Numerical study on lift augmentation via distributed propulsion for a propeller-driven regional transport aircraft in landing configuration

Kurzfassung

Increased high-lift capabilities due to propeller effects is seen to be one of the main benefits of distributed propulsion, as it may lead to a reduction in the main wing size and thus to reduced drag in cruise flight and/or reduced system weight and complexity. Within the framework of the European IMOTHEP project, a comprehensive numerical investigation of the lift augmentation potential of distributed propulsion has been performed based on a propeller-driven regional transport aircraft concept. After carrying out a high-lift design, the lift augmentation capabilities under take-off conditions were first assessed. The present study now focuses on the behavior under landing conditions. While the design demonstrates substantial maximum lift increases due to slipstream deflection in take-off, the lower thrust demand during landing makes the latter case more challenging. To assess the lift augmentation potential, a sensitivity study on the number of propellers, thrust demand assumptions, and thrust split with regards to the maximum lift coefficient has been performed by computing numerous angle of attack sweeps with a RANS approach. The propeller effects were thereby modeled with actuator disk boundary conditions based on the blade element momentum theory. The study indicates that even under landing conditions noteworthy lift gains may be achievable under certain conditions. In contrast to previous results for take-off, a lower number of propellers appears to be more beneficial with regard to maximum lift gains if the thrust is homogeneously applied. Lift augmentation can further be increased by re-distributing the thrust among the propellers leading to maximum effective lift gains of more than 20%. With highly distributed propulsion and homogeneous thrust distribution the maximum lift gain is however negligible.