NASA’s SUSAN Electrofan Aircraft: Designing the Future of Green Aviation

Overview

With the ever-growing concern for the environment, a multidisciplinary team of researchers from NASA’s Ames, Glenn, Langley, and Armstrong Flight Research Centers are investigating the design and performance of a revolutionary hybrid-electric transport aircraft called the SUbsonic Single Aft eNgine (SUSAN) Electrofan, which shows great potential to reduce aviation energy consumption and emissions. This aircraft concept, developed within the the agency’s Convergent Aeronautics Solutions (CAS) project, reduces the number of gas turbofan engines on a conventional single-aisle aircraft from two to one, and leverages distributed electric propulsion (DEP), boundary layer ingestion (BLI), and natural laminar flow (NLF), among other advanced technologies, to achieve an overall reduction in weight, drag, and fuel burn.

These advantages are partly enabled by a hybrid-electric propulsion system powered by a hydrocarbon fuel-consuming tail cone thruster (TCT), which provides 35% of the propulsive force, while also generating electric power via a set of generators to drive wing-mounted electric propulsors responsible for the remaining 65%.

Computational fluid dynamics (CFD) analyses play a critical role in maturing many of the advanced technologies being considered for the SUSAN Electrofan, involving complex multidisciplinary tradeoffs between aerodynamics and propulsion. Accurate simulations of the flow field are required to properly assess the design and potential benefits of these technologies, thereby contributing to a better understanding of the overall vehicle performance.

Project Details

The SUSAN Electrofan can assume a wide range of wing-mounted electric propulsion system configurations. This vast design trade space is being investigated by researchers in the NASA Advanced Supercomputing (NAS) Division at Ames. To accurately assess the potential benefits of DEP and BLI individually, three configurations are considered: Configuration 1 uses two underwing podded propulsors; Configuration 2 features a pylon-mounted DEP system consisting of 16 electric ducted fans in a mail-slot nacelle; and Configuration 3 mounts the mail-slot nacelle DEP system directly onto the lower side of the wing to leverage BLI. Baseline models are developed for each configuration, and successively refined to improve concept performance. The end product is a credible estimate of the relative benefit offered by each configuration.

In parallel, this research also focuses on investigating the aero-propulsive performance of the TCT, which is designed to benefit from BLI. CFD analyses contribute to a comprehensive characterization of the flow ingested by the engine, thereby informing design choices and providing insight into the advantages and design challenges of BLI. One design challenge actively being studied includes inlet flow distortion intensity, which can be addressed through careful reshaping of the fuselage diffuser.

All CFD analyses are performed with the Launch, Ascent, and Vehicle Aerodynamics (LAVA) flow solver developed within the NAS Division’s Computational Aerosciences Branch. The LAVA flow solver considers the compressible, steady Reynolds-Averaged Navier-Stokes (RANS) equations and utilizes an actuator zone model to simulate the propulsive effects of each thrust-producing element.

Results and Impact

By accounting for the interactions between aerodynamics and propulsion, these investigations contribute to further understanding the design and integration of advanced propulsion technologies into next-generation commercial aircraft. These technologies have the potential to significantly reduce aviation energy consumption and emissions—key elements in the future of aviation as the industry pushes for greener aircraft solutions. The relative benefits of DEP and BLI are also quantified on an aircraft systems level, providing valuable insight into the benefits that each technology can provide.

Why HPC Matters

Supercomputing resources available at the NAS facility are paramount for studying these novel propulsion concepts. These resources enable fast and efficient simulation turnaround times that accelerate the exploration of the vast aerodynamic and propulsion trade space, while facilitating a rapid exchange of designs and analyses between the various disciplinary teams for a seamless collaborative effort. All simulations were performed on the Pleiades supercomputer, using up to 800 Broadwell cores per simulation.

What's Next

Design of the SUSAN Electrofan continues, with emphasis on applying high-fidelity aerodynamic shape optimization to improve the aero-propulsive performance of each aircraft component. Future work also includes the generation of an aerodynamic database to support aircraft systems analysis, stability and control, and other efforts. Furthermore, researchers will continue close collaborations on the internal flow path and blade geometry design for each propulsion unit, refinement of the main engine design cycle, structural sizing and analysis, NLF wing technology, and development of scaled-model prototypes for flight testing and for exploring control and stability augmentation strategies.

Researchers

• Leonardo Machado, NASA Ames Research Center
  
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• Jared Duensing, NASA Ames Research Center
  
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• Timothy Chau, NASA Ames Research Center
  
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• Cetin Kiris, NASA Ames Research Center (POC)
  
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