Assessment of Front Rotor Trailing Edge Blowing for the Reduction of Open Rotor Interaction Noise

Abstract

Contra-Rotating Open Rotor (CROR) propulsion systems show promise as a highly economic and environmentally friendly powerplant for future transport aircraft. One major challenge to overcome relates to the noise emissions of this type of engine, which is driven in large part by the complex mutual interactions between the two rotors of the CROR. In the present study, a coupled aerodynamic and aeroacoustic analysis using the DLR numerical methods TAU and APSIM+ is performed to assess the potential of front rotor trailing edge blowing (TEB) to achieve a reduction of interaction tone noise emissions of CROR propulsion systems. A successful alleviation of the front rotor’s blade wakes could be achieved, which led to a clear reduction in local aft blade unsteady loadings for much of their spanwise extent. However, the specific CROR configuration under study here still has significant impingement of the front blade’s tip vortices on the aft rotor due to an insufficient reduction of the aft rotor diameter with respect to that of the front rotor. In terms of overall aerodynamic performance, no notable difference is found between the two configurations under study. On the aeroacoustics side, interaction tones are most affected showing the expected decrease in sound pressure level near the rotor planes. Upstream of the rotors, increased levels are seen resulting from the aforementioned tip-vortex impingement on the aft rotor blades.