Z08: low-speed aero-acoustic experimental characterization of open rotor installation on aircraft

22nd AIAA/CEAS Aeroacoustics Conference

et al. 2016

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 wake's 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.

Section: -9mentioning

confidence: 52%

Pusher-Propeller Installation Effects in Angular Inflow

22nd AIAA/CEAS Aeroacoustics Conference

et al. 2016

“…Numerical simulations performed by Stürmer and Yin [9] have shown that pylon trailing-edge blowing can successfully decrease the unsteady blade loading, resulting in a reduction of the installation noise penalty. The beneficial effects of pylon blowing on far-field propeller noise levels have also been confirmed by experiments [6][7][8]10]. …”

Section: Introductionmentioning

confidence: 50%

Mitigation of Pusher-Propeller Installation Effects by Pylon Trailing-Edge Blowing

et al. 2017

Journal of Aircraft

This paper presents an experimental assessment of the working principles of pylon trailing-edge blowing for the mitigation of the interaction between a pusher propeller and its associated pylon. The experiments were performed at the Large Low-Speed Facility of the German-Dutch wind tunnels (DNW-LLF), using a powered propeller model and an upstream pylon equipped with a trailing-edge blowing system. In-flow microphone measurements demonstrated the impact of pylon installation on the propeller's tonal noise emissions, with increases of up to 16 dB relative to the isolated propeller. Analysis of the unsteady blade pressures showed that this installation effect is caused by the impulsive increase in blade loading during the pylon-wake passage.The efficacy of pylon trailing-edge blowing to reduce the momentum deficit in the pylon wake was confirmed by stereoscopic particle-image-velocimetry measurements between the pylon and the propeller. Consequently, application of the pylon-blowing system alleviated the pylon-installation effects at the source. At an intermediate thrust setting, the root-mean-square of the blade-load fluctuations due to the wake encounter was reduced by up to 60%, resulting in noise emissions approximately equal to those recorded for the isolated propeller.a Ph

“…4 The adverse pylon-installation effects can be mitigated by eliminating the momentum deficit in the pylon wake. This can be achieved using pylon blowing, as confirmed previously by experimental research with single-rotating [5][6][7] and contra-rotating [8][9][10][11] propellers, as well as numerical investigations 12 . The experimental studies published so far focused on the beneficial effects of pylon blowing on the far-field noise levels.…”

Section: Introductionmentioning

confidence: 52%

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

34th AIAA Applied Aerodynamics Conference

et al. 2016

The aerodynamic interaction effects 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 confirmed 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 deficit in the pylon wake by up to 77% compared to the unblown case. As a result, the load fluctuations during the wake encounter were practically eliminated, thereby mitigating the adverse installation effects.