Steady Calculations Introduction
This series of calculations simplify the analysis of the turbine by computing the loading and performance of the turbine for a combination of steady environmental conditions and operating points. The operating point for a calculation will either be specified exactly by user input or determined through turbine operational parameters. The operating point fixes the rotor speed and pitch angle for the analysis. The wind speed used will be specified by the user. The structural states of the system are then solved based on the resulting applied loads. This will determine the blade or tower deflection if flexibility is included in the analysis. The output of the analysis varies according to the selected calculation type and more details can be found in the corresponding section for each calculation. These calculations are most useful at the preliminary design stage or for verification against other aeroelastic simulation tools.
Aerodynamic Information: This computes the aerodynamic performance of the blade including flow induction, lift coefficient and local aerodynamic loading at each blade station. The analysis is computed for one operating point and one wind speed and the user must specify the uniform wind speed, rotor speed and pitch angle to analyse.
Performance Coefficients: Power, torque and thrust coefficients are calculated for a range of user specified tip speed ratios and a fixed rotor speed.
Steady Power Curve: This gives power, torque and thrust as a function of wind speed, assuming a uniform steady wind field.
Steady Operational Loads: The turbine structure is analysed at a range of wind speeds to compute how variables such as electrical power, pitch angle, rotor speed, hub and blade root loads vary with respect to wind speed. At each wind speed the rotor speed and pitch angle operating point are determined using the turbine control strategy.
Steady Parked Loads: Loads on the parked turbine are calculated in steady wind. As the blade position is specified, the wind field need not be spatially uniform.
Model Linearisation: Small perturbations are used to generate system responses, from which the dynamics of the fully non-linear coupled system can be linearised and then analysed. A Campbell diagram can be generated, showing how the system frequencies change with rotational speed. Or (with the advanced control) the linear model post-processing calculation can be used to derive a linearised model of the turbine in state-space form. This is of particular value for designing controllers. Finally, blade stability analysis can be performed to assess the aerodynamic stability of flexible rotor blades.
Last updated 23-08-2024