One of the operational problems encountered with vertical axis wind turbines is their low starting torque. A number of analytical methods were investigated to see whether they could predict the starting performance of vertical axis turbines. The chosen methods used " actuator disc theory" for both single and multiple streamtubes. Two different forms of the multiple streamtube model are applied, one using a single actuator disc and the other using two discs in tandem. The computational analysis of all models simulates the blade aerodynamics throughout the full range of incidence from -180° to 180°. The effects of varying various geometric parameters of the windmill upon the performance of the rotor are investigated to find a design with improved self starting characteristics. The best agreement between theory and experiment was obtained using the multiple streamtube (double disc) method. Savonius rotors have been commonly employed as " starters "for Darrieus turbines. A new analytical method has been developed to model the performance characteristics of the Savonius rotor. In this method the blade is divided up into small elements, and each element is treated as a thin airfoil. The rotor torque and power are computed taking into account the blades' motion, the blade shape and momentum consideration. This method shows good agreement with experimental results for a variety of Savonius rotors.A new experimental technique has been developed to provide information about the variation of torque within a cycle. These results have been used as a check on all the theoretical methods. The agreement between these experimental results and the theoretical methods show that they predict both the time averaged and the instantaneous performance.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:629477 |
| Date | January 1995 |
| Creators | Elmabrok, Ali Mohammed |
| Publisher | University of Manchester |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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