A parametric study of installed counter rotating open rotors

This paper reports on the results of a series of aeroacoustic measurements of a counter rotating open rotor (CROR) installed on a 1/7 scale model of an advanced regional aircraft design. The tests were conducted in a large low speed wind tunnel for a wide range of aircraft configurations. The paper reports the results for the aircraft model in a pusher configuration at take off settings. In total there were 16 aircraft configurations tested consisting of 9 pusher and 7 tractor configurations in both take off and approach settings. The aircraft model consisted of a modular design featuring interchangeable tail pieces, variable fuselage length, engine pylon rotation and elongation and was controllable for angle of attack. Far field measurements were acquired for each configuration using three beamforming microphone arrays and a linear far field microphone array centered on the front blade plane. Near field measurements were made using a traversing arm on 7 planes centered on the front blade plane. This paper will present the results of a parametric study of the CROR noise emission including far field noise maps, CROR source spectra and directivity and the influence of the model geometry on interaction tones. The results reported here are limited to three model configurations designed to investigate the influence of the model tail on far field noise levels. This work has been conducted as part of the European Clean Sky funded WENEMOR project which will be completed in August 2013, the testing phase of which was completed in May 2013.