Parametric Study Of A Diffuser For Hawt Power Augmentation

The paper is a compilation of a work involving the study of the parametric relationship ofrngeometric parameters of a diffuser for power augmentation for horizontal axis wind turbinesrn(HAWTs). Various works of researchers are studied and hypotheses and possible optimizationrntechniques are put together to depict the picture of power augmentation. The bottom line showsrnthat the power output and performance of a wind turbine can be improved through the use ofrndiffusers. The effect of the use of these devices is to increase the mass flow rate at the rotorrnplane. This significantly augments the power developed by the wind turbine due to the cubicrnrelationship of wind speed and power. This increase in speed, represented by the accelerationrnfactor or velocity ratio, rn��rn��∞rn, is dependent on the geometry of the concentrator device,rnspecifically the diffuser. The basic diffuser geometry parameters were identified and theirrnrelationships were formulated based on CFD results. A commercial software, ANSYS-Fluent,rnis used for simulation where the results are analyzed with MS-Excel and Matlab. The resultsrnshow good agreement with previous works. rnDue to the presence of a diffuser in the flow field, the velocity ratio along the central axis ofrnthe diffuser shows an increase as the flow approaches the diffuser inlet. The velocity peaks atrna location immediately after the diffuser inlet. The velocity, then, levels off and furtherrndecreases as the flow continues to the diffuser outlet and exits it. This suggests a possiblernlocation of a wind turbine at the vicinity of the inlet. rnThe length of the diffuser and the flange height were the major parameters considered in thisrnstudy. Their relationship with velocity ratio was analyzed and the results show that both haverna direct relationship with the velocity ratio. The no-flange configuration showed a 32.5%rnincrease in the on-axis wind speed in reference to the bare wind turbine configuration. Thernflanged configurations showed a 45% and 51% increase on the on-axis wind speed with rn=rn0.1 ������ 0.2, respectively. The maximum power augmentation ranges from two-to-three timesrnthe power produced by a comparable bare wind turbine. The mathematical relations obtainedrnfor the major parameters and the velocity ratio can be used in the performance prediction andrnoptimization of a diffuser. Finally, possible directions of further research and work arernrecommended

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