Cruise flight simulation of distributed propulsion and wingtip-mounted propeller aircraft and their validation with in-flight measurement data

Abstract

The utilization of aerodynamic interactions between propellers and wings through distributed propulsion (DP) and wing tip mounted propellers (WTP) offers a range of advantages for electrically powered aircraft, from improved high-lift behavior to increased aerodynamic efficiency in cruise flight. In the LuFo project VELAN, a DP configuration of the unmanned scaled flight demonstrator e-Genius-Mod is currently being investigated, following the evaluation of a pure WTP variant in the LuFo project ELFLEAN. For both concepts, a numerical analysis with the Reynolds-Averaged Navier-Stokes (RANS)-based flow solver TAU is discussed in this paper and the influence of various parameters is addressed, such as the flight speed and the thrust ratio of the propellers. To ensure a reliable prediction of the cruise flight condition and the aerodynamic effects in the numerical simulations, the CFD methods are validated with experimental data from wind tunnels and in-flight tests. The cruise flight condition in the simulation is achieved by an algorithm for adjusting the propeller thrust to the aircraft drag, resulting in qualitatively and quantitatively accurate results. Both concepts improve the aerodynamic efficiency in cruise flight, which improves as the ratio of WTP thrust to the total thrust increases. In relation to each isolated wing, over 6%increased aerodynamic efficiency can be achieved with the WTP configuration and almost 5%with the DP concept. In absolute values, the optimal WTP aircraft achieves an aerodynamic efficiency of 21.5, which is 3%higher than with the most efficient DP configuration.