Synthesis of Aero-Propulsive Interaction Studies Applied to Conceptual Hybrid-Electric Aircraft Design

Abstract

This paper presents a synthesis of aero-propulsive interaction studies performed at Delft University of Technology, applied to conceptual aircraft designs with distributed hybrid-electric propulsion (DHEP). The studied aero-propulsive interactions include tip-mounted propulsion, wing leading-edge distributed propulsion and boundary-layer ingestion, combined with different primary propulsion-system arrangements. This paper starts with a description of the applied design framework and an overview of the aero-propulsive interactions. Subsequently, the different aircraft configurations are sized for a set of top-level requirements covering the range between regional turboprop to typical narrow-body turbofan aircraft. Results indicate that lower shaft power ratios show better performance, with the unoptimized DHEP concepts showing values of maximum takeoff mass (MTOM) and payload-range energy efficiency (PREE) comparable to their reference aircraft. It was shown that beyond 20% shaft power ratio, the PREE decreases and MTOM increases much more than between 10% and 20%, indicating a possible local optimum between these values since even lower values did not yield any significant improvements. The benefits of tip-mounted propulsion are found to be constrained by the propeller blade tip Mach number in this particular analysis for the selected reference blade loading distribution. At the high range case for Mach 0.5, it can be seen that the distributed propulsion systems show the largest improvement.

Aero-Propulsive Efficiency Requirements for Turboelectric Transport Aircraft

“…Firstly, because the long-term environmental impact of aviation cannot be reduced effectively without significant improvements in the aerodynamic and propulsive efficiency of the aircraft. And secondly because, even though several turboelectric aircraft design studies have been performed [13,18,30,31], there is still a large uncertainty regarding the benefits of such aircraft, especially due to the lack of propulsion-airframe integration studies. While the aerodynamic benefits of novel propulsion-system layouts such as leading-edge distributed propulsion [32], over-the-wing propulsion [33], under-the-wing propulsion [13], boundary-layer ingestion [34], or tip-mounted propulsion [35] have been studied at subsystem level, it is still unclear which of these configurations leads to the greatest benefit at aircraft level.…”

A Comparison of Hybrid-Electric Aircraft Sizing Methods

“…The sizing process is documented in Ref. [28], and has been used in several configuration studies [29][30][31] and sensitivity studies [32,33] of hybrid-electric transport aircraft. Analogously to the approach of FH Aachen, the sizing method combines a point-performance analysis with a mission analysis and subsequent mass estimation, again using power-loading diagrams to represent the design space.…”

A Review of Concepts, Benefits, and Challenges for Future Electrical Propulsion-Based Aircraft

“…The propulsors can be spread in multiple fashions, such as in the leading edge of the wing [56,57], over-the-wing [58][59][60], under-the-wing [59,61], on the wing-tip [57,62], and on the fuselage-aft [26,53,63] to realize aero-propulsive synergistic integration benefits. Such benefits can be materialized in multiple ways: a lower size wing, better cruise performance, a shorter take-off and landing length etc.…”

“…Thrust-lift-drag decomposition was modified considering the impact from multiple thrust producing source on the wing and from the hybrid electric architecture. The proposed methodology is used in several of the system and sensitivity studies [54,59,125,[144][145][146]. This is proposed for finding the optimal power schedule for a hybrid electric distributed propulsion (HEDP) system configuration but based on the low-fidelity aerodynamics tool.…”