Experimental investigation of the effects of tip-injection on the aerodynamic loads and wake characteristics of a model horizontal axis wind turbine rotor

Abdulrahim, Anas
In this study, tip injection is implemented on a model Horizontal Axis Wind Turbine (HAWT) rotor to investigate the power and thrust coefficient variations as well as the wake characteristics. The model wind turbine has a 0.95 m diameter 3-bladed rotor with non-linearly twisted and tapered blades that has NREL S826 profile. The nacelle, hub and the blades are specifically designed to allow pressurized air to pass through and get injected from the tips while the rotor is rotating. The experiments are performed at selected tip speed ratios by placing the turbine at the exit of a 1.7 m diameter open-jet wind tunnel facility. This thesis will present a comparative study of the power and thrust coefficient distributions with Tip Speed Ratio (TSR) for the baseline (no-injection) case as well as for the injection cases. In addition, wake measurements using Constant Temperature Anemometry (CTA) system have been conducted at different axial locations downstream of the rotor plane. Results show that, when there is injection, obtained characteristics have significant differences compared to the baseline case both for the load data showing an increase in power and thrust coefficients for TSR values starting near maximum CP condition up to higher TSR levels as well as for the wake characteristics showing a tip flow region that is radially pushed outwards with increased levels of turbulence occupying wider areas compared to the baseline case. Within the wake zone, it’s observed that the boundary between the wake and the freestream gets wider and more diffused due to tip injection. Finally, tip injection shows a power deficiency in terms of increasing the load data, since we are spending more power on the injected air than we gain. Therefore, it is best used for instantaneous active load control depending on flow conditions and load requirements.


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Citation Formats
A. Abdulrahim, “Experimental investigation of the effects of tip-injection on the aerodynamic loads and wake characteristics of a model horizontal axis wind turbine rotor,” M.S. - Master of Science, Middle East Technical University, 2014.