Analysis of a CROR Propulsion System at High Angle of Attack and at Low Speed Flight Conditions

Kurzfassung

In the present investigation, Computational Fluid Dynamics (CFD) simulations of semi-installed Contra-Rotating Open Rotor (CROR) propulsion systems are performed. The studied CROR geometry was developed by Rolls-Royce and consists of a wind tunnel scaled 12x9 CROR with different rotor diameters and unequal rotational speeds. The numerical simulations are performed at low speed flight conditions for two angles of attack at 0°and 10°. The results are compared with WTT data toassess the accuracy of the unsteady Reynolds Averaged Navier-Stokes (uRANS) and the steady (Actuator Disk model) approaches for the simulation of rotatory systems implemented in the DLR-Tau code. The results show a good agreement of the predicted performance numbers of the propeller, but some deviations probably due to blade deformation are still observed especially on the front rotor performance. The wake measurements downstream of the rotor planes show a very good agreement between CFD and WTT and are in line with the predicted rotor performance. Important conclusions are extracted for the case at angle of attack 10° such as the effect of the front blade tip vortex impingement on the aft propeller which is relevant for the acoustics and vibration analysis during the blade design process.