The Effect of Pylon Trailing Edge Blowing on the Performance and Noise Production of a Propeller

This paper discusses a study of the effects of pylon trailing edge blowing on pusher propeller performance and noise emissions. Experimental investigations were performed in a low speed open jet wind tunnel, using a powered propeller model and a generic pylon model. A novel pylon blowing system was integrated in the aft part of the pylon to provide a uniform outflow. The numerical analysis was executed using a combination of a propeller model that is based on an extended Blade Element Model (BEM) and a set of analytic methods from the literature, to assess the effects of pylon installation on the propeller performance and noise emissions. Measurements of the velocity distributions in the blown pylon wake showed that application of the blowing system reduced the integrated velocity deficit by up to 60% compared to the unblown configuration. Evaluations of the propeller forces and moments showed that the effects of installation on the time-averaged propeller performance are small, with differences of at most 2% for advance ratios below J=1.4. Furthermore, excellent agreement was obtained between the computed and measured performance for the isolated propeller. With respect to the propeller noise emissions it was observed that installation of the pylon upstream of the propeller strongly increases the noise levels. Depending on the propeller operating point, noise penalties of up to 15dB were measured. The application of pylon blowing clearly reduced the propeller noise emissions over the entire advance ratio range, with reductions of up to 7dB compared to the unblown case. The largest noise reductions were found at the highest blowing rate, indicating that the most effective blowing rate might not have been reached yet.