WT PERF Analysis - Wind Engineering - Lecture Slides, Slides of Environmental Law and Policy

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Wind Engineering

Module 4.

WT_PERF Analysis

Recap

• In Module 1, we reviewed course

objectives, history of wind turbines, and

some terminology

• In Module 2, we developed an actuator

disk model of the wind turbine.

• In Module 3, we reviewed airfoil

aerodynamics, analysis and design tools.

• In Module 4.1, we reviewed blade element

theory.

Sample Input Files

• WT_PERF comes with several sample input

files.

• Start with one of these, and modify for your own

needs.

• These are in a folder named CertTest

– CertTest/Test01_UAE.wtp

– CertTest/Test02_AWT27.wtp

– CertTest/Test03_CART3.wtp

– CertTest/Test04_WP15.wtp

– CertTest/Test05_WL8.wtp

Common Extensions

• All output files use the same root name as the input file.

• They will have different extensions.

• The extensions are as follows:

– bed – the blade-element data

– ech – the echo of the input data

– oup – the primary output file

• Run the code for a supplied input file, and compare your

output files against the supplied output files.

• The data is in ASCII format and may be plotted using

Excel, Tecplot, or your favorite plotting tools.

Sample Input File, Input

Configuration

• The next few lines specify whether you

want the input to be written out to the .ech

output file, whether your input is

dimensional, and which system of units you

are using.

• False Echo: Echo input parameters to".ech"?
• False DimenInp: Turbine parameters are dimensional?
• False Metric:

Model Configuration

• If there is a yaw angle, or if the turbine is

large, wind velocity and total velocity may

vary radially and azimuthally.

• You also specify how many iterations are

needed for computing a, a’

16 NumSect: Number of circumferential sectors.

5000 MaxIter: Max number of iterations for

induction factor.

1.0e-6 ATol: Error tolerance for induction

iteration.

1.0e-6 SWTol: Error tolerance for skewed-wake

iteration.

Turbine Data

• We next specify turbine geometry. Only the

radius is dimensional (feet since we chose the

British system)

3 NumBlade: Number of blades. 16.5 RotorRad: Rotor radius [length]. 0.2 HubRad: Hub radius [length or div by radius]. 3.5 PreCone: Precone angle, positive downwind [deg]. 0.0 Tilt: Shaft tilt [deg]. 10.0 Yaw: Yaw error [deg]. 3.3333 HubHt: Hub height [length or div by radius]. 16 NumSeg: # of segments (entire rotor radius).

• Pre-cone angle is the prebuilt coning angle of the blade relative to

the plane of rotation.

• Instead of being flat in the plane of rotation, the blade cones upwards or downwards

• Manufacturers sometimes build this into the rotor to reduce

stresses at the root due to bending moments.

• In the performance code, the coning reduces the rotor disk radius

from R to R times cosine of the coning angle, 16.5 cos(3.5 deg)

feet in the above example.

Precone Angle http://www.cavalrypilot.com/fm1-514/Ch2.htm

• The upward flexing of a rotor blade due to lift forces acting on it is called coning.
• Coning is the result of lift and centrifugal force acting on a blade in flight.
• The lift force is almost 7 percent as great as the centrifugal force, which causes the blade to deflect upward about 3° to 4°.
• The preconed hub lets the blades operate at normal coning angles without bending, which reduces stress.

Turbine Data (Continued)

• We next specify the rotor blade at a

number of radial locations.

RElm Twist Chord AFfile PrntElem 0.225 0.000 0.0911 1 False 0.275 0.000 0.0911 1 False 0.325 0.000 0.0911 1 False 0.375 0.000 0.0911 1 False 0.425 0.000 0.0911 1 False 0.475 0.000 0.0911 1 False 0.525 0.000 0.0911 1 False 0.575 0.000 0.0911 1 False 0.625 0.000 0.0911 1 False 0.675 0.000 0.0911 1 False 0.725 0.000 0.0911 1 False 0.775 0.000 0.0911 1 False 0.825 0.000 0.0911 1 False 0.875 0.000 0.0911 1 False 0.925 0.000 0.0911 1 False 0.975 0.000 0.0911 1 False Radial location, twist on degrees, chord non-dimensionalized By tip radius, airfoil family, and whether we want details About the element printed or not.

Aerodynamic Data

• We next supply density, kinematic viscosity,

and the coefficient which determines if wind

speed varies with height across the rotor

diameter.

• We also give the name of the airfoil file(s).

0.0019749 Rho: Air density [mass/volume]. 0.0001625 KinVisc: Kinematic air viscosity 0.143 ShearExp: Wind shear exponent(1/7 law) False UseCm: Cm data included in the airfoil tables? 1 NumAF: Number of airfoil files. "airfoils/unsteadyaeroexp/s809_cln.dat" AF_File: List of NumAF airfoil files.

Output Files

• The output files contain valuable and useful results.
• These include power, power coefficient, torque, thrust, thrust coefficient, root bending moment, sectional loads, etc.
• Sample output files are found at: CertTest/TestFiles/Test01_UAE.bed CertTest/TestFiles/Test01_UAE.oup CertTest/TestFiles/Test02_AWT27.bed CertTest/TestFiles/Test02_AWT27.oup CertTest/TestFiles/Test03_CART3.bed CertTest/TestFiles/Test03_CART3.oup CertTest/TestFiles/Test04_WP15.bed CertTest/TestFiles/Test04_WP15.oup CertTest/TestFiles/Test05_WL8.bed CertTest/TestFiles/Test05_WL8.oup

Source Code

• The source code of the most recent

version is written in Fortran 90.

• Please look at the following files if you are

curious about how these programs are

written.

Source/SetProg.f

Source/WT_Perf.f

Source/WTP_Mods.f

Source/WTP_Subs.f