TGRID) and defin ing boundary

conditions. Modeling in Gambit taking the wind tunnel

analogy as boundary conditions, and there is only one

volume control around rotor as rotating frame. In Fluent, the

fin ishing process is using segregated solver model with

relative velocity formulation or multip le reference frames

(MRF) model and steady conditions . It is important to do the

relative velocity formulation because the volume control

that used is rotating frame (non inert ia) [2], in order to

analyze relat ive velocity impact to a rotor and exposed

current flow behind the rotor (wake) [9]. The expected result

in 3D simulation is to get far flow around rotor, not just only

at the rotor surface. The applied viscous model is the same

model that applied in 2D simulat ion wh ich is viscous k-ε

model [8], [10].

VI. RESULT AND DISCUSSION

Two dimension and three dimension rotor turbine are

analysis using optimum blade design and calculated with

BET PRANDTL-XU methods or designed and simulated by

3D Fluent indicates a good results and have same similitude.

If we compare both analyses result by fluent and by BET

PRANDTL-XU methods, it turned out that there is only

small d ifference on calculation results of resultant velocity.

It is showed by calculation result of velocity resultant

distribution along the blade shown at fig. 9 and 10, where

the torque is 17 Nm and the efficiency is 35% at 500 rpm

and by using numerical simulation Fluent, the torque is 0.14

Nm and the efficiency is 30% at 500 rpm. The same way the

efficiencies calculated by both methods has a same tend.

Fig. 17. Simulation result of the torque and efficiency curve of the front and rear rotor IWT

The BET-PRANDTL-XU method has been used for the

front and rear rotors optimum design condition and

produced the front and rear rotor blades as shown at fig. 14

above. The numerical simulat ion used FLUENT to get the

performance shown at fig. 17 is the numerical simulat ion

result give the torque and the efficiency curves in function

of rotation speed of the both rotor, front and rear rotor

blades. The simulation is conducted by separate the front

rotor as a single wind turbine. To get the result of rear rotor

numerical simulation, the boundary condition should be

setup from the output of the front rotor numerical

simulation. The boundary condition for the rear rotor has

been taped as shown at fig. 15, there are several pick up

data’s in the radial direction and data’s at direction of flow

in the upstream and downstream as we can see at z1, z2 and

z3. The p ickup data at radial d irection are indicated by raw r1

until r5. The 3 dimensional IWT design can be seen at fig.

16, the front rotor has 3 blue blades and the rear blade rotor

has green color. The result of numerical simulat ion using the

FLUENT has results as shown at fig.18, the efficiency curve

of IWT versus wind velocity and fig. 19 shown the

characteristic of the rotational velocity relative of the front

and rear blades depend on the wind velocity.

Fig. 18. Efficiency Curve of IWT

Fig. 19. IWT Rotational speed versus wind speed

In the classical wind turbine, there are two ways in

controlling the output of wind turbine power, they are:



1. Blade pitch controlled wind turbine

2. Stall controlled wind turbines; passive stall controlled

wind turbines and active stall controlled

On the Intelligent Wind Turbine (IWT) with contra rotation

rotor blades has speed adjustment depend on the wind speed

as shown at fig. 17. The IWT both rotors start to rotate at

low wind speed, namely cut in wind speed, but the rear rotor

contour rotates against the front rotor. The increase of the

wind speed make the both rotational speeds increase, and

the rotational speed rear rotor become faster than that of the

front rotor. At wind speed of 4 m/s the rotational of front

rotor is 400 rpm and rotational speed of rear rotor is -400

rpm and until wind speed of the 6 m/s, the rotational of front

rotor is 600 rpm and rotation of rear rotor is -500 rpm, that

means the relative rotational velocity is 1100 rpm and IWT

has maximum efficiency of 27%.

At the wind speed more than 7 m/s, the rotational speed of

rear rotor decreased until the wind speed 11.5 m/s, the

rotation speed direction of both rotor, front and rear rotors

has a same direction but the relative rotational speed remain

same is 1100 rpm.

VII. CONCLUSION

The IWT which composed of tandem rotors and contra

rotation has characteristic superior as the conventional wind

turbine, than no need pitch control or stall control to

controlling the rotational speed when wind speed became

too high. The IWT can start rotate on weak wind speed. At

moderate wind speed IWT can rotated relatively on

adequate rpm, because the IWT has contra rotation rotor.

When the wind speed increased, the relative rotational speed

remain constant, event at high wind speed the relative

rotational speed rema in constant about 1100 rpm, the rear

rotor has been entrainment by the front rotor and rotated at

same direction.

The numerical simulat ion was demonstrated the

direction of the rotation of both front and rear rotor should

have a same order torque. The method to get the optimum

blade profile and the numerical simulation can be used as

preliminary design and to get the estimated characteristic of

contra rotation blade span.

ACKNOWLEGMENT

This works was supported by Riset Unggulan 2010 LPPM

(Research and Service to the Community Institute)

INSTITUT TEKNOLOGI BANDUNG.

REFERENCES [1] Toshiaki Kanemoto. and Ahmed Mohamed Galal. 2006.

Development of Intelligent Wind Turbine Generator with Tandem Wind Rotor and Double Rotational Armatures, Series B, Vol. 49 No 2, JSME International Journal.

[2] Dahl K. S., et al., Experimental Verification of the new RISO-Al

Airfoil family for wind turbine, Proc of EWEC’99, 1999, pp 85-88 [3] Wilson, R.E., and Lissaman, P.B.S., Applied Aerodynamics of

Wind Power Machine, NTIS PB 238594, Oregon State University,

1974 [4] Afjeh, A.A., and Keith Jr. T.G. A Vortex Lifting Line Method for

the analysis of Horizontal Axis Wind Turbine. Transaction of ASME, Journal of Solar Energy Engineering, Vol. 108, 1986, pp.

303-309

[5] Hasegawa Y., et al., Numerical Analysis of Yawed Inflow Effect on a HAWT Rotor. Proc. of 3

rd ASME/JSME. Joint Fluid Engineering

Conference FEDSM 99-7820. 1999. [6] Duque, E.P.N., et al., Navier-Stokes Analysis of T ime Dependent

Flow about Wind Turbine, Proc. Of 3rd ASME/JSME Joint Fluid

Engineering Conference, FEDSM99-7814, 1999.

[7] Priyono Sutikno, Numerical Optimization of Wind turbine blades. Proceedings of the International Conference on Fluid and Thermal Energy Conversion 2003.

[8] Verdy Kohuan, Priyono Sutikno., Aerodynamic Design and Analysis of Wind Turbine Blade Propeller Type with Power 500 kW, Proceedings of the International Conference on Fluid and Thermal Energy Conversion 2006 , FTEC 2006, Jakarta,

Indonesia, December 10 – 14, 2006, ISSN 0854 – 9346 [9] Moriarty P., Hansen A., (2005). Aero Dynamic Theory Manual,

National Renewable Energy Laboratory, NREL/TP-500-36881. [10] Fluent 6.3.26 Documentation User Guide (2008)

design and blade optimization of contra rotation double rotor

Documents