WTPREP Manual
Airfoil Data Preparation Software for Horizontal Axis Wind Turbines

UIUC Applied Aerodynamics Group
Department of Aeronautical and Astronautical Engineering
University of Illinois at Urbana-Champaign, Urbana, Illinois 61801

Michael S. Selig
with contributions by Nikhil Raj


Last update 7/05/98

Contents

  1. Overview (6/24/98)
  2. Generic Turbines (6/24/98)
  3. Input file lines (6/24/98)
  4. Sample Input Files and Output (6/24/98)
  5. Results (6/30/98)
  6. Airfoil Data (6/30/98)

1. Overview

WTPREP is a preprocessor code, and is used in the preparation of blade airfoil data for use in PROPID, PROP93 and other wind turbine design programs. WTPREP was originally written to have the data preprocessing features but no design and analysis capabilities. The features of WTPREP were recently integrated into PROPID, the wind turbine design and analysis program written by Dr. Michael Selig, heading the Applied Aerodynamics Group at the University of Illinois. This document is a standalone manual for use of WTPREP features in PROPID. It contains a set of additional instructions to the PROPID code which correspond to the features of WTPREP. This includes the generation 3D data using the UIUC model, the expansion of this data from -180 to +180 deg and the generation of input files for the PROP93 and AERODYN programs. The complete description of PROPID and its features are given the PROPID Manual. A preprocessor code has now been coupled with a design code, which becomes a powerful tool for the aerodynamic design and analysis of wind turbines.

2. Generic Turbines

Two generic turbines have been discussed here. Turbine A is similar to the NREL Combined Experiment Rotor, Phase III machine. Turbine B is similar to the NREL AWT-26 machine. The parameters of the machines anaylzed are:

Description of Turbine A
Number of Blades 3
Rotor Diameter 10.06m
Rated Power 20kW
Description of Turbine B
Number of Blades 3
Rotor Diameter 10.06m
Rated Power 20kW

2. Input File Lines

These are the lines to be added to the general PROPID input file to make use of the WTPREP features.

DU_MODEL 1.0 1.0 1.0 22.5

The constants for the UIUC model. The first three are the empirical constants used in the model. Has been found that a value of 1.0 for all these constants give good predictions.

The fourth constant is the fixed wind speed used to generate the data for the PROP93 code. This is in mph.

MakePROPAirfoilData

This line is used to generate the airfoil data for use in the PROP93 code. It is one of the many ways to obtain airfoil data from WTPREP. The wind speed is fixed here, and data is generated for several different angles. This approach is referred to as the "fixed-wind mode" of generating airfoil data. This is used with the AlfaMinMaxInc line. Data can now be generated from -180 to +180 deg for one wind speed. This has been plotted in Figure 1 shown here.

Figure 1. Cl at 25% span for Generic Turbine A
OUTPROP
filename
Used to generate the input file for the PROP93 code. filename is the name desired for the input file.

OUTAERODYN
filename
Used to generate the input file for the AERODYN code. filename is the name desired for the input file. This feature is still to be implemented.

OUTGRAPH
filename
Used to generate the input file for the WTPLOT plotting code. filename is the name desired for the input file.

Figure 2. Cl data for Turbine A
This is the Cl curve at the 30% span location along the blade for the variable wind mode. The difference between the 2D data and the 3D data can be seen clearly. The 3D effects are huge near the root. Stall is greatly delayed. The UIUC model captures this effect.

PROPFileNames
10 ! This is the number of segments, iseg
filename 1
title of file 1
.
.
.
filename for the n'th segment(iseg)
title for that file

If the data generated from the 2D_SWEEP line is desired, then the PROPFileNames line is used to read in the names of the files, one for each segment. This is the variable wind mode of data generation from the code. Here, there is a wind speed sweep, which generates different angles of attack. These angles are then used in the interpolation subroutines to generate the data. The data generated is written out to the files whose names are read in at this line. There has to be the same number of files as there are segments. It must be noted that these files are written in the append mode and if the same file name is used for several different runs of the program, the file will be continously appended. Another point to be noted here is that both the 2D_SWEEP and 1D_SWEEP data is added to the files. Data generated in the variable wind mode is shown in the adjoining figure.

3. Sample Input Files

In this section, the input files for the two generic turbines are described.
Annotated Input file for Turbine A
Download the Turbine A input file
Turbine A: Output

Annotated Input file for Turbine B
Download the Turbine B input file
Turbine B: Output

These input files are examples of the WTPREP features in PROPID. The use of all the special lines explained in Section 2 is illustrated in these files. A small explanation on every line in the input file is available by clicking on the line itself, or is provided in the input file, if its obvious. To return to the input file, the user is advised to use the BACK button on the browser. For details regarding most of the lines in the input files, it is necessary that the user looks into the PROPID User's Manual and the Updates to PROPID User's Manual.

The above input files can also be downloaded and can be used to run the program. The output obtained can be compared with the outputs that have been already obtained to see if the program has been installed correctly and is running as expected.

4. Results

The results obtained by using WTPREP with the above turbines A and B input files are shown here. Comparison of the results of turbine A with the experimental data for the NREL CER III is made because the modeling of turbine A is close to that of the CER III. Similarly the results of turbine B are compared with those of the NREL AWT26. The data generated by the PROPFileNames line is used to generate the graphs in the variable wind mode. The data from the AirfoilFileNames line is used to generate data in the fixed wind mode.

Cl curves are compared with experimental results. The curves are shown for both the variable wind mode and the fixed wind mode. The power curves are also shown. The experimental data match with the predictions for the lift coefficient. The power curve for the AWT26 shows a good match between experimental data and predictions. But the power curve predictions need to be looked into. This does not reflect the accuracy of the model itself at this stage. But it is certainly true that there are improvements needed for the model.

Results for Generic Turbine A
  • Cl, Cd in fixed wind mode
  • Cl in variable wind mode
  • Power Curve
    		•  Results for Generic Turbine B
  • Cl in fixed wind mode
  • Cl in variable wind mode
  • Power Curve
    		•

    4. Airfoil Data

    The 2D airfoil data to be used in the program for analysis of the various wind turbines is required to be in a certain format. The data can be viewed or downloaded here.

    View the airfoil data.

    [Top] [UIUC Applied Aerodynamics Group]