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

Abstract

A possible way to decrease the noise contribution of the interaction tones of a contrarotating open rotor (CROR) is through application of trailing edge blowing (TEB), by reducing the momentum deficit of the front rotor wake and therefore its interaction with the aft rotor. In this contribution, we present a novel assessment of front rotor TEB for the reduction of CROR noise. For this purpose, the Airbus Clean Sky generic Open Rotor configuration AI-PX7 configuration has been modified to include TEB at the front rotor blades. With the DLR CFD-code TAU, uRANS simulations have been made of the baseline and the TEB configuration. Subsequently, an aeroacoustic analysis has been performed with the Ffowcs-Williams/Hawkings tool APSIM+ for both configurations. The results show a negligible degradation of the aerodynamic performance, with slightly higher unsteady loading of the aft rotor. This is resulting from the front rotor tip vortices which impinge on the aft rotor due to insufficient aft rotor cropping. On the aeroacoustics side, interaction tones are most affected showing a slight decrease in maximum overall sound pressure level. Rotor-alone tones show approximately similar sound pressure levels near the rotor plane. It is demonstrated that indeed it is possible to influence CROR noise emission from interaction tones with TEB. However, the considered CROR geometry decreases the noise reduction potential due to the aforementioned small aft rotor cropping. New simulations are underway, addressing the current shortcomings of the CROR geometry (aft rotor cropping) and practical applicability (massflow reduction of TEB).