الفهرس 
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Abstract
The Diffuser Augment Wind Turbine (DAWT) is one of the advanced concepts being developed to improve the attractiveness of the wind energy as An energy resource alternative. It is aimed to increase the concentration of naturally diffuse wind energy and reduce the specific cost of available power by minimizing the capital cost of energy conversion machinery.
Diffuser controls the expansion of turbine flow, producing a highly sub-atmospheric pressure at the turbine exit. The low static pressure induces greater mass flow through the turbine in contrast to a conventional wind turbine in (CWT) design of the same diameter. Thus, the output power of DAWT is much larger than for a bare turbine. This research work describes a multiphase investigation, involving two phases of testing the DAWT.
The first phase is for testing a model of conventional wind turbine to determine the most proper rotor geometry. A three blades horizontal axis wind turbine has been constructed in such a way to change the geometric pitch angle and to replace the twisted blades fastened in the conical hub .Three twisted blade groups having a twisted angles of 100,200 and 300 have been tested at three different pitch angles, 100,200and 300. A theoretical model was constructed to evaluate the performance of the tested models. The experimental results showed a maximum power coefficient of 28%0at a tip speed ratio of 1.6 for the 200 geometric pitch angle and blade group having 100 twist angle .
The second phase is the testing of wind turbine rotor shrouded with a diffuser. A short cylindrical part of 5cm.length was made at the entrance of the diffuser to make uniform inlet flow of air. The wind turbine model is installed at the entrance of the diffuser. Four groups of diffuser were tested as a shroud for the rotor. Each group n of four different vertex angle diffusers 150,300, 450 and 600 but having the same area ratio equal 3. The first group is without slot and the other three groups with slot to control boundary layer flow. The slot widths made are 3mm, 5mm, and 8mm which correspond to slot area relative to diffuser inlet area of 2.5,5 and 7% respectively.
The experimental results showed that the first group of diffusers have a low pressure recovery factor and its maximum value is in the case of 150 vertex angle diffuser equal 75%. The maximum augmentation ratio of the DAWT in case of using diffusers without slot is 0.99, (relative to Betz`s limit) and 2.27 (relative to the tested CWT model). The diffuser pressure recovery coefficient increases in case of using slot for boundary layer control and so the augmentation ratio of the DAWT increases. The maximum value of the pressure recovery coefficient is 90.5% and the corresponds to 3.54 relative to the selectes CWT.
at a tip speed ratio of 1.6 for the 20