Comparison of Aero-Propulsive Performance Predictions for Distributed Propulsion Configurations

Abstract

NASA's X-57 "Maxwell" flight demonstrator incorporates distributed electric propulsion technologies in a design that will achieve a significant reduction in energy used in cruise flight. A substantial portion of these energy savings come from beneficial aerodynamicpropulsion interaction. Previous research has shown the benefits of particular instantiations of distributed propulsion, such as the use of wingtip-mounted cruise propellers and leading edge high-lift propellers. However, these benefits have not been reduced to a generalized design or analysis approach suitable for large-scale design exploration. This paper discusses the rapid, "design-order" toolchains developed to investigate the large, complex tradespace of candidate geometries for the X-57. Due to the lack of an appropriate, rigorous set of validation data, the results of these tools were compared to three different computational flow solvers for selected wing and propulsion geometries. The comparisons were conducted using a common input geometry, but otherwise different input grids and, when appropriate, different flow assumptions to bound the comparisons. The results of these studies showed that the X-57 distributed propulsion wing should be able to meet the as-designed performance in cruise flight, while also meeting or exceeding targets for high-lift generation in low-speed flight.

Comparison of High-Fidelity Computational Tools for Wing Design of a Distributed Electric Propulsion Aircraft

“…This performance should be achieved with the increased propulsion system efficiency of the electric motor/battery system. The sizing design study of the wing presented in Reference 1 resulted in a wing design with a wing loading of 45 lb/ft 2 , a wing area of 66.67 ft 2 , an aspect ratio of 15, and a cruise " = 0.75. The higher aspect ratio for the new wing is meant to minimize induced drag at cruise, since the new wing's cruise lift coefficient is much higher than the original P2006T.…”

“…The higher aspect ratio for the new wing is meant to minimize induced drag at cruise, since the new wing's cruise lift coefficient is much higher than the original P2006T. The original P2006T has a wing loading of 16.365 lb/ft 2 , a wing area of 158.88 ft 2 , an aspect ratio of 8.8, and a cruise " = 0.275. The specially designed X-57 airfoil is tailored for a cruise lift coefficient of 0.85 and incorporates a 25% chord flap.…”

Large-scale multidisciplinary optimization of an electric aircraft for on-demand mobility

“…Camber is added to the VLM mesh to obtain the expected lift coefficient at zero angle of attack. This is determined based on 2-D lift coefficient of the NASA GA(W)-2 airfoil at 2 • angle of incidence as predicted by XFOIL, which is 0.74, and the value predicted using CFD in the literature [29], which is roughly 0.8. Based on the 2-D drag coefficient data from XFOIL, we use a constant parasitic wing drag estimate of C Dp = 0.01.…”

Modeling Multirotor Aerodynamic Interactions Through the Vortex Particle Method

“…The use of multiple rotors operating in close proximity introduces complicated aerodynamic interactions that are not well understood, are not captured through conventional design tools, and need to be addressed in the conceptual design stage. [12][13][14] For instance, Yoon et al 15 investigated the effects of separation distance between rotors on a quad tilt-rotor aircraft in hover, discovering a myriad of beneficial and counterproductive interactions between rotors and airframe. Using an unsteady detached-eddy Reynolds-average Navier-Stokes (RANS) solver, they simulated the rotors operating at a high Reynolds number with and without the aircraft body.…”