Wind Engineering
Module 4.2
WT_PERF Analysis
Lakshmi Sankar
lsankar@ae.gatech.edu
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.
Overview
•
In this module, we briefly review WT_PERF
– You may use other software for deliverables #2 (validating a wind turbine
performance code) and deliverable #3 (design your own wind turbine for the site
chosen in deliverable #1)
•
This software is publicly available from http://wind.nrel.gov/designcodes/
•
Contact Info:
–
–
–
–
–
–
•
•
•
Marshall L. Buhl, Jr.
NWTC/3811
National Renewable Energy Laboratory
1617 Cole Blvd.
Golden, CO 80401-3393
United States of America
Web: http://wind.nrel.gov/designcodes/
Email: marshall_buhl@nrel.gov
Voice: (303) 384-6914
WT_PERF
• Source code and Windows executables
are available.
• For this course, we only need the
executable.
• Download WT_PERF, unzip is into folders
• Print out the user guide.
• To run the code, in an MS DOS wind type
WT_Perf <input file> where input file has
extension wtp
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
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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, Header
• At the top of the input file.
• Describes the wind turbine you are
modeling.
• Example:
WT_Perf Test01 input file. UAE Phase 3 turbine
(Non-dimen, English, Space, PROP-PC).
Compatible with WT_Perf v3.00f
• This info is echoed in oup files.
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
False
False
Echo:
DimenInp:
Metric:
Echo input parameters to"<rootname>.ech"?
Turbine parameters are dimensional?
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.
Algorithm Flags
• We next specify which of the corrections
we are using (hub loss, tip loss, etc)
True
TipLoss:
False
HubLoss:
True
Swirl:
True
SkewWake:
True
AdvBrake:
True
IndProp:
induction algorithm?
False
AIDrag:
induction calculation?
False
TIDrag:
induction calculation?
Use the Prandtl tip-loss model?
Use the Prandtl hub-loss model?
Include Swirl effects?
Apply skewed-wake correction?
Use the advanced brake-state model?
Use PROP-PC instead of PROPX
Use the drag term in the axial
Use the drag term in the tangential
Turbine Data
•
We next specify turbine geometry. Only the
radius is dimensional (feet since we chose the
British system)
3
16.5
0.2
3.5
0.0
10.0
3.3333
16
NumBlade:
RotorRad:
HubRad:
PreCone:
Tilt:
Yaw:
HubHt:
NumSeg:
•
Pre-cone angle is the prebuilt coning angle of the blade relative to
the plane of rotation.
–
•
•
Number of blades.
Rotor radius [length].
Hub radius [length or div by radius].
Precone angle, positive downwind [deg].
Shaft tilt [deg].
Yaw error [deg].
Hub height [length or div by radius].
# of segments (entire rotor radius).
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.
Accounting for pre-Cone
Radius is R times cos(coning angle)
R
Coning Angle
Plane of
Rotation
Turbine Data (Continued)
• We next specify the rotor blade at a
number of radial locations.
RElm
0.225
0.275
0.325
0.375
0.425
0.475
0.525
0.575
0.625
0.675
0.725
0.775
0.825
0.875
0.925
0.975
Twist
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
0.000
Chord AFfile
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
0.0911
1
PrntElem
False
False
False
False
False
False
False
False
False
False
False
False
False
False
False
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
0.0001625
0.143
False
1
"airfoils/unsteadyaeroexp/s809_cln.dat"
Rho:
KinVisc:
ShearExp:
UseCm:
NumAF:
AF_File:
Air density [mass/volume].
Kinematic air viscosity
Wind shear exponent(1/7 law)
Cm data included in the airfoil tables?
Number of airfoil files.
List of NumAF airfoil files.
Other input
• We finally specify how we want our output,
the range of wind speeds, and range of
RPM values, and range of pitch angles to
examine.
• Some of the input flags are not shown
here..
3, 4, 1
pitch (deg).
72, 73, 1
speed (rpm).
15, 75, 1
PitSt, PitEnd, PitDel:
First, last, delta blade
OmgSt, OmgEnd, OmgDel:
First, last, delta rotor
SpdSt, SpdEnd, SpdDel:
First, last, delta speeds.
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.f90
Source/WT_Perf.f90
Source/WTP_Mods.f90
Source/WTP_Subs.f90