Hysteresis Effect in Operation of Small Wind Power Generators
Mathematical models of operating of horizontal-axis and vertical-axis wind turbines (HAWTs and VAWTs) are considered describing both aerodynamic load and electric generator. This model allows describing steady regimes and transient processes. Using the model, the hysteresis phenomenon is described arising during change of the external resistance in the electric circuit. It is shown that the preferable working regimes of the devices belong to the range of external load where the hysteresis effect appears.
A MODEL FOR UNSTEADY ROTOR AERODYNAMICS
Abstract An aerodynamic model for the simulation of unsteady flow past rotors of wind turbines is presented. The model consists of solving the unsteady, axisymmetric Euler or Navier-Stokes equations by a finite-difference method subject to volume forces determined from tabulated airfoil data. Results are compared to the blade-element momentum theory and experiments for the cases of a rotor with a prescribed constant normal load and steady as well as unsteady flows past the 2 MW Tjaereborg wind turbine. The model is found to be in better agreement with measurements than the momentum theory and in particular excellent agreement is obtained with dynamic in-flow phenomena from measured pitching transients.
Technical Note: Accuracy of Straight-Line Segmentation Applied to Curvilinear Vortex Filaments
Electrical drive apparatus for a vehicle comprising a detachable battery pack and a further unit comprising an electric motor, a differential with output shafts to respective vehicle wheels and a transmission from the motor to the differential including a universally jointed shaft, the axes of the motor differential output shafts and the shaft being substantially parallel and the motor being on the sprung and the differential being on the unsprung part of the vehicle.