IP Library › Granted Patent US 8,197,218
Granted Patent B2
US 8,197,218 · App. 11/937,183 · Granted Jun 12, 2012

Quiet airfoils for small and large wind turbines

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Quick Facts
Patent No.
US 8,197,218
App. No.
11/937,183
Granted
Jun 12, 2012
Kind
B2
Abstract

Thick airfoil families with desirable aerodynamic performance with minimal airfoil induced noise. The airfoil families are suitable for a variety of wind turbine designs and are particularly well-suited for use with horizontal axis wind turbines (HAWTs) with constant or variable speed using pitch and/or stall control. In exemplary embodiments, a first family of three thick airfoils is provided for use with small wind turbines and second family of three thick airfoils is provided for use with very large machines, e.g., an airfoil defined for each of three blade radial stations or blade portions defined along the length of a blade. Each of the families is designed to provide a high maximum lift coefficient or high lift, to exhibit docile stalls, to be relatively insensitive to roughness, and to achieve a low profile drag.

Claims (443)

1. A blade for large wind turbines rotatable about a horizontal axis, the blade being adapted for mounting to a hub on the turbines for rotation about said horizontal axis and extending a distance radially outward from the horizontal axis to a tip, the blade comprising:

a primary span region extending from a point that is approximately sixty-five percent of the distance radially outward from the horizontal axis to a point that is approximately eighty-five percent of the distance radially outward from the horizontal axis; and

a primary airfoil in the primary span region, the primary airfoil having a thickness of at least about twenty-one percent, a Reynolds number of at least about 4,000,000, and a maximum lift coefficient of about 1.6.

2. The blade of claim 1 , wherein the blade has a length in the range of about 20 to 50 meters as measured from the horizontal axis to the tip.

3. The blade of claim 1 , wherein the primary airfoil further comprises:

an upper surface and a lower surface, both of which extend spaced-apart in relation to each other from a leading edge to a trailing edge; and

a chord line with a length c extending in a straight line between the leading edge and the trailing edge, said upper surface and said lower surface having shapes and contours expressed by x/c values and y/c values, wherein the x/c values are dimensionless coordinates that represent locations on the length of the chord line and the y/c values are dimensionless coordinates that represent heights from the chord line to points on the upper surface and on the lower surface substantially as follows:

Upper

Lower Surface

Surface

x/c

x/c

y/c

0.00006

0.00112

0.00004

−0.00084

.00321

.01040

.00041

−.00254

.01104

.02127

.00138

−.00406

.02343

.03307

.00288

−.00560

.04015

.04540

.01318

−.01192

.06101

.05794

.02942

−.01794

.08576

.07041

.05165

−.02385

.11413

.08253

.07932

−.03013

.14580

.09406

.11146

−.03674

.18042

.10474

.14756

−.04351

.21762

.11434

.18687

−.05030

.25699

.12262

.22887

−.05701

.29810

.12934

.27253

−.06393

.34048

.13417

.31589

−.07002

.38383

.13653

.35873

−.07334

.42854

.13632

.40193

−.07288

.47434

.13395

.44627

−.06859

.52084

.12962

.49216

−.06086

.56764

.12354

.53971

−.04984

.61431

.11592

.59018

−.03645

.66042

.10703

.64307

−.02282

.70550

.09715

.69724

−.01029

.74904

.08657

.75132

.00013

.79053

.07559

.80381

.00775

.82943

.06449

.85314

.01212

.86518

.05352

.89755

.01296

.89719

.04283

.93491

.01083

.92504

.03222

.96391

.00721

.94908

.02179

.98422

.00357

.96943

.01245

.99611

.00096

.98554

.00533

1.00000

.00000

.99621

.00120

1.00000

.00000.

4. The blade of claim 1 , wherein the primary airfoil is positioned at a blade radial station of about 0.75.

5. The blade of claim 1 , further comprising:

an intermediate span region extending from a point that is approximately eighty percent of the distance radially outward from the horizontal axis to a point that is approximately one hundred percent of the distance radially outward from the horizontal axis; and

an intermediate airfoil positioned radially outboard from the primary airfoil in the intermediate span region, the intermediate airfoil having a thickness of at least about eighteen percent, a Reynolds number of at least about 3,500,000, and a maximum lift coefficient of about 1.5.

6. The blade of claim 5 , wherein the intermediate airfoil is positioned at a blade radial station of about 0.90.

7. The blade of claim 5 , wherein the intermediate airfoil further comprises: an upper surface and a lower surface, both of which extend spaced-apart in relation to each other from a leading edge to a trailing edge; and

a chord line with a length c extending in a straight line between the leading edge and the trailing edge, said upper surface and said lower surface having shapes and contours expressed by x/c values and y/c values, wherein the x/c values are dimensionless coordinates that represent locations on the length of the chord line and the y/c values are dimensionless coordinates that represent heights from the chord line to points on the upper surface and on the lower surface substantially as follows:

Upper Surface

Lower

x/c

v/c

Surface

x/c

0.00004

0.00088

0.00004

−0.00080

.00036

.00277

.00017

−.00155

.00449

.01168

.00041

−.00221

.01307

.02201

.00080

−.00281

.02606

.03319

.00134

−.00340

.04333

.04479

.00280

−.00458

.06483

.05655

.00966

−.00795

.09031

.06828

.02422

−.01170

.11951

.07975

.04525

−.01480

.15212

.09077

.07229

−.017%

.18776

.10113

.10441

−.02131

22608

.11064

.14105

−.02479

26663

.11912

.18146

−.02831

30899

.12638

22509

−.03171

.35269

.13226

27122

−.03485

39728

.13659

.31929

−.03752

.44223

.13917

36859

−.03951

.48707

.13978

.41855

−.04054

53137

.13799

.46850

−.04013

.57522

.13349

51847

−.03767

.61871

.12640

56861

−.03326

.66185

.11707

.61888

−.02718

.70445

.10608

.66924

−.01993

.74609

.09394

.71934

−.01226

.78632

.08116

.76865

−00492

.82460

.06818

.81639

.00118

.86035

.05544

.86130

.00530

.89294

.04327

.90193

.00707

.92180

.03167

.93666

.00668

.94699

.02083

.96429

.00489

.96834

.01157

.98416

.00263

.98514

.00481

.99606

.00077

.99614

.00105

1.00000

.00000

1.00000

.00000.

8. The blade of claim 1 , further comprising:

a tip span region extending from a point that is approximately ninety percent of the distance radially outward from the horizontal axis to a point that is approximately one hundred percent of the distance radially outward from the horizontal axis; and

a tip airfoil positioned radially outboard from the primary airfoil in the tip span region, the tip airfoil having a thickness of at least about fifteen percent, a Reynolds number of at least about 2,500,000, and a maximum lift coefficient of about 1.4.

9. The blade of claim 8 , wherein the intermediate airfoil is positioned at a blade radial station of about 1.0.

10. The blade of claim 8 , wherein the intermediate airfoil further comprises: an upper surface and a lower surface, both of which extend spaced-apart in relation to each other from a leading edge to a trailing edge; and

a chord line with a length c extending in a straight line between the leading edge and the trailing edge, said upper surface and said lower surface having shapes and contours expressed by x/c values and y/c values, wherein the x/c values are dimensionless coordinates that represent locations on the length of the chord line and the y/c values are dimensionless coordinates that represent heights from the chord line to points on the upper surface and on the lower surface substantially as follows:

Upper Surface

Lower Surface

x/c

y/c

x/c

y/c

0.00000

0.00028

0.00010

−0.00126

.00011

.00150

.00026

−.00194

.00328

.00973

.00053

−.00252

.01071

.01942

.00094

−.00303

.02242

.03000

.00150

−.00353

.03830

.04102

.00188

−.00380

.05831

.05217

.00298

−.00448

.08228

.015320

.01074

−.00728

.11007

.07390

.02577

−.00958

.14137

.08415

.04734

−.01088

.17583

.C9376

.07510

−.01192

21310

.10256

.10825

−.01295

25274

.11037

.14628

−.01404

29436

.11701

.18846

−.01522

33747

.12233

23423

−.01649

38161

.12614

28287

−.01779

.42629

.12824

33377

−.01907

.47105

.12830

38622

−.02025

.51577

.12599

.43959

−.02122

.56040

.12129

.49317

−.02188

.60480

.11436

.54634

−.02208

.64882

.10544

.59843

−.02158

.69229

.09486

.64911

−.02005

.73496

.08312

.69821

−.01745

.77642

.07079

.74555

−.01394

.81614

.05839

.79090

−.00991

.85352

.04638

.83384

−.00585

.88788

.03517

.87378

−.00234

91858

.02488

.90980

.00013

.94539

.01576

.94089

.00144

.%785

.00839

96513

.00169

.98514

.00333

.98476

.00118

.99619

.00069

.99616

.00041

1.00000

.00000

1.00000

.00000.

11. A wind turbine that rotates about a horizontal axis, comprising:

a plurality of turbine blades mounted to a hub of the wind turbine for rotation about the horizontal axis and extending a distance radially outward from the horizontal axis to a tip;

an airfoil family defining cross-sections of each of the blades, the airfoil family comprising an inboard airfoil with a thickness of at least about 21 percent, a tip airfoil proximal to the tip of the blade with a thickness of at least about 15 percent, and an intermediate airfoil positioned between the inboard and tip airfoils with a thickness of at least about 18 percent;

wherein the turbine blades have a length measured from the horizontal axis to the tip of at least about 20 meters and wherein each of the blades further comprises:

a primary span region extending from a point that is approximately sixty-five percent of the distance radially outward from the horizontal axis to a point that is approximately eighty-five percent of the distance radially outward from the horizontal axis, wherein the inboard airfoil is positioned in the primary span region, the inboard airfoil having a Reynolds number of at least about 4,000,000 and a maximum lift coefficient of about 1.6;

an intermediate span region extending from a point that is approximately eighty percent of the distance radially outward from the horizontal axis to a point that is approximately one hundred percent of the distance radially outward from the horizontal axis, wherein the intermediate airfoil is positioned radially outboard from the inboard airfoil in the intermediate span region, the intermediate airfoil having a Reynolds number of at least about 3,500,000 and a maximum lift coefficient of about 1.5; and

a tip span region extending from a point that is approximately ninety percent of the distance radially outward from the horizontal axis to a point that is approximately one hundred percent of the distance radially outward from the horizontal axis, wherein the tip airfoil is positioned radially outboard from the intermediate airfoil in the tip span region, the tip airfoil having a Reynolds number of at least about 2,500,000 and a maximum lift coefficient of about 1.4.

Assignments (3)
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Sep 30, 2008
From: MIDWEST RESEARCH INSTITUTE
To: ALLIANCE FOR SUSTAINABLE ENERGY, LLC
Reel/Frame 021603/0337 →
CONFIRMATORY LICENSE Recorded May 9, 2008
From: MIDWEST RESEARCH INSTITUTE
To: ERNERGY, UNITED STATES DEPARTMENT OF
Reel/Frame 020929/0827 →
ASSIGNMENT OF ASSIGNOR'S INTEREST Recorded Nov 8, 2007
From: TANGLER, JAMES L., MR.
To: MIDWEST RESEARCH INSTITUTE
Reel/Frame 020087/0457 →