advanced biplane blade design - wirz.seas.ucla.edu

Advanced biplane blade design for large-scale wind turbines

UCLA Tech Forum

February 6, 2014 Funding provided by: UCLA Graduate Division • California Energy Commission

Link Foundation • Communities Foundation of Texas • Clean Green IGERT

Perry Roth-Johnson Ph.D. Candidate

Energy Innovation Lab | www.wirz.seas.ucla.edu

UCLA, Mechanical & Aerospace Engineering

Advisor: Prof. Richard Wirz

2 Roth-Johnson & Wirz, Advanced biplane blade design for large-scale wind turbines

Roadmap

Image: Leon Salcedo | flic.kr/p/bLJ5hH

1. Background & motivation for large wind turbine blades

2. Biplane blade concept

a. Aerodynamic studies

b. Structural studies

3. Path forward


Wind turbines are expected to grow

UpWind (2011), “Design limits and solutions for very large wind turbines - A 20 MW turbine is feasible”.

𝑃rotor = 12𝐶𝑝𝜌𝜋𝑅2𝑉3


Challenges for large wind turbine blades

Sandia National Lab | moourl.com/2tbt5

standard compromise:

structures > aerodynamics

Is it feasible to further upscale conventional blades, or is a new design needed?

Blade loads Blade mass


Roadmap






3. Path forward


“Biplane blade” design concept

Wirz (2011), “Advanced Aerodynamic and Structural Blade and Wing Design,” USPTO Int’l App. No. PCT/US11/26367.

Images: Phillip Chiu

biplane

inboard region

monoplane

outboard region

mid-blade

joint

root

joint

Is the biplane blade a feasible design to address the challenges of large blades?

biplane monoplane


Roadmap






3. Path forward


Thick monoplane vs. biplane

Method: 2D, steady-state,

incompressible viscous CFD

(FLUENT commercial CFD code)


Aerodynamic results

Roth-Johnson & Wirz (2012), “Aero-structural investigation of biplane wind turbine blades,” Wind Energy.

biplane monoplane

The biplane is more aerodynamically

efficient than the thick monoplane.


Parametric analysis of biplane airfoils

Wind turbine-specific airfoil:

DU 91-W2-250

Aerodynamic performance with

varying gap, g, and stagger, s

What is the aerodynamically optimal

biplane configuration?

Chiu & Wirz (in preparation), “Aerodynamic performance of biplane airfoils for wind turbine blades”.


Parametric analysis: 2D CFD

[1] Chiu & Wirz (in preparation), “Aerodynamic performance of biplane airfoils for wind turbine blades”.

[2] Drela & Giles (1986), “Viscous-inviscid analysis of transonic and low Reynolds number airfoils. AIAA Journal.

Method: 2D coupled

viscous/inviscid

incompressible CFD

(MSES research code2)


Parametric analysis: wind tunnel testing

Chiu & Wirz (in preparation), “Aerodynamic performance of biplane airfoils for wind turbine blades”.

Caltech Lucas Wind Tunnel


Roadmap






3. Path forward


How to design the biplane inboard region?

joint length, 𝑟𝑗 =?

gap, 𝑔 =?

[1] Lowe & Satterly (1996), “Comparison of Coupon and Spar Tests,” Design of composite structures against fatigue: applications to wind turbine blades.

The spar is the primary load-bearing component in the blade.1

Glass

Fiber

Reinforced

Plastic


How to design the biplane inboard region?

“Structures-first” approach

for biplane blade

1. Design internal spar

structure

2. Fit airfoil exterior over

spar

2

2

1

1


gap, 𝑔 =?


Want to use a parametric analysis

composite materials tapered spar thickness


gap, 𝑔 =?


Parametric analysis needs fast & accurate tools

[1] Bauchau (1998), Multibody System Dynamics. [2] Hodges & Yu (2007), Wind Energy.

[3] Chen, Yu, & Capellaro (2009), Wind Energy. [4] Otero & Ponta (2010), J. Solar Energy Eng. [5] Roth-Johnson & Wirz (2012), Wind Energy.

Technical University of Denmark |

risoecampus.dtu.dk/Vindenergi/VEA/VIM/Becas.aspx

Alternate approach

1D FEA (DYMORE1) and

2D cross-sectional analysis (VABS2,3)

• Fast computation, with good accuracy2,3

• Modeled conventional blades4

• Validated approach for biplane blades5

Windpower Engineering | windpowerengineering.com

Direct approach

3D finite element analysis (FEA)

• High accuracy

• Time consuming

• Model setup

• Computational time


Sandia completely defined the blade structure

Images: Edward Lin

Griffith & Ashwill (2011), “The Sandia 100-meter All-glass Baseline Wind Turbine Blade: SNL 100-00”.

composite materials tapered spar thickness

100 m


Spars were designed from the Sandia blade

Sandia blade

monoplane spar

biplane spar

spar geometry, composite layup, materials


Equivalent static loads

biplane spar

monoplane spar


Computational model: results

upper inboard element

lower inboard element

Roth-Johnson & Wirz (in review), “Structural design of spars for 100-meter biplane wind turbine blades,” Renewable Energy.


incre

asin

g

join

t le

ngth

-to

-sp

an r

atio

, 𝑟 𝑗

/𝑅

increasing gap-to-chord ratio, 𝑔/𝑐

Parametric analysis: results

1 2 3

4 5 6

7 8 9

10 11 12

13 14 15

1 2 3

4 5 6

7 8 9

10 11 12 13 14 15

(lighter colors are better)

Biplane

should

extend to

~50% span

Roth-Johnson & Wirz (in review), “Structural design of spars for 100-meter biplane wind turbine blades,” Renewable Energy.


Conclusions

The biplane blade is a feasible design for large wind turbine blades.

Showed aero-structural benefit of biplane blade

Structural studies

Searched a large parameter

space in a short amount of time

Found a near-optimum

structural configuration

Aerodynamic studies

Biplanes have improved performance

compared to thick inboard airfoils

Larger gap and stagger tends to

improve performance of biplanes


Roadmap






3. Path forward


Path forward

• Aerodynamic shape optimization

• Full blade analysis

– Structural analysis of staggered biplane region

– 3D FEA: dynamics and buckling

– Torsion/edgewise response

– 3D CFD

– Aeroelastic/fatigue simulations

• Manufacturing & costs


Intellectual property in wind energy

1. Wirz R.E., “Advanced Aerodynamic and Structural Blade and Wing Design,”

PCT Application No. PCTIUS2011/026367, U.S. Patent Application 13/581,278,

filed Aug 24, 2012.

2. Wirz R.E., Aspe S., “Design for High Performance Wind Turbines,” U.S.

Patent Application 13/581,286, filed Aug 24, 2012.

3. Roth-Johnson P., Wirz R.E., “High-Strength Wind Turbine Blades and Wings,”

U.S. Patent Application 61/654708, filed Jul 01, 2013.


Small wind

Max power

Solar: 245 W

Wind: 500 W

solar

wind

3 6 9 12

average annual wind speed [m/s]

1500

800

100

an

nu

al

en

erg

y

ou

tpu

t [k

Wh

/yr]


Acknowledgements

Prof. Richard Wirz Phillip Chiu Edward Lin

advanced biplane blade design - wirz.seas.ucla.edu

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