Tomas Sinnige

Aerodynamic and Aeroacoustic Effects of Pylon Trailing Edge Blowing on Pusher Propeller Installation

The aerodynamic and aeroacoustic effects of pylon trailing edge blowing on the propulsive performance and noise emissions of a propeller installed in a pusher configuration were studied in a wind tunnel. A propeller model and a pylon equipped with a trailing edge blowing system were installed in the large low-speed facility of the German-Dutch wind-tunnels (DNW-LLF). Particle image velocimetry measurements of the flow field downstream of the pylon confirmed a wake re-energization obtained through blowing, with a momentum deficit recovery of 80% compared to the unblown case. For the symmetric inflow conditions considered, the effect of pylon installation on the propulsive performance was found small. Increases in thrust and torque of 1% up to 6% were measured at high and low thrust settings, which was comparable to the measurement variability. Acoustic data obtained using out-of-flow microphones confirmed the strong interaction effects resulting from the installation of the upstream pylon, with an increase in noise levels due to the presence of the pylon of up to 12 dB at a medium propeller thrust setting. The application of pylon trailing edge blowing successfully eliminated the installation effects, resulting in noise levels equal to those of the isolated propeller over the entire axial directivity range. At higher thrust settings the change in blade angle of attack due to the pylon wake impingement is smaller, and the steady blade loads are larger compared to the unsteady loads experienced during the wake passage. Consequently, in this operating regime the propeller noise emissions were dominated by steady sources for all but the most upstream observer positions.

The Effects of Swirl Recovery Vanes on Single-Rotation Propeller Aerodynamics and Aeroacoustics

A preliminary assessment of the aerodynamic and aeroacoustic impact of swirl recovery vanes (SRVs) installed downstream of a single-rotating propeller model was performed at the large low-speed facility of the German-Dutch wind tunnels (DNW-LLF). The SRVs are designed to recover the swirl in the rotor slipstream, thereby increasing the propulsive efficiency without the added complexity of contra-rotating systems. The performance data acquired with a rotating shaft balance showed that the upstream effect of the SRVs on the time-averaged rotor performance was negligible. Particle image velocimetry measurements in the slipstream of the propeller with and without SRVs substantiated the efficacy of the vanes in reducing the swirl in the propeller slipstream. Integrated in the radial direction, installation of the vanes reduced the swirl kinetic energy by 50% at a medium propeller thrust setting. An additional slipstream contraction was observed with vanes installed. The acoustic data measured with out-of-flow microphones showed that installation of the SRVs increased the total sound pressure levels by 2 to 6 dB compared to the isolated propeller.

Aerodynamic interaction effects of tip-mounted propellers installed on the horizontal tailplane

This paper addresses the effects of propeller installation on the aerodynamic performance of a tailplane featuring tip-mounted propellers. A model of a low aspect ratio tailplane equipped with an elevator and a tip-mounted propeller was installed in a low-speed wind-tunnel. Measurements were taken with an external balance and surface pressure taps to determine the aerodynamic characteristics of the tailplane, while the flowfield in the wake of the model was investigated using particle-image velocimetry. The experimental data are supported by CFD analyses, involving both transient simulations of the full-blade configuration and steady-state simulations the propeller replaced by an actuator-disk model. The upstream effects on the propeller time-average and time-accurate thrust and normal-forces are found to be limited for different tailplane operating conditions. It is shown that for a given propeller rotation direction, the load distribution on the tailplane is highly dependent on the direction of elevator deflection. The rotation direction of the tailplane tip-vortex relative to the propeller swirl therefore significantly affects the integral loads on the tailplane, resulting in differences in the normal-force gradient and elevator effectiveness.

Tractor Propeller-Pylon Interaction, Part II: Mitigation of Unsteady Pylon Loading by Application of Leading-Edge Porosity

Citation (APA) Della Corte, B., Sinnige, T., de Vries, R., Avallone, F., Ragni, D., Eitelberg, G., & Veldhuis, L. (2017). Tractor Propeller-Pylon Interaction, Part II: Mitigation of Unsteady Pylon Loading by Application of LeadingEdge Porosity. In 55th AIAA Aerospace Sciences Meeting: Grapevine, Texas [AIAA 2017-1176] American Institute of Aeronautics and Astronautics Inc. (AIAA). https://doi.org/10.2514/6.2017-1176

Pusher-Propeller Installation Effects in Angular Inflow

Pylon-mounted pusher propellers suffer from installation effects due to the interaction between the pylon and the propeller. The impact of angular inflow on these installation effects was quantified at the Large Low-Speed Facility of the German-Dutch wind tunnels (DNW-LLF). Particle-image-velocimetry measurements showed that the pylon wakes width and velocity deficit were hardly affected by the introduction of a six-degree sideslip angle. Application of pylon trailing-edge blowing reduced the integral velocity deficit in the wake by up to 65%. Evaluations of the surface pressures on the blades confirmed the sinusoidal loading behavior in angular inflow and the impulsive loading peak due to the pylon-wake encounter. The circumferential velocity components induced by the pylon tip vortex strongly affected the steady-state propeller performance by modifying the effective advance ratio sensed by the blades. Increased performance was measured when the rotation direction of the pylon tip vortex was opposite to that of the propeller. Angular inflow affected the propeller noise emissions due to the resulting unsteady blade loads and the circumferential variation of the effective Mach number of the blade sections. The installation of the pylon added a noise source due to the unsteady blade loads caused by the pylon-wake encounter. Depending on the sideslip angle, application of blowing eliminated a large part of the installation noise penalty, despite remaining non-uniformities in the blown wake profiles.

Unsteady Pylon Loading Caused by Propeller-Slipstream Impingement for Tip-Mounted Propellers

An experimental analysis was performed of the unsteady aerodynamic loading caused by the impingement of a propeller slipstream on a downstream lifting surface. When installed on an aircraft, this unsteady loading results in vibrations that are transmitted to the fuselage and are perceived inside the cabin as structure-borne noise. A pylon-mounted tractor–propeller configuration was installed in a low-speed wind tunnel at Delft University of Technology. Surface-microphone and particle-image-velocimetry measurements were taken to quantify the pressure fluctuations on the pylon and visualize the impingement phenomena. It was confirmed that the propeller tip vortex is the dominant source of pressure fluctuations on the pylon. Along the path of the tip vortex on the pylon, a periodic pressure response occurs with strong harmonics. The amplitude of the pressure fluctuations increases with increasing thrust setting, whereas the unsteady lift coefficient displays a nonmonotonic dependency on the propeller thrust....

Pusher-Propeller Blade Loading With and Without Pylon Trailing-Edge Blowing

The aerodynamic interaction e_ects characteristic of pusher propellers were studied at the Large Low-Speed Facility of the German{Dutch wind tunnels (DNW-LLF). A propeller model was positioned downstream of a pylon equipped with a trailing-edge blowing system. Surface-pressure transducers integrated into the propeller blades con_rmed the local impact of the pylon wake on the blade loads. At an intermediate thrust setting, the sectional lift impulsively increased by 30% during the wake passage. The application of pylon blowing decreased the integral velocity de_cit in the pylon wake by up to 77% compared to the unblown case. As a result, the load uctuations during the wake encounter were practically eliminated, thereby mitigating the adverse installation e_ects.