integrating hyperworks into the development and optimisation of wind turbine rotor blades

EHTC 2011; ACENTISS GmbH © ACENTISS 2011 2.1-1

Approved Center of Engineering, Technology andIn Service Support

The reproduction and distribution of this document as well as the communication of its contents to others without explicit authorisation by ACENTISS GmbH are prohibited. Offenders will be held liable for the payment of damages

Integrating HyperWorks into the Development and Optimisa tion of Wind Turbine Rotor BladesDr. Christoph Katzenschwanz; Wolfgang Kurz

© ACENTISS 2011 2EHTC 2011; ACENTISS GmbH

Agenda

� Presentation of ACENTISS and A2Wind

� Design Process of Rotor BladesLoadingConstraints

� OptimisationDisciplinesMacros to support the optimisation process

� Example

� Conclusion and Outlook


Presentation ACENTISS / A2Wind

Approved Center of Engineering, Technology andIn Service Support Automotive InfoCom Transport &

Environment

Aeronautics Space Defence & Security

• ACENTISS as 100% GmbH of IABG

• up to 30 employees end of 2011

Airframe Primary StructureSystem Integration

Do328 Prop / JetDo328 Prop / Jet

Do728

A380 Pax / FA380 Pax / F

A318 – A321A318 – A321

A300,A330/340A300,A330/340

Fuselage SectionsWing ComponentsFloor Grid

Eurofighter Typhoon

A400M

Fuselage SectionsCargo Door

B787

Aft Pressure Bulkhead

LJ85

Airframe Primary Structure

Avionic Subsystems

AEOLUS II

MON 50

Design & Development


ACENTISS Services & Engagements

� formed as a business company from two established companies

� specialized in design and development of wind energy systems� experienced in developing turbines up to 3 MW rated power, including the

complete design of rotor blades


Agenda




� Example



Design Process

� Structure, aerodynamic and loads are highly coupled� An iterative process is needed to account for the interaction

� Objective of the design process should be revenue / costs but weight is used quite often

aerodynamic

structureloadsgeom

etry

mass, stiffness

loadsge

omet

ry,

aero

dyna

mic

pol

ar

perf

orm

ance

FOCUS 6

In-house tool

Optistruct


lower flange

(bending moments)

web of read spar

(shear forces)

lower skin

(torsional moment)

Typical Components of Rotor Blades

upper flange

upper skin

web of front spar


Constraint: Tip Deflection

� Due to the aerodynamic and mass forces the rotor blade will be deformed

� The rotor blade needs sufficient bending stiffness to avoid a collision with the tower

� From the certification specification a stiffness requirement a ≥ 0.3 b has to be shown


Constraint: Modal Requirements for Rotor Blades

Operational Range

Resonance

flatwise edgewise

Example of a Campbell Diagram for a Wind Energy Converter

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

Rotor Speed [Hz]

Nat

ural

Fre

quen

cy [H

z]

1st Tower Bending

1st Rotor Blade Flapwise

1st Rotor Blade Edgewise

2nd Rotor Blade Flapwise

1st harmonic excitation

2nd harmonic excitation

3rd harmonic excitation

4th harmonic excitation


Example of a Campbell Diagram for a Wind Energy Converter

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 0.50

Rotor Speed [Hz]

Nat

ural

Fre

quen

cy [H

z]

1st Tower Bending

1st Rotor Blade Flapwise

1st Rotor Blade Edgewise

2nd Rotor Blade Flapwise

1st harmonic excitation

2nd harmonic excitation

3rd harmonic excitation




Constraint: Strain Level

� The allowable strain values (tension and compression) of the fibres and the inter fibre failure has to be regarded

� For fatigue a simplified strain level can be used when no detailed fatigue calculation will be used

tension

compression


Constraint: Buckling

� Due to compression or shear loads struts, plates etc. tend to fail

� Large displacements will occur and the aerodynamic is distorted

� Structural integrity is endangered

� A sufficient large buckling factor has to be shown


Source: SGL-Rotec

Constraint: Manufacturing

� Rotor blades are typically manufactured from the main substructuresupper skin with flange

lower skin with flange andweb(s)

� For the flanges, leading and trailing edge typically a constant width of the fabrics is used

� For the layup of the fibres Bi- and Triax-fabrics are used (only 0°, ±45°and 90°fibre angles)

� Sandwich material is used for the web and the skin (e.g. balsa, foam)


Agenda




� Example



Optimisation Discipline

� Optistruct knows different optimisation disciplines liketopology

shapeparameter/sizing.

� For the rotor blade only the sizing optimisation can be used because the outer loft is fixed for aero dynamical reasons

� In earlier optimisations the free size optimisation was usedEach thickness of the plies in each element in the finite element model is variable through a design variable

Optimal strength and stiffness distribution will be found

Structure is manufacturable only at high costs

� The result of the optimisation has to be modified in a way that the manufacturing constraints can be regarded


Comparison Free Size - Sizing Optimisation

+ Maximum design flexibility

+ Easy to define design variables using the gauge function in HyperMesh

+ Buckling load cases tend to high numbers of iteration

− After the optimisation the manufacturing constraints have to introduced in further optimisations

± Number of design variables less than free size optimisation

− Design variables and the connection to the ply thickness has to be done by hand (The gauge function in HyperMesh does not help due to different min and max values)

+ Integrating buckling load cases into the design optimisation is more stable

+ The optimised design is directly manufacturable

Free Size Optimisation Sizing Optimisation

Combining the advantages of both strategies would be best


Macro for the Design Variable - Requirements

� The width of the flanges, leading and trailing edge should be easily adapted using TCL macros

� The flange etc. has to be divided into several properties along the blade length

� The design variables are the thicknesses of the individual plies

� Individual min and max thickness per ply can be applied

� The stacking sequence is ignored using the SMEAR or SMCORE option on the PCOMP(G) cards


Macro for the Design Variable - Implementation

� Several TCL-macros have been developed to support the optimisation process:

macro to change the width of the flange, leading and trailing edge

macro to split the rotor blade in longitudinal direction into different properties and define the design variables

macros to define the constraints and optimisation parameters

and a macro to support an efficient post processing of the results


Agenda




� Example



Results - Optimisation History of a GFRP Rotor Blade

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 5 10 15 20 25 30 35 40

Iteration [-]

norm

alis

ed r

espo

nse

[-]

Total Mass1st mod freq2nd mod freq

Tip disp

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 5 10 15 20 25 30 35 40

Iteration [-]

norm

alis

ed r

espo

nse

[-]


Tip disp

0.0

0.2

0.4

0.6

0.8

1.0

1.2

0 5 10 15 20 25 30 35 40

Iteration [-]

norm

alis

ed r

espo

nse

[-]


Tip disp

blade length ~ 40 m


Result - Thickness Variation of Upper Flange

°

Manufacturing constraint of constant width of flang e, leading and trailing edge is regarded


Result – Thickness of Plies

� From the optimisation a thickness distribution is found which is then processed as ply based laminate property PCOMPP

� Element sets can be generated using EXCEL and a FORTRAN program

� Design guidelines are considered in a semi automatic process

0.0

5.0

10.0

15.0

20.0

25.0

30.0

0 5000 10000 15000 20000 25000 30000 35000 40000 45000

Length [mm]

Thi

ckne

ss U

D [m

m]

0.0

2.0

4.0

6.0

8.0

10.0

12.0

Thic

knes

s B

iax

[mm

]

Flange; SS-UD

Flange; PS-UD

Flange; SS-Biax

Flange; PS-Biax


Objective Function

� Beside the objective minimum weight the target could also be minimum cost when a cost function is included

� A cost function is needed especially when different materials are combined

� E.g. combining glass fibre reinforced plastic (GFRP) with carbon fibre reinforced material (CFRP)

12

88

33

67

0

20

40

60

80

100

120

140

160

GFRP/CFRPflanges

GFRP CFRP cost optimal0

20

40

60

80

100

120

140

160

GFRP

CFRP

Mat

eria

l cos

ts [%

]

Str

uctu

ral m

ass

[%]

12

88

13

4

33

67

10

2

0

20

40

60

80

100

120

140

160

GFRP/CFRPflanges


20

40

60

80

100

120

140

160

GFRP

CFRP

Mat

eria

l cos

ts [%

]

Str

uctu

ral m

ass

[%]

12

57

88

13

4

33

15

9

67

10

2

0

20

40

60

80

100

120

140

160

GFRP/CFRPflanges


20

40

60

80

100

120

140

160

GFRP

CFRP

Mat

eria

l cos

ts [%

]

Str

uctu

ral m

ass

[%]

12

57

25

88

13

4

35

33

15

9

55

67

10

2

25

0

20

40

60

80

100

120

140

160

GFRP/CFRPflanges


20

40

60

80

100

120

140

160

GFRP

CFRP

Mat

eria

l cos

ts [%

]

Str

uctu

ral m

ass

[%]

Cost estimation depends on the blade and the manufacturing process

These results can not be taken as general guideline


Agenda




� Example



Conclusion

� TCL-macros for the definition of the optimisation task helpto reduce the time for the setup,

to increase the reliability of the process andthe optimisation know how is able to be used by all involved persons.

� Due to the shorter set up time for the optimisationmore design variants can be analysed in the same time,

design decisions are based on a fundamental analysis/optimisation rather than instinct and

customers get lightweight rotor blades.


Outlook

� Further development will be done to integrate all the tools within a user panel / browser

Setup model and design variables

Define constraints and optimisation parameters

Support of postprocessing


Thank you for your attention

ACENTISS GmbH

Dr. Christoph KatzenschwanzResearch & Technology, Innovations

Einsteinstrasse 28a85521 OttobrunnGermany

E-Mail [email protected] www.acentiss.de

A2Wind GmbH

Wolfgang KurzTechnical Manager Wind Energy

Einsteinstrasse 28a85521 OttobrunnGermany

E-Mail [email protected] www.a2wind.net

integrating hyperworks into the development and optimisation of wind turbine rotor blades

Business

acentiss gmbh acentiss

acentiss services engagements

rotor bladesexample

rotor blade flapwise2

manufacturing rotor

iterative process

sizing optimisation

free size optimisation