Experimental investigation into the effects of blade number on wind turbine rotor aeroacoustics and performance

Wind turbines have established their place in the energy market and are gaining increasing support for implementation. Having only become economically feasible within the past ten years they are devices that lack complete understanding and require further investigation. Opposition to this form of renewable energy has come, and is supported by the aerodynamic noise generation and radiation from the turbine blades steady and unsteady loading. The individual sources are well identified that comprise this noise, but insight is needed into their control on a system level. The Wind Turbine Rotor Research Facility was designed and instrumented in response to the incomplete research in the field. Necessary facility capabilities were determined and provided to control and measure the wind speed, to select the turbine rotational speed independent of all other parameters, to understand the power performance by measuring the rotor torque, and finally to determine the relationship between these variables and the measured acoustic footprint of the rotor. Satisfaction of the facility requirements was verified through experiments with a two- and a three-blade rotor and subsequent comparison to expected and manufacturer results for the baseline wind turbine utilized. The suitability of this facility for experimental studies of wind turbine was verified through inlet radial velocity profile measurements which show the boundary layer beyond the tip radius of the rotor. Rotor torque measurements yield expected curves for a wind turbine with values very near to that of the manufactured baseline wind turbine. Comparison amongst power performance curves for the two- and three-blade rotor further confirms expected results and the facility operation. Acoustic measurements taken to quantify the wind turbine noise generation for various turbine rotational speeds provided insight into the turbine noise sources, demonstrating the ability of this facility to effectively study noise sources and isolate and identify the controlling flow and turbine parameters