Numerical Parameter Study of a Strake on a Turboprop Engine in Active High-Lift Configuration

Kurzfassung

The engine integration into the wing of an aircraft often has a significant impact on lift generation in high-lift configuration. Within this project, the SFB 880 aircraft, equipped with a droop nose and an active Coanda flap is analysed in the landing configuration. The integration of large turboprop engines leads to strong nacelle vortices that cause a wake burst above the flap inboard of the engine and therefore reduces C_{L,max} recognisably. Therefore, a nacelle strake parameter study is performed, based on an initial strake. The strake optimisation allows for a lift recovery of C_{L,max} by around 17 LC and an increase of Alpha_{max} by 2° compared to the configuration without strake. Since nacelle strakes have not been extensively investigated for aircraft with turboprop engines and an active high-lift system, particular attention is paid to the effects of the parameter variations and to the nature of the improvements. It turns out that the lift recovery arises from an effective weakening of the nacelle vortex. This is particularly achieved thanks to a smaller distance between the nacelle and the strake vortex compared to the case with the initial strake. Thereby, the strake vortex shows a very good interaction with the nacelle vortex while its impact on the flow close to the surface is kept low. Hence, a final enlargement of the strake area also allows for an increase of lift. In addition, further potential for an augmentation of C_{L,max} by the utilisation of a supplementary outboard strake is revealed. Finally, the impact of the strake integration on drag in cruise configuration is analysed. Hereby, a drag increase at the beginning of cruise of 0.222% is determined.