Single-aisle Transport Research Articles

Comparison of Overwing and Underwing Nacelle Aeropropulsion Optimization for Subsonic Transport Aircraft

This research compares a forward-mounted overwing nacelle configuration to a conventional underwing nacelle for a single-aisle transport aircraft. We focus on characterizing the impact of the overwing placement on cruise fuel burn. To this end, we optimize both configurations under similar constraints and design processes. We use coupled computational fluid dynamics and propulsion cycle analysis with Gaussian process-based adaptive sampling in a multistage design process. The particular overwing design has a 4% higher fuel flow than the underwing design at cruise conditions. However, a postoptimization nacelle placement study illustrates that this fuel burn difference can drop to 2–3% if the overwing nacelle is moved farther forward in our design space without accounting for any resulting structural weight changes.

Environmental life cycle assessment and operating cost analysis of a conceptual battery hybrid-electric transport aircraft

Noise and greenhouse gas emission targets set by e.g., the EU commission, NASA, and ICAO oblige the aviation industry to reduce its environmental footprint. Battery-powered hybrid-electric aircraft are currently being investigated in this regard as they can potentially reduce in-flight greenhouse gas emissions and noise. However, most studies to date have focused on the CO2 emission reduction potential instead of considering the total life cycle environmental impact. Hence, within this study an environmental life cycle assessment method for a hybrid-electric aircraft is developed and applied, supplemented by a direct operating costs analysis. This allows the simultaneous evaluation of the environmental impact reduction potential and the economic consequences for aircraft operators. This demonstrates the faced trade-off and contributes to a meaningful review process. A single-aisle transport aircraft (A320 class) serves as a use case for the established methodology. It consists of the conceptual aircraft design, the environmental life cycle assessment, and the direct operating costs analysis for a conventional reference aircraft and a hybrid-electric aircraft with a discrete parallel powertrain architecture. It should be noticed that the focus of this study is the comparison of conceptual aircraft designs of the same fidelity on system level, in lieu of the detailed modeling of a hybrid-electric aircraft. Results show that for a degree of hybridization of 0.3, the environmental impact of the hybrid-electric configuration increased by 15.1%, while the operating costs increased by 41.0% compared to a conventional reference aircraft. For a future scenario, favourable for hybrid-electric aircraft with i.a. renewable electricity production, the environmental impact could be reduced by 7.0% compared to the reference aircraft. At the same time, the operating costs gap between both configurations decreases to + 26.8%. Hybrid-electric aircraft should therefore be investigated further as a potential solution to reduce the environmental impact of aviation, if simultaneously to developing them the expansion of renewable energies is fostered. Nevertheless, this reduction in environmental impact involves a high direct operating costs penalty.

Aerodynamic Aspects of Unmanned Aerial Vehicle Aerial Refueling

The feasibility of refueling a high-endurance unmanned aerial vehicle was investigated numerically, focusing on the aerodynamic effects. For this study, a single-aisle transport aircraft-based tanker was proposed (the Airbus A320) and, for the much smaller unmanned aerial vehicle, the MQ-9 Reaper was selected (and the weight ratio between these two airplanes was less than 6%). This refueling scenario was different from most previous studies where the tanker and the refueling airplanes were of similar weight. Computed results showed that the aerodynamic coefficients changed significantly with lateral and vertical separation between the two airplanes, and they changed only marginally when changing the following distance. In spite of the size and performance differences, it was found that, when the refueling plane approached from reasonably below and behind the tanker airplane, the induced rolling moments were within the unmanned aerial vehicle aileron control limit and a refueling maneuver was possible.

Multi-Objective Optimization of a Turbofan for an Advanced, Single-Aisle Transport

Considerable interest surrounds the design of the next generation of single-aisle commercial transports in the Boeing 737 and Airbus A320 class. Aircraft designers will depend on advanced, next-generation turbofan engines to power these airplanes. The focus of this study is to apply single- and multi-objective optimization algorithms to the conceptual design of ultrahigh bypass turbofan engines for this class of aircraft, using NASA s Subsonic Fixed Wing Project metrics as multidisciplinary objectives for optimization. The independent design variables investigated include three continuous variables: sea level static thrust, wing reference area, and aerodynamic design point fan pressure ratio, and four discrete variables: overall pressure ratio, fan drive system architecture (i.e., direct- or gear-driven), bypass nozzle architecture (i.e., fixed- or variable geometry), and the high- and low-pressure compressor work split. Ramp weight, fuel burn, noise, and emissions are the parameters treated as dependent objective functions. These optimized solutions provide insight to the ultrahigh bypass engine design process and provide information to NASA program management to help guide its technology development efforts.