WIND TURBINE DESIGN BASIS AIMS AT CREATING A PERSONAL COMPUTER SOFTWARE PACKAGE, CAPABLE OF PERFORMING A WIDE RANGE OF WIND TURBINE DESIGN CALCULATIONS. THE INPUT-OUTPUT STRUCTURE OF THE END PRODUCT SHALL HAVE A FORM THAT ALLOWS PROFESSIONAL ENGINEERS, WITH NO SPECIFIC TURBINE ENGINEERING BACKGROUND, TO USE THE PACKAGE WITH ONLY LITTLE INTRODUCTION.
A number of models together constitute the theoretical basis for the design basis program. The program facilitates the evaluation of the load carrying capacity of a horizontal axis wind turbine (HAWT) operating at constant angular velocity and with a relatively stiff tower. The load carrying capacity is ultimately expressed in terms of extreme values and fatigue lifetime. Moreover, deflections, velocities, accelerations, sectional forces and stresses can be presented for an arbitrary load case. These results are given in terms of a complex amplitude spectrum describing the deterministic part, and a power spectrum describing the stochastic part. The program provides a user friendly environment based on menu driven editing and control facilities. Moreover, graphics are used extensively for the presentation of results. The design basis program has been developed for use on a personal computer, and much effort has been used to assure that a minimum of computer memory is employed. Further development of the theory and the program is planned for the future.
DESIGN BASIS DRAWS VERY LARGELY ON EXISTING THEORY FOR ITS TECHNICAL CONTENT. EVEN SO, A CERTAIN AMOUNT OF MODIFICATION IS IN MANY CASES NECESSARY, TO TAKE ACCOUNT OF THE LIMITED RESOURCES AND SPEED OF A MICROCOMPUTER. THE FOLLOWING AREAS HAVE BEEN CODED :
* BLADE AERODYNAMIC LOADS
* BLADE NATURAL FREQUENCIES AND MODE SHAPES
* CROSS SECTION PROPERTIES FOR COMPLEX STRUCTURES
* TRANSFORMATION OF WIND POWER SPECTRUM TO THE ROTATING FRAME
SINCE THE SUCCESS OF DESIGN BASIS DEPENDS VERY LARGELY ON THE PROGRAMME'S USER INTERFACE, MUCH EFFORT HAS BEEN CONCENTRATED ON SOFTWARE ASPECTS. THESE INCLUDE :
* ANALYSIS OF TRENDS ANS AVAILABILITY OF SOFTWARE AND HARDWARE
* DEVELOPMENT OF "USER-FRIENDLY" MENUS AND DATA EDITORS
* INPUT DATA VERIFICATION
* "HELP" WINDOW SYSTEM
* DE-BUGGING TECHNIQUES
IN ITS PRESENT FORM, THE DESIGN BASIS PROGRAMME CAN CALCULATE AND DISPLAY AERODYNAMIC LOADS ON VARIOUS PARTS OF THE TURBINE. TYPICAL SERVICE CONDITIONS INCLUDING YAW ERROR, FLOW INCLINATION, TOWER SHADOWING AND WIND SHEAR, MAY BE TREATED. DATA INPUT IS FULLY INTERACTIVE.
WORK IN PROGRESS WILL SHORTLY EXPAND THE PROGRAMME'S CAPABILITIES TO INCLUDE DYNAMIC LOAD DETERMINATION. OF PARTICULAR IMPORTANCE HERE IS THE ESTIMATION OF BOTH FATIGUE DAMAGE AND EXTREME LOADS. IN ITS INITIAL FORM ONLY THE DYNAMICS OF A SINGLE BLADE WILL BE MODELLED. FOR MANY CONTEMPORARY WIND TURBINES, THIS IS SUFFICIENT TO GIVE A CLOSE APPROXIMATION TO THE ACTUAL BLADE LOADS.